ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Table6:Material Properties ofDISPAL S225Compared toAlternative Materials. Mech.property Tension Strength YieldStrength • YoYou_Eg's Modulus Specific Mass CTTE(21-100°C)DISPAL S225 265MPa 192MPa 93000MPaAL3.4364T7351 480MPa 420MPa 71000MPa 2620kg/mJ2890kg/mJ 10.2-10-°1/K 23.10"bIlK Material DISPAL S225AA7075T7351Ti3.7164.1 900MPa 830MPa 110000 MPaSteel1.3543 1970MPa 1900MPa 216000 MPa 4490.kg/m_8000k£1/m_ 910°.l/K 10.1.10.°I/K MIL-T-9046 AISI440C Antenna andtheAPMI/Fplatewithout producing significant deformations intheAPMgimbalbracket. TheI/Fbetween theAPMandSatellite panelconsists ofa5-screw holepattern (3ononebasebracket, 2 ontheother). Theattachment screws areequipped withthermal washers outofGFRPinordertolimit theheatfluxfromthesatellite totheAPMandviceversa.Anoptional Baseplate withI/FtotheAPMonly butnottothesatellite panelcanbeusedtoaccommodate accessories suchaswaveguide brackets, connector brackets, harness etc.without affecting thesatellite I/F. TheGimbal Brackets areequipped withpairsof440Cbearings inanXarrangement (Table7).Each gimbalaxisisequipped withapairoffixedandapairoffloating bearings. Theaxialmotioncapability is realized byapairofBeCumembranes, whichinterface withthecorresponding bearing pair. Characteristics MaterialTable7:Bearing Characteristics FixedBearing Xl02CrMo7 (1.3543) 37mm OuterDiameter Bore 20mm 30mm= CageMaterial PTFE PTFE Lubricant Thickness ofLubricant Film Arrangement PreloadIon-sputtered MoS2 <0.5IJm Xarrangement 343NFloating Bearing X102CrMo7 (1.3543) 47mm Ion-sputtered MoS2 <0.5IJm Xarrangement 267N P0tenti0meter /Encoder Interface Inthebaseline design, IIFflanges areforeseen onbothAPMaxesinordertoallowtheaccommodation of acustomer-specific position-sensing device(potentiometer orhigh-resolution encoder). Intheactual design, open-loop steering formsthebaseline. Sprinq/Damper Unit TheGimbal BaseBracket aswellastheGimbal FrameBracket isequipped withaSpringUnitallowing to forcetheGimbal viaaleverarmagainst thelinearoutputI/FoftheAPMactuator duringoperation. By thisconcept, theactuator I/Fispreloaded withanalmostconstant forceovertheoperation anglesothat hysteresis effectsintheactuator canbelimited. Theconcept impliesthateachgimbalaxisisoperated in onedirection bymoving thelinearactuator against thespringforcewhileintheotherdirection thespring forceisusedtotiltthegimbalsimultaneously withtheretracting actuator. Duringlaunch, thegimbalis lockedbytheHRMsinaposition outside thenominal APMworking rangesothattheactuators areoutof themechanical loadpathanddecoupled fromtheantenna. Afterreleasing theHRMsinorbit,theSpring Unitsforcethegimbalagainst theactuators sothatapre-adjusted firstmission configuration canbe achieved without activation oftheactuators. Inordertoreducetheshockloadsintheactuator I/Fdueto gimbalrelease, adamper unitequipped withasetofBelleville washers isprovided intheactuator I/F. TheBelleville washer package ispreloaded suchthatthemaximum forceapplied bytheSpringUnitis 292
alwayssmallerthanthepreloadofthedamperunit.Bythismeasure,adefinedpositionofthedamper systemisalwaysassuredinoperational conditions. LinearActuator Besides theGimbal Assembly, theLinearActuator formsthesecond majorassembly oftheAPM mechanism. Oneactuator comprises atwo-phase stepper motor,aplanetary gear,andanut/spindle unitwithlinearguidance. Duetothecogging torqueofthemotor,theratioofthegearandthechosen smallspindle pitch,theactuator provides goodbackdriving torquecapability sothatthefirstmission pointing position canbepre-adjusted onground without losingitduringlaunch. Figure3showsthelinear actuator design. Motor JActuator Housing I Reference Switches Spindle UnitI Actuator OutputFlexible Coupling Figure 3:APMLinearActuator MotOr Themotorisatwo-phase discrotorstepper motoronthebasisofanindustrially available type (Portescap P532),butmechanically modified inordertoadapttotherequirements andtemperature environment ofspacemissions. Themotorconsists basically oftwostatorpartscontaining theredundant windings andofthediscrotor.Thedeviceismechanically overworked byDSSinordertomakesurethat allsizesandtolerances areaccording tothespecified values. Themotoristhenequipped withdry lubricated bearings (RMB)andtheaxialbacklash isadjusted tozerobymeansofPTFEwashers, which alsocompensate fortheaxialthermal mismatch between thetwobearings seatsandtherotorshaft.A stepper motorofthesametypewasalready qualified anddelivered toARTEMIS. Themostimportant motorcharacteristics arelistedinTable8,andacross-sectional viewofthemotorisshowninFigure4. Table8:Characteristics of Characteristics DiscRotorMol Motormass Winding Resistance Windings Phases Cogging Torque Holding Torque Natural Step PhaseCurrentStepper Motor Value 12.10.0kg_mL 0.26Okg 12_ Redundant 14mN-m 174mN-m 3.6de9 0.56A 293
/= IVVas.erIRotorBearing andBearing ..._....q_t  FStator--_a nd_Winding--_-s __--_F (Redundant)  IStatorandWindings :_'_ _1(main) JRotorShaft I Figure 4:MotorConfiguration GearUnit Thegearunitattached tothemotorisaplanetary gearfromGysin(GPL32-S)anditscharacteristics are listedinTable9.Thegearislubricated withBray601.Inordertodealwiththelowtemperature environment, itsoutersurface isequipped witharedundant heater, athermistor, andmultilayer insulation sothatthegearunitcanbeheated uptooperational temperatures ifitshouldcooldowntounacceptable values(lowerthan-50°C) duringtheexpected tongnon-operation phases. Theoperational low temperature limitisdefined bythepourpointofthelubricant. Table9:GearUnitCharacteristics Characteristics Ratio Mass Size Lubrication BacklashValue 1:32 0.180rkg L=61mm,O32mm Bray601 0.003rad _Spindle Unit TheSpindle Unitisconnected viaaflexible metallic coupling tothemotor/gearunitandcomprises a bearing unit,whichsupports aplanetary rollerscrew(Rollvis). Spindle unitcharacteristics arelistedin Table10.Thescrewnutisbearedinalinearguidance bushing andcarriesthespherical actuator output I/F.Thespindle islubricated withBray601andthenutispreloaded inordertoavoidbacklash. Table10:Spindle UnitCharacteristics ICharactenshcs Value Type Pitch Diameter Lubricant Mass PreloadPlanetary RollerScrew 1mm 8mm Bray601 O.O98k9 60N Monitorin.q Switches Eachactuator isequipped withasetof4monitoring switches, twoateachendoftheworking stroke. Twoswitches arenominally usedtocalibrate thezeroposition oftheactuator; theotherpairisfor redundancy andtoswitchofftheelectronics incasethatoneswitchshouldfail.Theswitches are 294
normallyclosedandopenifapproached bythespindle I/F.Theyareindustrially procured (Baumer) and werequalified fortheMSG/SEVIRI Project. TheSwitches provide aswitching accuracy intheIJmrange andareadapted tospaceconditions byintegrating aspaceprovenharness. Theswitches characteristics arelistedinTable11. Table11:Precision Switch Characteristics Characteristics Value Mass Size Switching AccuracyO.O03kg O8mm,I=20mm +_1pm(ambient) Electronics TheAPMiscontrolled bydedicated electronics consisting oftwocoldredundant drivers, oneofthem interfacing themainwindings oftheAPMactuators, theothertheredundant ones. Electrical I/FandElectronics TheAPMelectrical I/Fisrealized byasetofCannon connectors attached totheAPMBaseBracket. The APMControl Electronics hasamassofabout1.9kg,atadimension of160x160x65 mm.Thepower dissipation isabout2.2Wandaprimary voltage of24upto52Vcanbehandled. TheElectronics isable todrivethemotorinmicrostepping mode.Thecommand anddataI/FisaserialR422I/Foroptionally a MACSBusI/F. Rx/TxSignalandPowerTransmission Flexible Wave.guides Thesignalreceived andrespectively transmitted bytheantenna intheKa-orKu-bandisguidedfromthe moving antenna downtothesatellite I/FbymeansofFlexible Waveguides. Inthebaseline design, the Flexguides areroutedfromtheSatellite I/Fthrough thecenteroftheAPMuptotheAntenna I/F.The Flexguides areofthetypesWR34andWR51fortheKabandreceivers andtransmitters, andincaseof aKu-band application, theaccommodation ofWR75Flexguides isforeseen. Sincethethermal analysis hasshownthatatransmission powerofsomehundred wattsaspotentially required forfutureapplications wouldcauseFlexguide temperatures intherangeof300°C, aspecial routingwasidentified alongthesideoftheAPMforthisapplication caseinordertoallowheatdissipation tocoldspaceandnottoproduce hotspotsandhighgradients inthemechanism itself.Thecorrugated Flexguides aremanufactured outofBeCu,aresilvercoated, andpainted blackwithahightemperature Silicone Paint. HRM ThetwoHolddown andRelease Mechanisms whichformtogether withtheAPManisostatic threepoint support fortheantenna duringlaunch, aredesigned aspyrotechnic release units(ME038AA055).The chosen designisderived fromtheLOCSTAR Antenna HRM.Inordertoachieve theSISeigenfrequency requirement of50Hzatanantenna massof24kgandanMolof15kg-m2,release boltsM10are included intothedesign. Figure5showsthelayoutoftheHRM. 295
I [Bracke_ Figure5:HRMConfiguration Development Status AnAPMQualification Modelincluding Flexible Waveguides wasbuiltandtested.Testsperformed are: •Functional Performance •Vibration •TV •Life •EMC •Functional Performance •Duringfunctional performance testing, pointing accuracies andreproducibility ofthecommanded antenna I/Fpositions wereverified. •Vibration wasperformed together withtheHRMsandwithadummy massof24kgontopofthe APM,simulating theworst-case antenna configuration. •TheTVqualification temperature was-110to+107°C. Duringtest,thefunction oftheAPMandits performance wasmeasured bymeansofaLDDM(LaserDoppler Displacement Meter). •AfterTVtesting, alifetestwith90,000 random slewsatahalfcone angleof10degwasperformed. •AnEMCtest(together withthecontrolelectronics) wasperformed andthetestprogram was completed byafinalfunctional performance testcardedthrough inordertodetectpotential degradations ofthemechanism overthewholetestsequence. Te._tResults oftheFunctional Test Thefunctional testswereperformed ona3Dmeasuring facilityfromLeitz.Therepeatability errorofthe machine (assuming thedimensions relevant fortheAPMmeasurements) iswithin0.5mdeg. Inafirst teststep,theAPMwasadjusted onthemeasuring facilityandthecross-coupling effectbetween thetwo (baseandframe)axeswasmeasured. Crosscoupling meanstheangular shiftoftheframeaxisifthe baseaxisiscommanded andviceversa.Nomeasurable effectcouldbedetected ontheframeaxisifthe baseaxiswasrotated. Byrotation oftheframeaxis,acrosscoupling effectofabout+5mdegwasfound onthebaseaxis.Sincethiseffectisrepeatable, itcanbecompensated byintroducing anoffsetinthe axislinearity deviation curves(nonlinearity curves) takenfortheidentification oftheangular antenna IlF position asfunction ofthecommanded actuator steps.Arbitrary anglesofthecommand I/Fcouldbe recovered withanaccuracy ofbetween 0and1mdegifthetargetangleisalwaysapproached fromthe 296
samedirection. Similarresultsareobtained ifarequired angularvalueiscommanded byusingthenonlinearitycurve(antenna targetangleasfunction ofmotorsteps).Table12summarizes thefunctional test results,andtheAPMduringfunctional testisshowninFigure6. Table12:Functional Performance TestResults TestPerformed RestResult Comments AngleofMotion VelocityofMotion Position Reproduction Error Position Errorofthepreadjusted position afterRelease fromLaunchPosition Position ErrorafterRelease fromLaunchPosition andactive Position Recovery bymeansof Actuator20.5degonBaseAxis 20.6degonFrameAxis 5.45.deg/min 0to1mdeg mdegto57mdeg About2mdegdepending onlimitswitch ...a...djustment J.... overall15arbitrary positions werecommanded 5testswithantenna inertia simulator performed atdifferent targetpositions actuator moved100stepsforth andbackafterreleasefrom launchposition Figure6:APMduringFunctional Performance Test Vibration T_t Thevibration testconfiguration consists oftheAPMandofthetwoHRMsattached tothevibration test adapter. Inordertosimulate theloadsappliedtotheAPMbytheantenna structure, adummymassof24 kgwasmounted tothetopoftheAPMandthetwoHRMI/Fpoints.Lateralinplaneloads(Y_Y)are transferred bytheAPMandtheHRMs,whileaxialoutofplane(Z)loadsarefullytransferred viatheAPM. Sinequalification testlevelsof12to15ginplaneand6to30goutofplanewereappliedupto100Hz. Random qualification wasperformed at17grmsinplaneand20.5grmsoutofplane.Asketchofthetest setupandaxisdefinition isshowninFigure7.Thefirsteigenfrequencies oftheAPMwereabout160Hz inplaneandabout160Hzoutofplanewiththedummymassof24kgontopoftheAPM.Inplane,the HRMsarepartiallysupporting theAPMwhiletheZ-(outofplane)loadsarefullyovertaken bythe mechanism. 297
Thevibration testwasperformed without degradation ormalfunction oftheH/W,theonlyminorNCR established wasrelatedtoadamper unit,whichgotlooseduringtestduetoinsufficient securing. The threadwasrefixedandthetestwascontinued nominally. Adequate designmeasures tosecurethe dampers werethenincluded intotheAPMdesign. IM_ssD.J,rm_/I $ Z.  / I -x/ iVibratiol TestAdapterl Figure7:Vibration TestSetup /'\ 0 20 40 60 80 100 1_0 1800 -2 -2._= =3 .3._= .,4 -4,_=\J_ __ 1 1 I / / .._._f-----' 40 80 80 100 t20 140....180 180 -- 0 ..4 0 20 40 60 80 100 120 t40 I6_ _0\ -\G20 40 80 B0 100 t_0 140 180 180 RUNA RUNB Figure 8:APMReproducibility Measurement Results atdifferent Temperature Levels 298
Table13:Overview overachieved W-Test Results Temperature Reproducibility It[°c] RunA[deg] RunB[deg] 50 0,00039 4,29.10"= 60 0,00028 0,00027 70 0,00074 0,00060 80 0,00020 0,00090 90 0,00171 0,00027 100 0,00495 0,00663 -80 0,00031 0,00126 102 0,00469 0,00597 105 0,00781 0,00061 -100 0,02550 0,02144 -106 S/Werror 0,00227 102 0,00050 0,00173 -95 0,00104 0,00013 TVTest TheTVtestwasperformed ataqualification temperature rangeofbetween -110to+107°C. Overall 5 cycleswereperformed; thefirsttemperature cyclewasdedicated tothesearchofapotential functional limitation ofthemechanism. Forthispurpose, afunctional check(detection oftheactuator limitswitches function andmotionofthegimbalframe,aswellasaperformance check)wascarriedthrough atdifferent temperature levels. Theperformance checksweredonebymeansofaLaserDoppler Displacement Meter(LDDM) arranged outside theTVchamber. Aretroreflector attached tothegimbalbaseaxis reflected thelaserbeam.Thereceived signalwasdirectly relatedtothetiltangleoftheAPMAntenna I/F.Someresultsofthereproducibility measurements performed duringTVtestingareshowninthe Figure8.Table13 depicts asummary ofthemeasured reproducibility valuesforthetemperatures during runA(positive angles) andrunB(negative angles). TheAPMpassed thervtestsuccessfully, however, duringtestingthefollowing issueshadtobesolved. Duringthefirstcoldcycle,thelasersignalusedforperformance measurement gotfaintatabout-80°C anditwasobserved thatparticles hadcondensed onthecoldopticalsurface oftheretro-reflector attached totheAPMbaseaxis.Theproblem couldbesolvedbyapplying asmallheatertotheretroreflector housing sothatitstemperature couldbestabilized totemperatures above0°C. Despite thefactthattheAPMwasmounted underneath anadditional thermal shroud, itwasverydifficult toachieve well-balanced temperature extremes atallrelevant APMpartswithinareasonable working time.Themainreasons forthisbehavior isthattheAPMBaseBracket isdirectly connected toacold plate,whiletheGimbal Bracket iscoupled totheenvironment mainlybyradiation. Basedonthisfact,a significant thermal gradient wasbuiltupduringheating upandcooling downprocess overthegimbal bearings. Inordertoachieve performance measurements intheextreme temperature withinalimitedTV testingtime,thesemeasurements hadpartially tobeperformed atuncompleted temperature stabilization ofallrelevant APMparts,i.e.,thatgradients werestillobserved intheAPMduringmeasurements. One oftheperformance measurements wasperformed inthecoldcaseatthebeginning oftheheatupphase. Thismeasurement yielded decreased performance valuesduetoextreme thermal gradients intherange ofAT=50°C,occurring between theAPMBaseBracket andtheFrameBracket (overthegimbal bearings). Theseextreme gradients ledtoanincrease offrictioninthegimbalbearings, which jeopardized theAPMperformance byincreased elasticeffectsinthebearings. Figure9summarizes the performance measurement resultsunderTVconditions. Theworstcasereproducibility valuesof0.026 and0.021degarerelatedtothehighoccurring gradient discussed above. 299
R e p r o d U C i b.Reproducibility Antenna Pointing Mechanism 0,03 0,025 0,02 0,015 0,01 0,005 0 -150m.E Requirement: 0,01deg Specified temperature m range = •. o! ;_-;_;, ;........ ...... -100 -50 0 50 100 150 Average Temperature [°C] Figure9:Summary ofReproducibility Measurements AfterTVtesting,asubsequent lifetestwith90000randomrepositioning slewswassuccessfully performed ontheAPMwithout degradation (verified inafinalperformance check). Therandomslews covered ahalf-cone angleof10degwithaminimum angleofabout0.175deg.perslew. 12000 _........... , I O --L.... _..... D NO0 4L_O BrJO0 B(]O0 _ODC_ 1,3DOO Figure10:LifeTestRandom SlewDistribution 3O0
Summary andConclusions Atthebeginning ofthedevelopment phase,anenvelope specification wasestablished inordertoallow theapplication ofthemechanism toavarietyofapplications. Theoperational qualification temperature of theAPMwasdefined to-40to+60°Candthedesignofthemechanism wasbasedonthistemperature regime. Thethermal analysis performed atthesystem levelandlaterontheAPMlevelunderconsideration ofa chosen reference Satellite Platform andofarepresentative orbityielded forsomemission casesamuch moreseverethermal environment thanspecified. Therefore thegoalwassettoachieve theextreme qualification temperature rangeof-110 to+107°C withtheexisting designatminimum designchanges. Inordertoadapttothenewtemperature regime, notonlythelubrication concept ofthegimbalbearings hadtobechanged fromliquidtosolidlubricant, butalsothebearing concept hadtobechanged from hybridto440Cbearings inordertonotdamage thehardpreloaded bearing pairsatlowtemperatures duetotheoccurring thermal mismatch atmaximum occurring temperature changes of130°C?T(change from+20to-110°C). Furthermore, thebearing housing material, whichwasintended tobestandard Aluminium before, hadtobereconsidered inthiscontext sincethestresses inthealuminium housing and thesubsequent deflections induced intotheouterbearing ringwereunacceptable high.Theonlywayto solvetheproblem wasfoundinusingaspecialAI-Sialloy(DISPAL S225)providing aCTElikesteelat thespecific weightofstandard Aluminium. Bymanufacturing thebearing housings outofthisalloy,an almostperfectmatchbetween therotating steelgimbalshaft,thedrylubricated steelbearing, andthe bearing housing couldbeachieved. Thematerial performed wellwithout anyproblem overthecomplete APMqualification cycle.DuetoitsCTEcharacteristics, thealloyisfoundtobeanidealmaterial tobe matched withballbearings orothersteelparts.Sincethematerial isactually notwidelyusedinspace applications, theavailable material database isactually notonthesamelevelasforstandard space materials. Therefore itmightbenecessary tocarrythrough project-specific material testsinorderto qualifythematerial foraspecific application. Inaddition tothegimbalbearing issue,theactuator concept hadtobereconsidered withrespect tothe temperature problem. Theactuators arelubricated withBray601andaconfidence testhasshownthat theactuation temperature waslimitedtoabout-60degduetotheincreasing viscosity ofthegrease in thistemperature range. Sinceitwasnotacceptable tochange thechosen lubrication concept ofthegear duetolifetime reasons, itwasdecided toapplyathermistor andadedicated redundant heatermattothe planetary gearsurface oftheactuator inordertoallowheating uptooperational temperatures inthecold case. Theoverall APMperformance wasmuchbetterthanspecified, eveninthelowandhightemperature regime, however, itwasfoundthatsignificant gradients overthegimbal bearings strongly influence the performance. Thisisduetoelasticeffectscaused inthebearings attheincreased frictiontorquerelated tooperational conditions athighgradients. 301
Testing Asafirsttestphase,priortoinitiation ofthebearing lifeteststations, separate material andlubrication tests wereperformed. Basedontheresultsofthosetests,thebestbearing material andlubricant wereselected earlyintheprogram. Asathirdphaseofthetestprogw:am, aftercompletion ofthequalification program, life testingbeganonthequalification mechanism. Bearing lifeteststationIIIwasinitiated aspartofthesecond testphase. Threeflightquality440Csteel, 66.675mm(2.625inch)outerdiameter, 50.800mm(2inch)innerdiameter, 165N(37pound)preload, DF duplexpairbearings wereusedinthetesting. Thebearings, phenolic laminate retainers andsintered nylon reservoirs werelubricated inaccordance withflightrequirements. Theteststationisillustrated asFigure1. Eachbearing pairwascontained initsownclamp/housing. Thehousings alsocontained lubdcation reservoirs. Eachhousing wasfittedwithinnerandouterraceheaters. Astraingaugewasmounted ona cantilever beamsupporting eachbearing enclosure tomeasure thetorque. Instantaneous torquereadings wererecorded every15minutes. Themonthly average ofthesereadings wasplottedoverthelifeofthetest (seeFigure2).Onetelemetry platinum resistance thermometer (PRT)wasmounted toeachbearing outer racehousing fortemperature measurement. TwocontrolPRTswerealsomounted toeachbeadng housing (oneontheouterraceandonefortheinnerrace).Alltestingwasperformed undervacuum. Ferrofluidic rotGtory feedf.hrough assy. Figure1-TestStation 304
TestData Torquevaluesoverthecomplete testarepresented inFigure2. MODISBEARING SCREENING TESTI STATION #3 0.10 0.09 0.08 _0.07 Zv0.06 80.05 0.04 _-0.03 0.02 0.01 0.00 0102030405060708090100110120130140 Cumulative Cycles(Millions) Figure2-Torque vs.Revolutions forUpperPairBearings (1111), Middle Bearlngs (1112)andLowerBearings (1113) Atabout88millioncycles,aslightriseinindicated testtemperature occurred. Theindicated temperature of allthreebearing pairsrosetoapproximately 48°C(118°F) [thenominal temperature was37°C(99°F)]. It wasnotuntilthestationwasdisassembled thatdelamination ofthetelemetry PRTswasobserved, Analyses showed thatthePRTswerefunctional, butthebondareasjoiningthetelemetry PRTstotheouter racetestfixtures werefractured. BondareasforthecontrolPRTsremained intact.ThecontrolPRTswere approximately 2-mmwideand5-mmlongwhilethetelemetry PRTswere3-mmwideand12-mmlong.The fractures mayhaveresulted inlowerindicated temperatures thantheactualbearing temperatures. A corresponding dropintorquewasobserved atthistime.Thetorquecharacterization plotsindicated significantly lowervalues(approximately 1/4oftheprevious values)fortheupperandlowerbearing pairsand aslightlylowervalueforthemiddlebearing pair.Thedropintorquewaslikelyduetoadropinlubricant viscosity andadropinbearing preload asthealuminum housing expanded morethanthesteelbearings. Thiscontinued forapproximately 4weeksatwhichtimetheheaters weredisabled. Thetorquevalues returned toalevelslightlyabove(approximately 1/3higherthan)thatpriortothetemperature excursion. Theriseintorquelikelyresulted fromanincrease inlubricant viscosity andariseinbearing preload. The testcontinued without heaters untiltheconclusion. Atapproximately 60millionrevolutions, thetorquecharacteristic plotsshowed considerable fluctuation due tojitterforallthreebearing pairs.Thecumulative trenddatadidnotindicate thissincedataisaveraged in thecumulative trendplot.Theteststationspeedwasincreased to60RPMandthejitterceased. Thetest wascontinued at60RPM. Higherthannormaltorquereadings wereobserved atapproximately 95millioncyclesforthelowerbearing pairandatapproximately 120millioncyclesfortheupperbearing pair.Asthehighertorquereadings were 305
stillwithinscanmechanism operating parameters, thetestwascontinued. Ineachcasethetorque readings subsequently decreased belowthenormallevel. Testingwasperformed foratotalof144,263,692 revolutions or2.5specified mechanism lives.Torque characteristic plotswereprepared monthly byMoogSMDandsubmitted toRaytheon SBRS.Figure3 presents atypicalcharacterization plot.Torqueshownonthecharacteristic plotscorresponded tothe average torquevaluespresented inthecumulative trenddata. ® E0 I--0.15 0.12 0.09 0.06 0.03 0.00TORQUE CHARACTERISTICS IGAUGE1112 I ,,il a a l l • I | l I | l 012345678910111213 Revolutions 0.15 0.12 ,E0.09z =_0.06EO 0.03 .0.00ITORQUE CHARACTERISTICS IGAUGE1113 I I 012345678910111213 Revolutions Figure3-TorqueCharacterization (Notethelowertorqueandjitterpresentinthelowerbearingpair,gauge1113.Thisoccurred afterthetorque spikesseenatapproximately 120millionrevolutions inFigure2.) 306