ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
(i.e.,high-speedsteppermotorwithavoltage supply). Compared toanon-redundant designbuiltintothe samelamination stack,foragiventorqueoringeneral formotorshavingalineartorque-to-current characteristic, Table1showsthatthe"electrical redundancy" concept doubles thepowerneed. Thetwomechanical redundancy concepts, builtwithintwoseparate magnetic stacks(Figure5&Figure6), leadtoawindings' "endofcoil"lengthtwicethosecompared totheonerelatedtotheelectrical redundancy concepts (builtwithinonestack). Forthetwomechanically redundant options, thisimpliesalarger resistance andthushighercopperlosses: thelongerthemotor's axiallength,thesmaller therelative impactoftheendofcoillengthupontheresistance /powerconsumption. Thisisindirectly showninFigure 10,whichprovides asafunction ofthemotor's axiallengtharelativevaluereflecting theresistance increase. Indeed, itrepresents theevolution oftheratioofthe"resistance oftheelectrically redundant unit/resistance ofthemechanically redundant unit."Evenforrelatively longmotors(upto150mm,or6in),theratio remains below90%andthustheelectrical redundancy concept willoftenbemoreefficient, evenforrather longmotors. Saturated Motor: Torque.-.T_Power Ratio Forasaturated motor,Figure11provides thetorque-to-copper losscharacteristics forthedifferent typesof redundancies. Themostefficient designs are,intheirorderofimportance: (1)thenon-redundant design builtintothesamelamination stack;(2)boththetwo-parallel-wires andtheshared-slots electrical redundancy concepts; (3)thetwo-sector electrical redundancy concept; and(4)boththefullandpartial mechanical redundancy concepts. Itisimportant tonotethatthemotorusedinthisexample [2]isnormally onlypermanently usedbetween 5Wand10W,depending upontheenvironmental temperature. Ahigher powercan,inthiscase,onlybeconsidered foraveryshortperiod(afewseconds). Figure 10.0.8 0.6 0'4t" , ,0.2  I I I 050t00 I50 200 250 Resistance RatioBetween Electrical andMechanical Redundancies. 1000t900 ,0o4_.,,-"j............[mNm] 500JJ," .e.'- 100j_r _ _ _ ol , , , , 0 5 10 15 20 25 [w] Figure 11.Torque-To-Power Characteristics 183
Insomeemergency over-torque scenarios, bothmainandredundant windings aresimultaneously energized inordertoincrease themotor'storquecapability. Forunsaturated motors,thisworkingmode(withtwice thepower)willprovidetwicethetorque.Forallthedifferentwindings' redundancy options,thetorquevalue corresponding tothetotalinputpowercanbedirectlydeduced fromcurve(1)ofFigure11.Acorrective factorbasedonFigure10mustbeintroduced toreflectthelargerpowerrequirement ofthetwomechanically redundant options. Massan(;]Dimensions Intermsofbothmassanddimensions, theimpactofthedifferent redundancy optionsisshowninTable1 considering frameless unitsandamagnetic circuitidentical foralloptions,evenifsplitintwoinsome cases.Itshowsthatthe"mechanically redundant" optionsareheavier(+20%)andlonger(+50%)due againtothelarger"endsofcoils":thelongerthemotor'saxiallength,thesmallertherelativeimpactofthe endsofcoilsonitsmassanddimensions. Thisisindirectly showninFigure12,whichprovides asa functionofthemotor'saxiallengthtworelativevaluesthatreflectthemassandthemotor'saxiallength, respectively. Ineffect,itprovides theevolution ofthefollowing ratiosasafunctionofthemotor'saxial length:(1)themassoftheelectrically redundant motordividedbythemassofthemechanically redundant oneand(2)theaxiallengthoftheelectrically redundant motordividedbytheaxiallengthofthe mechanically redundant one.Theseratiosaregreaterthan95%formotorlengthslargerthan50mmand 250mm(2inand10in).Theconclusion isthattheadvantage intermsofmassoftheelectrically redundant motorbecomes marginal asthemotorlengthincreases. Thisis,however, notthecaseintermsofaxial lengthcomparisons. [-]1.00 0.80 0.60 0.40 0.20 0.00fre(l)mass (2)length I I 0100200300[mm] Figure12.RatiosBetween Mechanical andElectrical Redundancies Redundantand Non-Redundant MotorswiththeSameToraue-to-Power Budget Atthemechanism level,thetorquedemands andpowerbudgetscanbeseenasfixeddesignconstraints. Thus,ifaredundant motormustbeselected, itwillinherently havelargerdimensions thananon-redundant unit.The"non-redundant" design,discussed intheprevious paragraphs, alwaysdemonstrated animproved efficiency thantheredundant options: thus,itsdesignmustbeoptimized inordertoalignitwiththe performance ofredundant units. Table2provides aperformance comparison between twounits:anon-redundant andaredundant (twosectorselectrical redundancy) motor.Bothhavethesamepowerbudgets andareassumed tohavealinear torque-to-current behavior. Thereference caseistheonealsoconsidered inTable1,theredundant unit. Formotorswithlongaxialdimensions, therelativelengthandmassofthenon-redundant unitwouldtend toward50%.Forsaturated units,therelativemassanddimensions ofthenon-redundant designmustbe increased. 184
Table2.Performance Com_arison PARAMETERS Non- Redundant Redundant Two-Sectors Resistance I00 100% Inductance 78 100% Back-emf Constant 100 100% CopperLosses 100 100% Frameless Mass 70 100% TotalAxialLength 83 100% CostComParison Aroughassessment ofthemotor's costevolution ismadeinTable3forbothredundant andnon-redundant units.Sinceitisdifficulttobegeneral onthecostpointofview,thefollowing assumptions aremade:a size23stepper motorisconsidered [2];thehoused motorcostsassume standard space-rated mechanical parts(without anyparticular complications); andbothframeless andhoused unitsareconsidered. Itis important atthisstagetoemphasize theneedtoconsider theoverallredundancy costsatthesub-system level.Infact,itislikelythatthemajorcostdriverwillbeonthedriveelectronics sideandnotonthemotor side. Table3.Relative Costs PARAMETERS Mechanical Redundancy FullIPartial Frameless motor 190 190 Housed motor 290 230Electrical RedundancyNonRedundant 110 100 160 150 Redundant Designs -Available Statistical Data Thestatistics presented herehaveconsidered thetypesofredundancy concepts typically selected for various spaceprograms forthedesigns ofmorethan100spacemechanisms. Thesestatistics takeinto account awiderangeofelectromagnetic motorsincluding brushless DCmotors, hybridandreluctance stepper motors, limitedangletorquers, monoandbi-stable electromagnets, andmoving coilormoving magnet linearmotors. Thedatabase isgivenin[3].Itleadstotheproportions summarized inTable4. Thenumber ofknownapplications considering a"fullmechanical redundancy" isverylimited: eitherthis optionisrarelyconsidered atsub-system levelornon-redundant unitsareprocured withoutinforming the motormanufacturer ofitsintended redundant use(wenevertheless feelthatthisinformation isavailable). Thenumber ofapplications askingforthe"partialredundancy concept" isverylimited. Thereasoncanbea preference togoeithertowardaclearmain/redundant separation (fullmechanical redundancy) ortoward themoreefficient compromise (electrical redundancy), yetneverinbetween. Finally, iftheelectrical redundancy concept isselected, thesharebetween thethree"electric options" isratherbalanced, witha slightpreference forthemorereliable"twosectors" design. Table4.Selected Redundancy Concept Mechanical Redundancy Full Partial 4% 3% 1%Electrical Redundancy Two 2Parallel Shared Sectors Wires Slots 37% 16% 12% 9%NonRedundant 59% 59% 185
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Development ofaMiniature, Two-Axis, Triple-Helmholtz-Driven Gimbal BozSharif, EdJoscelyn*, BrianWilcox" andMichael R.Johnson** Abstract Thispaperdetailsthedevelopment ofaHelmholtz-driven, 2-axisgimbaltoposition afiatmirrorwithin50 microradian (finepositioning) inaspaceenvironment. Thegimbalisintended totravelonadeepspace mission mounted onaminiature "rover"vehicle. Thegimbalwillperform bothpointing andscanning functions. Thegoalfortotalmassofthegimbalwas25grams. Figure 1 Theprimary challenge wastodesignandbuildabearing system thatwouldachieve therequired accuracy inaddition tosupporting therelatively largemassofthemirrorandtheoutergimbal. The mechanism issubjected to100-Gloading without theaidofanyadditional cagingmechanism. Additionally, itwasdesired tohavethesamelevelofaccuracy duringEarth-bound, 1-Gtesting. Duetotheinherent lackofdamping inazero-G, vacuum environment; theabilityofthegimbaltorespond toverysmallamounts ofinputenergyisparamount. Initialtestingofthefirstprototype revealed exceedingly longdamping timesrequired evenwhileexposed tothedamping effectsofairand1-G friction. Itisenvisioned thatfinepositioning ofthegimbalwillbeaccomplished inverysmallstepsto avoidlargedisturbances tothemirror. Various bearing designs, including materials, lubrication options andbearing geometry willbediscussed. Inaddition various options fortheHelmholtz coildesignwillbeexplored withspecific testdatagiven. Ground testinginthepresence of1-Gwascompounded bythelocalmagnetic fieldsduetothe "compass" effectonthegimbal. Thetestdatawillbepresented anddiscussed. Additionally, rationale for estimating gimbalperformance inazero-Genvironment willbepresented anddiscussed. i,Aeroflex Laboratories, Farmingdale, NY NASAJetPropulsion Laboratory, Pasadena, CA Proceedings ofthe34_Aerospace Mechanisms Symposium, Goddard SpaceFlightCenter,May10-12,2000 189
Someofthephysicalandfunctionalrequirements areasfollows: •Aclearapertureof17mmandafieldofregardof+15°inbothElevation andAzimuth witha50 microradian (finepositioning) positioning increment. •Unimpeded, fullrotation inbothelevation andazimuth. •Asurvival temperature rangeof-155 to+145°C. •Anoperational temperature rangeof-80to+70°C. •Amaximum massof25gramswithamaximum totalpowerof0.72wattforsimultaneous 3-axis operation. •Abilitytowithstand 100-Glaunchloading. Introduction a)Size&Weight: Asdepicted inFigure1,thegimbalisarectangular cubewith(8)integrally machined mounting earsarranged (4)toaside.Theprimary dimensions are48x42x32mm.Anelliptical mirror,18x25x2.5mm,actsastheinnergimbalandismounted onjeweled bearings totheouter gimbal, whichisinturnjeweled bearing-mounted tothegimbalouterframe. Onceallowances forthe 17-mmaperture andthe+15°fieldofregardareconsidered, thegimbalstructure islimitedtoa3-mm squareregionalongtheedgesoftheaiiovvable envelope. Totalmassofthegimbalislimitedto25grams. Themagnetic andleadwiremassisapproximately 17grams, leaving 8gramsforthemirrorandgimbalstructures. b)PowerConstraints: Thegimbalislimitedto0.72wattpeakpower. Typical available powerduring normaloperations toanypairofcoilsisapproximately 0.10to0.20watt. c)Positioning Philosophy: Threecoilsets,eachconsisting ofapairofcoilswiredinseries,areplaced orthogonally toeachothertoformarectangular box.Thisconfiguration resultsinamagnetic vector thatisabletofollowacomplete spherical path.Amagnet fixedperpendicular tothecenterofthe inneraxisandcarried bytheinnergimbalfollows themagnetic vectortopointthefiatmirror. In theory,anypointinspaceshouldbeaddressable asthesumof3magnetic vectors generated bythe threecoilsets.Inpractice, effortswereconcentrated inachieving bestfieldlinearity andcontinuity in thefieldofregard. Desigg__C_o____ Physical Form Thegimbalstructure isasinglemachined aluminum alloyspacestructure thatincorporates theframes for thelargestpairofcoilsasWellasthe(8)mounting earslThealloyChosen is6061-T651, athermally stable,iron-free alloy.Theremaining (4)coilsareseparately woundonmachined framesandthen bonded tothemainstructure. Thesepartsaredesigned tointerlock andcreateasubstantially more robuststructure without addingadditional mass.Thestructure andtheseparate coilhousings generally maintain a0.2-mm section thickness. Theultimate strength ofthestructure isobtained whenall components arebonded together. Theentirestructure, priortowinding ofthecoils,weighs4.7grams. BearinaDesign Oneofthekeystothesuccessful realization ofthismechanism wasthefinalconfiguration ofthe bearings. Inviewoftheminiscule levelsoftorqueavailable, thelowestpossible bearing dragtorques wererequired. Itwasestimated thatanaxisdragtorqueof5xE-5N-morlesswasnecessary to achieve therequired accuracy duringEarth-bound testing. Thislevelofdragtorquecanonlybeachieved withjeweled bearings. 190
aremadefrompurecopper. Thedissimilar materials areproperly coatedtonegateelectrolytic effects. Vibration Robustness: Thegimbalstructure issubject toseverevibration duringlaunch. Further, duetothelimitedspaceandmassbudget, nocagingmechanism wasallowable. Themechanism mustbeabletoendure thelaunchcyclewithout anydegradation. Asdemonstrated bysubsequent testing, thespring-loaded bearing designandtheinter-locking structure successfully address this challenge. Bearinas Choice ofJeweled Bearings: In1764,whenJohnHarrison builthisfamous H4marine chronometer, heutilized afullcomplement ofjeweled bearings inatimepiece forthefirsttime.With thereduced friction, theH4chronometer provedaccurate enough tocalculate longitude anywhere in theworld.Upuntilthe1770's, navigation wasaprecarious artatbest.Nautical chartsfortheentire worldcouldnowbeaccurately charted. Eversincethen,Jeweled bearings havebeenthestandard in instrument-grade mechanisms ofeverykind.Thereisawidevarietyofbearing designs invarious materials readilyavailable. Initially, an"olivehole"-type bearing wasselected andaprototype gimbal wasconstructed totestthebearings. The"olivehole"designwasselected totakeadvantage ofits inherent lackofsensitivity toaxialmisalignment andtheinherently lowdragtorqueresulting fromits "pointcontact" geometry. Thegeometry ofthebearing willresultinaminimum ofthreetheoretical contact pointsfortheaxisconsisting ofoneofthetwoendpoints andonesidewall. Thecupportionof thebearing consisting ofatoroidal ringwithanabutting endplateweremadefromsynthetic sapphire whilethepivotwasfabricated inseveral different materials including several alloysofhardened stainless steelandsapphire. Testing oftheprototypes revealed ahigherthandesired dragtorque. Thetestresultsclearlydemonstrated theneedforatwo-point system withthesmallest rotation radius possible. Asecond generation ofbearings wasdeveloped tospecifically address theserequirements ofthemechanism. Thefinalbearing designisamodified v-cupincorporating several novelfeatures. Thev-cupisspring mounted toallowaspecific preload tobeapplied totheassembly. Thespringmounting protects the jeweled bearings inthepresence ofshockandvibration. Additionally, thespringloading fixesthe relationship between thespherical tipofthepivotshaftandthev-jeweled cupthuspromoting consistent performance bymaintaining aconstant radiusofrotation. Usingthisgeometry, the bearings performed atlowerthanestimated dragtorquevalues, helping toimprove thepointing accuracy during1-Gtesting. Figure2depicts asection viewofthebearing cupassembly. Figure3 depicts asectional viewofthemechanism withthebearings inplace. OliveHoleBearinq Figure 2V-Jewe! Bearlnq 192
Figure 3 Materials: Asdiscussed earlier, allbearing components werefabricated fromnon-magnetic materials. Considerable effortsweremadetoobtainiron-free variants ofthemany"common" materials employed intheconstruction ofthegimbal. Lubrication: Nolubricants areemployed. Duetothesemi-cryogenic operational temperatures, no wetlubricants weresuitable. Theuseofjeweled bearings precluded theneedforanyadditional lubrication. Thecombination ofthematerials employed inthebearing resultsinacoefficient of frictionof0.15. Vibration: Thespringwithinthebearing isapotential singlepointfailuresothatattention mustbe concentrated onthisimportant aspectofthedesign. Areliability prediction wasperformed toverifya verylowfailurerateintheapplication ofthespring. Thespringuses0.2-mm diameter wirewithameancoildiameter of1.32mmdiameter. Thereare6 activecoilswithapitchof0.33mm.Thematerial isBeryllium-copper. Thespringrateforacompression springis: R=(modulus ofrigidity)(wire diameter_ 8(meanspringdiameter)3(Active coils) R=4.24Ibs./in Thespringconcentration factoriswherer=coildiameter towirediameter 193
Kw=[(4r-1)/(4r- 4)]+0.615/r Thefailurerateforspringsis: _L=[functionof(stress/strength) 3] Stress=8(R')(comDression)('sDrina diameter_ Kw  (wirediameter) 3 Strength forBeCu=190psi ;_=(3470psi/190E3 psi)3=6E-6failures/million hours Thesprings arefreefloating inacylindrical channel sothatnoextraordinary sideloadsorstresses other thantheapplied compression canbeapplied. Thesprings areconsidered tohaveaverygooddesign marginforpreventing failureinthisapplication. Helmholtz (;oil Fieldintensity: Thefieldsaresmall,approximately 40gaussincloseproximity tothecoilsranging toapproximately 2.5gaussinthecenterforaninputpowerinthe100to200milliwatt range. By contrast theEarth's magnetic fieldisintheorderof0.50gauss(0.57gaussatplantlocation). Torque isproduced byinteraction withthefieldofasmallcylindrical magnet (3.0mmdiaby6.3mmlong) affixedtothebackoftheactuator mirror. Themagnet islocated atthegeometric centeroftheinner gimbalandcanonlyinteract withtheweaker fieldsatthecenter. Byvarying thecurrents inthethree coils,themagnet canbemadetoalignwiththevectorsumofthesethreefields.Figure4showsthe FEAmatrixforapairofcoilsandthecentermagnet. Thesurrounding airiseliminated sothe components canbeseen.Figure5showsasideviewofonepairofcoilswiththeuniformity ofthe fieldillustrated bythemonocolorinthecenter. Figure6isatypicalplotofthefluxdensity through thenormaltoandthrough apairofcoils. Torque Values: Theprecision andfrictionfreerequirements forthebearings canbeseenby analyzing thetorque's generated bytheseweakfields.Thepeaktorques areintheorderof3.5xE-3 N-m.Theunit,whenproperly balanced, actsasacompass andtheseforcesmustbeaccounted for whentestingtheactuator. Prototype performance Precluding theuseofNASA's "Zero-G" aircraft, itwasnotpossible totestthegimbalbearing performance asitwillbeultimately used.Gravity hasamajorinfluence onthebearing dragtorque(due tofriction) andthussomemeasures mustbetakentoreducethenegative effectsofthisforce. Itwasfoundthataxis"stiction", thenon-linear dragtorqueeffectattributed togravity, wasfarlesssevere whentheaxisofrotation wasperpendicular togravity. Further investigation revealed thattheeffectwas duetotheabilityofthegimbaltorollalongtheinnerconicalsurfaces ofthev-jewel. Therollingeffectof thebearing enabled byalevelaxisofrotation gavemuchbetterresultsthanwhentheaxisskidded atthe centerofthebearings whentheaxisofrotation isparallel withgravity. Although thedifference between thesetwomodeswassignificant incomparison, thegimbaleasilymetpointing accuracy criteriaineither orientation. Repeatability: Themirror's positioning repeatability needed quantification. Thefirsttestinvestigated thecombined effectofmirrorbearing frictionandfieldgeneration repeatability. Themirrorwasthen allowed tostabilize ataposition intheareaofregard. Noaircurrents orvibrations ofanykindare allowed. Thetestbenchisisolated fromfloorvibrations orstrayaircurrents suchastheair 194
conditioner orfilterairstreams. Thedrivecurrents ofthethreeaxesarenoted.Themirroristhen electrically drivensothatalaserbeamreflected toacalibrated targetmovesupwardandhasasnear averticaltravelaspossible. Themirroristhenelectrically reversed andbroughtbelowtheinitial position. Themirrorisagainelectrically reversed andthebeamisreturned totheoriginaltargetspot. Thecurrents arethenrecorded. Knowing thegimbal's sensitivity, milliradians permilliamp, the deviations (shouldthecurrents notbeexactlyastheywerewhenthebeamexcursion began)can thenbecalculated. Figure4 195
Shaded Figure 5 Typical resultsfromasetoftentrialsareshowninTable1 Table1  AxisCurrent 1 51.2ma 2 51.3 3 51.2 4 51.3 5 51.3 6 51.2 7 51.2 8 51.2 9 51.2 10 51.1 Givenasensitivity of4.5milliradians permilliamp, themaximum offsetfromtheoriginal spotis approximately 0.56milliradian. Accuracy: Another testinvestigating thebearing frictionalonewasalsoperformed. Withthesystem setasaboveandthecurrents leftunchanged, themirrorwasgentlymovedfromequilibrium usinga gentleaircurrent fromapipette. Themirrorwasallowed toswinguntilitcametorest.Thedeviation ofareflecting laserbeamonatargetcalibrated atadistance wasrecorded. I96
Table2.Accuracy trials  .Recorded Anales 1 0milliradian 2 -0.5 3 -2.5 4 -1.0 5 +0.5 6 -1.0 7 -0.5 8 -1.0 9 +0.5 10 0 Theaverage deviation being0.55milliradian with1.95milliradians asthegreatest fromcenter. Micro-Joule Positioning: Athirdcriterion forthegimbalisitsabilitytomoveinsmall"jog" increments. Theminimum amount ofenergynecessary toelicita0.1-milliradian motionwas measured as45microjoules. Thisamount ofenergyisequivalent tolighting a10Wflashlight for4.5 millionths ofasecond. Vibration: Ofgreatconcern wastheabilityofthebearings towithstand thevibration specification (27.7g'sRMSrandom). Thebearings showed nodegradation inperformance afterexposure tothe vibration environment. Forexample, thefirsttestsequence abovewasrepeated aftervibration witha maximum deviation of0.55milliradian. Lessons Learned Jeweled Bearina Performance Whentestingajeweled bearing instrument intended formicro-gravity operation inagravityfield,itisbest totestwiththerotation axisperpendicular tothegravitational field. Maanetic Behavior ofNon-maanetic Materials Whendealing withextremely finemagnetic fieldsandeffects, itisbesttotestallassociated materials and components foranylatentmicro-magnetism thatmayaffecttheaccuracy oftheinstrument. 198
CoverDriveandLockRingMechanisms forGenesis LouiseJandura" Abstract TheGenesis payload canister willreturnsolarwindsamples toEarth.Thecanister contains four mechanism assemblies: theCoverDriveMechanism, theLockRingMechanism, theArrayDeployment Mechanism, andtheArrayLatchMechanism. TheCoverDriveandLockRingMechanisms aredescribed indetailwhiletheothertwomechanisms arebrieflysummarized. TheEngineering Modelcanister has beendesigned, built,tested,anddelivered tothespacecraft. TheFlightModeliscurrently beingbuiltwith delivery tothespacecraft scheduled formidJuly2000.Launch isscheduled forJanuary 2001. Introduction TheGenesis mission willplaceaspacecraft outside theEarth's magnetosphere andexpose ultra-pure materials tothesolarwindforabout23months. Figures 1and2showthestowed payload canister integrated withtheSample ReturnCapsule (SRC)andthespacecraft. TheElectron Monitor andtheIon Monitor aresensorassemblies thatprovide dataabouttheelectrons, protons, andalphaparticles inthe solarwindasafunction oftime.Thesedataareinputtothescience algorithm, whichcontrols the specifics ofthesolarwindcollection. Theembedded solarwindsamples willbereturned totheEarth withinthepayload canister, safelycontained withintheSRCforreentry. TheSRCwillberetrieved by mid-airrecovery. Thecanister isrichwithmechanisms, containing fourdistinct assemblies: theCoverDriveMechanism, theLockRingMechanism, theArrayDeployment Mechanism (ADM), andtheArrayLatchMechanism. Twokeycomponents, theCoverDriveandLockRingMechanisms arethefocusofthispaper. Thesetwo mechanisms provide straightforward functions: alaunchlatchandthemeanstoopenandclosethe canister cover,buttheirrequirements anddesignarelinkedtogether creating amuchmorechallenging problem. Figures 3and4showtheintegrated canister inboththeclosedandopenconfigurations. TheCover DriveMechanism andLockRingDriveMechanism arevisibleonopposite endsofthecanister. TheLock RingAssembly islocated aroundtheperimeter ofthecanister between thecoverandbaseflanges. Solarwindiscaptured withboththeConcentrator andthehexagonal collectors thatfillthearrays. The ADM(notvisibleinthefigures) isastepper motordrivewithseparate motorsusedtoposition eachofthe fourdeployable arraysinthebase.TheArrayLatchMechanism secures thestowed arraysforlaunch andreentry. LockRingMechanism Requirements TheLockRingMechanism consists oftheLockRingAssembly andtheLockRingDriveMechanism. AlongwiththeCanister Seal,thismechanism's purpose inthecanister assembly is:toprovide alaunch latchforthecanister covertosustain launch, reentry, andrecovery loads;toprevent contamination ofthe canister interior; andtoproduce apush-off forcetoseparate thesealinterface. Anadditional requirement isthatthemechanism mustbecapable ofperforming afunctional testtoverifytheflightelectrical interfaces andactuator operation without opening thecanister toavoidcontamination oftheinteriorofthe flightunit. "JetPropulsion Laboratory, California Institute ofTechnology, Pasadena, CA Proceedings ofthe34_Aerospace Mechanisms Symposium, Goddard SpaceFlightCenter,May10-12,2000 199