hermes final technical paper (1)

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2016 Revolutionary Aerospace Systems Concepts –Academic Linkage

Habitable Environment for Research and Manned

Exploration of Space

(HERMES)

Victoria Coverstone1, Koki Ho2, Lui Suzuki3, Audrey Lee, Christine Mehr, Isabel Anderson, Guang Ting Lee,

Katherine Carroll, Kaushik Ponnapalli, Novoneel Chakraborty, Rick Wilhelmi, Robert Francis

University of Illinois, Urbana-Champaign, Illinois, United States of America

Hideaki Ogawa4, George Coulloupas5, Alexander Albrecht, Angus Mufatti, Chi Chun To, Daniel Chadwick, Ethan

Ross, Johnathan O’Neil Donnellon, Kristian Moore, Leann Vitug, Matthew Rozek, Victor Lim

Royal Melbourne Institute of Technology, Melbourne, Victoria, Australia

Final technical paper submission for the Earth-Independent 1G Space Station theme as part of the

2016 Revolutionary Aerospace Systems Concepts – Academic Linkage (RASC-AL) competition,

June 2nd 2016.

1 Professor, RASC-AL Faculty Advisor, UIUC Department of Aerospace Engineering. 2 Assistant Professor, RASC-AL Faculty Advisor, UIUC Department of Aerospace Engineering. 3 Local Team Leader, UIUC Department of Aerospace Engineering. 4 Senior Lecturer, RASC-AL Faculty Advisor, RMIT School of Engineering. 5 Local Team Leader, RMIT School of Engineering

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I. Introduction

The Habitable Environment for Research and Manned Exploration of Space (HERMES) is a long term

international effort to develop the infrastructure for a completely Earth-independent habitable system. The

mission architecture relies on a space station structure capable of simulating Earth’s gravity in a Moon orbit

and a lunar surface in-situ resource utilization (ISRU) base. This integrated system provides an environment

that can be colonized without the harsh conditions present in other potentially habitable location such as

the lunar and Martian surfaces. The station will be fully operational with 24 permanent crew members by

2040 and Earth-independent by 2045. A progressive build-up of the technology and infrastructure will begin

in the year 2015. HERMES will serve as a platform to demonstrate a safe, sustainable, and feasible step

towards permanent presence of humankind beyond Earth.

The space station will be a large ring structure with

a central hull and a passageway through the center for

structural integrity and accessibility. The station will

have a radius of 100 meters and will be an assembly of

smaller modules. It will rotate about the central hub in

plane with the ring simulating Earth’s gravity by the use

of centrifugal force. The space station will be assembled

in its lunar orbit from a combination of habitat modules

launched from Earth and modules built in orbit. A

modular design will be incorporated so that the station

can be built, assembled, and repaired throughout the

years of the mission.

The lunar mining base will consist of three

subsystems: the regolith mining rover, manufacturing

and processing base, and the material transport ascent-

descent vehicle. The rover will collect lunar regolith and retrieve the material to the manufacturing and

processing plant. There, the material will be processed into water, fuel, and metals. The ascent-descent

launch vehicle will then launch and rendezvous with the space station to transport the useful resources. The

lunar base will primarily be autonomous with crew coming down to the surface only when repairs are

needed to be done by humans.

II. Mission Operations

A. Timeline

The mission will begin in 2015 with research and development of the critical technology for HERMES

including the on-orbit construction and assembly of the station, and the material manufacturing and

processing systems on the lunar surface. The first decade will mainly be spent on precursor missions and

the launching of the equipment for the lunar base. The next five years or so will be spent sending the portion

Figure 1. Artist’s concept of HERMES in

operation.

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of the space station from Earth to the lunar orbit. Afterwards, continuing through the early 2040’s will be

the construction of the space station in orbit and the launch of supplies and crew to the station. In 2040, the

space station structure will be fully constructed and the it will be fully operational with rotation. The station

will continue to receive supplies from Earth until the end of 2044 when it will become completely Earth-

Independent. All of the events listed in the timeline in Figure 2 note the launch dates of each item and other

important milestones.

B. Orbital Mechanics

The space station will be placed in an orbit 150 km frozen orbit around the Moon with an inclination of

86 degrees. Frozen orbits are characterized by keeping the argument of perigee and the eccentricity of the

orbit constant [1]. By doing this, the space station always passes over a given lunar latitude with the same

altitude. Since the lunar mining base will be located near the pole of the moon, the distance from the base

to the space station will remain constant at each pass. An additional benefit to this orbit is that it drastically

reduces the amount propellant required for station keeping, since that process occurs naturally due to the

perturbations caused by the oblateness of the Moon.

1. Station-keeping orbit

Utilizing an automated process chain, a

computational trade study was conducted to

determine key design factors involved with the

first orbital state for the beginning phases of on-

orbit operations around the Moon. Combining

numerical integration by the means of Systems

Tool-Kit (STK) and surrogate assisted

evolutionary algorithms (MATLAB), multi-

objective design optimization was conducted for

two objectives; duration of flight on orbit until at

least one destabilization criterion are met, and the

summation of the magnitude of ∆V (impulsive

maneuvers) required to correct the orbit. The

intention of the study was to determine an orbital

state corresponding to optimal performance as

characterized by the objectives. That is, a stable

orbit with a long time of flight in orbit as well as

optimally performing corrections. Thus, the

decision variables were orbital elements n (mean

motion), i (inclination), Ω (right ascension of

ascending node), e (eccentricity) and ω (argument

of latitude) as well as Ep, orbit epoch.

The results of the analysis include a high

number of high-performing and feasible orbital

states. Of the 4608 evaluations performed, 2551

were feasible. One such orbital state and target

epoch, capable of a time of flight of 110 days,

requiring an optimal ∆V for correction is included below. Figure 3 which follows, also characterizing the

trade-off relationship with a pareto-front. It is said, non-dominated results are optimal solutions as no other

minimized or maximized results for the objectives exist with respect to one another.

Destabilization

criteria

Eccentricity 1% increase

Periapsis & apoapsis

altitude

± 5%

Experimental design

Objective functions f1 = min (∑|∆V𝑥,𝑦,𝑧|) &

f2 = max(time of flight)

Decision variables 0.0436 < 𝑛< 0.0499 [deg/s] 0 < 𝑒 < 0.05 85 < 𝑖 < 87 [deg] 0 < 𝛺 < 360[deg]

0 < 𝑢 < 360 [deg]

1 Jan 2029 12:00 < Ep <

31 Dec 2030 12:00 UTCG

Constraint function f2 > 14 days

Evolutionary

algorithm parameters

N Generations = 48,

N Individuals = 96

STK parameters Propagator: Moon High

Precision Propagator v10

(48 degree, 48 order) with

Sun, Earth point-mass.

Table 1. Multi-objective design optimization

summary.

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2. Earth to Moon transfer trajectories

The initial stages of the mission will be

constructing the lunar base to make a start on

resource collection before any humans will arrive.

Earth to Moon transport of humans must be

completed in a very short time to reduce the radiation

dosage hence a, high thrust transfer be used. The

transfer time required to transport the lunar base

resources is not heavily driven by the radiation dosage, therefore a longer transfer trajectory can be used.

The initial lunar base resources such as machinery, raw materials and other essential items weighing a

combined total of 25 tonnes can be on board each launch and sent to the moon by the Space Launch System

(SLS) [2]. This mission will primarily use the various SLS vehicles as they are developed to transport

supplies and the Orion Multi-Purpose Crew Vehicle for crew transfer. The payload will be put into a highly

elliptical orbit with an apogee of 42,164 km and perigee of 6978 km, from this point there are two

trajectories that it could take.

The first is to complete an impulsive maneuver to place the payload into a geosynchronous orbit to

perform in-orbit diagnostics, then complete a low thrust circular spiral transfer out to get captured by the

moon. This transfer would take approximately 6 months to complete using a 200 kW Variable Specific

Impulse Magneto plasma Rocket (VASIMR) by Ad Astra Rocket Company [3]. The SLS upper stage will

be modified to use this technology for this mission. By using Xenon as a propellant the engine is able to

produce 5N of thrust and a specific impulse of 5000s [4]. This VASIMR unit is currently TRL 5. The

advantage of using the VASIMR unit is that it can be repurposed as the Isp is variable, or the nuclear reactor

could also be used as an energy source in the initial stages. The transfer time may decrease if spacecraft

propulsion technology has major advances between now and the launch date.

The second trajectory would be to stay in the highly elliptical and also use the VASIMR engine to

perform thrust arcs around the perigee to gradually increase the apogee. Once the apogee is within the

sphere of influence of the moon the payload will be transferred to a lunar orbit. This trajectory will have a

short transfer time, and by thrust arcing the fuel usage is much lower. The downside is there is no stable

orbit to perform the in orbit diagnostics. This trajectory has not been modelled, however using data from

previous missions such as ESA’s SMART-1 probe [5] assumptions and calculations can be made. There

will be a high number of resource launches required and both of these trajectories are feasible so each

mission can be tailored specifically to the payload.

C. Budget

The budget for the HERMES mission is based upon the NASA 2016 fiscal year presidential budget

request of $18.5 billion through the end of the mission without adjusting for inflation [6]. ISS will be fully

funded at current rate until 2024, when it will be decommissioned. SLS and Orion will continue to be

funded but with a 30% budget reduction after 2030. A 20% budget reduction of all non-mission NASA

projects results in $1.49 billion per year through 2024, $5.23 billion per year from 2025 to 2030, and $6.21

Objectives f1 = 6.185 m/s, f2 = 110.5 days

Orbital

state

Apoapsis altitude = 370.68 km

Periapsis altitude = 229.17 km

Eccentricity = 0.03473

Inclination = 86.13º

RAAN = 142.68º

Arg. Of Lat. = 262.13º

Target Insertion Date:

22nd Dec, 2029 21:46:45 UTCG

Figure 3. Multi-objective design output. Table 2. Objectives and orbital elements.

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billion per year after 2031. This totals a lifetime budget of $125.1 billion for this mission from 2015 to

2045. From this amount, a total of $164M was budgeted to Research, $14,500M to SLS Launches [7],

$1,200M to BA-330 Modules [8], $10,221M to moon related operations and $98,990M to the HERMES

Station. The HERMES budget has a minimal margin between available and used amounts of 2.31%

occurring in 2019, a maximum margin of 11.1% occurring in 2028 and an average margin of 5.66%. A

detailed distribution of the total budget year to year of different systems for the HERMES mission can be

seen in Figure 4 below. The costs below depict the cost to NASA, excluding the costs to other partnering

organizations as explained in the following section.

D. International and Commercial Partnerships

Similar to other large scale space programs, HERMES will rely

on international and commercial partnerships. NASA will lead the

HERMES program in cooperation with Europe (ESA), Russia

(Roscosmos), Japan (JAXA), Canada (CSA), and China (CNSA).

These partners were chosen based on their program budgets and

technical value to the mission [9].

The United States will barter crew seats on the space station in

return for services towards the mission. In the past, similar trades

have been conducted for projects such as the ISS and Cassini-

Huygens [10]. HERMES will have 24 total astronauts from the

participating organizations and the distribution can be seen in the

chart to the right. NASA will be responsible for the construction, assembly, and supplying of the station

structure. Meanwhile, ESA will develop the material processing and manufacturing station on the moon,

Roscosmos will design and build the ascent-descent vehicle, JAXA will create the lunar mining rover,

CNSA will manage the cis-lunar satellite communication network, and CSA will work on the robotic arm

attached to the outside of the space station. These tasks were based upon the available budget of each space

agency and their strengths that could be useful for this mission.

Figure 4. HERMES mission budget breakdown from 2015 through 2045.

Figure 5. Crew distribution on

board the space station

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The different nations will work closely with NASA which will provide budgetary aid to the

corresponding space agencies, as shown mission budget for NASA, but each country is expected to make

a significant monetary contribution for the mission as well.

In addition to the international partnerships, commercial partnerships will be sought in forms such as

mission data purchases and on board experiment opportunities through the first 5 non-independent years.

Also, partnerships with commercial entities such as Bigelow Aerospace, Moon Express [11], Shackleton

Energy Company [12], and the Google Lunar XPRIZE [13] will greatly reduce the costs of development

on NASA for the HERMES technology and infrastructure. These organizations interested in lunar mining

and space habitation will receive NASA contracts and also invest their own money into the research and

development of mission essential technologies.

E. Research and Development

For estimating research costs, low TRL components of HERMES were considered. Specifically, lunar

resource manufacturing processes, lunar nuclear power generation, extended life support system, in-orbit

3D printing, and lunar mining robotic technologies. Such research costs were estimated from transition

costs between TRL levels for their respective technology area [14] [15]. Specifically, each research

component was given an initial TRL level based on current literature and experiments and costs were

estimated as a transition to TRL level 9.

For cost estimation of low design inheritance systems, the JSC NASA Advanced Missions Cost Model

[16] was used. In estimating the costs for the individual lunar systems and space station, historical mission

data of similar systems was used as an input to the model and the outputs were scaled by an overhead factor

of 1.2 to account for indirect costs. All costs were inflation-adjusted to FY16 $USD using the US Inflation

Calculator [17]. The lunar rover’s cost was estimated using historical data as it is a high design inheritance

system.

The timeline of pre-independence was categorized into five general objectives with their respective

qualitative risks: launch vehicles–very high, lunar surface deployment–high, orbital deployment and

rendezvous–moderate, manufacturing–low, and research and development–very low. A joint cost and risk

analysis was performed on the

mentioned objectives throughout

the duration of the mission timeline.

The financial detriments of each

risk is the budget appropriated to the

respective objective for that year. It

was found that the most prevalent

risk was the launch vehicles,

specifically the SLS, as it appeared

consistently throughout the mission

timeline. In the case that such a risk

occurs, the financial effects will be

mitigated through the budget

margin, as well as possibly through

partnership support.

F. Cadence Missions

To make this mission a reality, the technology must first be developed and proven through smaller

objectives. Cadence missions will be planned to prepare for the construction of the space station. First,

because HERMES relies greatly on the SLS and Orion MPCV, test missions of these technologies are

required. NASA currently has three main missions planned with the SLS and Orion. Exploration Mission

1 (EM-1) is planned for November 2018 to prove SLS and Orion in deep space environments. It will place

the Orion in the lunar Distant Retrograde Orbit (DRO), which will provide data about the moon valuable

to HERMES [18].

Figure 6. HERMES yearly risks to the mission budget

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EM-2 will launch crew into the DRO and will also carry a CubeSat as a secondary payload. This CubeSat

would be equipped with a dosimeter in order to observe the radiation levels experienced and would also

serve as a method to verify the trajectory design [19]. EM-3 will analyze an asteroid put in DRO by the

Asteroid Redirect Mission (ARM) [20]. The funding for the Exploration Missions are already included in

the SLS and Orion cost within the exploration budget [21]. The ARM, however, will need to be funded

additionally by an estimated $2.6 billion [22].

Another component that the HERMES mission relies on is the Bigelow module. As such this technology

must also be tested in space. The test, planned for 2017, would be verifying deployment of two of the

modules in LEO, allowing for the added benefit of the ability to test the in orbit assembly technology as

well.

The lunar mining rover technology is also one that needs to be tested. A mission planned to begin in

2019 would launch a scouting rover. The rover would serve as a test for lunar surface technology and would

allow for the verification of both the physical design of the rover and its communication system.

III. Space Station

The space station will be assembled in the lunar orbit, designed to simulate the gravity environment of

Earth and eventually support 24 crew members. The gradual build-up of the space station will incorporate

a central hull, central axis, 8 Bigelow BA-330 habitat modules, and modules constructed in space. Human

beings can adapt to levels of up to 3 rotations per minute and with the 1G requirement, the radius was

estimated to be approximately 100 meters [23].

The modules building up the space station will be circular and will have an outer diameter of 6.7 meters

based on the dimensions of the Bigelow BA-330 modules [24]. The usable space within the module will be

a square cross section of 4 meters by 4 meters. This defines the total usable volume of the station to be

approximately 10050 cubic meters and the total floor space to be approximately 2500 square meters. The

space inbetween the outside and the usable volume

inside will be filled with lunar regolith, water, and other

materials to be stored to serve as radiation protection.

In times of severe radiation dosages such as at times of

solar flares, crew members will concentrate in the BA-

330 modules which are properly shielded for extreme

occasions.

A significant portion of the space station will be

constructed in orbit about the moon. A crucial part of

this mission is the advancement of technology in 3D

printing in orbit. A satellite 3D printer with robotic

arms, similar to the SpiderFab by Tethers Unlimited,

will be used to manufacture the metal modules [25].

The satellite will extrude metals obtained from the lunar resource base and move around with robotic arms

to operate. A significant amount of time and money will be spent to develop this technology. Multiple of

these robotic 3D printer satellites will be used to develop the HERMES space station.

G. Assembly Process

The construction of the HERMES station shall involve a number of distinct phases, providing periodic

testing to validate and verify the employed manufacturing processes and techniques, in terms of long-term

operations and structural integrity.

Before any assembly of the station will be the deployment of the lunar ground station to begin its

material collection and processing operations. The phase will begin with the deployment of the lunar rover

on the lunar surface where it will undergo verification and validation to ensure that it is capable of gathering

the lunar regolith. The second stage of the lunar operations will be the delivery of a materials refinement

lab capable of refining the lunar regolith brought by the rover into useful resources. The testing phase of

the refinement facility shall be rigorous to ensure that the useful materials are successfully and efficiently

Figure 7. “SpiderFab additive manufacturing

and assembly on-orbit” [25]

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produced. This phase shall conclude with the testing of an orbital delivery system that can transport

payloads from the lunar surface to rendezvous with the station. From the lunar resource base, the station

will receive water, regolith for radiation shielding, and metals for constructing the space station modules.

The first phase of construction will be the central hub that will be at the core of the ring structure. This

hub will be manufactured on Earth and launched to insert into the desired lunar frozen orbit. As part of the

station, this hub will serve as a rendezvous point for supplies from Earth and the lunar base. Once the hub

is set in the orbit, the on-orbit 3D printing robot will construct the passageways from the hub to where the

outer ring will be. Stage 1 will consist of the hub, one segment of the passageway arm, and a collection of

4 Bigelow BA-330 modules will be attached to the end of the arm segment.

Phase two will continue the work of creating a

symmetrical arm segment from stage one. It will continue

to print the modules on the opposite side of the hub where

another group of 4 BA-330 modules will be attached. As

this process continues, resources such as the metals for the

3D printers, water, and regolith will be brought up to the

station and stored in the available volume.

Phase three shall see the construction of the outer ring

using building materials delivered from the lunar base.

This period will act as a proof of concept for orbital

manufacturing and construction and the final structure

will be subject to rigorous testing to ensure the structural

integrity of the finished structure. The multiple 3D

printing robotic satellites will continuously operate to

construct the entire station ring structure.

Phase four will focus on the station’s self-sufficiency

and culminate in the gradual ceasing of Earth resupply

missions as the station becomes Earth independent.

During this stage many of the final modules will be

complete and the ring’s rotation will increase incrementally to ensure the stability of the ring and its

structural integrity. During this period, all life support and food management systems will slowly be

expanded and the crew roster will slowly be expanded to 24 crew members to ensure that systems are in

place to cope with the increasing loads on the on-board systems.

Figure 8. Assembly of BA-330 modules and

modules manufactured in orbit

Figure 9. Sequential build-up of the space station in orbit

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H. Propulsion System

In order to determine the propulsive requirements of the space station, the mission profile must be

understood. A single system is planned on being used for station keeping, emergency orbital maneuvers,

and for attitude and rotational control.

1. Attitude and Rotational Control

Initial calculations have been done to assess the thrust requirements for the initial spin-up cycle to the

desired 3 RPM with a trade-off study completed between thrust and days required. For these calculations

the moment of inertia and torque required were based upon the estimated mass and geometry of the

HERMES model. Once the space station is in rotation it will experience levels of precession, which will

alter the attitude of the station and can have negative effects on the crew from the sideways forces [26].

However, the amount of precession experienced is quite minimal due to the rotational velocity of the station

and therefore will produce negligible effects in the short term.

By increasing the spin-up cycle timeframe the

thrust requirements decrease significantly from

over 500N for 1 day down to 54N for ten days. The

force required can be seen in Figure 10 to decrease

exponentially with time). The goal is to combine

the spin up propulsion system and the precession

correction system requirements together to

optimize the position and number of the thrusters

to be able satisfy both. For maximum rotational

thrust the thrusters shall be positioned pointing in

the direction of rotation on the outside of the outer

ring whilst the procession correction thrust shall be directed perpendicular to the rotational plane. For this

to be possible each thruster will have 360 degrees of freedom in their yaw axis to adjust the thrust vector

as desired. The thrusters will be placed at maximum 90-degree intervals around the outside of the station

(minimum 4 thrusters), more may be needed depending on structural considerations.

2. Emergency Maneuvers

To ensure the long term survivability of the HERMES mission possible disaster scenarios need to be

considered. Collisions with small solar system bodies (SSSB) pose a very real threat to the longevity of the

habitat. Integrating emergency propulsion with a system for the detection and tracking of hazardous objects

will function to minimize the risk. The tracking system will additionally serve as early warning for that

which is situated on the lunar surface but also could have the potential to relay information back to Earth

as well.

3. Thruster Operation

The HERMES propulsion system shall utilize resistojet thrusters and the lunar water as propellant. This

approach will reduce system complexity and associated risk while increasing reliability as there is no need

for onboard cryogenics or cautionary measures to be taken with regard to combustion or explosive

materials.

Resistojets have been studied extensively for the application of attitude control on smaller satellites with

many successful technology demonstrations [27]. The resistojet is a mechanically simple and low cost

design with the propellant being heated by a resistive element then expanded through a convergent-

divergent nozzle. The simple design will allow for low maintainability requirements and possibility for in-

situ thruster manufacturing. Resistojets can operate with a wide range of propellants like hydrazine,

hydrogen, methane, water, air, ammonia and many more [28]. This range of propellant versatility provides

a high level of redundancy in the event that the primary fuel stores are depleted. The primary source of fuel

will be water due to the high availability on the lunar surface and ease of storage.

Current resistojet technology is able to provide and Isp range of 200 – 350s and a thrust range of 200 -

300mN with overall efficiencies between 65-90% [29]. Due to the high thrust requirements of the station

spin-up cycle the thrusters will be scaled up to provide 13.3N of thrust each to satisfy the 54N of thrust for

a 4 thruster configuration and a 10-day spin-up cycle. The spin time was chosen as it represents an

Figure 10. Force required for spin-up cycle

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approximate optimum between force required to rotate the station, input electrical power while minimizing

the propellant mass. Too long of a burn and the mass expelled becomes prohibitive, too short and the

electrical power required is prohibitive (in the megawatt range). Based on the thermodynamic relations for

convergent-divergent nozzles presented in [30], [31] and [32] the following thermal rocket engine was

developed.

Table 3. Nominal thruster operation.

Unit Value

Thrust N 13.37

Mass Flow Rate g/s 6.4

Specific Impulse S 206.9

Chamber Conditions

Pressure kPa 101.325

Temperature K 1500

Nozzle Geometry

Throat Diameter mm 10

Exit Diameter mm 40

Expansion Ratio Ae/A* 16

Total Operational Costs (4 Thrusters)

Burn Time Days 10

Propellant Mass (Water) kg 22,234

Electrical Power (50% efficiency) kW 154.1

The thruster geometry here is far from optimized in terms of specific impulse, expansion and power

usage and future work on this system should involve optimizations and analysis of disaster scenarios and

manufacturing analysis. The geometric specifications were obtained using isentropic compressible flow

relations and have not taken into account thermal losses and efficiencies. Estimated energy conversion

efficiencies were used in the calculation of electrical input power (50% conversion efficiency). Not taking

flow losses into account this equals a 70.4 % efficiency in converting electrical power to jet power, which

has been demonstrated to be feasible in water propellant resistojet thrusters [33].

Due to the operation requirements of the thruster the internal chamber pressures were limited to 1

atmosphere and a chamber temperature of 1500 K. This aimed to reduce the materials requirements and

increase thruster lifetime. It is envisioned with the current drive for reusable rocket technologies the

development of thermal engines that can repeatedly perform for the extended periods described is within

the realms of feasibility in the next 20 years.

The thruster will be placed radially on the structural ring. The propulsive system is designed to operate

with a minimum 4 thrusters therefore a minimum of 16 thrusters equally spaced (22.5 degrees apart). This

arrangement with each having a freedom of yaw control will be able to provide 213.92 N of thrust

perpendicular to the rotational plane of the HERMES.

I. Power

The space station is estimated to require 1.25 MW of energy, which means about 11-13 km2 of the

exterior will be cover with solar arrays. These will placed on the surface of the station facing the rotation

vector, since this is the direction that will be facing the sun at all times.

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The space station will be completely dependent on solar power to meet its energy requirements.

Specifically, the power will be provided by an array of concentrated crystalline photovoltaic cells. These

cells have an efficiency of 119.5-179.8 W/m2. The solar arrays will charge a bank of Ni-H batteries due to

the long shelf lives. These batteries will act as generators when the space station is eclipsed. They will also

act as an APU, discharging auxiliary power to systems that require more power. The specific discharge will

be controlled by an algorithm that monitors the station’s energy requirements and outputs. This system

serves a backup to maintain life-support and other crucial systems during eclipses and other losses of solar

power.

J. Thermal Management

Heat build-up within the HERMIES could pose an issues to astronauts if it is not dealt with

appropriately. In contrast to habitation systems on Earth with conductive and/or convective dissipation

methods, HERMES shall feature a novel system to meet thermal dissipation requirements, drawing use of

thermal energy regarded as waste. One proposed method to satisfy this requirement involves utilizing the

outer hull of the station augmented with thin aluminum ribbons whose exposed length and orientation are

variable, behaving as a passive radiator to the external space environment. Although, sustainability

concerns exist surround the long-term reliability and effectiveness of this system. Alternatively, the

application of thermoelectric generators to convert waste thermal energy into stored electrical energy has

been considered. The efficiency of these generators are proportional to the exposed temperature differential.

Thus, it is thought a small portion of the radiation shielding water jacket may be used as a convective heat

sink, thus acting as a hot reservoir, cooled by radiation to the external space environment in substitute of

an augmented cooling approach.

IV. Environmental Control and Life Support Systems

To make the HERMES station a habitable and sustainable ecosystem, the environmental control and life

support systems will be integrated with each other and with the resource supply from the lunar surface base.

Food, water, environmental control, safety, and exercise systems will be incorporated, oriented towards the

safety and well-being of crew members as well as economic feasibility and efficient use of resources.

K. Food Production

For the space station to be Earth-independent and sustainable, the crew will grow their own food within

the station. Their crew will consume a vegetarian diet consisting of hydroponically grown vegetables.

Essential nutrients for health including carbohydrates, protein, fat, vitamins, and minerals were considered

when deciding which vegetables to grow on the station [34]. Beans, beets, lettuce, peas, and potatoes will

be the main vegetables to be grown. In addition, smaller amounts of tomatoes, broccoli, cucumber, cabbage,

carrots, eggplants, and other various vegetables will also be grown hydroponically [35]. These vegetables

were chosen based on their nutritional value and ease of growing hydroponically.

To calculate the amount of tray space needed for the hydroponic growing equipment, a few assumptions

were taken. Potatoes will be the primary crop grown because of its high calorie content and the calculations

for growing space will be based on the potato plant. In a hydroponic garden, it is recommended to grow

two potato plants per square foot [36]. On a single plant, a

minimum of five potatoes are expected to grow and each

potato, assuming they are average sizes with a diameter of

about 3 inches, will provide about 160 calories [37] [38]. An

average needs about 2500 calories per day and there will

eventually be 24 crew members on the space station [39]. A

potato plant can typically fully grow in 70 to 120 days in a

regular soil environment. In general, hydroponic growing

environments grow crops more easily because of the

sufficient nutrients, water, and light but it will be assumed

that the plant will grow in 120 days [40]. Assuming that

Figure 11. Hydroponic farming system

layout [42]

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potatoes are the only source of calories, an area of about 450 square meters is needed to feed the entire crew

for 120 days plus 10 days for the transition period between planting. Giving an additional margin, a total

floor space of 800 square meters, or about a third of the space station, will be reserved for the hydroponic

farming equipment. Plants can also be grown using two layers of planting beds to optimize spatial

efficiency.

The hydroponic system will require growing lights, air pumps, and water pumps. In total, the equipment

for one 4-foot by 4-foot unit will require about 250 watts [41]. This means that in total, the entire hydroponic

system should take about 12.5 kW of power in total. Each unit will also have a water reservoir which will

be filled with water retrieved form the surface of the moon on the base. Most of the components such as

the tray, reservoir, pumps, and airstone will be sent in the supply launches from Earth. A large excess of

amounts of each component will be sent and put in storage so that these components can be replaced once

they need to be replaced. Further on, these components will be manufactured on board the space station

with 3D printers using metals retrieved from the lunar surface. Initially, nutrients for the hydroponic system

will be sent in the supply launches from Earth but it will later be replaced by organic waste from every day

use of the station.

In addition to traditional hydroponically grown vegetables, other more experimental forms of

sustainable food providing methods will be applied. This includes things such as in vitro artificial meat,

insects, small fish, and algae. Also, different methods of providing the hydroponic system nutrients will be

experimented with including methods such as fish, different kinds of bacteria, creating a nutritious soil

solution, and creating a nutrient providing aquarium.

The crew members will initially eat typical astronaut foods sent from Earth in the initial years while the

space station is being constructed. As the station’s outer ring expands, crew will set up the hydroponic

systems on board the station. The types of vegetables grown will be cycled so the crew can have a variety

of foods. There is an excess of growing space so the crew can grow a surplus and store them by vacuum

packaging or refrigeration and consume them at a different time. The hydroponic system will be able to

operate autonomously but crew members will closely monitor the growth of the crops.

L. Water

The water recovery system (WRS), based off of the system on the ISS, provides clean water by

reclaiming waste water from sources such as crew member urine, cabin humidity, and hydroponic system

waste. The purified water is required to meet stringent purity standards before it can be used as clean water

by the crew. The WRS reduces the net mass of water and consumables needed to be brought to the space

station by 15,000 pounds to support a six-member crew for a year. The WRS consists of a Urine Processor

Assembly (UPA) and a Water Processor Assembly (WPA). A low pressure vacuum distillation process is

used to recover water from urine and the water recovered is combined with all the other wastewaters and

delivered to the WPA. In the WPA, the water is separated from solid and gas materials before going through

a series of multi-filtration beds for purification. Any remaining organic contaminants and microorganisms

are then removed by a high temperature catalytic reactor assembly. Lastly, the purity of the water is tested

by electrical conductivity sensors and water of unacceptable quality is reprocessed while clean water is sent

to a storage tank [43].

Water will be recycled as much as possible on board the station to minimize the amount needed to be

transported up to the station from the lunar base. Water circulating through the hydroponic system will

periodically be replaced with new water retrieved from the lunar surface. The old water will be purified and

repurposed for other uses on board the space station.

M. Oxygen Generation System

The Oxygen Generation System (OGS) produces oxygen used by the crew and replacement of oxygen

lost due to activities on the station similar to the ISS. The system consists of the Oxygen Generation

Assembly (OGA) and a Power Supply Module. The OGA consists of a cell stack which electrolyzes water

provided by the WRS to produce oxygen and hydrogen. The oxygen produced is delivered to the cabin

atmosphere while the hydrogen is vented overboard. The OGS is able to generate oxygen at selected rate

13


and is able to provide 5 to 20 pounds of oxygen per day during continuous operation. The temperature and

humidity in the station is controlled by the Thermal and Humidity Control subsystem, which regulates by

removing heat and humidity and provides air circulation [44].

The large amounts of plants growing within the station will affect the level of regulation of oxygen and

carbon dioxide in the station. However, the amount of each gas consumed and produced by the plants and

crew vary greatly. The oxygen and carbon dioxide content of the station will be closely monitored and any

excess of deficiency of both the gases will trigger the atmospheric regulation equipment to address this

issue.

N. Crew Health & Safety

To ensure the health of crew living on the station for extended amounts of time, there will be plenty of

opportunity to exercise on board the station. Because the space station will be under influence of a simulated

Earth gravity, there is no concern of bone and muscle loss caused by a zero gravity environment like on the

ISS. However, exercise is an important part of a healthy lifestyle.

Because artificial gravity will be present on the station, regular exercise equipment used on Earth could

be used such as treadmills, exercise machines, and weights. However, the exercise equipment on the space

station will also be able to operate in zero-gravity environments so that crew can exercise when the station

is not rotating. Resistance exercise equipment similar to those aboard the ISS will be implemented in the

space station’s exercise room. This will allow crew to maintain their bone and muscle strength while the

station is being built up and while the station is not rotating in special occasions.

The HERMES space station will have extra-vehicular activity (EVA) capabilities for recreational use to

the crew as well as for when repairs are needed on the external surface of the space station. To allow EVA’s,

the station will have multiple airlocks and an extensive systems of railings on the outside of the station

structure for crew to harness onto. The station will have periodic airlocks and spacesuits located at these

airlocks spread evenly across the ring of the station. This will allow crew members to swiftly get into their

spacesuits into a safe, contained environment in cases of emergencies in the space station.

Safety measures will be considered during the construction of the space station to ensure that the crew

can safely live in the station. There will be redundancies in all of the essential life support equipment such

as the WRS and OGS as well as spare parts in storage. The modular design of the space station allows each

module to be separated from the rest of the station with a door. This segmentation of the space station will

be important to the safety of the crew in emergencies such as fires, unpressurizations of modules, and

contamination.

V. Lunar Base and In-situ Resource Utilization

The moon has an abundance of resources that can be taken advantage of to successfully build and supply

a 1G space station. A key resource that needs to be extracted is water. Water ice deposits are speculated to

be present at both lunar poles (1,2,3). It is estimated that 600 million cubic meters of ice water exist in

craters at the poles (2). Water is not only important for sustaining the people in the 1G space station, but

also useful for fuel, hydroponics, and possibly protection from radiation. It was discovered that 2 grams of

water could be extracted from 200 grams of regolith with one watt of power (5). Silicon will be necessary

for creating solar panels for power. Aluminum, iron, and titanium will be useful for repairs and other

components of the space station. Some regions have more of a certain material than others, but all are

accessible from regolith (Figure 3, 2). Silicon has about 20 weight% in regolith while titanium has around

5-8 weight%. Aluminum is not rare, as it is anywhere from 7-14% of the composition of regolith while iron

is 14-17% of regolith.

14


O. Communication System

The communication system on the lunar base is the bridge between the HERMES and the Earth-based

communications satellites, required for all the activities on the lunar surface, will be responsible for

tracking, resource management and logistics coordination.

Lunar Base Antenna (LBA) is mainly used for communication between the Earth Center and the Lunar

base and will serve as the main communications relay between the HERMES and the Earth. A high data

rate is required for the LBA (>10Mb/s) because it will be handling the majority of the telemetry dataload.

A single antenna on the Lunar base will minimize cost and feature a large capacity for data transfer as it

will be required to facilitate all of its functions. The antenna supports communication between the

HERMES, Lunar base, Earth Center and the astronauts on the lunar surface as well as the management of

the Lunar Positioning System (LPS) and the automated mining rovers. The Antenna is first manufacturing

task on the Lunar base, using the ore and the 3D printer for the development of dish and tower structures.

The signal transmitter is manufactured on Earth due the complexity of the electronics required for

functionality.

The Lunar Positioning System provides communication network for the lunar orbit that consists of a

constellation of miniaturized satellites. The main mission of the constellation is terrain mapping to be

carried out at an altitude of 150 km above the lunar surface. The satellites can deliver updated surface

imagery with a period of 14 days. The positioning system required 3 orbital planes for constant

communication. Each plane has eccentricity of 0.185, inclination of 40 degrees, and semi-major axis of 150

km. The Right Ascensions of Ascending Nodes for the planes are 310 degrees and 180 degrees. The

minimum target of the system is the minimum coverage of 80% of the moon surface, where north pole and

south pole required less coverage since most of the mining activities and Lunar base location are focus on

the equator of moon. The satellites carry wide angle camera and laser ranging instrument for mapping

system. The maximum range for the current photography technology is approx. 150 km, which is the

targeted altitude for the satellite. The second function of the LPS will be to provide constant

communications coverage of the entire lunar surface. The satellites are planned to be built on Earth because

the systems are complex. Compared to the manufacturing process on moon, the cost is significantly reduced

because of this process alone. Furthermore, the propulsion requirements for the satellites are less without

launching to the prescribed orbit by itself from the lunar surface. The mass of each satellite is estimated at

20kg including payload.

Figure 12. Lunar communications network.

15


P. Power

Sustainable power systems are key for the longevity of the Lunar Base. Solar energy is a key source of

electrical power but is an intermittent resource and logistically costly to scale for large power requirements.

Nuclear power is an alternative that can be developed for use on the lunar surface with light mass reactor

systems deployed for high power consumption activities. The power consumption of the Lunar base

includes the life support system, mining activities and the communications network. The application of

solar power and nuclear power can support the lunar base power consumption about 20kWh. Solar power

generation on the moon is significantly more effective than on Earth due to the lack of atmosphere. The

first generation of solar panels will be manufactured on Earth, however after the initial station deployment

the capability to manufacture and repair them on the lunar surface. Solar power is the primary source of the

power supply with nuclear power providing auxiliary support.

Current solar technology can provide approx. 100 W/m however this is expected to improve. Due to

regolith build up on the solar surface, automated cleaners will need to be in place to sustain high efficiency.

During times of darkness (two weeks), a cover will be automatically placed over the panels to ensure no

unnecessary regolith build up. Nuclear power will be required for use on the lunar base during the periodic

14-day stretch without access to solar power experienced at the facility location The reactor design will be

based on radioisotope thermoelectric generator technology, which has proven flight technology on several

space missions. The heat power for starting up the reactor is produced by the Solar panels, the reactor will

not be activated in Earth orbit due to safety concerns, however the assembly will take place on Earth.

Q. Resources and Methods

Due to the HERMES Project being Earth independent, resources are limited, orbiting the moon and

utilizing its natural resources are best chances for the satellite and its inhabitants have at succeeding.

Excavation tools are to be intelligently and autonomously designed to minimize risk of any live crew and

work efficiently. Based on multispectral imaging of the near side of the lunar surface, the compositional

properties of the regions analyzed present resource abundance levels in locations such as western Mare

Tranquilitatis which displays the highest levels of Titanium Dioxide (TiO2) [45]. Areas of high TiO2

abundance are probably rich in a resource known as ilmenite (FeTiO2) which can be utilized for its valuable

iron content [46]. Other commodity types, where they are found, and in what form were summarized in the

table below [47].

The data in the Table 4 of the appendices only specifies landmarks of interest that could contain said

resources, however, this broadens the scope of potential sites to encompass numerous new areas of interest

on both the near-side and far-side of the moon. The Clementine mission, launched in 1994, completed

element mapping (iron, titanium, thorium, etc.) of the lunar surface and came up with high abundances of

each element signature on the western near-side of the moon, or Oceanus Procellarum.

Initial stages of the Lunar Base incorporate heavy use of a Bigelow module in the preliminary stages before

the base is fully autonomous. Two Bigelow modules will be used as the initial crew habitat. The solar panels

pre-set on the Bigelow module may prove unnecessary, as additional solar panels will be installed on the

lunar surface but shall remain to provide redundancy. The module will be sunken into the ground to provide

protection from weathering effects. Incorporation of additional air locks provide the crew with another

means of exiting the module in high risk and emergency cases, also for higher connectivity between

modules.

Radiation shielding will come in the form of lunar regolith. Silicon dioxide found within the material

forms into a crystalline-glass structure under microwave influence [48]. The amount of radiation shielding

upon the bigelow module amounts to approximately 203cm of lunar regolith [49].

A section will house all the manufacturing processes the lunar base experiences. An inflatable module

will be incorporated with the aid of structural reinforcements in the form of the crystalline regolith. The

manufacturing sector will not be pressurized as the sector will be for robotic activity only. The sector will

be located inside a warehouse type structure approximately is 50m2 to protect the machinery from the

abrasive lunar dust.

16


The Moon-bot is designed to be autonomous in collecting materials for satellite and lunar base

construction. Working in conjunction with the communication system between the micro satellites,

HERMES and the Lunar base antennas. It receives data about the lunar surface while simultaneously

mapping topological change as the Moon’s surface is excavated. It records and maps the material

composition during it operation. The lunar rover shall also store onboard navigational data should

communications with the Lunar Base or LPS be severed. The bot will utilize a loader Bucket made of

Tungsten Carbide, which will need to be delivered in the initial launches from the Earth as the first

excavation rovers will be required to stay operational until the capacity to manufacture them has been

developed. The rover will ally high pressure to the collected regolith to compress it into to a brick shape in

preparation for use as a construction element. These bricks will be assembled to provide the basis for

structures and radiation shielding but can be easily stored to await processing.

Through molten oxide electrolysis (MOE), it’s possible to obtain materials like iron, aluminum,

titanium, and silicon from regolith without pretreatment. Water can be extracted surface regolith through

microwaves heating.

Rocket propellant manufactured on the lunar surface will be vital for the sustained operation of the

resource and structure delivery system. Propellant will be derived through electrolysis from water harvested

on the surface. However preliminary missions to the lunar surface to develop the technology will be

performed.

VI. Conclusion and Future Capability

The HERMES space station and lunar base infrastructure

will serve as a large step towards the permanent presence of

humankind into the solar system. A habitat completely Earth-

independent faces many challenges as there are various items

that need to be restocked and repaired throughout the years on

the space station.

In the decades following the full operation and

independence of the space station, the space station could have

various options for expansion. The station could be modified

into a two ring model to allow for more volume and to sustain

more crew.

The HERMES can also be used as a model design or

transport ship for in orbit settlement of other planetary bodies.

Constructed in lunar orbit and fitted with upgraded propulsion

systems to allow for a self-propelled journey to Mars or

beyond. A portable long-term scientific laboratory allowing the

close study of worlds whose surfaces are inaccessible or

inhospitable to landing craft.

Figure 10. Two joined ring structures

showcasing the modular approach to

the design of the HERMES

17


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18


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19


Appendices

20


21


22


Destabilization

criteria

Eccentricity 1% increase

Periapsis & apoapsis

altitude

± 5%

Experimental design

Objective functions f1 = min (∑|∆V𝑥,𝑦,𝑧|) &

f2 = max(time of flight)

Decision variables 0.0436 < 𝑛< 0.0499 [deg/s] 0 < 𝑒 < 0.05 85 < 𝑖 < 87 [deg] 0 < 𝛺 < 360[deg]

0 < 𝑢 < 360 [deg]

1 Jan 2029 12:00 < Ep <

31 Dec 2030 12:00 UTCG

Constraint function f2 > 14 days

Evolutionary

algorithm parameters

N Generations = 48,

N Individuals = 96

STK parameters Propagator: Moon High

Precision Propagator v10

(48 degree, 48 order) with

Sun, Earth point-mass.

Objectives f1 = 6.185 m/s, f2 = 110.5 days

Orbital

state

Apoapsis altitude = 370.68 km

Periapsis altitude = 229.17 km

Eccentricity = 0.03473

Inclination = 86.13º

RAAN = 142.68º

Arg. Of Lat. = 262.13º

Target Insertion Date:

22nd Dec, 2029 21:46:45 UTCG

Multi-objective design optimization summary.

Objectives and orbital elements.

23


24


25


26


27


Nominal thruster operation.

Unit Value

Thrust N 13.37

Mass Flow Rate g/s 6.4

Specific Impulse S 206.9

Chamber Conditions

Pressure kPa 101.325

Temperature K 1500

Nozzle Geometry

Throat Diameter mm 10

Exit Diameter mm 40

Expansion Ratio Ae/A* 16

Total Operational Costs (4 Thrusters)

Burn Time Days 10

Propellant Mass (Water) kg 22,234

Electrical Power (50% efficiency) kW 154.1

28


Breakdown of Costs

Cost Number Total cost

Developing Miniaturized

satellites

Hardware and software 50,000 24 1,200,000

Manufacturing 10,000 1 10,000

Lunar Antenna

Signal transmitter 80,000 1 80,000

Hardware and software 70,000 1 70,000

Launch cost 100,000 2 200,000

Moonbot



Launch cost 15,000 3 45,000

29


Table 4. Lunar Resources

Type of Occurrence Main Commodities Where on Moon?

Mafic igneous rocks Fe, Cr, Ti Central peaks of craters; crater

rim deposits; maria

Evolved igneous rocks K, Rare Earth Elements, P, Th,

U, Zr

Procellarum KREEP terrane

(western nearside)

Explosive volcanic deposits Fe, Zn, Cd, Hg, Pb, Cu, F Pyroclastic deposits; near vent

deposits in maria

Meteoric debris Ni, Pt, Pd, Ir, Au Regolith, regolith breccias,

highland impact breccias,

segregations in impact melt

sheets

Space weathering Solar wind gases in regolith;

microscopic metallic iron

Regolith

Volatile deposits H2O? Other volatile compounds

(comet species, Hg)?

Permanently-shadowed craters

in polar regions

KREEP = Potassium (K), Rare Earth Elements (REE), Phosphorus (P)

Lunar base Sub-System Architecture

Breakdown of Costs

Cost Number Total cost

Developing Miniaturized

satellites

Hardware and software 50,000 24 1,200,000


Lunar Antenna

Signal transmitter 80,000 1 80,000


Launch cost 100,000 2 200,000

Moonbot



Launch cost 15,000 3 45,000

30


31


32


Mission Segment Result

Earth to Selenocentric Orbit maneuvers

Trans-lunar insertion orbit ΔV

Lunar orbit insertion ΔV

3,110.46 m/sec lunar Northern hemisphere approach

(N)

3,110.43 m/sec lunar Southern hemisphere approach

(S)

772.70 m/sec (N)

772.30 m/sec (S)

Lunar launch and correction maneuvers

Lunar launch ΔV

Sum of Corrections ΔV

1,500.0 m/sec

67.971 m/sec (Periapsis and apoapsis raise,

circularization)

Station-keeping correction from safety boundary

condition

Sum of Corrections ΔV

7.450m/sec (Apoapsis and periapsis raise,

circularization)3

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2016 RASC-AL Technical Paper Compliance Matrix Earth Independent 1G Space Station Page #

Is the overall system infrastructure sufficiently addressed? 2

Have you proposed synergistic application of innovative capabilities and/or new technologies for evolutionary

development that enable future missions, reduce cost, or improve safety? 7-8

Does your scenario address novel applications (through scientific evaluation and rationale of mission operations) with

an objective of sustaining space exploration by NASA, the international space community and/or industry? 7-11

Have you considered unique combinations of the planned elements with innovative capabilities/technologies to

support crewed and robotic exploration of the solar system? 2-7

Have you addressed reliability and human safety in trading various design options? 11-13

Have you identified the appropriate key technologies and TRLs? 6

Have you identified the systems engineering and architectural trades that guide the recommended approach? 7-11

Have you provided a realistic assessment of how the project would be planned and executed (including a project

schedule with a test and development plan)? 2

Have you included information on annual operating costs (i.e., budget)? 4-5

Have you given attention to synergistic applications of NASA’s planned current investments (within your theme and

beyond)?

*Extra credit given to additional inclusion of synergistic commercial applications*

2-7

Does your paper adhere to the 10-15 page limitation and other formatting guidelines? yes

Summarize Critical Points Addressing Theme Compliance and Innovation

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(At a minimum, please quickly address the bullets.

Feel free to summarize additional key components of your concept, using up to one additional half page if extra space if needed.)

Capabilities that enable Earth resupply independence (after 5 years)

Ability to continuously support 16-20 people

Unique large-scale 1G facility design

Timeline of missions (campaigns) to show gradual buildup of capabilities, infrastructure, and risk reduction over 20-30 years

Budget accurately reflects the constraints listed in the themes description

Innovations in technology and operations that prepare and assist for future, further destinations

The HERMES mission incorporates a ring structure space station orbiting the moon with an in-situ resource utilization base on the lunar surface. This

lunar base will provide a sustainable solution to continuously supporting 24 crew members on board the space station. The lunar base with the mining

rover, processing plant, and ascent descent transport vehicle will provide the station with water, metals for construction of the station, and regolith for

radiation shielding. The station is a ring design and utilizes centrifugal force by rotation to simulate a 1G environment. The on orbit construction and

assembly of the space station using 3D printing satellite robots is a unique and challenging design. Food will be grown hydroponically on board the

space station and many systems similar to those on the International Space Station will be incorporated to support the crew members. The hydroponic

system and large amounts of storage as well as the lunar resupply base allows the station to become Earth-independent. The current and future budgets

of NASA when planning the this mission and its timeline. International and commercial partnerships will be sought to make this large scale mission

possible. All the technologies of this mission, especially the in orbit 3D printing construction and assembly, material processing on the moon, and Earth-

independence on the space station will assist in future space missions. The HERMES space station can be modified and added on to as well as taken to

other destinations such as Mars and further into the solar system.

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Team Info Graphic of Concept/Technology

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Required: University Name, Paper Title, Faculty Advisor, Team Leader Name, &

Competition Category (undergrad or graduate)

Optional:

University/team logo; team photo

Paper Title: Development of Full-scale Mission Architecture for

the Habitable Environment for Research and Manned Exploration

of Space (HERMES)

University Name: University of Illinois at Urbana Champaign

Royal Melbourne Institute of Technology

Faculty Advisor: Victoria Coverstone, Koki Ho, Hideaki Ogawa

Team Leader: Lui Suzuki, George Coulloupas

Competition Category: Undergraduate

(Insert graphic/image(s) here)

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hermes final technical paper (1)

Documents