ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Table3.Scanner Crosssection PartsandMaterials forOriginal andHigherStrength Designs Item 1Title Housing, Scanning Motor ShaftScanMotor OuterBearing RaceOldMaterial Beryllium HP-20S-200 Inconel X-750NewMaterial Beryllium HP-20S-200 Inconel X-750 440CSteel 440CSteel 4InnerBearing Race !440CSteel 440CSteel 5OuterBearing Spacer 416Steel 416Steel 6InnerBearing Spacer 416Steel 416Steel 7Washer, InnerBearing 304CRES A286Steel 8Retainer-Spring 304CRES Custom 455H1000 9Retainer -Outer 6061-T6 Aluminum 7075-T7351 Aluminum 10Nut,Bearing Retainer 304CRES A286Steel 11Screws-Spring Retainer 304CRES A286Steel 12 304CRES Screws-Outer Retainer A286Steel Afterthehigherstrength partshadbeenmanufactured andinstalled intothescanner thescanner was retested. Thematerial changes madethescanner muchmorerobustwithrespect tovibration. Therewas verylittlechange innatural frequency asaresultofvibration. However, whentestedovertemperature, thejitterperformance wasfoundtovarygreatly andinfactthescanner failedtomeetthespecification requirements atatemperature extreme. Further analysis wasperformed and2rootcauses werediscovered: 1.Tolerance stack-up andsubtleassembly madetheactualpreload onthebearing veryinconsistent on anassembly toassembly basis.Theactualpreload couldvarybeyond limitsspecified onthedrawing asaresultofthesevariations. 2.Thecoefficient ofthermal expansion (CTE)mismatches resulted inavariation inbearing preload as thetemperature changed. Thepretoad variations resulted invariations inbearing running torqueandmoresignificantly bearing torquehashovertemperature. AscanbeseenfromFigure3,variations intorquewillcausetheslipangle andhencetherotational periodtovary.Thisvariation resulted invelocity jitterwhich, inthiscase, exceeded specification limits. Theanalysis indicated that,forabulktemperature change ofaslittleas10degrees C,ifthebearing isat thelowendofthepreload tolerance, thetemperature change canresultinzeropreload. Design Solution Atypicaldesign solution forahighprecision bearing mountsuchasthiswouldbetoaddanelement flexible element suchasawavewasher. Thewavewasher orsimilarelement wouldbemuchmore flexible thanthebearing spacers orrotorshaft.Thepurpose ofthiswouldbetoallowforexpansion and contraction duetobulktemperature changes whilemaintaining aconstant preload onthebearing. However, inthiscasetheinstallation ofanelement suchasawavewasher wasnotanoption.Themotor andbearings hadalready beenpurchased. Theavailable axialspacewasnotadequate forthe installation ofthistypeofelement. Oneoftheotherproblems withtheuseofawavewasher ordiskwasher istheirrelatively lowload capacity. During vibration, theAVHRR scanner bearing experiences loadsapproaching 1000pounds. Thisiswellbeyond theloadcapacity ofexisting waveanddiskwashers, giventhesmallamount ofaxial spaceavailable. Figure6illustrates atypicalbearing installation utilizing awavewasher. 40
Existin ArtFREE THICKNESS HEIGH1 L--------OEA"ING 0.0.LOAO 'tWORK HEIGHT Figure6.Typical Bearing Installation utilizing aWaveWasher AsshowninFigure6,theduplexballbearing mountdeviceclamps thebearing axially.(Axially clamped isdefined asapplying aforcealongtheaxisofrotation totheracesofthebearing). Asthebearing is clamped thecomponents oftheretaining system willdeflect. Asthebearing isclamped, theaxialspringwilldeflect, applying aloadtotheracethatisproportional to thedeflection. Thus,variations inthedeflection ofthespringwillresultinvariations intheloadonthe bearing. Thus,increased torqueresultsinanincreased load. Discsprings, wavesprings andfingerdiscsprings fromanother manufacturer arealsoused,butthe existing springconcepts designhaveavariation ofloadontheorderof+25%.Thisisnotacceptable for highprecision mechanisms, whichrequirestableperformance, especially overalongperiodoftimeunder severeenvironment condition, asrequired ofspaceflightmechanisms. Jfthesespringswereeliminated fromthedesigninFigure6itwouldbeimpossible tocJampthebearing without changing theeffective preload. Theoriginal designofbearing retainer foroneoftheendsofthe AVHRR hysteresis scanner motorwasasimpleflatwasher fastened tothemotorhousing witheight countersunk screws. Thisdesign produced springratesintheshaftaxialdirection inexcess of875,000 N/mm.Thustherewaslittleoftheflexibility thatistypically desired inabearing retainer design. 41
Figure7.FEAAnalysis ofNewBearing Retainer Compared tothealternatives suchaswavewashers anddiscsprings, thisspringisjustascompact while havingagreater loadcapacity andahigherspringrate.Bothofthesefeatures makethisdesigncapable ofsurviving highvibration loads,whichwouldbewellbeyond thecapability ofthewavespringordisc springs. Table4presents anapproximate summary ofcapabilities forabearing usedintheAVHRR scanner. Table4.Comparison ofSpringCapabilities Property NewRetainer Design WaveSpringz Working Load 1779N 66.7N Working Height SpringRateDiscSpring 102.3N 1.91mm 1.52mm 0.51mm 70,050N/ram 110.8N/mm 179.7N/mm Numbers shownareapproximate basedona1inODbearing similartowhatisusedintheAVHRR scanner 43
ThenextaspectofthebearingmountdesignisshowninFigure8.Thisistheballbearingretainer.It appliestheloadtotheouterracethroughthecombinedpreloadresultingfromthetorqueon4bolts(a moreuniformloadingconditionwouldbeachievedbyusing8boltsorscrews).Thispartismatch machinedtothe"stick-out"ofthespecificbearingandhousingused. Thebasicapproachisthatastorqueisappliedtotheretainerbolts,therearretainerspringelement deflects.ThismatchmachiningisdesignedtoprovideaspecificdeflectioninthespringshowninFigure 7.Oncethatdeflectionhasbeenachievedtheretainerseatsagainstthehousingandnofurthertoadis impartedtothebearing.ThisresultsintheforceversusdeflectioncurveseeninFigure9forthenew design.ThiscanbecomparedtothecurvefortheolddesignalsoshowninFigure9.Thereductionin variationprovidedbythenewdesignisveryapparent. RETAINERBEARING Figure8.BallBearing Retainer Acrosssection ofthenewdesignintheassembled condition isshowninFigure5. Intheolddesign, thehighstiffness oftherearretainer meantthatotherpartsofthesystem woulddeflect. Thustheloadonthebearing wouldbedependent upontheactualpreload applied bytheretaining bolts andtheactualdimensions ofthepieceparts.Theolddesignusedshimstoattempt toachieve atailored fit(instead ofmatchmachining) however thisallowed excessive variation giventhehighstiffness ofthe rearretainer. 44
BearingLoadversusClampingTorque 2500 _-2000v 1500 1ooo m500 1 2--NewDesign :::::: i 3 4 5 6 Bearing Retainer Clamping Torque(N-m)7 8 Figure10.Bearing Loadversus Clamping Torque Characteristics Thenewdesign combined withmatchmachining resulted inaconsistent assembly, thatwascompact yet,flexible. Theeffectiveness ofthenewdesignhasbeenproven byitssuccessful implementation on thePOESAVHRR scanner. Modaltesting performed beforeandaftervibration showed littlechanges in natural frequencies. Running torquedatatakenonthemotorshowed aconsistent preload. Asummary of themodalperformance isshowninTable5. Table5.Comparison ofModalDataNewDesign versus OldDesign FirstModepriortoVibeOldDesign 290NewDesign 270 FirstModeafterVibe 240-220 270 Delta 50-70 0 TableUnitsarehertz Measurement errorofmodesisestimated tobe5Hz. Numbers inTableareapproximate, basedonanumber of"OldDesign Builds." Conclusion Whenworking withanexisting design andattempting totrouble shootorimprove theexisting design, improving oneaspectcanhaveunintended consequences, orindicate othershortcomings inthedesign. Asystematic systems engineering approach mustbetakenonanyredesign efforttoaccount forallthe factors andrequirements thataffectthedesigns performance. Averycompact andflexible, yetstrong, bearing retaining system wasdeveloped fortheAVHRR scanner. Theuseofdetailed finiteelement models andnonlinear analysis enabled thedesigntobesuccessfully analyzed andimplemented. 45
Thenewbearingmountdesignhasthefollowingfeatures: Theabilityofthebearingstoselfalign.SincethefingersshowninFigure7eachsupportasectionof thebearingtheywillindependently adjusttoprovidethecorrectsupport.Thisprovidesrepeatability ofassembly. Thehighspringrateoftherearretainer(Figure7)coupledwiththesolidmountingoftheretainer (Figure8)allowstheassemblytosurvivehighlevelsofvibrationwithoutachangeinassembly position.Asaresultthedesignisabletoachieveoutstanding deviceperformance. Itprovidesastablebearingpreloadoverthermalvariations Apatentonthisapproachhasbeenappliedfor.TheUnitedStatesPatentandTrademark Officehas issuedSerialnumber09/702,510 fortheapplicationfiledon31October2000. , , 3.References BallandRollerBearings Theory, DesignandApplication, Johannes Brandlein, PaulEschmann, Ludwig Hasbargen, KarlWeigand, JohnWiley&Sons,NewYork,1999,p.311. Smalley SteelRingCompany Catalog, Wheeling, Illinois,60090. Machine Design Theory andPractice, ArronD.Deutschman, WalterMichaels, Charles E.Wilson, Macmillian Publishing Company, NewYork,1975,p.454. 46
/ ( Retractable Trunnion PinMechanism WayneJermstad* andMarkLandeck* Abstract TheX-38isatechnology demonstration projectfortheproposed International SpaceStationCrewReturn Vehicle. Theproject consists ofseveral atmospheric flightvehicles andanunmanned spacecraft. This paperwilldiscuss thedesign, development, andtestingofaRetractable Trunnion PinMechanism usedto mountthespacecraft inthepayload bayofthespaceshuttleorbiterforlaunch. Introduction TheX-38Vehicle 201isanunmanned spacecraft beingdeveloped in-house atNASA's Johnson Space Center (JSC)byajointgovernment/industry team.TheV-201spacecraft islaunched inthepayload bay ofthespaceshuttleorbiter. Figure 1showsthegeneral arrangement oftheV-201spacecraft inthe payload bay.TheV-201spacecraft isattached tothespaceshuttleorbiteratfivepointsusing82.55-mm (3.25-in) diameter trunnion pins.Threetrunnion pinsarelocated ontheDe-orbit Propulsion Stage(DPS), whichisattached totherearoftheV-201spacecraft. Twotrunnion pinsattached totheorbiterIongerons carryXandZloads,andakeelpincarriesYloads.Theremaining twotrunnion pinsaremounted tothe forward bulkhead oftheV-201spacecraft andcarryloadsintheZdirection only.Because thenoseofthe V-201spacecraft isquitenarrow, anAirborne Support Equipment (ASE)cradleisusedtoprovide a mounting pointfortheforward trunnion pins.Thepinsprotrude fromtheV-201spacecraft andare retained byPayload Retention LatchAssemblies (PRLAs). Thesepinsmustberetracted beforere-entry oftheV-201spacecraft toprovide theoriginal outermoldlineshapeforaerodynamic purposes. A retractable trunnion pinmechanism hasbeendeveloped tomeettheserequirements. DP8Trunnion Pin De-orbit Propulsion Stage (DPS) Fins Folded DP8 Trunnion Pin Z X y_ ShuttlePayload BayX-38Vehicle 201 Airborne Support EquIprnent (ASE) Retractable Trunnion Pin Mechanism andPRLA Retractable Trunnion Pin Mechanism andPRLA Figure1.V-201Spacecraft inSpaceShuttle Orbiter Payload Bay *NASAJohnson SpaceCenter, Houston, TX Proceedings ofthe35mAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 47
Forward :._!:_ Bulkhead Starboard Trunnion Pin AssemblyPortTrunnion PinAssembly Figure4.Trunnion PinMechanisms Retracted Trumion PinTPS Cap ----__NoseStructure Figure5.Trunnion PinsRetracted Through NoseStructure Themainpartsoftheretraction mechanism areshown inFigure6.Thehousing isahollowcylinder machined fromCustom 455stainless steelbar.Thehousing attaches tothebaseplateusingthetwo mounts. Thetrunnion piniscylindrical withasmooth borethroughout itslength. ItismadefromCustom 455stainless steelandischrome platedwithasurface finishof0.2p.m(8pin)tocomply withshuttle payload requirements. Thetrunnion pinalsohasanotch(visible inFigure6)usedforlatching the mechanism intheretracted position. Anendcapboltsontothehousing andcontains thesilicone rubber bumper inagroove. Alongrodscrews intotheendcapandfitsinsidethetrunnion pinbore.Ontheother endoftherodisastop.Thepistonslidesontherod.Threelockpinsmechanically lockthetrunnion pin andthehousing together. Allmetallic parts,exceptforthetrunnion pinandthehousing, aremadeof15-5 precipitation hardening stainless steel.Thepistonandthethreelockpinshaveatitanium nitridecoating forlowfrictionanddurability. Butylrubbero-rings lubricated withvacuum grease areusedextensively to prevent leakage. 50
Mount Housing BasePlate Rod EndCapBumper LockPins Stop Piston Figure6.Trunnion Mechanism Parts Mechanism Operation During ascent inthepayload bayofthespaceshuttle, thetrunnion pinineachmechanism is mechanically lockedintheextended position usingthreelockpinsspaced 120°apart(seeFigure7). Theselockpinsareseatedinlockpinreceptacles located inthemainhousing oftheassembly. Thelock pinsareheldinposition byapiston.Thepistoniskeptinplacewithaspiralretaining ringandthree springplungers (seeFigure8).Thethreespringplungers arespaced 120°apartlikethelockpins.The springplungers canbeadjusted tochange theoperating pressure ofthemechanism. Bending loadsonthetrunnion pinarereacted bythehousing asabeaminasocket. Theengagement lengthofthetrunnion pininthehousing isabout200mm(7.87Jn).Agenerous radiusonthecomerofthe housing prevents localstressconcentrations atthetrunnion pintohousing interface. Axialloadsonthe trunnion pin(whichcomeonlyfromfrictionatthepintoPRLAinterface) arereacted bythethreelock pins.Because oftheangleofthelockpinsandreceptacles, axialloadsonthetrunnion pingenerate an inwardcomponent offorce,whichisreacted bythelockpinsbearing onthepiston. OncetheV-201spacecraft isdeployed fromtheshuttle andthetrunnion pinsneedtoretract, nitrogen gasissupplied through theinnerrodintothepressurized volume showninFigure8.Whenthepressure induced forceonthepistonovercomes thespringforceofthespringplungers, thepistonstartstomove towardthestop.Assoonasthepistonclearsthelockpins(seeFigure9),thelockpinsmoveinwarddue totheinwardcomponent offorcegenerated bytheslopedsurface onthelockpinsandreceptacles. The lockpinsandreceptacles haveagenerous 37.5°angletoavoidjamming. Inaddition smallspring plungers inthelockpinreceptacles assureinwardmovement ofthelockpins.Oncethelockpinsclear thelockpinreceptacles thetrunnion pincanfullyretract(seeFigure10). 51
Trunnion StopLockPin Receptacle Piston LockPinHousing Rod GasSupply Figure9.Spring Plunger Pressurized Volume CrossSection ofMechanism asPistonStartstoMove Trunnion Stop Figure10.LockPin Receptacle PistonHousing LockPin Rod Spring Plunger Pressurized Volume CrossSection ofMechanism Partially RetractedGasSupply 53
Toprevent rotation ofthetrunnion pinwithrespect tothehousing, aslotiscutintothetrunnion pinanda keyisattached tothehousing asshowninFigure11. Trunnion Figure 11.Socket Head Key CapScrew(2X) Cross Section Showing KeyandSlotinTrunnion Thetrunnion pinretracts rapidly(inlessthanonesecond). Toabsorbtheenergy ofimpactandtoprevent rebounding, asilicone rubberbumper isused(seeFigure12).Anotched groove inthetrunnion pinanda cantilevered latchattached tothemainhousing areusedtolockthetrunnion pinintheretracted position (seeFigure12). Tounlockthetrunnion pinmechanism forre-use, thekeymustfirstberemoved fromthetrunnion pinslot. Thetrunnion pinisthenmanually rotated toliftthelatchfromthenotchinthetrunnion pin.Thetrunnion pincanthenbefullyextended andthekeyputbackinplace.Aplunger isthenusedtopushthepiston backoverthespringplungers intoitslockedposition. TrunnionLatch /Housing Bumper Figure12.CrossSection ofMechanism Retracted andLocked 54
Futuretestinq Acomplete qualification testprogram willbeperformed onthetrunnion pinmechanism. Themechanism willbefunctioned inathermal vacuum testatboththehotandcoldtemperature extremes. The mechanism willbestatictestedto1.2timeslimitloadandthenfunctioned. Qualification forAcceptance Vibration Testing andQualification Vibration Testing willbeperformed, withfunctional testsofthe mechanism aftereach.Lifecycletestingwillbeperformed onthequalification unit.Aftercompletion oflife cycletestingthequalification unitwillbestatictestedtoultimate load(1.5timeslimit).Thetwoflightunits willbeproofpressure tested, haveaspringplunger calibration test,andbeacceptance vibration testedin avehicle levelvibro-acoustic test. Remaining Work Inaddition tothecompletion ofthequalification testprogram, someadditional design workremains on thetrunnion pinmechanism. Microswitches mustbeincorporated forboththeextended andstowed positions. Redundant locking devices mustbeaddedforallthreaded devices. Thisworkwillbedoneprior tothestartofthequalification testprogram. Conclusions Aretractable trunnion pinmechanism hasbeendeveloped whichcancarryahighstructural loadina lockedextended position, thenretractintoalockedstowed position. Development testing indicates that themechanism concept issound.Themechanism canoperate overawiderangeofoperating pressures. Whilethereismoreworktobedone,sofarthemechanism meetsallitsdesignrequirements. 56
Design oftheX-34Speedbrake Mechanism UnderVolume, Stiffness, Cost,andSchedule Constraints William H.Kim Abstract TheX-34Reusable Launch Vehicle (RLV)Technology Demonstrator hasasplitflapspeedbrake mounted toanall-moving vertical tailforenergymanagement duringdescent andforpitchtrimduringascent. The speedbrake isdeployed usingalinearhydraulic actuator thatdrivesapairoftorquetubes.Thedesignof thisspeedbrake mechanism wasconstrained bytheX-34program goalsoflowcostandaggressive scheduling aswellaslimited volume forthespeedbrake mechanism andastiffness requirement to preclude aerodynamic flutter.Thespeedbrake mechanism hasbeendesigned, tested,andintegrated on thefirsttwoX-34flightvehicles. Themechanisms havebeenverified viafitchecks, functional checkouts duringflightsimulations inthehangar, ground vibration testing, andrunway towtesting. Upcoming unpowered approach andlanding testsaswellaspowered flightswillbetheultimate testofthe mechanisms. Figure 1.X-34onDryden FlightResearch Center Lakebed PriortoTowTesting Introduction Thepurpose ofthispaperistoprovide anoverview ofthedesignoftheX-34speedbrake mechanism. Howvolume andstiffness constraints effected thedesignofmechanism willbediscussed. Inaddition, howthecostandschedule constraints effected theexecution ofthedesignaswellasthedesignitselfwill bediscussed. Background TheX-34RLVTechnology Demonstration program isajointindustry/government projecttodevelop, test, andoperate asmall,fully-reusable vehicle withtheobjective ofdemonstrating technologies andoperating concepts applicable tofutureRLVsystems. Orbitalisdeveloping theunmanned X-34,showninFigure1, asanair-launched, liquid-fueled vehiclethatdrawsheavilyonOrbital's Pegasus andTaurus heritage and incorporates manyRLVtechnologies including anall-composite primary airframe structure, composite RP-1tank,SIRCA leading edgetiles,andautonomous flightcontrolwithsafeabortcapabilities. TheX-34 iscarried uprange byOrbital's L-1011carrieraircraftandfliesbacktoitsbaseofoperations atspeeds of uptoMach8andaltitudes of76km(250,000 feet).Itlandshorizontally onaconventional runway andis quicklyreadied forsubsequent flightsusingaircraft-style ground operations. *OrbitalSciences Corporation, Dulles,VA Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 57
Twocompleteairframeshavebeenfabricatedandassembled atOrbital'sDullesIntegration andTest Facility.Athirdfuselagehasbeenfabricatedandiscurrentlybeingassembled. Systemtestingonthefirst airframeisunderwaywithseveralcaptivecarryflighttestsontheL-1011carrieraircraftcompleted and severalrunwaytowtestsatDrydenFlightResearchCentercompletedaswell.Unpowered approachand landingtestsaswellaspoweredflightswillbeperformeduponcompletionofgroundtesting. Requirements TheX-34wingprovides therequired lifttochange thevehicle flightpathangleduringthepull-up maneuver afterseparation fromthecarrier aircraft, andduringthere-entry pull-up. Thewingalso provides crossrangeandmaneuverability duringthefinalapproach andlanding. Aerodynamic attitude control inpitchandrollisprovided byelevons supported offthetrailingedgeofthewing.Afuselage mounted bodyflapalsoprovides pitchcontrol. Theall-moving vertical tailprovides lateralstability andcontrolfortheX-34duringatmospheric flight.A splitflapspeedbrake mounted totheall-moving vertical tailprovides dragwhichisusedforenergy management duringdescent [1].TheX-34speedbrake mechanism isuniqueinthatitisthefirstsplitflap speedbrake mounted toanall-moving vertical tailthatisdesigned fortransonic andhypersonic flight(up toMach8)andisactuated withasinglelinearhydraulic actuator. Inaddition toserving asadragdevice, another uniquefeature ofthespeedbrake isthatitisusedasapitchtrimdevicebothduringascentand descent. AsshowninFigure2,duringthefirst40sofflight,elevondeflection, whenthespeedbrakes are opened to75°,doesnotexceed -15°.Ifthespeedbrakes arenotopened (0°deflection), elevondeflection increases to-20°.Thus,thespeedbrakes provide anadditional 5°ofelevoncapability onascent and keeptheelevons wellbelowthesaturation levelof-34°[2]. Incontrast, theShuttle speedbrake isasplitflapmounted toafixedvertical stabilizer andisactuated with multiple rotaryactuators. ThesplitflapsonShuttle areusedasspeedbrakes between Mach10and5. Theyareusedasbotharudderandspeedbrake belowMach5andareusedforpitchtrimonlyduring descent [3]. 0 -2 -4 _-6 ._-8 -10 _-12 o _)-14 ,m -16 -18 -20 0i'---75°Speedbrake 0_Speedbrake i600 5OO _400 !300 .u 200 100 0 0 10 20Dynamic Pressure Nominal MachNumber 10 20 30 40 50 60 30 40 50 Time(eec) Time(sec)2.00 180 1.60 1.40 1.20_ _E1.00z 0.80 0.60 0.40 0.20 Q00 60 Figure2.TheSpeedbrake isUsedforPitchTrimDuring Ascent toOffload Elevon Demand Theall-moving vertical tailconsists ofarudder, ruddermechanism, twospeedbrakes, andaspeedbrake mechanism. Therudderisfabricated usinggraphite epoxy/aluminum honeycomb monocoque sandwich panelconstruction fortheskinsandribs.Theruddermechanism consists ofasteeltorqueshaftwithtwo tapered rollerbearings. Thespeedbrake panels aremonocoque sandwich panelconstruction with graphite epoxyfacesheets andaluminum honeycomb core.Thespeedbrake mechanism consists of several metallic components. Thedrivingloadcaseforthespeedbrakes occursduringascentwhenthespeedbrakes aredeployed 75° tohelppitchthenoseofthevehicle up.AsshowninTable1,atMach1.25andadynamic pressure of 58