Design andManufacturing ofExtremely LowMassFlightSystems Michael R.Johnson* Abstract Extremely smallflightsystems posesomeunusual designandmanufacturing challenges. Thesmallsize ofthecomponents thatmakeupthesystem generally mustbebuiltwithextremely tighttolerances to maintain thefunctionality oftheassembled item.Additionally, thetotalmassofthesystem isextremely sensitive towhatwouldbeconsidered smallperturbations inalargerflightsystem. TheMUSES C mission, designed, built,andoperated byJapan, hasasmallroverprovided byNASAthatfallsintothis smallflightsystem category. ThisNASA-provided roverisusedasacasestudyofanextremely small flightsystem design. Theissuesthatwereencountered withtheroverportion oftheMUSES Cprogram arediscussed andconclusions abouttherecommended massmargins atdifferent stagesofasmallflight system projectarepresented. Introduction TheMUSES CNanorover Mission TheMUSES Cmission isconducted bytheJapanInstitute ofSpaceandAstronautical Science (ISAS). TheMUSES Cspacecraft willnavigate toarendezvous withanasteroid andthendropmarkers ontothe asteroid surface fortargeting. Thespacecraft willthendescend totheasteroid surface foramomentary touchdown, atwhichtimeaprojectile willbefiredintotheasteroid surface. Thedebrisgenerated fromthe projectile willbecaptured inacone-shaped collector andguidedtoasample container. Thespacecraft willfireitsengines toriseapproximately 20kilometers fromthesurface andmaintain thatposition while obtaining remote science dataontheasteroid. NASAiscontributing totheMUSES Cmission inseveral ways.Oneofthemanyaspects oftheNASA contribution consists ofasmallrover,calledtheNanorover, whichwillbedropped offfromtheMUSES C spacecraft whilethespacecraft isstillatanaltitude of20to30meters abovetheasteroid and descending. TheNanorover willthenfree-fall andimpactthesurface oftheasteroid, landing atalarge enough distance fromthespacecraft toprevent theplumeproduced bythespacecraft engines onascent fromblowing theNanorover offtheasteroid surface. OncetheMUSES Cspacecraft hasobtained a sample oftheasteroid andrisentoitsparking orbit,theNanorover willbeginitsmission. Thefirstpartof thismission involves afullyautonomous self-righting oftheNanorover vehicle combined withdetermining itslocation usingastarmap. TheNanorover wasbuiltbyNASA's JetPropulsion Laboratory inPasadena, California 1.TheNanorover is significantly smaller thantheSojourner roverthatwasdeployed onthesurface ofMarsin1997.Asideby-side comparison oftheNanorover andtheSojourner roversittingononeofthesidepetalsoftheMars Pathfinder landerisshowninFigure1.Themassandvolume oftheNanorover arebothapproximately one-tenth oftheSojourner rover's massandvolume. TheNanorover ismadetooperate ina20micro-g environment, whichrequires additional mobility functions thattheSojourner roverdidnothave. Additionally, theNanorover carriesonemoreinstrument thantheSojourner rover,hasgreater computing capabilities, andhasahigherperformance camera andhazard avoidance system. Theneedtofitthis increased functionality intothesmallvolume oftheNanorover meantthatthecomponent partswouldall beverysmall. *JetPropulsion Laboratory, California Institute ofTechnology, Pasadena, California TheNanorover portion oftheMUSES Cmission wascancelled andwillnotflywiththeMUSES C spacecraft. TheNanorover wascompleted through component fabrication, assembly, andsometesting. Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/CP--2002-211506 103