ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
12VBattery I iLinear IPotentiometerI PitchRateSensor RollRateSensor YawRateSensor Separation Connector Opto-isolator _1_ I IDetensioner PowerSupplyir y LabVIEWServerDatabase Test Test Assy Number Director Number 5RLP 4000340 6RLP 4000340 7RLP 4000340 8RLP 4000340 Figure16.Separation Reliability System BlockDiagram Separation Reliability TestResults Turnaround timebetween successive testswaseventually trimmed totenminutes, resulting intheability toperform largenumbers oftestswithinarelatively shorttimeframe. Thisgreatlyreduced thecost-per-test andguaranteed arobustseparation reliability testing regimen fortheLightband units.Thesefactors allowed astatistically significant number ofseparation reliability teststobeperformed foreachLightband. TheLightband usedforthesuccessful Starshine-3 mission wastestedover50timesontheseparation reliability fixtureoverthecourseofamonth.Theentiretestprocedure canbeperformed byonetechnician working alone,freeing upengineers forotherwork.Figure 17shows theStarshine-3 satellite and Lightband inpreparation forlaunch. DatafromthetestswerereadintoaLabVIEW program andoutputintoacomprehensive database. The information wasthenscrutinized tocharacterize theLightband andpredicton-orbit performance. Asample ofthedatacollected fromtheLightband usedfortheStarshine-3 mission isincluded inTable2. Maximum, minimum, average values, andstandard deviations werecalculated foreachofthemeasured characteristics, andwereusedtomakeadjustments tomeetseparation requirements andpredicton-orbit performance. Analytical predictions ofsystem dynamics differed considerably fromtestdata.Thisisbecause lossesin separation energyandangular momentum duetofrictionandotherfactorswerefoundtobesubstantial. Without thetestdataitwouldhavebeenimpossible toaccurately characterize theperformance ofthe Starshine-3 Lightband. Therefore, relyingonanalytical means aloneforpredicting on-orbit performance wouldhaveresulted inanunderestimation ofthespringenergy necessary toproduce therequired separation velocity andangular rollrateforStarshine-3. NASA/CP--2002-211506 288
TheLightbandforStarshine-3 (shownbeingmatedto LMA'sAthena)successfully spunuptheStarshine3 spacevehicle.On-orbitspinratecloselymatchedabove testdata. Figure17.TheLightband forStarshine-3 Table2.Sample DataSetForStarshine 3Lightband OnOrbitPerformance Prediction I RollRate[deg/sec] Velocity [cm/sec] Lightband 001 5.976 15.246 Lightband 002 5.257 14.804 IRequired Rate 5 (+/-1.00) 15.24 (+/-TBD) 26inchStarshine 3Lightband SerialNumber 001 Test Number of Initial Pitch Roll Yaw Velocity Timeto Separate Number SpringAssemblies Tension [N][deg/sec] [deg/sec] [deg/sec] [cm/sec] [sec] 41 10 1779 0.211 6.228 0.206 16.492 14.5 42 10 1655 0.252 5.525 -0.446 13.459 15.44 43 10 1632 -0.567 6.151 0.059 15.245 19.89 45 10 1846 0.178 5.372 0.126 14.000 18.02 46 10 1753 -0.067 6.222 -0.059 16.627 18.4 47 10 1779 -0.266 6.129 0.208 15.250 18.51 48 10 1721 -0.427 5.894 0.155 15.984 17.35 49 10 1779 -0.199 6.002 0.198 14.920 17.09 50 10 1761 -0.079 6.258 -0.22 15.237 16.26 Average 1745 -0.107 5.976 0.025 15.246 17.27 Maximum 1846 0.252 6.258 0.208 16.627 19.89 Minimum 1632 -0.567 5.372 -0.446 13.459 14.50 Standard Deviation 67 0.288 0.323 0.227 1.052 1.67 Actualon-orbit spinfortheStarshine-3 satellite wasmeasured tobe4.4degrees persecond, wellwithin therangeofacceptable spinvalues(5degrees persecond [+/-1degree]). Itisalsolowerthantheaverage spinvaluederived fromseparation reliability tests(5.257degrees persecond) fortheLightband usedfor flight.Thisdiscrepancy mayhavebeencaused byatmospheric differences between separation reliability testingconditions andlaunchconditions. Though thelubricating qualityoftheatmosphere allowstheair bearings toproduce africtionless environment inwhichtotest,thissamequality mayalsoimpact NASA/CP--2002-211506 289
separationmotioninawaythatisabsentinavacuum.Theseparationreliabilityfixturecannotbeusedin avacuuminitscurrentconfiguration, andthislimitationshouldbeacknowledged inthedesignoffuture testfixtures. Discussion ofLessons Learned Therewerenumerous lessons learned intheprocess ofdeveloping theautomated testprocedure. Theyinclude: •Analytical means aloneareinsufficient toaccurately predict on-orbit performance ordetermine standard deviation. Variations inperformance andhiddenlossesmakerepeated andthorough testing theonlysuremethod ofpredicting on-orbit performance. •Massproperties ofthesatellite mock-up shouldbematched verycloselytothesatellite tobeflown. Equivalent massproperties allowamoreaccurate simulation ofactualconditions thancalculated results basedontheprinciple ofconservation ofangular momentum. •Ratesensor calibration isanessential partofthetestingprocedure, andquickandwell-understood calibration methods areusefultomakethisnecessary taskuncomplicated. •12-voltbatteries arearelatively noise-free powersourcefordrivinginstruments likeratesensors, but itisessential tocontinually checkontheirstateofcharge aslowbatteries maycausethesensors to produce falseandmisleading signals. •Sensor signalwiresmustbethinenough toreducetestinterference caused bytorques fromdangling wiresmounted ontheseparating armofthetestfixture,andthickenough toprevent excessive signal noiseandfragility caused byverylightandthinwires.Slightly thickerwire(26-28AWG)willbeusedfor futuretests. •Basicprogramming principles ofgooddocumentation andeasy-to-debug codehaverealvalue. Debugging software canbecome asubstantial drainontimeandproductivity andshouldbemadeas easyaspossible through well-organized andwell-documented sourcecode. Thestatus oftheautomated separation reliability testprocedure isfunctional, though valuable improvements abound. TheLabVIEW codecanbeimproved upon,airpressure fortheairbearings shouldbeautomatically regulated, andtheinstrument wiringshouldberepositioned onthetestset-upand generally streamlined tominimize impactandbreakage. Athorough reassessment ofthetestfixtureis underway, andpossible changes include suspending theentiretestunittoallowseparation reliability testinginavacuum andanadditional degree offreedom inthevertical axis. Conclusion Theautomated separation reliability testfixtureisavaluable newtool.Itconfirms separation, monitors and records rotational andtranslational separation rates,eliminates gravitational forcesandtorques, and allowsasignificant number ofteststobeperformed asaresultofitsshortturnaround timeandeaseof use.Thisthorough verification ofamission criticaleventislacking intraditional methods ofdetermining separation reliability. Theautomated separation reliability testfixturehasbeenusedsuccessfully for multiple Lightband separation systems, andwasusedtodetermine thespringconfiguration necessary to produce therequired on-orbit spin-up ratefortheStarshine-3 mission. NASA/CP--2002-211506 290
Repelling Magnets "A.rac,ing o,agcnetMairI,Bearing Floating Bea_ Magnets Figure 1"Mechanism Operation SchematicsTelemetry/Command _l_Jjlnterface PCB / Actuator StatorCore Rotating Package Floating Bearing Axial-Stroke Adjusting Shim MainBearing & SnapRingX Y Figure 2"Cross-Section Through theHighPower T-Switch Description OfTheSupported Packaqe Therotating package (Figure 3)isatemperature compensated bearing system withrotating massof 42x10-3kg.Thepermanent motor-magnet isaxially offsetoutside thesurrounding statorcoretocreate a netaxialmagnetic forceofrequired intensity, preloading themainbearing against thesnap-ring. The magnetic axialforceisproportional totheoffset. Thiswaythepre-load ofthebearing isbasically constant during operation (thesamarium cobalt permanent magnets, usedfortherotor,areverystableoverallthe usefultemperature range). Thedirection oftheaxialbearing load(forthemainbearing) isalways fromthe snap-ring toward thetrailerbearing (reaction ofthesnap-ring). Intheopposite direction onlytheinertia (verysmall) oftheballsandouter-race ofthemainbearing act.Thefloating (trailer) Conrad bearing hasa sliding fitinsidethehousing, whicheliminates theaxialstresses duetomismatched CTE's between the shaftmaterial andthebearing. Thisdesign solution avoids anyaxialstresses duetotemperature andalso maintains constant bearing pre-load. NASA/C P--2002-211506 292
MainBearing Floating Bearing I / Crown Retainer Figure3.Rotating Package &Bearings Figure4.Exploded ViewoftheMainBearing Themaximum possible axialmotionofthemobilepackage isadjusted usingaxialstrokeadjusting shims interposed between thetrailerbearing anditsshoulder inthehousing. Themainbearing isaminiature Conrad thin-section ballbearing withanouter-diameter of33.3375 mm, (1.3125 in),aboreof26.9875 mm,(1.0625 in)andwidthof3.96748 mm(0.1562 in).Thebearing usesa one-piece phenolic crownball-retainer ridingtheoutside race(Figure 4)and14balls.Thismainbearing is situated nearthecenterofmassfacingthesnap-ring withoneshield(opposite sidetotheretainer). Description OfTheMountin.q Panels T-Switches aremainlyusedinredundancy ringapplications. Inacommunications payload havingmultiple transponders, theswitchringpermits replacing anyofasetofchannels withonefromasmaller setof sparesignalpaths.Figure1showsthethreeswitchstate(A,B,andC)andasimpleredundancy ring havingtwosparesforsixchannels. 2 PosA3 4I.U 4PosC / PosBJjJ"_/ff Figure5.Switch Positions andRedundancy Application Telecommunications payloads trendtoward increasing sizeandcomplexity. Asavailable mounting real estatebecomes scarce, sub-panels raisedonbrackets (mezzanine structures) areincreasingly used.In turn,copingwithlaunchvibration becomes increasingly challenging. Inthepresent case,multiple RFTSwitches plusadditional equipment aremounted onraisedaluminum honeycomb flatpanelstructures. Figures 6showsatypicalconfiguration ofsuchapanel.Theswitches (asaredundancy ring)arealongthe nearedgeofthepanel.Bothfacesofthepanelaresimilarly populated. Figures 7and8showthe corresponding modalanalysis ofthewholestructure. Thesignificant natural frequencies andmode shapes forvibration oftheequipment 1contain amajormodeat100Hzandthreeoffourpanelshavea secondary modenear600Hz. 1Analysis doneforfrequencies upto2000HzusingPro/Mechanica Structure modalanalysis basedon Lanczos method ofeigenvalue extraction. NASA/C P--2002-211506 293
,i! Figure6.PanelLayout n Figure7.PanelMajor ModeZ-Axes Figure8.Panel Secondary Mode590Hz Description oftheTestReqime Themajormode(forallaxes)onallhoneycomb panels (around 100Hz)coincides withthenatural frequency ofthefree-body motion oftheelectrical contacts. Duetoconcerns overpotential fretting of electric contacts duringvibration, special vibration screening testsweredevised toproveunitspriorto integration. Testing wasperformed onaspringboard fixturedesigned toreplicate theenvelope of worst-case transmissions ofthefourraisedpanelstructures inuse.Thespringboard wastherefore tuned toachieve twopeaks(around 100Hzand600Hz).Figure9showsthecomputed desired springboard outputforout-of-plane axis2(Z-axis) andfigure10showsatypicalmeasured response asinputintothe switches undertest.Similar approaches wereusedtodefinetestsinthetwoin-plane axes.During vibration testtherotarypackage wasmagnetically latched inoneofitsstandard positions andafter vibration ineachaxistheposition wasverified electrically. 2Coordinate System showninFigure6. NASA/CP--2002-211506 294
100.0 10.0 1.0 0.1 0.01 0.001I I PSD [g2/Hz] /J fJ /A / I •f1L/ Y Overall46.5grms rllllI1(o Frequency [Hz]/L 1(_002000 Figure9.Umbrella Switch Vibration Spec Out-of-Plane10.0I PSD 0.1 0.0 i Frequency [Hz] Figure10.Resonant Fixture Response Bearing Failure History InitialFault Asthespecial springboard testsprogressed, threeswitches failedtoactuate afterexposure. Thefailure occurred, eachtime,afterrandom vibration intheout-of-plane axis(Z).Disassembly ofaffected switches revealed thatthemainbearing hadseparated leaving therotating loadunsupported withattendant damage tosurrounding parts.Allferrous partswereheavilyencrusted withchipsofsamarium cobaltfrom theactuator rotormagnet. Ballsweredistributed throughout thepackage andtypically werefoundclinging tothemagnetic materials oftheactuator. Allballswerefoundandnoneappeared significantly deformed. Bothracesexperienced substantial impact damage inthegrooves, however, thedamage was concentrated atthelips.Littlemarking wasnotedintheballtracking region.Mostoftheracedamage was therefore attributed tohammering aftersomeinitialfault.Theretainers werefoundontheshaftbehindthe bearing planeandshowed noovertsignofdamage. Figure11showsthecondition ofafailedbearing. Figure11.Damaged bearing Subsequent Faults Additional monitoring andfunctional checks wereaddedtothevibration testsequence topermitearly detection ofthefault.Aftertestresumption, twoadditional unitsshowed anomalies. TheseunitswereXrayedandbearing faultsconfirmed. Figure12showsX-rayphotographs ofanormal assembly (Figure 12a)andoneafterfaultdetection (Figure 12b).Inthefaulted case,allballsareconcentrated inanarc segment ononesideofthebearing. Although notapparent inthereproduced X-rayimage,thecrown retainer isdiscernible asbeingfullyremoved fromthebearing assembly. Thesetwounitsdidnotincur extended faultpropagation damage andaccurately represented thepartcondition atthetimeoffault. Races,balls,andretainer wereinpristine condition (seeFigure13). NASA/C P--2002-211506 295
02/20/2001 1355 Figure 12:Normal Bearing (a)02/19/2001 094143 St4090008_ Bearing AfterVibration (b) BearingInnerRace Figure13.Faulted bearing Withnopropagation damage Itisclearthatthefaultinitiates withthedisassembly ofthebearing inreverse sequence ofthenormal bearing assembly process. AsitmaybeseeninFigure14,thefailuremechanism consists ofthefollowing threesteps: 1.Thebearing ball-retainer isejected outofthebearing duetovibration. 2.Theballsaretherefore freetomoveandaccumulate ononesideoftherace. 3.Thebearing disassembles duetothefreeplaycreated. START Figure14.Bearing Failure Mechanism Theinvestigation intothecauses ofthisfailuredealtwiththefollowing questions: 1.Isthisfailurerelatedtotheparticular batchofbearings? 2.Isthedesignoftheball-retainer unsatisfactory? 3.Didthevibration-induced loadsonthebearing justifythefailure,andfurther, isthefreebody resonance oftherotating package afactor? NASA/CP--2002-211506 296
Basedonawell-known resultwhendealingwithSDOFsystemstheresponseofthehousingisalmost equalwiththebaseinputforlowfrequencies 3(aroundthenaturalfrequencyofthemobilepackage)andis independent ofthehousingmountinginterfacedamping.ThereforetheinputforSDOFmass-system can beapproximated bytheprofilesinFigures8and9.FortheresponsetoZ,YandX-axisvibrationsthe couplingsteady-state transmissibility functionwasdetermined basedonexperimental data.Aspecialtest wasdoneusingaconstantPSDrandomvibrationlevel(0.1g2/Hz)inZ,Y,andX-axesandtheresponse acceleration wasmeasured directlyonthemobilepackageinX-axis.Thecouplingsteady-state transmissibility functionisgivenby[1],[2]: T_,(.f)=IPSDx(.f) PSDz(_)I IPSDx(f)PSD,.(f) PSD,_,,(f) PSD,.,,(f)(I) Thethreecoupling steady-state transmissibility functions arepresented 4inFigure15andthevibration response spectrum ofSDOF-system inFigure16fortheinputonZ-axis. Similar functions werederived forXandYaxisinputs. 10.00 1.00 0.10 0.01...... ___.,_4 .;.-::_; _ .... . [Gout/Gin] _:1 iii-i-___ :Tzx I*t }.l_l_=T-i-M , •!1IIIII/._IIKlbli,j iTyx ,iii_, !_-_!-/]g "'_. -xx--t--t--r"T-1-;- -- _--_ i = Ii!!!!!: !!I!1Ii,,,,_I,.r_FI'tlq_ !!I III....I_LL':.___,,J'__I_!I _ [IiI; __JI [I!1_,,', I IiI]1 [ iIlill III'.111 i!_.!i,Z'_LI 1_ ;i_r ;]i[i[i --i_-i-i- 'jiliiii iilllll r--I'171iii]ifiii*,iiiii] 10 100 1000 10,000 Frequency [Hz] Figure15.Coupling Steady-State Transmissibility Function10iPSDilii,;;;l-i-f-tl........... i..... iiiliTit , :tl 0.00001; _III;!!il i,i ........................ 10 1O0 1000 10,000 Frequency [Hz] Figure16.AxialResponse of Mobile Package inFree-Body Motion Table1presents therandom vibration induced axialforcescalculated usingthepeakaccelerations (3G) corresponding totheoverallgrmsresponses fromfigure16.Ascanbeseen,allpeakforcesarehigher thanthemagnetic-spring pre-load andasaresultthemainbearing willunloadandthenwillimpactonthe returnstroke. Theimpactforcescanbecalculated usingasimplified method basedontheassumption thattheshockduration isnegligible whencompared withtheperiodofoscillation oftheelasticbodies. Withthisassumption, theimpactforceiscalculated asfollows[4]: 3Atleastoneoctavelowerthanthenaturalfrequency ofthehousing [3]. 4Foraconstant bandwidth of4Hz. NASA/CP--2002-211506 298
F,,,,,,,,=_V"F_=1+_[I+--W_.,E"(2) Where: F=vibration induced force;'+'=dynamic impact coefficient; E0=kinetic energy ofthemobile package; WsT=deformation energyofthesnap-ring considering thatFisstaticapplied. Integrating thePSDresponses ofthethreeaxesyieldsoverallfree-body displacement responses (3_)of 0.2050034 mmforonZ-axisinput,0.2393188 mmforY-axis, and3.7084 mmforX-axisinput.Allthese valuesarelargerthanthemaximum axialstroke0.127mm.Thecalculation ofthedynamic impact coefficient istherefore adjusted usingthemaximum axialstroke. Considering KSRthestiffness ofthe snap-ring, fromequation (2)thedynamic impactcoefficient is: I2'K_.,•L_=1+ 1+' (3)F Where: L=themaximum axialstroke; Table1.Random Vibration Induced AxialForces ontheMainBearing InputAxis Vibration Induced PeakForce[N] Impact Force[N] X 67.27 397.2 Y 14.94 167.9 Z 21.71 206.5 Thestiffness ofthesnap-ring iscalculated [5]assuming theringissupported attheouteredgeundera uniform loadonaconcentric circular-ring ofradiuscorresponding tothemeanradiusofthemainbearing outerrace.Thecalculation ofKSRispresented intable2. Table2.KSRCalculation 5 i_ t[m] a[m] b[m] 0.256.350x10-41.739x10-2 1.515x10-2r0[m] D[N.m] T1[m/N] T2[m/N] 1.630xl0-2 4.547KSR[N/m] 4.006x1072.368x10-76.106x106 Therotation around thebearing axisdoesnotproduce anyloadonthebearing andwillnotbeanalyzed in detailhere.Itworthmentioned however thatthesesmalloscillations 6mighthelptheretainer ejection as pointed outinFailure Investigation section. Structural Response OfTheSupported Packaqe Table3presents themassproperties oftheHighRFPowerT-switch mobilepackage (seeFigure17for thecoordinate system). 5Inaccordance withsection B9of[5] 6Theydonotgobeyond theunstable equilibrium pointinthelatching torquecharacteristic. Thisisproved bythefactthattheswitchdoesnottogglepositions duringvibrations. NASA/CP--2002-211506 299
Table3.MassProperties oftheT-switch Mobile Package 7 Figure17.Coordinate System usedforModal AnalysisCenter ofGravity Magnetic Spring Stiffness [N/m] Mass[kg] Maximum AxialForceonthe MainBearing [N]X[m] Y[m] Z[m] -9.3x10.6-1.4xl0.3 2.6xl0.6 25192 42x10.3 397.2 MainBearing AxialPreload [N] 1.76 MainBearing Stiffness (z[N/m] Axial Radial 35.9x106 13.6x106 Axial Radial Floating Bearing Stiffness °_ 10.6x106 5.5x106 [N/m] Inertia [kg.m2] 5.123x106 Figure18presents theresultofthemodalanalysis 8.Thefirsttwomodeshapes correspond tofrequencies (411.4Hzand414.5Hz)insidetherangeofinterest (between 20and2000Hz)andareinlongitudinal direction. Duetolargediameters, thefirsttransversal modeoccursonlyover2,000Hz. MajorModeX-axis 411.4HzSecondary Mode MajorZ-axis X-axis >2,000Hz Figure18.ModalAnalysis Results fortheStructural Response oftheMobile Package Experimental measurements showthemajormodes at331.5HzonX-axis, 695.3HzonZ-axisand respectively 873.3HzonY-axis(usingthecoordinate system presented infigure17).Thedifference inthe transversal andlateralvalues ofthecalculated andmeasured natural frequencies isdetermined by bearing stiffness. Itmaybeconcluded fromtheabovethattheaxialfree-body motion ofthemobile package generates thelargestaxialloadonthebearing andthestiffness ofthebearings determines the loadsintransversal andlateraldirections 9. Bearing RadialLoads Radialloadsarecalculated according tothemethod usedforaxialloads.Experimentally 10derived steady-state transmissibility functions aresuperimposed todetermine forlateralandtransverse vibration responses. Thepeakradialforces(3(;)aredetermined tobe66.3NwithZ-axisinputand56.3Nfromthe Y-axis. 7Calculated usingPro-Engineer software. rJ.Calculated withESTLCABARET around peakaxialandradialloads(X-axis). 8Assuming infiniterigidityofthebearings 9Theshaftpackage behaves astotallyrigid. 10Usingasimilarequation toequation (1). NASA/C P--2002-211506 300
Table4summarizes thebearingloads. LoadDirection/ Vibration axis AXIALI3 [N] RADIAL Main [N] FloatingTable4.Calculated LoadsontheBearings X-axis Vibrations 397.20 13.02Y-axis Vibrations 167.90 48.54Z-axis Vibrations 206.50 70.69 2.08 7.76 11.31 Bearings Analysis TheBearing Analysis section isbasedonthecalculation flowdescribed by[7]andotherindustry practical recommendations. Forclarityallpartsnotrelevant totheproblem athand11(i.e.,lifeanalysis, cagerotation instability, frictionandlubrication, temperature effects, etc.)wereomitted. StaticAndDynamic Load-Carryin.q Capacity 12 Thebasicstaticload-carrying capacity isgivenby: Co (4) Where: C0=static load-carrying capacity; S0=static safety-factor; X0=static radial-factor; Y0=static axial-factor; FRADIAL=Static radial-load onthebearing; FAXlAL=Static axial-load onthebearing. Thedynamic load-carrying capacity canbecalculated withaformula similarto(4)inwhichthetermsin brackets (equivalent staticload)arereplaced bytheequivalent dynamic load-rating. Acatalog bearing similar withthemainbearing hasratedloads: FRAD/AL=858.50 N,FAXlAL=2166.28 Nandadynamic load-carrying capacity ofC=-814.02 N.CocArALOG=1598.24 Nandworst-case mainbearing basedondata intable4(assuming asafetyfactor13of2)Cox.Axls=412.82 Norastaticsafetymarginof+287.15%. For thedynamic load-carrying capacity assuming thatthesameloadswillactonthebearing duringoperation, theworst-case dynamic load-carrying capacity isCx.Ax_s=507.76 Norasafetymargin of+60.31%. It resultsthatthebearing haslargesafetymarginversustheloads. Advanced Bearinq Analysis Theresultsoftheadvanced bearing analysis (performed usingCABARET andA.B.Jonessoftware) are summarized intable6TM.Itisassumed thattheentireloadapplied bytherotorisdistributed evenlyamong theballcontacts ofthemainbearing. Thetrailerbearing isconsidered tobeunloaded. Moment loadswill beinsignificant sincethetrailerbearing limitsrotation oftheshaftaboutthemainbearing center. The software foranalysis ofthebearings calculates thenumber ofballsthatcarrysignificant loads.Themost heavilyloadedballisconsidered fortheworst-case Hertzian stresses. Theanalysis wasperformed forthe worst-case measured impact loadof397.2Ninlongitudinal direction, andfor206.5axial-load corresponding theaxis(Z-axis) onwhichthefailureoccurred. Axialforcesforthemainbearing. Radialforcescalculated asvectorsumofthetwo corresponding forcesonY-axisandrespectively Z-axis. 11Thefailurewasundervibration andinlatched position. 12Thistypeofselection calculation isspecific forthecasewherebearings areselected fromacatalog. Inourspecific casethebearings arecustom build,nevertheless wepresent acalculation basedon similarcatalog bearings toshowthatthisisnotcapable ofcatching thistypeoffailure. 13Ball,quietrunning, normal loading [7]. 14ForA.B.Jonesanalysis bothbearings wereconsidered. NASA/CP--2002-211506 301