via ad astra - international space elevator...

Via Ad Astra

The Space Elevator Magazine

Volume 1 / Number 1

www.isec.org

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ACKNOWLEDGEMENTS Via Ad Astra – The Space Elevator Magazine

Official Publication of the International Space Elevator Consortium (ISEC) http://www.isec.org

Editor-in-Chief Ted Semon President Emeritus, ISEC

ISEC Officers & Directors Officers:

President: Peter Swan Vice President: Robert “Skip” Penny Secretary : Martin Lades Treasurer: Ted Semon

Directors:

David Horn John Knapman, PhD Martin Lades, PhD Bryan Laubscher, PhD Robert “Skip” Penny Stephanie Ratko Peter Swan, PhD Dennis Wright, PhD

Via Ad Astra (Print version ISBN 978-1-329-64123-5, eVersion ISBN 978-09854262-7-9) is published by the International Space Elevator Consortium (ISEC), 16991 McGill Road, Saratoga, CA, 95070-9602, USA. Please direct all enquiries to [email protected].

Editorial Communications should be sent to the International Space Elevator Consortium, 16991 McGill Road, Saratoga, CA, 95070-9602, USA or emailed to [email protected].

Subscription Rates: The Print version of Via Ad Astra is offered free, to all ISEC Members in good standing with membership level Professional or above. The electronic version of Via Ad Astra is offered free to all ISEC Members in good standing. Individual copies may be purchased from the ISEC store (located on the ISEC website; http://www.isec.org). For questions or more information, please email us at [email protected].

MISSION: Our Mission statement reads “ISEC promotes the development, construction and operation of a space elevator as a revolutionary and efficient way to space for all humanity.” ISEC works towards this goal by publicizing and promoting the concept, promoting and encouraging research in technologies necessary to build a space elevator and promoting and encouraging research into all aspects of space elevator technology.

Copyright © 2015 by the International Space Elevator Consortium. All rights reserved. No part of this work may be reproduced or translated in any way without permission from the copyright owner. Permission to reproduce all or part of this publication in any form must be obtained in writing from the President of ISEC. Requests for reprints should be sent to [email protected].

Disclaimer: The ideas and opinions expressed in Via Ad Astra do not necessarily reflect those of ISEC or the Editors of Via Ad Astra unless so stated.

Print version published by lulu.com.

eBook published by The International Space Elevator Consortium.

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CONTENTS INTRODUCTION

Acknowledgements iii

Contents v

Foreword vii

Preface ix

ARTICLES

Conversations with Yuri Artsutanov Artsutanov, Schlusser, Sherman

1

Early Space Elevator History – Tsiolkovsky, Artsutanov and Pearson

Martin 13

International Law and the Construction and Operation of a Tethered Space Elevator

Kirchner 29

Space Elevator Dynamic Response to In-Transit Climbers Lang

46

The Space Elevator in the Earth’s Atmosphere Knapman 76

The ISEC History – Interview with Vern Hall Hall, Dodrill 92

Space Elevator Simulation: Validation and Metrology Robinson

99

Anchored Lunar Satellites for Cislunar Transportation and Communication

Pearson 110

A brief history of the Space Elevator Games Semon 139

Yearly Study Reports from the International Space Elevator Consortium

Swan 153

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FOREWORD Welcome to another step towards space elevators. ISEC has expanded its reach with a new publication titled Via Ad Astra – “Road to the Stars.” This new publication will help us record the history and progress of the space elevator and present projects and processes as we go forward to the stars. Our technical journal, CLIMB, has concentrated on peer-reviewed papers but has also included other interesting and worthy articles about the Space Elevator. These types of articles were included in CLIMB because there was no other publishing venue for them. Via Ad Astra represents that new publishing venue as ISEC believes we need a format that showcases these articles, shows our progress and presents our approach toward the future. The name was chosen to reflect our mission: to provide the Road to the Stars. This new venture will help ISEC fulfill its vision:

A world with inexpensive, safe, routine, and efficient access to space for the benefit of all mankind.

In this issue, you will find a varied and informative set of articles:

An interview with Yuri Artsutanov, the ‘father’ of the modern-day concept of the space elevator.

A review of the Space Elevator Games, the highly successful collaboration between NASA and The Spaceward Foundation.

Several technical articles about specific aspects and requirements of a space elevator.

A brief review of the ISEC Study Reports, reports created by ISEC each year targeting a specific area of research necessary to build a space elevator.

And much, much more!

Via Ad Astra will be the publication for our members and supporters around the world, and each of you is invited to contribute to future issues. We hope you enjoy the articles!

“Pete” Swan Dr. Peter Swan, President of ISEC - November, 2015

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PREFACE Welcome to the inaugural issue of Via Ad Astra – the Road to the Stars! This publication will feature articles of interest for those of you who, like me, find the idea of a space elevator fascinating or who want to learn more about this most magnificent of engineering concepts. As Dr. Peter Swan mentions in his Foreword, articles in this publication will include those which would have appeared in the ‘Additional Reading’ section of CLIMB, the Space Elevator Journal. In addition, we will be including articles which might not be appropriate in a scientific journal, but are still technical in nature. In this and future issues, you will find articles on the history of the space elevator and progress towards developing a space elevator, what life might be like with a space elevator, or, perhaps, an installment of ‘the great space elevator novel’ (whenever it is written ). We will also occasionally include reprints of important, space elevator-related articles which have not been made available to the general public before. You might also see space elevator-related artwork, reports from space elevator competitions and who knows what else. It’s going to be an eclectic mix and should be a fun read – I know I had a great time working with the various authors while pulling this issue together.

It is not an overstatement to say that a space elevator will truly revolutionize life as we know it; scalable, cheap, easy and reliable access to space will open up a wealth of opportunities and allow all of humanity (not just astronauts and rich tourists) access to this new frontier. Via Ad Astra, along with CLIMB, the yearly ISEC reports, the yearly ISEC Space Elevator Conference and all of the other projects which ISEC coordinates will help make this happen.

Comments? Suggestions? Constructive criticism? Please send them to me at [email protected].

Finally, I would be remiss if I didn’t remind you that you can find out how to help us by becoming a member of ISEC by visiting our website at http://www.isec.org.

I hope you enjoy the articles – thank you for reading!

Ted Semon Ted Semon, Editor – Via Ad Astra - November, 2015

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CONVERSATIONS WITH YURI

ARTSUTANOV Russian Engineer Yuri Artsutanov is

considered to be the original inventor of the modern-day idea of a Space Elevator. In

March 2010, while in St. Petersburg, Russia, he held a phone conversation with Eugene Schlusser and Natalie Sherman.

This conversation was in Russian but was translated into English by Mr. Schlusser

and Ms. Sherman.

PART I – “A LIFT INTO SPACE”

Q. Yura, please tell us how the idea of “A Lift into Space” came to you initially?

A. It was in 1957; I had a friend, Alik (Albert) Yezrielev; his father was a Stalin Prize winner and as such had access to foreign scientific and technical journals so Alik read them as well. One day he told me the Americans had invented a very strong material so that a cable made of this material could be as long as 400kms and would not break under its own weight. I commented that if the cable were placed vertically at an altitude of 400kms where the force of gravity is less than on earth the cable could be made even longer (for ~ 200m) without collapsing into itself. There followed this hypothetical

question: what strength would a cable of infinite length have to have? And what if such a cable where erected on the equator where its centrifugal force would keep it at the higher altitude and therefore it would not fall down? That might make it possible to travel into space along such a cable instead of using rockets!

Q. What aroused your interest in the material and the thickness of the cable in the first place?

A. I was interested in travelling into space from my early childhood. When I read that a new super strong material had been invented I immediately realized it could be used for building super long cables to lift us to cosmic altitudes, i.e. for traveling into space.

Q. So the very idea of “A Lift into Space” came to you when you thought about the cable, its strength etc.?

A. Yes and it was in 1957, two months before the first Sputnik was launched.

Q. Why is it so important to travel into Space?

A. To find fossil fuels and water on other planets and to use them.

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Q. What about “saving humankind”?

A. Plenty of writers and philosophers from Aristotle to the present have thought and written about this. K.E.Tsiolkovsky said that “The Earth is the cradle of humanity but mankind cannot stay in the cradle forever”. The idea of Arthur C. Clarke was “to resettle humankind around the sun to increase its possibilities of survival”. Besides, sooner or later the sun will perhaps explode and people will need transport to escape and to disperse into space. So “salvaging humankind” has two meanings: the salvation of humankind in the event of a catastrophe, and making way for humankind in its natural aspiration to expand. Now it is closer to being realized thanks to the invention of the new super strong material – fullerene. The Americans could be using “A Lift into Space” by 2040.

Q. Tell us how your idea came to be connected with Tsiolkovsky?

A. Five years after my article “A Lift into Space” was published in the newspaper Komsomolskaya Pravda a short article mentioning it appeared in the newspaper Leningradskaya Pravda. A year later the Americans invented the same “lift” (they called it a “space elevator”) and published an article in the American

magazine Science. A correspondent of the Novosti Press Agency V. Lvov had special access to the foreign press and brought the article to Leningradskaya Pravda where he was told that the idea was not a new one. A Russian article on the same idea had already been published in their paper one year prior. They searched their archives and found the article. Lvov then came to me convinced that the Americans had stolen my idea and he even published an article accusing the Americans. That was in 1966 when “the cold war” was coming to an end. When the Americans found out about Lvov’s article they asked him to stop alleging plagiarism because he was wrong. Their invention had been made quite independently. Lvov agreed and in an article for the American journal Science wrote the space elevator had been “invented for the second time”.

Then the KGB came into the picture asserting that I was not worthy of the status of “a hero”. My father had been arrested as “an enemy of the people” and I myself hadn’t informed them about a group of young dissidents (i.e.“enemies of the Soviet State”) at the Leningrad Technological Institute where I had studied. I had known them and was even acquainted with them. Lvov was ordered as


follows: “You need to reduce the role of Artsutanov in this invention; write that the idea originated with Tsiolkovsky and Zander, and Artsutanov had copied their idea; that is, he wasn’t the originator of the idea”.

In fact what Tsiolkovsky had written was: “If it were possible to build a tower to a height of 36, 000 kms it might be possible to launch satellites from the top. However, everybody understands that to build such a tower is impossible”. He didn’t even offer a solution on how to build such a tower. It was a purely mental speculation on his part, “a mental experiment” as Arthur C. Clarke put it later.

Among the rough notes belonging to F. Zander they found his calculations for the strength of a tube which could be used by people to get to the moon. He concluded that the entire supply of cast iron on the planet would not be enough to build such a tube. He also wrote that while it might be conceivable “everyone understands that it would be impossible”, and thereafter he never mentioned it again.

Despite all these obvious facts V. Lvov still claimed that both scientists had been thinking of “a Lift into Space” long before me.

It must be said that Tsiolkovsky’s idea for a tower was not original.

It goes back to the Biblical Tower of Babel. People wanted to build a tower to reach the sky but God punished them and destroyed the tower.

Arthur C. Clarke wrote to V. Lvov pointing out that there are no references to a lift in the works of Tsiolkovsky. The idea of a tower remained merely a speculative matter.

Q. What did Arthur C. Clarke think about it all when he found out you were the real father of the idea?

A. In his novel The Fountains of Paradise he clearly wrote that the lift into space was invented in the 20th century by Yuri Artsutanov and Tsiolkovsky didn’t invent any of it. Tsiolkovsky’s writings about the tower are no more than a mere “mental experiment”.

Q. How did you meet Arthur C. Clarke?

A. He came to the USSR with several purposes in mind; one was to meet me. His main goal was to see the Hermitage in St Petersburg and the location in Siberia where the Tunguska meteor fell in 1908 (he wasn’t able to fulfil this aim). His trip was organized by the newspaper Komsomolskaya Pravda who gave him an interpreter as well.


Yes, he came to my apartment, looked out from my window, we spoke sitting around the table …

Q. What do you think about John Isaacs and his work?

A. His is engineering work of a very high quality but the idea itself is exactly the same as mine. He had the opportunity to try to build a lift – the company, the equipment etc. which I, of course, didn’t have. The idea itself came to him through his work as an oceanographer. In their research into the oceans it was very important to have very strong cables which wouldn’t break even at a depth of 30km. Then he realized it would be possible to pull the cable not only down underwater but up as well.

Q. Do you have other inventions on which you have written and published?

A. Dyson’s Sphere. In our search for other civilizations we need to locate and study huge objects of a length of up to one billion km. Their temperature has to be less than 50C for life to exist. In the future the increasing population on earth will need all the energy of the sun, not just that fraction which at present reaches our planet. So we need to create a sphere, where intelligent creatures can live on its inner surface and capture all of their

energy’s source – the sun’s or other sources. That’s Dyson’s idea.

Q. What is your part in the idea?

A. Nobody knows how to construct a sphere so that it isn’t destroyed by the sun’s gravitation. My article on the subject was published in the Russian magazine Knowledge is Power, 1969, No.9.”


PART II - DYSON SPHERE

Q. What is a Dyson Sphere?

A. Dyson is an American scientist-physicist. He proposed that if we want to survive in the Universe we need to search for much bigger sources of energy than the sun, the size of the entire solar system and the absolute temperature of radiation up to 300 degrees K, the temperature needed to support life. He said that life of any civilization develops and expands requiring more and more space. In the end, the entire terrestrial civilization will occupy a “cocoon” – so called “Dyson’s Cocoon” which will include some of the planets of our solar system, satellites, any artificial bodies (Sputniks) etc. All this matter will form a sphere around the sun capturing its entire energy for use by humankind. At present only a millionth part reaches our planet. So the sphere has to be of an enormous size but its temperature has to be equal to that of the human body.

Nobody knows how to construct such a cocoon. The (Polish) writer and philosopher Stanislav Lem wrote that it was impossible. Mathematics and mechanics also indicate such a sphere is impossible to create, that it is fundamentally unstable, that it will be crushed by the forces of gravity.

So this is my proposal: to make a belt in the shape of a beautiful shell revolving around the sun like a stretched satellite. If such a belt were constructed we could get not just a millionth part of the sun’s energy but as much as one hundredth of it. However, the radiation will be immense so a second belt has to be constructed at an angel to the first, and a third belt – at the same angle as the second one. The second belt must have a lesser diameter than the first one and the third belt a lesser diameter than the second to prevent them from crashing into each other. Such a shell will be impossible to crush. It will be stable because in each section the centrifugal force will be balanced by the force of gravity. The sphere will rotate around the sun and in addition it might even be possible to move closer to the sun. However that is a very complicated option.

So in principle it is possible to devise a mechanical structure which will not be crushed under its own weight and I’m the first one to propose this. My article “Threefold Matryoshka” was published in the Russian magazine Energy. 1986, No.12. There is even a drawing of how it will look. I sent the article to Freeman Dyson, but unfortunately I couldn’t meet him


when I was in the USA about 10 years ago.

PART III - WHAT YURI ARTSUTANOV TOLD US ABOUT HIMSELF

Q. When and where were you born?

A.I was born on the 5th of October, 1929 in Leningrad, on the Moika River, in the building which once belonged to the Governor-General of St. Petersburg in the XVIIIth century, during the time when either Casanova or Cagliostro visited the city.

Q. Who were your parents?

A. My mother was a teacher of history and worked in both standard and technical schools. My father was also a teacher of history but taught in special schools for workers which were organized after the revolution to educate the working classes. They met at the A. Herzen Education Institute where they studied together.

My maternal great-grandfather, my mother’s grandfather, was Ivan Vassil’evich Vassil’ev (after whom a street in old St Petersburg was named, now called Degtyaryov’s street). He was the son of a serf who came to St. Petersburg from Tver province to sell canvases. Artists recognized

his talent and began to teach him their trade. He became an artist and produced many paintings. Later he even became an Honorary Citizen, the title passed on to the next generations as Hereditary Honorary Citizen and my mother had this title as well. He opened a lane on the Okhta (a district in St. Petersburg on the other side of the Big Neva River) near the Okhta cemetery. This lane grew and was renamed Vassil’ev street as I mentioned before.

In 1935, when I was 5 years old my father was arrested in connection with Trotsky’s trial and he was exiled to Kazakhstan. During the first couple of summers he came illegally from there to the dacha we rented near Leningrad. In 1937 he was finally sentenced to five years as ‘an enemy of the people’, and taken to a concentration camp in Magadan, on the Kolyma.

After that, he was stripped of his civil rights for a further 15 years, exactly like Ivan Denisovich, the hero in Solzhenitsyn’s famous novel. After five years, in 1942 he was released but denied the right to live in a big city. He lived in a village called Nexican, in Magadan district until 1957. After Stalin’s death and with Khrushchev in power he was rehabilitated. Then he moved to Krasnoyarsk where he lived until his death in 1973. I have a


document confirming that I’m the son of the victim of unlawful repression and as such I receive an additional pension – 300 rubles (about $10!) a month.

My mother died in 1978. I had a brother who died 5 years ago. He was a graduate of the Air Force Academy as a meteorologist. After his death his wife appropriated my flat by deceit and left me to live in a tiny flat where I can’t order all my belongings properly. I think my original flat should become a museum just like the Tsiolkovsky museum.

Q. Where were you educated? What do you remember about your school?

A. I was educated in school No.14 (which later became No.78) on the Petrogradskaya Side. That was before the war and it was a standard school and my class was a standard one as well. There were some boys who were friends interested in science and we discussed all sorts of unusual scientific problems. I finished year 7 only.

Q. What do you remember about the war?

A. The war started in June 1941 but only in March of 1942 were my mother, brother and I able to

escape the blockaded city across the frozen Lake Ladoga along the so called “Road of Life”. We were lucky to survive as the truck in front of us sank under the ice. We spent the rest of the war in the Urals – in the village of Beloyarka in what was Chelyabinsk province at that time but later became Kurgan province. There was a very nice river in Beloyarka and the village itself has some connection to Tsar Boris Godunov.

Q. Where did you study and work after the war?

A. We returned to Leningrad in July 1945. After 7th grade at the standard school I began studies at the technical school from 1945 to 1949 and in that year I entered the Lensoviet Leningrad Institute of Chemical Technology. After graduation in 1954, I was sent to The Research Institute for the Chemistry of Mineral Oil (I stayed there for 3 years) and worked on polymers. In 1957 I entered the special course at the same Chemical Institute. I studied to do my PhD in the faculty of colloid chemistry.

Unfortunately I didn’t complete my PhD. I wrote my thesis but didn’t submit it because I became very skeptical of the details of “Kremnyov’s Method” (he was the head of the Faculty) when I found them to be incorrect – this way of doing


things made it possible to achieve any results you wished.

Q. Was it at that time that the idea of a lift into space came to you? How?

A. Yes, my idea for a lift into space took shape at that time. I was always interested in space and my friend Alik Yezrielev’s father, as a Stalin Prize winner had access to foreign scientific and technical journals (that was in 1957, four years after Stalin’s death) and we could also read them. On one occasion we read about a newly developed extremely strong polymer, so strong that if you used it to make a rope 400km in length it would not break under its own weight. At an altitude of 400km the force of gravity is significantly less than on earth so the rope could be lengthened up to 1km (according to my calculations) without it breaking. The question arose what thickness would a rope of infinite length require. It turned out to be impossible if it was of a constant diameter. However, such a rope could be possible if it had a variable cross section, that is, was spindle shaped and if it was possible to use centrifugal force to counter the force of gravity. Step by step the idea of a lift into space was born. I kept talking to people about the idea but didn’t submit

my article to the Soviet newspaper Komsomolskaya Pravda until 1960 and a week later they published it.

Q. Where does your ability to have ideas in so many different areas come from? Is it innate or did you develop the skills yourself or were they the result of your studies and work?

A. It is difficult for me to answer that question. As a child I read popular science books in the series “Entertaining Physics”, “Chemistry, “Mathematics”, “Astronomy”, “Mechanics” and so on, all by the same author Perlman. Perhaps both my interest and my ability came from there.

Q. If you were interested in such books and you read them it suggests you already had an interest in these things. The ability to think, to analyze, to develop new ideas could develop from your reading because all those books were about ideas and how to put them into practice.

A. I was always solving difficult problems. For example in 4th Grade I solved all the problems in our Arithmetic text book.


Q. Was your Arithmetic teacher special?

A. No, he was an average teacher.

Q. Do you recall any outstanding teacher at your school?

A. Yes. In Grade 7 there was a teacher of Physics – Guchkov who made a big impression on me. He gave me a physics textbook to read which he had used at University.

Q. Did you understand it all?

A. Of course! (Laughs)

Q. What are your own best qualities?

A. Love for knowledge otherwise known as ‘inquisitiveness’. I love to solve difficult problems. Yes, I’ve always tried to solve difficult problems wherever I’ve been.

Q. Did you join the Komsomol (Young communists) organization?

A. Of course I did. It was compulsory! As soon as I was 14 years old, I became a member at once.

Q. What happened when you graduated from the Technological Institute? Did you let your membership lapse?

A. When I started my studies at the technical school I was asked whether I was a member of Komsomol and I said “yes”. When I started to work in the Research Institute for the Chemistry of Mineral Oil I was asked if I was a member of the Communist Party. I said ”no”. Of Komsomol? I said “yes”. When I completed the course work for my PhD in 1960 I left Komsomol because of my age. They kept asking me to become a member of the Communist Party but I avoided it at all costs. I was afraid to tell them that I didn’t want to! (Laughs).

From 1960 to 1964 I remained in the faculty of Colloid chemistry and worked in the laboratory for four years.

In 1965 my friend Alik Yezrielev persuaded me to join the Institute of Synthetic Rubber (VNIISC) because at the Chemistry for Mineral Oil Institute I had been working with latexes. It was here I first met some young dissidents.

Q. Did the fact your father was arrested affect your career, if so how?

A. Yes, it affected me before his rehabilitation in 1956. Before then


I was expelled from the special faculty of Atomic Energy in the Technological Institute where I studied. It was actually contrary to their own popular slogan “Children are not responsible for the deeds of their fathers”! (Laughs). I always had the best marks in all subjects. I was awarded a special allowance as part of my scholarship (but they didn’t give me a Stalin scholarship!) Everyone around me kept telling me I was the best student in the Institute etc. Despite this I was expelled from the Atomic Energy faculty.

Q. How did you get into the Faculty of Atomic Energy in the first place?

A. I had a “red”diploma (an outstanding diploma with Honors) from the technical school where I had studied so they enrolled me there but by doing so they kept me from any of the other, better faculties. The faculty of Atomic Energy was “closed” with increased security and secrecy so you needed to have an absolutely (politically) clean biography. From that point of view I was not “trustworthy” because my father was a political prisoner. Political considerations were more important than my qualifications in 1949. My father wasn’t rehabilitated until 1956.

Q. Were you interested in atomic energy?

A. No, but they offered other subjects in the faculty: all the nuclear processes, all the chemical processes connected with nuclear technology etc. i.e. it gave a very broad knowledge around the behavior of atoms.

Q. How did you become an “Enemy of the People”?

A. It was much later, in 1965 and I didn’t become one directly as such. There was a group of nine students who decided to organize a communist revolution. They were all arrested and imprisoned. Those who read their pamphlets and the book called “From Bureaucracy to Dictatorship of the Proletariat” and who hadn’t informed the “organs” (of the KGB) about such anti-Soviet activities were expelled. “Why didn’t you denounce them?” “Why didn’t you come to tell us?” “If you hadn’t forgotten our special department (Department No.1) at your place of work or study and if you had have come to us more often everything could be different”. So, I was dismissed from the Institute of Synthetic Rubber. I had worked there for only a year and a half.

Q. How did that affect your life?


A. It continued to affect me in one way or another. Wherever I worked I was either paid less than before or didn’t receive any wages for some months. And if they wanted to dismiss me I was told to write an application that I wanted to terminate my work “of my own free will”. Or else I was told, “Yes, we’ll appoint you” but three days later I was rejected.

That was the case in five or six work places. Finally I found a position at the VNIIASH (Institute for Abrasives and Grinding Materials) where people from the 1st Department of my previous place of employment had called asking them to take me (the Institute had a low security profile). That was in 1966. Actually it only happened after I had gone to the headquarters of the KGB in Leningrad (the so called “Big House” on the Liteinyi Prospect) and told them that I hadn’t known that I had to inform them about the dissidents. I hadn’t known I had to denounce them! I worked from 1966 to 1992 at VNIIASH. In between I worked for four years at the “Ilych” in an experimental research plant.

Q. Your future wife worked at VNIIASH?

A. Yes, she had graduated from the Electrotechnical Institute in Leningrad.

Q. How did you survive financially before you started to work at VNIIASH?

A. My mother and my aunt helped me with money but personally I wasn’t stressed because I felt it wasn’t my fault that I didn’t have a job.

Q. Why didn’t you emigrate when it became possible? You told me in 1979 when I emigrated that you couldn’t bear leaving the Russian landscape.

A. No, I was joking! I never considered emigrating seriously because I couldn’t bear to cut my connections with hundreds of my friends and acquaintances.

Q. Are you a member of some scientific organization, club, or association?

A. I was a member of a society where people delivered scientific lectures and I did the same: the Society for the Dissemination of Scientific Knowledge Unfortunately I haven’t heard about the society for a long time. I also gave lectures at the Historical Museum of the Peter and Paul Fortress.


Q. When did you retire from VNIIASH?

A. In 1992. I didn’t retire, they made me go on the pension. The Deputy Director of Science, M. Efros, told me I was too individualistic. If I had have included all the “essential people” (i.e. himself) as co-authors on the applications of my inventions I could have worked much longer!

(This interview originally appeared in the Space Elevator Blog

(http://www.spaceelevatorblog.com)

Questions about the interview and/or translation should be directed to Eugene

Schlusser

([email protected])


EARLY SPACE ELEVATOR HISTORY

- TSIOLKOVSKY, ARTSUTANOV, AND PEARSON

Nicholas Martin

Nicholas Martin Teaches English as a Second Language while volunteering within

the ISEC1.

Introduction

In reconciling human presence with outer space, the rocket remains unchallenged as the definitive icon of our link to the stars. Whether to the moon, routine trips to the ISS, or delivering of instruments into space so that they may continue into the deep reaches of our solar system, it is the rocket that gets us there. The question, however, is “Are these towering metallic colossi, which rely on equally massive expenditures of fuel to escape the relentless gravity of the planet, the only means by which we as a civilization might become active in space?” Are they truly the only systems that might grant us access to worlds beyond our own? For a number of years, many in the scientific community have believed the

answer to that question is no, and in expressing such sentiment, feel that there might be a rather extraordinary alternative.

While no one could undermine the significant contributions that rocket technology has made to aerospace, nor to civilization as a whole, there are those who criticize the method as being exceedingly inefficient, dangerous, and far too expensive. In the waning days of the space shuttle, launches were estimated to cost more than $1.5 billion each, totaling around $209 billion when the shuttle Atlantis touched down on July 21st, 2011, marking the retirement of the 30-year program. Today using launch craft more akin to those of the shuttles’ predecessors, NASA estimates that it currently costs the administration around $10,000 per pound to get into Earth’s orbit. [Note: to reach Geosynchronous Orbit or escape the Earth’s gravity, the number is at least twice that, or $ 20,000 per pound] This staggering price tag has made space travel an uneconomical venture that few have had the bankroll to finance. Many would argue it to be the most discouraging element of our extra-planetary activity. As next-gen rocket technology unfurls over the coming decades, many organizations, either government run or privately owned, hope to see a reduction in the cost of


getting to space. In doing so, many feel the onus is largely on reusability and/or the mitigation of reassembly. Or rather, putting the parts that are reusable back together in preparation for subsequent launches, such as the solid rocket boosters that were employed by the shuttles. If no reassembly were required at all, through the use of what many refer to as an SSTO (Single-Stage-To-Orbit) craft, then getting to space via rocket could see a dramatic reduction in its overhead expense.

While rockets are being retooled to better accommodate both government and corporate checkbooks alike, one still has to wonder if there exists another way; another means by which we might provide egress from the gravitational binding of planet Earth via a system that didn’t employ any form of rocketry whatsoever. A cleaner, greener alternative that would be entirely reusable, and only require a one-time assembly.

I don’t think anyone could be blamed if they felt that such a system sounded entirely impossible, or at the very least, incredibly implausible. However, a cadre of scientists and engineers, whose numbers have been growing steadily over recent decades, firmly believes there is such an option that satisfies all of the aforementioned

criteria. A completely unorthodox method whose absurdity has been increasingly diminished given its prolonged subjugation to scientific analyses. Though it would be the most monumental engineering endeavor humanity has ever known, the space elevator, as envisioned by both its creators and proponents, could theoretically provide humanity with cheap, routine, effective, daily, and clean access to space.

For those who may be unfamiliar with the concept of a space elevator, don’t worry, it is precisely as its name implies, a ground terminal on the Earth’s surface tied to a space station by an enormously long tether on which climber cars will deliver crew and cargo to space. The orbital element is located at roughly 36,000 kilometers above the equator, or geostationary orbit. As its name would suggest, anything placed in this orbit remains perfectly in step with the Earth’s rotation, maintaining a fixed position relative to a point on the planet’s surface.

Communication satellites are often found at this location as it is more convenient for ground antennas to relay information to them. Imagine then, that from a space station maintaining an exact position above the planet, a line being dropped that would eventually make contact with a


terminal on the surface, in turn providing access to space entirely rocket-free. Reaching outward from the space station, the line would also need to be extended to a distance of some 100,000 km, or more, where it would be attached to an Apex Anchor counterweight, whose purpose would be to keep the entire system taut. To put that

Figure 1, Modern Day Space Elevator2

distance into perspective, the moon is 385,000 km away, meaning that we are talking about the construction of a system that would extend to over 25% or more of the distance to Earth’s age-old lunar companion. As difficult as it is to imagine that engineering effort, advocates of the space elevator estimate that

putting payloads into GEO orbit using this method would cost a mere $100 per pound, as compared to NASA’s current figure of $20,000.

I will be the first to admit that the space elevator sounds like something straight out of a science-fiction novel, and yes, it does have tenaciously imaginative image. The idea of a monolithic bridge to the stars has been a common element in sci-fi literature, occupying significant roles in the works of authors such as Sir Arthur C. Clarke3, Kim Stanley Robinson4, and others. Despite its prominence in fictitious renderings however, the elevator has also acquired tenancy in the minds of scientists and futurists alike, and for a much longer time than most might intuitively assume.

For 120 years in fact, the space elevator has been conceptualized, invented, reinvented, published in both media outlets and science fiction, and seen an increasing amount of supporters flock to the dream of cheap, daily access to space that it proposes. Since the 1960s, it has been the subject of increased scientific scrutiny all in an effort to determine whether or not it can be made real. Today, there are a multitude of organizations based in various nations that advocate for its construction; and, since 2008,


annual conferences have been held by the International Space Elevator Consortium (ISEC) that address the prodigious amount of obstacles that impede an elevator’s progress. The past decade alone has seen a variety of books published that enumerate the engineering details relevant to the elevator’s construction and operation, estimating just how doable such an undertaking would be. The most recently published work, Space Elevators: An Assessment of the Technological Feasibility and the Way Forward5, whose editors include major players in the space elevator community, was released in December 2013. The book emphasized the finding that space elevators do in fact, seem feasible.

Long before the release of this comprehensive text however; as well as those before it, the idea of a space elevator has been reaching outwards, looking to gain traction in the minds of scientists, engineers, and enthusiasts alike. Oddly, its official invention is recognized to have occurred in two separate locations and times; first by Yuri Artsutanov in 1960 with the release of “To the Cosmos by Electric Train”6, and then by Jerome Pearson in 1975 with his piece “The Orbital Tower: A Spacecraft Launcher Using the Earth’s Rotational Energy”7. Time

and circumstances separated the two efforts by more than the 14 years, Artsutanov and Pearson have since agreed to be known as ‘co-inventors’, despite never having collaborated. The conceptual origins of this grandiose railroad to the stars however are believed to have occurred much earlier. In chronicling the elevator’s progress as an alternative to rocket powered flight, it is necessary to travel back to the imaginative foundations that begot its earliest incarnations. Through the decades that followed, one can see how the elevator became the object of extensive and systematic evaluation. In doing so, three primary individuals can be identified as playing a critical role in the propagation of the space elevator. The story begins just prior to the turn of the 19th century with a well-known Russian scientist who, even today, is celebrated as being one of the most pervasive names in the early development of space flight.

Conceptualization − Tsiolkovsky and the Celestial Castle

Together with Goddard and Oberth, Konstantin E. Tsiolkovsky is considered to be one of the fathers of rocketry. In Moscow, a statue in his likeness sits in front of


the ‘Monument to the Conquerors of Space,’ a behemoth of a space-age obelisk built in memory to the USSR’s accomplishments in exploring the final frontier. He is perhaps most famously associated with the Ideal Rocket Equation, sometimes referred to as the Tsiolkovsky Rocket Equation, which provides the formula to account for the change in a rocket’s velocity as its mass continues to reduce while expending fuel during flight. This equation, which serves to yield a rocket’s delta-v, or the total change in velocity the craft is capable of producing, is still used in determining how much fuel is required to successfully propel a rocket-based craft of any given mass into orbit or beyond.

Significant as that contribution was however, equations as they pertained to the yet invented rocket weren’t the only thing on Tsiolkovsky’s mind when it came to conceptualizing avenues by which to gain access to space. As a professor of mathematics, he was particularly fascinated by the study of gravity, finding ways to simulate it, and also, ways to defeat it. To that end, his examination of the subject provided for a multitude of hypotheses that he included in his numerous written works. Within the pages of one particular collection of essays from 1895,

“Dreams of Earth and Sky”8, can be found what many regard to be the earliest abstract imagining of the space elevator.

In this piece, Tsiolkovsky speculated on a variety of methods as to how the pull of gravity could be diminished, shifted, or even reversed entirely providing the application of a sufficient amount of external force. In explaining his ideas, he invited his readers to imagine entering into a clay pot being spun on a potter’s wheel, and how one would be able to stand on the inner walls as the pot was being spun due to the centrifugal force. Many of us today have actually been able to enjoy this very simulation owing to the proliferation of amusement parks. In my childhood it was known as the ‘The Mineshaft’, but the ride itself has no doubt been called by various other names I’m sure. Regardless, the mechanics are precisely the same as Tsiolkovsky described with his spinning clay pot many decades prior. Park goers enter into, and line their backs along the wall of a large cylindrical chamber. With the push of a button from the operator, the room begins to spin at increasingly faster speeds. The riders feel the generated force pressing upon their bodies, and find that when the floor is dropped out, they remain fixed to the walls of the spinning


chamber. The rotation of the room generates an artificial gravity in a manner similar to Tsiolkovsky’s clay pot hypothesis.

Further along in his essays, Tsiolkovsky took his speculations to even greater heights, for in calculating the centrifugal force that would be required for one to be free of Earth’s gravitational influence entirely, the Russian mathematician conceived of some rather unconventional means. He suggested that if one were to be riding a train that ran full circle around the equator at a speed of 18,000 miles per hour, the pull of gravity would be entirely reversed, and any passengers on board would become secured to the ceiling. You don’t have to be a train engineer to know that such speeds are nowhere near attainable as the fastest trains in the world currently top out at just over 300 miles per hour. Continuing this line of thought, Tsiolkovsky contemplated on the change in conditions if one were not trying to defeat gravity on the surface of the planet, where it is at its strongest. Instead he thought, why not use centrifugal force at a point where gravity is significantly diminished? Like space for instance.

Having been inspired by the Eiffel Tower on a recent trip to Paris, Tsiolkovsky imagined even grander towers situated at the

equator that stretched far into the heavens, at the top of which sat what he called ‘celestial castles’. With Earth’s gravity seeming to vanish entirely at what he measured to be a distance of 34,000 versts (roughly 36,000 kilometers, a.k.a. geostationary orbit), combined with the effects of the centrifugal force provided by the rotation of the planet, he suggested that anyone standing inside his celestial castle would be looking up at the Earth, instead of down, as the pull of gravity would be effectively flipped.

Though the system he described in “Dreams of Earth and Sky” sounds incredibly familiar to what is now recognized as the space elevator, Tsiolkovsky was never acknowledged as the inventor per se. The reasoning behind this is that he never bothered to calculate some rather significant factors pertinent to the elevator’s successful assembly and operation. Factors such as the material used for construction, how the line would need to double in width at certain intervals in order to support itself, how one would be transported to the top of the tower, or the need for a counterweight that extended much further than his castle at geostationary orbit to keep the entire system taut. Also devoid of any extensive numerical treatment, his ideas


have often been chalked up to the musings of a highly imaginative mind, or what many refer to as a ‘thought experiment’. Jerome Pearson expanded on this terminology:

“I really believe it was definitely a "thought experiment," in the manner of Einstein and the equivalence of gravity and inertial force in an accelerating elevator in space, quite often called in German, a ‘gedankenexperiment.’ Einstein did not describe exactly what was accelerating the elevator, what the cable was made of, or what velocities it would be going at--he was only interested in the observations inside the elevator. In the same way, Tsiolkovsky discussed his celestial castle and tower in terms of the observations of gravity as one went higher, and calculated the height of what we could call stationary orbit now; he wasn't concerned about building a real tower, as indicated by the fact that he calculated the stationary orbit altitude for the Sun as well!”9

The gauntlet of scientific analyses that would champion the label of invention was yet several decades down the road. In fact, it would be more than half a century before the space elevator would even be conceived of yet again.

Space Age Alternatives − Artsutanov and the Cosmic Railway

In 1960, a young engineering student in Leningrad by the name of Yuri Artsutanov, unaware at the time of Tsiolkovsky’s castle 65 years prior, independently conceived of what he called a ‘cosmic railway,’ the catalyst for which was an advancement in materials science that had recently been made in the United States. In 1957 to be precise, he learned that a super-strong material had been invented whose strength-to-weight ratio could theoretically allow for the construction of a cable up to 400 km in length without collapsing under its own weight. Artsutanov then took the idea of something even stronger; a fictitious super-material that could be used to extend a cable to an infinite length into the cosmos. That same material, as he imagined it, would serve as the rail in his cosmic railway. After a great deal of thought, his idea eventually made its way from the firing of neurons to the printed word, later published in the youth section of the daily Russian tabloid Komsomolskaya Pravda on July 31st, 1960. His piece, “To the Cosmos by Electric Train”, went into extensive detail regarding what is thought to be yet another earlier rendition of the space elevator. An interesting twist of


history was that it seemed to be an accident that it was published. Jerome Pearson explains:

“He was a graduate student, and didn't submit to an engineering journal. He had a journalist friend, Vladimir Lvov, who arranged to have his article published in the youth Sunday supplement to Pravda. Later, when John Isaacs published his space elevator article in Science, Lvov10 wrote a letter to Science saying that Artsutanov was first to publish the SE idea. Isaacs et al. replied, and agreed that after seeing Yuri's article and calculations, he was the first.”11

Artsutanov began with criticizing the rocket as being too dangerous and having too lengthy of a preparation process prior to each individual launch. So much so, that he emphasized its inefficiency as a means of getting off world. He then began to work with the previously established notion of ‘celestial moorings’, or orbital spaceports that would allow for the docking and embarkation of large interplanetary vessels. These way stations would also employ smaller shuttles to ferry people to and from the planetary bodies they orbited. Artsutanov’s permutation of this concept envisioned that instead of using smaller craft to transport people from the ground, travelers would

use railways that would extend into the sky, tying the ground terminals on the surface directly to their orbital counterparts above.

In many ways his system was similar to that of Tsiolkovsky’s in that the elevator would have to be placed on the Earth’s equator in order to utilize the centrifugal force generated by the rotation of the planet. In explaining his concept, he drew a metaphor between the space station revolving around the planet and a stone being swung around on the end of a string. He explained that just as the centrifugal force allowed the string to remain taut, so would the same be true for his cosmic railway. In some of the finer details however, his system differed from that of his unacquainted predecessor’s, particularly in that instead of a station placed at precisely the geostationary point at 36,000 km, it would instead be located 50-60,000 kilometers out. His “end of the line” as he called it, is from where he imagined interplanetary spaceships could depart on cosmic ventures into the solar system and beyond.

As a completely new element in the design, his model also employed the spaceport to serve a dual purpose in that it would simultaneously function as the counterweight for the entire system, helping to keep the line


taut, thereby preventing its collapse. While subsequent analyses have provided for estimates of counterweights attached at distances of 100,000 km and beyond, Artsutanov made it clear that he was well aware of this factor as a necessity in the system’s overall design. Even today, the need for a counterweight is still considered to be a requisite in the most up-to-date models of space elevators.

“To the Cosmos by Electric Train” also afforded its readers a bit of narrative in that it invited them to imagine the experience of a passenger making his or her way up the railway from the ground terminal to the orbital station overhead. In doing so, it allowed for the visualization of some of the finer conceptual details within the elevator’s design. After having left the surface, Artsutanov envisioned that at 5,000 km up, the rider would pass through a solar station that would use large collectors to generate power for the entire drive system, which itself would utilize an electromagnetic field to move the climber upward. At 36,000 km, where he estimated centrifugal force to overpower the Earth’s gravitational pull, he explained that the climber would no longer need to expend its own energy to continue the ascension as the rotation of the system with

the planet would provide enough energy to propel it further outward. As the rider reached his or her final destination at the spaceport 60,000 km from the surface below, they would see a collection of structures that comprised, as Artsutanov imagined it, a small city held down by simulated gravity that diametrically opposed the influence of the Earth.

While ostensibly airing on the side of fiction at this point, Artsutanov was sure to adhere to the very practical requirements, later corroborated by others, that would enable the elevator’s successful deployment. For example, he made it clear that construction would need to begin from a satellite placed at the geostationary point, where both the line being dropped to Earth and the one extending into space would need to be extruded simultaneously. This would be done in order to ensure that as the line reaching towards the surface became heavier with the increasing gravitational pull of the planet, the system could be kept in balance with the weight of the line reaching into space, which through the use of centrifugal force would negate the pull of the Earth.

He also drew attention to the need for the line connecting the spaceport to the Earth to exponentially increase in width as


it was produced and slowly threaded towards the surface. With the thickest part of the line at the geosynchronous spaceport, this would ensure that it would not snap, as there would be an enormous strain placed upon it by the rotating station once anchored to the planet below. Those who would later come to work on the space elevator would reaffirm this stipulation in even finer detail.

But even for all of Artsutanov’s unconventional concepts on constructing this revolutionary system, they were still predicated on a material that existed only in his mind. In 1960, there was no known physical substance whose strength-to-weight ratio could support such a gargantuan structure. Even today this still remains the elevator’s primary obstacle in becoming realized, which leads many to argue that an elevator could be possible on the moon, where the environmental conditions are far less demanding. In concluding “To the Cosmos by Electric Train”, Artsutanov made mention of this and stated that if two elevators, one on the Earth and the other on the moon, operated in tandem, the distance between the two bodies from surface to surface could be negotiated almost entirely without the use of fuel.

Super materials pending, Artsutanov’s first publication of a

space elevator article was sufficient to label him as one of two independent co-inventors of the elevator. And though his ideas were lacking in any kind of mathematical treatment, his thought processes included enough conceptual detail to have him recognized as one of the space elevator’s founding fathers. Despite this designation however, his piece was not received by a wide enough audience to gain any real footing in the scientific community, and for that reason, the space elevator remained in the shadows. Fortunately, it wouldn’t have to wait another 65 years before finally making its big debut.

Running the Numbers − Pearson and the Orbital Tower

In the five years prior to 1975, Jerome Pearson, an aerospace engineer for both NASA and the Air Force Research Laboratory, had been laboriously trying to persuade various scientific journals to publish his piece “The Orbital Tower: A Spacecraft Launcher Using the Earth’s Rotational Energy”. He was finally met with success when a 1975 volume of the journal Acta Astronautica featured what became the definitive piece that heralded the space elevator’s entry into the scientific


community and ultimately, the world. Since then, this incredibly futurist means of Earth-to-space transportation has gained a following of scientists and enthusiasts alike who devote their time and energy to merging the space elevator with reality. Just as Artsutanov had been unaware of the work of Tsiolkovsky before him, so too was Pearson of Artsutanov’s, which led to Pearson’s being identified as the other independent co-inventor. That, and the fact that his paper was the first mathematical presentation of the elevator designed to convince scientists and engineers that such a grandiose alternative to rocketry was not only theoretically possible, but also the right way to go.

Figure 2, Yuri Artsutanov and Jerome

Pearson12

His assiduous number crunching provided for what can perhaps be seen as a kind of evolutionary analogue in that if Tsiolkovsky’s ‘thought experiment’ can be

compared to that of a single-cell organism, the concept in its most nascent phase, then Pearson’s elaborate numerical treatment can perhaps be thought of as a bipedal hunter. Continuing with that metaphor, Artsutanov’s piece in 1960 might then be the proverbial ‘missing link’ between the two. But even for its being laden with esoteric formulas undecipherable by the layman, Pearson’s Orbital Tower still contained plenty of intelligible content to fire the imagination of your average space buff.

He began his assessment by imploring his readers to imagine a physical connection being made between a satellite at geostationary orbit and the Earth’s surface below. He suggested that through the use of this connection, the deployment and return of satellites and spacecraft to and from the planet would be much safer, and require far less energy which, as a consequence, would also make them cheaper.

Like Artsutanov before him, Pearson recognized many of the finer mechanical details pertinent to the elevator’s construction and operation. Details including the need for assembly to begin at the geostationary point so that the increasing weight of the cable reaching toward the planet could be counteracted by a separate cable extending


into space. But, whereas Artsutanov imagined his counterweight attached at a distance of 60,000 km, where it would double as a spaceport, Pearson fastened his at a much further distance of 144,000 km, nearly half the distance to the moon. As a matter of fact, Pearson’s design didn’t even call for a true counterweight per se as the sheer distance and mass of the line, and the outward force placed upon it by the spinning planet, would be sufficient to keep the structure standing. This enormously elongated line in Pearson’s model was of particular interest given that it paved the way to another major divergence in the two inventors’ designs.

Instead of interplanetary vessels departing from the station like ships from a harbor as proposed by his Russian counterpart, Pearson saw the elevator directly employing the inertia generated by the centrifugal movement of the rotating system to slingshot craft away from the planet. Essentially, it is like imaging the Earth as a giant discus thrower and any given spacecraft, the discus. The Earth rotates as a discus thrower would, thereby transferring the centrifugal force into the discus, or spacecraft, before releasing at full arm’s length. By his estimates, anything launched in this manner from appropriate distances above the

geostationary point would be able to reach as far out as Saturn without using any form of rocketry. This means that traveling to Mars for instance, would require no more energy than what was needed to reach geostationary orbit.

As for the power that would be needed to reach geostationary orbit from the surface, Pearson thought of that too. He suggested, again like Artsutanov, that perhaps this energy could be supplied by a solar power station attached to the elevator system. Either that, or through the capturing of energy from returning climbers as they descended the line back to Earth, generated via friction from braking that could be reabsorbed into the line.

This means that in 1975, Pearson associated sustainability with space travel on an entirely unprecedented level. His system would harness the rotation of the Earth to launch craft into space, thereby eliminating the need for rocket propulsion, while also generating its own power. I’m certain that if anyone were to have the space elevator explained in these terms, you would be hard pressed to find somebody who would believe it to be possible. Fortunately for his readers, Pearson backed it all up with countless calculations with which he thoroughly accounted


for every technical aspect of the elevator’s design and operation. Of those numerical computations, Pearson was certain to include those related to that one fundamental obstacle that continues to fetter the space elevator; the material, and its minimum strength-to-weight ratio.

Again, just as Artsutanov had done previously, Pearson identified the need for the elevator’s cable to be tapered in order to prevent the line from snapping due to the enormous tension that would be placed upon the system from both the downward pull of the planet and the counterweight being spun around it. Were the elevator to be constructed using steel, the tapering factor would require that the diameter of the cable be increased at such frequent intervals, that its widest point at geostationary orbit would be impractically large. Wider than the planet’s diameter in fact, given that the distance from Earth’s surface to geostationary orbit is roughly 36,000 km. With steel out of the equation, Pearson did theorize that a suitable candidate might be found with ‘perfect-crystal whiskers of graphite’, a material whose tapering ratio would require that the cable be only ten times larger in area at geostationary altitude than on the surface. At the time

Pearson wrote The Orbital Tower, this perfect rendering of graphite crystals could only be done on microscopic scales, a problem Pearson speculated could be rectified were they to be manufactured in a zero-gee environment, say from the point of the elevator’s construction at geostationary orbit. And though the production of super crystals in space is a project still pending, Pearson was certainly on to something in that the solution to this major hurdle might be found in carbon allotropy.

Historic Starts, Stops, and Discovery

Recognition has been given to Yuri Artsutanov and Jerome Pearson as the originators of the modern space elevators. They showed engineering solutions that lead to the remarkable work of Dr. Edwards13 as the 20st century changed over. These included an approach that showed the concepts of centrifugal force, the need for the cable to be reeled in and out from the GEO location, and the need for tapering the material with a wide ribbon to “beat debris.” There were a few groups during those early years who also discussed castles in the sky from GEO to the surface of the Earth. Two specific innovators were active in the field and then


relaxed their ideas and moved on to other questions. They were John Isaacs of Scripps Institute and Tom Logsdon of California Museum of Science and Industry. In 1966, a group of oceanographers led by John Isaacs at the Scripps Institute re-discovered the concept; but, they proposed such a thin wire that it would be cut by micro-meteoroids almost instantly, and was, therefore, completely impractical (Isaacs et al, 1966). Four engineers [Isaacs, Vine, Bradner and Bachus] determined what type of material would be required to build a space elevator, assuming it would be a straight cable with no variations in its cross section “Satellite Elongation into a true Sky-Hook.”14 By 1970, Tom Logsdon and Robert Africano developed an idea while teaching orbits early in the Apollo program. Their textbook showed the orbital characteristics of dropping off bodies at varying heights of their theoretical tower. They showed the strength of the location of drop-off with potential and kinetic energies leading to horizontal velocities which lead to elliptical orbits missing the Earth. Their concept was based upon a tower, not a ribbon. Much of their work was formalized inside “Rush to the Stars”15.

It was 1991 that saw the birth of that elusive material previously

relegated to fiction alone; carbon nanotubes (CNTs) have the strongest arrangement of a carbon molecule ever known. Since their discovery, CNTs have made big waves in material science, appealing to multiple fields and engineering megaprojects. Space elevator advocates were no exception as CNTs were found to not only meet, but far exceed the strength-to-weight ratio required in the tapering factor of the elevator’s lengthy cable. The problem however, similar to the perfect-crystal whiskers of graphite in the 70s, is getting them to lengths beyond that of the nanoscale, an achievement for which those who engage in CNT research hold frequent competitions.

Summary

As CNTs continue to grow to greater lengths, it is Jerome Pearson to whom credit can unquestionably be allocated in bringing the space elevator onto the world stage. Following his publication in 1975, the elevator soon worked its way into numerous works of science fiction such as Sir Arthur C. Clarke’s “The Fountains of Paradise”. Clarke contacted Pearson in 1976, beginning a lifelong friendship (Jerome Pearson visited Clarke in Sri Lanka, as shown in figure 3).


Between them, space elevator details were delineated while Clarke worked on his science fiction novel. Clarke recognized this help in the afterward of the novel by saying;

“As this book is (I hope) more of a novel than an engineering treatise, those who wish to go into technical details are referred to the now rapidly expanding literature on the subject. Recent examples include Jerome Pearson's ‘Using the Orbital Tower to Launch Earth- Escape Payloads Daily.16’"

Released in 1979, this seminal novel is often regarded to be the vanguard in bringing the space elevator to the attention of a wider public. In the same year, Charles Sheffield also published his science fiction novel “The Web Between the Worlds”17, which also featured the elevator as the central theme of its story. Interestingly, like that of Artsutanov and Pearson, Clarke and Sheffield were entirely unaware of each other’s work at the time, and in reference to this bizarre coincidence, Clarke is often quoted as saying, “This is an invention whose time has come.18” And while the space elevator remains far from deployment, the scientific work

1 International Space Elevator Consortium, http://www.isec.org

that has be done on it in the years following Pearson’s paper has only become more extensive as numerous individuals, groups, and organizations strive to see it realized. Between the International Space Elevator Consortium (ISEC), The Japanese Space Elevator Association (JSEA), EuroSpaceward, and groups like Liftport, whose goal is to have an elevator on the moon by the end of 2019, the space elevator is not without its burgeoning growth of supporters. One such organization, the International Academy of Astronautics, after a four year study, concluded:

Space Elevators Seem to be Feasible!

Figure 3, Sir Arthur C. Clarke and

Jerome Pearson19

2 Image by Frank Chase, www.chasedesignstudios.com.


3 Clarke, Arthur, The Fountains of Paradise, Harcourt Brace Jovanovich, 1979. 4 Robinson, Kim Stanley, Red Mars, Spectra/Bantam Dell, 1993. 5 Swan, P., C. Swan, D. Raitt, R. Penny, J. Knapman, Space Elevators: An Assessment of the Technological Feasibility and the Way Forward, Virginia Edition Publishing, 2013. 6 Artsutanov, Yuri, To the Cosmos by Electric Train, Komsomolskaya Pravda, July 31st, 1960. 7 Pearson, Jerome, The Orbital Tower: A Spacecraft Launcher Using the Earth’s Rotational Energy, Acta Astronautica. Vol. 2. pp. 785-799. Pergamon Press 1975. 8 Tsiolkovsky, Konstantin E., “Dreams of Earth and Sky,” Put´ k zvezdam: Sbornik Nauchno-Fantasticheskikh Proizvedenii (Moscow, USSR: Akademiya Nauk SSSR, 1960). 9 Personal conversation between Pearson and Peter Swan, 1 August 2015. 10 Lvov, Vladimir, Science, Vol. 158, pp. 946-947, 1967

11 Personal conversation between Pearson and Peter Swan, 1 August 2015. 12 Image by Jerome Pearson, 2006 13 Edwards, B. C. and Westling, E. A. (2003). The space elevator: a revolutionary Earth-to space transportation system. BC Edwards, 2003. 14 Isaacs, John D., Allyn C. Vine, Hugh Bradner, George E. Bachus, “Satellite Elongation into a true Sky-Hook,” Science, 151, 682-683, 1966. 15 Logsdon, T. and R. Africano, Rush to the Stars. [Franklin Publishing Company, Inc. NJ. 1970.] 16 Afterward, Clarke, Arthur, The Fountains of Paradise, Harcourt Brace Jovanovich, 1979. 17 Sheffield, Charles. The Web Between the Worlds, Baen, 2001. 18 Clarke, Arthur C., http://www.spaceward.org/elevator-who. 19 Image by Jerome Pearson, in Sri Lanka, 1988


INTERNATIONAL LAW AND THE

CONSTRUCTION AND OPERATION OF A TETHERED

SPACE ELEVATOR: International Space Elevator

Law as a Functioning Academic Discipline1

Stefan Kirchner2 About the author: Dr Stefan Kirchner, MJI,

is a member of the bar in Frankfurt am Main (Germany) and is specializing in

international human rights litigation and the international law of the sea at his law

firm CrossLegal (www.crosslegal.com). He has taught human rights and law of the sea

at universities in Germany, Lithuania, Ukraine and Finland and has worked as a lawyer for Germany’s Federal Maritime

and Hydrographic Agency in Hamburg and as Assistant Professor for International

Law and for the Law of the Sea in Kaunas, Lithuania. He is the founder of the OCEAN

Network, an NGO dedicated to the protection of the marine environment

(www.ocean-network.org). Formerly a Co-Chair of the Rights of Indigenous Peoples

1 This article is based on a blog entry published earlier this year, Stefan Kirchner, Space Elevator Liability Rules: when do we need them?, 24 February 2015, <https://rladi.wordpress.com/2015/02/24/space-elevator-liability-rules-when-do-we-need-them/> last visited 14 April 2015, see also Stefan Kirchner, International Law Challenges of Liability Regulation for Space Elevator Tourism, in: Journal of Brief Ideas, 24 February 2015, <http://beta.briefideas.org/ideas/711826afae

Interest Group of the American Society of International Law (www.asil.org), he

currently fulfills the same role at ASIL’s Law of the Sea Interest Group. This text only reflects the author’s private opinion

and is not to be attributed to any institution or organization the author is or has been

affiliated with.

Abstract: The idea of a tethered space elevator is no longer the stuff of science fiction but has been occupied scientists and engineers already for some time. Recent developments in the field of carbon nanotubes with very high tensile strengths which would allow the formation of long chains which could form the core of a tether have brought the space elevator nearer to the realm of technical possibility, albeit one which still requires a number of issues to be dealt with. In this article it will be shown that while the construction and operation of a tethered space elevator is highly complex also from a legal perspective, this complexity can actually be dealt with to a large extent through legal rules which are already in existence today and which already bind many of the states which are likely to have an interest in a space elevator project. It will also be shown that even liability rules for extreme events such as a complete tether destruction and tetherfall back to Earth can be addressed under the

9025361fab74142ebe7fc3#sthash.aoif4nF6.dpuf> last visited 14 April 2015. Some errors still contained in the original blog entry have been corrected. 2 Senior Lecturer for Fundamental and Human Rights, with Special Focus on Indigenous Righty, Faculty of Law, University of Lapland, Rovaniemi, Finland; Rechtsanwalt, CrossLegal, Antrifttal, Germany; Global Coordinator Email: [email protected].


lex lata. Also the participation and indeed leading role of non-state actors can be facilitated under existing rules. While if necessary limitations and need for further developments will be indicated, the main thesis of this article is that International Space Elevator Law is already emerging as a legal discipline in its own right and it brings together aspects of general Public International Law, International Space Law, International Law of the Sea, International Environmental Law, Human Rights, but also Private International Law and Conflict of Laws issues. The new academic discipline of International Space Elevator Law will be tasked with navigating the cross-sections between these fields of law and to creatively build on existing rules and contribute to the development of new rules as needed.

3 Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 735. 4 Ibid. 5 Ulf von Rauchhaupt, Die achtmillionste Etage, in: Frankfurter Allgemeine Zeitung, 2 October 2014, <http://www.faz.net/aktuell/wissen/weltraum-aufzug-wuerde-die-raumfahrt-revolutionieren-13177163.html?printPagedArticle=true#pageIndex_2> last visited 14 April 2015; Kilian A. Engel, Lunar transportation scenarios utilising the Space Elevatory, in: 57 Acta Astronautica (2005), pp. 277-287, at p. 277. 6 Cathy W. Swan / Peter A. Swan, Why we need a space elevator?, in: 22 Space Policy (2006), pp. 86-91, doi: 10.1016/j.spacepol.2006.02.008, at p. 86. 7 For an alternative suggestion to the tether solution see B. M. Quine / R. K. Seth / Z. H. Zhu, A free-standing space elevator structure: A practical alternative to the

Keywords: Space Elector, Tether, Public International Law, Liability, Private International Law, Law of the Sea, Human Rights.

Introduction

In the last quarter of a century, technological advancements (in particular work on carbon nanotubes with a tensile strength of 130 GPa and a density of 1300 kg/m3,3 which makes them less dense and more than 36 times stronger than Kevlar4) have moved the idea of a tethered space elevator from the realm of science fiction to that of engineering.5 While the term “elevator” is technically not correct in so far that the tether serves more like a rail (or “track”6) for a space railway as the climber is moving along the tether7 (or

space tether, in: 65 Acta Astronautica (2009), pp. 365-375, doi: 10.1016/j.actaastro.2009.02.018; see also Kai Sunao, The Law of the Space Elevator - The relationship to the Law of the Space, the Sea and the Sky, <http://www5a.bioglobe.ne.jp/～kaisuno/ronbun/law_of_space_elevator.html> last visited 1 April 2015, I. 1. (3), who proposes “a cyclindrical tower of 100,000 kilometers in height and a 32 meter radius [and thus establishes a plan to create a] total floor space […] larger than the continental surface area of the Earth” (ibid.), albeit without explaining the concept, which raises numerous questions, in more detail. The concept might be connected to the same author’s note that a tether, “a thin, almost invisible line extending towards the sky” (ibid. III. 3.) would be “a breach of the Chicago Convention [on International Civil Aviation” (ibid.). While Kai argues that “every tower-shaped construction needs


“ribbon”8) but not pulled by the tether. The term will, however, be used as it is well-established, also in academic literature. The construction of a space elevator had been estimated to be a technical reality around the year 2030.9 These estimates need to be taken with a grain of salt10 but in recent decades the space elevator has become a technical challenge rather than a concept. This makes it necessary for lawyers to address questions which can possibly come up in the context of the construction11 and

aircraft warning paint for the daytime and aircraft warning lights during the night” (ibid.), the presence of a space elevator tether would have to be accompanied by aerial exclusion zones anyway, similar to those already in place around the world e.g. near nuclear power plants and the like. From a legal perspective, regardless of the location of the base-station on land or on sea, this is an issue which can be solved. In the grand scheme of things, the color choice of the biggest object ever made by man should not be a major issue if safety against aerial intrusion can be guaranteed otherwise, see also Article 60 of the United Nations Convention on the Law of the Sea and Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at p. 89. On the Chicago Convention (15 United Nations Treaty Series 295) see also Ruwantissa Abeyratne, The Legal Status of the Chicago Convention and its Annexes, in: 19 Air and Space Law (1994), pp. 113-123. At the time of writing, the tether solution seems to be the preferred approach (see also e.g. Parag Mantri, Deployment dynamics of space tether systems, Ph.D. Thesis, North Caroline State University (2007); David Smitherman Jr., Space elevators - Building a permanent bridge for space exploration and economic development, AIAA Space 2000 Conference & Exposition, 19-21 September 2000, AIAA

operation of a space elevator. It will be shown in this article that while some questions still need to be answered, many of the future problems can be dealt with on the basis of existing legal tools, although it has to be kept in mind that many questions will only emerge over time and it is likely that there will be issues which will emerge based on specific technical challenges, not all of which can be known at this time. In so far this issue will have to be

Meeting Papers A00-42952) and this paper is solely concerned with that concept. 8 Cathy W. Swan / Peter A. Swan, Why we need a space elevator?, in: 22 Space Policy (2006), pp. 86-91, doi: 10.1016/j.spacepol.2006.02.008, at p. 86. 9 Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at p. 73, refers to two commercial plans to have a space elevator operative by 2029 or 2031 respectively, but see also the next footnote. 10 While one of the two companies referred to in the text referred to in the last footnote no longer seems to be in business, the other (LiftPort Group) now concentrates on “Lunar Space Elevator Infrastructure” (Liftport Group, The Lunar Elevator, <lunarelevator.com> last visited 15 April 2015.). 11 See David D. Lang, Space Elevator Initial Construction Mission Overview, <http://home.comcast.net/~GTOSS/Paper_Lang_GEO_Deploy.pdf> last visited 15 April 2015, pp. 2 et seq.; Robert Raymond Boyd / Dimitri David Thomas, Space Elevator, Patent US 6491258 B1, <https://www.google.com/patents/US6491258> last visited 1 April 2015; James G. Dempsey, System and method for space elevator, Patent US 69816474 B1, <http://www.google.com/patents/US6981674> last visited 1 April 2015.


revisited again and again in the future.

From the perspective of international law, the space elevator raises important questions. Under international law as it is now, national sovereignty extends from the center of the earth (where all subterranean national borders meet) to the so called Kármán line 100 km from the level of the sea.12 In this area, national law applies.13 Above the Kármán line Outer Space begins and hence International Space Law applies. Most of the space elevator therefore would be in outer space, but it would be dependent on a part which falls squarely within a national jurisdiction — or the high seas legal regime as there are plans 12 Cf. Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at p. 93. 13 In the 1970s, attempts were made by equatorial nations to secure claims to the geostationary orbit as a national resource (Glenn Harlan Reynolds, International Space Law in Transformation: Some Observations, in: 6 Chicago Journal of International Law (2005), pp. 69-80, <http://chicagounbound.uchicago.edu/cjil/vol6/iss1/7> last visited 1 April 2015, at p. 77), e.g. through the 1976 Declaration of Bogota. These attempts have failed (Glenn Harlan Reynolds, International Space Law in Transformation: Some Observations, in: 6 Chicago Journal of International Law (2005), pp. 69-80, <http://chicagounbound.uchicago.edu/cjil/vol6/iss1/7> last visited 1 April 2015, at p. 77) but might be revived as work on the space elevator advances (ibid., pp. 77 et seq.). At least for now, this seems to be a potential political issue but it appears highly unlikely

for space elevator base stations at sea. A base station in the high seas does only solve part of the problem as the base has to fall under some national jurisdiction because it is the states which have the right to construct installations under Article 87 (1) (d) of the UN’s Law of the Sea Convention14 (LOSC15). In outer space, the law of the state in which a vessel is registered applies (assuming that the climber is a spacecraft in the legal sense of the term, an issue to which we will get back in a moment). This makes a space elevator the object of a range of legal systems, regardless of whether the tether and / or the climber is operated by a state, a

that a new rule of customary international law or an international treaty binding upon all states concerned with the use of the geostationary orbit will emerge to the effect that equatorial states’ sovereignty were to include the geostationary orbit above their national territory. Nevertheless might such political assertions, should they arise, become relevant for political and / or corporate decision-makers. 14 United Nations Convention on the Law of the Sea, <http://www.un.org/depts/los/convention_agreements/texts/unclos/unclos_e.pdf> last visited 14 April 2015. 15 The abbreviation LOSC is used here in preference over the often used abbreviation UNCLOS in order to avoid confusion between this document and the series of UN Conferences on the Law of the Sea in the second half of the 20th century which are also referred to as UNCLOS I-III. Essentially, LOSC was the final point in a legal development spanning several decades and the result of UNCLOS III.


corporation, an international organization16 or another entity.17

Existing research places emphasis on the different international legal regimes of the law of the sea, air law and space law18 and on liability,19 issues which will also feature here, although it is the attempt of this author to go beyond the functions provided established literature by bringing legal and technical sides of the development closer together. What this article will not deal with are contract law questions which 16 This is proposed by Kai Sunao, The Law of the Space Elevator - The relationship to the Law of the Space, the Sea and the Sky, <http://www5a.bioglobe.ne.jp/～kaisuno/ronbun/law_of_space_elevator.html> last visited 1 April 2015, I. 1. (2) (iii). While this is certainly an option, I do not share Prof. Kai’s view (ibid.) that this is the only option available under international law. While existing International Space Law is still based on the paradigm of spacefaring by states, the continued relevance of the lex lata despite the emergence of private space travel (with a national regulatory component, very similar to air and sea travel) is evidence for the applicability of existing legal rules which were written under conditions which were dominated by states also to the current situation. Indeed, many norms of Public International Law are based on the paradigm of the state as the central element of international relations. While states no longer enjoy the dominant position in international law they used to have prior to 1945, they continue to be at the core of the international legal system and yet this system has not only allowed for the emergence but for the accommodation of non-state actors in a wide range of sub-fields of Public International Law (an excellent overview is provided by Andrea Bianchi (ed.), Non-State Actors and International Law, 1st ed., Ashgate, London (2009), which collects essays from leading international law experts on the role of non-state actors, most of which from the early

will depend on the legal systems of actors which will be involved in the planning and operation of the tether and climbers. The focus of the article are international legal issues with a particular focus on liability questions and selected practical questions.

Base-Station Location Choices

The point of departure for this paper is the selection of a base-station,20 i.e. the location of the

years of the 21st century but also dating back to 1970). 17 For a relatively state-based view on the space elevator project see Mark S. Avnet, The space elevator in the context of current space exploration policy, in: 22 Space Policy (2006), pp. 133-139, doi: 10.1016/j.spacepol.2006.02.005. 18 For a brief overview over the key legal issues see Bradley C. Edwards, The Space Elevator NIAC Phase II Final Report, 1 March 2003, <http://www.niac.usra.edu/files/studies/final_report/521Edwards.pdf> last visited 15 April 2015, p. 25. 19 Romain Loubeyre, Questioning the Space Elevator Legal Risk Management Regime, in: 1 CLIMB (2011), pp. 67-75. 20 The also used term “anchor” (Cathy W. Swan / Peter A. Swan, Why we need a space elevator?, in: 22 Space Policy (2006), pp. 86-91, doi: 10.1016/j.spacepol.2006.02.008, at p. 86) creates the impression of immobility, which is not only not necessary, in the case of a sea-based end point on Earth some mobility in order to react to local phenomena (weather, nearby accidents etc.) will be desirable. Unlike in the case of a fixed installation at sea, the use of a ship as a base-station (as suggested ibid.) would not allow for an exclusion around the end point, only normal maritime traffic rules would apply. Therefore a fixed installation appears preferable if a maritime point of departure is chosen. This will also be reflected in the


starting/end21 point of the space elevator’s cable or tether on Earth. Essentially there are two major options: a sea-based or a

considerations made in the remainder of this paper. 21 During the construction phase, the cable would have to be lowered from space (Luboš Perek, Between a celestial body and a spacecraft: Making the space elevator a success, in: 23 Space Policy (2007), pp. 3-6, at p. 3; Luboš Perek, Space Elevator: Stability, in: 62 Acta Astronautica (2008), pp. 514-520, doi: 10.1016/j.actaastro.2008.01.020, at p. 515; Noboru Takeichi, Geostationary station keeping control of a space elevator during initial cable deployment, in: 70 Acta Astronautica (2012), pp. 85-94, doi: 10.1016/j.actaastro.2011.07.016, at p. 85; Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 737), in so far it would be one end point (the other end, beyond the geostationary orbit would in this sense also be an end point. In terms of travel, though, this point is the starting point for trips from Earth and the end point for trips to Earth. Especially in the case of a sea-based space elevator, this point can be mobile Therefore the deliberately vague term ‘base-station’ is used. The acquisition of a celestial body for use as a counterweight (if a tether shorter than 144,000 km is used, Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 735) is problematic under current international law as ownership of celestial bodies is not necessarily compatible with Article II of the Outer Space Treaty (Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies, 27 January 1967, 610 United Nations Treaty Series 205), Even half a century after its conception the five key treaties which have been drafted under the auspices of the United Nations (in addition to the Outer Space Treaty these are the Agreement on the Rescue of Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space, 22 April 1968, 672 United Nations Treaty Series 119, the Convention on International Liability for

land-based approach. In either case a location on or near the equator is desirable.22

Damage Caused by Space Objects, 29 March 1972, 961 United Nations Treaty Series 187 and the Agreement Governing the Activities of States on the Moon and Other Celestial Bodies, 18 December 1979, 1363 United Nations Treaty Series 21) remain at the heart of International Space Law (Jackson Nyamuya Maogoto / Steven Freeland, A Contemporary Review of the Air Space and Outer Space Regimes - The Thin Lines Between Law, Policy, and Emergent Challenges, in: Sanford R. Silverburg (ed.), International Law - Contemporary Issues and Future Developments, 1st ed., Westview Press, Boulder (2011), pp. 300-317, at p. 302). Article II of the Outer Space Treaty prohibits states from exercising sovereignty over celestial bodies, although it is not necessarily clear that this prohibition includes a prohibition for states to allow for private law ownership of domestic bodies or parts thereof under national law (Alan Wasser / Douglas Jobes, Space Settlements, Property Rights, and International Law, in: Sanford R. Silverburg (ed.), International Law - Contemporary Issues and Future Developments, 1st ed., Westview Press, Boulder (2011), pp. 275-299, at p. 277, with further references). However, it has been noted that this rule might not hold up forever as there will eventually be commercial use of celestial bodies (including by non-state actors) which will then require some protection of rights (ibid., pp. 288 et seq.). On questions of ownership in Outer Space see in more detail Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at pp. 90 et seq. 22 But see also Blaise Gassend, Non-Equatorial Uniform-Stress Space Elevators (2004), <http://gassend.net/publications/NonEquatorialUniformStressSpaceElevators.pdf> last visited 15 April 2015; John R. Hull / Thomas M. Mulcahy, Magnetically Levitated Space Elevator to Low-Earth Orbit (2001), para. 3.5.


From an international law perspective a location in the high seas23 might seem preferable at first in order to avoid national jurisdictions of a territorial state. But this would not actually be the case as some state would have to claim jurisdiction over the base station. A flagless vessel on the high seas would be without legal protection and could be brought up by vessels from any state under both the United Nations Convention on the Law of the Sea24 and under customary international law. The latter aspect is particularly important from the perspective of states, such as the United States, which are likely to have an interest in a space elevator project but, while not having ratified LOSC, are bound by customary international law. The jurisdiction of the flag state of such a vessel might be of different origin than the jurisdiction of a state over its territory but the high seas do not mean freedom from all forms of national regulation.

A sea-based solution however brings with it a significant 23 Articles 86 et seq. United Nations Convention on the Law of the Sea. 24 Article 110 (1) (d) United Nations Convention on the Law of the Sea. 25 Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 738. 26 Ibid., pp. 738 et seq. 27 Cathy W. Swan / Peter A. Swan, Why we need a space elevator?, in: 22 Space Policy (2006), pp. 86-91, doi: 10.1016/j.spacepol.2006.02.008, at pp. 86

problem. Energy transfer e.g. by laser25 or microwave26 to a climber which is powered by electrical motors27 can be hampered by the presence of water in the air.28 While a combination of a land-based laser and a sea-based tether has been proposed,29 a land-based tether remains an important option. There are however a number of aspects which need to be taken into account.

In addition to the latitude near the equator, the aforementioned energy-related benefits of land-based operations over sea-based operations are only relevant at a minimum altitude of about 5,000 meters above sea level.30 This limits the sites which are potentially useful. The Tepuis in the Guiana Highlands are interesting due to their mesa-like structure but their altitude is too low, not to mention that there are enormous concerns concerning the natural environment and indigenous rights there. The latter aspects are also among issues which need to be taken into account in other potential

et seq.; cf. also the linear electrostatic propulsion system proposed by Alexander Bolonkin, Electrostatic Climber for Space Elevator and Launcher (2007), <http://arxiv.org/pdf/0705.1943.pdf> last visited 15 April 2015. 28 Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 741. 29 Ibid. 30 Ibid.


locations. While, assuming such issues could be dealt with effectively, at first sight the Chimborazo31 would be a good location, although it is a (in the last centuries inactive) volcano. Given the risk to human life and the importance of the space elevator infrastructure for mankind as a whole and taking into account the inability to prevent volcanic eruptions and earthquakes even more than a millennium of inactivity might not be sufficient to provide the level of safety which is desired in such a project. In addition safety considerations such as weather patterns,32 the likelihood of lightning strikes33 but also respect for environmental and cultural aspects and for the human rights and their democratic consent to such a major project of the local population will be required in determining the location for a space elevator’s base-station.

While a climber would require a kind of space-lifeboat-style emergency system for a safe return to Earth in case of disruption of operations, such as

31 Cf. ibid., p. 742. 32 Ibid., p. 741. 33 Ibid., there (pp. 741 et seq.) two particular areas are mentioned, at sea off the coasts of Ecuador and Tanzania respectively. 34 Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 742. 35 See A. M. Jorgensen / S. E. Patamia / B. Gassend, Passive radiation shielding considerations for the proposed space

the severance of the cable,34 the project requires high levels of safety, if it is to attract widespread users. If travel by space elevator is ever to become widespread, the level of safety has to approach that of today’s air travel rather than that of the first experiments with manned flight several generations ago. Space travel remains inherently dangerous (which includes not only the risk of accidents but also the need for shielding against radiation35) but a broader access to space travel will also lead to other expectations of safety.36 What is perceived as ‘normal’ will be associated with an inbuilt expectation of safety. The space elevator is different from flying to space in a rocket. This will have to be taken into account already at the planning stage.

The same applies to the concerns of non-users. In case of tetherfall a large area will be affected by a large amount of debris which might pose an unprecedented environmental problem which required more research.37

elevator, 60 Acta Astronautica (2007), pp. 198-20, at pp. 199 et seq. 36 Cf. Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at p. 96. 37 Bradley C. Edwards, Design and Deployment of a Space Elevator, in: 47 Acta Astronautica (2000), pp. 735-744, at p. 742.


Liability Rules

Manmade systems are not perfect and there is a risk of eventual failure, resulting in damages to material, the environment or even human health or human lives. This brings us to the question of liability rules.

A Space Elevator raises a number of issues from the legal perspective. Below an altitude of 100km national law38 and international air law apply.39 Above, international space law would govern the elevator. Choosing a base station on land or at sea adds another level of complexity to this issue. Is the elevator one structure to which different legal rules apply in different parts of the structure? Or is the transport unit which rides along the elevator line a spacefaring vessel and too simple to be treated no different from the way international law treated the Space Shuttle? Also for passengers, this will raise a

38 See e.g. Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at pp. 75 et seq. 39 On International Air Law aspects of a space elevator project see in more detail Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at pp. 92 et seq. 40 Athens Convention relating to the Carriage of Passengers and their Luggage by Sea, 1463 United Nations Treaty Series 19.

number of questions. For the shipping industry on Earth’s oceans, the Athens Convention40 regulates insurance requirements for passenger ships on international trips. What will be necessary from the perspective of passengers who will board climbers will be similar liability rules (and a certain sense of safety to begin with41). But while passenger shipping has been around for centuries prior to the introduction to such rules, strict liability rules and insurance obligations are likely to make it even more difficult for startups to enter the market. This problem might be relatively small given the overall costs and efforts associated with building and operating a space elevator but it needs further investigation.

Under existing international space law, spacecraft have the nationality of a state, like ships or aircraft, and the state in question is liable for damages cause abroad,42 as the USSR had been

41 See also Peter A. Swan, Safe Space Elevator - An Expectation to be Met Through a System Architecture Approach (2004), <http://images.spaceref.com/docs/spaceelevator/iac-2004/iac-04-iaa.3.8.3.06.swan.pdf> last visited 15 April 2015. 42 But there are particular details to be noted when it comes to International Space Law as compared to general rules, see e.g. Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97: “If a collision does occur, liability


liable for the damages caused by a crash of a Soviet satellite in Canada.43 While it could be argued that a climber is not a

issues will certainly arise. The Outer Space Treaty affixes international liability to the launching state, even for the activities of its nationals. In the case of a collision between a space elevator under United States jurisdiction and a space object launched by another state party to the treaty, both launching states would remain liable to each other on an international level, and the loser would have to indemnify itself by pursuing the offending party. The Liability Convention also affixes liability, but it does so to different degrees depending on the circumstances that surround the collision. Under Article II of the Convention, a launching state is absolutely liable for any damage incurred by its launch to person or property located on the earth, or to aircraft—although this liability can be mitigated if the damage is the result of malicious activity. In cases involving collisions between two space objects, a fault-based analysis applies rather than strict […] liability. This is extremely relevant to the operation of a space elevator, because once it has been deployed and registered [assuming that the space elevator is also a spacecraft in the legal sense of the term], presumably other launching states would have constructive notice of its existence and location—and the onus to avoid a collision would rest with subsequent launching states and to the operators of the space elevator to the degree they could avoid or mitigate a collision” (ibid., pp. 94 et seq., footnotes omitted). This approach has the benefit of the elegance of allowing for one legal regime for different modes of transport from Earth to orbit, rockets, space elevators and future, currently not yet planned, modes of transport. However, as the same author notes “[o]bjects already in orbit present a more serious problem in terms of liability. […] The Liability Convention doesn’t provide any absolute rules for how fault is determined, only that they are to be presented and resolved through diplomatic channels. Presumably, the burden to avoid a collision with already orbiting objects would ultimately rest with the operators of the space elevator, unless the offending space object could be controlled by its

spacecraft44 because it is not launched”,45 I believe that the case can be made that the term

launching state in such a way as to avoid or mitigate the collision.“ (ibid., p. 95, footnotes omitted) However, it has to be noted that the ability of the other to avoid a collision with the tether does not necessarily free the operator of the space elevator from all responsibility as an abstract danger has been created in the form of the space elevator which then would have contributed to the collision. It appears likely that, at least with regard to third party damage as a result of tetherfall, operators and nation states will face some level of residual responsibility and liability. This issue, though, is not primarily one of liability but first and foremost one of avoidance. Indeed, the risk of destructive events in connection with already orbiting items is significant and it might hamper efforts to implement the construction of a space elevator on Earth. At the end of the day the current amount of orbiting objects, including in particular debris, might severly restrict mankind’s near-term access to space. Continued reliance on non-reusable technology has the potential to close the door to space and poses a risk the dimensions of which might not be fully understood at this time. 43 See Eilene Galloway, Nuclear Powered Satellites: The U.S.S.R. Cosmos 954 and the Canadian Claim, in: 12 Akron Law Review (1979), pp. 401-415. 44 For a discussion as to the legal nature of the climber within International Space Craft see Glenn Harlan Reynolds, International Space Law in Transformation: Some Observations, in: 6 Chicago Journal of International Law (2005), pp. 69-80, <http://chicagounbound.uchicago.edu/cjil/vol6/iss1/7> last visited 1 April 2015, at p. 79. 45 For an overview over the discussion of the importance of the term “launch” in International Space Law against the background of the new starting mechanisms offered by the space elevator see in more detail Glenn Harlan Reynolds, International Space Law in Transformation: Some Observations, in: 6 Chicago Journal of International Law (2005), pp. 69-80, <http://chicagounbound.uchicago.edu/cjil/vol6/iss1/7> last visited 1 April 2015, at pp. 78 et seq.


“launch” includes any means46 by which a vessel enters outer space from Earth or in the future from locations outside Earth, which would also cover situations in which the spacecraft has never been on Earth because it has been constructed in space, be it in orbit or on another celestial body. Essentially, climbers should therefore be treated as spacecraft,47 either by, as suggested here, assuming that they are spacecraft or by extending existing legal rules for spacecraft to climbers by means of analogy. While avoided in criminal law for sake of clarity of the law according to the principle nulla poena / nullum crime sine lege praevia, certa, scripta (no penalty / no crime without a prior, clear and written law), analogy is a legal tool which

46 Cf. John R. Hull / Thomas M. Mulcahy, Magnetically Levitated Space Elevator to Low-Earth Orbit (2001). 47 An interesting alternative view is offered by Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at p. 93, who holds that “the Liability Convention […] defines “space object” to include the component parts of a space object and the component parts of its launch vehicle. The anchor station, ribbon, and counterweight would all fall under one of those two categories.” (ibid.footnote omitted). 48 The use of a legal analogy requires a gap in the law. It is not a legal technique which would be meant to circumvent existing rules. 49 Tetherfall can be caused by external damage to the tether (see e.g. Luboš Perek, Between a celestial body and a spacecraft: Making the space elevator a success, in: 23

is used in many legal systems in order to fill gaps in the law48 and which can also be applied in international space law. In addition, like in the case of the early years of international space law, customary international law can emerge very quickly, if not instantaneously, in a new field of law. If all states were to treat a climber like any other spacecraft, e.g. by requiring registration under national spacecraft laws, it seems not unlikely that a norm of customary international law to the effect that climbers are spacecraft will emerge before the first climber will have left the ground. In the long run, it will be in the interest of everybody involved to have clear liability rules for climber operations.

Not even tetherfall49 liability will necessarily require new

Space Policy (2007), pp. 3-6, at pp. 4 et seq.) or by internal processes inherent in nanotubes (cf. ibid., p. 5, and already Gen-Wei Wang / Ya-Pu Zhao / Gui-Tong Yang, The stability of a vertical single-walled carbon nanotube under its own weight, in: 25 Materials and Design (2004), pp. 453-457). On internal processes latter see Nicola M. Pugno, Towards the Artsutanov’s dream of the space elevator: The ultimate design of a 35 GPa strong tether thanks to graphene, in: 82 Acta Astronautica (2013), pp. 221-224, who proposes the use of graphene bundles). Tether stability questions are dealt with in a number of other publications, e.g. Luboš Perek, Space Elevator: Stability, in: 62 Acta Astronautica (2008), pp. 514-520, doi: 10.1016/j.actaastro.2008.01.020; Nicola M. Pugno, On the strength of the carbon nanotube-based space elevator cable: from nanomechanics to megamechanics, in: 18 Journal of Physics: Condensed Matter


regulation. One might think so at first sight as the tether is clearly not a spacecraft. But if the construction or operation of a tether is permitted by a state on its territory or undertaken by a state on the high seas the state in question is obliged already under current rules of international environmental law to refrain from activities which can harm other states.50

(2006) S1971, doi: 10.1088/0953-8984/18/33/S14; Nicola M. Pugno, Space elevator: out of order?, in: 2:6 NanoToday (2007), pp. 44-47; Nicola M. Pugno, The role of defects in the design of space elevator cable: From nanotube to megatube, in: 55 Acta Materialia (2007), pp. 5269-5279, doi: 10.1016/j.actamat.2007.05.052; Nicola Pugno / Michael Schwartzbart / Alois Steindl / Hans Troger, On the stability of the track of the space elevator, in: 64 Acta Astronautica (2009), pp. 524-537, doi: 10.16/j.actaastro.2008.10.005. In addition, the simultaneous operation of several climbers on one tether will have effects on the tether’s stability, which adds an additional level of risk (see David D. Lang, Space Elevator Dynamic Response to In-Transit Climbers, <http://spaceelevatorwiki.com/wiki/images/2/2b/Paper_Lang_Climber_Transit.pdf> last visited 15 April 2015; Stephen S. Cohen / Arun K. Misra, Elastic Oscillations of the Space Elevator Ribbon, in: 30 Journal of Guidance, Control, and Dynamics (2007), pp. 1711-1717; Stephen S. Cohen / Arun K. Misra, Static deformation of space elevator tether due to climber, in: 111 Acta Astronautica (2015), pp. 317-322; Stephen S. Cohen / Arun K. Misra, The effect of climber transit on the space elevator dynamics, in: 64 Acta Astronautica (2009), pp. 538-553, doi: 10.1016/j.actaastro.2008.10.003; P. K. Aravind, The physics of the space elevator, in: 75 American Journal of Physics (2007) 125, doi: 10.119/1.2404957; Paul Williams / Wubbo Ockels, Climber motions for the tethered space elevator, in: 66 Acta Astronautica (2010), pp. 1458-1467, doi:

In the case of a sea-based base-station only one small level of complication is added, which is resolved easily, though: the base-station, being located on the high seas, is thus outside the territory of any state. But this does not mean that no state would have jurisdiction: if the base station is registered in a state,51 then the flag state has jurisdiction. If the base station were a

10.1016/j.actaastro.2009.11.003; Pamela Woo / Arun K. Misra, Dynamics of a partial space elevator with multiple climbers, in: 67 Acta Astronautica (2010), pp. 753-763: Pamela Woo / Arun K. Misra, Mechanics of very long tethered systems, in: 87 Acta Astronautica (2013), pp. 153-162.). While wake turbulence is a well known phenomenon in aviation, the research on effects between climbers is so far only theoretical in nature and will require more attention as work on the space elevator advances. 50 See e.g. Stefan Kirchner, State Responsibility for Transboundary Ecological Damage: the Case of the Amur River Benzole Spill in China, in: Areti Krishna Kumari (ed.), Water Pollution: Problems & Perspectives, 1st ed., Amicus Books, Hyderabad, India (2007), pp. 223-242; Stefan Kirchner, Grenzüberschreitende Umweltrisiken und internationale Kooperationspflichten, in: 21 (1) Jurisprudencija (2014), pp. 306-319. 51 This would be the case e.g. if the base station would be floating and were constructed in analogy to a mobile offshore drilling unit (MODU), which is not a ship in the classical sense of the term but has small engines which enable it to move and hold position and which thus is registered in a nation state, has a registration number by the International Maritime Organization (IMO) etc. See also Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at p. 87.


constructed artificial installation, then under Article 87 (1) (d) of the Law of the Sea Convention states would have the right to construct such installations.52 Corporations would thus have to act on behalf of a nation state. Article 87 (1) (d) LOSC is a key factor in why a base-station on the high seas would not be independent of the state.53

All of these issues represent solvable problems — assuming that the climber is under the jurisdiction of a nation state which can impose its laws on it. There is, however, one aspect which makes a space elevator fundamentally different from other modes of transport. Unlike even spaceships, the space elevator system, or at least the first space elevator, will arguably be so expensive that only a concerted effort of multiple actors will be sufficient to achieve its construction and continued operation. At this level, it might make sense to simply price in a compensation system for accidents but there is one consideration which is far more important than economic

52 Cf. Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, pp. 88 et seq. 53 As the case of “Sealand” has shown, an artificial installation itself also cannot provide the basis for a new state, but see also Andrew H. E. Lyon, The Principality of Sealand, and its Case for Sovereign

considerations: a catastrophic failure of the space elevator system could disable not just one cabin or gondola but the entire system and it could put the future of space elevator technology as such at risk. Unlike in the case of rocket-based space exploration, the entire concept would be put in doubt. In addition will the space elevator at least in the long term aim at a mass tourism market as well, which leads to different safety expectations than one might find among professional astronauts etc. Therefore the incentive to make a space elevator work safely is even bigger than in the case of other modes of space transport.

Conflict of Laws

But the inherently international nature of a space elevator project also raises more questions. If states want to regulate space elevator operations54 and if climbers have a nationality like other spacecraft it is conceivable that at any given time several climbers might use the same tether at the same

Recognition, in: 29 Emory International Law Review (2015), pp. 637-671. 54 For an overview over the legal situation in the United States see Benjamin Hamilton Jarrell, International and Domestic Legal Issues facing Space Elevator Deployment and Operation, in: 7 Loyola Law and Technology Annual (2007), pp. 71-97, at pp. 75 et seq.


time55 (which provides specific risks56), a tether which might be owned by a corporation from another country and which might be based on a territory of yet another country, ferrying cargo and passengers from different countries to a space station operated by yet another group of countries at which a spacecraft from yet another state is docked.

It is possible to imagine different climbers, registered in different states, which share a space elevator and which could essentially be parked at either end of the space elevator. Likewise, different vessels could dock at the space end of the elevator system. Assuming that the elevator infrastructure will have been constructed and financed by a state or private corporation, an analogy to existing maritime infrastructure might be useful by comparing such a system to a canal, like the Kiel, Suez or Panama Canals. Being able to charge a fee would give the constructing entity an incentive to make the very high investment. The elevator cable could practically become a toll road to space with parking lots on either ends. Basing the base station in the high seas allows universal access to the stars. Given the high costs of a space

55 See the discussion supra fn. 49 and the literature mentioned there.

elevator system, a likely alternative is the cooperative model used in the construction and use of the International Space Station (ISS). Like in the case of space stations, though, it has to be assumed that some states, like China with the Tiangong space station, will want to go it alone – which would raise the smallest number of legal issues if it were done by an equatorial nation, such as French Guiana, Brazil or Ecuador.

Conclusions and Outlook

The growing role of private actors in space activities can even lead to privately constructed and operated space elevator systems. While many future (legal) questions might hardly be imaginable today, the basic problems can be solved with international law as it already exists today. In particular passenger liability will need some improvement and the legal status of climbers as spacecraft has to be clarified. Space Elevator Law will be a highly complex matter at the intersection of public and private international law but it is a field of law which can be navigated by lawyers. It will be necessary to have experts on space elevator law in all jurisdictions which could have a

56 Ibid.


connection with a space elevator, be it through participation in the project to a resident or citizen being a passenger on board a climber. At least with regard to the major jurisdictions which are likely to be involved early in the process of building and operating a space elevator it is therefore already possible today to attempt to research and teach space elevator law as an academic discipline which cuts across and unites existing legal fields and also deals with new questions. This is why it is possible to speak of international space elevator law not merely as a new academic discipline but as an emerging academic discipline, many parts of which already exist today.

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SPACE ELEVATOR DYNAMIC RESPONSE TO IN-TRANSIT CLIMBERS

David D. Lang David D. Lang Associates, Seattle WA.

Abstract: This presents findings of time-domain simulation studies of the space elevator using the Generalized Tethered Object Simulation System (GTOSS). Overview of mathematical models comprising GTOSS are presented. Physical configuration of the elevator as it manifests itself within GTOSS is described. GTOSS simulates climber transit by modeling chains of multiple objects and tethers, the climber being an object between two adjacent tethers, thus, climbing occurs as the earth-side tether undergoes deployment and ballast-side tether undergoes retrieval. Once an element of ribbon enters the domain of the climber, that element is no longer a participant in the free motion model of tether lying outside the climber (until it emerges). So that which is true in nature is extant within GTOSS to simulate a climber and should provide useful insight into the nature of climber design and its impact on elevator operations. The study characterizes effects on the ribbon’s transverse, longitudinal, and libration mode oscillations due to start-up, cruise transits, and motion arrest.

I. Introduction

This paper explores the dynamic response corresponding to a variety of climber operations including: initial lift-off dynamics, nominal transits, transit resumes, and transit arrests. This study attempts to identify potential problem areas, and recommend areas for further examination. In particular, this is an exploration of dynamic attributes that could lead to ribbon failure or present operational limitations. Due to lack of concrete information on climber design, such as mass tensor properties and control system strategies, climbers are simulated as 3 (rather than 6) degree of freedom rigid bodies.

I. GTOSS Overview

The Generalized Tethered Object Simulation System is a time-domain dynamics simulation code, developed by the author in 1982 to provide NASA with the capability to simulate the dynamics of combinations of space objects and tethers for flight safety certification for the Shuttle Tethered Satellite System (TSS) missions. Since then, GTOSS has undergone continuous evolution and validation, being applied at some stage in the


formulation of virtually every US tethered space experiment flown to date; more than 25 aerospace organizations have employed it. GTOSS was designed for generality, thus allowing its current use in simulating space elevator behavior. Below is an overview of its features.

• Multiple rigid bodies, with 3 or 6 degrees of freedom, connected in arbitrary fashion by multiple tethers, all subject to natural planetary environments, including sophisticated models for earth attributes as well as more rudimentary models for the other planets.

• Tethers represented by either massless or massive models. The massive tether model is a “point synthesis” approach, each tether employing a constant number of up to 500 nodes, specifiable by tether (500 being a system configurable limit).

• All tethers can be deployed from, or retrieved into, objects by means of user-definable scenarios. The deployment/retrieval dynamics model includes momentum effects of mass entering or leaving the domain of the tether itself, and produces related forces on objects deploying and retrieving the tether material.

• Tethers can be defined to have length dependent non-uniform material properties. Elastic cross section, aerodynamic cross section, and lineal mass density are independently specified for up to 15 separate regions. Properties at sub-nodal points within each region are determined by interpolation. Each region can have its own modulus of elasticity and material damping attributes.

• Tethers are subject to distributed external forces arising from the following environmental effects: Aerodynamics in the subsonic and hypersonic regime; Electrodynamics due to tether current-flow interaction with the Earth’s magnetic field using current-flow models that incorporate the earth magnetic field and effects of an insulated or bare-wire conductor interacting with the orbital plasma environment model. Note, with an appropriate ribbon-to-plasma electron contact model, this could simulate grounding-current in a conducting elevator ribbon.

• Tethers experience longitudinal thermal response. Tethers gain heat under the influence of solar radiation, earth albedo, earth infrared radiation, aerodynamics, and electrical currents; heat loss occurs through radiative dissipation.

• Tethers can be severed at multiple locations during simulation.


• Objects and tethers can be initialized in many ways, including creating stabilized extremely long tether chains, attached to and rotating with a planet (a space elevator) with due consideration for non-uniform tether properties and the concomitant longitudinally varying strain distribution of elastic tether material.

• GTOSS creates a database containing results of response to the user-defined material configuration, initialization specifications, and environmental options; this permanent data base can then be post processed to produce a wide variety of result displays, from tabular data, to graph plots, to animations.

II. Climber Simulation Rationale

Construction and operational payload climbers traversing the ribbon will excite transverse and longitudinal string mode responses and elevator libration motion (the simple pendulum-like motion of the elevator about its anchor point). Such responses will reflect all the potentially non-linear effects related to tapered ribbon design, inverse-square gravity field, centrifugal forces, Coriolis effects, atmospheric disturbance, and climber speed modulation.

GTOSS possesses the ability to simulate a climber’s transit of the ribbon by modeling chains of multiple objects and tethers. The climber would be an object in a chain with two adjacent tethers, the earth-side tether undergoing appropriate deployment, while the ballast-side tether undergoes complimentary retrieval (for upward climbing). An argument in behalf of this approach starts with the fact that once an element of ribbon enters the "domain of the climber" (ie. gets clenched-in and/or threaded-through rollers, etc.), and until it emerges, that element is within the domain of the climber itself, thus, not a participant in the free dynamic motion of the ribbon lying outside the climber. Such a state of affairs appears to meet all the pertinent criteria for application of a tether deployment/retrieval simulation. So that which is true in nature is extant within GTOSS to simulate climber action. In further affirmation of this viewpoint, note that ribbon strain distribution internal to the climber will, in general, be unlike that of adjacent external ribbon because unique strain states can be imposed upon the ribbon within the climber mechanism; indeed, exceeding limit-strain within the climber may be a factor in climber traction designs that engage the ribbon through overlapping roller schemes to take advantage of capstan effects. Intuitive reasoning opposed to the above climber simulation rationale’ and based on a priori


knowledge of ribbon continuity must be tempered by the fact that as far as external ribbon dynamics are concerned, there could just as well be a recycling plant within the climber ingesting ribbon from above, re-synthesizing it to make a new ribbon, and deploying it out the bottom.

For climber studies, the GTOSS configuration consists of a climber containing two reels of ribbon, both of which characterize the ribbon’s dual taper design. Earth-side deployment occurs such that the earth-end taper would emerge first, while for the upward deployed ribbon, the ballast-end would emerge first. In this way, no matter where the climber is positioned, the ribbon below and above properly portray the total earth-to-ballast profile.

Conventionally, deployment conjures up images of a reel positioned at altitude, with ribbon being dropped down; that is not what is occurring during climber operations. To clarify, consider two points, P1 and P2, between which ribbon is to be dispensed. Two distinct processes can accomplish this, process A and B. In process A, the reel is positioned at P2 remaining stationed there with the ribbon spooled-off and dragged to P1. In process B, the reel starts at P1, and is then transported to point P2, with ribbon being laid-down between P1 and P2. These are dynamically distinct processes, in that if observed from a location fixed between P1 and P2, the following would be noted: in process A, there would be a continuous parade of different ribbon particles traversing by, while for process B, a single particle of ribbon would appear at the observation point, and remain there throughout the deployment. Process B is realized by GTOSS climber simulation both above and below the climber.

III. GTOSS Space Elevator Physical Properties

By using appropriate definitions of tether properties above and below the interior climber-object, GTOSS is made to reflect the design profile properties along the entire elevator. Conveniently, since each finite tether model can have independent properties, assigning a different number of nodes to each tether can provide dissimilar nodal resolutions at different regions of ribbon if desired.

Ribbon characteristics vary with length, and are comprised of: density, elastic-area, modulus, aerodynamic-area, and damping, all corresponding to baseline ribbon design as described in References 1 and 2. The ballast mass is 634,000 kg at a radius of 100,000 km. The climber mass corresponds to the nominal 20 ton design; attributes for inertia tensor, control effectors, etc., are currently un-defined, so the climber is simulated


with 3 (rather than 6) degrees of freedom. The elevator’s tapered ribbon is initialized by GTOSS to a stabilized vertical state with ribbon strain distribution in equilibrium with gravity, centrifugal, and attached climber loads. The dual tapered ribbon is designed to achieve, over its entire length, a uniform stress distribution of about half of the 120 giga Pascal capability anticipated for operations. GTOSS confirms this as shown by the unloaded ribbon’s stress profile in Figure 1.

Figure 1. Ribbon Stress vs Altitude

This uniform stress results from GTOSS simulation of the interplay between planetary environments and the ribbon’s tapered cross sectional profile, modulus, and density (shown in Figures 2 and 3). The slight droop in the stress curve near the earth can be attributed to approximation errors associated with curve-fitting the ribbon profile’s taper gradient near the earth.


Figure 2. Ribbon Elastic Cross Sectional Area vs Altitude

Based on elastic cross sectional area profile and a nominal value of ribbon material’s bulk density of 1.3 gm/cm3 (CNT), the lineal density profile shown in Figure 3 was derived for use in GTOSS.

Figure 3. Ribbon Density vs Altitude


IV. Case Definitions and Simulation Results:

Unless otherwise specified, the following definitions apply:

(a). Nominal climber Transit speed is 200 km/hr.

(b). Nominal Lift-off or Transit-resume is defined as a one hour duration linear ramp-up from zero to nominal transit speed.

(c). Nominal Arrest is defined as a one hour duration linear ramp-down from nominal transit speed to zero.

(d). Sudden Arrest is a step change from transit speed to zero speed.

All Transit and Arrest cases start with a stable transit in progress. All Liftoff or Transit-resume cases start with zero rate.

Case 1: Nominal Payload Liftoff from Ground (1 hr ramp-up).

Case 2: Limit Payload Liftoff from Ground (1 hr ramp-up).

Case 3: Transit Resume from GEO (1 hr ramp-up).

Case 4: Nominal Transit to Ballast (200 km/hr).

Case 5: Fast Transit to Ballast (400 km/hr).

Case 6: Nominal Transit to GEO (200 km/hr).

Case 7: Sudden Arrest at 2 km (zero ramp-down time).

Case 8: Modulated Arrest at 2 km (60 sec ramp-down time).

Case 1: Nominal Liftoff from Ground (1 hour ramp up).

This case shows the mechanism by which nominal climber liftoff can occur. A 20 ton climber weighing 178,035 N on the launch pad will experience a ribbon tension from above of 197,000 N and from below of 19,700 N. Before liftoff, the climber net weight (gravity less centrifugal force) is in equilibrium with this tension differential across the climber. While this tension differential allows practical liftoff acceleration to occur, it also represents the maximum possible liftoff acceleration. The mechanism by which the tension in the lower ribbon is exploited for liftoff consists of the climber’s transporting ribbon from above itself to below. An element of ribbon length, when transported from the domain of the upper ribbon has very little effect upon the strain in the upper ribbon due to that ribbon’s extreme length, thus tension is correspondingly affected but little due to the low effective spring rate of the upper ribbon. On the other hand, that same


parcel of ribbon, when introduced into the domain of the lower ribbon, has a profound effect upon its strain state due to the lower ribbon’s short length, thus, a correspondingly greater effect upon the lower tension due to the lower ribbon’s high spring rate. Transport of ribbon from above to below, can cause an immediate and significant drop in lower ribbon tension; this in turn creates an imbalance on the climber accelerating it upwards. Once the lower ribbon becomes slack, then the maximum possible immediately available force imbalance on the climber will have been realized. Any additional acceleration can only come from increasing strain in the upper ribbon. Figure 4 depicts a nominal liftoff.

Figure 4. Climber Liftoff vs Time

As seen in Figure 4, tension at the ground dips down initially as the climber starts transporting upper ribbon into the lower ribbon domain. This tension


drop, that can be easily and quickly induced, provides the initial upward force imbalance that starts the climber in motion. In spite of upper ribbon continuing to flow into the lower domain, the lower tension starts to increase due to upward climber motion continually separating the lower ribbon attach points, thus tending to neutralize strain reduction that caused the tension to drop initially, as shown in Figure 5.

Figure 5. Average Strain in Lower Ribbon vs Time

During the liftoff acceleration period, the upper ribbon is very slowly acquiring a tension increase due to the strain increase brought about by the climber’s continual removal of ribbon from the upper domain; also at work is the general gravity/centrifugal effect that brings about the characteristic concave- down tension-versus-altitude profile of the elevator. The oscillations seen in these figures is associated with the fact that the liftoff scenario employed was not designed to control longitudinal oscillations. Since the end-to-end ribbon transmission time for a stress disturbance is about an hour, with the first longitudinal mode having a period of about 2 hours, it is evident that stress disturbances, once initiated, will periodically manifest themselves at the site of the initial disturbance and longitudinal oscillations will exhibit (2 hr) periodicity.

Upper and lower ribbon climber tensions are compared in figure 6 below. It is seen that upper tension also drops initially, with both tensions following a similar profile in time. The initial drop in upper tension is because the climber starts accelerating upward under the force imbalance due the immediate reduction of lower tension. Even though the climber is transporting equal increments of ribbon length from the upper into the


lower domain, such increments aren’t nearly as effective in increasing tension above as it is in lowering tension below. Both tensions, continue to rise and converge, finally peaking and coalescing to a zero differential at GEO.

Figure 6. Upper and Lower Tension at the Climber vs Time

Figure 7 shows tension observed at 50 km altitude on the ribbon. The discontinuous change at 0.75 hours is where the climber passes 50 km point.

Figure 7. Tension at 50 km Altitude vs Time


The climber itself progresses up the ribbon with only slight westward horizontal displacement as shown as libration angle relative to local vertical in Figure 8. This libration is due to Coriolis effects, and its steady diminishing is likely attributable to geometry of increasing altitude combined with steady tension increase (above and below) that provides some restoring stiffness against horizontal displacement.

Figure 8. Climber Libration vs Time

Case 2: Limit Payload Liftoff from Ground.

This explores repercussions of attempting climber launch at the maximum weight the elevator can support, a situation in which the lower ribbon has essentially zero initial tension. Unlike Case 1, the only means to effect liftoff in this situation is to “climb” the upper ribbon, a process equivalent to increasing upper ribbon tension alone to effect liftoff and subsequent transit velocity.

Figure 9 shows a set of related liftoff parameters (note, a somewhat different set of parameters are presented than shown in Figure 4.)


Figure 9. Liftoff Parameters vs Time

Since the lower ribbon tension is initially near zero, the process of transferring ribbon into the lower domain to effect a tension differential is no longer effective; only increasing strain in the upper ribbon will act to effect liftoff. This is clearly not an operationally feasible scheme, since it operates the elevator at a transiently unstable load condition capable of pulling down the ballast.


The lower ribbon is observed to go slack for about 1.5 hours; by the time ribbon transfer-rate has ramped to its nominal value, the climber has deposited 40 km of slack ribbon on the ground. Albeit an inefficient means of creating tension differential, removing this amount of ribbon from the upper domain has increased upper tension to eventually accelerate the climber to an altitude equal to the amount of slack ribbon below; this increase is not obvious at the tension scale in Figure 9. At the point climber altitude matches the (heretofore slack) ribbon length below, a severe impact event occurs creating a longitudinal strain disturbance seen to manifest itself on the order of every 2 hours at the climber, consistent with the round-trip stress wave propagation time to the ballast. At first impact, altitude rate is twice nominal transit rate. The climber quickly acquires nominal rate after impact transients subside, as shown in Figure 10.

Figure 10. Climber Altitude Rate vs Time

Figure 11 shows snapshots of the impact disturbance at various times as it progresses along the ribbon.


Figure 11. Tension Snapshots vs Altitude along Ribbon

Note, the climber progresses up the ribbon less than 1% of the total ribbon length during the 4 hours of simulated time.

This case clearly exhibits the fact that creation of immediate and significant climber acceleration cannot exceed a level corresponding to a force equal to the initial tension at the climber interface with the lower ribbon; in fact, smooth and timely liftoff operation depends upon this initial lower tension. Thus, once a design acceleration is specified, then maximum liftoff mass of the climber is determined. This will likely not constitute a significant operational constraint since the time to accelerate to nominal transit speed is likely not a critical design parameter provided a reasonable level is possible, and it seems that it is.

Case 3: Transit Resume from GEO (1 hour ramp-up).

This case examines a climber resuming to nominal transit speed from a parked position at GEO. Starting from 35,400 km altitude, the climber ribbon rate ramps up to nominal over a period of one hour. Figure 12 shows


the resulting altitude and climb rate response, and indicates that a resume to transit speed is feasible from GEO.

Figure 12. Climber Altitude and Rate vs Time

This situation presents a different situation than liftoff from ground. The mechanism that creates altitude rate, while intrinsically the same at ground or GEO, is not as immediate or as effective at GEO. It is apparent, from the periodic oscillations in the altitude rate, that the climber is interacting with the ribbon’s first longitudinal natural mode. In equilibrium at GEO, before a transit resume, the climber would have the same tension above as below. Ribbon is still transferred from above to below to create a tension differential, but it is unlike ground liftoff where upper ribbon being transferred to the lower ribbon causes an immediate and significant tension drop below but little tension increase above. At GEO, this ribbon transport process has nearly equal effectiveness above and below for creating tension change. Figure 13 shows upper and lower tensions at the climber. Meaning can be extracted from this apparent meandering behavior if the differential in these two tensions are examined.


Figure 13. Tension Above and Below Climber vs Time

This tension differential, shown in Figure 14, represents the forcing function that creates vertical climber acceleration. During the initial 1 hour ramp- up of ribbon transfer-rate, the net vertical tension differential is increasing to accelerate the climber.

Figure 14. Tension Differential Across Climber vs Time

At one hour, ribbon transfer rate has arisen to the constant nominal transit speed and at that point an oscillation manifests itself in the differential tension, with a period characteristic of the first longitudinal mode of the ribbon. The ribbon transfer scenario used in this study has made no attempt to minimize coupling with the first longitudinal mode, as may be possible


with proper climber design. Unlike transverse string modes, longitudinal modes inherently induce strain rate, thus might be effectively controlled with internal material damping.

Case 4: Nominal Transit to Ballast at 200 km/hr.

Figure 15 presents an overview of a 200 km/hr transit of essentially the entire length of the elevator from 2,000 to 98,000 km.

Figure 15. 2,000 to 98,000 km Climber Transit @ 200 km/hr vs Time

The characteristic oscillations in the altitude rate starting at about 450 hours represents the longitudinal response of the climber-ribbon combination to a linear ramp-down transit arrest. This is an artifact of the


arbitrary arrest scenario used in this study, and likely would be suppressed with a well designed climber-arrest control strategy. The elevator’s 5 day in-plane (east-west) libration period manifests itself throughout transit indicating a progressively westward retrograde bias under the influence of Coriolis effects on the climber until climber transit arrest; then, starting from the arrest state-conditions, a new phase of libration develops, symmetrical about the vertical. So the net overall effect on the elevator as a whole, due to this particular full length climber transit and arrest, is to have induced a net libration of about +/- 0.55 degrees.

The resulting libration appears to be dependent upon when the arrest actually occurs. From examination of figure 15, up until arrest occurs at 450 hours, the developing libration oscillation has points of zero libration rate; if arrest completes at a zero libration-rate-point, the resulting libration of the elevator simply acquires the corresponding amplitude as its initial condition (and maximum amplitude). Thus based on time-of-arrest for this transit, it appears that a net libration between +/- 0.3 and +/- 0.65 degrees could have resulted.

Figure 16 shows climber altitude rate oscillations at arrest, using a magnified time scale to expose an approximately 6 hour period of oscillation. The climber, since it arrests very near the ballast mass, excites the ballast’s longitudinal bobbing mode; due to the dominating ballast mass, this mode can be visualized as a one degree-of-freedom spring-mass system comprising the ballast mass and an effective end-to-end ribbon spring rate of 0.04 N/m. The smaller periodic irregularities are likely related to longitudinal-mode interaction with the climber mass now parked very near the ballast.

Figure 16. Climber Altitude Rate after Arrest vs Time


Compared to gross elevator libration, the climber is producing insignificant transverse string-mode displacements as seen in Figure 17 depicting snapshots taken throughout the 28 days of simulated time. Here, each snapshot simply appears as a straight line.

Figure 17. Ribbon Snapshot Envelope vs Distance along Ribbon


Figure 18. Ribbon Displacement Snapshot vs Distance along Ribbon

Figure 18 depicts a shape snapshot with greatly magnified horizontal scale showing transverse displacement at 2 days into the transit (10,000 km). Though appearing as a solid line, this snapshot consists of dots, each being a nodal point. At the time of this snapshot, nodal density is far greater between the climber and ground than between climber and ballast; by the end of the transit, just the opposite will be true. Figure 19 shows that normal climbing produces virtually no over-stress. At 450 hrs, arrest maneuver stress oscillations are seen.


Figure 19. Ribbon Stress Profile vs Distance along Ribbon

Case 5: Fast Transit to Ballast at 400 km/hr.

Figure 20 presents an overview of a 400 km/hr transit of essentially the entire length of the elevator from 2,000 to 98,000 km.

Figure 20. 2,000 to 98,000 km Climber Transit @ 400 km/hr vs Time


It is notable that this particular 400 km/hr transit induced libration angle about twice that of the 200 km/hr transit. However, unlike the previous 200 km/hr case, it appears that this arrest occurs at a more advantageous libration state; had arrest occurred at the most inopportune time, then up to +/- 1.3 degrees of libration may have resulted. The general effect of increasing transit rate appears to be an increase in westward bias, or slope of the average libration angle while under transit rate; peak-to-peak libration excursions during transit are more or less invariant at about 0.3 degree. This mean that regardless of optimal arrest timing, faster transits will always result in more residual elevator libration.

An interesting effect is seen in the transit-arrest disturbance induced at 98,000 km as it propagates to lower altitudes on the ribbon. Figure 21 is a stress time history at 5,000 km and 50,000 km altitude, indicating a disturbance magnification factor of three. Under close examination, this disturbance is found to consist of; stress waves being propagated up and down the ribbon, bobbing mode response of the ballast, and excited longitudinal modes. This magnification might be attributable to two effects, (a) an increase in tension level as the strain energy encounters

Figure 21. Ribbon Stress at 2 Altitudes vs Time

ribbon of smaller elastic cross section (similar to the increase in ocean wave height as wave energy encounters narrowing land-constraints), (b)


for a given disturbance tension level, an increase in stress due to smaller elastic cross section of the ribbon.

Case 6: Nominal Transit to GEO at 200 km/hr.

Figure 22 presents libration response of a 200 km/hr transit from 2,000 km to GEO altitude (35,400 km); note, general response was typical of the other transits. It may be possible to modulate transit rate to arrive at GEO arrest with near zero libration (note “Region of interest” above), a fact that could have benefit for elevator operations. Note that the act of climbing induces transverse vibrations of the ribbon as shown in figure 23 that depicts a snapshot of ribbon displacement just before GEO arrest. From figure 23, it can be concluded that by the time the climber nears arrival at GEO, about 10 km of transverse string displacement has been induced; this corresponds to about 0.002 deg deflection (as viewed from ground). Given that gross elevator libration at this point is on the order of 0.1 degrees, this transverse deflection does not appear to be operationally significant at this transit speed. Transverse string response can translate into equivalent librations since, like libration, it is a manifestation of momentum disturbance in the horizontal direction. Note also that the restorative effects of ribbon tension toward keeping the climber aligned between anchor and ballast are operationally insignificant due to the very small angles that the ribbon makes with the line-of-sight between ballast and anchor (note axis scaling in figure 23).

Figure 22. Elevator Libration vs Time


Figure 23. Ribbon snapshot: Total Displacement from Vertical vs Altitude

Case 7: Sudden Arrest at 2 km.

This case examines response of a climber at full transit speed of 200 km/hr experiencing a sudden arrest. Starting at 1 km, the climber maintains full speed for 18 sec until, at which point, ribbon transport rate becomes instantly zero at 2 km altitude. Figure 24 shows the response.


Figure 24. Climber Altitude and Altitude Rate vs Time

The response is characterized by the climber first engaging against the stiff spring of the lower ribbon and being catapulted back downward in reverse to immediately put the lower ribbon in a state of slack; this is followed by a slower rebound upward under the influence of the softer spring of the upper ribbon; these two processes then cyclically repeat while attenuating due to damping. The difference in upper and lower spring rates is clearly seen in the altitude rate graph above. Figure 25 shows tension history at two ribbon points. Tension at 1.5 km exhibits load spikes characteristic of impact loading. Note that at 20,000 km, the ribbon does not experience this transient until almost 10 minutes after the sudden arrest has occurred below it on the ribbon.


Figure 25. Ribbon Tension at 1.5 km and 21,000 km vs Time

Figure 26 shows a magnified display of details of the initial impact.

Figure 26. Ribbon Tension at 1.5 km Altitude vs Time

While this response is certainly not desirable, Figure 27 shows why it could be disastrous. It is apparent from this stress time history, that the design


strength of the ribbon, including the factor-of-safety of 2, is seriously threatened by the sudden arrest load.

Figure 27. Ribbon Stress at 1.5 km Altitude vs Time

This is good reason for climber mechanism design and liftoff speed modulation scenarios to eliminate possibility of such an event.

Case 8: Modulated Arrest at 2 km.

This case is identical to Case 7, except, a gentler 60 sec ramp down to zero rate is employed. Figure 28 shows the response to such an arrest.


Figure 28. Climber Altitude and Altitude Rate vs Time

The resulting stress time history at 1.5 km, is shown in Figure 29; compare this with Figure 27.

Figure 29. Stress @ 1.5 km vs Time

There are many possible arrest scenarios to optimize aspects of climber operations; the above arrest is arbitrary, primarily illustrating that practical scenarios can be easily designed to bring about transit arrest in a reasonable time, even at low altitude, without threatening the ribbon strength.


V. Conclusions

The major operational effect of a climber transit is seen to be due to the Coriolis dynamics as the climber ascends. The residual libration resulting from a transit appears to be a function of both the speed and distance of the transit, as well as when the transit arrest occurs relative to the libration cycle being induced throughout the transit. As a rule, faster transit causes greater libration.

This study points out the potential effects of simultaneous climber interactions with both a very low effective end-to-end spring-rate of an elevator ribbon of full length, and the high spring rates associated with shorter ribbon sections extant near the ground at liftoff. This manifests itself in a variety of elevator climbing operations, but most dramatically in the process of both accelerating and decelerating a climber on the ribbon, especially in near-ground operations such as liftoff. The longitudinal string modes of vibration were found to be easily excited under climber acceleration or deceleration. Bobbing mode frequencies of the ballast mass, as well as climber mass can manifest themselves in response to climber activity. Stress wave propagation effects are also seen to manifest themselves.

VI. Future Work

Many areas of new investigation regarding climber transit were identified, but left unaddressed by this preliminary study. Noting that passive (i.e., non- horizontal-thrusting) transits leave a residual libration artifact in the elevator, there may be significant issues concerning how these artifacts will accumulate or be controlled over successive transits during long term operations. Will it be possible to plan transit launch phasing to minimize residual levels of libration without undesirable impact on transit schedules? Can transit speed modulation and arrest timing be used effectively to minimize resulting libration? If elevator traffic models were to include a (roundtrip) shuttling schedule between earth and LEO, then how might these trips be phased to take advantage of the reverse-Coriolis effect on the way down in order to control residual libration of the elevator? What is an acceptable level of libration? What are optimal lift-off scenarios? Rigid body response of climbers interacting with: atmospheric loads, ribbon string modes, and elevator libration may have impact on beamed-power system design, and should be addressed.


Acknowledgements

Funding for this work has been provided by the Institute for Scientific Research, Fairmont, WA.

This paper was first presented at the First International Conference and Exposition on Access, Habitation, Exploration, Business and Science in Space

April 3-7, 2005 - Albuquerque, New Mexico

References Edwards, Bradley C., Westling, Eric A. “The Space Elevator”, published by Spageo Inc, San Francisco, CA, 2002.

Edwards, Bradley C., unpublished communications with the author.

Pearson, Jerome, “The Orbital Tower: a Spacecraft Launcher Using the Earth’s Rotational Energy”, Acta Astronautica. Vol. 2. pp. 785-799


THE SPACE ELEVATOR IN THE EARTH’S ATMOSPHERE

John M. Knapman ISEC, Director of Research

Abstract: Three designs have been proposed for that part of the space elevator that is within the atmosphere; they are “Spring Forward,” “Box Protection” and “High Stage One.” The paper examines in more detail than before how these designs can operate and what the advantages are. Spring Forward involves pulling the tether down so that its elasticity can lift the weight of a tether climber. This will cause longitudinal waves to propagate along the tether, and an appropriate wavelength must be selected and controlled. Box Protection adds to the tether climber’s weight and hence places an additional load on the whole of the tether, but it allows the part of the tether in the atmosphere to be designed to minimize wind forces. High Stage One is unproven, although it is based on established technology. It eliminates the need for any part of the tether to be in the atmosphere. Some recent prototyping work has been done.

Nomenclature A = area of cross section of tether E = Young’s modulus (modulus of elasticity) of tether F = lateral force on tether L = effective length of tether when considering elastic stretching l = increase in length t = time v = velocity of propagation x = displacement along tether ξ = change in displacement ρ = mass density of tether material

I. Introduction

Rocket launches can be scheduled for good weather, but the space elevator should provide a regular daily service. Tether climbers need to depart at regular times so that the load on the tether is within constraints. If a launch is delayed by three hours, for example, the next days’ launch must also be delayed by the same amount or more. When using solar cells for power, the hours of daylight are an additional constraint.


As a tether climber passes through the atmosphere, it is subject to the usual hazards of wind and ice. The solar panels will need to be stowed and protected. The receivers for laser power will be smaller but will still need protection.

The tether itself is also subject to atmospheric phenomena, and it has to endure all weathers. It is reasonable to cancel the launch of a climber in extreme weather, but the tether is a permanent part of the infrastructure. A tether design specific to the atmosphere is needed, much narrower than the 1 meter width that is appropriate for avoiding space debris and meteors. Edwards and Westling propose a width of 20 cm in the atmosphere, but a much narrower shape would be better to minimize wind impact.1

This subject has been treated in previous talks and publications, but more detail is presented here.2

II. Spring Forward

When the time is close for launching a tether climber, the concept is to pull the tether down so as to utilize the natural elasticity of the tether material. Assuming the climber uses solar power above the atmosphere, launch preparations would begin a couple of hours before dawn.

The tether above the atmosphere is a meter wide but only 8 to 70 microns thick, depending on altitude. The tether must remain attached to the Earth’s surface in order to launch a climber and also to ensure that the climber receives the benefit of the Earth’s rotation. However, within the atmosphere the tether will be subject to atmospheric effects, principally wind and ice. The optimum shape for the atmospheric part of the tether is close to a circular cross section, like a rope. This is the shape that minimizes the surface area and thus minimizes the loading due to both wind and ice.

We call the part of the tether that is always in the atmosphere the auxiliary tether. The rest of the tether is the main tether. The main tether only has to be in the atmosphere while it is being pulled down and released. The tether climbers’ drive mechanism is designed for the main tether, which is thin and a meter wide. When using Spring Forward, the climbers do not have to climb the auxiliary tether.


Figure 1. Raising a climber above the atmosphere using Spring Forward.

When preparing for a climber launch at the marine node, machinery pulls in the auxiliary tether to draw down the main tether (Figure 1), which becomes exposed to wind and ice risks until it is restored to its normal altitude. This is the time of greatest hazard, since the winds in the stratosphere are often very strong. The auxiliary tether has to take the full tension of the main tether, which must be sufficient to support the weight of the climber, plus the additional force needed to stretch the tether. When the marine node releases the tether, this stretching force provides lift to accelerate the climber.

A first-order analysis is as follows. Consider the tether up as far as the geosynchronous node (GEO). We don’t look beyond GEO, as the GEO node is likely to be quite massive and so will not move much. The tether length from Earth to GEO is about 36,000 km. Suppose the marine node pulls it by 40 km. The extra force required to do this is given by

≅ 10 9 1040

36000≅ 10000 1


That is, a force of approximately 10 kN is required to stretch the tether. Here, ≅ 10 Pa is Young’s modulus (the modulus of elasticity) of carbon nanotubesi and ≅ 9 10 mm2 is the tether’s area of cross section.

A force of 10 kN will accelerate a 20-tonii climber by 0.5 m/sec2. The force reduces linearly to zero as the tether’s extension reduces from 40 km to zero. Hence, the average acceleration is 0.25 m/sec2, and the climber reaches 40 km altitude after about 560 seconds. Allowing for a controlled deceleration, this amounts to about 10 minutes climbing time.

However, the situation is rather more complicated, because there will be other climbers at various points on the tether. If we assume the constant power method of operating, in which climbers consume a maximum power of 4 MW using only solar arrays, there will be another climber at about 1500 km altitude, the exact position depending on seasonal variations. In addition, there is a propagation delay between starting a movement at the base and its effect reaching various heights.

It is easiest to start by considering a uniform tether. The extension is subject to d’Alembert’s equation

2

Here, is the displacement of the tether, along the length of the tether, from a steady-state position at time . is Young’s modulus of the tether material, and is its mass density. The general solution is of the form:

3

and Q are constants. The functions and are determined by the movement at the bottom of the tether. We can control these functions by the way we pull the tether. The waves travel at velocity up the tether, where is given by:

4

i Gilberto Brambilla, personal communication ii For “ton” read “metric ton” throughout.


For carbon nanotubes, we can take the density as 1.3 times that of wateri. Then the velocity of wave propagation is approximately 28 km/sec or 100,000 km/hr. If a tether climber is resting overnight at an altitude of 1500 km, this means that a pull on the tether from the surface will reach it in 54 sec. For the effect to reach GEO at 36,000 km takes about 22 minutes.

Of course, the tether is not uniform, since the cross section increases with height. The applicable equation now is

5

This equation is difficult to solve analytically, but we can say that, at 1500 km, the area of cross section is double that at the base, allowing for the extra tapering to support the weight of the climber at 1500 km3. Using

⁄ (Equation (1)) we can calculate the extra tension needed to move the tether climber downwards. The increase in tension in the tether will cause different parts of the tether to extend by different amounts, depending on the cross section, which increases with height. Using a spreadsheet, we can calculate the movements at all altitudes to GEO and calculate that the tension increase needed to move the tether base down by 40 km is 34.2 kN. This is equivalent to adding 3.5 tons to the weight on the base of the tether.

Climber Altitude (km)

Movement (km)

Propagation delay (min)

1,500 32 1 4,600 26 3

10,600 19 6 17,100 13 10 23,800 8 14 30,600 3.5 18

Table 1. Tether extensions and propagation delays at various altitudes.

Table 1 shows all the climbers below GEO and how much they move as a result of pulling the tether down with this force of 3.5 tons. The climbers’ positions are those reached using propulsion at constant power (strictly speaking – max power, max speed)3.


In summary, 34.2 kN is the force needed, and so this is the force that must be provided by the marine node’s machinery. To avoid putting undue strain on any part of the tether, the speed of movement must allow for the propagation time, gradually increasing the tension over a period of about an hour until the base has reached the required 40 km of extension. Releasing the tether with the climber duly loaded on it must also be a carefully controlled operation over about an hour, gradually relaxing the tension in the auxiliary tether until the climbers are restored close to their proper positions.

A. Effect of Winds on the Tether

Bearing in mind the delicate application of tension required to ensure careful coordination of the tether’s extension in concert with the movements of the climbers, it is salutary to consider the effect of winds. The parts of the tether that are in the atmosphere will be subject to winds which are unpredictable and variable. During an operation to launch a tether climber, the main tether is lowered into the atmosphere and spends up to two hours there. Previous calculations have shown the maximum wind pressure that may be encountered in the upper atmosphere is on the order of 1 kPa. This means that a 1-meter-wide tether, curved to present a 50 cm cross section, could encounter a total lateral force as high as 3000 kN when summed over its length at all altitudes, taking into account the differing wind pressures at different altitudes (Figure 2)4.


Figure 2. Maximum wind pressure at various altitudes.

However, whereas the auxiliary tether must withstand freak or exceptional conditions, it is reasonable to assume that the operators would cancel a scheduled launch if the wind is more than double the average speed. This would probably mean losing only a few days in a year. Since the wind pressure is proportional to the wind speed squared, that brings the maximum expected wind pressure down to 250 Pa, giving a maximum force on the tether, accumulated over its length in the atmosphere, of 740 kN.

The effect of lateral forces on a tether is to move it sideways until its tension increases sufficiently to overcome the forces, according to Newton’s third law: action and reaction are equal and opposite. As pointed out elsewhere, if we allow a maximum tether swing of 10° from the vertical, the lateral force increases the tension by an amount equal to sin 10°⁄ ≅5.8 .4 Thus, a lateral force of 740 kN leads to an increase of tension equal to 4300 kN, equivalent to 438 tons extra tension. To this must be added the force on the climber (see Section III).

These forces dwarf the delicate movements required for Spring Forward. They also swamp the moderate 5-ton forces needed to deflect the tether


when maneuvering to avoid space debris. This seriously calls into question the viability of Spring Forward.

III. Box Protection

Box Protection was first devised as a way of protecting the delicate solar panels proposed for powering tether climbers. The solar panels must be very light in weight so as to fit into the climber’s mass budget. 4 MW is required to power a climber of 20 tons using the constant power method. This power must be delivered from panels weighing less than 2 tons. The present state of the art is about a factor of three short of that needed, and it is reasonable to project that level of improvement over the next few years, given the enormous investment in R&D on this topic5.

The space elevator’s unique mode of operation also requires a strong enough structure to support the solar panels under full gravity when they are deployed just above the atmosphere. This contrasts with the normal usage in space, where a spacecraft reaches microgravity before it deploys them. This means that the supports on the tether climber must be quite strong, but even so, the wind forces would still be too great without protection.

The estimated surface area of solar panels required is 66,000 m2, and the wind force on them in the stratosphere could be as high as 66 MN, equivalent to a force of 6700 tons. It is therefore quite clear that the panels must be stowed inside a protector with a relatively small surface area. The same applies in Spring Forward as in Box Protection.

The proposed shape and size of a climber is a cylinder 20 meters in diameter by 15 meters high5. To this we add an estimate of another 5 meters in height to hold the deployable solar panels. This presents an effective surface area to the wind of 400 m2, giving a maximum force in the stratosphere of 400 kN. However, whereas the tether must withstand freak or exceptional conditions, it is reasonable to assume that the operators would cancel a scheduled launch if the wind is more than double the average speed. That brings the maximum expected wind pressure down to 250 Pa, giving a maximum force on a climber of 100 kN, equivalent to 10 tons, which the tether has to absorb. Again, the formula of sin 10°⁄ ≅ 5.8 leads to an increase in tension, this time amounting to 580 kN, equivalent to 59 tons force. The tether has to support this tension throughout its length.


The tether climber is acting rather like a sail. So large is the force on it that we would probably want to consider making the tether climber smaller to avoid the effects, as otherwise it will triple the overall load that would have to be carried by the whole space-elevator tether all the way to the Apex Anchor.

A. Effect of Winds on the Tether

The tether itself is also subject to wind forces. This can be minimized – but not eliminated – by using a cylindrical shape (i.e., like a rope rather than a ribbon) in the atmosphere, similar but not identical to the auxiliary tether proposed for Spring Forward. The advantage of Box Protection over Spring Forward is that it is never necessary to lower the main tether into the atmosphere with Box Protection. The drawback is that a different climber mechanism is needed as part of the Box Protection to cope with the differently shaped tether in the atmosphere. This probably adds about 2 tons to the weight, and hence adds to the load on the tether, which increases the required mass of the whole tether. However, it significantly reduces the wind effects on the tether.

Call the part of the tether in the atmosphere the atmospheric tether (Figure 3). The atmospheric tether has to endure the full force of the wind in all conditions. The ideal shape of the atmospheric tether could reduce the effective surface width presented to the wind to as little as 4 mm. Then the expected maximum wind force on the atmospheric tether is only about 24 kN. Using sin 10°⁄ ≅ 5.8 , as before, this leads to an increase of tension equal to 139 kN, equivalent to 14 tons weight.


Figure 3. Raising a climber above the atmosphere using Box Protection.

Devising a suitable drive mechanism to gain sufficient traction to lift an augmented climber on such a slender atmospheric tether presents a significant engineering challenge. The narrow tether would probably cut through many conventional wheels like a cheese knife. A safer assumption is to take a width of 4 cm curved to present an effective width of 2 cm. Then it encounters an expected maximum wind force of 120 kN, leading to an increase of tension equal to 700 kN or 71 tons weight.

Source of load Tons Tension due to wind on atmospheric tether

71

Weight of climbing mechanism in atmosphere

2

Tension due to wind on tether climber 59

Total load added by Box Protection method

132

Table 2. Increase in tether load in Box Protection.


The tether climber also has to absorb wind forces which add another 580 kN tension to the tether, equivalent to 59 tons weight.

In summary, the net effect of atmospheric forces when using Box Protection is to increase the tether load by 132 tons (Table 2). Halving the tether climber’s diameter to 10 meters to present half the area to the wind could bring the total down to an increase in tether load of 102 tons, but this would limit the overall carrying capacity to 1 √2⁄ ≅ 0.7 times the volume. Customers would be constrained to designing their payloads to fit into this smaller space. Even with this restriction, the tether has to be strong enough to hold a 20-ton climber plus more than 100 tons due to wind forces.

IV. High Stage One

High Stage One absorbs the forces due to the atmosphere without affecting the tether. The relatively delicate movements needed to deflect the tether when avoiding space debris are carried out at an altitude of 40 km or more – above most of the atmosphere – rather than being swamped by strong forces lower down. The delicate solar panels can be deployed at the time the tether climber commences its ascent, avoiding the need to lift their deployment mechanism. The atmospheric buffeting of the climber itself is also absorbed by High Stage One.

High Stage One is useful whether employing solar power or laser power transmitters. Lasers can be positioned at an intermediate altitude, say 20 km, where the beam dispersion due to the atmosphere is much less than at sea level. At that altitude, they are still separated from the tether by a horizontal distance of 30 km or so.

High Stage One is an adaptation of the Lofstrom Loop (or Launch Loop)6. That was designed for direct launch of vehicles to orbit, but it introduced the idea of a high-altitude structure supported by deflecting the momentum vectors of objects, called rotors, traveling inside evacuated tubes using magnetic levitation to minimize friction. Mathematical analysis and computer simulation have been undertaken on a smaller version called the space cable. Particularly important is the method of stabilizing the structure in the presence of gusting winds, which is called active curvature control7. This technique expends a minimal amount of energy by constraining the natural bending to maintain equilibrium, rather than trying to impose rigidity or enforce movements.


Using this technology, it is possible to support a platform weighing several thousand tons, if necessary, at an altitude as high as 100 km. The proposed height for the platform is between 40 and 50 km. 50 km is the boundary between the stratosphere and the mesosphere. The tether is anchored to the platform, and it is the place where we transfer payload to the tether climbers before they commence their ascent4. A separate system transfers payloads and equipment between the platform and the surface. It operates like a mountain railway or funicular, using the tubes as a track.

A staged development plan for High Stage One is proposed, gradually increasing the height attained, starting with an indoor proof of concept and progressing to a large prototype 20 km high at sea before constructing the production version to 40 km high. The development plan calls for a significant investment, starting at $100,000 in the first year and progressing to several hundred million dollars in some of the later years for the production version. Preparatory to that work, some detailed design has been taking place, with prototype parts of a small scale model being built, tested and redesigned over several iterations. This model is intended to reach a height of less than a meter, but it is small enough that useful work can be done within a modest budget of a few thousand dollars using tools and components that are available to an enthusiast.

In the original Lofstrom Loop, the rotor was envisaged as a continuous, flexible loop traveling inside an evacuated tube. However, in High Stage One a rotor is split into bolts, each of which is a short, rigid structure up to a meter in length. In the small prototypes, each bolt is 9 cm long. This arrangement allows a single experimental bolt to be tested over the various stages through which it needs to travel. When the design is mature enough, multiple bolts may be built by copying the successful version and then joining them into a continuous train that forms a rotor. Similarly, the static parts of the small model are composed of short segments which are relatively easy to replicate once a good design has been found.


Figure 4. High Stage One.

The different parts are illustrated in Figure 4 and Figure 5. Several pairs of tubes are used for the sake of robustness. At the surface station, the thrusters accelerate the rotors, which then pass up the ramp at 1.6 km/sec to reach the platform at a height of 40 km. The weight of the tubes and platform, plus the rotors’ own weight, deflects the rotors’ momentum vectors downwards so that they arrive at the far end of the structure. There, the rotors pass down the ramp, which brings them back to the horizontal. After that, they pass round the ambit, which turns them 180° so that they once more pass up the ramp, through a return tube and back down the ramp at the near end. Then they pass through the ambit there and continue indefinitely. The thrusters can make up for any loss of speed due to residual friction.


Figure 5. Detail of Surface Station.

The full-scale version extends over a horizontal distance of 112 km, whereas the smallest model occupies a length of 5 meters and the rotors travel at just 8 meters/sec. In the smallest model, it is not worth operating in a vacuum, and this makes it easier to observe progress and to make measurements and improvements. The single experimental rotor will move along a track, rather than inside a tube.

Magnetic levitation is a proven technology used in railways in China and Japan, and is also used in certain machines such as pumps with magnetic bearings. However, there is no off-the-shelf supplier, and the details needed for High Stage One are different enough that some additional design and experimentation are required. The bolts have permanent magnets on each side which are attracted to permanent magnets in the track. Electronic controls in each bolt ensure that it remains central, and thus balanced, between the two sides. When a bolt drops down or rises up, there is a strong restoring force, and this provides the means of levitation. When the rotor is switched off, the bolts rest touching one of the sides. When switched on, the electronic controls energize the coils so that the bolts move to the center; then they maintain that position.


Analogue circuits were tried for the electronic controls in the bolts, but they have now been replaced by digital circuits. The digital chips used can store data and they have a USB link, via an adapter, to a computer whereby they can be programmed. The computer software can also be used to read out data stored in the chips, which allows for measurements to be taken several times per microsecond and monitored later from the computer. In this way, various problems have been detected and corrected.

The main task of the digital chips in a bolt is to measure the difference between the distances of the bolt from each side of the track and to send a control signal to the power circuits that energize the coils. The distances are measured using infrared light-emitting diodes (IR LEDs) and IR-sensitive transistors in conjunction with reflective surfaces at the sides of the track. Separate circuits control the front and back coils. Eventually, an analogue circuit is likely to be more efficient in terms of speed and battery consumption, but the digital chips are more suitable for testing, measuring and debugging.

The strongest forces are encountered in the ambit. The design is such that the round parts of the ambit gradually increase in tilt so that the bolts perform a banked turn as they travel round it. This uses the permanent magnets to their maximum extent and minimizes the load on the coils. The forces in the ambit are much larger than those needed to hold a rotor against gravity – the centripetal force exerted is about eight times the bolts’ weight.

Once these tests have been completed satisfactorily, work on thrusters, a second ambit and other components may commence.

V. Conclusion

Spring Forward involves lowering the meter-wide tether into the atmosphere whenever a climber is to be launched, thus subjecting it to winds that will disrupt the movements for stretching the tether and avoiding space debris.

Box Protection is the simplest of the three options, but it does involve increasing the load on the tether by a factor of up to seven and a half. This factor can be reduced to six by making the tether climber smaller so that it acts less like a sail when it is climbing through the atmosphere, but this would constraint the space available to customers.


High Stage One relieves the tether of atmospheric effects and loads, and it uses proven technology and materials, but there is still a great deal of engineering effort required to turn the concept into a reality. It is the most complex of the three options.

Acknowledgments

Thanks are due to Gilberto Brambilla for advice on carbon nanotubes and to Keith Lofstrom for earlier input to the work on High Stage One.

References

1 Edwards B. and Westling, E., The Space Elevator, BC Edwards, Houston, TX, 2003 2 Knapman, J. and Swan, P., “Design concepts for the first 40 km a key step for the space elevator,” Acta Astronautica 104 (2014) 526-530 3 Knapman, J., Tether Climbers at Constant Power, International Space Elevator Conference, Seattle, WA, August 23rd–25th, 2013 4 Knapman, J., High Stage One, International Space Elevator Conference, Seattle, WA, August 25th–27th, 2012 5 Swan, P. A., Raitt, D. I., Swan, C. W., Penny, R. E. and Knapman, J. M., Space Elevators: An Assessment of the Technological Feasibility and the Way Forward, International Academy of Astronautics, Paris, 2013 6 Lofstrom, K., The Launch Loop, AIAA Paper 85-1368, July 1985 7 Knapman, J., “The Space Cable: Capability and Stability,” Journal of the British Interplanetary Society, Vol. 62 (2009), No.6, pp. 202-210


THE ISEC HISTORY COMMITTEE

Mark Dodrill Senior Software Engineer and

Lead for ISEC History Committee

ISEC Interview with Vern Hall during the 2014 ISEC Space Elevator conference in Seattle. Interviewer was Mark Dodrill.

About Vern Hall After obtaining his B.S. in Engineering from UCLA and serving in the US Navy for 10 years, Mr. Hall served as a Civil Engineer for the Port of Los Angeles on various projects for 27 years. He also served a key role in the multi-billion dollar "2020 Program", also known as the "Alameda Corridor Program", related to the modernization of the Ports of Los Angeles and Long Beach, CA. Most recently, Mr. Hall is part of a committee that is defining the role and function of the marine node in the Space Elevator program.

(Q) Can you please describe how you first heard about the space elevator?

(A) I heard of the concept in popular publications like National Geographic, in an article several years ago, and it is a very interesting concept. But it is only in the last 2 months where I have become more involved. Actually, I was approached by

an old friend of mine, Michael Fitzgerald, who is part of the ISEC (International Space Elevator Consortium) group, who wanted to talk to me about the Earth side of the Space Elevator, commonly called the Marine Node. That’s where my experience is in, building ocean structures. It was Michael and Peter Swan (President of ISEC) who got me excited about the concept.

(Q) The aspect that’s most interesting to you is the design and construction of the marine node?

(A) Correct. I am also peripherally interested in some of the legal, policy, structural, and organizational aspects of the project. I have a lot of experience in putting together organizations that can pursue mega projects, which I will discuss later.

(Q) Given your mega project experience, what would you do to build the Space Elevator?

(A) Due to the wide range of issues that are present, I would first go out and hire 10 young lawyers, with international law experience, in the context of understanding laws of the sea. In my view, the Space Elevator project is going to require a marine base with an exclusive economic zone (EEZ),


somewhere out on the ocean at the equator, where international laws of the sea would apply.

(Q) How can your background help with the Space Elevator project?

(A) One of the mega projects I worked on was with the Port of Los Angeles where I helped to create something called the Alameda Corridor. Los Angeles has a reputation as a big megapolis, where everyone goes everywhere in their cars. Back in 1980, we were developing the 2020 Plan, imagining what the Port of Los Angeles and the adjacent Port of Long Beach would look like in the year 2020, and what would need to be done to prepare to meet those future needs. We determined that the functions of the port would require a lot of trains, coming to and from the ports. And if you were to superimpose the amount of cargo and the number of trains we were predicting, on the grid pattern of streets, highways, and rail lines of Los Angeles, the results would be absolute and total gridlock. The trains are called unit trains and they are a mile long and take about 8 minutes to clear a single intersection. So if you have 250-300 intersections, and the trains have the right of way (which they do) you get total disaster. So, we

came up with a plan to mitigate those potential impacts, deciding that the only way to do that was to create a consolidated corridor and force all port rail traffic on to that corridor. And we planned to grade separate it from all the major crossings, to limit the number of intersections that would be completely blocked when a train went past. Because we chose an existing rail line parallel to a street called Alameda Street, the project came to be called the Alameda Corridor. This corridor connected both Los Angeles and Long Beach to the intercontinental rail lines that already exist and serve the rest of the country. The project was, from concept to construction, over 10 years in the making. And, back to my point, about 5 of those 10 years were the politics, legal, structures, wrangling with multiple agencies, getting legislation passed to allow the two ports to fund the project, getting the cooperation of the lawyers and the management of the railroads, and not the technical and engineering details to get the project done. So, my advice for the all the people interested in building the Space Elevator is that while you are resolving all your technical problems, you ought to be handling all these other issues as well, from day 1. Because otherwise you can have all of the greatest science in the


world, but if you can’t build it somewhere, it’s not going to do much good. So, I’m interested in what the marine node will look like, but I'm also advising that you better start doing your politicking, as soon and as often as possible!

(Q) Do you think the political/legal issues are going to be more significant than the technical issues? Or about the same?

(A) They just have to be tackled, you have to approach it as an engineering challenge, but you have to use different people to solve them. Instead of hiring scientists, you are hiring diplomats and lawyers and money people. You must approach it as another piece of the puzzle and don't just assume that it will just happen. It must be tracked in concert with and interfacing with the rest of the overall plan. Obviously, it all comes together when you really start construction at the site, wherever that site might be. You have time, my message is don't ignore it, since it takes so much time: get going on it right away.

(Q) On a different note, do you have a sense of who you think is going to be the entity that will actually build the Space Elevator? Do you think it will be private or the government?

(A) I hope it will be private. But I think it will have to be private or a quasi-private or consortium of sorts. I would guess that a piece of the US government will be involved, and maybe other governments too, possibly China, Japan, and/or Europe. But if it is going to be successful, it has to be something separate from the bureaucracy of any one government. It can’t come under Department of Defense (USA) or the Department of Homeland Security (USA). I don't have all the details, but certainly there are many agencies have been created quasi-public or private/public partnerships that have been very effective.

(Q) Have you had the opportunity to try to explain the Space Elevator concept to other people? What is the analogy or the way you communicate the idea to the general public?

(A) Yes, I have spoken to a number of people about it and most everyone loves it! I usually make a drawing of Earth on a piece of paper, with a line going away from the Earth. I show the marine node down at sea level at the equator. I show the International Space Station, which is about 260 miles in orbit on the line away from the Earth. I show the Hubble space telescope, which is at 347 miles,


and then we've got the apex anchor much farther down the line and then there's the moon and Mars somewhere. But, it’s easy to explain, and I’ve got a lot of people excited about it.

(Q) What’s the reaction you generally get from people?

(A) Oh, they understand it, they grasp the concept of going into space slowly on the cable, instead of on a rocket. And in the case of my oldest granddaughter I showed this, she said “when can I sign up for the first ride?” And the concept of moving paying customers into space for a 2 week round trip luxury cruise basically in space is really sellable, I think. Of course, that is going to come after you do the commercial and industrial stuff. And maybe 30-40 years from now. And the science of it is something I've got my grandson interested in. He is currently a sophomore in Engineering at Long Beach State, studying Mechanical Engineering with a Math minor that says “Hey this stuff is really right up your alley.” It’s the real world stuff that he should get interested in. It’s a neat thing.

(Q) What excites you about the Space Elevator?

(A) The thing that really excites me is what happens above the geosynchronous orbit node, and the ability to assemble things in space, probably by robots, and then shove them out the door and let them land on Mars. I don't understand orbital mechanics but the concept is amazing. Just by pushing it out the door at the right time at the right velocity and acceleration, boom! That’s the real future of space. You get a free ride because all the energy has been paid to get out of Earth’s gravity. Awesome! People don't laugh when I tell them about this. It’s quite exciting.

(Q) What would the 3 biggest impacts on mankind be, if the Space Elevator was built tomorrow and we started using it? How do you think that would change our world?

(A) I think the obvious one is the exploration of the other planets and the capturing and bringing back resources (space mining). To me that’s the biggest thing. Another thing is sending people up to see the Earth from space – space tourism. In one sense, it’s trivial, but it’s a good profit center -- a cruise ship in space. A good family cruise today to the Caribbean is going to cost you 20 thousand USD, if you include your kids and grandkids. For the price


of a one week cruise to the Caribbean, you could go into space for 2 weeks. It’s a no brainer. But, then I also think so much can be done with weightlessness as part of improving manufacturing -- the practical things you can do in space, without fighting gravity are amazing.

I think several people have said it. Once the space elevator system is in place, it opens the door for bright young people to come up with new applications of that system. In my lifetime there are many examples of that, most obviously in the computer realm. How many apps do you have on your phone today? That’s the beauty of having the Space Elevator as a private for profit enterprise, the market forces will allow people with new ideas will come in and do a simple business deal. No governments or studies or delays. And since it's a business deal, it can be done. Just the opening of the door to entrepreneurs and to applied scientists and inventors, creates a whole new future that’s not currently available. For several million dollars you can book a 10 min flight on Richard Branson’s ship. In order to get the price down, it’s always been economies of scale. The power you have in your cell phone which you pay $200 for. If you had to buy that power 10 years or 20

years ago, you would be spending much, much more.

(Q) Do you have anything else you would like to share on this topic?

(A) I think it’s time to start refining the concepts for the marine nodes (plural), because I think there will be more than one. It’s not going to look like an oil drilling ship – it will be custom designed for the functions that yet to be determined. The good news is there are people out there who know how to do that.

(Q) It sounds like you volunteering for that, right?

(A) Well, I can't do it myself, but I can organize. But I know people who put together things like that. The obvious example is an offshore semi-submersible, self-powered oil platform. A better model might be a ship that launches from equator, rockets into space, called Sea Launch. Sea Launch was produced by the joint efforts of private companies and governments. To me, this is a better model than an oil drilling rig. And going back to what a port does: a port is an interface to receive and distribute cargo. And so you custom design it for the type of cargo you are dealing with, and in the case of the marine node, the first ones can


be extremely industrial, no hotels on it or hoteling required for the crew. And platforms have crew facilities some of which are very lovely, but we will probably need a full blown weather station and tremendous communication equipment linked with satellites. On the marine side, you are going to need to receive shipments of several types, not just the ocean-going tug, but ships that are going to be long range, high speed cargo ships that may be custom designed. Probably catamarans, or tri-hulls, that will be coming out of maybe Hawaii, or San Diego, or Ecuador, or some land side distribution point. If it’s truly a two-way elevator, each marine node would probably be two platforms, servicing going up and then coming down. So you may have little work boats: you will require intense security, you will need helicopter platforms, you will have small boats running around the perimeter, keeping everybody away, fighting off the pirates. I mean these are mundane things, but all of the systems are known and have to be applied properly. I think everything is on the right track here. It’s good that you have experienced engineers and scientists pushing this thing forward because some day a politician may come and say “I want a space elevator, and I want it tomorrow.” The Space

Elevator community needs to be ready if this were to happen.

(Q) We really appreciate your help on the project and everything as a whole because the expertise you have in transportation systems.

(A) Many other people here understand the physics of space and orbital mechanics so I ignore those aspects. But then, the marine node and the communications center, the transportation elements is basically, it is a transportation project. And you have to move stuff, you are adding a new dimension. I used to preach this about the port industry, as I said earlier, the port is an interface that has to be efficient, and that’s the key word: move cargo, large volumes of cargo. In the case of ships, they continue to be the most efficient way of moving a lot of stuff over a long distance. For example, if you have a case of new Rolex watches you want to get to somebody, you put them on an airplane. But if you have a container full of Rolex watches, you going put it on a ship. And, by the way, there are containers that come into ports that are full of Rolex watches! So, you can have very high value cargo in a container, and you can have waste, recycled paper, shredded recycled paper in a container,


you don’t know until you open it what is in there. You can't tell the difference, but the point is it doesn't matter: the port interface becomes a transition from the marine node, which is the marine mode of transportation, to a landside mode. Currently, there are 3 landside modes of transportation: train, truck, and pipeline. Now we have a fourth mode, extending into space: sending and receiving from space. It just adds another dimension. So, the Space Elevator is a transportation project. And if I can help in that area, focusing and bringing together the right players to pursue it as a transportation project on the Earth and in the water, maybe I can help with it.


SPACE ELEVATOR SIMULATION: VALIDATION AND METROLOGY

Peter Robinson No Affiliation: Shrewsbury, UK

Abstract: A dynamic tether modelling tool is an essential component of any Space Elevator program, and will be required at all stages of work from initial concept development to deployment and operations. This paper outlines how a simulation tool could be developed, validated and integrated into the eventual elevator infrastructure. It does NOT describe the results of any modeling or propose any particular modeling solution, but includes an outline description of the metrology requirements to support test and deployed tether systems.

Introduction

Space Elevator studies to date have included the results of analysis of tether loading and motion using a variety of mathematical predictive techniques, and have been valuable in defining potential design concepts for the elevator tether, climbers and other system components. Some of these models have been based on differential-equation based analysis of entire systems, but have usually been simplified to reduce complexity. Other models have been of the dynamic multi-element type: such models are typically capable of greater complexity and so are probably more likely to yield results of the required accuracy.

Dynamic multi-element models are widely used in mechanical and fluid dynamics simulation, with application examples ranging from suspension bridges to engine combustion simulation to weather forecasting. The simulation of a space elevator system is likely to include a less complex model than some current applications, but there is a significant difficulty surrounding the lack of a real-world system with which to compare the output results: comparison with real-world behavior is an important step in the validation of any simulation model, and such validation will be critical if the model results are to be used to support the control of any safety-critical system (as is the case with an earth-based space elevator).

This paper will not attempt to analyze or select any particular simulation model type or source, but will describe how models may be validated and used in the speculated phases of an Earth Space Elevator program (with a Lunar Elevator as a preliminary subproject). It will also discuss what


metrology requirements may be necessary to support model validation and their use within Space Elevator control systems.

Simulation in Stages of Space Elevator Program

Table 1 summarizes the possible stages of an Earth Space Elevator program, speculating on activities not related to Simulation and describing in more detail the model-related work that could be included in each stage.

Note, the Lunar Elevator is included within the Earth Elevator project. It is recognized that this could well be run as an independent project, certainly pending invention of a suitable tether material for an ‘Earth’ system: whatever the project structure, Phases 1a to 1c would be required before 1d.


Project Phase Primary Activities Simulation / Model Activity

1a : Concept & Start-up

Elevator Concept Studies Ribbon Material

Development Climber Concept

Development Project Start-up

Simulation Tool & Model benchmarking.

Concept Exploration

1b : Groundwork

Elevator Concept Chill Ribbon Material

Development Climber Prototyping Earth-based

tether/climber tests & demonstrations

Tool validation against tether tests.

Sensor integration for initial state import

1c : Near-Earth Development

Earth Elevator tether material selection & development

Lunar Tether material manufacture

In-Space rotating tether/climber tests & demonstrations

Climber durability & reliability growth

Tool validation against space tests

Tool integration into tether/climber control systems

Demonstration of real-time control of tether deployment

1d : Lunar Elevator

Lunar Elevator Launch, Deployment & Operations

Earth Tether material manufacture

Model integrated with deployment control systems

Sensor validation Real-time control of

counterweight and climber systems

1e : Earth Elevator Deployment

Minimum-capacity Earth Elevator Deployment

First Climb to GEO Commence removal or

tagging of all LEO material

Develop multiple climber variants

Autonomous control of deployment

Validation of LEO material avoidance countermeasures

Autonomous climber validation

2 : Earth Elevator Initial Operations

Upgrade Earth Elevator to Operational Capacity

First manned ascent

Models fully integrated with distributed fully autonomous configuration & climber control

3 : Earth Elevator Full Operations

Multiple Elevators deployed

Full ascent/descent capability

Commercial Passenger rating

Table 1


Phase 1a: Concept and Start-up

This Phase represents the current (2015) status of the Space Elevator program, with preliminary concept work in progress in many areas.

Numerous studies have been undertaken using models of tether dynamics. Many of these appear to have used differential-equation (DE) based analysis of the entire tether system, often with simplifications such as exclusion of solar and lunar tidal forces. Other studies appear to be of the dynamic finite-element (FE) type: these have a greater potential to include all possible influencing factors (such as solar, lunar & planetary gravity, atmospheric & solar wind loading, etc.), but it is not known which models have been built with such complexity, or indeed if any work has been done to establish what complexity level is necessary for any particular level of accuracy.

The existing models appear to be allowing useful conclusions to be made regarding Space Elevator configuration, operations and safety, but these conclusions assume an adequate level of model accuracy, and this accuracy cannot yet be properly confirmed. This shortfall primarily stems from the absence of a real-world system with which to compare the simulation results: proper validation can only commence when extensive tether system testing commences.

One possible path forward would commence with benchmark evaluation of all existing tether system models. This evaluation should be undertaken by some independent entity (perhaps ISEC1), and could involve analysts being requested to undertake simulation of identical scenarios using their differing models. These could include simple scenarios to enable comparison of DE and FE models, plus more complex scenarios enabling comparison of more complex FE or other model types. These benchmark tests would define the tether and other mechanical characteristics such as initial geometry and tension profile, ground station location, model start date & time, etc.: tether geometry and tension results would then be requested at a number of subsequent points in time. Should comparison of the results from various models show little variability there may be some confidence in each model accuracy: if results were significantly different further work would be needed to understand the variability, but it may not be possible to determine which (if any) model was ‘right’ or ‘wrong’ without some real-world test results.


Phase 1b: Groundwork

This project phase would commence when resources became available to commence detail design, development and test of potential Elevator system components. Some of this work (such as tether material or climber design) would not be directly relevant to simulation model development, but any practical work involving lengthy tethers (with or without climber prototypes) could be valuable in providing model validation data.

Simulation tool verification and validation would be made possible by modelling the behavior of a test tether and comparing results with the observed actual behavior. This would require the actual tether position, geometry and tension to be known throughout the period simulated, sampled at regular length and time intervals. This will require measurement capability perhaps in excess of what might be specified for simple tether or climber tests: tether metrology systems would be required for the eventual deployment and operation of any Space Elevation system, so any development and test of measurement systems at this earlier program stage would not be wasted effort. Tether location measurement could be achieved by passive (such as laser or radar reflector) or active (such as GPS) devices attached to the tether: this phase of work could enable evaluation and ranking of these options against factors such as functionality, cost, accuracy, and of course any risk to a passing climber. Various options also exist for tether tension measurement and data transmission, ranging from basic strain gauges to more complex systems: again, options could be evaluation and ranked in this project phase prior to deployment in the later project phases.

There are numerous options for ground-based tether and climber testing, some of which have already been evaluated. External tests alongside a fixed structure (perhaps a building or cliff) would be limited in length but would enable simpler motion measurement. Sheltered or internal tests (perhaps within a building structure or mine shaft) would be also limited in length but would have the benefit of being shielded from wind loading, reducing the need to model this input variable. Longer tethers could be evaluated using balloon suspension, but drift of the system could make it difficult to obtain accurate position measurement. This drift problem would be eliminated if the balloon were tethered, either by the test tether or a separate cable, but this may only be possible if light wind conditions could be guaranteed. Another option could be some form of kite, allowing the use of fixed ground stations for position monitoring: this option would require a suitably strong tether, but that of course is a prerequisite for the entire Space Elevator project. The kite option would introduce


significant wind loading: this could be difficult to simulate accurately and might swamp any small tether motions induced for experimental purposes, but wind load modelling is an eventual requirement for an Earth Elevator system and so must be addressed at some stage.

In summary, ground-based testing could enable evaluation of space elevator simulation code but is limited in scope, and of course is not adequate to assess tether systems of more than a few miles in length. More complete code validation must await space testing in the next project phase.

Phase 1c: Near-Earth Development

This phase of the project would primarily be the technology test and demonstration phase prior to the deployment of the first Space Elevator. It is likely that a number of free-flying tether systems would be deployed, these would steadily build confidence in the deployment of tethers in orbit and in near-Earth space, with increasing tether lengths and configuration being evaluated.

Tether simulation models would be key part of this process, initially for planning tether deployment and then increasingly as a part of the tether control system. The actual motion and tension of the tether as it was deployed and subsequently in Earth/Moon/Sun orbit would need to measured, both to ensure tether configuration is as planned and to confirm ongoing simulation models. This would draw on lessons learned during the earlier project phase, but there will of course be greater challenges as the distance to the tether increases. GPS-based location, for instance, may not be sufficiently accurate above low earth orbit, and ground-based radar or laser ranging could be unfeasible: it may be necessary to deploy one or more dedicated metrology satellites to enable collection of accurate tether configuration and other data.

This phase of simulation tool validation would also need to include verification of the impact of moving climbers. Space testing of climbers on a rotating tether/counterweight assembly would be expected to be part of this program in any case, so collection of additional data could be the only incremental activity.

At a later stage of this phase of work it should be possible to integrate the simulation tool into the control system of a rotating tether assembly. This combined system would then be capable of autonomous control of thrusters and/or climbers to enable optimum deployment and yield a desired configuration, reacting to external factors such as tidal forces or


solar wind fluctuations without proscriptive pre-determined instructions. This capability would be essential for the deployment of any full ‘Space Elevator’ tether system and so must be demonstrated in advance.

At the time of writing (2014) some tether systems have already been experimentally deployed: it is not known what measurement accuracy was achieved or whether behavior matched whatever models had been used.

Phase 1d: Lunar Elevator

An Elevator to the Lunar L1 point may well be a project objective in its own right, but would also be an essential technology demonstrator before the deployment of the first Earth Elevator. Deployment of this system will need to be modelled from the earliest concept phase onwards, and the final hardware deployment will need to be accurately monitored ‘real time’ with predictive techniques used to make control corrections as necessary to maintain the desired configuration.

Any Lunar Elevator would need to be periodically monitored throughout its operation to ensure the configuration remains within the desired envelope, and the model supporting this will need to be regularly reset to match the ‘real world’. It must be remembered that the accuracy of the model can only be as good as the accuracy of the ‘Initial Condition’ measurement, and that this accuracy will degrade over time as the model will inevitably deviate from reality: the target for the model must be for this deviation to be negligible between resets. The positional and tension measurement systems would be as developed in Phase 1c (discussed above): positional metrology may need to be supported by lunar ground stations for laser ranging, or by lunar orbiters for GPS-type capability. The positions of any lunar-orbiting satellites (or parked asteroids) would also need to be monitored to enable potential elevator impacts to be predicted and correcting action taken.

The lunar elevator would be inherently more stable than an earth elevator, but there would still be some disturbance. Solar tides would have some effect, but the motion of the L1 point and associated lunar libration are likely to have a larger effect. The L1 point location will move as the moon-earth distance varies through the lunar orbit, this will result in a varying effective gravity force at the elevator counterweight. The magnitude of this effect will need to be established by modeling and the necessary countermeasures (if any) devised: these could include counterweight thrusting or tether reeling/unreeling on a monthly cycle.


It should be noted that accurate tether configuration prediction and control should enable more than one lunar elevator to be deployed, provided their ground stations were sufficiently far apart. Each elevator would need separate active control to avoid collisions or tangling, but this extra functionality should not be a massive extra burden on the control systems. It may be best to link the counterweights of these multiple tethers, or simply use a single counterweight, but this of course would need some negotiation if the tethers were operated by separate organizations.

After deployment of a Lunar Elevator it may be decided to deploy a Mars Elevator before the more difficult Earth Elevator, but this of course will depend on many non-technical factors, not least the status (and funding) of ongoing Mars colonization efforts. Simulation and control of a Mars elevator would again be critical: tidal disturbance would be far less than for either the lunar or earth elevators, but regular avoiding action will be needed to prevent impacts with Phobos or Deimos.

Phase 1e: Earth Elevator

It is unlikely that an Earth Space Elevator would be financed and deployed unless the risk of failure were negligible. The required confidence level would need mitigation of all conceivable risks and prior demonstration of all critical technologies, hence the assumption that a Lunar Elevator would need to be deployed first. If the Lunar elevator were to be built using some existing (2014) tether material it may be necessary to deploy a second lunar elevator, or at least a lengthy free-flying tether, using the intended earth-elevator material to gain long-duration space exposure experience.

A negligible failure risk would also require the danger of impact with orbiting material to be addressed. Clearance of all such material is of course one option, but this may well be impractical: it may be more feasible (and less costly) to somehow ‘tag’ all known material to enable all orbital parameters to be continually kept up-to-date. This tagging could be achieved by one of the techniques assessed during earlier space elevator development work, perhaps by use of radar systems (as now), or passive laser reflectors or active GPS-type devices. The database of orbiting material, including a forward projection of each item’s future path, would be integrated with the earth elevator predictive model and all future potential close-proximity encounters identified. The optimum evasion action could then be devised and implemented by the elevator control system, taking priority over the ongoing configuration management and climber control functions.


The above evasion functionality would need to be applied throughout the deployment phase of the elevator, and continue indefinitely (or until all orbital material is removed). In time the predictive model accuracy would be improved and the permitted clearance limit reduced, resulting in the need for less frequent evasive action and less potential disruption to the climber operations. As discussed in the previous section, the accuracy of the model depends on the accuracy of the metrology, so highly accurate positional measurement of both the elevator state and the orbital material is essential to prevent the need for too-frequent evasive action.

Phase 2: Earth Elevator Initial Operations

This phase will involve increasing the capacity of the first Earth Elevator and commencing regular full-load climber operations. The existence of a ‘real-world’ example will allow the predictive model of the elevator to be continually refined and improved during this phase, allowing the future tether position to be forecast with increasing accuracy for a longer period of time. This, coupled with inevitable ongoing metrology improvements, should allow for a further reduction of the frequency of evasive action, permitting climbers to proceed at their maximum velocity for longer and so maximizing capacity.

Phase 3: Earth Elevator Full Operations

By this stage, with multiple full-capacity elevators deployed, there should be no need for further simulation tool validation. The models and metrology systems will be fully proven and probably distributed in some form throughout LEO and the various elements of elevator systems, allowing each element (climber, countermass, GEO station, etc.) to take autonomous action if required to protect and optimize the elevator structure.

Recommendations

The above outline analysis attempts to make few detailed assumptions or proposals, accepting that detailed technology and project plan decisions will be made by whatever organizations or teams are undertaking the work. That said, there are some short-term recommendations that may add some clarity or focus to early simulation tool development process.


ISEC Tool Survey

CLIMB2 papers suggest that a number of simulation tools are in use for tether configuration analysis. It may be that these have already been identified and collated by some individual or organization, but this information is not readily available through the ISEC web site. It is suggested that ISEC take the lead in surveying existing simulation tools, identifying their owners, pedigree, software/hardware requirements, and any verification or validation that has been undertaken

ISEC Benchmarking

Following the initial Tool Survey, it is recommended that ISEC undertake Benchmark evaluation of simulation tools. This could take the form of requesting the users or owners of each tool to undertake a number of simulations of test cases: the results would then be compared and conclusions drawn.

This activity would of course require the involvement of the simulation tool users or owners: it is not proposed that copies of models would be run independently at this stage as non-expert usage may well introduce unwanted errors.

Simulation Tool Distribution

After simulation tool benchmarking, it is recommended that ISEC review other factors before making a recommendation for a tool (or tools) that could be made available to non-expert analysts for investigating various space elevator operational and design features.

Benchmark test performance would be important, but other factors to be considered must include simulation tool and code availability (free or open-source ?), support (training availability, embedded help or FAQs ?), parent operating system (preferably Windows or Linux ?), hardware requirements, user skill and/or training requirements, typical run times, user interface maturity, and more.

Model Library

Once a recommended simulation tool has been identified it must be hoped that multiple users (new and old) will use the tool to create models of various elevator or free-tether scenarios. It is recommended that users submit their models to ISEC for uploading to a model database (‘library’)


available via the ISEC website. This would allow analysts to build on the work of others, avoiding duplication of basic system modelling and so allowing each researcher to move forward into their own area of interest from a common starting point. It may be possible (depending on the final model and code structure) to upload individual model elements to calculate various parameters likely to be common to most models (for example, a subroutine or module with embedded ephemeris data to calculate gravity forces due to various bodies at any future point in time).

The ISEC model library would be ‘Open Source’, so it is anticipated that some organizations may prefer not to submit their more-complex models to protect their Intellectual Property. ISEC will need to review whether some requirement could be imposed on Library Users to eventually share their developed models in return for downloading the work of others, but this is beyond the scope of this paper.

1 ISEC – The International Space Elevator Consortium (http://www.isec.org) 2 CLIMB is the Space Elevator Journal, published by the International Space Elevator Consortium.


ANCHORED LUNAR SATELLITES FOR CISLUNAR TRANSPORTATION AND

COMMUNICATIONi

Jerome Pearsonii

Abstract

The concept is examined of anchored lunar satellites, balanced about the collinear libration points L1 and L2 of the Earth-moon system and attached to the lunar surface. The design parameters of such satellites are examined by applying the equations of the restricted three-body problem; the material strengths required are within those of available composite materials. Anchored lunar satellites could launch lunar materials throughout cislunar space electrically for 0.75 kilowatt-hour per kilogram, could provide essentially continuous lunar farside communications without stationkeeping propellants, and could supply a lunar base without lunar landing rockets.

Introduction

Since the Apollo lunar landings, the moon has popularly been considered a ”dead world,” hostile and useless except as a scientific curiosity. Only now are we beginning to realize what a storehouse of raw materials the moon can become. In the development of cislunar space, roughly the disk-shaped region enclosing the libration points of the Earth-moon system, the moon is the most accessible and least fragile source of metals, minerals, soil, and shielding for space colonies. As pointed out by Ehricke1, when the development of these space habitats begins we will come to realize how fortunate we are in having a ”dead world” so conveniently nearby.

In order to use fully the lunar resources, however, a transportation system must be developed to bring thousands of tons of lunar surface material into lunar orbit, to space colonies, and into high Earth orbit. One scheme to alleviate the high cost of rocket launching is that of the i Presented at the European Conference on Space Settlements and Space Industries, London, 20 September 1977. This work is not connected with the author’s official duties at the Flight Dynamics Laboratory. ii U.S. Air Force Flight Dynamics Laboratory, Wright-Patterson Air Force Base, Ohio.


electromagnetic launcher proposed by Clarke2 and developed into a feasible system by O’Neill and his colleagues3. A linear motor on the lunar equator would accelerate small pellets of lunar ores into an orbit intersecting the L2 liberation point behind the moon. Here a ”mass catcher” would retrieve the pellets and send them via slow space freighter to space colonies for construction of solar power satellites4.

The purpose of this paper is to investigate an alternative to this system – an alternative which shows the promise of greater efficiency, greater versatility, and eventually greater economy. The technique which will be investigated here is the use of anchored satellites for the launching of lunar materials into cislunar space. After the rocket and the linear accelerator (for airless worlds only), the anchored satellite represents the only known method of launching payloads to planetary escape velocity.

An anchored satellite is simply an extremely long, thin member in tension which is balanced about the stationary altitude and extends to the surface of the planet about which it revolves. Such a planet-to-orbit connection, if successful, would allow unprecedented techniques for launching payloads by using the energy of rotation of the parent body.

The concept of a tower which extends all the way into orbit apparently originated in an 1895 science-fiction story by the Russian rocket pioneer Tsiolkovsky5. He realized that a tall tower reaching geostationary orbit would experience a net gravitational force of zero at the top, but he did not see how such a tower could be built. The problem of building the tower was first solved theoretically by a Leningrad engineer, Artsutanov6, in 1960. Artsutanov was apparently the first to recognize the key requirement that the tower itself must be a satellite in geostationary orbit. This satellite could then be greatly elongated both upward and downward, using the gravity gradient for stabilization, until the lower end of the balanced tower touched the surface at the equator. Artsutanov envisioned a structure large enough to support passenger capsules shuttling between Earth and orbit; he called it a ”heavenly funicular.” He apparently published no technical papers, however, and his work is known only through the cited article published in Pravda.

Unaware of the work of Artsutanov, a group of American oceanographers led by Isaacs7 independently discovered the concept in 1966 and proposed a much smaller-scale version which they called a ”skyhook.” They proposed a pair of fine wires which could be alternately raised and lowered by ground-based machines to ”walk” payloads into orbit, and performed a static analysis of the wire strength requirements.


The concept for the Earth-to-orbit connection was again discovered independently by this author in 19758. This proposal was in the form of a large structure called an ”orbital tower,” and included the first dynamic analysis of the structure. The orbital tower was proposed to recapture the energy of payloads returning from orbit to propel other payloads into orbit. In a later paper9, the Earth-escape launch capacity of the orbital tower was examined and its limitations were defined in terms of the tower dynamic responses to payload launching forces.

Three independent discoveries in a span of fifteen years indicate that the concept, which may be called an ”anchored satellite,” is an idea whose time has come. Because the concept is not widely known, the design and capabilities of anchored satellites will be discussed before their applications to the development of cislunar space are investigated. The term ”orbital tower,” coined by this author, will be used for the general concept of a greatly elongated structure in orbit. If the structure is extended all the way to the parent body, the term ”anchored satellite” will also be used.

Characteristics of Orbital Towers

The general features of an orbital tower connected to a planet are shown in Fig. 1. The structure is balanced in tension about the synchronous orbit rs. The distance to the top for a balanced tower, rt , is a function of the length of the lower end, which is at the planet’s radius ro . The relation between ro and rt is found to be8:

1

In this equation the distances are normalized to rs = 1. For a balanced orbital tower above the Earth, rt = 3.56, corresponding to a radial distance of 150,000 km. Equation (1) is applicable to any single rotating body. For example, Mars has rs = 20,435 km and ro = 0.1986 rs . The height of the balanced Martian orbital tower is found from Eq. (1) to be rt = 3.0756 rs , or 62,850 km.


Fig 1. General Features of an Orbital Tower

Orbital towers are tapered in cross-sectional area to maintain a constant stress due to the tensile force at any point, from a maximum area at rs to minima at ro , and rt :

2

where h is the characteristic height of the building material, the height to which a uniform tower could be built in a one-g gravity field. In this equation h is normalized to the synchronous orbit radius: h = σ/ρg0 rs . The exponential taper goes to zero area at r = 0 and r = ∞. The tower remains in balance if it is truncated at ro and rt given by Eq. (1). The taper ratio is then defined as A(rs )/A(ro ).

The orbital tower can be truncated at any point above rs other than rt and be maintained in constant stress by attaching a counterweight mc at the top. This mass is selected so that its upward force on the tower is σA(rt ), where σ is the constant stress limit. The bottom of the tower then experiences an unbalanced upward force of σA0. If the tower is held in place at the ground, it will have a lifting capacity of σA0 . The size of mc is a function of its location rt :


3

where r¨t is the acceleration at rt .

Satellite Launching by Orbital Tower

The orbital tower allows travel into space by techniques which are fundamentally different from rockets. By providing a fixed structure to climb, the tower allows almost any kind of mechanical device to be used for propulsion. A motorized capsule with traction wheels to clamp onto the tower would be able to power itself into space. The energy source could be electrical, chemical, nuclear, or solar.

Launching payloads into space by this tower-climbing technique has almost none of the constraints of the rocket. There is no need to expend energy as rapidly as rockets, and thus no need for high thrust or high acceleration. There is no gravity loss, which means that a powered capsule can stop indefinitely at any height without expending energy. It can simply clamp firmly onto the tower until it is prepared to continue.

The tower ascent into orbit can be very efficient; it requires a surprisingly small amount of energy. A payload which climbs to the synchronous orbit has the correct velocity to simply disengage from the tower and remain in orbit. The energy which must be supplied is then just the potential energy difference between the planet’s surface and rs . This is given in terms of the payload mass m and the planet’s surface gravity g0 as:

4

This result shows that the total energy required to put a payload into geostationary Earth orbit is only 14.8 kWh/kg. At a typical busbar cost of 3 cent per kWh, this is an energy cost of 45 cent/kg into synchronous orbit.

Astonishing as it seems, the orbital tower could conceivably allow payloads to be placed into geostationary orbit for even less than the potential energy difference. A linear induction propulsion system10 could be used on the tower to propel payloads into orbit electrically. The same system could be used to absorb the energy of descending payloads to


generate electrical power. By operating payloads in pairs, the net energy input is only that required to overcome frictional and conversion losses and that required to lift any excess payload into orbit over that being returned.

These figures should completely revise our thinking on the minimum achievable cost of space travel. The Space Shuttle is expected to cost hundreds of dollars per kilogram put into low Earth orbit, and even advanced vehicles are expected to cost tens of dollars per kilogram11. Even higher costs are involved for stationary orbit. Because large amounts of carbon and water may need to be exported from Earth to space colonies beyond stationary orbit, it is imperative to bring launch costs down. The orbital tower represents the only known technique for these orders-of-magnitude reductions in Earth-launch costs.

Interplanetary Launching by Orbital Tower

For sending payloads beyond synchronous orbit, the orbital tower has the capability to transfer energy from the Earth’s rotation into the orbital motion of payloads located above the synchronous point. Since the tower is balanced about the geostationary point with constant angular velocity, the upper parts have greater than orbital velocity and tend to fly outward. A payload released from the upper part of the tower would be in a higher orbit and could be sent without rocket power to the moon or beyond. This property of the orbital tower means that the energy necessary to reach geostationary orbit is all that is required to send the payload to the moon, Mars, or even solar system escape8. This system of launching and recovering space payloads is truly an order of magnitude different from the system of rockets. The Earth orbital tower could launch a continual string of high-mass payloads to escape velocity for no additional energy over that needed to attain geostationary orbit9.

It is possible to imagine an interplanetary transportation system between the Earth and Mars, for example, consisting of an orbital tower attached to each body. Electrical propulsion systems could send payloads from the ground to synchronous orbit launch platforms, from which they would be released at the proper times to rendezvous with the other planet. By mid-course and terminal guidance, the payloads could match velocities with the receiving tower at a point above the synchronous orbit. They could then climb down the tower under electrical power to the surface of the planet, eliminating the need for heat shields.

Construction Requirements


There are serious obstacles to the successful construction of an Earth orbital tower; the foremost problem is the required strength-to-weight ratio of the building material. The only materials which promise the required strengths are the whiskers of perfect-crystals which have been made on a laboratory scale12. These whiskers, a fraction of a centimeter long and a few microns in diameter, show nearly the theoretical single-crystal tensile strength. If whiskers of alumina, graphite, silicon carbide, or boron could be successfully produced and bonded in a suitable matrix, they could be used as the Earth orbital tower material. At present, however, there is no practical building material available for an efficient, low-mass Earth tower.

In spite of the difficulties, the potential of the orbital tower for efficient, ecologically harmless launching of extremely large payloads makes it worthwhile to pursue the concept. In addition, the strength requirement is significantly less for construction of orbital towers about bodies of lower mass than the Earth, such as the moon.

Anchored Lunar Satellites

The orbital towers, or anchored satellites, discussed so far have been applied to the stationary orbit of a single planet. A more complex situation is the construction of an anchored satellite about the unstable libration points of a planet-moon system. In this case the satellite is constructed from the libration points L1 or L2 to the surface of the moon, which must have a captured rotation (one side always facing the planet). Isaacs et al.7, suggested the construction of a connection between L2 and our moon’s farside, but did not analyze this situation. The analysis which follows examines the general characteristics of such anchored lunar satellites, assesses their difficulties of construction and their launch capabilities, and discusses possible applications in the development of cislunar space.

The analysis of anchored lunar satellites is an application of the restricted three-body problem. In this case the primary bodies are the Earth and the moon, assumed to revolve in circular orbits about their barycenter, as shown in Fig. 2. Using in general the notation of Szebehely13, the barycenter is the origin of coordinates, the x-y plane is the orbital plane, Earth is of mass 1 − µ at (µ, 0) and the moon is of mass µ at (µ-1,0). The quantity µ is the ratio of the moon’s mass to the total mass, in this rotating coordinate system, the Earth-moon distance and total mass are normalized to one and the angular velocity of the moon is also set to one. With a unit distance of 384,410 km, the normalized time is 104.362 hours, the unit velocity is


1023.17 m/s, and unit acceleration is 0.00273 m/s2. The value of µ is taken to be 1/82.30.

Fig 2. Notation for Earth-Moon-Spacecraft Problem

The third body shown in Fig. 2 is located at distances r1 and r2 from the Earth and the moon, respectively, and is of such small mass that it does not affect their motions. The equilibrium points discovered by Lagrange are also shown in Fig. 2. The triangular points L4 and L5 are stable positions for third bodies; the collinear points L1, L2, and L3 are unstable equilibrium points.

We first assume that an anchored satellite is to be built about L2, which is at a mean distance behind the moon of 64,517 km. Referring to Fig. 3, the weight of a slice of the satellite of length dx is:

5


where ρ and A are the tower density and cross-sectional area, r1 x µ,

r2 x‐1 µ, and ω is the angular velocity of the moon,

Fig 3. Notation for Anchored Lunar Satellite Problem

where T and a are the period and semi-major axis of the moon’s orbit. Using the normalization that a = 1, ω = 1, Eq. (5) reduces to

6

for a balanced tower, where x0 is at the moon’s surface and xt is the unknown location of the tower top. Integration gives:

7


After some algebraic manipulation a quartic equation in xt is derived which can be solved numerically. The result is that xt = 2.36, and the length of the satellite is 525,724 km. This means that the top of the balanced satellite must be extremely distant to counterbalance the weight of the lower part of the satellite. A similar analysis of the balanced anchored satellite about L1 shows it to have a length of 291,901 km.

Because these structures must support loads which vary along their lengths, their cross-sectional areas may be optimized by sizing them for a constant stress. Using Eq. (5) for the differential weight, dW,of the L2 satellite,

where σ is the constant stress. Rearranging gives

Integrating and setting A(x = Li ) = Amax gives the cross-sectional area as a function of the distance:

8

where


The upper sign refers to the L1 tower (i = 1) and the lower sign to the L2 tower (i = 2). The taper required is seen to be an exponential function of the strength-to-weight ratio, very similar to the result for the Earth-anchored satellite8. These balanced anchored lunar satellites are shown to scale (with exaggerated diameters) and compared to the balanced Earth anchored satellite in Fig. 4.

Fig 4. Anchored Lunar Satellites Compared to the Anchored Earth Satellite

Design Requirements for Anchored Lunar Satellites

The taper ratios, Amax /A0 , for the L1 and L2 anchored satellites are shown in Fig. 5 as functions of the characteristic height of the building material. The characteristic height is the height that a uniform column of the material could attain in a gravity field of ge , the value at the surface of the Earth, without exceeding the stress limit at the base: h = σ/ρge . The taper ratio required for the anchored Earth satellite is also shown in Fig. 5 for comparison.


Fig 5. Taper Ratios Required for Anchored Lunar Satellites

The anchored lunar satellites are seen to be far easier to construct than the anchored Earth satellite. They could be made from existing engineering materials such as those shown in Table I. Data for these composite materials have been taken from the Advanced Composite Design Guide14. The graphite/epoxy composite could be used to construct anchored lunar satellites with taper ratios of less than thirty, but there is some question about the availability of carbon on the moon. In order to use this material, an outside source of carbon might be required, such as carbonaceous chondrites. Aluminum and boron are far more common1, but the boron/epoxy would require a taper ratio of nearly 100 and the boron/aluminum composite even more.


Design Strength

GN/m2 Density kg/m3

Characteristic height, km

Graphite/Epoxy 1.24 1550 81.6

Boron/Epoxy 1.32 2007 67.3

Kevlar 49 0.703 1356 52.9

Boron/Aluminium 1.10 2713 41.5

TABLE I. Candidate Materials and Properties for Anchored Satellites

The relative amounts of material required to build the L1 and the L2 anchored lunar satellites are shown in Figs. 6 and 7, respectively. The satellite mass per unit base area is given as a function of the satellite length for a taper ratio of 30. These figures also show the mass of the counterweight required to balance the satellite as a function of the satellite length. As an example, an L1 satellite with a base area of 10−4 m2

constructed of graphite/epoxy would total 5.31 X 108 kg. It would have a lifting capacity of 74,400 kg at the base, or 1,316,000 kg if this mass were spread uniformly between the lunar surface and L1. If this material were carried upward at an average velocity of 375 m/s, then in one year 2.77 X 108 kg could be carried to L1. From this point it could be launched without rockets to many points in cislunar space.

The mass and carrying capacity (kilograms of payload per kilogram of satellite mass) are shown in Fig. 8 as functions of the characteristic height of the material. Note that the L1 anchored satellite is lighter than the L2 satellite for the same carrying capacity. Note also that increased characteristic height dramatically increases the payload ratio; a change from 75 to 100 km, for example, more than doubles the payload ratio.

A different measure of the carrying capacity of the anchored satellite is the time required to carry its own mass into orbit. Table II shows these duplication times for various characteristic heights of the building material for the L1 satellite. Doubling the characteristic height from 60 to 120 km decreases the duplication time to about one fourteenth. This result again shows the importance of using the strongest possible material.

Construction Technique

To begin the construction of these satellites, an initial thin strand of material would be carried by rocket to L1 or L2, where it would be uncoiled and extended to the surface from a manned construction module. The upper


end could be terminated far short of the balance point xt given by Eq. (7) by attaching a large counterweight of mass mc. The use of a counterweight would add to the total mass required, but it would reduce considerably the mass of high-strength material needed. The counterweight could be almost any kind of inert mass, such as excess lunar surface slag from the processing of the high-strength building material or the remains of a carbonaceous chondrite used for its carbon.

Figure 1. L1 Lunar Satellite Mass and Counterweight


Once the initial strand was attached to the surface and put into tension by the counterweight, it could be used to support self-powered mechanical climbers. These devices could then carry additional strands of material to build up the satellite to its final size. The counterweight would be the proper mass to cause a net upward force on the base of the satellite of σA0 newtons. This force is then the net lifting capacity at the base.

Figure 7. L2 Lunar Satellite Mass and Counterweight


Because of the instability of L1 and L2, the anchored lunar satellite is not fail-safe. This contrasts with the Earth anchored satellite, which would continue in stable orbit if it were severed near the base and then jettisoned its counterweight. A break in the lunar satellite, however, would tend to make the upper part fly off into space or crash to the surface even if the counterweight were released. To prevent this from happening, an emergency stabilization system would be required. Such a system could take the form of a powered module located near the balance point and capable of lengthening or shortening the cable. Farquhar15 has analyzed the stability of cable-connected masses about L1 and L2 and found that this configuration could be stabilized by controlling the length of the cable. In case of a break in the satellite, part of the ballast mass could be released to bring the remainder of the satellite into balance; the stabilization module could then maintain the satellite in position until a repair could be made. The repair could take the form of extra strands of material lowered along the satellite to the lunar surface.


Fig 8. Mass and Payload Capacities for Lunar Anchored Satellites

Characteristic height, km Payload ratio Duplication time

years 60 6.2 X 10-4 7.67 80 21.3 2.23

100 45.4 1.05 120 85.7 0.55

TABLE II. Duplication Times for Anchored L1 Lunar Satellites


Applications of Anchored Lunar Satellites

Anchored lunar satellites can be used in the same manner as the Earth orbital tower to extract energy from the moon’s motion and use it to launch orbital or escape payloads. The potential energy required to lift a mass from the moon’s surface to L2, for example, can be found by integrating Eq. (5):

9

This amount of energy is 0.749 kilowatt-hours per kilogram. Once the payload is supplied with this energy by lifting it to the libration point, it can be allowed to slide to higher points of the satellite without additional energy and then be released to travel in cislunar space.

The dynamics of a body released from the lunar tower are very complex, because the gravity effects of both the moon and the Earth must be taken into account. The motion must be analyzed as a restricted three-body problem, which has received extensive analytical treatment. Using the notation of Szebehely, Fig. 2, the planar equations of motion of a small body in the vicinity of two massive bodies in circular orbits are:

10

and

11


Here the distances to the primaries are defined as:

12

and Ω(x,y) is a potential function from which the Jacobian constant C is defined:

13

and

14

These equations were programmed on a digital computer in order to find the trajectories of small masses released from various points on the anchored lunar satellites. Examples of these trajectories are shown in the next two illustrations. Figure 9 shows the orbit of a body released from near L2 with a small velocity toward the moon. This body performs a few orbits of the moon, then escapes through L1 into an elliptical orbit around the Earth. In contrast to this, Fig. 10 shows the trajectory of a body released from near L2 with a small velocity away from the moon. The result is a large elliptical orbit about the Earth and moon.


FIG. 9. Orbit of Small Body Released Near L2 with Small Velocity toward the Moon


FIG. 10. Orbit of Small Body Released Near L2 with Small Velocity Away from the Moon

This computer run was stopped when r1 reached three times the lunar distance. The difference in velocity between the two trajectories of Figs. 9 and 10 was just 0.02 units, or 20 m/s.

These examples show that a small change in the velocity of a body released from the L2 lunar satellite can drastically change the area accessible to it. A large part of cislunar space is therefore accessible from near L1 and L2 with very small velocity requirements.

The general features of such orbits can be understood by a plot of curves of zero velocity taken from Szebehely and shown in Fig. 11. This diagram shows the curves of constant C as a function of x and y for bodies of zero initial velocity with respect to the rotating coordinate system. These curves are not orbits; rather, they represent the boundaries of the region in which travel is possible by bodies of a given energy. These curves are symmetrical about the x axis, so only the upper half of the x-y plane is shown. The lower part of Fig. 11 shows the region about the moon in greater detail.


FIG. 11. Curves of Zero Velocity in the Earth-Moon System

In this diagram, the first important point is that the highest values of the Jacobian constant are represented by the Earth and the moon; at these ”point masses” C increases without bound. A body near the Earth or moon with a large value of C (low velocity) is constrained to remain within the curve about that body with that value of C. Secondly, notice that the stable libration points L4 and L5 have the lowest value of C (C = 3). These


positions represent extreme points on the energy diagram and require the most energy to be accessible to a spacecraft.

The third important feature of Fig. 11 is that the unstable libration points are represented by saddle surfaces. Along the x axis the value of C increases as we move away from L1, L2, and L3. Conversely, in the y direction the value of C decreases away from these libration points. What this means practically is that a small change in initial energy near one of these points results in radically different orbits.

Figure 12 defines the areas accessible to masses released from the L1 and L2 points on the anchored lunar satellites. The upper part of the figure shows the region accessible to the L2 release point by shading. The lower part shows the L1 accessible region shaded. The difference is that large orbits about both Earth and moon are accessible from L2 but not from L1. This extra capability from L2 can be represented by the velocity difference of 1 2 , or 130 m/s.

FIG. 12. Areas Accessible to Masses Released from the L1 and L2 Satellites


This diagram shows that a large volume of cislunar space is accessible from L1 or L2, including Earth orbits and lunar orbits. However, the L4 and L5 points are both excluded. This difficulty in reaching L4 and L5 has led Heppenheimer and Kaplan4 to propose that space colonies be located in an orbit about the Earth with a period of half a month, approximately as shown in Fig. 9. This orbit can be reached easily from L2 or L1. In contrast, L5 requires a velocity change of 440 m/s from L2, as can be seen by comparing the difference in the Jacobian constant between them of

2 5 = 0.430 units.

We can now summarize how the L1 lunar satellite could be used in the commerce of cislunar space. Material would be mined and refined at the base of the satellite, on the equator in the center of the near side. A manned station at the libration point would receive the lunar material and send it to its destination. Allowing it to slide down the tower toward the moon and then releasing it brings various lunar equatorial orbits in reach. Releasing with small velocities near L1 puts Earth orbit into reach; such launches could be used to send material to rendezvous with the upper part of the Earth orbital tower. By using an electrical propulsion system on the upper part of the Earth orbital tower, these payloads could be sent to the Earth’s surface or synchronous Earth orbit without rockets.

This cislunar transportation system can work in reverse, with the L1 station receiving goods from Earth or the space colonies and sending them to the base of the lunar satellite to supply the lunar base. The system could also function essentially identically by using the L2 satellite; the higher energy orbits about Earth-moon would then be accessible. The L1 satellite has the advantages of being slightly easier to build and having significantly greater payload capacity. It would also have the advantage of being constructed on the near side of the moon, being in continuous view from the Earth.

The Anchored Lunar Halo Satellite

The concept of the L2 anchored satellite lends itself to a communications link to the moon’s farside by using the ”halo” orbits shown in Fig. 13. Farquhar16 originally proposed stationing a relay satellite in a quasi-periodic halo orbit about L2 in order to provide continuous communication between the Earth and the moon’s farside. The halo orbit could be large enough to keep the satellite in continuous view of the Earth and also of a second satellite at L1. With accurate knowledge of the halo satellite’s position, an active control system could maintain a stable orbit


with small amounts of reaction propellant or with a solar sail, as suggested by Colombo17.

FIG. 13. Lunar Halo Orbit for Farside Communication

FIG. 14. Notation for Anchored Lunar Halo Satellite

The anchored L2 lunar satellite could also function as such a communication link, using the cable as a completely passive position control system. The concept is shown in Fig. 14 as a mass m in a halo orbit past L2 and attached to the center of the lunar farside by a tapered cable of length R. The cable is sized to maintain the mass m in balance by its


tensile force, making the mass equivalent to the counterweight given in Fig. 7. This system would act as a spherical pendulum free to swing in the y and z directions.

The motion of such an anchored satellite in three dimensions was examined under the assumption that the mass of the cable can be neglected compared to the mass of the satellite. The equations of motion in terms of the two angles θy and θz are:

15

where the forces Fy = m and Fz = m are given by Eqs. 10 and 11, and the distances are given by Eqs. (12).

These equations were first examined for the region of static stability. Using Fig. 14 as a guide, the anchored halo satellite is stable if the net force on the mass is in the negative x direction, opposing the cable tension. The stability boundary in the x − y plane is thus:

in which the forces are evaluated with all velocities equal to zero. The resulting stability boundaries for both the L1 and L2 satellites are shown dashed in Fig. 11. The side of each boundary marked ”s” represents the stable region and the side marked ”u” is the unstable region. In order for the mass to maintain a positive tension in the cable, the minimum cable length is the distance from the surface to L2 when the moon is at apogee, which is 68,056 km.


FIG. 15. Example Path of Anchored Lunar Halo Satellite Seen from L1

The nonlinear spherical-pendulum Eqs. (15) were programmed for a digital computer. The motion of the mass was found to be in general a complex Lissajous pattern, as shown in Fig. 15. These Lissajous paths occasionally cross the origin, resulting in communication blackouts by lunar occultations. The typical trajectory of Fig. 15, however, would result in communication loss during eclipses of only 11 hours in 65 days. The shaded circle shows the area in which the satellite would be hidden from L1.

Putting the anchored lunar halo satellite at near the minimum altitude for stability, say 70,000 km, means that the cable can be very small because of the nearly zero force on the mass. At this distance the mass of the satellite can be thirty times the mass of the cable. For a satellite mass of a few thousand kilograms, an extremely fine wire would suffice, with a total mass on the order of a few hundred kilograms.


Conclusions

The concept of anchored lunar satellites balanced about the collinear libration points L1 and L2 of the Earth-moon system has been examined. Such satellites would be far easier to construct than the corresponding Earth-anchored satellite in geostationary orbit. The anchored lunar satellites could be used to supply lunar materials to space colonies located at a variety of points in cislunar space without rocket power. The L4 and L5 points, however, cannot be reached without rocket thrust. The L1 satellite offers easier construction and higher lifting capacity. The L2 satellite offers advantages in communication with the lunar farside. The use of such anchored satellites for supplying lunar materials to space colonies could reduce transportation costs to nearly the theoretical minimum. Anchored satellites also provide a means of supplying a lunar base from Earth or space colonies without lunar landing rockets.

(Reprinted with the permission of 5The Journal of the Astronautical Sciences,

Vol. XXVII, No. 1, pp. 3962, January-March, 1979)

References

1 EHRICKE, K. A. ”Lunar Industries and Their Value for the Human Environment on Earth,” Acta Astronautica 1:585-622, 1974. 2 CLARKE, A. C. ”Electromagnetic Launching as a Major Contributor to Space-Flight,”JBIS 9:261-267, 1950. 3 O’NEILL, G. K. ”The Colonization of Space,” Physics Today 27(9):32-40, September, 1974. 4 HEPPENHEIMER, T. A., and KAPLAN, D. ”Guidance and Trajectory Considerations in Lunar Mass Transportation,” AJAA J. 15(4):518-524, 1977. 5 TSIOLKOVSKY, K. E. Grezy o zemle i nebe (i) Na Veste (Speculations between Earth and Sky, and On Vesta; science-fiction works), Moscow, Izd-vo AN SSSR, 1895, p. 35. 6 ARTSUTANOV, Y. ”V Kosmos na Elecktrovoze” (in Russian), Komsomolskaya Pravda, 31 July 1960. (A discussion by Lvov in English is given in Science 158:946-947, 17 November 1967). 7 ISAACS, J. D., VINE, A. C., BRADNER, H., and BACHUS, G. E. ”Satellite Elongation into a true ’Sky-Hook’,” Science 151:682-683, 11 February 1966. (A further discussion is given in Science 152:800, 6 May 1966). 8 PEARSON, J. ”The Orbital Tower: A Spacecraft Launcher Using the Earth’s Rotational Energy,” Acta Astronautica 2(9/10):785-799, 1975. 9 PEARSON, J. ”Using the Orbital Tower to Launch Earth-Escape Payloads Daily,” presented at the 27th IAF Congress, Anaheim, California, 10-16 October 1976. AIAA paper IAF-76-123. 10 KOLM, H. H., and THORNTON, R. D. ”Electromagnetic Flight,” Scientific American 229:17-25, October 1973. 11 WOODCOCK, G. R. ”Solar Satellites: Space Key to our Power Future,” Astronautics and Aeronautics 15(7/8):30-43, July/August 1977. 12 LEVITT, A. P. Whisker Technology, Wiley Interscience, New York, 1970. 13 SZEBEHELY, V. Theory of Orbits: The Restricted Problem of Three Bodies. Academic Press, Inc., New York, 1967.


14 Advanced Composites Design Guide, 3rd ed. U.S. Air Force Materials Laboratory, WPAFB, Ohio, 1973. 15 FARQUHAR, R. W. The Control and Use of LibrationPoint Satellites, NASA TR R-346, Washington, D.C., 1970. 16 FARQUHAR, R. W. The Utilization of Halo Orbits in Advanced Lunar Operations, NASA TN D-6365, Washington, D.C., 1971. 17 COLOMBO, G. The Stabilization of an Artificial Satellite at the Inferior Conjunction Point of the Earth-Moon System, Smithsonian Astrophysical Observatory Special Report No. 80, November 1961.


A BRIEF HISTORY OF THE SPACE ELEVATOR GAMES

Ted Semon Author, The Space Elevator Blog1

President Emeritus – The International Space Elevator Consortium2

Introduction

If you do an Internet Search on the term “space elevator” today, you will find literally millions of hits on web pages which have some connection to the space elevator (I just did this and Google returned ‘About 8,270,000 results’). Interest in this concept has increased tremendously in the last couple of decades.

One of the major contributors which greatly increased the visibility of the space elevator to the general public was the Space Elevator Games, a series of four competitions held over a five year period which were dedicated towards advancing technologies needed to build a space elevator. While other competitions have been held since then, I think it is safe to say that these are still the ‘gold standard’ which all other competitions must be measured against.

As the “Space Elevator blogger”, I was privileged to be involved with and blog about the last three of these competitions. Without a doubt, this was the most exciting space-elevator related activity I have been associated with. Spending time with people who were involved in the Games was very gratifying – I’m a big fan of the “can do” attitude.

It’s been a full 10 years since the first of these Games were held and memories about them are starting to fade. While I blogged extensively about them on The Space Elevator Blog, my blog posts were ‘snapshot entries’, not a complete record (although a good source of competition details, photos, videos etc.). This article is an attempt to commit to permanent record a summary of these Games.

Overview of the Games

In 2005, the National Aeronautics & Space Administration (NASA) launched the Centennial Challenges3:


NASA Centennial Challenges were initiated in 2005 to directly engage the public in the process of advanced technology development. The program offers incentive prizes to generate revolutionary solutions to problems of

interest to NASA and the nation.

The program seeks innovations from diverse and non-traditional sources. Competitors are not supported by government funding and awards are only made to

successful teams when the challenges are met.

There were several of these Challenges; Astronaut Glove, Regolith Excavation, Green Flight, etc. Two of these Challenges, Power Beaming and Strong Tether, involved technologies which have a direct application to the construction and operation of a space elevator.

An Israeli-American engineer, Ben Shelef, had the grand idea to leverage these two challenges into an event he titled The Space Elevator Games and formed The Spaceward Foundation4, in part, to acquire the resources to do so. NASA awarded Spaceward a five-year license to organize these two Challenges. In accordance with how NASA organized these Challenges, Spaceward would devise the rules for each Challenge, procure a competition venue, recruit the competitors and coordinate all of the activities for each event. NASA would review and approve the rules and, if there were any winners, award them prize-money based on the Challenge results. NASA also provided administration and consulting expertise and some advertising as well.

During this five year agreement, four sets of competition events were held:

2005 – Both Challenges were held at the NASA facility in Ames, California.

2006 – Both Challenges were held in Las Cruces, New Mexico, initially as part of that year’s X Prize competition.

2007 – Both Challenges were held at the Davis County Event Center in Layton, Utah.

2009 – The Power Beaming Competition was held at the NASA Hugh L. Dryden Flight Research Center (renamed the Neil A.


Armstrong Flight Research Center in 2014) located wholly within the Edwards Air Force Base in southern California while the Strong Tether Challenge was held at the Microsoft Conference facility in Redmond, Washington, along with the annual Space Elevator Conference hosted by the International Space Elevator Consortium (ISEC).

For the 2005 event, NASA provided a $100,000 prize purse ($50,000 for each Challenge). In 2006, NASA increased this to $400,000 ($200,000 for each Challenge). In 2007, NASA further increased this to $1,000,000 ($500,000 for each Challenge) and for 2009, NASA provided a total prize purse of $4,000,000 ($2,000,000 for each Challenge).

In the first three events, no winners were declared (though one team from Canada came very close in the Power Beaming Challenge – twice!). In the fourth and final event, the team from Lasermotive LLC5, an American engineering company based in Seattle, Washington, won the first level of the Power Beaming Challenge and with it, a $900,000 prize.

The 2005 Challenges

My involvement with space elevators began in early 2006, so I was not involved in the 2005 Challenge. Thus I am indebted to Ben Shelef (and the Internet Archive “WAYBACKMACHINE”6) for helping to fill in the details of this event.

This inaugural event was held in October of that year at the NASA Ames Research Center, located in Mountain View, California and was a four-day affair. For this first set of Challenges, NASA put up a total prize purse of $100,000.

The 2005 Power Beaming competition

NASA offered a prize purse of $50,000 in this first year. Climbers were mounted on a 50 meter long, 4” wide tether suspended from a crane at the height of 5 meters and had to climb to the 50 meter level at an average speed of at least 1 meter per second (m/s) to be eligible for the prize. There were also other requirements; Climbers had to descend within a maximum length of time, they had to do so under control, etc. If only one team succeeded in meeting all of the requirements, it would win the full $50,000. If multiple teams succeeded, the prize purse would be divided according to a set of criteria set out in the rules. The Climbers could not carry any fuel, they had to be beam-powered, i.e. power transmitted to


them wirelessly. For this first competition, all of the beam power was generated by 70 kW portable searchlights provided by Spaceward.

Six teams entered this competition;

Team Name Where from Power Source

USST (University of Saskatchewan Space Design Team)

University of Saskatchewan, Saskatchewan, Canada

Spaceward provided searchlights.

Snow Star University of British Columbia, British Columbia, Canada


MClimber University of Michigan, USA Spaceward provided searchlights.

Star Climber Private group from Maryland, USA


SpaceMiners Private group from Texas, USA Spaceward provided searchlights.

Centaurus Aerospace Private group from Utah, USA Spaceward provided searchlights.

Table 1.

Every team except Star Climber used photovoltaic cells on their Climber to convert the light beam to electricity to power their Climbers. Star Climber used a Stirling Engine which was powered by the heat generated from thermoelectric cells.

Only the two Climbers from the Canadian teams were able to successfully make a beam-powered climb on the ribbon. The Snow Star team was first to actually succeed in climbing, ascending about 20 feet before stalling out. Starting a tradition that was to carry forward to future competitions, USST performed the best, ascending about 40 feet, but not quickly enough to be eligible for any prize money.

The 2005 Strong Tether competition

For the Strong Tether competition, NASA provided a separate $50,000 prize purse. The rules were simple. Tethers had to be in the form of a closed loop, had to weigh a maximum of 2.5 grams, had to be at least 2.5 meters long and could be no wider than 200mm. Each team also had to provide four identical tethers. Once a tether was measured and certified as being within specifications, it was placed on a competition apparatus (nicknamed the “Tether Torture Rack” - TTR). The TTR allowed two tethers


to be placed on separate rollers which, when the competition started, were simultaneously forced apart with hydraulic pressure. Whichever tether broke apart first was the loser. A strain meter was attached to the TTR to provide a numerical value of the force applied to it.

When a tether would break, it was eliminated and the team with the winning tether would move on to the next round. This would continue until only one team was left. This team’s tether was then matched against a ‘House Tether’, a tether made of COTS (Commercial, Off-The-Shelf) materials which was identical in form to the competition Tethers except it weighed 50% more. If the competition tether was able to defeat the House Tether, it would mean that it was at least 50% stronger than the House Tether and would therefore be eligible for prize money.

Four teams entered this competition;

Team Name Where from Tether Type

Centaurus Aerospace Private group from Utah, USA Unknown

Fireball Private group from New Mexico, USA Unknown

Tethers Unlimited Company from Washington, USA Unknown

Carbon Neanderthals Private group from Washington, USA Unknown

Table 2.

The Tether from Centaurus Aerospace won both of its matches and was then was matched against the House Tether. The Centaurus Aerospace tether lost but broke at a very respectable 1200+ pounds. The House Tether was then tested and broke at 1300+ pounds so the Centaurus Aerospace tether came very close to winning.

The 2006 Challenges

This event was held in Las Cruces, New Mexico in conjunction with that years X Prize Cup. The venue for the X Prize Cup was the Las Cruces International Airport and, for two days, the Power Beaming Challenge was also held there. One of the teams, however, had a microwave powered Climber and the Airport refused to allow it compete on Airport grounds. So on Day 3, the Space Elevator Games moved to the nearby County Fairgrounds and finished up there.


Coverage of the 2005 Challenge drew worldwide interest and resulted in 20 teams registering for the 2006 event, including the first non-North American entries. For this year’s Challenges, NASA put up a total prize purse of $400,000, $300,000 in ‘new’ money plus the $100,000 left over from the 2005 event.


The Power Beaming rules had many similarities to the 2005 competition; the racecourse was still a 50m high, 4” wide ribbon suspended from a crane, competitors would still mount their Climbers on the ribbon and start their timed climb at 5 meters and the goal was still 1m/s. However, the teams now had to provide an end-to-end solution, i.e. they had to bring their own beam source. Also, NASA increased the prize purse to $200,000. Six teams passed the Qualification runs and were able to compete:



University of Saskatchewan, Saskatchewan, Canada Searchlights

Snow Star University of British Columbia, British Columbia, Canada Reflected sunlight

MClimber University of Michigan, USA Searchlights

TurboCrawler Max Born College, Germany Searchlights

Kansas City Space Pirates Kansas City, Kansas, USA Reflected sunlight

Lite Won Campbell, CA, USA Searchlights

Table 3.

In addition, there were several other teams that registered and showed up, but were unable to compete for various reasons. These were:

Recens – A team from Spain. Their equipment got caught up with a Customs issue in Germany and ultimately did not arrive at the competition.

SpaceMiners – They burned out 4 cells on their photocell array on a qualification attempt and ultimately were unable to repair their Climber in time.


Star Climber – They suffered an ultimately fatal mechanical problem with the ribbon gripping mechanism and the gears driving it trying to qualify.

Beamer1 – When their Climber was being weighed in, it somehow got disconnected from the scale and crashed to the ground. The lens fractured and became unusable.

PunkTaurus – This was a combination of the PunkWorks and the Centaurus Aerospace teams. The PunkWorks Climber was powered by microwaves. They could not get their equipment working and it looked like they wouldn’t be able to compete. At the last minute, however, the Centaurus Aerospace team showed up and they too, had a microwave powered Climber. The two teams decided to combine forces and thus PunkTaurus was born. As mentioned earlier, the Power Beaming competition was eventually moved to the local County Fairgrounds to give them a chance, but they could not get their equipment working.

All of the competing teams Climbers were able to successfully climb to the top of the tether except the Kansas City Space Pirates (which did successfully negotiate a significant portion of the course) and Snow Star. MClimber had the distinction of being the very first Climber to ascend the entire length of the ribbon while USST completed the course in, by far, the best time – 57 seconds, just two seconds two slow to claim the prize. USST’s time was so close that the Spaceward team had to re-measure the ribbon for elastic and plastic elongation to determine if a winning run had been made.

One other note about the entry from USST is worth mentioning. They came very close to winning with their second choice of beam power. They had brought a laser and hoped to power their Climber with it, but were ultimately unable to get it working properly and had to resort to using searchlights.


The rules for the 2006 Strong Tether Challenge were similar to those from 2005, but the weight requirement was reduced from 2.5 grams to 2 grams and the length requirement was reduced from 2.5 meters to 2 meters. NASA also increased the prize purse for this Challenge to $200,000. Four teams registered for and competed in the Challenge:


Team Name Where From Tether Composition

Astroaraneae Private group from California, USA Unknown

Snow Star University of British Columbia, Canada Unknown

Centaurus Aerospace Private group from Utah, USA Unknown

Fireball Private group from Washington, USA Unknown

Table 4.

While tethers from all four teams met the 2 gram limit qualification, only the tether from Astroaraneae met the 2 meter limit qualification. This meant that Astroaraneae won the competition among the individual teams by default, something which caused much heartache from the disqualified teams.

In the spirit of competition, however, the Fireball and Snow Star tethers were matched against each other in a “non-title” match. Snow Star won when Fireball’s tether parted at 531 pounds. Snow Star then took on Centaurus Aerospace in another friendly competition. Centaurus Aerospace won when the Snow Star tether parted at about 880 pounds.

The Astroaraneae tether was then matched against the “House Tether” to see if it would qualify for prize money. Alas, it did not, breaking at about 1,336 pounds. And as it turned out, this was the strongest measurement of any competitor’s tethers in the entire Games.

Once that was completed, the House Tether was then matched against some rope, just to see what level the House Tether would break at. Unfortunately, both tethers proved to be too strong for the TTR and they broke the machine – a fitting end to a disappointing competition.

The 2007 Challenges

This year’s Challenges were held at the Davis County Event Center in Layton, Utah (near Salt Lake City). Originally scheduled to run from October 19th through the 21st, they were extended by several days due to weather-caused delays and also to accommodate additional competition runs.



The rules for the 2007 competition again were similar to the 2006 rules, but the height of the racecourse was doubled to ~100 meters and the speed necessary to win a prize was also doubled to 2 m/s. The prize purse was also significantly increased to $500,000.

While many teams (~20) registered, ‘only’ seven showed up at the competition.



University of Saskatchewan, Saskatchewan, Canada Laser

LaserMotive Professional group from Washington, USA Laser

Punkworks / McGill Canada Microwaves

E-T-C Japan Searchlights

Technology Tycoons Campbell, CA, USA Searchlights

Kansas City Space Pirates Kansas City, Kansas, USA Reflected sunlight

Snow Star British Columbia, Canada Reflected sunlight

Table 5.

All of these teams were able to mount Climbers on the ribbon and attempt runs, but three of them, LaserMotive, Punkworks and Snow Star, were unable to make it to the top of the ribbon.

The Kansas City Space Pirates (KCSP) had the fastest measured climb rate over a significant portion of the ribbon, well over 3.5 m/s, but unfortunately could not keep this up over the entire climb. Their best time to the top of the ribbon averaged out at 1.25 m/s. USST had the fastest climb to the top of the ribbon (and they were able to make multiple climbs to the top, the only team to do so) but their best time, 1.8 m/s, was just slightly under the required 2 m/s necessary to be eligible for a prize. This was the third Power Beaming competition in a row where the USST Climber had the best performance.



The rules for the 2007 Strong Tether Challenge were very similar to the 2006 Challenge; the tethers had to be at least 2 meters in length, they could weigh no more than 2 grams and they had to beat the House Tether (which could weigh 50% more) in order to be eligible for prize money. The prize purse in this Challenge was also increased, to $500,000.

Only two teams entered tethers for this Challenge:


Astroaraneae Private group from California, USA Unknown

Delta-X MIT, Massachusetts, USA Carbon nanotubes

Table 6.

Delta-X brought the first carbon nanotube tether ever entered into the Strong Tether competition but it was so new that they had not had time to form it into a true loop – they wound up tying the ends together in a knot.

The tethers from both teams met the qualification criteria, so they were matched up in a head-to-head competition. It was a foregone conclusion that the Delta-X entry would separate at the knot and this was, in fact, what happened – it was a rather anticlimactic victory for Astroaraneae. They were then to be matched against the House Tether to see if they would be eligible to win a prize, but they inexplicably refused to do so. So, once again, there was no prize winner this year.

The 2009 Challenges

It had originally been hoped to have the next set of Challenges in 2008, but several factors, most significantly that of trying to find a venue which could handle the new Power Beaming Challenge requirements, conspired against this. After a lot of searching, the venue selected was the NASA Dryden Flight Center located in southern California near Mojave.

The Power Beaming competition was first scheduled in early 2009, and then in August but it was finally held in November of that year. The Strong Tether Challenge was held in conjunction with the annual Space Elevator Conference held by the International Space Elevator Consortium (ISEC) in August.



The rules for the 2009 Power Beaming Challenge were similar to prior year’s competitions but the requirements to win any money were made significantly more difficult. The prize purse for this Challenge had been increased by NASA to $2,000,000. Teams had to have their Climber ascend the competition tether with a minimum speed of 3 m/s to be eligible for the first-level prize of $900,000. If a team could make the run with an average speed of at least 5 m/s, they would then be eligible to win the entire $2,000,000. The ‘racecourse’ for this event was a kilometer long steel cable held aloft by a helicopter. The starting point was at 100 meters so the timed run was 900 meters long.

Because of the difficulty in satisfying these requirements, only teams with laser-powered Climbers joined this competition. There were three of them, all veterans of previous years’ events.



University of Saskatchewan, Saskatchewan, Canada Laser

LaserMotive Professional group from Washington, USA Laser

Kansas City Space Pirates Kansas City, Kansas, USA Laser

Table 7.

Each team used a different tracking mechanism to keep their laser pointed at the photovoltaic cells on the Climber. USST used a GPS-based system. The Kansas City Space Pirates (KCSP) team used an automatic beam tracking system while LaserMotive tracked their Climber manually with a camera and a joystick.

LaserMotive was the only team to be able to climb the entire length of the cable and they did so multiple times. In addition, they were able to climb the cable in a best time of 3 minutes, 48 seconds, which worked out to a speed of about 3.95 m/s, more than enough to win the $900,000 prize. Once they had qualified for that prize, they then stripped off every gram they could from their Climber in an attempt to win the $2,000,000 prize, but their Climber failed during the attempt. KCSP was able to climb several hundred meters multiple times, but different failures kept causing them to


be unable to ascend the full distance. And, in something which remains inexplicable, the USST Climber was barely able to climb any distance at all. It was most puzzling. They were the most experienced team (all-around and with lasers) and they had performed the best in the previous three competitions, but this time around it was just not to be.

Still, these Challenges were finally able to award some prize money, $900,000, to the LaserMotive team – congratulations!


For this year’s Challenge, NASA had increased the prize purse to $2,000,000 and, concomitantly, rules to win prize money were even more difficult than in previous years. A competition tether still had to meet the ‘no less than two meters long and weigh no more than 2 grams requirement’ and then would have to beat the house tether in a head-to-head match. If successful, it would then have an absolute measurement made of its breaking strength. If this exceeded 5 Mega-Yuris (5 GPa-cc/g or 5 N/Tex), then it would eligible to win prize money.

There was only one entrant into this year’s competition;


Shizuoka University Japan Carbon nanotubes

Table 8.

This was only the second carbon nanotube tether we had seen in a Strong Tether competition and, alas, it didn’t perform any better than the one from Delta X in 2007. While it was formed as a true loop without a knot holding it together (it looked like a thin ribbon, very similar to the old VHS or Betamax video tapes) it parted at a very low load, barely registering on the strain meter.

Some Final Notes…

There was some interest in holding one more set of competitions in 2010, but ultimately it did not happen.

Unfortunately, NASA decided not to renew these two Challenges (despite persistent efforts from ISEC to get them to renew the Strong Tether Challenge). In 2010 and 2011, ISEC sponsored its own Strong Tether competition, using the same basic rules and equipment which had been


used in the NASA-Spaceward Challenge, but these events produced no winners either. There were multiple carbon nanotube entries for both of these competitions, but none of them even approached the strength of commercial materials, let alone exceed them, as would be necessary to win some prize money (or build an earth-based space elevator).

Two other organizations have held ‘serious’ Climber competitions, EuroSpaceward7 and the Japan Space Elevator Association (JSEA)8. EuroSpaceward has held two competitions and there is talk of organizing a third. JSEA has been holding Climber competitions for several years, each with an increasing level of difficulty (much the same as the Space Elevator Games), but the climbers in these two competitions (as well all of the other academic / school kid / robotics / science fair competitions I’m aware of) are battery powered.

No one yet knows, of course, how we’re actually going to build a space elevator, but when that day comes, I think it’s fair to say that The Space Elevator Games will be seen as an important early step in the process. Most, if not all of the technologies used in the Power Beaming competition will probably be relevant, even if lasers are ultimately replaced with another power source. And the need for a material to create a strong tether, is, of course, absolutely crucial to building an earth-based space elevator.

It’s been estimated that the minimum tether strength to build an earth-based space elevator is in the range of 25-30 MYuris9 (stronger is better, of course), about an order of magnitude above the material we have today. It’s fortunate we now have several possibilities for ultra-strong materials in the lab (boron-nitride nanotubes, carbyne, diamond nanothreads and graphene as well as carbon nanotubes) and hopefully a breakthrough will happen in at least one of them in the relatively near future.

We’re all waiting as fast as we can…


Additional Reading

The Space Elevator Blog1

The Spaceward Foundation4

The International Space Elevator Consortium2

The Space Elevator Reference10

The NASA Centennial Challenges website3

References

1 http://www.spaceelevatorblog.com 2 http://www.isec.org 3 http://www.nasa.gov/directorates/spacetech/centennial_challenges/index.html 4 http://www.spaceward.org 5 http://www.lasermotive.com 6 https://archive.org/web/ 7 http://www.eurospaceward.org 8 http://www.jsea.jp 9 http://www.spaceward.org/documents/papers/SEFC.pdf 10 http://www.spaceelevator.com


YEARLY STUDY REPORTS FROM THE INTERNATIONAL SPACE ELEVATOR

CONSORTIUM Dr. Peter Swan

President – The International Space Elevator Consortium (ISEC)

The International Space Elevator Consortium (ISEC) Board of Directors has determined that a single topic focus each year results in far more productive activities. This selection of a single topic enables the small volunteer organization to focus its efforts on a topic to enable consistency across it conference, its scientific pursuits, its discussion groups and individual involvements. Therefore, ISEC annually selects a 'Theme' to focus its activities around for that year. ISEC commissions a study activity based upon the annual Theme. Each resulting study report is designed to provide a broad, definitive and current look at the topic in question. It's also intended to counteract some of the misinformation that is so prevalent about the Space Elevator. Each ISEC Study is conducted for approximately a year, depending on the topic, and is managed by the Director of Studies.

Each ISEC study is managed by a Team Lead. This person is selected by the ISEC Board of Directors and responsible for the year-long study, to include: assemble a team, research the available literature, analyze the information, and prepare the report. Once the preliminary Report is completed, it is sent out to a broad list of people (including attendees at the International Space Elevator Conference) for review and comments. These comments are then incorporated, as appropriate, into the report and then a more formal review process takes place. The completed reports from each of the studies based upon yearly themes are:

2014 Topic: Space Elevator Architecture and Roadmaps

2013 Topic: Design Considerations for Space Elevator Tether Climbers

2012 Topic: Space Elevator Concept of Operations

2010 Topic: Space Elevator Survivability - Space Debris Mitigation


The following pages address each completed study. A print copy of each Report can be purchased from lulu.com. Visiting this site also allows you to see a preview of this Report. You can also purchase a pdf version of this Report from the ISEC store at: www.Lulu.com.

2014 Topic: Space Elevator Architecture and Roadmaps

Team Lead: Michael “Fitzer” Fitzgerald

Team Members: Peter Swan, Robert "Skip" Penny and Cathy Swan


This 2014 study report establishes a baseline roadmap for designing space elevators for the future. This study addresses critical aspects of space elevator infrastructures: basic architectures and how we will get there with a roadmap. The roadmaps will leverage desired paths to lower risks and identify approaches for pulling together the diverse concepts. The three architectures in the literature today are solid looks at various approaches, while not providing that key element of “how will we get there?” Each path from today to the successful implementation of a space elevator infrastructure must be identified and discussed with respect to hurdles and milestones. The study has three architectures being compared:

1. Dr. Edwards baseline architecture [2002]

2. International Academy of Astronautics architecture [2013]

3. Obayashi Corporation architecture [2014]

The methodology used is explained in Figure 1.

Step One in the roadmap is essentially a statement of where one is. In the mind of the Architecture and Roadmaps (A&R) team, this upper left corner is reserved for a statement of where we are.

Step Two shows where we are headed. It is a citation of our destination: "An Initial Operational Capability." By having a destination, the roadmap makes more sense as one transitions towards it.

Step Three in each of the five roadmaps / pathways is a documentation of the essential purpose of the functions of the segment. In the case of the Climber Segment, the A&R team saw three key functions of the climber: a) Repairing the tether, b) Releasing satellites at various altitudes, and c) Operating above GEO.

Step Four is a valued position along the pathway. Based upon the topics cited in #2, the team strongly suggests that the Technology Development Plan be used as a reference to determine technology and engineering readiness.

Step Five is the beginning and the completion of the readiness assessment process. This distillation of technological and engineering issues reveals the criteria for which progress toward an implementation plan is measured.


Figure 1

Step Six is the citation of the technical content needed within each of the Segment’s culminating demonstrations and the delineation of how (and how well) the Segment is ready to begin execution of the implementation planning process.

Step Seven is the start of the building of the programmatic planning package to plan the effort needed to design, build, and test the IOC Space Elevator.

Each of these seven steps is intrinsically in each of the five roadmaps built by the A&R) team. All five of the roadmaps are reviewed and discussed in detail in separate chapters. The reader should appreciate two things: how much we learned by the process and how much more we have to learn. The five segments compared are: Headquarters – Primary Operations Center; Marine Node, Tether System, Apex Anchor and Tether Climbers.

A print copy of this Report can be purchased for $9.50 (plus shipping & handling) from lulu.com. Visiting this site also allows you to see a preview of this Report. You can also purchase a pdf version of this Report for $2.14 from the www.isec.org store page.


2013 Topic: Design Considerations for Space Elevator Tether Climbers

Team Lead: Dr. Peter Swan

Team Members: Dr. Peter Swan, Dr. Peter Glaskowsky, Dr. John Knapman, Robert "Skip" Penny and Dr. Cathy Swan

This 2013 study report establishes a baseline for designing the climbers. The summary is as follows:


"The 2013 ISEC study report addresses a critical aspect of the space elevator infrastructure: the tether climber. The tether climber will leverage 60 years of spacecraft design while incorporating aspects of traditional terrestrial transportation infrastructure..."

The study is organized as follows:

Chapter 1: Introduction

Chapter 2: Tether Climber Operational Phases

Chapter 3: Sub-System Description

Chapter 4: Power Sources

Chapter 5: Conclusions and Recommendations

Space elevator tether climber design has always been challenging and intriguing to the interested. These climbers can be built with today’s technology; however, there will be a myriad of designs leveraging spacecraft technologies – new technologies to emphasize strength and lightness, as well as tether materials that are not available today. One strength is that there are 60+ years of heritage in spacecraft design. This study report will address many questions such as;

Is the projected design achievable within the next 15 years? YES

Do we know enough to design a basic tether climber? YES, the tether climber is essentially a spacecraft with a special climber apparatus based upon terrestrial designs.

What are the special design requirements for the climber? Power sources and the interface between the tether and the climbing wheels.

How will the tether climber interact with the tether? Most current designs have opposing wheels using friction for traction. Externally supplied power will drive the motors which will turn the wheels as the climber ascends.

What are the demands the tether will put on the tether climber? General understanding exists; but, until characteristics of the tether are further developed, there is much to be analyzed and assessed.

What are the anticipated needs of the developer/owner/operator? 6 Metric Ton (MT) climbers with 14 MT payloads, one launch per day, one week trip to GEO, 7.5 years of life for each tether with 10 year MTBF for tether

Can we meet these needs? YES


Can the tether climber carry its own power source? NO. The current expected state of the art of materials will not allow the mass to generate and store energy to be raised against gravity, the power must be external.

Is solar or laser power preferable? Could be either, or a hybrid of both.



2012 Topic: Space Elevator Concept of Operations

Team Lead: Robert (Skip) Penny

Team Members: Dr. Peter Swan, Robert (Skip) Penny & Dr. Cathy Swan

From the Preface:


“This study report presents the current thinking on how a fully developed commercial space elevator will operate. It draws on the experiences of the study participants and the authors who have over eleven decades of major space system acquisitions and operations experience. While the development of Space Elevator tethers and climbers is a daunting task, their operation will leverage 50 years of satellite operations experience. The climber is essentially a satellite just like the thousands that have been launched to date. The authors conclude:

‘While the development of Space Elevator tethers and climbers is a daunting task, their operation will leverage 50 years of satellite operations. The climber is essentially a satellite just like the thousands that have been launched to date. The classic “telemetry, tracking, and command” functions for climber and tether operations will be the same as today’s satellites.’”

As shown in Figure 2, the Headquarters and Payload Operations Center (HQ&POC) will host key elements of conducting the business of transporting payloads to and from space. The business side will be the Enterprise Operations Center while the day to day execution of activities will be allocated to the various operations centers co-located within the HQ&POC. The Climber will be in constant contact with the operations center, capable of autonomous operation, and able to execute instructions from the Climber Operations Center. The GEO Node will be a satellite capable of remote controlled and autonomous operations just like the hundreds that have been functioning in the geosynchronous belt for years. The Apex Anchor will also be a satellite and its operation will be even simpler than the GEO Node. The Marine Node, comprised of the Floating Operations Platform and Ocean Going Vehicles, will leverage over 100 years of off-shore drilling operations.

Figure 2

Function Location

Enterprise Operations Center HQ & Primary Ops Center

Transportation Operations Center HQ & POC

Climber Operations Center HQ & POC

Tether Operations Center HQ & POC

GEO Node Operations Center HQ & POC

Marine Node Operations Center Marine Node

Payload (Satellite) Operations Center Owner’s Ops Center


Operations for a Space Elevator

Have NO Showstoppers

Have Reasonable Costs

Meet the Challenges



2010 Topic: Space Elevator Survivability Space Debris Mitigation

Team lead: Dr. Peter Swan

Team members: Dr. Peter Swan, Robert "Skip" Penny and Cathy Swan

From the Preface:

“Will space debris be a ‘show stopper’ for the development of the Space Elevator Infrastructure?


The answer is a resounding NO!

The elimination of the space debris risk with reasonable probabilities of impact is an engineering problem. The proposed mitigation concepts change the issue from a perceived problem to a concern; but, by no means is it a significant threat. This pamphlet illustrates how the development office for a future space elevator infrastructure can attack this problem and convert it into another solvable engineering issue.

The Big Sky Theory of Space Debris, or ‘what, me worry?’ has faded into the past just as Sputnik and the Saturn rocket. Space Faring nations recognize that the continuous growth [see Figure 3] of objects remaining in orbit has led to an arena where space debris collisions need to be addressed. During the study, the team addressed many issues to include:

The probabilities of collision between a space elevator and debris in Low Earth Orbit, in Geosynchronous Earth Orbit, and in Medium Earth Orbit.

The growth rate as it threatens an operational space elevator

A reasonable approach for space elevator developers to ensure infrastructure safety

Approaches to interrupt the sources of debris creation

Mitigation of risk for the space community through design, policies, operations, and lowering of the threat.

To assess the risk to a space elevator, we have used the methodology from the 2001 International Academy of Astronautics (IAA) position paper on Orbital Debris. Using the supplied formula, we calculated the probability of collision for LEO, MEO and GEO. Our focus is on LEO – as fully two thirds of the threatening objects are in the 200-2000 km altitude regime. Our hope is that this study will raise awareness of the problem (and spur action to implement policies and directives to mitigate and reduce the risk of collision) to the space elevator and all other users of the near Earth space environment. Our analysis shows:

‘The threat from Space Debris against the space elevator is manageable with relatively modest design and operational fixes.’”


Figure 3


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