ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
26.42kPa(552psf),3,767N-m(33,338in-lb)ofhingemomentisgeneratedoneachspeedbrake panel. Theresultantnormalforceoneachpanelis17,263N(3,881Ib).Theresultantaxialforceoneachpanel is5,698N(1,281Ib).Theresultantspeedbrake actuatorforceis54,388N(12,227Ib)whichcorresponds toa1,959N-m(17,342in-lb)momentonthetorquetubes. Table1.Speedbrake LoadCases Ascent_sb 75°Mach 1.25 Entry 90° 6.60Q HM FN 26.42kPa 3,767N-m 17,263N (552psf) (33,338 in-lb) (3,881Ib) 15.61kPa 1,417N-m 6,494N (326psf) (12,543 in-lb) (1,460Ib)FA 5,698N (1,281Ib) 2,144N (482Ib) Thesurface motion requirement forthespeedbrakes is0°to90°and+/-10°fortheall-moving vertical tail.Theslewraterequirement is30°/sforthespeedbrakes and45°/sfortheall-moving vertical tail.In addition toloads,thequalification temperature requirement forthecomposite speedbrake is176°C (350°F). Thermal blankets andbarriers areusedtokeepthecomposite structure belowthislimit.The speedbrakes arerequired tobeinterchangeable between airframes [4]. Constraints Thetailcrosssection geometry wasconstrained bytheneedtofitwithinthecavityinthefuselage ofthe L-1011 carrieraircraft. Thiscavity,whichwasoriginally designed tohousethePegasus vertical fin,was modified toaccommodate theX-34all-moving vertical tailandwaskeptassmallaspossible tominimize structural modifications totheaircraft. Because thetailisactually embedded withinthefuselage ofthe carrier aircraft, thetailcanpotentially impact thecarrier aircraft duringtheseparation sequence. Extensive dynamic analyses wereperformed inordertoverifyadequate clearance between thetailand thecavityexisted forsafeseparation. Figure3showsthepathofthetailrelative tothecavityin0.10s intervals afterseparation fromthecarrieraircraft. Anareaofthespeedbrake wasactually truncated atthe intersection ofthetrailingedgeandtipchordinordertoincrease theclearance margin between X-34and theL-1011. Thetailcrosssection geometry wasalsoconstrained bythedesiretohaveasthinatailas possible inordertominimize dragduetoflowseparation duringtransonic andsupersonic flightofX-34.A tailcrosssection wasselected (tic=17%)thatwaslargeenough toaccommodate thespeedbrake mechanism butstillfitwithintheL-1011 cavity. Astiffness constraint isderived fromtherequirement thatallcontrolsurfaces onX-34beflutterfree.This constraint drivesthedesignofmostofthespeedbrake components. Costandschedule constraints are derived fromtheoverallX-34program costandschedule allocations setatthebeginning oftheprogram. Theseconstraints drivetheexecution ofthedesignintermsoftheuseofasmall,highlyefficient team, modular/common components, simplified assembly tooling, robustdesigns, andadvanced design and analysis tools. 59
80 60 I,° 0 I20 -4O 56OL-1011 _ = 560600620640660680700 FORE-AFT RESPONSE (INCHES, Positive right)100 PathofTail__ AfterSep(.10sintervals) 8o i,° 720740L-1011 Envelope r 7 0 -20 -40 -20 0 20 40 LATERAL RESPONSE (INCHES, Positive right) Figure3.TheAll-Moving Vertical TailwasConstrained bytheL-1011 Envelope Volume Constraint Thedesign oftheX-34speedbrake mechanism demonstrated thatitispossible todesign acompact control surface deployment mechanism tofitintoasmallvolume. Thelimitedvolume available forthe mechanisms (defined bythetrailingedgeoftheall-moving vertical tailandtheinnermoldlinesofthetwo speedbrake panels) required thatthemechanism beverycompact. Figure4showsviewsofapartially integrated speedbrake mechanism intheopenandclosedposition aswellasadepiction oftheavailable volume forthespeedbrake mechanism. Available Volume forSpe:dbra:e---_. /;I_ if Figure4.TheSpeedbrake Mechanism wasConstrained bytheSpeedbrake Panels andTail Thespeedbrake mechanism consists ofaspeedbrake hydraulic actuator, speedbrake actuator clevis, crankarm,crankarmclevis, drivelinks,scissor links,torque tubes,pillowblocks, pianohinges, 6O
speedbrake clevises,andspeedbrake panels.Aschematicrepresentation ofthemechanism isshownin Figure5andasolidmodelrepresentation ofthemechanism isshowninFigure6. PianoHinge-_ Hydraulic __Crank ArmPillow Actuator__)1_ Block .// _ CrankArm ,,//_ _l_kfOlevis _  _wr,t Drive I,f.,llll_'l_ __'IB_ Link ToTorque Scissor _-Actuator Clevis Tubes LinkSpeedbrake _(//----Panel "qK_._._J Speedbrake Clevis TorqueTube ViewLooking Starboard ViewLooking DownRudder Trailing Edge Figure5.TheKinematics oftheSpeedbrake Mechanism isShown inThisSchematic Themechanism isactuated byasinglelinearhydraulic actuator located withintheall-moving vertical tail. Theactuator waslocated withinthetailinordertokeeptheactuator ascloseaspossible tothe speedbrakes whichreduced mechanism complexity andweight. However, hydraulic feedandreturnlines hadtobepassed upthetorqueshafttotheactuator. Swivelfittingsatthebottomoftheshaftarerequired toadaptbetween therotating shaftandthefixedfuselage. RudderBrace Speedbrake Assembly Clevis ueTube Speedbrake Actuator Speedbrake Clevis Link Actuator DriveLink Rib CrankArm Clevis PillowBlock Figure6.TheSpeedbrake Mechanism Consists ofMultiple Components Tosimplify hydraulic systems design, operations, andcost,identical actuators wereusedforallcontrol surfaces (elevons (4),bodyflap(2),rudder(1),speedbrake (1)).Asaresult,thespeedbrake mechanism actuator wasoverdesigned inslewrateandstroke.Thebodydiameter oftheactuator couldhavebeen 61
smalleriftheactuatorwasoptimizedforspeedbrake requirements. Thespecifications ofthecontrol surfaceactuatorsarediscussedfurtherintheCostandScheduleConstraints sectionofthispaper. Theactuator'sbodydiameterdrovethespanwiselocationoftheactuatorintheall-movingverticaltail. Theactuatorwaslocatedasclosetothetipchordoftherudderaspossible whilestillmaintaining clearance totheinnermoldline(23.9mm(0.943in)skin-to-cylinder clearance). Theuseofgraphite epoxymonocoque sandwich panelconstruction allowed forlargerribspacing thantraditional metallic semi-monocoque skin-stringer construction sincesandwich panelconstruction hasagreater specific stiffness. Thelargerbayspacing (457mm(18in))allowed formoreroomintheactuator bayforthe hydraulic systems. Thespeedbrake actuator hydraulics areshowninFigure7. Thespeedbrake actuator isattached toaribontheall-moving vertical tailwithastainless steelclevisand astainless steelcrankarm/clevis sub-assembly attached totheaftsparofthetail.Whilethedesignofthe stainless steelfittingsisconventional, theattachment ofthefittingtothegraphite epoxystructure required careful consideration. Inordertotransfer theactuator loadintotherib,itwasnecessary tothicken therib facesheets locally, addmetallic thru-bushings toprevent bearing failureinthefacesheets, andadda stainless steelbacking platetoprevent fastener pullthru.Similarly, localdoublers andabacking plate wereaddedtotheaftspar.Arudderbraceassembly wasalsorequired toreduce loading intotheskin-tosparjointsbytransferring aportionoftheloadtotheribabovetheactuator viaapairofstainless steel struts.Thesereinforcements weremadelateinthedesign/analysis phasebutwereeasilyaccommodated withintheconcurrent engineering environment. Theabilityoftheconcurrent engineering environment to handletheseadditions isdiscussed intheCostandSchedule Constraints section ofthispaper. Minimum Clearance_ Figure7.TheSpeedbrake Actuator wasLocated asClosetotheTipChordoftheRudder as Possible Thecrankarm/clevis sub-assembly isconnected viatwoscissor linkstothetorquetubes.Thescissor linkshavespherical bearings ateachoftheirendstoadaptbetween themotionintheplaneofthecrank armandthemotion inthedifferent planes ofeachtorque tube.These'narrow' profilebearings (PIN M81935/4-8) werenottypically stocked byvendors andrequired leadtimesinexcess ofninemonths. Vendors didstock'wide'profilebearings (PINM81935/1-8) butthesebearings werelesscompact and hadalowerloadratingthanthe'narrow' profilebearings. (Twoshipsets of'narrow' profilebearings were located afterseveral weeks ofsearching.) Thetorquetuberotation axesareparallel tothehingeline rotation axesforsimplicity. Thehingeline axesaredrivenbytheoutermoldline(OML)oftheall-moving vertical tailwhichissweptaftandtapersfromroottotipchord.Asaresultofthissweepandtaper,the torquetubesarenotparallel toeachotherbut'toe-in'towards thetipchord.Because ofthis'toe-in'and because thediameter ofthetorquetubewasdrivenbystiffness concerns (discussed intheStiffness 62
Constraintsectionofthispaper)andbecauseoftheseverevolumeconstraintonthemechanism, the outputarmsofthetorquetubesarenestedtopreventinterference. Minimum Clearance ,Ii/ PianoHinge--_(_ _ SkinPlane_,_I !':,.JJ_ _3 SidedPolygon !IB,ock _'_---Aft SparPlane Figure8.ThePillowBlockDesign wasConstrained bythePianoHinge Eachtorquetubeismadeupofthreestainless steelsections (totallength=1117mm(44in)).Theneed tominimize torquetubediameter forspacereasons necessitated theuseofathree-sided polygon section toconnect thetorquetubesections. Thepolygon section, showninFigure8,ismorespaceefficient at torquetransmission thanaconventional spline.Breaking thetorquetubesinthreesections alsoallowed foraone-piece pillowblockdesignasshowninFigure9because theindividual segments ofthetorque tubecouldbefitintothepillowblocksandthenassembled. Apillowblockislocated ateachendofthe torque tubeandatthetwojointsinthetorque tube.Thestainless steelpillowblocks contain maintenance-free composite bushings. Theminimum clearance between thepillowblocksandthepiano hingeis.50mm(0.02in).Duetothelimitedfootprint available ontheaftspartofastenthepillowblocks, itwasnecessary tofastenthepillowblockstothepianohingeboltpatternwhichislocated ontheskins. Whileitwasundesirable tohaveonecomponent fastened totwonearlyorthogonal planes, thiswasthe onlywaytofastenthepillowblocksadequately. Thedifficulties encountered whileintegrating thepillow blocksisdiscussed furtherintheCostandSchedule Constraints section ofthispaper. PillowBlockTube 3SidedPolygon (male) Torque PillowBlockTube 3SidedPolygon f(female) Figure9.TheUseofMultiple Torque TubeSections Allowed foraOnePiecePillowBlockDesign Theoutputarmsofthetorque tubesareconnected tothespeedbrake clevises viadrivelinks,The speedbrake clevises areattached tothespeedbrake panels. Sincethetorquetubeoutputarmsare 63
nested,thecorresponding speedbrake clevisesarenestedaswell.Theseclevisesemployamodular designwhichisdiscussedfurtherintheCostandScheduleConstraints sectionofthispaper.Thisclevis underwentseveraldesigniterationsinordertoachieveaworkablesolution.Inordertoachieveadequate stiffnessinthespeedbrake panels,ahoneycomb corethicknessof34.9mm(1.375in)wasrequired.At thatthickness,thelastthirdofthetrailingedgeofthepanelsrequiredtaperingtofitwithintheOML.In ordertomaintainasmuchfullheightcoreontheremainingtwo-thirdsofthepanel,a45°pandownangle waschosentoaccommodate thespeedbrake clevisesasshowninFigure10.Thiswastheonlylocation onanyofthecontrolsurfacesthatdidnotusethepreferred18°pandownangle.Withthe45°pandown angle,theinitialclevisdesignwasunabletodistributetheloadintobothfacesheets. Thisproblemwas discovered instaticloadtesting.Testingwashalteduntilanewcleviscouldbedesigned,fabricated,and integrated. Itwasnecessary toextendtheclevisinthechordwisedirectiontoaccountforthe45° pandownangle.Thisredesign/retest efforttookthreemonths. TaperedCore_ Fu,He h,18°Pan_  _  °  a°O°w° Speedbrake Panel 18°Pandown °°=o Figure 10.InOrdertoAchieve Adequate Stiffness, theSpeedbrake Panels Required theUseof45°Pandowns Thespeedbrake panels areattached tothetrailing edgeoftheall-moving vertical tailviathepiano hinges. Thepianohingeiscomprised ofmodular titanium leavesandastainless steelpin.Themodular designofthepianohingeisdiscussed furtherintheCostandSchedule Constraints section ofthispaper. Thespeedbrake mechanism hasbeenintegrated withnointerferences ontwoall-moving vertical tailsfor thefirsttwoX-34flightvehicles. Themechanisms werestaticloadtestedatthesystem levelduringthe all-moving vertical tailstaticloadtestbyapplying theflighthingemoment tothetorquetubesandallowing themechanism toreacttheloadintothetailstructure. Flighthingemoments werealsoapplied tothe individual speedbrake panels inseparate staticloadtests.Themechanisms havebeenverified viafit checks, functional checkouts duringflightsimulations inthehangar, ground vibration testing, andrunway towtestingatDryden FlightResearch Center. Stiffness Constraint Thedesign oftheX-34speedbrake mechanism demonstrated thatitispossible todesign acompact control surface deployment mechanism withadequate stiffness toprevent aerodynamic flutter.Itwas recognized thataerodynamic flutterofthespeedbrakes couldoccurifthestiffness ofthedeployment mechanism wasbelowacertain value.Afterlayingoutthespeedbrake mechanism usingtheavailable volume, preliminary handcalculations showed thatthestiffness ofthesystem wasinadequate toprevent aerodynamic flutter.Further investigation revealed thatalthough thespeedbrake panelsthemselves were thin(t/c=6%)duetothesevere volume constraints, theywerenottheprimary contributor tothe mechanism compliance sinceitwaspossible tomakethemstiffbyconstructing themwithgraphite epoxy facesheets overaluminum honeycomb core.Thehydraulic oilcolumn stiffness associated withthe 64
actuatorwasalargecontributor tothecompliance, butitwasnotpossibletoalteritsdesignbecauseof therequiredcommonality withtheothercontrolsurfaceactuators. Analysisshowedthatthenextlargestcontributor tothecompliance ofthesystemaftertheoilcolumn stiffnesswasthetorquetubes.(Thetorquetubesinitiallyaccounted for73%ofthespeedbrake mechanism stiffness.)Sincethetorquetubeswerelongandsmallindiameter,theirrotationalcompliance relativetotheothercomponents washigh.Inordertoreducethisundesirable compliance, thediameter ofthetorquetubeswasincreasedfrom25.4mm(1.00in)to38.1mm(1.50in).Thisincreaseindiameter reducedclearances betweencomponents (Figure8)butdecreasedthecompliance dramatically which increasedthespeedbrake mechanism stiffnessby58%.ThedesignwasfinalizedandgiventoStructural DynamicsResearchCorporation (SDRC),thefirmtaskedtoperformadetailed speedbrake flutter analysis. Figure 11.X-34atDryden FlightResearch Center priortoGround Vibration Testing, March1999 Figure12.Rudder andSpeedbrakes Instrumented withAccelerometers for Ground Vibration Testing SDRC's initialmodalanalysis predicted arigidbody'scissors mode'ofthespeedbrakes at17.135Hz.At thatfrequency, apotential flutterinstability existsforthelowsupersonic portions oftheflightenvelope. Thisinstability wasfoundtobeasingle-degree-of-freedom (DOF) instability, nottheclassical bending/torsion coupling instability. SingleDOFinstabilities mayresultfromasymmetric shock-boundary layerinteractions. Theinstability couldbeeliminated byincreasing themechanism stiffness considerably (i.e.:increasing thetorquetubediameter beyond 38.1mm (1.5in)).However, thestiffness increase required wasnotfeasible giventhevolume andmassconstraints onthemechanism [5].Amodification to thecontrolsystem involving activedamping usingpressure feedback wasdeveloped inordertodealwith thisproblem. SDRC's initialflutteranalysis alsorevealed thataerodynamic loading increased thestiffness ofthe system. Thisloading occurswhenthespeedbrakes aredeployed intotheairstream [5]butnotwhenthe speedbrakes areclosed. Itwasdecided topreload thespeedbrakes intheclosedposition by'pinching' thetrailing edgeofthespeedbrakes together. Asetofelastomer padswasinstalled inthreelocations alongthespanofthespeedbrake toprovide abearing surface, andtheactuator isusedtoprovide the preload force. AGround Vibration Test(GVT)wasperformed ontheflighthardware atDryden FlightResearch Center (Figures 11and12).Datafromthattestwereusedtocalibrate andconfirm SDRC's analyses. Therigid body'scissors mode',foundat37HzduringGVT,washigherthantheinitial17Hzprediction (Figure 13). Theinitialmodalanalysis wasrefined bycorrecting modeling discrepancies andwasabletopredictthe modeat37Hz.Thesedataaresummarized inFigure14[6].Withthemodeat37Hz,thecontrolsystem activedamping modification actually decreased stability, andso,itwasremoved afterGVT. 65
7¸. 37Hz_f''_ _ _,..J % j: Figure13.GVTRevealed ThattheSpeedbrake Scissors ModeWasHigher ThanInitially Predicted Theflutteranalysis wasrerunusingthecorrelated model.Apotential flutterinstability stillexisted inthe lowsupersonic portions oftheflightenvelope. Itshould benotedthattheflutteranalysis assumes itis analyzing singlesurface thatissubjected tosmalldisturbances. Thespeedbrakes areactually two surfaces thatarebothsubjected tolargedisturbances (6_b=60°).Theanalysis isextrapolating itsresults andmaynotbecompletely accurate. Awindtunnelfluttertestmayberequired inordertoverifythatthe instability doesexist.Actualflighttestinginthetransonic regimewherethesystem ismostsusceptible to flutterwiltbetheultimate testofthedesign. 45 40 35 _.3O _2s _2o gu.15 10 5 037078 Initial37,172 37,078 Final[]Analysis I;3Test Figure 14.AfterCorrecting Modeling Discrepancies, Predicted Frequencies Matched TestResults CostandSchedule Constraints Thedesign oftheX-34speedbrake mechanism demonstrated thatitispossible todesign acompact controlsurface deployment mechanism withadequate stiffness toprevent aerodynamic flutterforlowcost inashorttimespan. Theoriginal X-34program wasafixedpricecontract valuedat$60millionover30 months. Thespeedbrake mechanisms needed tobedesigned, fabricated, tested,andintegrated under theseconstraints. 66
Inordertomeetschedule, fabrication ofthespeedbrake mechanism commenced withthecompletion of handcalculations andlimitedfiniteelement modeling. Astheanalysis wascompleted, itbecame apparent thattheloadsinduced bythespeedbrake mechanism ontheaftsparoftheall-moving vertical tailwould over-stress theskin-to-spar joints.Arudderbraceassembly thatconsisted ofapairofstrutsthatspanned between thefittingontheaftsparandtheadjacent ribwasaddedtooffloadtheskin-to-spar joints.A composite doubler andmetallic backing platewereaddedtotheaftsparandactuator ribtoprevent fastener pullthru.Thesemodifications wereimplemented withminimal impacttothemechanism andtail, whichwerealready inproduction, andthespeedbrake mechanism wasdelivered tostaticloadtestingon time. Inordertokeepcostsdown,theamount ofassembly toolingforthespeedbrake mechanism waskeptto aminimum. Allcomponents weredesigned tobeassembled inplaceonthetailwithout fixturing. Anaft sparsimulator showninFigure15,whichconsisted ofaflataluminum platecontaining theappropriate holepatterns, wasfabricated toassistinassembling thetorquetubesub-assembly. Thissub-assembly required alignment between torquetubeswhichwaseasiertoachieve usingassembly toolingthanby design. Ifahigherproduction ratewasrequired, theassembly toolmayhavebeendesigned differently to allowforeasiersetup.However, onlytwotorquetubesub-assemblies wereassembled usingthistooland theadditional timerequired todesigntheeasiersetuptoolwasnotdeemed necessary. TorqueTube Sub-assembly-- AftSpar Simulator Figure 15.Simplified Assembly Tooling wasDesigned fortheTorque TubeSub-assembly Asetofpillowblocksimulators wasalsofabricated toassistinproperly locating theaftsparrelative tothe tailskins.Thisisimportant forthepillowblockssincetheyhaveaboltpatternontheaftsparaswellasa boltpattern ontheskinwhoseplaneisroughly 90°totheaftsparplane.Again,itwaseasiertofabricate simple assembly tooling toachieve thecorrect alignment thantofabricate morecomplex tooling. Unfortunately, thepillowblocksimulators werenotusedcorrectly duringthefirsttailassembly andthe alignment between thetwoboltpatterns wasoff.Extensive rework tothepillowblockswasrequired in ordertoaccount forthisdiscrepancy. Inhindsight, thiswasacaseofnothavingadequate 'design space' toachieve agoodsolution. Thepillowblocksweredesigned withboltpatterns at90°toeachothersince thatwastheonlywaythereaction loadcouldbepassed intothestructure giventhesevere volume constraints. Inthiscase,takingthetimetodesignthemorecomplex toolingwouldhaveeliminated the timerequired toreworkthepillowblocks. Afterthedesign, analysis, fabrication, andintegration werecomplete, itwasnecessary toloadtestthe mechanism. Thetestingphilosophy forthespeedbrake mechanism andforallX-34components wasto verifythecomponents usingasystem leveltest.Instead oftesting itsindividual components, the 68
speedbrake mechanism wastestedatthesystemlevelaspartoftheall-moving verticaltailstaticload test.Thefullflightintegration ofthespeedbrake mechanism withtheexception ofthespeedbrake panels, speedbrake clevises, andhydraulic actuator wereinstalled intoaflighttail(speedbrake simulator and actuator simulator wereusedinplaceofflightarticles). Thecomposite speedbrake panelsandaluminum speedbrake cleviseswereprotoflight testedindividually inaseparate staticloadtest. Sincetheinterfaces between themetallic mechanism andthegraphite epoxytailwerechallenging to analyze, itwasbeneficial totestatasystem levelnotonlyverifytheintegrity oftheindividual components, butalsotoverifytheinterfaces between thecomponents. Mostunforeseen problems occur atjointandinterfaces. Systemleveltestingisahighlyefficientwayofdiscovering theseproblems [7]. AsshowninFigure16,themechanism wasverifiedbyfirstprotoflight testingto125%ofdesignlimit.In ordertoverifythattheprotoflight testdidnotintroduce anydamage, themechanism wasthenacceptance testedto100%ofdesignlimit.Theacceptance testwasthenrepeated. Thepeakstrainsanddeflections between eachacceptance testwererequired tobewithin5%andthestrainsanddeflections were required toreturntowith5%ofthepeakvalueinordertoverifythatnodamage waspropagating thruthe mechanism orstructure. Designing andtestingto125%ofthedesignlimitensures arobuststructure and accounts foruncertainties intrajectories, loads,analysis methods, andmanufacturing processes [7]. Twospeedbrake mechanisms werefabricated fortheX-34program andeachmechanism wassubjected toprotoflight testing.Incontrast toahighrateproduction program, itismoreefficienttotestandflyeach articletoaccount fortheinherent manufacturing andprocessing differences thatariseinalowvolume prototype program suchasX-34[7]. Protoflight Loading Eor8 P Design 125% Limit Design LimitFirstAcceptance _or5Second Acceptance ¢or_ Flight Test 10 Design LimitDesign Limit Figure16.Protoflight -Acceptance TestApproach [7] 69
Conclusions TheX-34splitflapspeedbrake mechanism isactuated withasinglelinearhydraulic actuator, ismounted totheall-moving vertical tail,andisdesigned fortransonic andhypersonic flight.Thespeedbrake mechanism isusedforenergy management duringdescent andforpitchtrimbothduringascentand descent. Thedesign ofthemechanism wassubjected volume constraints duetocarrier aircraft compatibility andaerodynamic requirements aswellasastiffness constraint duetoano-flutter requirement. Theseconstraints drovethelayoutanddesignofthemechanism. Inaddition, theexecution ofdesignwassubject tocostandschedule constraints setbyprogram goals.Inordertoaccomplish the task,asmallteamemployed advanced design andanalysis toolsinordertoworkasefficiently as possible butalsorecognized thatcertainanalyses couldbeperformed usingsimplehandcalculations or notperformed atallbutverified inasystem leveltest.Modular androbustdesigns werecreated aswell assimplified assembly toolingtocontrol costs.Theteamsubcontracted withexperts incertain subject areasandutilized ahighdegree ofconcurrent engineering. TheX-34speedbrake mechanism demonstrates thatitispossible todesign acompact control surface deployment mechanism with adequate stiffness toprevent aerodynamic flutterforlowcostinashorttimespan. Thisabilitycontributed significantly tothesuccess oftheX-34program. References 1.Pamadi, BanduN.,Gregory J.Brauckmann, Michael J.Ruth,andHenriD.Fuhrmann, "Aerodynamic Characteristics, Database Development andFlightSimulation oftheX-34Vehicle", AIAA2000-0900. 2.Brauckmann, Gregory J.,"X-34Vehicle Aerodynamic Characteristics", AIAA-98-2531. 3.Jenkins, Dennis R.,SpaceShuttle: TheHistory ofDeveloping theNational Space Transportation System. Motorbooks International. Osceola, WI,1992. 4.X10001, LoadandDesign Criteria X-34.OrbitalDocument, RevC,6/30/99. 5.Blades, EricL.,MikeRuth,andHenriD.Fuhrmann, "Aeroelastic Analysis oftheX-34Launch Vehicle", AIAA-99-1352. 6.Blelloch, Paul,EricL.Blades, andThomas L.Dragone, "Modeling andCorrelation oftheX-34Launch Vehicle", AIAA-2000-1777. 7.Dragone, Thomas L.,"Structural Innovations inDesign, Manufacturing, andTesting ontheX-34 Reusable Launch Vehicle", AIAA-2000-5309. Acknowledgements TheauthorwouldliketothankTomDragone, HenriFuhrmann, MikeRuth,andBryanSullivan ofOrbital Sciences Corporation fortheirassistance withthispaper. 70