Design ofaPower-Assisted Spacesuit GloveActuator Russell D.Howard* Abstract Thispaperpresents thedetailsofthedesignandimplementation ofanelectromechanical power-assisted spacesuit gloveactuator. TheprojectwasajointeffortbytheUniversity ofMaryland's SpaceSystems Laboratory andILCDover,Inc.,andinvolved innovative approaches topoweraugmentation andcompact actuator packaging. Thefirstactuator builtvalidated several basicdesignconcepts, andthesecond demonstrated improved performance andmetmanyofthegoalsforflightqualification ofthetechnology. Introduction Agreatdealofhumanextravehicular activity (EVA)isplanned byNASAforthecoming years,primarily in support oftheInternational SpaceStation. Spacesuit glovedesignisacrucialelement intheproductivity, dexterity, comfort, andprevention offatigueofanastronaut working inEVA.Improvements inglove designhavebeenidentified asaNASApriority[1][3]. Spacesuit glovedesignisadifficult problem. Thelargerspacesuit joints(hips,shoulders, etc.)canbe designed tohaveconstant volume overtheirrangeofmotion, eliminating theeffectofpressure forceson jointdynamics. Intheglove,however, thelargenumber ofdegrees offreedom (DOF)(atleast16) combined withthesmallvolume available andtheneedfordexterity makethisapproach difficult or impossible. Hence, theconventional spacesuit glovedesignisessentially aballoon, withasingle carefully-selected "neutral" position. Anymovement fromthisneutral position requires theastronaut to combat pressure forces(30kPa(4.3psi)differential incurrent NASAspacesuits), aswellasthestiffness, frictionandinertiaoftheglovematerial. Sincethemuscles ofthefingersandhandaresmall,a significant fraction oftheirstrength maybeneeded toovercome theseforces,leading tolimitedworking forcecapability andrapidfatigue[5].Theauthor's personal experience inneutral-buoyancy simulation (NBS)bearsthisout.Itcanbequitefatiguing tosimplyholdawrench inaclosedhandfortenminutes. Theintentofthisprojectwastoinvestigate theaddition ofpowerassistance toaspacesuit glove, combining theroboticactuator technology developed bytheUniversity ofMaryland's SpaceSystems Laboratory (SSL)withtheglove-design expertise ofILCDover,inc.Tosimplify theproblem, initiallya singledegree offreedom wasselected forstudy:themetacarpalphalangeal (MCP)joint.Thisisthe motionobtained whenallfourfingersareclosedtothepalmsimultaneously. MCPmotionisanessential degree offreedom forgripping tasks(oftenrequired whenworking withtools),andonethatisopposed by considerable forcesduetopressurization incurrent spacesuits. Thepoweraugmentation objective wasnottomultiply theoperator's strength byalargefactor,butsimply tocompensate fortheresistance forcesimposed bythespacesuit gloveitself.Ideally, thiswouldrestore "nude-body" performance totheMCPjoint,making workintheglovefeelmorenaturalandlessfatiguing. Othergroups havepreviously explored augmented glovedesigns [2][4][6]. Theapproaches takenhave included purelymechanical changes totheglovedesign, passive spring-based mechanisms, pneumatic systems, andelectromechanical actuators. Thesesystems haveeitherfailedtoachieve adequate performance, exceeded themaximum packaging volume allowed byNASAEVAstandards, orused technology incompatible withspacesuit operations. "University ofMaryland, College Park,MD Proceedings ofthe34_Aerospace Mechanisms Symposium, Goddard SpaceFlightCenter,May10-12,2000 89