SpaceRadiationProtectionduringNASAExplorationClassMissions

KerryLeeSpaceRadiationAnalysisGroupOperationsLead

NASAJohnsonSpaceCenterHouston,TX

Outline

• SRAGOperationsandInstrumentationonISS• SRAG’spurposeistoprotectastronautsfromradiationexposure

• ExplorationMissionsandOperations• MeasurementsvsModel• RadiationHazardMitigationPlanning

• MPCV*RadiationSystemSensors

• SpaceWeatherNeedsforExplorationClassmissions

*Orion=MPCV=Multi-PurposeCrewVehicle

ISSInstrumentation

• CPDS– ChargedParticleDirectionalSpectrometer

• REM– RadiationEnvironmentMonitor

• ActivedosimeterwithUSBinterface

• TEPC– TissueEquivalentProportionalCounter

• LocatedinISSServiceModule• IV-TEPC– newTEPCdetector

• MovesaboutISSevery4-6weeks

• ISS-RAD– RadiationAssessmentDetector

RadiationEnvironmentMonitor(REM)TheTimepix Detector

§ DevelopedasaHighEnergyPhysicsapplicationofmedicalimagingtechnology

§ HybridPixelDetectorwithindependentcountingandreadoutcircuitryineachpixelfootprint

§ 256x256pixelgridwithtotalareaof2cm2

PixelDetectorImagefromMedipix collaborationwebsite:http://medipix.web.cern.ch/medipix/img/medipix2/web_flipchip.gif

PixelDetectorTechnology

ExplorationMission(EM)ClassMeasurementsandSimulation

ExplorationFlightTest1– Dec5,2014

Credit: NASA

L

R

GoogleEarthVideo– EFT-1Flight

EFT-1MissionAnalysis

• Trajectory:EFT-1ApproximatedTrajectory

• Shields:FullvehicleCADmodel• Points:BIRDRAMs1and2,BIRDDetectorsLeftandRight

• TrappedRadiation:AP8/AE8Model

• GCR:Badhwar-O’Neill2014Model,December5,2014

• RadiationTransport:HZETRN2015

BIRDLeftModel

BIRDLeftModelvsData• DataisinmicroGy andmodelincGy

• 4ordersmagnitudedifference

• ModelslightlyunderpredictsGCRregions• 10sofpercent

• Modelsignificantlyunderpredictstrappedradiationregions

• Factorof2-3

ModelvsDataforeachEFT-1Measurement

ShieldFile Modeled(mGy) Measured(mGy)BIRDLeft 5.57 17.9BIRDRight 5.94 15.7BIRDRAM1 6.81 15.1BIRDRAM2 6.18 13.5

EM-2MissionAnalysis

• Trajectory:HybridTriple

• ShieldPoint:Crew1ChestLocationinOrionSeat1ofEM-2Vehicle

• Trapped:AP8/AE8

• GCR:Badhwar-O’Neill2014,August2010• ExpectedtobesimilartoAugust2021whichisEM2schedulelaunchdate

• RadiationTransport:HZETRN2015

EM-2MissionOption:FreeReturnHybridTriple

Pre-Decisional:InternalNASAUseOnly 14

(4)Trans-LunarInjectionOrion

(5)OTCManeuversOrion

(8)Entry&Landing

(7)RTCBurnOrion

Notional

(1) Launch(2) ARB ICPS

(3)ICPSDisposal

(6)FreeReturnFlyby(noburn)Orion

1-2)LEOparkingorbit,1-2orbitcheckout,andICPSApogeeRaiseBurn(ARB)demonstration3)OrionseparatesafterARB,achievessafeseparationdistance,ICPSperformsdisposalburn4)OrionflighttestsystemcharacterizationoccursinHEO(16-24hrs),TLIperformedbyOrion6)Freereturnflyby,noOrioncriticalburnsrequired8)Nominalmissionreturnandcis-lunarentryvelocitytargetingSanDiegovicinity

Considerations• Achieveslunarvicinity• MaintainsLEO/HEO

checkoutopportunity• WithinexistingOrion

capabilities• LikelywithinICPS

capability

EM-2ProposedHybridTripleTrajectory

• 3passesthoughtrappedradiationbeltscontribute~2/3ofmodeleddose• 12daysofGCRcontributes~1/3ofmodeleddose

FutureExplorationMissionAnalyses

• Needtoevaluatehundredsofpotentiallaunchtrajectoriescoveringthefulllaunchwindow

• In keepingwiththeALARAprinciplewewillrecommendtrajectorieswiththelowestexposures

• Usethebesttrappedenvironmentmodelwiththelatestdata(IRENE)

• UseEM-1Mission(December2019launch)measurementstocalibratepredictioncapabilitiesforfutureEM-Xmissions

MPCVRadiationSystem• HybridElectronicRadiationAssessor(HERA)

• Activeinstrumentprovidestelemetereddatastream

• Systemconsistsoftworedundantstrings• Eachstring- 1PowerUnitand2SensorUnits

• RadiationAreaMonitors(RAMs)• PassivedetectorsfromShuttleandISSheritage

• CrewPersonalActiveDosimeter(CPAD)• Activedosimeterprovidesindividualdosimetric measurement

• Dataretrievedafterthemission

HERAVehicleLocations

HPUs

HSUStarboard

HSUPort

HSUinshelter

HSUFwd Bulkhead

MPCVRadiationMitigationPlanning

• HERAsystemisconnectedtotheCautionandWarningSystem• AudiblealarmsoundswhenHERAthresholdisexceeded• IfgroundcommunicationisavailableRadiationConsoledeterminesifshelteringisneeded,otherwisecrewwillshelteruponHERAalarm

• AcuteradiationimpactassessmentmodeledbasedonHERAmeasurements

• StowageconfigurationoptimizedbasedonHumanintheLoop(HITL)test• HITLtestconsistedofmanysimulated4personcrewsinthemediumfidelitymockupatNASA/JSC

• Abouthalfofthetestsubjectswereastronauts• Noneofthetestsubjectshadeverseentheprocedureandmostwereunfamiliarwiththemockuplayout

• Averagetimetoreconfigurethecabinwasabout30minutes

Originalstowageconfiguration

D

E

F

A

B

Stowagere-configurationbasedonHITLtest

StowageRe-configurationModelResults• SRAGusedstowageconfigurationusedinHITLtest

• 11CTBsand3halfCTBsand10canisters(totalmass=630lb)• 6CTBsontopofbacksofseats1&2overshelter(baysDandE)• 3CTBsinfrontofshelterunderDUs• OnehalfCTBonthesidesofshelter• Added2suitbags(50lb each)onachsideoftheshelter(total4bagsof200lb)• 10canisters(9inODand9.5inlong)insideWMSonthesidewallsharedwithBayD

Crew 1 Crew2 Crew3 Crew4CrewinSeats 208mSv 191mSv 268mSv 230mSvHITLconfig (630lb +suitbags) 69mSv 83mSv 79mSv 71mSv

WholeBodyEffectiveDose*RadiationAnalysisResultsforasimulated1972KingSpectrumSPE

*EffectiveDoseasdefinedinNationalCouncilonRadiationProtectionandMeasurements(NCRP)ReportNo.132

Summary

• EstablishedMPCVconceptofoperationsforradiationcontingencyevent• Protectionispossiblebelowrequiredlimitwithoutflyinganyparasiticmass• Finaldetailsarebeingworked

• MPCVradiationinstrumentationisbuilt• HardwaretestingonISSinthenearfuture

• SRAGOperationalneedsforfutureexplorationmissions(inchronologicalorder)

• UselatestIRENEreleasetoevaluateEM-1andEM-2trajectoriesandcomparewithdata

• ForecastingtoolsformoreleadtimeonSPEs• All-clearstillavalidoperationalmethod– nogeomagneticfieldprotectionforGatewaymissions

• OffSun-EarthlineSPEforecasting(all-clear)• EuropaandMarsmissions(2030s)

Acknowledgements

• SpaceRadiationAnalysisGroup– REMandHERAanalysiswork• MartinKroupa,StuartGeorge,Nic Stoffle,ThomasCampbell-Ricketts,RyanRios

• AESProgramforfundingHERAdevelopment• JasonCrusan,CatherineMcleod,ScottWheeler,MichaelEcord andentireHERAdevelopmentteam