Conceptualization andDesign ofaMechanical Docking System . TroyNilsonandMitchWiens Abstract Ascaleable Mechanical Docking System (MDS)hasbeendeveloped andtestedtosupport docking and servicing unmanned spacecraft. Toallowforsystem useonvarious spacecraft configurations, theMDS wasdeveloped togeneral requirements anddesigned forscaling ease.Information onexisting spacecraft docking systems wascombined withaconceptualization ofhowspacecraft servicing mightoccurto develop asimpleandcosteffective softdocking system. Thedevelopment, testing, andperformance of thissystem, underthechallenging absence ofhardrequirements, aredescribed. TheAirForceResearch Laboratory (AFRL) funded theproject through twoPhaseIandPhase IISmallBusiness Innovative Research (SBIR)grants. <_:_iiii_i_-i:_-_Introduction .......:;_++--;:;::" Overthepastdecade therehasbeenanaggressive pushtodevelop the ......,,,_, capability ofunmanned vehicles toservice orbiting spacecraft. Thereasons 7+_:-_!_/----'+__:::::::::-_ arecompelling: _:_,c___U_:_( • _i---r-'.."_+`-+-'+` ,_,Toextendthelifeofspacecraft attheendoflifeduetopropellant depletion. Toreplace components thatareobsolete orhavefailed Tocapture spacecraft andmovethemtomoreeffective orbits(e.g.a _ _ spacecraft isinanunusable orbitfromlaunchvehiclefailure) _-_,+--:J_'....,I!,! Torecover aspacecraft withafaileddeployment bymanually deploying ;"°-_-__.' Toexamine spacecraft todetermine causeoffailure _,-_:++_-.____._Overthepast20years,aservicing capability hasbeenavailable through the:SpaceTransportation System (STS),orShuttle. However, thehighcostofthisapproach haslimiteditsusetoveryexpensive systems withintheShuttle's orbitalreach(e.g.,Hubble). Asaresult,thesystem isgenerally impractical forcurrent andemerging spacecraft servicing needs. Unmanned servicing technology isexpected tomanifest inthenextdecade asprograms suchasOrbital Express areforwarded. Keytothesesystems isthecapability tocapture, mechanically connect, and makefluidandelectrical connections between twospacecraft, anoutstanding mechanisms challenge. Starsys Research Corporation (SRC), aspartoftwoPhaseIandPhaseIISBIRprograms, hasbeen activeindeveloping thistypeofsystem. Thechallenges associated required thatasetofparameters for amechanical system capable ofsoft-docking twoindependent spacecraft bedefined. Design goals included provisions forthealignment, structure, andcoupling forcesnecessary tojoinfluidand/or electrical couplings. Thissamemechanism wastogenerate latching/rigidizing forceslargeenough to reactmoment loadsinduced oncethespacecraft joined. Additional challenges resulted astheproject wentforward without tangible system requirements (i.e.,thehardware wasdeveloped andtestedina "requirements vacuum"). Although theprojects wereundertaken without complete definition ofaservicing program, therewasalways theclearintention ofcreating asystem applicable toavariety ofprograms andmissions. Thedevelopment approach included anevaluation ofcurrent docking technology, a conceptualization ofvarious mechanism configurations andmission scenarios, andthenthe implementation ofdetailed tradestudies intended toidentify aviableconcept. Theresulting system was designated theMDS(Mechanical Docking System). Starsys Research Corporation, Boulder, CO Proceedings ofthe3_hAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/CP--2002-211506 265