Weanalyzedtheactualtemperature theunitwouldseeinspaceafterthepredicteddwelltimeand changedthetestconfiguration toachievethismoreclosely.Ourtestplatewasprovidingamassiveheat sinkatthebaseandwaskeepingthebaseofthemastfromgoingcold.Tofixthis,wemountedthe canisterwithanairgapbetweenthetestfixtureandthebaseplatetoallowthebottomendofthecanister togetcoldermorequicklyanddecouplethebaseplatefromthefixture.Wealsoinstrumented the baseplatetomonitorthethermalgradientbetweentheoutercanisterandtheinnercanisterelementsat thebase.Tooursurprise,thetemperature differentialbetweentheinnerandoutercanisterswas40°Cat thepointwehadstartedthetestpreviously. Weincreasedthedwelltimeatcoldandmonitoredthe temperature ofthebaseplate.Whenitreachedequilibrium, thetemperature differentialwas16°C.Atthis pointweranthetestandthemastworkedproperly.Whathadhappenedinthetestfailurewastheouter canisteratthetopwascoldandthebottomofthenextinboardcanisterwaswarmerandthedifference wasenoughtoaffectoperation. Thelessonswedrewfromthiswereasfollows: Ourpracticeofdesigningsystemssothatwheneverpossibleanysubsystem canberemovedwithout teardownofthewholesystemproveditsworthagain.WewereabletoremovetheSTEMTMdeployer quickly, testit,fixit,andreinstall itwithout amajorimpacttotheprogram. WecouldhavetestedtheSTEMTMsubassembly inacoldchamber priortothefulltest.Thiswouldhave highlighted theproblem withtheswitchbeforethestartofflighttestingontheintegrated canister. Itisimportant tomatchflightconditions ascloselyaspossible duringtesting. Havingalargeheatsinkand notdwelling attemperature foralongenough timecostusseveral daysofschedule. Eventhough wehadadeployment anomaly, wewentaheadwithwhatwecoulddoanddiscovered another problem withtheswitch.Ifwehadstopped everything afterthefirstproblem, itwouldhaveadded moretimeandtesting totheschedule. Sometimes itisworthwhile tocontinue asfaraspossible to discover asmanyproblems aspossible inagiventestsetup,aslongasyouwillnotdamage the hardware. AHeavyLesson Wediscovered something elsethatisobvious inretrospect. Mostofourprevious designs weresmall enough tocarrybyhand.Thismast,fullyassembled withallCFEinplace,weighed 54kg(120Ib),which madehandling morecomplicated. Theweightplusthesizeofthestowed mastrequired theuseofforklifts andcranes tomoveitabout,alongwithseveral employees toposition andhandletheunit.Tooling for manufacturing thepartswaslarger,cradles andGround Support Equipment (GSE)werelarger,and existing GSEthatworked fineonlightweight masts, couldnotbeused.Thisresulted inanincrease in staffing fortheprogram, whichincreased costandschedule. Thelessonhereisthis:Ifaproduct variesconsiderably insizeandweightfromotherprojects ofasimilar nature, thensomeaccount shouldbetakenoftheimpactthiswillhaveontheproject. Thisapplies to largeincreases orreductions insize.Asmentioned before, thisdesign wasnearlyfivetimeslargerin diameter thantheprototype mastwebasedthedesignon. Conclusions TheISISmastqualification program istypicalofanynewhardware. Thecustomer requested changes soonafterthestart.Ourowninternal designandanalysis teamrequired morechanges. Someitemswe designed worked betterthanweexpected, andsomewejusthadtoendure. Manufacturing hadproblems withmaking someparts.Testing didnotrunassmoothly aswehadplanned. Intheendhowever, the designsuccessfully mettherequirements ofthespecification. NASA/CP--2002-211506 160