Development ofanAutomated BoltDriverfortheSpaceStation TrussAssemby Richard Meinhold" andKenSeidner'" Abstract TheMoogSpaceStation BoltMotorActuator (BMA)isarotaryactuator comprised ofabrushless DC motor,controller, and120VDC-DC powersupplycoupled toafour-pass planetary gearsystem and containing amanual override (MO)system. Thispaperdiscusses thenewtechnologies developed and lessons learned duringtheBMAdevelopment. Theseinclude theuseofarelatively newmaterial, Pyrowear 675,anewVaporDeposition coating, WC/C,andahard-on-hard (HOH)wormdrivesystem delivering 135.6N,m(1200in.lb)oftorque(theprimary focusofthispaper). Introduction TheBMAwasacontract awarded byMcDonnell Douglas Aerospace (nowBoeing Aerospace, Huntington Beach) toMoogInc.inDecember of1995foruseontheInternational SpaceStation. Thecontract schedule detailed an18monthstart-to-finish program withonedevelopment unit,oneQualunit,and20 "flight"units.Fouroftheflightunitswereslatedfor"nextlevelassembly" Qualification. TheBMA attaches tothemotorized boltassembly (MBA), whichisproduced byBoeing, andfacilitates theactual structural connection andattachment interface loadbetween thefivetrusselements inboard ofthesolar arrays,P3,P1,SO,$1and$3.(P=Port,S=Starboard). Several oftheoriginal BMAdesignaspects weremodeled aftertheMoogFluidQuickDisconnect (FQDC) program. TheMoogFQDCenables theflowofliquidammonia between thediscrete sections ofthe International SpaceStation Thermal Management System. Thesedual-line, manually-actuated devices provide essentially zero-loss throughflow capability. Redundant sealsareprovided against leakage in boththematedandde-mated conditions, andthecoupling isdesigned tolimitspillage volume upon demating tolessthanonecubiccentimeter. OneFQDCiteminparticular thatplayedamajorroleinthe BMAdesignwasapositive lock,no-backdrive device. Thisdeviceallowsnearly100%ofapplied torque topassfrominputtooutputand0%torquetopassinreverse (fromoutputtoinput).Whilenotoperating, theno-backdrive uniteffectively usesapininaslotconcept toprevent unanticipated rotarymotion. UnitDescription TheBMAisarotaryactuator comprised ofabrushless DCmotor,controller, and120VDC-DC power supplycoupled toafour-pass planetary gearsystem. Themotorrunsatapproximately 3400rpm,which resultsin4.1rpmattheBMAoutput(a25.4-mm 16/32femalespline)attheendofthe833:1geartrain. Dualinputelectrical connectors allowpowered operation fromeitheroftwoindependent BoltBus Controllers (BBC's). Theelectrical connectors supplypower(120VDC), direction logicsignal,redundant heatercurrent, redundant RTDbasedtemperature feedback, andlimitswitchpigtailpass-through lines. Thelimitswitches arepartofacustomer-controlled matingassembly. TheRTD'sarecustomer-supplied (Boeing PartNumber 1F08041-1) andtheheaters areKapton® 1encased, inconel element, thermal foil heaters supplying approximately 28wattspercircuit. Thesedevices wereneeded tomaintain the electronics atorabove-42.8°C (-45°F) whileonorbit. Thebrushless DCcontroller andDC-DC powersupplyweretotallycontained insidetheunitontwo independent multi-layered circuitboards. ThedualpowerlineinputswereY'dinternal totheunitand optoisolated attheboardlevel.Allelectronics weredesignated "S"classorequivalent andratedfor *MoogInc.,SpaceProducts Division, EastAurora, NY *"TheBoeingCompany, SpaceStation Electronic Actuation Products, Huntington Beach, CA Proceedings ofthe34"_Aerospace Mechanisms Symposium, Goddard SpaceFlightCenter,May10-12,2000 75