ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Recommendations forFutureDevelopment Asdiscussed, themethods usedforheating themechanisms coulduseimprovement. Avendorhasbeen foundtomakeaheaterthatwouldfitontotheMicroSep-Nut andshould easilybeabletodevelop a heaterfortheMiniSep-Nut. Forfutureheaters, thesmallest possible gaugeleadwire(30or32AWG) shouldbeusedforbothmechanisms. Also,themanufacturer shouldpresetthebendsizetomatchthe bodydiameter, byhotforming theheateraround amandrel. Bettercharacterization oftheSMAsprings isneeded. Thefocusoftheprogram andmosteffort(bothtime andbudget) wasspentondesign, assembly, andoverallcharacterization. Thespringvendor wasrelied ontomeetthedesign criteria specified. SincetheSMAsprings weremadeonabesteffortbasis,the vendorperformed noverification. MiniRotary Actuator DesignApproach Aminirotaryactuator wasdesigned anddeveloped byStarsys Research thatprovides .014-.042 N-mof torqueintwodirections overa120°rotational range.Therotaryactuator couldbeusedtoopenandclose aninstrument coverthatweighs about1/2gram.Itincorporates adetentlatchthatwouldbecapable of maintaining thecoverineithertheopenorcoverclosedposition without theuseofpower. Theholding torqueforeitherofthetwopositions wastobeequaltoorslightly greater thantheoutputtorqueofthe rotaryactuator. Mostofthedesignoptions considered fortheactuator required linearmotionbechanged torotarymotion toobtaintherequired output.Threechoices wereexamined fortheactuator tooperate themechanism; a smallparaffin actuator, SMAwire,andSMAsprings. Aftersomeconceptual designworkonthedifferent actuators, theSMAspringwaschosen asthemostfavorable approach. Thiswasduetothehighstroke thatcouldbeachieved, thefairlyquickresponse time,andthevarietyofavailable sizesandoutputs. TwotypesofSMAspringshapes wereevaluated inthefinalmechanism design. First,wavesprings were formed fromSMAstripstoprovide agoodrangeofmotion (Figure 5).Usingopposing springs, the mechanism coulddrivearackandpiniongeararrangement toconvert linearmotiontorotation. This designwasdeemed toolargeforthescaleofmechanisms beingdeveloped andtheprototype wasnot built. IIIWaveSpringCompressed WaveSpringAfterHeating Figure5.SMASpring Designs Thefinalspringdesignchosen fortherotaryactuator wasatorsionspringformed fromSMAwire(Figure 5).Wheninstalled, thetorsion springiswoundpastitsnominal position around amandrel. Asheatis applied, thespringreturns toitsnominal position, providing theoutputtorque. Anoppositely woundspring onthemandrel provides anopposite torquesothemechanism canbeoperated inbothdirections. The mechanism assembly isshowninFigure6. Foroperation, onepowerleadisapplied tothedrivedisk(providing asinglecommon foreithertorsion spring). Theotherleadisattached tooneoftheexposed endsofthetorsion springs (depending onthe direction ofdesired output). Thedrivediskiskeyedtotheoutputshafttotransfer therotation fromthe torsionsprings. Theoutputshaftalsocontains astopthatinterfaces withoneofthecovers. Thisstop limitstherotation oftheoutputshaftineitherdirection. 291
TorsonSprng:u eFigure 6.MiniRotary Actuator Characterization Testinq Because ofthesmallsizeofthemechanism, itwasdifficult tomeasure someoftheperformance characteristics. Wewereunabletoobtainanaccurate measurement oftheinternal friction. Also,testing waslimitedsincemostoftheeffortwasfocused ondeveloping thevarious designs anddeveloping the torsionspringdesign intoafunctional prototype. Nothermal testingorlifecycling wasperformed onthe mechanism. Operational testingshowed themechanism tobesensitive topower-on time.Ifaconstant current wasapplied totheSMAspring,therewasariskofdamaging theSMAspringbyheating ittoa temperature wherethespringmaterial isre-annealed. Thebestfiringsequence forthismechanism would beseveral short(1-second maximum) pulsesuntiltelemetry signals thecoveristotheopenorclosed position. Torque measurements weremadewithacalibrated torque gaugeattached totheoutputshaftofthe mechanism. Asthemechanism waspowered, theoutputtorqueof0.042N-mwasmeasured. Thisturned outtonotbeaveryaccurate measurement. Thetorque outputofjustthetorsion springs themselves wouldhavebeenmoreuseful.However, nofixturing wasdeveloped totestthesprings accurately. Problems Encountered Themostdifficult requirement ofthedesignwasthatitwasnecessary forthemechanism tooperate in bothdirections. Thismeantthemechanism hadtobecapable ofopening andclosingthecover.Asimple unidirectional drivemechanism wouldhavebeenmuchsimpler, yetnotnearlyasuseful. Themain problem thatthedualmotionpresented isthattheoutputspringisalwaysworking toresettheopposite direction spring. Thisgreatly reduces theavailable outputtorque, sinceapproximately halftheoutput torqueisrequired toresettheotherspring. Another problem encountered duringthedesignwashowtoincorporate adetent(required tomaintain the rotarylatchineitheroftheendpositions). Theinitialapproach usedwiththetorsionspringdesignwasa leafspringofmetalthatcontacted aflatonthedrivediskineithertheopenorclosedposition. Theleaf springalsoprovided thecommon contact pointfortheelectrical circuit,sinceoneendofbothtorsion springs wasincontact withthedrivediskatalltimes.Thisapproach resulted intoomuchdragonthe drivedisk,decreasing theamount ofoutputtorqueavailable. Theleafspringalsoprovided littleactual holding torqueforthemechanism ineitheroftheendpositions. Recommendations forFutureDevelopment Theultimate success ofthisdesignwillrelyonfurtherrefinement oftheSMAtorsionspring.Thetorqueof thespringisconsiderably lessthanneeded forthedesired outputtorqueofthemechanism. Increasing thewirediameter willeventually resultinanincreased outputtorque, butitwillatsomepointleadtoa largeroverallmechanism. 292
Thedetentapproachinitiallyusedinthedesignneedsimprovement. Anotherapproachtoconsideristo useanotherSMAdevicetolatchandunlatchthemechanism ineitherendposition.Ideallythiswouldbe connectedinserieswiththetorsionspringsothatwhenpowerisapplied, itbothreleases thelatching deviceandoperates thetorsionspring. However, thepractical implementation ofthiscouldbedifficult. It maybenecessary toaddasecond circuittooperate thelatching component ifaSMAdeviceisused. Thistoocouldaddcomplexity inbeingabletoproperly timetheevents. Crimpcontacts needtobeaddedtotheendsoftheSMAsprings forelectrical connection. Theprototype wasconnected manually andthiswasnotpractical foractualflightuse.ItwasfoundtheSMAwiredoes noteasilyacceptsolder. Forthecommon contact thedrivedisk,itneedsamethod toreduce dragfrom thewirecontact. Onesolution maybetoaddametalshaftthrough theoutputshafttocontact thedrive diskandthencrimporsolderacontact ontotheendofthis.Theendwouldthenbeallowed torotate freelyasthemechanism rotates. Miniature BurnWireRelease Thistinyrelease mechanism wasdeveloped atAPLforaminiature instrument coverorsimilardevice needing anextremely compact, lowmass,andlowpoweractuation device• Itusesaburnwiretodirectly carrythetensileloadofacoverorscrewthatisattached toitsretainer. Current applied tothewirewill breakorfusethewireatthelocation oftheretainer tocauserelease ofthehardware attached toit.This isuniquefromothertypesofsatellite burnwirereleases. Thismechanism usesthewiretodirectly carry thetensileload;therefore itisahighlysimplified designthatcanbegreatlyminiaturized. Itisalsoaneasy designtoscaleupordownaccording totherequirements ofthedeviceitisattached to. AluminumHousng i/.,_- __ Wtthmounting ears---.-._._ _I/ i Aluminum Retainer_------_ ! Kick-off ' _Sprmg_ }_:" BeCuBurnWir_._.._ i_:"l G-lOWireAttach Jiil "Button"-_ f_HousingRetainer Assembly BumWire Figure7.MiniBurnWireRelease Assembly Desi,qnApproach Itwasdetermined earlyinthedesign process thattohighlyminiaturize thismechanism, ithadtocontain thefewestpartspossible. Theburnwirerelease mechanism (shown inFigure7)hasonly5components withonlyoneofthosethatarereleased withthecover.Thesecomponents arealsomultifunctional. The burnwireisusedtoholdthemechanism together, carrytherestraint load,makeelectrical connection, andinitiatetherelease action. Wiresizewasbasedonrestraining a100-gram cover.Therestofthe mechanism wasdesigned topackage ascompactly aspossible andprovide threadforasmallscrew.A kick-off compression springwasincorporated toovercome frictionorothersmallforcesthatmighthangupthemechanism. Beryllium copper waschosen forthewirematerial basedonitsexcellent mechanical properties aswellasitshighresistivity. Purecopper wireofthesamediameter takesamuchhigher currenttoburn.Stainless steelwirehassimilarproperties asBeCuandcouldworkaswell. 293
design,couldalsobemadefromTorlonorotherthermoplastic. Thiswouldprovidealowfrictionsleeveto holdtheretainer. Thehousingcanberedesigned tomakethismechanism aplug-initemtomaketestingeasier.All assemblies werehandinstalledintothetesthousingsandeachelectricleadconnected manually.A packagesimilartoabusfusecouldbedesignedtoeasehandlingandinstallation ofthemechanism. Handlingofminiaturescrewsshouldbeavoidedbecauseofhowfragiletheyareandhoweasyitisto loosethemwithinaninstrument, whichwasdemonstrated timeandagainthroughout testing. Furtherminiaturization ispossiblewiththismechanism. Inordertohandmachineandhandassemblethe prototype,standardfitandtoleranceswereused.Alternativefabricationprocessshouldbeconsidered to takethemassandvolumeanothersteptowardsbeinga"micro"sizedmechanism. Theprototypeburn wiremechanism hasbeenshowntohaveexcellentreliabilityandthepossibilityforfurtherminiaturization. Itissimpleindesignandtheburnwiretestshaveshownveryconsistentresults.Itcurrentlymeetsthe criteriaforminiatureinstrumentcovers,buthaspossibilityforuseinnumerousapplications onamicrosatelliteprogram.Theminiburnwirereleasemaydevelopintoakeymechanism devicefortheAPL MicroSatprogram. MiniLinearActuator Linearactuators areprevalent insatellite programs astriggers orswitches formechanical devices. There isadefinite needforaminiaturized version ofthistypeofmechanism forfuturemicrosatellites. Thismini linearactuator, developed atAPL,isdesigned toprovide aquickacting,lowshocklinearmotion. This mechanism hasprogressed indevelopment fromfirstprototype intoamoreoptimized prototype. The second prototype wasdesigned andconstructed afterasmallsetofcursory testswasconducted onthe initialprototype. Fromthelessons learned, alargedecrease insizeandmasswasobtained without performance loss. Figure9.MiniLinearActuatorTravelPin.__._ SMAWire.._ _i o.o,6mmII Isolation / DesiqnApproach Themotion (orstrain)oftypicalSMAmaterials islimitedto8%oftheamount ofmaterial. Anominal designforthismechanism wouldlimitstrainto2%toensure adequate fatigue margin. Therefore, this restriction, aswellastheamount ofwirecontained withinthemechanism itself,limitsthestrokethis mechanism willbeabletoproduce. Forexample, awirelengthof20mm(0.8inch),thestrokewouldbe 0.4mm(0.014inch).Inthisdesign, Nickel-Titanium wireisheated byrunning current through thewire. Thecurrent heatsthewiredirectly viaresistance inthewire.Response timeisveryquick,(-1/10sec), andthedeviceisnottoosensitive toitsexternal thermal environment (inair).Through astrainrecovery 296
processinthematerial,thewirecontractswhenheatedandreturnswhencooledusingthecompression biasspring.Itisaself-latching devicethatisfullytestable.Theassembled conceptisshowninFigure9. Bothprototypemechanisms utilizeSMAwireforactuatingthismechanism. Itworksasahighforce,low shockpinpullerthatcantriggeranumberoflatchdevicesoninstruments shuttersorcovers.Themini linearactuatorisself-resettable usingabiasreturnspring(Figure9)andcanoperatein-flightfor numerousactuationswithoutanyexternalassistance orresets.Withdesignimprovements, thesecond unithadan85%reductioninmassandvolumeandimprovedtheperformance ofthepinactuation. Characterization Testin.q Operational testwereperformed onbothunitsusingasimpleelectrical circuitdirectly connected tothe SMAwire.Thiselectrical circuitwasabletorepetitively cyclethemechanism through itsentirerangeof motion through theuseofacapacitor. Thecircuitdelivered 0.25Aat8.5Vwiththecapacitor charging anddischarging everytwotothreeseconds. Motionofthetravelpincreated bythecontracting SMAwire wasmeasured through theuseofaLinearVoltage Displacement Transducer (LVDT) indirectcontact withthetravelpinofthemechanism• Whenthetravelpinisdisplaced bytheSMAcontractions, this causes theLVDTtodisplace andrecord themotion. Pindisplacement forthefirsttestunitwas approximately 0.30-0.33 mm,whichisalsopredicted through calculation. Thesecond testunit incorporated alongerSMAwire(inasmaller package design) andincreased displacement to0.53mm. Figure 10showstheresultsfromthesecond mechanism tests.Notetheconsistent andrepeatable motiondisplayed bythemechanism. Linear MOtlQFI 0O25 002 0015 001 0005 -0005--Linear Motion 1 20 25 30 2.5 40 45 50 55 6£ _me(I} Figure 10.MiniLinear Actuator Operational TestsResults (Second testunit) Lifetime testingwasconducted onthesecond unitfollowing thecharacterization testingusingthesame setupandequipment. Thistestrevealed thatthemechanism performed nominally forover1000cycles followed byagradual decayofperformance untilfailureat12,000 cycles(after10hoursofoperation). Thiswasperformed in-airunderambient conditions andistobefollowed bythermal-vacuum testingthat isyettobeconducted. 297
Recommendations forFutureDevelopment Oneofthebestfeatures ofthisdeviceisitscapability tobeeasilyadapted forheavier orlongerwirein ordertoprovide additional performance capability. Largerdisplacements ofthetravelpincanbeachieved byaddinglengthtothewireandmechanism. Largerpinretraction forceandelectrical redundancy canbe achieved through theuseofseveral SMAwiresinstead ofasinglewireasinthisdesign. Wiregauge, length,andarrangement oftheSMAelement thatdrivesthismechanism areareasoffurtherinterest for characterization tests. Overall, thismechanism isanextremely light,small,andreliable mechanism thatcanbeusedinmany applications thatrequire theuseofasimplemechanical linearactuator. Testing ofthemechanism first validated theconcept andthendemonstrated theimproved performance acquired byafewmodifications inthedesign. Through theuseofSMAtechnology, thismechanism hasgreatpotential thatwillenableit tobeavaluable component oftheMicro-Mechanism toolkit. MiniRedundant Release Mechanism Thisminiature release isdesigned toprovide electrical andmechanical redundancy. Mostmechanisms striveforredundancy intheelectrical connections buthavesinglepointsoffailureinthemechanical operation. Thismechanism provides multiple redundancies withitsabilitytooperate (release aplunger) withtwoofthethreeSMAelements operating. Theminiredundant release isinaveryearlystageof development, andonetestunithasbeenbuilt.Characterization andtesting ofthemechanism isjust gettingstarted andshowsalotofpromise. Desi.qnApproach Thisprototype mechanism contains shaped SMAstripsthatlockarestraint shaftforaninstrument cover, solararray,orothersystem needing arelease device. SMAstripsgriptheendoftheshaftwhileinacold state.Whenpowered andbrought toahighertemperature, theSMAstripschange shapeto"openthe lock".Figure11showsanexploded assembly viewofthemechanism. Fullmechanical redundancy is achieved because thedevice stilloperates ifoneofthestripsfailstoopen.Aresistor heateronthe housing provides thetemperature control. Thisdesign canbeconverted todirectcurrent heating to increase theresponse time.Directcurrent heating willalsoprovide furtherelectrical redundancy. Simple construction lendstominiaturization. Thismechanism canbeminiaturized muchfurtherdepending onthe holding forceneeded. Theassembled concept isshowninFigure11. Release Plun( Housing I Isolation B,tton i Figure11.MiniRedundant Release Device Recommendations forFutureDevelopment Initialfabrication andtesting ontheprototype mechanism showed theneedforproper tooling to manufacture andshapetheSMAmaterial inaconsistent manner. Thefirstprototype usedhandshaped 298
Conclusions Thekeyfactorforshrinking mechanism sizeistoreduce complexity. Theminiseparation nutdesignwas takenfromaconventional separation system andwassimplyscaleddown.Itwasjudged tobenotquite miniaturized forthemicrosatellite usesthatwasenvisioned. Byradically redesigning theminiseparation nut,themicroseparation nutwasabletogettheperformance needed with3components instead of8 andwas75%lighterandsmaller andlighterthantheminiseparation nut.Another example istheburn wiremechanism, whichisthesmallest andlightest inthetoolkitdueitssimplified andstreamlined design. Itsthiskindofstreamlining thatisneeded toaddress themicrosatellite needs. Someofthesemechanisms giveupredundancy forsimplicity. Thismaybeariskthatconstellations of smallandinexpensive microsatellite constellations willbewillingtotake.Ifredundancy isrequired, there areoptions inthistoolkitthatprovide it.Micromechanisms aregoingtoneedtobreakfromtraditional mechanism designtomeettheneedoffuturemicrosatellites. Theproblems encountered inthisprojectwerenotcompletely addressed andfullytested. Continuation of thisprojectisexpected tolookinmoredetailatmanufacturability, assembly, characterization ofSMA's and,andpowerandmassoptimization forthesemechanisms. Fromthebrieftesting performed, there appears tobeattainable solutions toalltheproblems encountered. Futureworkshouldyieldmechanisms thatarequalified forflight.Thesewillbesomeofthesmallest andlightest mechanical components available thatprovide precise andconsistent performance formicrosatellite aswellastraditional satellite programs. References Helvajian, Henry."Microengineering Aerospace Systems." TheAerospace Press,American Institute of Aeronautics andAstronautics, 1999. Madou, Mark."Fundamentals ofMicrofabrication." CRCPress,1997 Waram, Tom."Actuator DesignUsingShapeMemory Alloys." Second Edition, 1993 300
Form Approved REPORT DOCUMENTATION PAGE ouBNo.o7o4-o188 Publicreporting burden forthiscollection ofinformation isestimated toaverage Ihourperresponse, including thetimeforreviewing instructions, searching existing datasources, gathering andmaintaining thedataneeded, andcompleting andreviewing thecollectton ofinformation. Sandcomments regarding thisburden estimate oranyotheraspectofthis coltection ofinformation, including suggestions forreducing thisburden, toWashington Headquarters Services. Oireclorate forinformation Operations andReports. 1215Jefferson DavisHighway, Suite1204,Arlington, VA22202-4302, andtotheOfficeofManagement andBudget, Paperwork Reduction Project (0704-0188), Washington, DC20503 1.AGENCY USEONLY (Leave blank) 2.REPORT DATE 3.REPORT TYPE ANDDATES COVERED May2001 Conference PublicationiI 4.TITLE ANDSUBTITLE 5.FUNDING NUMBERS Proceedings ofthe35thAerospace Mechanisms Symposium 6.AUTHOR(S) Edward A.Boesiger, Compiler PERFORMING ORGANIZATION NAME(S) ANDADDRESS(ES) AmesResearch Center Moffett Field,CA94035-1000 9.SPONSORING/MONITORING AGENCY NAME(S) ANDADDRESS(ES) National Aeronautics andSpaceAdministration Washington, DC20546-0001712-30 8.PERFORMING ORGANIZATION REPORT NUMBER A-00V0037 10.SPONSORINGIMONITORING AGENCY REPORT NUMBER NASA/CP-2001-209626 i 11.SUPPLEMENTARY NOTES Sponsor: Mechanisms Education Association PointofContact: Ronald E.Mancini, Deputy Chief,Systems Engineering Division, AmesResearch Center, MS213-1, Moffett Field,CA94035-1000 12a.DISTRIBUTION/AVAILABILITY STATEMENT 12b.DISTRIBUTION CODE Unclassified --Unlimited Subject Category 15 Distribution: Standard Availability: NASACASI(301)621-0390 13.ABSTRACT (Maximum 200words) Theproceedings ofthe35thAerospace Mechanisms Symposium arereported. AmesResearch Center hostedtheconference, whichwasheldattheFourPointsSheraton, Sunnyvale, California, onMay9-11, 2001.Thesymposium wassponsored bytheMechanisms Education Association. Technology areascovered included bearings andtribology; pointing, solararray,anddeployment mechanisms; andothermechanisms forspacecraft andlargespacestructures. 14.SUBJECTTERMS Spacecraft components, solararraydeployment, bearings, tribology, covers, latches, dampers, retraction mechanisms. 17.SECURITY CLASSIFICATION 18.SECURITY CLASSIFICATION OFREPORT OFTHISPAGE Unclassified Unclassified NSN7540-01-280-550019.SECURITY CLASSIFICATION OFABSTRACT15.NUMBER OFPAGES 312 16.PRICE CODE A14 20.LIMITATION OFABSTRACT Standard Form 298trey. 2-B9) Prescr)bed byANSJ StdZ39.1 e 298-102
i NASA/ CP—2016– 219090     

43rd Aerospace Mechanisms Symposium   

Compiled/Edited by: Edward A. Boesiger  

Proceedings of a symposium held at   Biltmore Hotel, Santa Clara, CA   Hosted by the NASA Ames Research Center and   Lockheed Martin Space Systems Company   Sponsored and Organized by the Mechanisms Education Association 

May 4 -6, 2016     

May 2016
iii PREFACE  

The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the  reporting of problems and solutions associated with the development and flight  certification o f new mechanisms. Sponsored and organized by the Mechanisms  Education Association, responsibility for hosting the AMS is shared by the National  Aeronautics and Space Administration and Lockheed Martin Space Systems Company  (LMSSC). Now in its 4 3 rd symposiu m, the AMS continues to be well attended, attracting  participants from both the U.S. and abroad.    The 43 rd AMS  was held in Santa Clara, California on May 4, 5 and 6, 201 6. During  these three days, 4 2 papers were presented. Topics included payload  and positioning  mechanisms, components such as hinges and motors, CubeSats , tribology , and  mechanism  testing . Hardware displays during the supplier exhibit gave attendees an  opportunity to meet with developers of current and future mechanism components.    The high quality of this symposium is a result of the work of many people, and their efforts are gratefully acknowledged. This extends to the voluntary members of the symposium organizing committee representing the eight NASA field centers, LMSSC, and the European Space Agency. Appreciation is also extended to the session chairs,  the authors, and particularly the personnel at AR C responsible for the symposium  arrangements and the publication of these proceedings. A sincere thank you also goes to the sympos ium executive committee who is responsible for the year -to-year  management of the AMS, including paper processing and preparation of the program.     The use of trade names of manufacturers in this publication does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by  the National Aeronautics and Space Administration.