ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
j/...i/ /," /, DustCoverforaMarsLander SolarCellExperiment ScottChristiansen" andKurtLankford* Abstract Alightweight, lowvolume dustcoverwasrequired toprotectthreeexperiments located onthetopofthe MarsIn-SituPropellant Precursor (MIP)module ontheMars'01lander. Theneedforacoverwasnot solidified untillateinthedesignphaseand,atthatpointintheproject, therewasnoenvelope planned for acover.Additional spacewasapparently unavailable, giventheverycrowded landerdeck.Thepurpose ofthecoverwastoprevent accumulation oninstrument surfaces ofdustkickedupduringthefinalphase oflanding asthelandernearedtheMartian surface. Thispaperdescribes thedifficult designprocess and theresulting design. Difficulties withperformance andmaterials thatoccurred duringmanufacture and testarealsodiscussed. Resolution oftheseissues ledtosuccessful qualification oftheentireMIP module andcoversystem. Introduction Oneoftheexperiment modules tobeflownonthe'01MarsLander wastheMarsIn-situPropellant Precursor (MIP)module. Thismodule wasdesigned andbuiltbyNASAJSCandLockheed Martin. The topoftheexperiment wasutilized forthreeadditional experiments, MarsThermal Environment Radiator Characterization (MTERC), DustAccumulation andRemoval Technologies (DART), andMarsArray Technology Experiment (MATE). Theexperiments consisted ofseveral panelareasdesigned to characterize radiator panelandsolararrayperformance intheMartian environment aswellasassess the effectsofdustaccumulation andpotential mitigation strategies afterlanding ontheMartian surface. MIP, MTERC, DART, andMATEarepartofNASA's planetary exploration program andarepartofaseriesof experiments toassess resource capabilities andpotential risksformanned exploration ofMars. MTERC ExperimentMATEand DART Experiments MIPModule Figure 1.MIPEngineering modelshown without coversystem. (MTERC coverorientation was rotated 90degrees intheQualification andFlightunits.) Starsys Research Corporation, Boulder, CO Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 71
coverandprotectsideaspectswouldremaininthefield-of-view ofcellsneartheedgesiftheyweren't movedoutofthewayduringdeployment. Duringdeployment, thecoverwasalsorequired tocontrol the disturbance orre-deposition ofanydustthathadcollected onitduringlanding. TheMTERC experiment included asmall,separate, spring-operated coverthatprotected aportion ofthe thermal radiators. Thissmallcoverwastoremaincloseduntilabouthalfway through theexperiment, then bedeployed toexpose freshradiator surfaces. Thelargerdustcoversystem hadtopassoverthissmaller coverandthencompletely moveawayfromitafterdeployment suchthatthesmaller covercouldoperate without interference. Aswithanycoversystem, thecoverrequired sometypeofdeployment mechanism andcontrollable release mechanism. Sincetheexperiments wouldbeuseless iftheywerenotuncovered, theentire system wasexpected toexhibitahighlevelofrobustness andreliability. Specific Envelope problems Theenvelope volume fortheMIPmodule wasdependent onseveral configurations forthelanderduring themission. •Thefirstconfiguration wasthelaunch andflightmode.Inthisconfiguration, allhardware onthe instrument deckwasstowed andtheaeroshell (aconical upperspacecraft cover)waspresent, enclosing theupperexposure ofthespacecraft. •Thesecond configuration wasthelanding mode.Inthisconfiguration theaeroshell wasjettisoned andthelanding legsweredeployed. •Thethirdconfiguration wasthetransition between thelanding modeandthefully-deployed lander mode.Duringthisprocess several experiments inthevicinityofMIPperformed deployment events andtheRoverwasreleased anddeployed. Thiscomplex combination ofconfigurations created averyrestrictive anddifficult toanalyze mechanical envelope whichmadeacoverinitiallyappear impossible. Threeareasofpossible interference werethe mostsignificant indrivingtheshapeanddeployment aspects oftheMIPcoversystem. .TheMIPmodule wasmounted suchthatalanding legpassed verynearoneedgeandevenslanted overaportion oftheuppersurface ofthemodule. Priortolanding thislegwasextended during deployment whichmeantthatthelegwouldnotbepresent duringcoverdeployment, butalsothatthe dynamic envelope forthelegmotionrequired thatanyMIPcomponents bewellawayfromtheundeployed leg. .Oneofthereasons thattheuppersurface oftheMIPmodule wasstepped wasthatitmustfitunder theconical shapeoftheaeroshell andmaintain aminimal clearance fordynamic envelope. One cornerofthelowersurface wasveryclosetothemaximum envelope allowable tonotcontact the aeroshell duringlaunchdynamic environments. Duringlanding theaeroshell wastobejettisoned and thisenvelope constraint wasnotanissuefordeployment. .TheMIPmodule andRoverweremounted relatively closetoeachotherintheirflightandlanding positions. Although theRoverwastomoveoutofthewaypriortodeployment, theenvelope inthat areawasconsidered off-limits intheeventsomething wentwrongandtheMIPcoverwasrequired to deploybeforetheRovercouldbemoved. Several otherinstruments wereneartheMIPmodule andit wasconsidered undesirable forthecovertodumpdustonanearbyexperiment duringdeployment. 73
Roll-updirection awayfromroverAlmost zero _ clearance with aeroshell ....:....dynamic  envelope Notchfor clearance with deployable landing leg Figure2.Qualification coversystem shownontestfixture. Design Process Establishin.q Envelope /Interface Asdiscussed above, initiallytherewasnospaceavailable (ormassbudget) foracover.Queries tothe organizations involved inmanaging themechanical envelopes allyielded responses thattheirenvelopes wererightupagainst theirneighbor's andtheydidnothaveanysparespacetogive.Theteamwas forcedtotrytolookatthelanderfromasystem pointofviewandidentify available mechanical volumes thatmightnotbeevident whenconsidering individual, simplified envelope definitions. Inreviewing numerous viewsofthelandersolidmodels, itappeared thattherewasroomforacoverifitcouldbe madetoworkaround theunsymmetrically shaped structures andinstruments neartheMIPmodule. It tookameeting ofpersonnel fromNASAJSC,Lockheed Martin-Houston, Lockheed Martin-Denver, and Starsys tobeabletoidentify thatadequate spacewas,infact,available. Thisgroupgathered around a CADworkstation andreviewed theactuallandermodels toidentify components withtheirdynamic envelopes andfindspaces in-between thatcouldallowspaceforthecover. Ultimately thegroup concluded thattherewasroomforanunusually shaped coverandtheprojectmovedforward. AUniqueApproach Atradestudyforapotential coverfortheseexperiments identified aunique, verylight,simplyreleased, self-deploying, roll-up, film-type coverasthebestapproach tomeettheMIPsystem requirements. The roll-upcoverprovided several distinct benefits. •Itrequired veryfewmechanical elements tooperate. Thissaveddesigntime,development time,and reduced mass. •Therollingactionofthecovercouldcapture dustasitrolledup,minimizing disturbances •Thefactthatthecoverrolleditselfupmeantthatthecoverwouldrequire minimal envelope after deployment. •Theminimization ofmechanisms anddrivenelements reduced thepowerandcomplexity ofcontrol electronics required foroperation. •Theshapeandsizeofthecovermadeitextremely adaptable tothecomplex shapeandfunctionality required •Although somedevelopment wasnecessary thesimple design allowed forveryrapiddesign and development tomeetthecompressed schedule ofalastminutecoverprogram. 74
Basiccomponents ofcover Thefinaldesignincluded thefollowing components: •Self-rolling Kapton filmcover-ThemaincoverwasasinglesheetofKapton film.Oneachedgea stainless steelconstant torquespringwasbonded toprovide therollingaction.Across themoving endofthecoverwasanaluminum tubethatserved tointerface withtherelease latchandholdthe endofthecoverduringlaunchenvironments, oprovide somestructural stiffness andmaintain the stowed covershapethecoverwasdesigned tobeshaped inacurve.Additionally twostiffening strips werebonded acrossthecoverintwoplaces. •Self-retracting siderails-Onthetwosidesofthecoverseveral deployable siderailsweremounted totheMIPmodule. Thesiderailswereneeded tosupport theKapton coverabovethesensitive solar cells.Theywerealsorequired tomoveoutofthefield-of-view afterdeployment. Eachsiderailwas mounted onapairofpivotswithtorsionsprings thatwouldcausethesiderailstoflipoutawayfrom theuppersurface experiments. Thesiderailshadtabsontheiredgestoengage withslotsinthe covertocreateastablestructure whenthecoverwasstowed. •Release Latch-TheRelease Latchwasasimpleparaffin actuator powered pin-puller mechanism. Twoparaffin actuators wereutilized toredundantly retracttherelease pin.Whenstowed, therelease pintrapped theTension Barbetween thepinandacradleonthelatchbody.Twoadditional cradles werepresent attheendsoftheTension Bartosupport theTension Barduring dynamic environments. SideRail Engagement TabsRoll-up cover Release Latch SideRailsTension Bar Figure 3.Basiccoversystem components shown instowed position ontestfixture. (Unitshown isthequalification unitinthefinalconfiguration.) Li,qhtwei,qht materials Theoriginal designdidnotinclude massbudget foracover,andthemassofacoversystem wasnot included inthemodule structural designoranalysis. Tomakethecoveraslightaspossible, mechanical components wereminimized andlightweight materials wereusedwherever possible. Thecoverwas fabricated from0.125-mm Kapton coatedwithaluminum ononeside.Thesiderailswerefabricated from Ultem(polyetherimide) andusedsmallaluminum pivotsthatmounted toexisting MIPmodule structural elements. Thetwoconstant-torque springs weremadefrom6-mmwideby0.1-mm thick302stainless steelstrips,Thelatchwasdesigned tobeaslightaspossible whileincluding redundant paraffin actuators. Totalmassofthedelivered flightcoversystem was472grams. 75
Operation Stowed Confiquration Inthecover-stowed configuration thesiderailsweremaintained intheirvertical positions. Thetensioned covercontained several slotsalongeachedgethatinterfaced withmatingsemi-circular tabsontheside rails.Withthecoverinplaceandtensioned slightly, thesiderailswereprevented fromfoldingdown.The covertension wasmaintained bytheclamping actionoftheLaunch Latchonthetension bar.Forlaunch andlanding loadstheendsofthetension barwerepreloaded against apairofsmallcradles outatthe edgeoftheinstrument. TheLaunch Latchalsocontained apairofcontacts thatcompleted acircuit through asmallconductive patchonthecover.Whenthecoverwaslatched inplace,thecircuitwas closed, indicating thatthecoverwasstillstowed inplace. Tension Bar Conductive Contacts Patch Figure4a.Contact switchRelease LatchPin Paraffin Actuators ;................. Preload Cradle Tension Bar Figure4b.Preload Cradle Figure4.Contact switchandpreload cradle; covershown instowed position. Deployment Whendeployment wasrequired apowersignalwassupplied totheparaffin actuators ontherelease Latch.Thelatchutilized redundant actuators topulltheretention pin(eitheractuator couldindependently retractthepin).Uponpinretraction, thetension barwouldbereleased andthecoverwasfreetobegin rollingup.Atthepointthatthespreader barmovedawayfromthelatchthecoverrelease indicator circuit wouldopen,indicating successful release. Theconstant forcesprings thencaused thecovertorollitself up.Duringrolling,thecoverwouldtendtocapture themajority ofdustcollected onit.Withthecoverno longerpresent toholdthesiderailsintheirupright positions, thesiderails"flipped" downintotheir deployed positions. Aftercompletely rollingup,thecovercametorestonthesidepanelontheoutboard surface oftheMIPmodule. Atthispoint,theexperiments wereexposed andreadytoperform their intended measurements. 76
LongSide MTERC Rail SideRail ReleaseLa Short SideRail Cover ._Deployed andatrest Notched SideRail Figure 5.Coversystem components shown incompletely deployed configuration. Development andQualification CoverandSprin.qdesi.qn Thecoverandroll-upspringdesignwasarrivedatbyaprimarily experimental process. General sizingof thekeycomponents wasdetermined asafunction ofthesystem geometry androughcalculations. The intentwastobalance adequate roll-uptorquewithminimization ofsystem energy. Inadequate roll-up torquemightcreateafunctional problem whilehighsystem energy wouldcausehigherdispersion of collected dustandpotential impactproblems attheendoftravelduringdeployment. Damping features suchasVelcrowereconsidered, butthesystem energy wassmallenough thattheadditional riskof damping features wasnotdeemed necessary. Development tests Several prototype coversystems werefabricated toassess theapproach andprovide additional design dataneeded tooptimize thesequenced deployments ofcoverandsiderails.Sincethesiderail deployment wasdependent onthecoverdeployment, interactions between themoving partsneeded to bestudied experimentally. Results oftheprototype testing ledtoseveral designdecisions. Tokeepthe siderailsvertical andstowed smalltabsontheSideRailsmatedwithslotsinthecover(similar tothe holesalongtheedgeofphotographic film).Keyshapes andlocations thatledtoaminimum number of tabswereidentified. Thefinalsystem configuration included fourtabsalongeachedgeofthecover.The finaltabconfiguration wasaflat,semicircular protrusion withtheplaneofthetabparallel tothedirection ofcoverroll-up.Theinterface between theflatsideofthetabandtheslotinthecoverprovided adequate forcetomaintain engagement between thetwopartswhenstowed. Thesemi-circular shapeeliminated a sharpedgeorcornerforthecovertocatchonasitrolledpastthetab. Thenumber ofsidepanelstheirsize,shape, andorientation wasalsodetermined through prototype testing. Atotalof4deployable sidepanelswereutilized tomeetthecombined requirements offullside protection, coversupport, clearance ofthefieldof-view, andnointerference withneighboring envelopes orfields-of-view. TheNotched SideRailmounted alongtheedgeclosest tothelanding leg.Thenotch waspresent toclearthelanding legdynamic envelope. TheNotched SideRailfolded down approximately 110degrees. AtthelatchendoftheNotched SideRailwastheShortSideRail.TheShort SideRailonlydeployed approximately 55degrees andwasnecessary tokeepfromhavingthesiderails onthissideofMIPcontact theAPEXpin-puller. OntheothersideoftheMIPmodule towardthelatchwas theLongSideRail.Thissiderailextended fromthelatchendtotheedgeoftheMTERC coverandfolded down90degrees. Thesethreesiderailsdeployed outward alongthesidesoftheMIPmodule. Because 77
theMTERCcoveralsodeployedinthisdirection,thefourthsiderail,theMTERCSideRail,couldnotbe mountedalongthisedge.TheMTERCSideRailwasmountedonapivotontheendofthemoduleand deployed180degreesoutwardawayfromthemoduleontheendwherethecoverwasattached(see Figure5). Additionaldevelopment testinginvolvedassessingthedispersion ofdustduringdeployment. Dust dispersion testswereperformed underearthgravityandambientairpressure.AnalysisbyJPLof previousmissiondataindicatedthatthetextureofthedustisprobablysimilartothatoftalcumpowderor flour.Forourdusttests,flourwassprinkledoverthecovertosimulateal-ramlayercollectionofdust. Thecoverwasthenreleasedanddeployed.Duringtherollingactionofthecover,mostofthedustwas capturedbetweentheKaptonlayersoftheroll,Arelativelysmallamount(severalpercent)escapedoutof theendsoftherollandwasdepositedontheSideRailsurfacesoneithersideofthetestmodel.Swirling aireffectscausedsomedusttoswirlaroundbehindedgesofthemovingcoverresultinginanextremely smallamount(muchlessthan1%)ofdustbeingdepositedontheedgesoftheexperimental testsurfaces (seeFigure6).Theamountandlocationofpossibledustthatmightbere-deposited ontheMIP instruments wasconsidered acceptable bytheexperiment principalinvestigators. Astherollreachedits stationaryattachment pointittendedtoovertravelanddepositdustfromaportionofthecoveratthebase ofthetestmodel.Thishadbeenexpectedatsomelevelandthedirectionofcoverdeployment hadbeen chosentoassurethatdustre-deposited inthiswaywouldfallharmlessly ontheouteredgeofthelander instrument deck. Figure6.Afterdust-loaded deployment test,dustispresent ondeployed Notched SideRailanda corneroftheexperiment area Dustondeck areabelowfinal cover-deployed position Figure7.Afterdust-loaded deployment testdustispresent ondeckareabelowfinaldeployed position ofcoverroll. 78
Qualification Basedontheprototype unittestresultsaqualification coversystem wasmanufactured. AMIPmodule structural simulator wasbuilttoallowtheproperconfiguration ofthecoversystem. Thesystem wasmade upofsixseparate subassemblies thatreliedontheMIPstructure tosupport andproperly locatethem. Thisstructural simulator wasusedforalltestsincluding vibration, acoustics, andthermal/vacuum. Thequalification unitwastestedaccording toarelatively typicalspacecraft qualification plan.Thetests included vibration, acoustic, thermal cycling (-98Cto+55C), andthermal vacuum functional tests.The unitpassed itsfunctional tests,butseveral characteristics observed duringthetestsledtochanges inthe flightunit.Duringvibration testingthespringguidebushings weredamaged duetointerference withthe pivotattachment features ontheshortsiderail(seeFigure8).Thebushing damage didnotleadtoa functional failure,butthedesignwaschanged toeliminate theinterference andbushing damage. Duringtestingofthisunitasmalltearwasnotedattheedgeononeoftheslotswherethecoverwrapped around thecornerofoneoftheSideRailsatthelatchendofthecover(seeFigure9).Thisareaismore highlystressed thantheotherengagement slots.Theproblem wasresolved bybonding patches of Kapton filmasdoublers around thetwoslotsattheSideRailcorners. Thetearing didnotreoccur during resumption ofqualification testing. Afterqualification testingatacomponent levelatStarsys thequalification coversystem wasdelivered to NASAJSC.Therethesystem wasmounted totheMIPmodule qualification unitandsubjected tosystemleveltestingwiththemodule. Thecoversystem functioned successfully throughout thequalification tests. Afterextended thermal cycling withoperation atlowtemperature inreduced atmosphere (simulation of Marsatmospheric pressure of6Torr),cracking ofseveral Ultempartsatboltedattachment pointswas noted(seeFigure 10).Whilethesystem hadfunctioned properly, thecracking ofthepartswas considered unacceptable. Investigation ofthefailurewasinconclusive astothecause. Differential expansion leading tooverload ofthepartswasconsidered, although thesystem hadbeenexposed to greater temperatue extremes inprevious tests.Lowimpactresistance oftheUltemwasalsoconsidered, butthepartsthatexhibited cracking werenotexposed tothehighest impacts duringdeployment. Without causing excessive delays orincreased costsduetoanextensive investigation, thesolution forthis problem wastoreplace theUltempartsatriskwithaluminum partsofthesamedesign. Thismaintained thefunctionality ofthepartswhileincreasing theirstrength andresistance tocracking. Subsequent tests weresuccessful andthedesignwasadopted forflight. Theflightunitwasmanufactured including important designchanges basedonresultsandobservations obtained duringqualification testing. Thecoversystem hasbeendelivered andhasbeenintegrated onto theflightmodeloftheMIPmodule. Theentiremodule iscurrently beingstoredinanticipation ofafuture flightmission. 79
DamagedPivot Bushing SideRailSideRail Engagement Tab SupportTearin Kapton Kapton cover Figure8.Vibration damage topivotbushing. Figure9.TearatedgeofholeinKapton cover UltemSide Rail UltemPreload Typical cracks Cradle observed onpreload cradles andside rail._ Figure10.Typical cracks observed aftersystem levelthermal qualification testing. 8O
Lessons Spacecraft component mechanical envelopes areoftensimplified anddonotnecessarily reflectthe shapeorexactsizeofthecomponent theydefine. Inaspacecraft assembly thereisoftenspacetobe foundifanaccurate system levelmodelcanbeutilized. Amajordifficulty inworking difficult envelope problems (especially fromasubcontractor point-of-view) istogetalloftheorganizations responsible for theindividual envelopes together toagreethatthespaceactually exists. WhileKapton andUltemarerelatively wellunderstood materials, additional care,analysis, andtestingis extremely valuable whenusingtheminapplications thatmayinduceunusual oruncharacteristic loading. BothUltemandKapton canbeusedinlightweight, structural/mechanical, spacecraft applications if proper precautions aretakenassess theirloadconditions. Inthatthesetwomaterials areplastics and predicting thermal andimpactaffectsisnotexact,testingofthepartsisextremely critical. Failuremodes forthesematerials maybedifferent thanthosetypically considered intraditional analyses. MTERC Side MTERC ExperimentRelease Latch Long MIPModule SideRail Figure12.Qualification unitMIPmodule withcoversystem. Shown instowed configuration duringqualification vibration testing. Summary /Conclusions Givenaverydifficult designproblem theMIPcoversystem wasdesigned andmanufactured tomeetthe restrictive envelope andmassrequirements. TheMIPmodule andcoversystem havepassed qualification testingandflightmodels havebeenfabricated andtested. Themodule wasscheduled tofly ontheMarsSurveyor 2001mission thathasbeencancelled duetochanges inNASA's Marsexploration program. TheMIPmodule maybeincluded inafutureMarsmission, butitisnotspecifically scheduled to beaboardaspecific mission atthistime. 81
SRTMMastDamping Subsystem Design andFailure Investigation JeffreyW.Umland* Abstract Amastvibration damping systemwasdeveloped fortheShuttle RadarTopography Mission (SRTM). The damping system development isconsidered frombothasystem perspective, andadetailed mechanism designviewpoint. Therequirements derivation approach ispresented, starting fromthegeneral instrument requirements, andproceeds tothedetermination ofspecific mechanism design requirements. Key component failuremodesandeffects, aswellasthedesignmitigations implemented, arediscussed. The diagnosis ofthedamping systemon-orbit failureisgiven.Therootcauseofthedamping system failureis provided. Conclusions aredrawntoprovide guidance forfuturedamping system implementations. Introduction TheSpaceRadarTopography Mission (SRTM), illustrated inFigure1,flewinFebruary 2000onthespace shuttle Endeavor astheprimary payload forSTS-99. Theobjective ofthisjointproject between the National Imagery andMapping Agency andtheNational Aeronautics andSpaceAdministration (NASA) wastogenerate anear-global high-resolution database oftheearth'stopography. Thismission madeuse ofInterferometric Synthetic Aperture Radartodigitally surveytheEarth'ssurface fromspace.Theprimary product ofthis11-day mission isatopographic database of80%oftheEarth's landsurface, i.e.,most landsurfaces between +60°latitude. Theresulting digitalterrain datasetprovides asignificant improvement overcurrently existing globaltopography datasets. _i__, Figure 1.SRTMMission Configuration Instrument Overview TheSRTMarchitecture isbasedupontheSpaceborne Imaging Radar/X-band Synthetic Aperture Radar (SIR-C/X-SAR) instruments thatflewtwiceontheSpaceShuttle Endeavor in1994[Jordan, etal,1995]. TheSIR-C/X-SAR project wasacollaborative effortbetween NASA, whichdeveloped SIR-C, andthe German andItalianSpaceAgencies, whichdeveloped X-SAR. TheSIR-Cinstrument wastwoseparate SAR's, whichoperate intheCandL-bands. TheX-SAR instrument operates intheX-band. Thecombined *JetPropulsion Laboratory, Pasadena, CA Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center, May9-11,2001 83