Inordertominimizecosts,thenumberofpeopleworkingonthespeedbrakes waskepttoaminimum.At anygiventime,nomorethanthreeengineerswereworkingonthespeedbrake mechanism andthey performedalargenumberoftasksincluding:design,modeling,analysis,drafting,projectmanagement, fabrication/integration/test support,testplanning,testfixturedesign/analysis. Mostcomponents were fabricatedout-of-house andwerethenintegratedatOrbital'sDullesIntegration andTestFacility.The system-level testingwasperformedattheall-movingverticaltailsubcontractor testfacility(Composite Optics,Inc.,SanDiego).Thesmallteamallowedforcommunication onadailybasisbetweenteam members.Theprimarydesignandanalysiswasperformedbythesameengineer.InkeepingwiththeX34designphilosophy, documentation waskepttoaminimum. Advanceddesignandanalysistoolswerealsousedtominimizecost.SDRCIDEASMasterSeries5was usedtoproduceasolidmodelofthemechanism, whichisshowninFigure6,thatallowedthecomplex threedimensional mechanisms tobefit-checked onthecomputerbeforepartswerefabricatedandno interferences werefoundwhentheactualhardwarewasintegrated. Inordertominimizetheneedforcomplexandtimeconsuming analyses,theX-34structuraldesign philosophy wastoproduceadesignthatwasrobustenoughtorelyonsimpleranalysesusingmore severeloadfactors.TheX-34programappliedsafetyfactorsof1.25foryieldand1.50forultimateto flightlimitlevels[4].Havingarobustlydesignedmechanism providedadditionalconfidence in implementing anaggressive schedule. Whereverpossible,components wereanalyzedusingsimplehandcalculations insteadofdetailedfinite elementmodelsornotanalyzedatallbutverifiedinasystemleveltest.Forexample,components with well-defined loadpathssuchascleviseswereanalyzedusingonlyhandcalculations, MathCad worksheets, andMSExcelandwerethenverifiedintest.Components withmorecomplexloadpaths suchasthepillowblocks requiredfiniteelementmodelinginadditiontotesting. Anothercostreductionmethodwasimplementing modulardesignwhereverpossible.TheX-34program mandatedtheuseofacommonhydraulicactuatorsincethisresultedinsignificantcostsavings.The actuatorwassizedforthehighbandwidthelevonsandrudderinstrokeandrate.Thespeedbrakes requiredaslowerslewrateandhadsmallerstrokerequirements, whicharesummarized inTable2.The stroke,force,andslewraterequirements werederivedfromstabilityandcontrolrequirements. Acommon pianohingedesignwasusedforallX-34controlsurfaces(elevons,bodyflap,andspeedbrake). The pianohingedesignwasselectedforitsinherentabilitytoserveasathermalbarrieralongthecontrol surfacehingeline.Thepianohingeassemblyitselfwasdesignedusingmodularcomponents inorderto savecostbyreducinguniqueparts.Thespeedbrake clevisesalsoaremodularinthattheyweredesigned tobeusedaseitherrighthandorlefthandpartsrequiringhalfasmanydashconfigurations onthe drawing.Inordertomaintainoperational flexibility,allX-34controlsurfacesweredesignedtobefully interchangeable. Itispossibletoexchangesurfacesfromvehicletovehicle.BoththeSN001andSN002 all-moving verticaltailshavebeeninstalledontheA-1vehicleatdifferenttimes.Inthecaseofthe speedbrakes, thismeantusingmatchedtoolingtodrillthehingelineboltpatternsoneachserialnumber oftheall-movingverticaltailandspeedbrakes. Table2.Actuator Design Specifications vs.Requirements Inboard ElevonRequirement Outboard Elevon Requirement BodyFlapRequirement Rudder Requirement Speedbrake Requirement Common Actuator Design SpecificationStroke Force 128mm(5.061in)4,762kg(10,500 Ib) 95mm(3.878in) 4,762kg(10,500 Ib) 106mm(4.195in) 3,815kg(8,411Ib) 62mm(2.466in) 2,296kcj(5,063Ib) 114mm(4.506in) 5,546kg(12,227 Ib) 180mm(7.100in)10,069kg(22,200 Ib)SlewRate 45°/s 45°/s 30°/s 45°/s 30°/s 45°1s Ahighdegree ofconcurrent engineering wasemployed intheexecution ofthespeedbrake mechanism design. Itwasnecessary torelease partsforproduction withminimal analysis inordertomaintain schedule. Whenproblems didoccur,itwaspossible toretrofitsolutions intotheexisting design. 67