ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Therotationvs.timeresultsfromthismodelcanbeseeninFigure13alongwiththeresultsfromthe undamped test.Thedeployment ismodelledwithgoodaccuracyuptothepointoflocking,but subsequently thesimulationshowsthehingeunlockingandrotatingbacktoarotationofaround20deg andthenoscillatingbackwards andforwardsanumberoftimes,beforefinallylocking.Notethatthe currenthingedesigncanturnonlyinonedirection,andhenceintheoppositedirectionitisabletoresista verylargemoment. 180[_ ." ---- Experiment 160I _:...... !'_ msimulation 14o,_.......:. .!......:... 12o,',!.....• .:...._• ,ooR.............sol......\,,./.............\.t .....:\",I...............\'t4°I.....\"/; i....::\2o .,.,i....i.....i. 0 1 2 3 4 5 6 Time(s) Figure13.Comparison ofrotation vs.timeresponse toPro/Mechanica simulation Thisdifference inthepost-locking behavior couldbeduetoanumber offactors, suchas: •Damping withinhinge.Atlocking therecouldbesignificant damping present duetostretching of thewires,compression ofthehingewheels, stretching ofthetapesorslipping oftheconnections. •Energy lossduetobuckling. •Incorrect modelling ofthemoment-rotation properties ofthehingewherethemoment-rotation properties ofthehingevaryfromthosepredicted bytheAbaqus analysis. •Resistance duringpaneldeployment. Thisresistance couldariseduetofriction withinthehinge orairresistance onthepanel. ShockMeasurements Inaddition tomeasuring therotation ofpanel2,fouraccelerometers wereattached totheapparatus, two toeachpanel,inthepositions shown inFigure14.Thedistance fromthehingeattachment tothe accelerometers wasminimised tomeasure thepeakshocklevels.Theaccelerometer outputs were logged at5000HzusingaPCwithananalogue todigitalconverter boardandaprogram written in LabView (National Instruments, 1998). Theshockresulting fromdeployment ofapanelwithhingeswithout additional damping canbeseenin Figure15.Thehingesdonotlockfullyonfirstdeployment butre-buckle twice;henceatotalofthree acceleration peakscanbeseenintheplots,eachcorresponding tothetapesprings snapping intothe deployed configuration. Themaximum acceleration isapproximately 1500m/s2(150g)andthereislittle difference between accelerations indifferent directions. Theshockresulting fromdeployment ofapanelwithtwo12-mm longpiecesofOasisfoamcanbeseen inFigure16.Thesizeofthefoamblockswasdetermined bysettingthekineticenergy ofthesystem on latch-up (equaltothestrainenergy inthehinges, givenbytheareaunderthemoment-rotation graph) equaltotheenergy required tocrushthefoamtoasizethatallowsfulldeployment ofthepanel.The panelnowlocksthefirsttime,without re-buckling thetape-spring hinges, andthemaximum acceleration NASA/C P--2002-211506 47
isreducedtoapproximately 600m/s2(60g).Successful deployment ofthepanelwasfoundtobevery sensitivetothelengthofthefoamblocksused.Forexample,whenthelengthwasincreasedto12.5mm thepaneldidnotlock;ideallyalargerpieceoflessdensefoamwithalowercrushingstressshouldbe used. P_anel 1 '-%":_::(_A2 _"_" IIAccelecometers ...::it': Figure14:Accelerometer positioning. Theshockresulting fromthedeployment ofapanelwith3M434sounddamping tapeattached toboth sidesofeachtape-spring canbeseeninFigure17.Themaximum shockisnowaround 250m/s2(25g) inaldirections. Conclusions Thehingepresented inthispaperissignificantly lighterandsmaller thanprevious designs. Italso provides predictable moment-rotation andstiffness properties. Ithasbeenusedasthedeployment mechanism infull-size verification models ofSARsandSolarPanels. Thedeployed stiffness properties ofthehingecanbepredicted analytically withgoodaccuracy, andthe equations thathavebeenpresented canbeusedtotailorthestiffness properties ofthehingetoagiven setofrequirements. Modelling thefullmoment-rotation relationship ofthehingewithgoodaccuracy hastotakeintoaccount theeffectofcontact between thetapes,whichwasachieved withafiniteelement analysis. Arelationship obtained thushasbeenusedtosuccessfully predictthedeployment dynamics ofastructure containing TSRhinges, however theprediction oftheamount ofenergydissipated withinthehingeduringlatching is anareawherefurtherworkisneeded. Fromapractical viewpoint, ithasbeenfoundthattheaddition of damping tapeismoreeffective atreducing shockthandamping foam.Damping tapegivesasix-fold reduction intheimparted shockoveranundamped hinge.Noneofthedamping systems testedhaveany effectonthelarge-scale rotation-time properties. Acknowledgments Theworkpresented inthispaperwasfunded bytheBritishNational Space Centre andtechnically supported byASTRIUM UKLtd.Wethankthetechnical monitor, MarkRoe,foradviceandmanyvaluable suggestions. Financial support fromtheScience andEngineering Research Council, intheformofa studentship forA.M.W. isgratefully acknowledged. NASA/C P--2002-211506 48
1500 5OO -5001000 ............................... -1000 ............................ i........ -1500 15000 0.1 O2 0.3 Time(s) 1000 .................................. 500["hi...... < -500 -1000 ..........................................: i -15001500 1000 500 o Ol < -500 -1000 -1500t i ! ........ 0 0.1 0.2 0.3 Time(s) 1500 Ji 1000 ......... 500 E_0 -500 -1000 ........ !........ i...... -1500 0 0.1 0.2 0 0.1 0.2 0.3 0.3 Time(s) Time(s) Figure15.Locking shockforpanelwithnodamping 1500 I 1000 ....  o.......-500 ............. i ............. -1000 ............... i........... :........ -1500 15005OO E0 -5001500 i 1000 ..................... !............. -1000 .......... :........... :........... -1500 0 0.1 0.2 0.3 0 0.1 0.2 0.3 Time(s) Time(s) 1000 ................................................ 500 ................................................ o -500 .................................... -1000 ................................................ -150O1500 1000 ................................................. 0-500 -1000 ................................................ -1500 0 0.1 0.2 0.3 0 0.1 0.2 0.3 Time(s) Time(s) Figure16.Locking shockforpanelwith12-mm Oasisfoam NASA/CPD2002-211506 49
1500 1000 5OO I -500i -1000 : i -1500 I 0 1500r--- 1000 500 E0v 2 -500 -1000 -150015ooIL 1000: 500E0 '_'_"......-..................................... -50001 Time(s)0.2 03-1000 -i -1500 •....... 0 01 1500i-! ! looo L0.2 03 Time(s) 500E0 _, -500- -1000 ! -1500 i 0 0 0.1 0.2 0.3 0.1 0.2 0.3 Time(s) Time(s) Figure17.Locking shockforpanelwith3M434sounddamping tape References Auternaud, J.etal.(1992). Selfmotorized antifriction jointandanarticulated assembly, suchasasatellite solarpanelequipped withsuchjoints,U.S.Patent5,086,541. February 11th,1992. Chiappetta F.R.,FrameC.L.,Johnson K.L.(1993). Hingeelement anddeployable structure including hingeelement, U.S.Patent5,239,793. August 31,1993. Chironis, N.P.andSclater, N.(1996). Mechanisms andmechanical devices sourcebook. Second Edition, McGraw-Hill, NewYork. Hibbit,Karlsson andSorensen (2000). ABAQUS Version 6.1.0.Pawtucket, RI02860. Hilberry B.M.andHallA.S.(1976). Rolling contact prosthetic kneejoint,U.S.Patent3,945,053. March 23rd,1976. Johnson, K.L.(1987). Contact Mechanics, Cambridge University Press,Cambridge. National Instruments (1998). Labview Version 5.0.1. Parametric Technology Corporation (2001). Pro/Mechanica 2001,140Kendrick St,Needham, MA02494. Pellegrino, S.,Green, C.,Guest, S.D.andWattA.(2000). SARAdvanced Deployable Structure. CUED/D-STRUCT/TR191, Department ofEngineering, University ofCambridge. Seffen, K.A.andPellegrino, S.(1999). Deployment dynamics oftapesprings. Proceedings oftheRoyal Society ofLondon, seriesA,455,1003-1048. Vyvyan, W.W.(1968). Self-actuating, self-locking hinge,U.S.Patent3,386,128. June4th1968. NASA/CP--2002-211506 50
Material Property Effects onCoaxial CableMechanical Failure R.B.Pan*,J.B.Chang*, C.C.Wan*,Y.R.Takeuchi*, R.McVey**, andI.Chen*** Abstract Aspaceflight coaxial cableexperienced mechanical failureat0.1xlifetime duringthequalification lifetest. Destructive physical analysis (DPA)performed onthefailedcablerevealed signsofmassive coldwelding between thesilverplatedcopperwirebraidandthesilvered platedcopperfoilwrap.Alsoobserved wasthe foil-to-foil coldwelding inthefoilwrapoverlap regions. Hardness measurements indicated lowhardness values inallcopper elements thatincluded thewirebraid,foilwrapandcenterconductors. Thispaper presents theDPAresultsandpostulates afailuremechanism thatrelateslowyieldstrength associated with thelowhardness valuestothecoldwelding ofsimilarmaterial attheinterface, rapidinitiation ofmultiple cracksitesandfastcrackpropagation. Introduction A4.8-mm (0.19-inch) diameter coaxial cable,fabricated byManufacturer Aandidentified asA190A, failedat0.1xlifetime duringthequalification lifetestconducted inlate1999.Figure1showsthehelically coiledconfiguration ofthecoaxharness. Abundle ofdirectcurrent (DC)twisted shielded pairs,seen behind thecoaxharness, isinstalled through thecenterofthehelix.Thisentireharness assembly is mounted insidetheshaftofadirectdrivetorquemechanism, oneendattached totheshaftandtheother attached tothehousing. Thelifetestmotion profilewasdesigned toevenlydistribute direction reversals anddegrees ofmotionthroughout theentiremechanism travelrangeof+150degrees. Onelifeconsists of120-million degrees oftraveland1.5-million direction reversals. Therequirement foraflightcoaxial cableinthequalification lifetestissuccessful completion of2operational lives. Figure2showsthetestarticleplaced insidethethermal vacuum chamber. Asuccessful testruns continuously for2months, withpressure maintained atlessthanlx10.6torrandtemperature ofthecoax harness controlled between 40°and120°F.Throughout thelifetest,criticaldatasuchasradiofrequency (RF)performance, hysteresis torqueplots,andDCcontinuity arerecorded onadailybasis. Thistypeofcoaxial cableharness isusedinspaceforhighfrequency, low-loss applications. Thecable consists offiveelements: afluorinated ethylene propylene (FEP)outerjacket,asilver-plated copper wire braid,asilver-plated copper foil,apolytetrafluoroethylene (PTFE) tape-wrapped dielectric core,anda strandoftwisted silver-plated copper centerconductor. Figure3showsthecrosssection viewofthe A190Acoaxial cable. Aliterature surveyuncovered asimilarcoaxial cablefailurereported byChiu(Reference 1).Coldwelding apparently caused somedamage totheouterjacketofthecoaxial cablesandresulted inunacceptable RFperformance. TheAerospace Corporation, ElSegundo, CA Boeing Satellite Systems, ElSegundo, CA Raytheon Systems, ElSegundo, CA Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/CP--2002-211506 51
Figure3.CrossSection ViewofA190A Coaxial Cable Failure Investigation Inspection ofthefailedA190A coilrevealed thatthewirebraid,thefoilwrapandtheFEPjacketwereall broken atacommon location (Figure 4).Signsofmassive coldwelding between components were observed inthebroken region. Destructive physical analysis (DPA)wasperformed inordertoseekthe rootcauseofthefailure. Samples cutfromboththecoilsection (CS)andthestraight section (SS)of A190A wereexamined withlowpoweroptical microscopy, fine-focus x-rayandscanning electron microscopy (SEM)techniques. Signsofmassive coldwelding werefoundatthewirebraidtofoilwrap interface inA190A/CS (Figure 5).Inafewplaces, wiresfromthewirebraidbonded sostrongly tothefoil wrapthattheycouldnotbeseparated fromthefoilwrapwithout damaging thefoil.Anexample ofwire braid-to-foil typecoldwelding wasillustrated inFigure6.Afterthewirebraidswereremoved fromthe coaxial cablesample, multiple circumferential crackswereobserved alongtheoverlap boundary ofthe wrapped foil(Figure 7).Itwasfoundthatthefoilwasdifficult toseparate duringsubsequent foilunwrap attempt. Insomecasesthefoilwastornduringtheunwrap operation. SEManalysis onunwrapped foil surface clearlyindicated thatafoil-to-foil typecoldwelding hadtakenplaceintheedgesofthefoiloverlap region. However, inthenon-flexing section ofthecoil,i.e.,testsample A190/SS, nosignofeitherwireto-foilorfoil-to-foil typecoldwelding wasfound. NASA/CP--2002-211506 53
Helicallyformed,3-mm(0.120-inch) diametercables,fabricatedbyManufacturer A,werealsoobtained forthisinvestigation. Thesecableshadpassed2.0livesinthelifetestandwereidentifiedassamples A120.CracksalongtheedgeoffoiloverlapwereagainfoundintheA120/CStest,.samplesalthoughthe cracklengthandthenumberofcracksappearedtobeshorterandlessinfrequencythanthosefoundin sampleA190A/CS. However,therewasnosignofwirebraid-to-foil coldweldingintheA120/CSsample. LikeinthecaseofA190A/SSsample,neitherwiresbraid-to-foil norfoil-to-foilcoldweldingwasfoundin A120/SSsample.Table1summarizes theinspectionresults. Microhardness measurement usinganappliedloadof25gramswasconductedonallcopperelements,i. e.,wirebraids,foilwrapandcenterconductor,oftheA190AandA120samples.Hardnessmeasurement wasalsoconductedonsamplesfromtwoother4.8-mm(0.190-inch) diametercablesmanufactured at earlierdatesforcomparison. ThesesampleswereidentifiedasA190-'97LotandA190-'80Lot.Asa reference,hardnessmeasurement wasdoneonsamples,identifiedasB197,ofcoaxialcablesfabricated byManufacturer B.Table2summarized thehardnesstestresultsfromthisinvestigation. Here,the microhardness valueswereconvertedtostandardRockwellhardnessB(RB)valuesforconvenience. Resultsshowedthat,exceptforsamplesfromtheearlyproductionA190-'80Lot,theRBvaluesofcables suppliedbyManufacturer AaregenerallylowerthantheaverageRBvaluesfromcablessuppliedby Manufacturer B.ThemostnoticeabledifferenceisinthefoilwrapofthefailedA190A/CSsample. Figure6.BraidWireStillBonded totheFoilafterBraidRemoval Failure Mechanisms Postulation Forthesamples takenfromthestraight section andthecoilsection ofthefailedcable,andothertested cables,thefollowing areobserved: (1)Straight section samples donotshowanysignofcoldwelding, possibly because thefoiloverlap regions arerelatively freetomove. (2)Coilsection samples always showsignsofcoldwelding inthefoiloverlap regions afterlifetest. (3)Thecoilsection ofthefailedcableexperiences massive coldwelding between thewirebraidandfoil interface. NASA/CP--2002-211506 55
(4)Hardnessvaluesofwirebraid,foilandcenterconductorfromthefailedcablearelow,especially thosevaluesmeasuredinthefoil. Table1.Inspection Results SAMPLE/ SECTION A190-A/CSTESTHISTORY Failedat0.lxlifeINSPECTION RESULTS •Massive coldwelding wasfoundatwire braid/foil andfoil/foilregion •SEMstakenfromfoilsrevealed manycracks A190-A/SS Failedat0.lxlife Nosignofcoldwelding A120/CS Passed 2.0xlife Signsofcoldwelding andtearswerefoundalong theedgeoffoiloverlaps A120/SS Passed 2.0xlife Nosignofcoldwelding Table2.Rockwell Hardness B(RB}ValueComparisons MEASURED WIREBRAID FOIL CENTER SAMPLES CONDUCTOR A190A/CS 45.6+2.2 22.7+2.61 46.5_+2.0 A190-'97 Lot 44.8+2.1 46.9+1.7 53.6+1.8 A190-'80 Lot 66.2+1.4 74.9+0.83 47.3+1.6 47.0_ A120 47.0 42.0 BCables 59.6 49.5 62.8 (Aveof8Lots) B197 58.7 49.6 62.7 Note:(Reference 2) 1.YieldStrength =69MPa 2.YieldStrength =275MPa 3.YieldStrength =345MPa Figure7.Multiple CrackSitesDevelop intheFoil NASA/CP--2002-211506 56
Conclusions Fromtheresultsofthefailureinvestigation, thefollowing conclusions aredrawn: •Coldwelding orRFfailureoftheelements madeofsilverplatedcopper islikelytooccurforthe currentA190Acoaxial cabledesigninaspaceapplication. •Coldwelding asseeninthefoilregiondidnotleadtomajordamage andRFfailureoftheA120 coaxial cableinthedesired lifespan.Thesmaller coaxcablesizeandincreased foilhardness are apparently important factorsinreducing cablestress. •Lowcoaxcablefoilhardness maybeacontributing causeofserious coldwelding leading toearlyRF failure. Lot-to-lot hardness measurements arehighlyrecommended. 3.0 o 2.5 ._ 13 20 rn >._ '_1.5 r_ 1.0 0 20 40 60 80 Number ofwires per layer Figure8.Relative Bending Moment vs.Number ofWireBonded perLayer . . ,References M.Chiu,"Coaxial CableFailure inaSpacecraft Mechanism", Proceedings ofthe34thAerospace Mechanisms Symposium, Goddard SpaceFlightCenter, May10-12,2000. Simon, N.J.,Drexier, E.S.andReed,R.P.,Properties ofCopper andCopper AlloysatCryogenic Temperatures, NISTMonograph 177,February 1992. P.C.Paris,TheFracture Mechanics Approach toFatigue. Fracture-An Interdisciplinary Approach, Syracuse University Press,1964. ElHaddad, M.H.,Smith,K.N.,andTopper, T.H.,"AStrainBasedIntensity FactorSolution forShort Cracks Initiating fromNotches", ASTMSTP677,C.W.SmithEd.,American Society forTesting and Materials, 1979. NASA/CP--2002-211506 58
Appendix A Themoment needed tobendthecablearadiusofcurvature, p,wascalculated usinganalytical methodology basedonclassicstrength ofmaterials. AsshowninFigureA-l,thecoaxial cables consist ofthecentral conductors, dielectric material, flat braids,roundwirebraids, andajacket. Thereareatotalof72roundwirebraidsintwolayers.Over multiple cyclesaprogressive number ofroundwirebraidsbondwiththeflatbraids, causing thecableto become stiffer.Consequently, themoment needed tobendthecableagivenradius, p,increases. The roundwirebraidsincontact withtheflatbraidsiscalledlayer1andtheouterwires,layer2. Tostart,themoment needed tobendacablewithnobonded wiresis: Eili M=). i=1PiEqn1 Where nisthetotalnumber ofcomponents, including centerconductors, dielectric, flatbraids, round wirebraids,andjacket. EiistheYoung's Modulus ofthecomponent, i. liistheareamoment ofinertiaofthecomponent, i. Piistheradiusofcurvature ofthecomponent, i. However, theradiusofcurvature islargecompared tothediameter ofthewire,so p_=PEqn2 then Eili Eqn3 M= i=l P Equation 3represents themoment needed tobendacablewithnobonded components toaradius of curvature, p.Tocalculate thechange inmoment needed tobendthecabletothesameradius of curvature aftercoldwelding, afewassumptions weremade. Inallcases, theflatbraidwasassumed to becoldwelded, therefore, modeled asatube.Furthermore, coldwelding wasassumed tooccurinboth layersoftheroundwirebraids. If,forinstance, fivewireswerecoldwelded totheflatbraids inlayer1, thenfivewireswerebonded tothewiremeshinlayer2.Next,thebonded wireswereassumed tobe equally spaced apart.Finally thewireswereassumed tobestraight. Forthecasewherenowiresarebonded, thebending ofeachcomponent (andtherefore itsneutralaxis) isaboutitsowncentroid. Oncethewiresarebonded, however, theneutral axisisnolongeratthe component's centroid. Instead, theneutralaxisisaboutthebonded structure's centroid (inthiscase,the cable),resulting inhigherstresses intheouterwires.Theeffectthishasonthebending moment canbe calculated bythefollowing equations: MtotaI=M.+MbEqn4 WhereMuisthemoment duetotheunbonded wiresandothercomponents andMbisthemoment dueto theflatbraidsandbonded wires,whichcanbeexpressed bythefollowing equations. NASA/C P--2002-211506 59
£E_I_+£EjIj i=1 j=lEqn5 where pistheradiusofcurvature tothecenterofthecable. misthenumber ofunbonded wires. nisthetotalnumber ofotherunbonded components including thecentralconductors, dielectric, andjacket. E_istheYoung's Modulus oftheunbonded wires. liistheareamoment ofinertiaoftheunbonded wires. EjistheYoung's Modulus oftheotherunbonded components including thecentral conductors, dielectric, andjacket. Ijistheareamoment ofinertia oftheotherunbonded components including thecentral conductors, dielectric, andjacket. Theadditional moment needed tobendthecableduetothebonded wiresis: q EkIk mb=k=l PEqn6 where 9istheradiusofcurvature tothecenterofthecable. qisthenumber ofbonded wires. EkistheYoung's Modulus ofthebonded wires. Ikistheareamoment ofinertiaofthebonded wires. Thekeydifference between thebonded andunbonded wiresisthecalculation ofthemoment ofinertia. Whiletheareamoment ofinertiaintheunbonded wireiscalculated aboutitscentroid, theIkofeach bonded wireiscalculated usingtheparallel axistheorem. Forlayer1andlayer2,theareamoment of inertiais /k1--Ix+A.II Eqn7 lk2=Ix+A._? Eqn8 where Ixistheareamoment ofinertiaofthewireaboutit'scentroid. Aistheareaofthewire. rlandr2isthedistance fromthecenterofthecabletothecentroid oftheroundwirebraid. Thedistance rlandr2canbecalculated bythefollowing equations: D rj=(_f+2 -)'sin(_--+m2(i-1)'_---)mEqn9 D_ /3 7/7Eqn10 r_=('+D+_--).sin( +2-(i-1).) -2 2 m m where Dfistheouterdiameter oftheflatbraids. Disthediameter ofthewires. NASA/CP--2002-211506 60
rlisthedistancefromthecenterofthecabletothecenterofthewireinlayer1. r2isthedistancefromthecenterofthecabletothecenterofthewireinlayer2. Usingtheaboveequations,onecancalculateMtotaIasafunction ofthenumber ofbonded wires. Jacket FlatBraid RoundBraidWiresinLayer1 RoundBraidWiresinLayer2 FigureA-1.Components intheA190A Coaxial Cable NASA/C P--2002-211506 61
Design andTesting oftheCRISPTracking MirrorCoverandRelease Mechanism . • JeffreyLeesandEdSchaefer Abstract Thispaperwilldescribe thedesignandqualification testingofadeployable coverandrelease mechanism fortheCombined Remote Imaging Spectrometer (CRISP) instrument tobeflownonNASA's COmet Nucleus TOUR(CONTOUR) mission scheduled tobelaunched inJuly2002.Therelease mechanism utilizes redundant HOP(HighOutput Paraffin) actuators torotateacamthatallows 2latches to simultaneously release aspring-loaded cover.Thecoverisathinshellconstructed ofacomposite fabric withabonded titanium hingethatisusedtocoverthetracking mirrorduringintegration/test andlaunch. Thehingeisdesigned toallowthecovertorotatetroughalimitedangleandflyawayfromthespacecraft alongalineartrajectory. Theextensive testprogram willalsobedescribed including high-speed video, 1000Hz,andatestflightonNASA's KC-135 Reduced Gravity Experiment plane.Lessons learned will include anexplanation oftheactualangleofdeployment andwhyitvariedfromthe"as-designed" angle. Figure1.CRISP Instrument JohnsHopkins University Applied Physics Laboratory, Laurel,MD Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/C P--2002-211506 63
Release Mechanism Themostconvenient location toplacetherelease mechanism wasinapocket, directly underthemotor. Thesizelimitations ofthepocketimposed achallenge topackage arelease mechanism withredundant actuators ina120(I)x48(h)x38(d)mmvolume. Inaddition, itwasdetermined thatasinglepointof release wouldnotbepractical. Aphilosophy wasadopted thatbothlatches should bereleased bya common component directly coupled totheactuators. Withtherequirement.,; defined, arelease mechanism wasdeveloped thatutilized identical redundant actuators thatcoulddriveasinglecam releasing twinlatches simultaneously andfitwithinthepocket. 2xLATCH 2xHOPEXTENSION SENSOR 2xHOP PISTONLATCH SPRING ROLLER TANGENT BAND V CAM Figure2.Release Mechanism Cut-Away Theheartoftherelease mechanism, showninFigure2andFigure13,isacylindrical, O25.4mm, cam withtwo180°opposed Vgrooves. Thecamisdrivenbytheactuator's tangent band,simultaneously or independently, rotating itagainst thetorsion spring. Oncethecamrotates 15°,thecamfollowers are drivenintotheVgrooves, providing aquickrelease. Thetension springs insidethecamfollowers provide aconstant forceagainst thecam.Therefore, alltheforcesactingontherelease mechanism, thesingle torsionspringandtwotension springs, areallinternal tothemechanism, andthemechanism itselfhasno external forcesactingonit. Release Mechanism Actuators TwoEH-3525 highoutputparaffin (HOP)actuators configured withanelgiloytangent banddeveloped by Starsys Research Inc.drivethemechanism, asshowninFigure3.Thetangent bandwasemployed for tworeasons: 1.Toprovide apurelylinearforcetotheactuator 2.Toallowtheactuators tooperate independently Thetangent bandconverts uni-axial HOPmotiontorotarycammotionwithout exerting transverse loads ontheHOP.TheHOPtangent bandsarealsoflexible enough toallowtheHOPstobeactuated independently aswellasaccommodate differential extension oftheHOPswhendrivensimultaneously. TheEH-3525 HOPactuator wasspecifically designed withstringent contamination controlrequirements. NASA/CP--2002-211506 65