ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Withtheproperspringanddamperparameters obtained,thenextstepwastousethosevaluesina DADSmodeloftheentirespacecraft. Thismodeliscomprised ofabus,twowingswithsixsolarpanelson each,thewingdeployment staggering mechanism, andotherfeatures torepresent therealistic natureof thedeployment behavior. Onesuchfeature aretwo"mousetrap" springs, orarticulation fingers, oneach wingbetween theouterpanelstocontrolrelative panelmotionandspeed(seeFigure9).AnAVIformat animation fileexistsinReference 2thatshowsthesolararraydeployment event,fromthefullystowed to thefullydeployed configuration. O=4-hinge line Articulation G=3-hinge line Fingers O=2-hinge line Core Plate Figure9.HingeandArticulation FingerLocations onSpacecraft (Courtesy ofOrbital Corp) Results Intheanalysis, thesecond wingisreleased after25seconds, ratherthan60seconds, whichwas arbitrarily chosen whentheprogram decision needed tobemade.Ithasbeenproventhatkeeping the60second delaywasnotonlyprudent andconservative, butitalsoprevented theneedforadditional software changes atthatlatedateintheprogram schedule. Therewereotherminorissuesuncovered through theuseofthismodelthatmightneverhavebeen rectified otherwise. Thebiggest issuewasthefactthatthearticulation fingerthatcontrols thetwoouter panelsclosest tothespacecraft centerline (theupperonepointed outinFigure9)wasineffective onthe staggered wing(andmaybeboth).Thosepanelsseparated approximately 25.4cm(10inches) atthetips, andthespringfingerisonlyafew(5-8)centimeters long.Thereason fortheseparation isthefactthat theirrespective innerpanels, whendeployed, arenotplanar, butinstead forma12-degree anglewith eachother. Twooutoffourofthesearticulation mechanisms thatareusedtokeepthepanelsunderasemi-controlled deployment wereshowninthemodeltolosecontact withtheirrespective panels. Depending ontheactual levelofvariability inthehingetorque, theleading panelcanbecome thelagging panelduetoalossof contact. Ifthatoccurs, themousetrap springwouldinterfere withthelatch-up ofthepanels, muchlikea broomstick across adoorjamb wouldprevent thedoorfromfullyclosing. Thehardware wasevaluated priortoflightanditwasdiscovered thatthefingerswereplacedinthewronglocations, tooclosetothe outboard tipsofthewings. Basedonageometric calculation, theywererelocated toamoreeffective location furtherinboard alongtheirrespective hingelines. Alsoduetothe12-degree offsetbetween thesepanels, itwasdiscovered thatthislocation hasthe potential forcreating thesamere-contact scenario asbetween thetwodeploying wings,whichwassolved 233
byaddingthestaggering mechanism. Sincethatsolutionisnotfeasibleinthislocation,engineers discussedaddingfoamtotheareasthatcouldpossiblycontact;however,itisunclearwhetherthe contractoreverincorporated thisfeature. Atthispoint,theteamreflectedbackonthefivemajorquestionstobeansweredattheoutsetofthis project,andassembledthefollowinganswers: .Howlongshouldthedeployment staggering devicewaittorelease thesecond wing? TheDADSmodelpredicted thatthevibrations ofeachwingweresufficiently settledafterapproximately 25seconds. Itisbelieved thatkeeping theaccepted 60-second delaywasnotonlyprudent andconservative, butitalsoprevented the needforadditional software changes atalatedateintheschedule. Does2_dwingdeployment causea'?all-wagging-the-dog" disturbance sufficient tounseatthe1st deployed wing? No.Thedeployed wingandjointstiffness issufficient topreclude contact between panelsondifferent wingsduringdeployment. ,Doesover-travel ofeitherwinginduceexcessive bending stressinthepanelsorspacecraft core plate? No.Themaximum moment caused bythecoreplateinterference was6.2N-m (55in-lb)forbothwings.Although thismayappear counter-intuitive sincethe wingsdeployslightlydifferently, itisbecause thefinal,roll-out motionisnearlythe sameforboth,withthesamemoments ofinertiaandverynearlythesame speeds. Acalculation wasdone,applying thismoment totherootpanelinordertoseethe effects. Thestressinduced inthefacesheetsresulted inlessthan6.2MPa(900 psi),maximum, andthecorresponding overall facesheetelongation dueto bending isabout0.01mm(0.4mils)-hardlyworthaconcern, giventhe compliant adhesive usedtobondthecellstothepanels. .Willanyotherpanelover-travel (withinaparticular wing)causedetrimental contact ofdeploying solararray? Possibly. Duetothenon-planar natureofthe12-degree offsetattwohingelines,it wasdiscovered usingtheDADSmodelthattheselocations havethepotential for creating thesamere-contact scenario asbetween thetwodeploying wings,the latterofwhichwassolvedbyaddingthestaggering mechanism. 5.Docoreplatesoftstopsnecessarily prevent detrimental over-travel ofthedeploying solarwing? No.Duringthetest,therewaslittleornoeffectgivenbyrubberfoamplacedalong theedgeofthecoreplate.Infact,itactually appeared asthough alar_erovertravelanglewasexhibited withthesoftstoppresent. Thereisnoexplanation for thisphenomenon, exceptforthepossibility thatthefoamslowstheinnerpanelat theendofitstravelrange,thuschanging thedynamics ofthewingasawhole.It wasreadilyseenusingtheDADSmodelthattheinteraction between thetwo panelsofasinglewingcanhavealargeimpactontheover-travel angle. Conclusion Theforemost conclusion brought aboutbythisentiretaskisthatitisdesirable todesignasystem thatcan betestedonEarthsotheextensive methodology discussed hereinisnotnecessary. However, itisnot always possible todoso,andinthoseinstances, ithasbeenshownthatiterative correlated testand analysis CANwork.TheTSX-5program accepted manyitemsbasedonthisprocess: 234
Thewingstaggeringmechanism anditstimedelay ;_Theplacement /relocation of"mousetrap" articulation fingers _*Theremoval offoamonthecoreplateduetolackofneed Thelackofdetailed FEMmodeling forsolarcellcracking atend-of-travel Itshouldbenotedthatthesupport ofmanagement toexecute propertestingisessential inthisprocess, because ifthismethodology ischosen, onemustremember thatthecomputer modelisonlyasgoodas thedatagoingintoit.Although thismaynotbearevelation, itisindeedonemorevalidargument proving theneedofanextensive ameaningful testingprogram. Theultimate proof?TSX-5successfully deployed itssolararrayon-orbit June7,2000... @ Lessons Learned _,Design asystem thatcanbeeffectively testedwithinEarth's gravitational field Whenusinganairbearing system, ensure sufficient stiffness laterally (sopaddledoesn't cock over)andprovide foradjustment vertically. Inareasofpossible hardware contactJcollision, testconfiguration withrubber/foam/etc, installed, sinceitmayhavedramatically different effectsthanexpected. Test,Test,thenTestsomemore... Acknowledgements Theauthorwouldliketoexpress extreme gratitude towardWalter Holemans, whodesigned thesubject hingewhileatOrbitalanddisplayed anenergetic andunwavering commitment toexcellence throughout thisentireprocedure. Afterleaving Orbital, Walteractedasagratisconsultant inordertoensure thiswork wascompleted. Itshouldalsobenotedthattheseeffortswouldnothavebeenpossible without Orbitars technical expertise provided byMichael Whalen andmanagement support provided byPatDavis.All illustrations oftheTSX-5spacecraft usedherein(Figs.1,3,&9)arereprinted withthepermission of OrbitalCorporation. References 1,Daniel,WalterK.,andBidinger, G.Michael, "Deployment Dynamics ofSolarArrayswithaLink-in-Slot,fh Hinge/Latch Mechanism,' 34Aerospace Mechanisms Symposium, May2000. 2.TSX-5spacecraft website athtt.p://www.te.plk.af.mil/stp/tsx5/craft/craft.html 3.Holemans, WalterandGore,Brian,"TSX-5 SolarArrayDeployment TestPlanandReport," October 1999. 235
Deployment TestAnomaly TheBoomdidnotfullydeploy intestbecause aninterference occurred between testhardware representing theL-bracket ontheFSSAandtheSolarArrayRelease Mechanism (SARM) bracket onthe vehicle bus.Thisinterference haltedthedeployment andleftthesystem stuckinahalf-deployed position. Inanominal deployment, theBoombeginsinitsstowed position (Figure 6).Duringthefirstpartofthe deployment, theTMallowstheinboard hingetotravel9°beforethetripwire cableispulledtaughtand haltsthemotionoftheinboard hinge(Figure 7).Theoutboard hingethenrotates 114°(Figure 8)atwhich pointthetripwire cableslidesoffofthehook(Figure 9).Atthatpoint,bothhingesarefreetodeployand thedeployment continues totheend(Figure 10).Intheanomalous deployment, theinboard hingedidnot travelitsinitial9°andthetripwire cableneverslidoffofthehook,thuscausing thetwobrackets to interfere withoneanother (Figure 11).Insufficient inboard hingerotation wascaused byexcessive friction intheTM.Duringdeployment tests,aTMdesignated asatestunitwasused.Thistestunithadbeen usedsincetheinception oftheprogram andhadneverbeenrefurbished. Friction increased overtimeand ultimately prevented theinboard hingefromrotating enough tocleartherelease mechanism bracket. Similarly, awornhookandaworntripwire cablecaused thetripwire tonotrelease fromthehook. Thistestanomaly ledtoamorein-depth investigation thatrevealed thatthedeployment designmargins tofriction couldbeimproved. Elevated levelsoffriction intheTMcomponents couldleadtoanon-orbit deployment failure.Thispotential interference hadnotbeenrecognized asaproblem beforethisincident. Toensure thatthefriction levelswereminimized, theTMcomponents wereredesigned andnewtest procedures werewrittentoverifythatthecomponents metthenewfrictionrequirements. i 17icmI //  ! FSSA VehiTle ,Outboard Hinge _Cable ISA_RMLB:_:::: t Figure1.BoomandFSSAinStowed Position 238
CauseofTestAnomaly TheBoomdeployment anomaly wascaused byexcessive friction intheTMcomponents. The components usedduringthetestweredesignated asnon-flight Special TestEquipment (STE)andwere usedduringeverydeployment test.Aseparate setofflightTMcomponents isreserved foreachvehicle andtheyarenotusedforBoomdeployment tests.Theproblem wasthattheSTEcomponents hadbeen subjected toapproximately 100deployment cycleswithout everbeingrefurbished. Inspection oftheSTE TMcomponents revealed significant signsofwear.Thiswearcaused twothingstohappen. One,the tripwire wasnotabletocompletely payoutoftheSTETM.Andtwo,thetripwire wasnotabletorelease fromtheSTEhook. TMWashers TheTMconsists ofthreespoolsmounted onanaluminum chassis (seeFigure4).Thecentral spool contains thetripwire cable.Thetwosmaller spoolscontain thesprings thatprovide thetension forthe tripwire cable.Allthreespoolsaremounted tothechassis byashoulder boltandnutcombination. In ordertoprovide aredundant rotating surface between theshoulder boltandthechassis, awasher was addedtothebearing surface. However, likethechassis, thewasher wasmadefromaluminum and created anidealsituation forgalling tooccuraslikematerials werebearing upononeanother. Furthermore, itwasdiscovered thattheSTETMwasassembled incorrectly asthewasher wastrapped undertheshoulder bolt.Instead ofbeingfreetorotate,thewasher waspinched between theshoulder boltandthechassis anddamaging itselfandthechassis witheachsubsequent cycle(Figure 12and Figure13).Thefriction created bytheimproperly installed washers andtheimproperly selected washer material weresignificant reasons astowhythetripwire didnotcompletely payoutoftheSTETM. Figure12.Pinched Washer Figure 13.Galling Caused byWashers TMExitHole Asthetripwire cableunwinds offofthecentralspool,itexitstheTMthrough asmallholeinthechassis. Duetothegeometry ofthesystem, thetripwire cableispulledtoonesideoftheexitholeandmakes contact withthechassis asthecableispulledoffofthespool.Sincethecableisstainless steelandthe chassis isaluminum, thecableactedasasawandcutasignificant groove intothesideoftheexithole (Figure 14).Thisgroove inhibited themotion ofthecableandcontributed tothetripwire notcompletely payingoutoftheSTETM. iiii,i....___C_:__ ._ Figure14.Groove CutinTMExitHole 242
Tripwire Cable Uponexamining theSTEtripwire cable,kinkswerefoundinthesection ofcablethatfeedsthrough the exitholeintheTM(Figure 15).Intheanomalous deployment configuration, oneofthesekinkswas located inthegroove thatwaswornintheexitholeoftheSTETM.Additional forceisrequired topull thesekinksthrough theexitholebuttheBoomwasnotcapable ofproviding thisextraforce.Therefore, thetripwire cablewasnotallowed tocompletely payoutoftheSTETM. Figure15.KinksinTripwire Cable Hook Thefinalpieceofthepuzzlewasthehook.LiketheTMchassis, thehookwasalsomadeofaluminum. Whenthestainless steeltripwire cablewasdragged overthealuminum hookrepeatedly, agroove was cutintheSTEhook(Figure 16).Withapristine hook,thetripwire cableshouldslideoffthehookata hookslipangleof12degrees. Withthegroove cutintheSTEhook,thetripwire neverreleased fromthe hookeventhough thehookslipanglewas43degrees. Subsequently, thiscaused themotion ofthe inboard hingetoberestrained longerthannormal. Figure 16.Groove CutinHook Corrective Action Because thedeployment anomaly wascaused byworncomponents, fixingtheSTEsystem wouldhave simplyrequired replacing thewornpartswithnewparts.ButtheSTEcomponents duplicate whatisused ontheflightvehicle, sotheanomaly prompted thedesignteamtodetermine thesystem's sensitivity to TMfriction. Therefore, thegoaloftheinvestigation wastonotonlyfixtheproblem buttoensure thatthis anomaly wouldneveroccuragain. 243
cm(13.6in)andthecablewasnotallowedtoslideoffthehook.Themodelalsomatchedthe43-degree slipanglethatwasheldwiththecabletrapped inthegroove. Figure17showsaclose-up ofthehang-up, aspredicted bythemodel. J f /.-_"_:1 tripwire , . \\,,,Oslip=43deg/,,, // zPUbSo_tn" "_ /// simulator [--_ hook ""'"'_. Figure17.Close-up ofPredicted Bracket Hang-up Manyinputstothemodelwerevariedbetween theirnominal andworst-case valuestodetermine their effectonclearance between theSARMandLbrackets. Someparameters required betterdefinition and, insomecases, prompted newcomponent teststodetermine nominal andworst-case values. After several iterations ofmodelprediction andparameter refinement, itbecame clearthatthetripwire hook force(similar tothearrowforceonabowandarrow)andhookslipanglewerecriticaltoclearance. This ledtoapass/fail requirement forthetripwire of15.6N(3.5Ib)maxhookforceatahookradiusof31.0cm (12.2in).The31.0cm(12.2in)radiusrepresents minimum payoutthatensures astaticbracket clearance of2.5cm(1.0in).Morepayoutisneeded fordynamic clearance, depending ontheslipanglethatthe tripwire releases at.Thisisbecause thebrackets arestillapproaching oneanother evenafterthetripwire hasreleased. Aftertripwire release, therelative strength anddamping atinboard versusoutboard hinges affects theminimum clearance. Thehookslipanglepass/fail wassetat20degrees. Theprocess of quantifying theparameter valuesandcorrelating themodelledtosomediscoveries. Oneofthediscoveries wasthatthedeployment duringthecolddeployment anomaly wasgreatlyassisted byatestharness thatwastie-wrapped tootightlybetween thesupport postandtherotating offloadbeam. Figure18showsthelargeaidingtorqueandfrictioncaused bythetestharness whencomparing the6/5 testwithlatertestswherethetestharness wasre-routed. Oneofthefunctions oftheBoomistotransfer powergenerated bythesolararraytothevehicle. Thisis accomplished byutilizing alargecableharness thatisapproximately 5.0cm(2.0in)indiameter. This thick,stiffcableharness isroutedovertheinboard hingeandmakes thehingeharder todeploy. Typically, acableharness aidsdeployment forroughly thefirsthalfofdeployment thenstartsresisting thereafter. Theaidingtorqueatthestartofdeployment isusually similar inmagnitude totheresisting torqueattheendofdeployment. Bycomparing thetestsafter6/5tothehinge-only testinFigure18itis clearthatthisharness resistsdeployment through most,ifnotall,ofdeployment. Thisisconsistent with theresultsduringdevelopment testsoftheharness. Therefore, theroutingandtie-wrapping ofthecable harness, asdesigned, tendstoreducethedeploytorqueandthus,theclearance between thebrackets. 245
A ii c E o c°i Z o r-400 350 300 250 200 150 100#1009ColdDeploy Data ........................... 6/5deploy ----e---- 8/22deploy -+ 8/31deploy .:-9/25startdeplyd 10/3startstowed _--.._ "_:o..... ---o-.- hingeonly ]....... __:._...._._. •.................. "....£r_._-_+_q......o_=:_._............ 0 10 20 30 40 50 60 70 80 90 Inboard Deploy Angle(deg) Figure18.Comparison ofDeploy Torque overVarious TestsonaSingleBoom Comparing the9/25and10/3results inFigure 18showsthatthecableharness takesasignificantly different setdepending ontheBoomorientation duringcooldown.IftheBoomiscooled initsstowed position, thecableharness takesacoldsetinthatstowed position andsignificantly decreases the available torqueofthehinge,compared tothetorquewhenthecableiscooledinthedeployed position. Thestarting orientation oftheBoomwasnotprecisely specified duringtesting, andatleastonetorque margin testisknowntohavestartedfromthedeployed position instead ofstowed. Another discovery wasthelargeunit-to-unit variation ininboard hingetorque. Figure19showsthedeploy torquemeasured fromseveral Booms. Simulation oftheBoomswithlowertorquevaluesshowsthatthere isverylittleclearance margin evenaftermatching theweakest tripwire tothatBoom. Theonly requirement leviedonthetorquetestsistodemonstrate 100%minimum torque margin, whichallthe Booms inFigure19(without thetripwire) possess. 246
ColdDeploy Data-AllBooms 350 300 I e,- E25o0 p. _3c _.200 0 ¢150 100 0 10 20 30 40 50 60 70 80 90 Inboard Deploy Angle(deg) Figure 19.Unit-to-Unit Variation inInboard Deploy Torque Athirddiscovery isthatthetorquemargin oftheinboard hingewhilethetripwire isengaged wasnot performed atthebeginning oftheprogram. Withthetripwire engaged, thetorquemargin oftheinboard hingeiswellbelowtheprogram requirement of100%.Atfirstglance, torquemargin mightseemirrelevant heresincethepurpose ofthetripwire istoholdbacktheinboard hingetemporarily. However, theinboard hingemustdeploy theBoomsufficiently tomaintain clearance fortheoutboard hingeasitdeploys. Failure oftheinboard hingetoprovide thisclearance results inahang-up asseeninthedeployment anomaly. Therefore, thetorquemargin mustbeatleastgreater thanzerothrough somepayoutdistance ofthetripwire toprevent ahang-up. Thetorquemargin mustbelargeenough toaccommodate variations inthetripwire forceamong others.AstheSTEtripwire forceincreased withwearthetorquemargin ofthe inboard hingedropped. Therefore, atorquemarginanalysis earlyonmighthavetippedthescalesagainst usingatripwire byhighlighting theBoom's sensitivity toit. Thetorquemargin fortheBoomdepends onthetrajectory because therearetwodegrees offreedom in theBoom,thetwohinges. Aminimum torquemargin of50%wasdetermined atfirst,basedonastatic analysis oftheBoomwherethetripwire payout wasadjusted tomaintain 2.5cm(1.0in)ofclearance between brackets forallachievable hingeangles. Thismethod wasdropped because theclearance continues todropforaperiodafterthetripwire isreleased. Thecurrent analysis method determines torquemargin directly fromtheworst-case dynamic clearance simulation foreachBoom.Thisanalysis indicates thatatorquemarginof38%whenthetripwire isreleased isneeded toprevent ahang-up during adynamic deployment. Thisnumber islowerthantheearliermethod because thetripwire ispaidout furtherinthedynamic analysis andcreates alargerresisting forceontheinboard hinge. Afourthdiscovery duringthisanalysis wasthatthedeadband inthedampers isasignificant factorfor clearance, andthestowing procedure influences theamount ofdeadband available forthenext deployment. Atthebeginning ofhingemotion, theBoomaccelerates awayfromtherelease bracket 247
maydecreasesignificantly, especiallyatcoldtemperatures. Unlessthedeployment marginislarge,use theminimumnumberoftie-wrapsortapethatwilladequately controltheworkingspaceanddynamic motionofanyharnesses crossingadeployable joint,andcontroltheroutingandconstraining ina drawing. Andfinally,specialcareneedstobetakenwhendesigningtestequipment. Requirements fortest equipment aren'talwayslessdemanding thanforflightequipment. Inthiscase,alloftheSTETM components passedtheircomponent test.However,thiscomponent testwasdesignedwithflight hardwarerequirements thatassumedthattheTMcomponents wouldseerelativelyfewcycles.However, theTMcomponents weresubjectedtoover100cyclesatthetimeoftheanomaly.Inaddition,theTM wasnottestedinthe(bowandarrow)geometrythatisseenatthesystemlevelwherethehighestforces andwearoccur.Thedesignteamneedstoconsiderthattestconditionscanbemoreofadesigndriver thantheactualflightconditions. Conclusions Thewear-out failuremodeoftheBoomtestequipment hadapositive outcome inthatittaughtthedesign teammanyvaluable lessons. Theselessons werelearning howtoimprove testequipment inspection procedures, realizing theimportance ofin-depth testingofeveryunit,recognizing thevalueofanalysis as adesign tool,learning thatcablerouting isacriticalvariable, andunderstanding thefactors thatare involved intestequipment design. Butthemostimportant outcome ofthedeployment anomaly wasthatit ledtodesign improvements thatincreased Boomdeployment margins. Apreviously unknown pointof failurewasquickly remedied, thusimproving theprobability ofsuccess inSolarArrayBoomdeployments fortheremaining Milstarsatellites. 249
/ The"Curwin ©''Design: ANovelSolarArrayConcept forConstellations HenkJ.Cruijssen* andGerardJ.A.N.Kester* Abstract WithinFokker Spaceastudywasundertaken duringtheperiod1998to1999toinvestigate solararray designs forinstance fortheconstellation markets. Incloseco-operation withBoeing andMMS(now Astrium), several solararraydesignoptions wereinvestigated fortheTeledesic andCelestri programs but alsootherfutureinitiatives couldbenefitfromourstudyeffort.Oneofthesolararrayconcepts studied in moredepthwasthe"Curwin©''solararray.Thispaperdiscusses theevaluations made,whichhaveledto thisnovelconcept. Also,thepreliminary performance characteristics areprovided. Abreadboard modelat 50%scalewasmadetocorrelate hardware withthetheory. Abriefoverview isgivenofthebreadboard testresults, Introduction Forconstellations, itismandatory tokeepthetotalsystem costdown.Therefore, thelaunchcostsareto bedecreased, forinstance byimplementing multiple launch options. Forthisreason, thetightstowage volume requirement forthesolararrayimplies aconsiderable design driver. Forfuturespacecraft concepts, thismayberequired aswell,asthepowerdemand isexpected toincrease whereas the available stowage volume maybecome critical. Figure1.Curwin solararrayinfullydeployed configuration withpanels curved (rearview) *FokkerSpaceBV,Leiden, TheNetherlands Proceedings ofthe3_hAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 251
SolarArrayTechnical Requirements Thefollowing tableprovides thetechnical requirements. Theserequirements werenotfirmandchanged several timesduringthecourse ofthestudy.Theseweretriggered bythemerger between theTeledesic andCelestri project, whichresulted inanincreased powerdemand. Table1:Majortechnical requirements (typical forconstellation typesolararrays) Parameter PoweratEndofLife(EOL) conditions Drop-off orbit Operational Orbit Lifetime Architecture Volume Overall Masstarget(specific) Maxdeployed area/Moment ofInertia Suntracking mechanism FieldofView Stowed resonance frequency Deployed resonance frequency Deployment shockTeledesic 4.3'kWlaterincreased to8.4kW ~300km 1375km,i=84.7° 9-10years 2wingsonacentralextension armfromtopsideoftheSIC 250mmtapering offto150mm >35W/kg N/A Double rotation axisSADM / gimbalmechanism Visuallineofsight/contact with theneighboring S/C fl>35Hz fl>0.3HzCelestri 7.6kWupto8.4kW -300km 1375km,i=48° 12years 2separate wingsonayoke fromeithersideoftheSIC 250mmheight >35W/kg. Lessthan10500kg-mz Double rotation axis/gimbal nodetailsavailable fl>40Hz Firstmodetobefl>(6/I)U_ withI=inertia N/A <TBDN-m Ahighdegree ofdesign commonality wasstrivedforfromthebeginning ofthestudy.Forboththe Teledesic /Celestri solararraythishasleadtothefollowing technical designdrivers End-of-Life (EOL)power(4.3kWupto8.4kW). Stowage volume onspacecraft (S/C)(150mmtapering to250mm) Deployed resonance frequency fl>0.3Hz Deployment trajectory toreachthefullydeployed configuration mustbecontrolled andwithin certainconstraints (i.e.stay-out zones) Totalsolararraymass(>35W/kg) Fieldofviewandmoment ofinertiaindeployed configuration Specific Proqrammatic requirements: Typical programmatic constraints wereimplemented toverifytheproposed technical designs against the schedule andcostconstraints. ;-Development schedule: firstdemonstration launchin2003,thereafter regular launchrate ;*Launch rate:everyweekonelaunch, resulting inadelivery rate:onearrayper2weeksfor Celestri (maximum case):onearrayper2working daysforTeledesic (maximum logisticcase) Non-recurring cost:TBDtoinitiateandendorse toamaximum extentlowering oftherecurring cost,recurring cost:<$1Mperarray.(4.3kWEOL),basedonaproduction lotof180satellites to beproduced in4years 252