Tribological Properties ofaPennzane®-Based LiquidLubricant (Disubstituted Alkylated Cyclopentane) forLowTemperature SpaceApplications Clifford Venier*, Edward W.Casserly*', William R.Jones,Jr.+,MarioMarchetti +,MarkJ.Jansen++,Roamer E.Predmore +++ Abstract Thetribological properties ofadisubstituted alkylated cyclopentane, Pennzane ®Synthesized Hydrocarbon FluidX-1000, arepresented. Thiscompound isalowermolecular weightversion ofthe commonly usedmultiply alkylated cyclopentane, Pennzane ®X-2000, currently usedinmanyspace mechanisms. New,lowertemperature applications willrequire liquidlubricants withlowerviscosities and pourpointsandacceptable vaporpressures. Properties reported include: friction andwearstudies and lubricated lifetime invacuum; additionally, typical physical properties (i.e.,viscosity-temperature, pour point,flashandfirepoint,specific gravity, refractive index,thermal properties, volatility andvapor pressure) arereported. Introduction Allspacecraft utilizemechanisms contain moving mechanical assemblies (MMAs) thatrequiresomeform oflubrication tofunction properly [Jones andJansen, 2000].Lubricants include liquids, greases, and solids.Thesematerials normally operate inultrahigh vacuum. Therefore theymustpossess extremely low vaporpressure [Nguyen etal,2001].Mostspacecraft arethermally compensated sothattheselubricants onlyexperience temperatures inthenarrow rangeof0to+60°C. Thisallowsconventional liquidand greaselubricants tobeused.However, newspacecraft mechanisms arebeingdesigned thatwilloperate atmuchlowertemperatures (i.e.,-50 to0°C).Moststandard liquidlubricants possess veryhigh viscosities inthistemperature range,whichwouldnecessitate theuseoflargemotors withhighpower requirements tomaintain design torque margins. Therefore, lowerviscosity liquidlubricants thatstill possess lowvolatility areneeded. Pennzane ®Synthesized Hydrocarbon FluidX-2000 (usually calledPennzane ®fluid)isamultiply alkylated cyclopentane hydrocarbon thathasdesirable tribological properties formanyspaceapplications [Venier andCasserly, 1991;Venier, etal.,1992;Carreetal.,1995,Casserly andVenier, 1999].Asixyearlife testofaCERES bearing assembly usingPennzane ®fluidhasyielded excellent results [Brown etal., 1999].Accelerated andoperational lifetestsonbearings fortheMODIS instrument havealsobeen completed usingaPennzane ®fluidformulation [VanDyk etal.,2001]andshowed excellent results. Full scalebearing testsconducted atLockheed Martincompared theperformance ofaformulated Pennzane ® fluidX-2000 toBray815Z,astandard spacelubricant, andshowed Pennzane ®fluidtohaveatleasta7 timeslifeadvantage over815Z[Loewenthal etal.,1999].Relative lifetime tests[Jansen etal.,2001; Jonesetal.,2000]usingtheSpiralOrbitTribometer (SOT) havealsoshown thatunformulated Pennzane ®fluid(X-2000) yielded thegreatest relative lifetime compared toaseriesofspacelubricants. Despite theexcellent performance ofPennzane® X-2000, itshighviscosity atlowtemperature (i.e., 80,000cPat-40°C)precludes itsuseundertheseconditions. Pennzane ®X-2000 isamember ofthechemical classofmultiply alkylated cyclopentanes orMACs [Venier andCasserly, 1991;Casserly andVenier, 1999].Itispredominately thetri-alkylated cyclopentane product prepared from2-octyldodecanol, namely, tri-2-octyldodecyl cyclopentane. Thedisubstituted PennzoiI-Quaker StateCompany, TheWoodlands, TX "*Penreco Company, TheWoodlands, TX +NASAGlennResearch Center, Cleveland, OH ++Sest,Inc.,Middleburgh Hts.,OH +++NASAGoddard SpaceFlightCenter, Greenbelt, MD Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/CP--2002-211506 331