ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
thetestsprovedthattheeffectsofcordconstruction onthefirstharmonicfrequencybecameconstant. Thecorrectionfactorsincorporated intothephysicsequationallowedtheMPMtogiveaccurateand precisemeasurements ofthecordtension. TheMusicalPitchMethoddemonstrated thatitcouldmeasurethetensionintheMAPKevlarcord accurately, astheconversion tablesthatusedtotranslatethemusicalpitchtocordtensionwere calibratedtowithinplusorminus2%.Thismeasurement techniquedoesnotpermanently deformthe cord,thusmakingitmoreaccuratethanthethree-point tensiometer. TheMusicalPitchMethodmetthe projectrequirements basedonitsaccuracyandeaseofuseandwasusedtotensiontheKevlarcordon MAPbeforelaunch. Conclusions TheMAPSARRS operated successfully afterthelaunchofthespacecraft. Thethermal knifesevered the Kevlarcordasdemonstrated inthethermal vacuum deployment tests.TheSAIRRS designandextensive testprogram werethemainreasons foritssuccess. Themethod formeasuring theKevlarcordtension is anewapproach andwasdeveloped atGSFC.Thismethod isapplicable toallarimidcordconfigurations thataretensioned tolevelatwhichanaudible soundismadewhenitisexcited (plucked). Thethermal knifecanbeusedsuccessfully asarelease system asdemonstrated invarious missions including MAP. Inutilizing theknifeandKevlarcordcombination oneshouldbeawareofthepotential problems. TheSARRS designofferssolutions tosomeofthepotential thermal knifeproblems. First,keepthecord diameter toaminimum andprovide enough staintopullthesevered fibersawayfromheaterelement duringactivation. Thisconfiguration willminimize thechances ofthesevered fibersadhering tothetrace priortofinalseparation andcausing damage. Finally, inspect theheaterelement before andafter actuation. Damage tothetraceusually occursduringcordseparation, andsubsequent activation willbe affected bytheexisting damage. AContinuity checkalonemaynotrevealadamaged trace.Thelistof issuesandrecommendations citedinthisreportwerebasedonthefeatures intheSARRS designthat addresses them.GSFCiscurrently compiling theinvestigation resultsofthethermal knifeissuesand solutions fromotherprograms. Thisreportwillbepresented inthenearfuture. References Marion, JerryB.,andHornyak, William F.,"Part1:Physics forScience andEngineering," CBSCollege Publishing (1982)pp.512-519. NASA/CP--2002-211506 255
Release Mechanisms ontheGravity Probe-B Relativity Mission SeanMcCully* andDennisStClair* Abstract TheGravity Probe-B Relativity Mission isscheduled forlaunchin2002.Thespacevehicle iscomprised of adewarmounted intoanaluminum space-frame ortruss(Figure 1).Thispaperdescribes thedesignand testoftherelease mechanisms usedtoconstrain andrelease thesolararraysandattitude reference platforms. Figure1.TheGravity Probe-B Spacevehicle, SolarArrays Deployed Lockheed MartinSpaceSystems Company, Sunnyvale, CA Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/CP--2002-211506 257
Introduction TheGP-Bsolararraysare3.5meters long,weigh330N,andarerotated aboutasingleaxisfromthe stowed todeployed positions wheretheyremainfixedrelative tothespacecraft throughout theremainder ofthetwoyearmission life.Itistypicaltohavesolararrayrelease mechanisms, buttheGP-Bsolution is somewhat uniqueinthatitusestwoshapememory alloyrodsforactuation. Thespacecraft controlgyrosandstartrackers aremounted toanAttitude Reference Platform (ARP)that isfixedtoathermally stablepost.Thispostrequires additional structural support tosurvive launch. The ARPLaunch/Restraint Mechanism (ALRM) wasintroduced toprovide thenecessary constraint changes on-orbit. TheALRMiscomprised ofanupperandlowergrooveplateheldtogether byarestraint rod.The release mechanism isusedtorelease thisrestraint rod. Therelease mechanism forthegravity probe-B vehicle isanimproved version ofapreviously flightqualified design[1].Theloadcarrying capability hasbeenincreased byafactoroffive(to3500N).The mechanisms' release function isfullyredundant bothelectrically andmechanically, andwaseasilyreusedoveronehundred andtwentytimesintwoproto-qualification testprograms. Release Mechanism Design TheGP-Brelease mechanism iscomprised oftwoheat-activated shapememory alloy(SMA)rodswhich begintostraighten whenanexternal temperature of70Cisreached (Figure 2).Eachrodisheldinthe titanium chassis bytwopivotbushings. Therodispinnedtoonebushing andisfreetotranslate inthe other.Astherodsstraighten, thesleeve assemblies separate releasing thetoggleboltthatisheld between them. Figure2.ShapeMemory AlloyRelease Mechanism (SARM) Atoggleboltholdsthesolarpaneltothespacecraft (Figure 3).Thetoggleheadisconstrained between thetwosleevebearing assemblies. Thepreload iscarried through thesleevebearings intothechassis andthenintothespacecraft. Therodsdonotcarryanypreload, andactuation ofeitherofthetworods willrelease thetoggle. NASA/CP--2002-211506 258
/ Figure3.SolarArrayRelease Mechanism Launch Configuration Twoneedlebearings wereaddedtotheheritage designinordertoincrease therelease capability ofthe mechanism (Figure 4).Therodsarecapable of440Nofforceastheystraighten. Byreducing therolling resistance inthisinterface, thepreload couldbeincreased tomorethan3500N.Thehardware was successfully released atacoldtemperature of-78Cwithapreload of7000N(demonstrating amarginof two)usingfirstonerodandthentheotheraspartoftheacceptance testprogram. Thedevelopment program demonstrated release atloadsinexcess of10600N. SECTIONCC Figure4.Sleeve Assembly Theroddesign isidentical totheheritage design (Figure 5).Therodis15cmlongand0.63cmin diameter. Anickeltitanium alloywithatransformation temperature ofapproximately 80Cwasused.A heating element waspottedintothecenteroftherodusingtheheritage process. Therodwasthen conditioned toobtainthedesired "memory". Whensubjected toheat,thematerial intherodtransforms frommartensite toaustenite. Thistransformation resultsinthedesired change incur_/ature. NASA/CP--2002-211506 259
1/:_[-,El_l L;_, ..-E:_'E:::=:THRE;£, PEF ,:,--_--,._, [_E_ ___-:_;, "",. ,/" /'A,,I_ELE¢4_I P.EF ', /'.... "_.. ,/" ,'NIFE Lr_D FEF j ". _....::' z,E_# Figure5.Roddesign Theheating element resistance is22ohms.Anominal busvoltage of28Vacross theheaterdraws approximately 1.2amps(2.4ampstotalpermechanism). Themechanism releases inlessthan120 seconds worst-case (i.e.single-rod, low-voltage, highpreload 3500N). Release Mechanism Test Component levelreleases wereperformed inatestfixturethatsimulated thesolarpanelinterface (Figure 6).Boththeacceptance testprogram andtheproto-qualification testprogram included fivereleases for run-inpurposes atapreload of3500N.Thebaseline functional included threereleases; anominal voltage dual-rod release at3500N,andtwosingle-rod low-voltage releases atapreload of7000N.All environmental testingwasfollowed byarepeatofthebaseline functional test. Figure6.Release Mechanism Installed inTestFixture Toggle preload, rodtemperature, rodvoltage, androdcurrent wasrecorded duringallreleases. These datawereusedtodetermine therelease time,therodtemperature atrelease, andthetotalpowerbeing consumed. NASA/CP--2002-211506 260
Randomvibrationwasaccomplished inthesametestfixture(Figure7).Theproto-qualification test programincludedarandomvibrationlevelof9.2Grms.Theacceptance testprogramsubjectedthe hardwaretoarandomvibrationlevelof6.5Grms.Boltpreloadwasverifiedbeforeandafterexposureto randomvibration. Figure7.Release Mechanism Random Vibration Tests Themechanisms wereacceptance testedthreeatatimeinthethermal vacuum chamber (Figure 8). Thermal vacuum testsresulted inatotalofseven(7)releases; adualrodrelease atbothhot(46C)and cold(-71C)environments, twosingle-rod low-voltage (26V)releases cold,onesingle-rod hotrelease, a dual-rod high-voltage (34V)release hot,andonedual-rod release atthepredicted on-orbit operating temperature (-25C). NASA/CP--2002-211506 261
Vacuumpump(turbo!) Pirani315vacuumsensor HP34970ADataLogger Pirani315vacuumcontroller Vishay2120A 8A02019GSE Timer HP6038A,200W Heatercontrolconsole 8A02410GSE SwitchBox Type-Tthermocouples HPPavilion6470Z 8A02131GSE Vacuumfixture Vacuumchamber Freezer Figure8.Release Mechanism Thermal Vacuum Tests Serialnumber three(3)wasthefirstunittobesubjected toaproto-qualification testprogram. Afternearly completing theproto-qualification testprogram, including overonehundred andtwentyreleases, rodsA andBfailedtorelease inthefinalpost-test single-rod functional. RodBeventually failedduringrepeated attempts tostudytheproblem (Figure 9). Figure9.RodBfailure NASA/CP--2002-211506 262
X-rayimaginghelpedconfirmthattheheatingelementcoilswereincloseproximitytoeachother(Figure 10).Insulationnormallypreventscoil-to-coilcontact.However,itwasdetermined thatthethermallimitsof theheatingelementinsulationis218C.Abareheatingelementwassubjectedto50voltsforover4 minutesatthevendor.Temperatures inexcessof650Cwereachieved.Theheatingelementdidnotfail, buttheinsulationwascharred.Continuedmechanical cyclingwasrequiredbeforecontact(andshorting) betweencoilsoccurred.Thetestprogramwasrevisedtoincludeathermallimitof2"18C. Figure10.X-rayImageoftheRod Arevision inthesleeveassembly designwasrequired toincrease theclearance between thebearings andthechassis. Thefixwasconfirmed byinstalling therevised assembly andsuccessfully releasing rod Aofserialnumber three. Thesleeve assembly design change wasimplemented. Arodtemperature limitof218Cwas incorporated intothetestprogram, andtheredundant modeofoperation became partofthebasic functional thatfollowed everyenvironmental test.Theentireproto-qualification program wassuccessfully repeated onserialnumber two. Aftersuccessfully completing theircomponent levelacceptance testprogram, serialnumbers 7and8 completed thesub-assembly acceptance testprograms oftheALRMwithout anyadditional problems (Figure 11). NASA/CP--2002-211506 263
Figure11. ALRMDuring Random VibeTest Conclusions TheGP-Brelease mechanism hassuccessfully completed aproto-qualification andacceptance test program. Thetworelease mechanisms thatwereinstalled ontotheALRMarenowinstalled onthe spacecraft. Thesolararrayrelease hardware nowawaitsinstallation ontothespacecraft. Themechanism hasproventobeeffective inreleasing preloads of3500Nateventhecoldest ofoperating environments. Acknowledgements TomMcCIoskey provided guidance indesign, process, andtooling. Dennis Petrakis provided guidance in material detailsandperformance expectations. TheGP-Bprogram officeprovided resources and patience asthehardware madeitswaythrough theassembly andtestprogram. References [1] McCIoskey, Tom,"Non-pyrotechnic Release System," U.S.Patent#05192147, 9March1993. NASA/CP--2002-211506 264
Table1.MDSDesign Requirements Parameter Value MaxCapture Distance*: Angular Capture Misalignment Tolerance*: Pitch/Yaw Roll LinearMisalignment Tolerance*: LinearContact Velocity Tolerance*: Preload: Capture Time: Capture andLatchTime: Interface OuterDiameter: Mass: *AIAA:Autonomous "Non-impact" DockingTolerances6.0cm(2.36in) +5degrees _+5degrees +25m(+1.0in) -.005m/s(-.016ft/s) >2224N(>500Ib) <5s <120s <30.5cm(12in) <89kg(20Ib) TheMDSiscomprised ofmanydifferent features, whichwhendescribed, createabetterunderstanding ofthesystem functionality andprovide someinsightastohowdesignobjectives foundtherewayintothe working prototype. Thesesubgroups include: •grappling features (drivetrain, linkages) •system alignment features (passive geometry, pin/cone kinematic interface) •fluid/electrical couplings RefertoFigure1forabreakdown ofsystem components. Figure3hasalsobeenincluded toprovide a senseoftheprototype system size. Grappling Features Thereareseveral components thatcreatethegrappling functionality withintheMDS.Theyinclude a1.5:1 translation gearbox usedtotransmit motorpoweroff-axis tothecentral MDSaxisandleadscrew. The motorisabrushless DCgearmotor withadual-stage 49:1planetary gearbox. Included inthemotorisan opticalencoder providing speedandposition feedback toamotorcontroller allowing thesystem tobe operated closed-loop. Thehousing provides astructure toguidethemainmoving structure withinthe mechanism, thepiston(RefertoFigure2).Theleadscrew, @9.5mm (0.38in) witha1.27mm (0.05in) lead (36%efficient), isaxiallyfixed.Bycoupling theleadscrew tothepiston,motormotioncauses thepistonto moveineitherdirection withinthehousing. Attached tothepistonisasetofthreelinkage assemblies that arespaced 120degrees apartaround themechanism. These4-barlinkage assemblies reactagainst a guiderollerthatcauses thespringbiased linkage assemblies tomoveaxiallyaswellastowards the centeraxisoftheMDS.Thismotionallowsthelinkage assemblies tointeract withthepassive geometry. Withasinglemechanical action,theselinkage assemblies provide thecapture, alignment, andlatching forcesrequired tomatethespacecraft. Theselinkages havebeendesigned tooptimize docking motion. Lateral motion (i.e.motiontowards thecenteraxisoftheMDS)wasincorporated tomaximize grappling actionandprevent thedocking eventfrompushing matingspacecraft apart. System Alignment Features Therearetwolevelsofalignment designed intotheMDS.Course alignment isachieved bydrivingthe activesidelinkage assemblies tomatewiththepassive interface trefoil.Thesepassive features, or"pie wedge" sectors, arepositioned 120degrees aparttomatchthe3setsoflinkage assemblies ontheactive side.Asthelinkage armsswingfromthe"ready-to-dock" position (i.e.,armsfullydeployed) tothe "captured" position (i.e.,armsfullyextended intheaxialdirection) (Figure 3),spherical ballendsonthe linkage assemblies reactonthefaceswithinthepassive interface wedgegeometry (Figure 4).These reactions forcebothinterfaces torotateaboutthelongaxisoftheMDSintoalignment. NASA/CP--2002-211506 269
3XLinkageAssy. Passive Interface ActiveInterface I 1XFluidCoupling 2XElectrical Coupling 3XReaction Roller i IPiston Radial/Thrust Ball Bearinq_",_t /'/../ // /, ///" _ /.'_" /// //. -... --,.-1 r., .-_.' ,---_r _tss',,'//,"/' ,",,",",",',,",,",",,',,"4 ,_,/',,,,,,,,,/,,,,',,,,,,,,,'...,,,.,,,/,,,,,,,,,,,,,,j 3XRetention Lip 3XShearCone I 3XShearPin 3XSpringCan (Spring NotShown) GearBoxand Gearmotor ILeadscrew Housing ScrewNut Figure1.MDSCrossSection Finealignment occurs viatheinteraction ofspring-loaded shearpins(active interface) into3-point kinematic loadpoints(passive interface), againspaced 120degrees apart.Eachloadpointlocation is designed toconstrain fromonetothreedegrees offreedom. AllpointsreactforcesintheZ-axis, two pointsadditionally constrain motioninYaxis,andonlyonepointreactsforcesinallthreeaxes(X,Y,&Z, whereXandYareintheinterface plane,andZisintheaxialdirection). Thegeometry ofthislastpointis a45-degree conical pinmating withaconical hole.Thefinalalignment isfineenough toaccurately position matingfluidandelectrical couplings overoneanother priortoactually making coupling contact. Thefinealignment pinsarealsopreloaded against compression springs priortoseating rigidlyand transferring alatching preload fromtheactivetopassive interface. Inthefinalphaseofthedocking process (refertoPhase4ofFigure5),thisaxialcompliance accomplishes twofunctions. First,aparallel interface planeisestablished abovedelicate andsensitive coupling interfaces priortocompleting the docking maneuver. Secondly, thepreloaded pinsprovide thecoupling de-mate force(approximately 44N (10Ib)eachpin). NASA/C P--2002-211506 270
Motor/Linkage/PistonHousing/Piston/Leadscrew Figure2.MotorlLeadscrewlLinkagelPistonlHousing "Ready-to-Dock"10.]q-- "Captured" orFullyExtended Figure3.MDSSystem inVarious Positions Fluid/Electrical Couplings Thedesign incorporates 3locations forfluidand/orelectrical couplings (Figure 4).Because thedesign usesthecenterofthemechanism foractuating thesystem, coupling locations wereplacedconcentrically, inthreelocations, ataradialdistance fromthemechanism central axis.Byusingcompression springs withinthecoupling assemblies, allthreepoints, regardless ofthetypeofcoupling installed, provide a balanced resistive loadduringthefinalmatingandrigidizing. Thisprevents anybinding fromoccurring. Eachcoupling alsohasmicro-alignment features toprovide afinallevelofmating accuracy ateach coupling point. NASA/CP--2002-211506 271
3XKinematic Mounts ,_t 2XElectricalCouplings ActiveSide(Ready toDock)i',_i_i_J Passive Side Figure4.MDSInterface System Operation Togainaclearunderstanding oftheMDSoperation, consider onepossible docking scenario. Two spacecraft (ClientandMicrosat) orbitneareachother,bothwithindependent guidance systems. The Microsat iscommanded toapproach theClientandmaneuver its'activedocking interface withinsome rangeoverthepassive interface oftheClient.Inparallel theMicrosat triggers theactiveinterface to deployfromastowed configuration. Oncefeedback indicates thespacecraft arewithindocking range,the Microsat disables itsguidance system andactivates thedocking sequence oftheMDS.Withinseconds, theMDShascaptured theClientandcontinues tocomplete docking. Thefollowing isasummary description oftheactualMDSdocking sequence (Figure 5). Phase1,Approach Theactivesidelinkages arefullydeployed inthe"ready-to-dock" configuration andbothinterfaces are brought withinthecapture envelope. Assoonasattitude control signals verifyproper positioning, the MDSisactivated. Phase2,Capture Powerisimmediately applied tomotoratfullspeedcausing thepistontostrokeaxiallycausing the linkage assemblies torotatetowardthepassive interface. Asthelinkages engage thetrefoilfeatures in thepassive side,coarsealignment occurs. Thisphaseiscomplete whenthelinkage assemblies arefully extended (Figure 3).Atthispoint,thepassive interface isconsidered captured. Phase3,Retraction Stillatmotorfullspeed, thelinkages withdraw intothehousing pullingthepassive interface withit.The linkage assemblies strokeuntilthepin/cone alignment features haveengaged butthepreload springs underthepinshavenotyetcompressed. Atthispoint,themotorspeedisreduced tominimize pitch/yaw oscillations oftheinterfaces duringthematingcycleofthecouplings. Phase4,Rigidization Themotorcontinues ataslowratedrawing thetwointerfaces together andcompressing theshearpin springs intheprocess. Powerisdiscontinued whenfeedback tothecontrol system senses desired preload atthekinematic shearpoints(thedesignincludes loadsensors atallthreepoints). Atthisstage, thesystem islatched andpreloaded. Transfer ofpower/data orfluidthrough couplings innowpossible without theneedforadditional docking mechanisms. NASA/CP--2002-211506 272
Phase1 Phase2Phase3 Phase4 Figure5.MSDOperation andKinematic Motion Testing Testing oftheMDSwasundertaken toevaluate theeffectiveness, aswellaslimitations, ofthedesign. Thetest program included threesignificant components. •Anoff-load fixturewasdesigned andmanufactured toassistinunderstanding various dynamics ofdocking as wellastoprovesystem abilitytodockandtransfer cryogenic fluids(LN2) •Atestplanwasdeveloped andexecuted totesttheMDShardware inamicro-gravity environment. •Thedesign wasapplied toasoftware simulation package wherefurther information wasgathered onthe effectiveness ofthemechanical system, inparticular, thelinkage system. Off-loadinq Approach Inordertogainageneral understanding ofthedocking system dynamics, aninitialtestbedwas constructed usingasimulated inertiamassandcable/pulley system (Figure 6).Thepassive sideofthe MDSisshown mounted toatip/tiltfixtureonanx-ytranslation stage.Thefixtureandstageallow adjustment ofthepassive halfrelative totheactivehalftoperform various misalignment tests.This passive sideofthefixtureaswellastheassociated fluidandelectrical couplings represents theclient satellite. Thelargetubular structure suspended fromthecablesimulates amicro-satellite inertia approximately equivalent toa50-kgsatellite. Theactivecoupling ismounted tothebottom ofthis structure. Adjustment ofthecableattachment point(universal joint)andoffload weights (shown atthe right)provided acloseapproximation toazero-genvironment. Thistestsetupwasusedforthefollowing tests: •Matingandde-mating oftheinterface undervarious alignment scenarios andcapture rangestoverify docking capability (Testresultsaresummarized inTable2.) •Electrical andfluidcoupler matingandde-mating verification Allcouplings werevisually inspected aftereachde-mate toverifynodamage resulted frommateanddematecycles. Continuity checks wereperformed ontheelectrical connectors oncethedocking interface wasmated. Thefluidcoupler wasverified byperforming liquidnitrogen transfer testsonthemated coupler. Threeliquidnitrogen transfer testsweredemonstrated usingthedevelopmental fluidcoupler installed intheMDS.Duringdevelopment over200mechanical mate/de-mate cyclesweresuccessfully completed. NASA/C P--2002-211506 273
Off-Load ___!MassUniversal Joint/Cable Attachment InertiaMass SimulatorCable/Pulley System i ",_"_ X-YTranslation I___  _1Table _,_z_'_'_'__  . Figure6.MDSZero-G /Off-load TestSet-Up Micro-Gravity Testing Thesecond phaseofMDStesting andevaluation included aflightonNASA's modified KC-135 aircraft nicknamed the"VomitComet" (flownEllington FieldnearJohnson Spaceflight Center, Houston (JSC)). Testswereperformed astheaircraft fliesinaseriesofparabolic maneuvers (3-4setsof10-12 parabolas). Approximately 25seconds ofmicro-gravity followed by30seconds of2-gatpull-up were experienced withineachparabola. Sincetheentiredocking sequence wasapproximately 2minutes long (fromdocking initiation tofinalpreload) theexperiment focused onthegrappling andcapture eventsthat couldbeaccomplished withinthe25seconds zero-gwindow. Theintentofutilizing thisresource wasto betterunderstand thedynamics ofmechanism docking inasimulated micro-gravity environment. Of primeimportance wastodetermine whether ornotthelinkage motionhadatendency topushthepassive interface outofcapture rangeduringthedocking sequence. Table2.MDSSimulated Zero-Gravity Off-load TestResults Requirement DesignGoal TestResults Capture displacement (x-axis) Capture displacement (y&z-axis) Capture RollAngle Capture Pitch/Yaw Angle Preload Capture Time Capture andLatchTime Mass6.0cm(2.36in) 2.54cm(_+1in) _+5° _+5° 2224N(500Ib) <5s <120s 89N(<20Ib)6.3cm(2.5in) 2.54cm(_+1in) (_+5-10°) (_+5-10°) 2669N(600Ib) 3-4s 120s 80N(18Ib) Inordertoperform experiments ontheKC-135, JSC'sFlightSafetyReview Boardmustevaluate test plansandfixturing forsafetyaspartofaTestReadiness Review (TRR).Although adetailed testplanhad beensubmitted forreview, theReview Boardfoundmanypointsofconcern withtheproposed testplan NASA/CP--2002-211506 274