instruments areinstalledbytheyear2004,theselubricantswillbepresentinatleastonemechanism per scienceinstrument. Althoughpronetopolymerization, thereareapplications wheretheuseofthis lubricantisjustified;usuallyduetoarelativelylowtotalnumberofrevolutions incombination withlowto moderatebearingstresses.Toverifysuitability,comparison tosimilarlife-testedengineering modelsmay beperformed. Anotherapproach,definedbelow,istoquantifythecumulative combinedeffectofduty cyclesandcontactstresses.Thisfirst-ordertechniqueforestablishing performance marginsisnarrowly definedbytheexpectedoperatingparameters, suchaslubricantoperatingregime,Hertziancontact stress,anddutycycles,established bythehardwaretobesimulated. Thisobjectivewasaccomplished throughthesimultaneous testingofthreebearingpairsoperatingatlow contactstress,withtheonlyvariabledistinguishing onesetfromanotherbeinglimitedtotheoildiluent. Thediluentwasusedinthepreparation ofanoilsolution,whichinturnwasusedtorinseoffexcessoil, andtoperformparticlecounts.Asexplainedbelow,thisprocesswassubsequent toallcleaningand lubricationsteps.Itwasanticipatedthatthistestwouldthereforenotonlyprovidethetimeperiodpriorthe onsetoflubricantpolymerization, butalsoyieldinformation regardingtheeffectofthediluent,ifany,with respecttotheperformance ofthelubricatedbearings. TestApproach Thesolvents studied were:DuPont'sFreonTF(CFC-113), DuPont'sVertrel®XF,and3M'sNovecTM HFE-7100. Vertrel XFisahydrofluorocarbon, orHFCsolvent, whereas HFE-7100 isahydrofluoroether. LikeVertrel XF,HFE-7100 haszeroOzoneDepletion Potential, butlowervaluesforGlobal Warming Potential andAtmospheric Lifetimes thanFreonTForVertrel XF.Neither replacement solvent is considered tobeavolatileorganic compound bytheEPA.TheFreonTFservedasthecontrol. Threeback-to-back bearing pairs,SBBpartnumber 3HAR007P5A, wereprocured forthistest.These non-separable 440Cangular contact bearings wereobtained withone-piece machined phenolic cages, andwereselected basedonavailability. Sincethereliability ofthetestcouldtherefore notbeincreased by duplicating bearing pairs,greatcarewasexercised duringtheprocessing ofthebearings tominimize variables. Allbearing pairsweremaintained assetsthroughout processing byserialnumbers positioned onthelargefaceofeachouterrace.Toavoidpotential preload problems, ballsweresegregated and maintained withtheappropriate innerandouterrace.6 Thebearing lubrication wasperformed atBallAerospace &Technologies Corp.,andwastypicalofthe processing performed forthelubrication offightbearings. Theprocessing consisted ofdisassembly using afixtureusedtoheattheouterrace,andcooltheinnerrace.Allcomponents wereinspected athigh magnification afteraninitialhydrocarbon solvent cleaning. Following furtherhydrocarbon solvent cleaning andextensive baking, allphenolic cagesweresimultaneously impregnated forseveral hundred hoursat elevated temperature withthesamelotofspecially processed Brayco 815Z.Thespecial process isa proprietary vacuum bakingprocedure thatreduces thevolatility oftheoil.Thevaporpressure measured at BallAerospace usingathermally controlled quartzcrystal microbalance measurement technique was foundtobelessthanlo1014torratroomtemperature. Following theimpregnation ofthecagesandreassembly, eachbearing wascleaned untiltheparticle levelswereinaccordance withMIL-STD-1246 Level100formetals, andlessthanLevel200forall particles. Thisprocess usedafive-percent byweightsolution oftheoilintheappropriate solvent: either FreonTF,Vertrel XF,orHFE-7100. Thissolvent substitution wastheonlydifference thateachbearing pairwassubjected toduringprocessing. Therinseresulted inadeposition ofapproximately 20mgofoil ontheballandraceway surfaces; enough toproduce aslightoilmeniscus between theballandraceway, butslightlylessthanwhatwouldnormally berequired forflightbearings. Ifthesehadbeenflightbearings, additional oilwouldhavebeenadded. 26