《Survivability Assessment Method of Spacecraft at the Threat of Space Debris.doc》由会员分享，可在线阅读，更多相关《Survivability Assessment Method of Spacecraft at the Threat of Space Debris.doc（11页珍藏版）》请在三一文库上搜索。
1、Survivability Assessment Method of Spacecraft at the Threat of Space DebrisJournalofSystemsScienceandInformation2006,Vo1.4,No.2,PP.203-213PublishedbyResearchInformationLtd(RIL),UKSurvivabilityAssessmentMethodofSpacecraftattheThreatofSpaceDebrisYangPei,BifengSong,QingHanCollegeofAeronautics,Northwest
2、ernPolytechnicalUniversity,Xian710072,China(ReceivedNovember30,2004)Abstract:Thethreatofspacedebronspacecrafthasincreasedourattentiontothesurvivabilityenhancementdesignofspacecraft.Thispaperstudiesthesurvivabilityassessmentmethod,whichhasmainlytwoparts,namelysusceptibilityassessmentandvul-nerability
3、assessment.Ouremphasisfocusesonhowtoassessthevulnerabilityofspacecrafttospacedebris.Thebasicvulnerabilityassessmentprocessincludes:(1)theanalysesofthethreatenvironmentofspacedebris;(2)theprocessofidentificationofcriticalcompo-nentsofspacecraft,inwhichaDMECA(damagemode,effects,andcriticalityanalysis)
4、isintroducedandanexpesystemisproposedtogetthedamageratioofeachcomponent;(3)thespacecraftgeometricaldescriptionmethod,inwhichshotlinescanningmethodisdescribedtocalculatetheprojected/overlappingareaofcomponentsanddeterminethemasking/shieldingrelationshipamongcomponents;(4)thecalculationofspacecraftkil
5、lprobabilityandvulnerablearea.Atlast,theauthorsconcludethattheproposedassess-mentmethodissystemicandfeasible,anditca31giveaquantitativeassessmentresultofsurvivability/vulnerabilityinthespacecraftconceptualdesign.Thetheorycontainedinthispaperisusefultodevelopcomputerizedtoolforspacecraftsurvivability
6、analysis.Keywords:spacecraft;survivability;vulnerability;spacedebris;probability1.IntroductionEveryspacecraftinorbitissubjectedtoseveraltypesofenvironmentalhazardssuchasneu.tralatmosphere,thermal,plasma,meteoroids,orbitaldebris,solaractivity,ionizingradiation,andSOonI-3.Meteoroidsarecreatedfromthebr
7、eakupofasteroidsandcomets.OrbitalThisprojectissupportedbyNationalNaturalScienceFoundationofChina(10372082);theAerospaceScienceFoundation(02B53008);andtheDoctorateFoundationofNorthwesternPolytechnicalUniversity(CX200301)204JournalofSystemsScienceandInformationVo1.4No.2debrisisaby-productofmansactivit
8、iesinspace,andconsistsofobjectsranginginsizefromapieceofpaintthathasflakedoffofarocketoraspacecrafttofragmentsofanexplodedrocketupperstagetoanentirederelictspacecraft.ManmadeorbitaldebrisparticlesinlOWearthorbitincreaseatarateofupto5%peryear引.Addedtothenaturallyoccurringme-teoroidenvironment,thispar
9、ticulateenvironmenthasbecomeaformidablespacecraftdesignchallenge.Inordertoaccomplishmissionandsurvivethespacedebrisenvironment,spacecraftmusthavetheabilitytowithstandthehypervelocityimpact.So,Survivabilitybecomesanimportantconcernofspacecraftdesign.Despiteseveralsurvivabilityassessmentmethodhasbeenp
10、roposed4-6,anacceptedmethodofanalysishasnotbeendeveloped7.Theaircraftcommunityhasexpendedagreatamountofeffortoverthelastyearstodevelopacoordinatedsurvivabilitymethodology.Reference7hasintroducedanotionalconceptofhowtoadaptawell-developedaircraftsurvivabilityanalysismethodforuseonspacecraft.Thispaper
11、pro-posesasystematicsurvivabilityassessmentmethodandmayberegardedastheextensionofthemethodologyinreference7.2.SpacecraftSurvivabilityAssessmentForspacedebristhreat,spacecraftsurvivabilityisdefinedhereasthecapabilityofaspacecrafttoavoidbeinghitbydebrisorwithstandthedebrisenvironmentwithoutsufferingan
12、abortiveimpairmentofitsabilitytoaccomplishitsdesignatedmission.SurvivabilityCanbemeasuredbytheprobabilityofsurvivabilityPs.Survivabilityiscomposedoftwofocusareas:1)suscep-tibility;2)vulnerability.SusceptibilityreferstotheinabilityofaspacecrafttoavoidbeinghitbyspacedebrisandCanbeexpressedastheprobabi
13、lityofhitPH.VulnerabilityreferstotheinabilityofaspacecrafttowithstandthedamageafterbeinghitbyspacedebrisandCanbeexpressedastheconditionalprobabilityofkillgivenahitr/日.TheprobabilityofkillofthespacecraftPK(thespacecraftSkillability)istheproductoftheprobabilityofhit(thespace-craftSsusceptibility)PHand
14、theconditionalprobabilityofkillgivenahit(thespacecraftSvulnerability,PKfH.ThusS,91,PK=PHPK/H(1)TheprobabilityPsisthecomplementofPK.Hence,Ps=1一(2)3.SusceptibilityAssessmentThepurposeofspacecraftsusceptibilityassessmentistodeterminetheprobabilityPHthatspacecraftwillcollidewithspacedebris.First,PHdepen
15、dsonthespacedebrisenvironmentsincludingthesize,mass,spatialdensityandthree-dimensionalvelocitydistributionofdebris.PeiY.eta1.SurvivabilityAssessmentMethodofSpacecraftattheThrt.205Second,isrelatedtothephysicalcharacteristicsandorbitofspacecraft.ThemostobviousfactisthatPHisproportionaltothesectionalar
16、eaandorbitaldurationofspacecraft.Atthesametime.PHisrelatedtosomeorbitalparameterssuchasorbitalobliquity,semi-longaxes,eccentricity,andSOon.SpaceDebrisMitigationHand-bookcompiledbyESAgivesthesatelliteprobabilityofhitbyspacedebrisasfollows.Assumingthemovementofdebrisfollowsarandomprobabilitydistributi
17、on,accordingtogaskinematicstheoryandthePoissondistribution,PHisexpressedas101PH=1一exp(一.AcDDAt)(3)where,istherelativevelocityofsatellitetospacedebris;AcDistheaveragesatellitecollisionsectionalarea(m2);Distheaveragedebrisspatialdensityinsatelliteorbit(particles/m);Atisthedurationofsatelliteindebrisen
18、vironments.Aftercalculation,reference【11JpointsoutthaltnOmatterwhateverorbitthesatelliteis,thesatelliteprobabilityofhitbydebrislargerthan1amisverysmall,thatmeansonlyahitOCCurSinseveralmillionyearsorevenseveral10millionyears;butthesatelliteprobabilityofhitbydebrislargerthan0.1cm.mostofwhicharesubmill
19、imeterdebris.iSapparentlyincreased.VulnerabilityAssessmentMethodVulnerabilityistheimportantindexofspacecraftsurvivabilitydesign.Themorevulnerableaspacecraftis,themorelikelyitwillbekilledwhenhitbyspacedebris.Figure1showstheflowchartofspacecraftvulnerabilityanalysis.Fig.1Vulnerabilityanalysisflowchart
20、Fig.2Basicstepsofcriticalcomponentsidentification4.1.ThreatCharacteristicAnalysisTheeffectsofspacedebrisonspacecraftdependonthesize,maSS,velocityandimpacting206JournalofSystemsScienceandInformationVl01.4No.2obliquity.Spacedebriscouldbedividedintothreediametercategories.(1)Diameterlessthan0.01cm.This
21、kindofdebriscouldproducecraterorcontaminantsonthespacecraftsurfaces.Thedebrisislargeinamountandcouldresultinobviouscumulativedamageinspacecraftafterlongtimecollisionwithspacecraft.(2)Diameterbetween0.01cmand1am.Thiskindofdebriscouldcausesignificantlycumulativedamageinspacecraftandtheamountofdamageit
22、doesdependsonthedamage-worthinessandprotectionmethodsofspacecraft.(3)Diameterlargerthanlcm:Thiskindofdebriscouldproducecatastrophicdamageinspacecraft.Atpresent,protectionmethodsusedinspacecraftonlywithstandthedamageproducedbydebriswithdiameterlessthan0.01cmandmasslessthan1.46g.Debrisobjectslargertha
23、nlcmmustbeavoidedbypropulsivemaneuvers.4.2.CriticalComponentsIdentificationMethodFigure2showstheprocessofidentificationofthecriticalcomponents.(1)Selectingthespacecraftkillleve1.Identificationofthecriticalcomponentsisrelatedtotheselectionofthekillleve1.AccordingtoMILSTD一882D31.therearefoursuggestedc
24、ategoriesofmishapseverity(wechoosethemasthekilllevelsofspacecraft).CategoryI:catastrophic;categoryII:critical;categoryIII:marginal;categoryIV:negligible.(2)Determiningtheflightandmissionessentialfunctions.Flightessentialfunctionsarethosesystemandsubsystemflmctionsrequiredtoenableaspacecrafttosustain
25、controlledflight.Missionessentialfunctionsarethosesystemandsubsystemfunctionsrequiredtoenableaspacecrafttoperformitsdesignatedmission.Theanalysisfortheessentialfunctionsshouldconsidereachphaseofthemission.Forexample,atypicalmissionforaspacecraftcouldincludesuchphasesasbefore-launching,propelling,orb
26、italoperating,returning,andlanding.(3)Determiningthesystemandsubsystemfunctionsthatcontributetotheessentialfunctions.Theabilityofthespacecrafttoflyandtoconductitsmissiondependsuponthecontinuedoperationofthosesystemsthatprovideorcontributetotheflightandmissionessentialfunc-tions.Ageneralexaminationof
27、eachsystemandsubsystemonthespacecraftmustbeconductedtodetermineitsspecificcontributiontotheessentialfunctionsidentifiedintheprecedingpro-cessforeachphaseofthemission.Thebasicsystemsofspacecraftincludesuchsystemsasstructure,energy,movementcontrol,heatcontrol,tracking,remoteorbiting,remotecontrol,prog
28、rammingcontrol,andsoon.(4)Conductingadamagemodeandeffectsanalysis(DMEA).ThroughaccomplishingaDMEA,wecanknowtherelationshipofdamagemodesofeverycomponent/subsystemandtheessentialfunctions.TheitemsinDMEAworksheetaresomewhatliketheitemsinFMEA141(Failuremodeandeffectsanalysis)worksheet(seeFigure3).Themai
29、ndifferenceliesinthedamagemodeinDMEAandthefailuremode,whichisoftenidentifiedinreliabilityanalysis,inFMEA.Failurereferstothemalfunctionofproduct/componentinthenormalenvironment.ButdamageinsurvivabilityreferstothekillofthecomponentwhenthethreatspacedebrishitsPeiY.eta1.SurvivabilityAssessmentMethodofSp
30、acecraftattheThreat207spacecraft.Spacedebrisposestheobvioushazardofpenetratingspacecraftsurfaces,producingdamagetoexternalandinternalequipment,decompressingpressurizedvolumes,andgeneratingplasmapulsesthatCancausearcingandburnoutofelectricalandelectroniccomponents.ig.3ItemsinDMEAworksheet(5)Performin
31、gdamagemode,effects,andcriticalityanalysisfDMECA).CriticalityAnalysis(CA)referstotheestimationofeverydamagemodeofcomponentSOastoevaluatethedamageeffectsonspacecraft.ThecombinationoftheDMEAandCAisthedamagemode,effects,andcriticalityanalysis(DMECA).DMECACanbequalitativeand/orquantitative.Whenthedamage
32、rateandconfigurationdataofcomponentisunknown,qualitativemethodCanbeused;otherwise,criticalitynumberCanbecalculatedandthusquantitativemethodCanbeadopted.1)QualitativemethodWesuggestthefollowingfivelevelsofdamageprobabilityofoccurrencereferringtothefivelevelsoffailureprobabilityofoccurrenceinFMECAM】:l
33、evelA(Frequent),levelB(Probable),levelC(Occasiona1),levelD(Remote),andlevelE(Improbable).2)QuantitativemethodsThepurposeofquantitativeDMECAofcomponentistocalculatethecriticalitynumberCrgivenaparticularkillleve1.ThecriticalitynumberCforacomponentisthenumberofdamagesexpectedforagiventimeduetothecompon
34、entSdamagemodesunderaparticularkillleve1.isgivenbytheexpression】:n=0.岛?tj=1where,nisthenumberofdamagemodesunderthesainekillleve1.isthecomponentdamageratio.(4)JournofSyStemsScienceandInformationV_01.4N0.2ble1ThevaluesDamageeffectActualloSSProbablelossPossiblelossNoeffectfvalues1.00.11.00.00.10.0isdam
35、agemoderatioortheprobability,expressedasadecimalfraction,thatthecomponentwillbekilledintheidentifiedmodej.8jistheconditionalprobabilityofmissionlossgiventhatthedamagemodejhasoccurred.ThesuggestedvaluecanbefoundinTable1.isthedurationofapplicablemissionphaseusuallyexpressinhoursornumberofoperatingcycl
36、es.(6)Drawingthecriticalitymatrix.Thecriticalitymatrixprovidesameansofidentifyingandcomparingeachdamagemodetoallotherdamagemodeswithrespecttokilllevels.Theresultingmatrixdisplayshowsthedistributionofcriticalityofcomponentdamagemodesandprovidesatoolforassigningcorrectiveactionpriorities.Thematrixisco
37、nstructedbyinsert-ingdamagemodeidentificationnumbersinma-trixlocationsrepresentingthekilllevelinthehorizontalaxisandeithertheprobabilityofOC-currencelevelorthecriticalitynumber()forthecomponentSdamagemodesintheverticalaxis.AsshowninFigure4.thefurtheralongIncre,amgCriticalityBI./I/Fig.4Exampleofcriti
38、calitymatrixthediagonallinefromtheoriginthedamagemodeisprojected,thegreaterthecriticalityandthemoreurgenttheneedforimplementingcorrectiveaction?TheexampleinFigure4showsthattheprojectionlengthOBislongerthantheprojectionlengthOA,80thecriticalityofdamagemodeBismorecritica1thanthecriticalityofdamagemode
39、A.4.3?GettingtheDamageRatioofEachComponentTheequation(4)iscalculatedassumingthatInfact,thedamageratioofeachcomponentthedamageratioofeachcomponentisknownfirst.isdependentonthelivefiretestofcomponentsorthegatheringofdamagedata.Sincethevulnerabilitytestisveryexpensiveandthedamagedataislimited,thedamage
40、ratioofeachcomponentisverydifficulttoget.Weintr0duceanexpertsystemusingtherelevancematrixevaluatedmethodstosolvetheproblemofgettingthedamageratioofeachcomponent.Invitingsomeexpertstofillintheexpertanalysistable,whichconsidersmanyfactorssuchasthecomponentssizes,shieldingandcomplexitythataffectthedama
41、geratio,wecangettherelativevalueofdamageratioofeachcomponent.LetAI,A2-.?,Ambemcomponentsofspacecraft;,.,%bethe扎ftorswhic王laffectsthedamageratioofeachcomponent;,.,betheweightofeverytorwhichBCDE_I9毒,Ioo矗.IJlIoo(v言每oJPeiY.eta1.SurvivabilityAssessmentMethodofSpacecraftattheThreat209canbedeterminedinrefe
42、rence15;Ykobetheevaluatedvalueofcomponentiwhithrespecttofactorxjinthekthexperttable;J)塘betheevaluatedvalueofcomponentiwhichcanbecalculatedinTable2.Table2ThekthexperttableA1ii121Dlk=W1Vk11+W2Vk12+Vk1A221222J2D2W1Vk21+Vk22+Vk2礼:A竹1m1m2JmnD竹1k=厂1Vk竹11+厂2Vk2+竹1canbedeterminedusingthefollowingrule.Givent
43、hefactor,wecanrankthecomponentbasedon1-10scaleaccordingtothedamageratiovalues.Thecomponentwiththemaximumdamageratiovaluecanberanked10;thecomponentwiththeminimumdamageratiovaluecanberanked1.Basedonexpertanalysistable,damageratiovalue入肌ofcomponentAiisexpressedas入m=D=iqwhere,J)i=Dik,Dmax=max(Di),qisthe
44、numberofexperttable=1(5)4.4.SpacecraftGeometricDescriptionThemasking/shieldingrelationshipamongcomponentsofspacecraftexistsinthepossiblethreataspectsofspacedebris.Forthepurposeofprotection,itisnecessarytoprovidethegeometricdescriptionforvulnerabilityassessment,namelycalculatingtheprojectedareas/over
45、lappingareasofcomponentsanddeterminingthemaskingorpartialmaskingrelationshipamongcomponents.Basedonfiniteelementsmodelofspacecraft,Figure5showsthegeometricdescriptionflowchartofanalgorithmcalledshotlinescanningmethod【,引.Thepreparationoftheorig-inalmodelofthealgorithmisbuiltinsomefiniteelementsoftwar
46、esuchasMSC/PATRANorNASTRAN.Thealgorithmsuperimposesaplanargridwithchangeablegridcellsizeovereachcomponentandgeneratesashotlineineachgridcel1.Thecoordinatesofintersectionpointofshotlineandeachquadrilateralfiniteelementintheoverlappingareaarerecordedtodeterminethemasking/shieldingforcomponents.Through
47、scanningthecomponentssurfacesfromshotline1toshotlineN,thenumberofgridcellsonthecomponentiscountedandmultipliedbythegridcellareatodetermineitspresentedareaandoverlappingarea.210JournalofSystemsScienceandInformationVo1.4No.2lBuildingthefiniteelementm.del1上rlConstmclingprojected咄蛐柚dgDeletingDacw删sIInacetotprotrumngpolynlron一厂SupdmrposinggridonspacecraftandproducingNshotliness=lJ:一一n0一Intrsect/oncalculationofshotlineandquadriIaIfinitedement,cumulatingthepresented/over?