DCMotorSelection forSpaceMechanisms DavidB.Marks*andRichard A.Fink* Abstract "DCMotorSelection forSpaceMechanisms" presents majortypesofDCmotors, theirdesigndifferences, andapplication guidelines, sothattheirselection andspecification foruseinspaceapplications willbe enhanced. DCmotors thatareexamined include twoandthreephasebrushless, brushed, conventional andhybridsteppers, andspecialty brushless forlowtorquerippleandhighspeedspinning applications. Motordesignandapplication concepts arepresented thatareessential forpropermotorselection topoint antennas, drivesolararrays, latch,andtoperform otherspacemechanism functions. Atradeoff matrix compares motortypesforspecific applications. Lessons learned fromavariety ofspaceflightmotor applications showselections thatworked wellandsomethatdidnot. Introduction D.C.motors playanintegral andcriticalroleintheoperation ofspaceflighthardware fromtheSpace Station tocommunication satellites. Motors provide motion driveforsolararraydeployment, antenna pointing, boomdeployment, cargolatching, aperture movement, inertial spinning forcontrol moment gyros,andmanyotherapplications. Without aproperunderstanding ofhowtoselectmotorcomponents andwhathasbeendonepreviously, itislikelythatmechanism performance anomalies willresultorredesignwillberequired. Giventhisdiversity ofapplications, proper selection ofmotortypesandspecification ofthemotor performance parameters forspaceflightmechanisms isessential tothesuccess offuturespace missions. Whilethesubject ofmotordesign isbeyond thescopeofanysinglepaperorbook,the fundamentals common toDCmotors andtheirapplication canbeexamined. Technical essentials for understanding andspecifying DCmotors, typesofDCmotordesigns forspacemechanisms, andDC motors inspaceapplications arepresented; aselection matrixintegrates keymotordesign and application factorswithlessons learned toguidefutureselection. IfDCmotorselection properly takesinto account motordesign differences andtheireffects onspecific spaceapplications, thentheresulting spacemechanism willexhibitsuperior performance andreliability. Inaddition tounderstanding motordesignandtradeoff concerns, aclosereviewofspacemotorheritage todetermine whathasbeenusedonprevious similarspaceapplications isimportant forassessing what touseonnewapplications andhowtospecify theuniquerequirements. Design considerations relatedto motorselection aregearreduction, motordriveelectronics, bearings, lubricants, andsystem dynamics. Theseassociated considerations cansignificantly affectthesuccess ofamotorized mechanism andwill oftencomeupinareviewofheritage mechanisms andlessons learned. Whileathorough reviewofthese associated concerns isbeyond thescopeofthispaper,theyareindicated asimportant relatedfactors. Technical Overview Inordertoillustrate thevarietyofmotorselection, Table1"MotorDesign Overview" showsalistofthe morecommon DCmotortypes.Because morethanonetypeofmotormaybeusedforanygiven application therearetradeoffs toconsider. Additionally, power consumption, envelope, torque characteristics, life,anddriveelectronics complexity usually weighinasmajorconcerns. MoogInc.,Technical Office,Research Triangle Park,NC Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/CP--2002-211506 89