ISSS/ADeployment -TheHighs&LowsofEVAContingency Capability, ADesigner's Perspective BertHaugen, Malcolm Ferry*andKevinKlein* Abstract EachsolararraywingfortheInternational SpaceStation (ISS)isroughly 38feetwideby115feetlong whenfullydeployed andisthelargest deployable (andretractable) spacestructure builttodate.The deployment andrepairofthefirsttwowingsonSTS-97 inDecember 2000highlighted boththe immensely beneficial capabilities provided bythemanned presence duringacomplicated deployment as wellassomeofthedifficulties inusingthiscapability toitsfullestpotential. Thispaperprovides a designer's perspective ofthesecapabilities inthecontext oftheISSsolararrayoperations onSTS-97 as wellassomeofthedifficulties inexercising thesecapabilities totheirfullestefficiency duringsuchafast pacedinvestigation. Suggestions willbeprovided tobetterequipmechanism personnel involved infuture investigations todealwiththeprogrammatic issuesasquicklyandeffectively asthetechnical issues. Introduction Thedeployment oftheISSsolararrayincludes bothplanned ExtraVehicular Activity (EVA)operations andautonomous operations toproperly deploythe164flexible solararraypanelsandtheirassociated structure. Thefinaloperations include theautonomous motordrivenextension ofthedeployment mast andtheapplication offullblanket tension (a.k.a.deployed preload). Duringthedeployment ofthefirst wingduringSTS-97, unexpected adhesion between manysolarpanelscaused aseriesofsticking then breaking looseofpanelsandgroups ofpanels. Theresulting dynamic motions induced inthepanelsand associated tensioning mechanisms weredramatic andultimately caused twoblanket tensioning cablesto jumptheirpulleys preventing properapplication ofthedeployed preload. Although thisanomaly wasnot readily detectable bydeployment telemetry ortomostobservers ofthedeployment video, the ramifications forachieving theproper deployed wingfrequency andstrength wereverysignificant. Fortunately, theresolution oftheOrbiter's "routinely" available videocoverage wasadequate toallow easydetection oftheanomaly whenviewed byindividuals familiar withthedesign. Withtheidentification oftheanomaly thesolararraydeployment support switched intothe troubleshooting mode,andthebenefits andthedifficulties ofthemanned operations capability quickly begantomaterialize. Thecapabilities ofthemanned operations allowed foramuchswifterandmore conclusive determination ofthenatureoftheanomaly thannormally experienced byspacecraft designers accustomed tothelimitations ofautonomous operations, andtheflexibility intheavailable repairoptions allowed adefinitive andcomplete restoration ofthewingtoitsnominal configuration. Thecapabilities that proved mostusefulintheevaluation andcorrection ofthesolararraydeployment anomaly included live videodownlink capability overportions oftheorbit,delayed videodownlink coverage ofthefull deployment event,variable resolution stillphotos ofrequested items,incredibly detailed inspection capability fromacamera ontheastronaut's helmet, avariety oftoolsavailable onorbit,theabilityof experienced astronauts tomakesafetyjudgments outside thedesignguidelines, andtheavailability of experienced astronauts andEVAsupport members tobequicklytransported toLockheed Martintowork asateamwithdesignpersonnel todetermine appropriate repairprocedures. Inspiteofthisimpressive arrayofcapabilities, therewereavariety ofimpediments inusingthese capabilities totheirutmosteffectiveness andefficiency whenviewed fromtheperspective ofamember of thedesigntroubleshooting team.Although someoftheseimpediments weretechnical innature, more oftentheywereself-inflicted bycommunication and/ororganizational barriers. Thedifficulties thatwere Lockheed MartinSpaceSystems Company, Sunnyvale, CA Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,May15-17,2002 NASA/C P--2002-211506 169