micro asteroid prospector
TRANSCRIPT
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Micro Asteroid Prospector Powered byMicro Asteroid Prospector Powered by
Energetic Radioisotopes: MAPPEREnergetic Radioisotopes: MAPPER
Steven D. HoweSteven D. Howe
Gerald P. JacksonGerald P. Jackson
Presented at the NIAC Review MeetingPresented at the NIAC Review Meeting
March 23, 2004March 23, 2004
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Topics PresentedTopics Presented
Goals and objectivesGoals and objectives
Target characterizationTarget characterization-- Main Belt AsteroidsMain Belt Asteroids
SubSub--SystemsSystems
Preliminary optimization calculationsPreliminary optimization calculations
IssuesIssues
ConclusionsConclusions
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Goals and ObjectivesGoals and Objectives
Purpose: Catalogue the resources of the Main BeltPurpose: Catalogue the resources of the Main Beltasteroids for future explorationasteroids for future exploration
Goal: Design a lightGoal: Design a light--weight, inweight, in--expensive spacecraftexpensive spacecraftso that a fleet can cruise autonomously through theso that a fleet can cruise autonomously through the
Belt for 20 yearsBelt for 20 years
Objectives:Objectives:
Determine mass, power, and number of spacecraft forDetermine mass, power, and number of spacecraft forcharacterizing a signif icant fraction of the Main Beltcharacterizing a significant fraction of the Main Beltasteroidsasteroids
Identify major issues and future goalsIdentify major issues and future goals
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Main Belt AsteroidsMain Belt Asteroids
The Asteroid Belt may be the most valuable future resourceThe Asteroid Belt may be the most valuable future resourcein the solar systemin the solar system
The asteroid belt is estimated to contain 100 bill ion objects.The asteroid belt is estimated to contain 100 bill ion objects.
The total mass is calculated to be around 1/1000 of EarthsThe total mass is calculated to be around 1/1000 of Earthsmassmass -- equivalent to breaking the top 1.3 miles of the Earthsequivalent to breaking the top 1.3 miles of the Earths
crust into piecescrust into pieces
Diameters range from a few kilometers to a few metersDiameters range from a few kilometers to a few meters
Most of the asteroids are silicon dioxide, some are iron andMost of the asteroids are silicon dioxide, some are iron andother metals, a lesser number are carbonaceousother metals, a lesser number are carbonaceous chondriteschondriteswith up to 10 % water by weight, and a few may be heavywith up to 10 % water by weight, and a few may be heavyprecious metals.precious metals.
Average separation distance is 2.3x10Average separation distance is 2.3x1044 km forkm for DminDmin=20m=20m
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The main belt asteroid sizeThe main belt asteroid size--frequencyfrequency
distribution approximately follows a power lawdistribution approximately follows a power law
Ntot=2.88e06 D-2.27
(Adapted from(Adapted from FarinellaFarinella and Davis, 1994)and Davis, 1994)
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The asteroids in the belt are notThe asteroids in the belt are not
uniformly distributed but form bandsuniformly distributed but form bands
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SubsystemsSubsystems
Th MAPPER i hTh MAPPER t i th
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The MAPPER concept requires theThe MAPPER concept requires the
integration of many subsystemsintegration of many subsystems
A power supply to provide electrical power to a platform thatA power supply to provide electrical power to a platform thatcancan propulsivelypropulsively cruise between targetscruise between targets
A radiation detector system that can measure elementalA radiation detector system that can measure elemental
constituents at a standoff distance,constituents at a standoff distance,
A heating system that can extract and store volatiles forA heating system that can extract and store volatiles forpropulsion,propulsion,
A tagging method to label the target for future generations.A tagging method to label the target for future generations.
A method of absolute coordinate location determination viaA method of absolute coordinate location determination viastar tracking or interstar tracking or inter--communication with Earth or a fixedcommunication with Earth or a fixedbeacon.beacon.
Radar system sufficient to provide guidance to the nextRadar system sufficient to provide guidance to the next
target and avoidance of smaller objectstarget and avoidance of smaller objects A communication link to EarthA communication link to Earth
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POWERPOWER
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232232U offers high specific powerU offers high specific power
The decay sequence ofThe decay sequence of 232232UUreleases 25% of the energy perreleases 25% of the energy peratom of a nuclear reactor butatom of a nuclear reactor butrequires no critical massrequires no critical mass
55 W(th)/gW(th)/g peak is 10 timespeak is 10 timesPu238Pu238
Power scales linearly with massPower scales linearly with mass
Relatively flat over 20 yearRelatively flat over 20 year
periodperiod Production:Production:
Available in spent fuelAvailable in spent fuel
Fast neutron irradiate UFast neutron irradiate U--233233
Accelerator irradiate ThAccelerator irradiate Th--232232 Uses tuned PV conversionUses tuned PV conversion
High gamma activity requiresHigh gamma activity requiresstandoff from platformstandoff from platform
ISSUE: l ifetime of tuned PVISSUE: l ifetime of tuned PV
Preliminary estimates of power source activityPreliminary estimates of power source activity
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Preliminary estimates of power source activityPreliminary estimates of power source activity(3e04(3e04 CiCi) are well below past launch history for) are well below past launch history for
the USthe US
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Power levels and mass of the power system varyPower levels and mass of the power system vary
strongly with average cruise velocity andstrongly with average cruise velocity and IspIsp
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PROPULSIONPROPULSION
Mi d i h ff h i l
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Microwave driven thrusters offer the potentialMicrowave driven thrusters offer the potential
of long life due to low surface interactionsof long life due to low surface interactions
(courtesy of(courtesy of http://www.islandone.org/APC/Electric /04.html)http://www.islandone.org/APC/Electric /04.html)
http://www.islandone.org/APC/Electric/04.html)http://www.islandone.org/APC/Electric/04.html)http://www.islandone.org/APC/Electric/04.html) -
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RefuelingRefueling
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Refueling sequenceRefueling sequence
Cruise
vector
Neutron probe
Water = Yes then decelerate
V = cruise velocity
T = Taccel
Return to asteroid in 1.4 Taccel days
Accelerate for distance and decelerate
for distance
Accelerate up to
Vcruise in Tacceldays
Water = NO
Then radar
search andcourse correct
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Microwaves couple toMicrowaves couple to regolithregolith
In 1985, Dr. T. Meek of theIn 1985, Dr. T. Meek of theLos Alamos NationalLos Alamos National
Laboratory (LANL)Laboratory (LANL)demonstrated the ability todemonstrated the ability toextract water from simulatedextract water from simulatedlunar soil using 2.45 GHZlunar soil using 2.45 GHZmicrowaves.microwaves.
According to Meek, usingAccording to Meek, usingconventional means to heatconventional means to heatthe soil would require 10,000the soil would require 10,000
times more energy thantimes more energy thanusing the microwaves tousing the microwaves toselectively heat the water inselectively heat the water inthe soil.the soil.
2.45 GHz microwaves for 15 s2.45 GHz microwaves for 15 sonto lunar soil sampleonto lunar soil sample
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DETECTIONDETECTION
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Neutron SourceNeutron Source
Original concept usedOriginal concept used 232232U plus Beryllium to makeU plus Beryllium to makeneutrons via (neutrons via (,n,n) reaction) reaction 44 sourcesource
Created too much backgroundCreated too much background
Irradiated componentsIrradiated components
Required close approach, i.e. < one diameterRequired close approach, i.e. < one diameter
Propose H(Propose H(66Li,n) mini acceleratorLi,n) mini accelerator 13.213.2 MeVMeV 66LiLi
1010oo
cone of emissioncone of emission Pulsed, intense source fired during flyby closest approachPulsed, intense source fired during flyby closest approach
Optimum standoff distance is 3 X diameterOptimum standoff distance is 3 X diameter
Flight qualified neutron detector hasFlight qualified neutron detector has
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Flight qualified neutron detector hasFlight qualified neutron detector has
been flown to find water on the Moonbeen flown to find water on the Moon
Designed and built atDesigned and built at
LANL by W. FeldmanLANL by W. Feldman
Weight: 8 lbsWeight: 8 lbs
Electrical powerElectrical power reqdreqd: 3: 3
ww
33He tubesHe tubes
Returned neutronReturned neutron
spectrum dependsspectrum depends
strongly on hydrogenstrongly on hydrogen
contentcontent
Issue: lifetime
Howe problem
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-09 1.0E-08 1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03
neutron energy
flu
x
3%water
water
10%
Issue: lifetime
Flight qualified gammaFlight qualified gamma--ray detector hasray detector has
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Flight qualified gammaFlight qualified gamma-ray detector hasray detector has
been flown measure gammas on the Moonbeen flown measure gammas on the Moon
Designed and built atDesigned and built at
LANL by W. FeldmanLANL by W. Feldman
Weight: 3 lbsWeight: 3 lbs
Electrical powerElectrical power reqdreqd: 2: 2
ww
BGO crystalsBGO crystals
Gamma rays identifyGamma rays identify
heavy metalsheavy metals
CdZnTeCdZnTe oror HgIHgI maymay
provide better resolutionprovide better resolution
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TAGGING and COMMUNICATIONTAGGING and COMMUNICATION
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Smart Dust sensors developed at Berkeley low massSmart Dust sensors developed at Berkeley low mass
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Smart Dust sensors developed at Berkeley low massSmart Dust sensors developed at Berkeley low mass
and long lifeand long life
ProPro
Low massLow mass
Broadcast widely, i.e.Broadcast widely, i.e.44
Reasonable rangeReasonable range
ConCon--
Power neededPower needed
Less secureLess secure
Limited lifeLimited life
Radiation mayRadiation maydegradedegrade
(courtesy of(courtesy of
http://http://robotics.eecs.berkeley.edu/~pister/SmartDustrobotics.eecs.berkeley.edu/~pister/SmartDust /)/)
Communications back to Earth rely onCommunications back to Earth rely on
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Communications back to Earth rely onCommunications back to Earth rely on
demonstrated technologiesdemonstrated technologies
Galileo transmissions required 400 w onGalileo transmissions required 400 w on
board powerboard power Platform will determine location from splitPlatform will determine location from split
field of view star sensors (field of view star sensors (
StarNavStarNav
II)II)
[http://www.jsc.nasa.gov/aiaa/lal/lljun01/][http://www.jsc.nasa.gov/aiaa/lal/lljun01/]
Information burst will include location,Information burst will include location,
measured gammameasured gamma--ray and neutronray and neutronspectra, and ship status dataspectra, and ship status data
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GUIDANCEGUIDANCE
The architecture depends on the averageThe architecture depends on the average
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e a c ec u e depe ds o e a e agep g
velocity of the craftvelocity of the craft i.e. cone of acceptabilityi.e. cone of acceptability
A light weight radar is required but does notA light weight radar is required but does not
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A light weight radar is required but does notA light weight radar is required but does not
yet existyet exist
Needs to see 156,000 km outNeeds to see 156,000 km out
Correlate distance with return signal strength (RSS) andCorrelate distance with return signal strength (RSS) and
target sizetarget size Indicate water content (i.e.Indicate water content (i.e. albedoalbedo) with RSS) with RSS
Determine relative velocity with multiple returnsDetermine relative velocity with multiple returns
May require power accumulator to operate in highMay require power accumulator to operate in high--powerpowerbut pulsed modebut pulsed mode
Determines required deltaDetermines required delta--VV
Enables target choiceEnables target choice
Issues:Issues: baseline needed for Synthetic Aperture Radar ?baseline needed for Synthetic Aperture Radar ?
power level?power level?
OptimizationOptimization
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OptimizationOptimization
DeploymentDeployment Nuclear Thermal RocketNuclear Thermal Rocket
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DeploymentDeployment Nuclear Thermal RocketNuclear Thermal Rocket
Current NASA program, Prometheus, isCurrent NASA program, Prometheus, isinterested in recovering the NTR to fulfill the newinterested in recovering the NTR to fulfill the new
Presidential space exploration directionPresidential space exploration direction NTR is considered to be a demonstratedNTR is considered to be a demonstrated
technology that could be recovered within atechnology that could be recovered within a
decadedecade Assumed operating parametersAssumed operating parameters
5000 lb thrust engine5000 lb thrust engine
T/W = 3T/W = 3 IspIsp= 950 s= 950 s
HohmannHohmann transfer orbittransfer orbitsum ofsum of VsVs= 9.52 km/s= 9.52 km/s
Reusable for N missionsReusable for N missions
Preliminary optimization calculationsPreliminary optimization calculations
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y p
are positiveare positive
Power level is dictated by the propulsion systems need toPower level is dictated by the propulsion systems need toaccelerate over a short period (variable)accelerate over a short period (variable)
The same power level is sufficient for communications backThe same power level is suff icient for communications backto Earth, water extraction, neutron generation, and the radarto Earth, water extraction, neutron generation, and the radarsystems.systems.
The average cruise velocity,The average cruise velocity, IspIsp, time of acceleration, and, time of acceleration, andinterception velocity are independent variablesinterception velocity are independent variables
Propellant requirements for initial acceleration to cruise,Propellant requirements for initial acceleration to cruise,intercepts, and refueling are determinedintercepts, and refueling are determined
Power system mass including waste heat radiator is found forPower system mass including waste heat radiator is found forthe tuned PV methodthe tuned PV method
Ship characteristics depend strongly onShip characteristics depend strongly on
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the average cruise velocitythe average cruise velocity
Significant surface area can be scannedSignificant surface area can be scanned
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by reasonable cruise velocityby reasonable cruise velocity
Optimum specific impulse lies withinOptimum specific impulse lies within
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achievable valuesachievable values
Preliminary cost optimization indicatesPreliminary cost optimization indicates
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lower than expected cruise velocitylower than expected cruise velocity
Phase II will strive to resolve severalPhase II will strive to resolve several
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issuesissues
LifetimesLifetimes-- Power conversionPower conversion scintillatorscintillator
RFRF taggerstaggers Microwave generatorMicrowave generator
detectorsdetectors
Need time dependent simulation to developNeed time dependent simulation to developguidance, control algorithms, andguidance, control algorithms, and VVinterceptintercept
RadarRadar mass and powermass and power
Earth communicationsEarth communications PackagingPackaging-- is the platform volume limited oris the platform volume limited or
mass limitedmass limited
C l i
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ConclusionsConclusions
A host of small platforms can survey a significantA host of small platforms can survey a significantfraction of the asteroid population in a 20 yearfraction of the asteroid population in a 20 year
intervalinterval The land area surveyed could be equal to aThe land area surveyed could be equal to a
major fraction of the Earths surface areamajor fraction of the Earths surface area
The energetic radioisotope power supplyThe energetic radioisotope power supplyappears adequate for the mission needsappears adequate for the mission needs
Most subsystem hardware has currentMost subsystem hardware has current--dayday
examples that can be improvedexamples that can be improved A timeA time--dependent simulation is needed for flightdependent simulation is needed for flight
profile demonstration and targeting algorithmprofile demonstration and targeting algorithmdevelopmentdevelopment