ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Gas Generator'--_ Flywheels (3places) Control Electronics Figure1.MissileIntegrated PowerandRollSystem Background MIPARS consists ofathree-flywheel array,controlelectronics, andamultiple-ignition solid-propellant gas generator. Thegasgenerator supplies high-pressure hotgasto1)spinuptheflywheels and2)provide divertmaneuvering thrustfortranslational controloftheKW.Theflywheels providecontroltorquesfor attitudecontrolbyrotatingthemomentum vectorswithagimbal,andprovideelectrical powerby extracting energyfromtheflywheel usinganelectrical generator. Theblockdiagram inFigure2illustrates howthesystemworks.TheKWisthefourthstageoftheNavy's standard missile. Twoseconds priortofourth-stage separation, thegasgener-ator isstartedandthe flywheels arespunup.Afterseparation, theguidance computer issuestorquecommands tothe flywheels tocontroltheKWattitudeandforcecommands tothethrusters tocontrolthetrajectory ofthe KW.Duringperiodswhentrajectory adjustment isunnecessary, thegasgenerator isextinguished and thenitisreignited laterwhenthrustisrequired. Throughout theflight,theflywheels supplypowertoall theKWsubsystems andattitudecontroltorquetotheKW.Table1summarizes theMIPARS requirements. Flywheel Theemphasis ofthispaperisonthegimbaled flywheel. Theflywheel hastwofunctions 1)provide attitudecontroltorqueand2)providepowertothekineticweaponthroughout its300-second flight.It replaces conventional thermalbatteries andbanglbang attitudecontrolvalves. 360
Seeker --_ Rate __[--* Gyros Divert Control Thrusters / Multi-ignition Gas PropellantGuidance _Gimbal Computer _Control 1 Divert :: Thrust i Reactor Oxidizer MK_G ControllerGimbal Rotor TurbineRywheel Array Gimbal Generat or Converter Rotor Bectronics Turbine Gimbal Generator i: Rotor!: TurbineSpeedSense--- Bectronics----- .......................................................... Figure2.MI'I_Ai_S BlockDiagram Table1:MIPARS Specification Parameter Requirement 150kJ Energy Storage PeakPower 650W Mission Duration 300s(maximum) Steering Torques 45.2N.m(pitch,yaw)22.6N.m(roll) DivertThrust 1557N(twoaxes) ThrustDuration 10seconds Weight <27.3kg Envelope 25.4-50.8cm(diameter) 38.1-63.5cm(length) Non-operational Temp -29to+54degC Magazine Temp +7to+32degC Altitude 70-200km__Supply !Voltage Fromthesystem powerandattitude controlrequirements, theflywheel requirements inTable2were derived. Theapproach toderiving therequirements isasfollows: • Selected thespeedrangeof2:1forefficient operation oftheelectronics. • Selected therequired energystorage basedonconservative energylossestimates duetothe bearing dragtorque, theeddycurrentlossesinthemotor,andtheefficiency oftheelectronics. • Selected arotorsizethatwouldfitwithinenvelope andweightrequirements. • Derived therotorspeedtoachieve thedesired energystorage. • Calculated theaverage spinuptorqueneeded toachieve fullspeedintwoseconds. • Calculated therangeofangular momentum available formomentum exchange withtheKW. • Calculated themaximum gimbalraterequired toachieve maximum attitude controltorqueat minimum rotorspeed. 361
Calculated themaximum gimbalholding torquetoholdtheflywheel inposition whenmaximum crossaxisratesarepresent Calculated themaximum required gimbalacceleration toachieve adequate fullpowerbandwidth. Calculated thegimbaltorquefromtherequired acceleration andtheholding torque. Setthegimbalrateloopbandwidth forusewitha5to10HzKWattitude controlbandwidth. Table2:Flywheel Requirements Parameter Maximum RotorSpeed Maximum RotorEnergy Useable EnergyStorage Maximum MomentumRequirement 42000 120Units rpm kJ 50.0 kJ 54.6 N-m-s Minimum Momentum 27.3 N.m-s PeakGimbal Rate +1.8 rad/s 75 19.0 400.0 +180 27.3 2 3.8Gimbal RateLoopBW Holding Torque Maximum GimbalAcceleration Gimbal AngleRange Spin-up torque Spin-up time Weight!Hz N.m rad/sz deg N-m sec k9 Theflywheel consists ofahubandrotorassembly, anelectrical generator, aturbine, ahousing, amotordrivengimbal, andanelectronics package. Theturbineisusedtospinuptheflywheel to42000rpmtwo seconds priortofourthstageseparation. Theenergystoredintherotorduringspinupisextracted from theflywheel topowerth-eKWduringflight.Tosupply[0rquetheflywheel isrotatedonagimbalwhose axisofrotation isperpendicular tothespinaxis.Thetorqueapplied bytheflywheel isthengivenby T=_xH where, coisthegimbalrate,and Histhemomentum oftheflywheel Theelectronics package, depicted inFigure3,consists ofaspinupcontroller, apowersupply, agimbal controller, andacommand andtelemetry processor. Thespinupcontroller isusedduringspinupto solicittheturbinegasflowandshutsoffthegaswhenthewheels reachspeed. Thepowersupplytakes th_6utput ofthegene_tor andconvertsit tOdc_voffages us_by th=e_iThegTmb_lcon[roiier accepts commands fromtheattitude controlsystem andcontrols thegimbalratetoprovide thedesired attitude controltorque. Thecommand andtelemetry processor provides thenecessary interfaces tootheron boardsystems andanyKWtestequipment. Flywheel Rim ....... TheinitialdesigneffortoftheMIPARS benchmodelhardware wasaimedatutilizing asimpleturbine designasan"add-on" tothe:Shaft ontheoutside ofthehousing. :itappeared thatthiSW0uid bethemost economical Use6f-de_,[gn effort.Several concerns led-us_-re+:eva[uate thatdecision andproceed to designanintegrated flywheel andturbineforthetesthardware. Rotor-dynamics studiesofpotential turbine/flywheel configurations illustrated thedifficulty inhavingtwolargernasses attheendsofthe support shaft.Thiscaused aIstmodebending criticalspeedranging from15k to25krpm,whichisinthe middleoftheoperating rangeoftheflywheel forSot_:_ow_r generation andattitude controltorque application. Inaddition, themechanical configurations werebecoming ungainly andtheassembly ofthe partsmoredifficult. Asaresultwearrivedatintegrated turbineandrimdesign. Theresultisthe hardware pictured inFigure4.4 t 362
Computer  PWM Amplifier  aC°T_I_ -  ee[_Gimbal TachH Gimbal IGear[.I  Motor[r ain]G'mbal[ Gimbal ] I ']ehI Control Computer Commands  Valve Turbine ] i [WheePeriod --[ Estimator 28VdcINT I_FW1 ! DCtoDCLFW2 Converter FW3Rotor I i Generator ]Gimbal Angle Sensor Figure3.BlockDiagram ofFlywheel Electronics Therotor,withintegrated turbineblades(Figure4),wasdesigned toprovidethebladedesignand appropriate nozzleandbladetipclearances. Theflywheel/turbine isfabricated from4340-HS steeland hardened toRC53toprovidebothhighstrength (1862MPa(270ksi))andgoodductility(11% elongation). Allmachining exceptfortheinterface diameter withthehubwasdonepriortohardening, greatlyreducing potential production costs.Comments fromthefabricators ofthehardware indicated that theheattreatprocesscreatedverylittledistortion thusopeningthepossibility ofhavingnofinalgrinding operations, whichcouldfurtherreducecosts. Similarly, thenozzledesignwasiteratedtocreateadesignthatwascompatible withtheflywheel layout. Thebenchmodelnozzle,showninFigure5,isatwo-piece assembly witharectangular nozzlecrosssection. Screwsattachthetwocomponents. Figure4.Flywheel Rim 363
Figure5:Turbine Nozzle HubDesiqn Initialdesigndirection forthisflywheel anticipated anintegral hubandflywheel. Detailed FEAanalysis of theconcepts quicklyrevealed thatsuchadesignwouldnotleaveadequate safetymarginforatestbed device. Analternative designusingaseparate hubwasanalyzed (Figure6).Thehub/flywheel interface isaninterference fit(0.2mm(0.008inch)radialinterference) thatprovides radialcompressive stressto maintain contact between thepartsuptoapproximately 54,000-rpm. Although thisresultsinadditional hoopstressintheflywheel andcompressive hoopstressinthehub,theoverallbalance istoimprove the stressseenbythehub,theoriginal problem area. Sincethetendency fortheflywheel istogrowfasterthanthehubasthespeedincreases, the compressive radialinterface stressdecreases withincreasing speeduntilthepartsactually separate. A designobjective wastoincorporate radialseparation oftheflywheel andhubpriortoanycatastrophic hoopfalures yetstillhavethisSpeedbeweltaboveplanned operational speeds. Thisdesignhas,in effect,abuiltinsafetyvalvewheretheflywheel becomes looseonthehub.Thispermits theflywheel to translate axiallytocontact eithertheendhousing orthenozzleassemblies. Friction resulting fromthis contact wouldthenslowtherotation; essentially itisabuilt-inover-speed brake.Inaproduction design, thisfeaturecanbeeasilyadjusted oreliminated ifdesired. Duetothehighstresses seenbythehub,it, liketheflywheel, washardened toRC-53. Sizeandconcentricity tolerances weremaintained through the hardening procedure andnofinalgrinding wasrequired. Figure6.Flywheel RotorParts 364
RotorAssembly: Attachment oftheRotorShafttothehubwasaccomplished withtheuseofshrinkfit,freezing theshaftin liquidnitrogen (LN2)to-184°C (-300°F) andheating thehubto+149°C (+300°F). The0.038mm(0.0015 in)interference between shaftandhubborediameters isrelatively easytoovercome. Thehub/shaft subassembly isthenchilledinLN2to-184°C andtheTurbine/Flywheel isheatedto+149°F. Againthis permits arelatively easyassembly forthe0.4mm(0.016in)interference oftheinterface diameters. Finally,themotorrotorispressed intoposition withtherestoftheassembly beingcooledto -73°C(-100°F). Theinterference issuchthatthisoperation couldbereplaced bypressing themotor rotorontotheshaft,butthethermal shrinkmethod eliminates anyshaftscoring. Atthispoint,therotor assembly lookslikethesolidmodelshowninFigure7. Hub InertiaRim Furbine Blades Figure7.Modelofrotorassembly Generator/Motor: A6-poleslotless, brushless DCmotor,manufactured byElincoMotors, wasselected foruseasthe generator. Themajordesignconsideration otherthanproviding poweratthedesignvoltage wasto minimize theeddycurrentlossescaused bythepassage ofthehigh-speed rotating magnets ontherotor pastthestatormetal.Inthisparticular testbedapplication, itisthetestingandutilization ofthegenerator to"motor-up" theflywheel rotortotheoperating speedof42,000rpmthatwasthekeydriverofthemotor design. Thisslotless designwasselected afterhavingreviewed numerous otherbrushless motoroptions andweighing thecostofdesigning acustom motorfromscratch todothisjob. Therotorconsisted ofasteelinnerring,anon-magnetic outersleevetocontain the6magnet arcsanda brassinserttoprovide asacrificial masstobeusedtobalance themotorrotorassembly. Themotorrotor isshrunkontotheshafttoprovide adequate interface pressure tooperate at>50,000 rpmwithout coming loose.Thisisthefinalpartassembled ontotherotorfollowing theshrinking ofthehub/shaft and turbine/flywheel together. Thestatoristheuniquefeature ofthismotorthatprovides loweddycurrentlosses. Thewindings fill essentially allofthespaceontheinsidediameter ofthestator;thereisnomagnetic material atthemotor airgap.Thereisaslotless lamination stack(simple discs)outside ofthewindings. Theeffectofthisisto increase thespacetothelamination stackandreducethepotential togenerate eddycurrent lossesdue tothehigh-speed passage ofthemagnets bythestatorlaminations. Figure8illustrates thesedesign features. Finally,whenthestatorisinstalled intothemotorhousing cavity,thereisaninterference fittoprovide a goodpassive thermal linktothehousing tohelpdissipate thestatorpowerlosseswhentheflywheel is motoring uptospeedinparticular. Thisisanadequate solution forthetestphasesinceitprovides adequate timetoaccelerate tospeedbeforeweexceed the150°Ctemperature limitonthestator 365
Figure8.Slotless Generator/Motor windings. Athermocouple wasattached totheendturnssothatthistemperature couldbemonitored duringtheoperation ofthemotor.Theanticipated temperature risesfortheflightunitsoperating asa generator onlyaremuchlessseverethanforthelong-term vacuum testsequence wheretheelectric machine wasusedasbothamotorandagenerator. Flywheel Bearinqs Torrington Superprecision stainless steelangular-contact ballbearings (2MM201WI-CR witha15° contactangle;ABEC-7) wereusedwithaphenolic retainertobeabletohandlethehighspeed.These bearings havealimitingPDxNvalue(PDinmmtimesRPM)of1,400,000 foroillubrication. Forthis application, wehaveamaximum valueof1,000,000 forPDxN.Lubricant willbeeitheravacuumcompatible oillubricant orasolid-film lubricant suchasDiacronite toprovidegoodshelflifeandcoldstartupcharacteristics withlowfrictionduringhigh-speed operation. ThebenchmodelutilizedNyeSynthetic Oil2001Atoprovideprotection tothebearings forthelongduration testinginavacuumenvironment (<1 millitorr). Thebearings areaxiallypreloaded throughtheshaftwithaforceofapproximately 133N(30 Ib)bytheuseofwavespringwashers ontheouterraceofonebearing. Onlyonesetofbearings was usedforallofthetestingandnoobservable performance changewasnotedoverthetestduration. Thetwobearings are"soft-mounted" intotheendhousings withtheuseoftwogreased O-ringsforeach bearing. TheseO-ringsarelocatedbetween thebearingoutsidediameter andthemounting cavitiesin theendhousings andprovideaneffective bearingstiffness of35-52kN/m(200-300 Ib/in).Figure9 illustrates thisbearinginterface concept. Thisdesignlimitstheforcesthatcandevelopasaresultofany structural resonance excitedbywheelfrequency. Itallowsradialmotionof+0.05to0.076mm(+0.002to 0.003in)of"soft-mount" beforethebearingouterracecontacts thealuminum bearinghousing. Thislevel ofradialfreedom ismorethanadequate toreducetheinterface forcesbetween therotorandthehousing toverylowlevels.Whilewithinthis"soft-mount" region,unbalance forcesarelimitedtolessthan4.5N(1 Ib).Inaddition, thesegreaselubricated O-ringsprovidesomeradialdamping aswellaslowaxialfriction forcetomaintain theaxialpreloadforces.However, thereisaneedforanaxialstoptolimitthemotionof theouterraceonthespring-loaded end.Duetoanextremely highgimbalinputrate,contactofthe housingwiththerotational stop,enoughaxialforcewasgenerated totranslate theouterracetothepoint whereenoughradialclearance wascreatedtopermitinterference between therotorandthecaseatthe turbinebladeoutsidediameter. Thiscanbeeasilyresolved withanaxialstopthatlimitsthistravelto0.13 to0.25mm(0.005to0.010in). Finally,thisbearinginterface systempermitstheouterracestoseektheirmostdesirable operating attitudethatisdetermined bytheaverage planesoftheinnerandouterbearingracesratherthanbythe outerdimensions oftheouterrace.Thisfeaturefurtherlessensbearingpowerlossesandimproves bearinglife.Although bearinglifeisnotasignificant issuefortheMIPARS flightsystems, otherlonger duration systems couldwellbenefitfromthesebearingsystemfeatures. 366
TestRiqDesiqn Thefunction ofthegimbaltestrigforthebenchmodelflywheel istoprovide thecapability ofputtinginan angular rateaboutanaxisofrotation, thetrunnion axis,thatisnormaltotheflywheel axisofrotation. Thisresultsinanoutputtorquevectororthogonal toboththespinaxisandthetrunnion axisthathasa magnitude equaltotheproduct oftheflywheel angular momentum andthetrunnion anglerateinrad/s.It isthisreaction-torque thatisusedtoredirect theflightpathofthemissile. Theentiretestrigisattached to atorquesensorsothatthereaction torquecanbemeasured andtheperformance ofMIPARS evaluated. Figure10illustrates theflywheel initshousing mounted tothegimbaltestrigwithastub-shaft attached to eachsideofthehousing. Theseshaftsdefinetheaxisofrotation normaltotheflywheel spin-axis. A radialbearing inoneoftheuprights supports onetrunnion shaftandothertrunnion shaftattaches tothe Gimbal torquer andusesitsoutputbearing. Thegimbaltorquer isattached totheotherupright. Finally, thereisasimpleangular stopwithtworubberpadstolimittheangular motionaboutthegimbalaxisto approximately +30°bycontacting thecornerofthelowerbearing housing. Oi RadlalMetlenofFIfwkeelRotor Figure9.Bearing Soft-Mount Design Slotless/Brushless DC Motor/G enerator /Hub _ //_Cover Fl_heel_ _ Nozzh_ ×\_'_.......nL..=._, "_\Housing H\\'Harmonic Drive_-,._ ...._ -Shaft __ ServoController _'_ "_Trunnion Bearing [_ __... __\_"-._ Housing [_,_. "-DriveSupport Bracket Figure10.TestRig 367
Test Testswereconducted todemonstrate compliance tothespecifications. •Spinuptests •Attitude torquetests •Powerandenergytests •Efficiency tests Figure11isaphotograph ofthetestunit.Specific testsincluded Figure11:BenchModelFlywheel Gimbal TestConfiguration Theflywheel hardware isassembled intothegimbalbracket, coupled tothegimbaltorquer andthen attached tothetopmounting faceofasix-degree-of-freedom force/torque sensor. Thesensorusedisa straingagesensormanufactured byAssurance Technologies Inc.(ModelFT3224Theta550/3300). The sensorhasatorquelimitof373N-m(3300in-lb)aboutallthreeinstrumented axesandaresolution of0.2 N-m(2in-lb)overthatrange.Thistorquesensorisfirstattached totheinterface plateinthevacuum chamber; thisinten_massembly ispictured inFi_Ure 12.Thegimbaltesirig!sthenattached tothe movable topsurface_6fthe_sens0r inthevacuum Chamber asshowninFigure!3priortothevaCuumtightcoverbeingattached. Allinternalelectrical connectlons aremadeandallfunctions areverified. The endcoveristhensecured, aroughing vacuum pumpisattached totheoutletoftheturbo-pump andall external electrical connections aremadeandoperation verified. Thistestchamber provides apressure duringtestingoflessthan1millitorr. Thisisequivalent tothepressure atanaltitude of90kmand provides agoodrepresentation oftheendusewindage lossestobeexpected intheactualflightsystem oncethehotgasses, usedtoaccelerate theflywheel, areventedfromtheflywheel housing.i 368
Figure12.Ckamber TorqueSensor Figure13.GimbalTestRig SpinUpTest Figure14belowshowsaspin-upevent.Spinupisachieved bydiverting hotgas(1038-1371°C (19002500°F)) fromthekineticwarhead's gasgenerator ontoaturbinemounted ontheflywheel rim.Thehot gasdrivestheturbineuntilthetopspeedisachieved atwhichtimeitavalveclosesandadumpvalve extinguishes thesolidgasgenerator. RotorSpeed, Torque, &DrivePressure vsTime (RPM,ft-lbfx1000,PSIAx100) 160,000 140,000 120,000 100,000 80,000 60,000 40,000 20,000 , 0.0 0.5GASGENERATOR PRESSURE 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Time,sec. Figure14.Results ofHotGasSpinUpTest 369
Dischar.qe Test Thedischarge testdemonstrated MIPARS abilitytosupplypowertotheKWduringitsflight.Thewheel wasspunupto37000rpmandthendischarged intoa250-ohm resistor. Thevoltage acrosstheresistor washeldconstant bythevoltage regulator. Thisresultsinaconstant powerdischarge. Figure15 illustrates theenergyusageduringthedischarge cycle.Thelowercurverepresents theenergy dissipated inthe250-ohm resistor duringthedischarge. Thecentercurverepresents theenergy dissipated inthemotorandbearings duetothedragtorqueaddedtotheloadenergy. Thetopcurve showstheenergyremoved fromthewheelasfunction oftime.Thedifference between theenergy removed fromthewheels andthelossplusloadenergyrepresents theenergylostintheelectronics and additional energylostinthemotorduetoresistance losses. Ascanbeseen,thelossesarehigherthan expected. Werecovered only21kJofenergyfromtheflywheel. Ourfailureinvestigation revealed there wasaviscous losscaused byexcessive eddycurrent lossesinthegenerator. Acustom generator designisrequired toovercome theselosses. 70000 60000 50000 Energy fromRotorBearing Loss •40000 o Generator and  Electronics 30000 Loss Energy Delivered toLoad 20000 10000 _me(s) F|gurelS. ResultsofDischargeTest A_ttitude Torque Test Thepurpose oftheattitude torquetestistodirectly measure thegyroscop!c torqueapplied bythe flywheel. Theflywheel ismounted onatorquemeasurement platform andtheentireassembly is mounted inthevacuum chamber. Thewheelisspunuptoabout21000rpmandagimbalrateis commanded. Themomentum ofthewheelmultiplied bythegimbalrateyieldsagyroscopic torque, which ismeasured bythethree-axis torqueplatform. Aplotofthevectorsumofthemeasured torques isshown inFigure16.Noticethatthetorqueresponse isquitenoisy.Thisnoiseismostlycaused bystructural resonances duetogeartraincompliance andbybacklash andothernonlinearities inthegeartrain,tt doesnotappear intherateresponse sincetherateismeasured attheinputofthegeartrain.Depending onthetorquerequirements oftheKW,moreworkwillberequired inphase3todesignasuitable gear train.Asummary ofthetorquetestsappears inTable3.Thetorqueerrorisquitesmallandwouldisvery acceptable foraKWattitude controlsystem. 37O
Inadvertent RotorCrashTest Thefinaltestinvolved simultaneously delivering powerandapplying attitude controltorque. Thecontrol system wasconfigured sothattheinputtothetorqueloopwasatorquecommand. Thecontrolsystem thenusedthemeasured wheelspeedtocalculate therequired gimbalrate.Thewheelspeedwas measured usingthesameHalleffectdevices usedtocommutate themotor.Unfortunately, themotor currents affectthemotormagnetic fieldthatdisrupts theHallsensoroutputs. Asaresultthemotorspeed measurement wasquitenoisyresulting inanoisygimbalratecommand. Thenoisesaturated thegimbal rateloopcausing thegimbaltotravelfromstoptostop(~60degrees) atabout20rad/s.Whenthis happened therotorwasspinning atabout40000rpm.Thecombination ofthehighrateandhittingto stopscaused therotortotouchdowninsidethecase.Theinsideofthehousing wasslightlyscoredbut therotorwasnotdamaged. Infuturedesigns anaxialstopwillbeaddedtolimitrotormotionduetoan unexpected gimbaloverrate. Also,aseparate rotorspeedsensorwillbeadded. MiparsTorqueResponse --Wheel Soeed =2t.65 -_Gimbal Rate=1.08rad/s T_--,_--_7 Figure16.Attitude Torque Response oftheMIPARS Flywheel Table3.Attitude Torque Performance Summary Gimbal Rate WheelSpeed Predicted Torque (rad/s) (krpm) (N-m)(in-lb)Average Torque (N-m)(in-lb)Error 0.09 22.4 2.53(22.4) 2.49(22.0) -1.8% 0.18 21.6 4.88(43.2) 4.88(43.2) 0.0% 0.36 21.6 9.76(86.4) 9.47(83.8) -3.0% 0.54 21.7 14.7(130) 14.9(132) 1.4% 0.72 21.6 19.5(173) 19.1(169) -2.2% 0.9 21.7 24.5(217) 24.4(216) -0.5% 1.08 21.7 29.4(260) 29.3(259) -0.6% 1.08 27.7 37.5(332) 38.3(339) 2.0% 1.26 21.8 34.5(305) 34.5(305) -0.t% 1.44 21.2 38.3(339) 38.4(340) 0.2% 1.62 21.2 43.2(382) 42.9(380) -0.4% 371
Conclusion TheworkdoneonMIPARS showstheconcept ofproviding attitude controlandenergystorage using flywheels isviableandattractive. Theflywheels offersignificant performance advantages overattitude controlthrusters including Continuously variable andsmooth torquedelivery resulting inmoreprecise andstablesensor-ontargetpointing Efficient andreliable energystorage Abilitytoprovide attitude controltorqueandpowerwhenthegasgenerator isshutdown Enables longduration (>300seconds) flightusingmultiple ignitiongasgenerators Ourtestingdemonstrated thefeasibility oftheconcept andalsouncovered somedeficiencies inthe design. Thesedeficiencies andtheirmitigation aresummarized inTable4. Table4:Lessons Learned Problem Poorefficiency Largeattitude controltorque noise Rotortouchdown afterstop contact NoisywheelspeedmeasurementCause Excessive motoreddycurrent losses Geartrain noiseduetobacklash andcompliance Excessive axialrotormotion allowed Interaction ofthemotorcurrent withthemotormagnetic field causeHalleffectdevices to produce anoisyoutputMitigation Custom highspeedmotordesign Stiffergeartrainwith antibacklash gearing Addaxialstop Useanindependent opticalor magnetic ratesensor Overalltheflywheel performed verywellandasaresulttheMIPARS concept isseriously being considered forinclusion infuturegenerations ofexoatmospheric interceptors. Acknowledgements Theauthors wouldliketothanktheNavalAirWarfare CenterWeapons Division forthesupport ofthis work.Inparticular wethankArnieDanielson, MartinMinthorn, JerryKong,andDr.Pashang Esfandiari fortheirinputsandguidance.4 372
J/Y/NAS,_CP_2001 -209626 35thAerospace Mechanisms Symposium Compiled by:Edward A.Boesiger Proceedings ofasymposium heldat TheFourPointsHotel,Sunnyvale, CA Hosted bytheAmesResearch Center and Lockheed MartinSpaceSystems Company Organized bytheMechanisms Education Association May9-11,2001 May2001