dimensional changesofupto0.5%aswaterisabsorbedovertime.Italsorequiredapost-machining recureprocessthatlasted17days.Titaniumwasusedasthenewmountinginterface,withtheadditionof G10fiberglassinsulatingwasherstoreduceconductive losses.Thebodyofthepinpullerwasalsomade easiertomachinebyeliminatingthehigh-tolerance, highsurfacefinishbores(25micronor10p-in)forthe seals.Instead,thesealsremainstaticinthebores,andthehighsurfacefinishisappliedtothepin.This facilitatesmachiningandinspectionoftheparts. CostComparisons Inquantities of1to4units,thepriceoftherevised pinpuller isabout30%higherthantheoldunit. However, thehigherfirstcostisoffsetbytheloweroverallsystem costsduetothesimplified controland operation. Thiscanbeseeninthemarket response totheimproved design, andthefactthatveryfew pinpullers arenowsoldwithout circuitinterrupts. Inhigherquantities, theunitcostdifference isreduced. TheIridium unitwaspricedatroughly $600. Starsys hascostedaslightlyhighervolume oftheimproved pinpullers atroughly $715perunit,ora19% difference. Assuming comparable designanddevelopment costs,thedifference totheIridiumcontract to usetheimproved designwouldhavebeenabout$115,000. Starsys spentatleasthalfthatamount in additional testing toresolve thecontrol issue.Andmanytimesthisamount weremostlikelyspentbythe antenna supplier andspacecraft company. Though itiseasytoanalyze thisinhindsight, theadditional costoftheimproved designwouldhavebeenworthwhile. Conclusions Designdriversforcommercial spacecraft canbeverydifferent thanforcustom spacecraft. Theimpetus to reduce costismuchgreater, because inlargevolumes, smalldifferences incomponent costbecome largesums.Theschedule pressure isgreater, duetothebusiness pressure tobecome profitable quickly inordertopaybackinvestors. Large,multi-discipline designreviews arelesscommon. Responsibility is spreadoverlargerteams,andusuallyacrossseveral companies. Thesefactorscanhaveastrongimpact ondesignchoices andtheoverallsuccess oftheprogram. Someelement ofthefollowing itemswerepresent ineachoftheproblems encountered onIridium: •Focusonmeeting immediate pricegoalswithout fullyconsidering downstream coststoimplement. •Earlyassumptions madetomeetcostgoalswerenotcompletely checked outduringdesignprocess. •Littlecommunication between designer andfinaloperator ofequipment/spacecraft. •Over-reliance onoperator training andprocedures tocontrol riskoffailure, ratherthanengineering thoserisksoutofthesystem. •Designers overlyoptimistic abouteaseofground operation ofequipment. Summary ofConclusions •Engineering controls arebestwaytomanage theriskoffailure. Design failuremodes outofthe equipment. Don'trelyonprocesses, procedures, ortraining tomanage failuremodes. Directcontact withtheend-user ispreferable tocommunication through thirdparties, orinstruction manuals. Giventhemagnitude oftheIddium project, specific on-siteinstruction inresetting theunits wouldhavebeenagoodidea. Thereisnoreplacement forawellthought outFailure Modes, Effects, andCriticality Analysis (FMECA) ofthefinaldesign, ratherthanatraditional reliability analysis. Askthequestion "howcould thisdevicefail?" •Ground operations mustbeconsidered inoverallreliability, inaddition toon-orbit operation. •Consider "human factors". Manuals arenotalways read,andprocedures arenotalways followed. Consider thisintheFMECA. 285