Marshall SpaceFlightCenterHighSpeedTurbopump Bearing TestRig HowardGibson', ChipMoore*,andRobertThom* Abstract TheMarshall SpaceFlightCenterhasauniquetestrigthatisusedtotestanddevelop rollingelement bearings usedinhigh-speed cryogenic turbopumps. Thetesterisuniqueinthatitusesliquidhydrogen asthecoolantforthebearings. Thistestrigcansimulate speedsandloadsexperienced intheSpace ShuttleMainEngineturbopumps. Withinternalmodifications, thetestercanbeusedforevaluating fluid film,hydrostatic, andfoilbearingdesigns. Atthepresenttime,thetestrigisconfigured toruntwoball bearings oraballandrollerbearing, bothwithahydrostatic bearing. Therigisbeingusedtoevaluate thelifetimes ofhybridbearings withsiliconnitriderollingelements andsteelraces. Introduction Marshall SpaceFlightCenterstartedbearingtestinginthe1980'sduetolowlifetimes experienced in SSMEturbopump bearings. Thebenchmark bearinglifewassetusingthethenusedSSMEturbopump bearings inabearingtesterdesigned forliquidoxygencoolant. Asnewbearingtechnologies developed, improved bearings wereinstalled andevaluated. Thebestimprovement wasfoundtobehybridbearings withsiliconnitriderollingelements andsteelraces.Theoriginalbaseline offifteenminuteswasimproved greatlytofourhundred andtwentyminuteswiththisdesign. Inthe1990's,theneedfortestinghighspeedhydrostatic bearings andachangeinsupplierof turbopumps alongwithanemphasis inextending thelifetimes ofbearings usedinhydrogen, brought abouttheneedforanewtestrig.Atesterwasbuiltthatcouldbeconfigured toruneither ball/ball/hydrostatic, ball/roller/hydrostatic, orallhydrostatic bearings. Theunitispowered byagaseous nitrogen turbine,whichgivesitaveryhigh-speed capability. Speedsofthirty-five thousand rpmare routinely reachedwiththecapability togohigher.Axialandradialloadingispossible withcycling capabilities. Thetestrigissimpletoassemble anddisassemble andhasborescope portstoinspectthe bearings withoutdisassembly. Therigcanalsorunusingliquidnitrogen oroxygenasthecoolant. Thistestrighascompleted fivetestseries.Thesetestswereusedtoevaluate ball/ballandball/roller configurations usinghybridbearings. Alltestsweredoneinliquidhydrogen. Totaltimeaccumulated is approximately 75,000seconds. Aftereachtestseries,aninspection ofthehardware isperformed inthe metrology lab.Tracesofsurfacefeatures aremade,racecurvatures aremeasured, roundness measurements aremade,balldiameters aremeasured, andvisualinspections arerecorded. Thispaperfocusesontheresultsoftheball/roller bearingtesting. Resultsoftheball/ballbearingtesting werepresented atthe32ndAerospace Mechanisms Symposium byChipMooreinMayof1998.1 TestRequirements TheTestRi_:l Thetestrig(Figure1)isaverticalshaftoriented testerwithaballbearingatthetopandeitheraballor rollerbearinginthemiddleposition. Nearthebottomoftheshaftisahydrostatic bearing. Thisrigwas originally designed tobeahydrostatic bearingtesterbutwasmodified totestrollingelement bearings also.Atthebottomoftheshaftisaturbinethatspinstheshaft.Gaseous nitrogen isforcedintotheinlet manifold andexitsthebottom. Speedsof35000rpmareroutinely usedfortesting.Radialloadsare *NASAMarshall SpaceFlightCenter,Huntsville, AL Proceedings ofthe34thAerospace Mechanisms Symposium, GoddardSpaceFlightCenter,May10-12,2000 331