美国SR71黑鸟Word文档格式.docx
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美国SR71黑鸟Word文档格式.docx
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Johnsonwasresponsibleformanyofthedesign'
sinnovativeconcepts.Duringaerialreconnaissancemissions,theSR-71operatedathighspeedsandaltitudestoallowittooutracethreats.Ifasurface-to-airmissilelaunchwasdetected,thestandardevasiveactionwassimplytoaccelerateandoutflythemissile.TheSR-71wasdesignedtohavebasicstealthcharacteristicsandservedasaprecursortofuturestealthaircraft.TheSR-71servedwiththeU.S.AirForcefrom1964to1998.Atotalof32aircraftwerebuilt;
12werelostinaccidentsandnonelosttoenemyaction.TheSR-71hasbeengivenseveralnicknames,includingBlackbirdandHabu.Since1976,ithasheldtheworldrecordforthefastestair-breathingmannedaircraft,arecordpreviouslyheldbytherelatedYF-12.
Design
Overview
TheSR-71wasdesignedforflightatoverMach3withaflightcrewoftwointandemcockpits,withthepilotintheforwardcockpitandtheReconnaissanceSystemsOfficer(RSO)monitoringthesurveillancesystemsandequipmentfromtherearcockpit.TheSR-71wasdesignedtominimizeitsradarcross-section,anearlyattemptatstealthdesign.Finishedaircraftwerepaintedadarkblue,almostblack,toincreasetheemissionofinternalheatandtoactascamouflageagainstthenightsky.Thedarkcolorledtotheaircraft'
scallsign"
.
WhiletheSR-71carriedradarcountermeasurestoevadeinterceptionefforts,itsgreatestprotectionwasitshighspeedandcruisingaltitudethatmadeitalmostinvulnerabletotheweaponsofitsday.Merelyacceleratingwouldtypicallybeenoughtoevadeasurface-to-airmissile,andtheplanewasfasterthantheSovietUnion'
sprincipalinterceptor,theMikoyan-GurevichMiG-25.TheMiG-25'
ssuccessor,theMiG-31,wasabletointercepttheSR-71,asitwascapableofMach2.8andarmedwiththeMach4.5R-33missile.SR-71overflightsoftheUSSRceasedfollowingMiG-31interceptsinthemid-1980s.Nonetheless,duringitsservicelife,noSR-71wasshotdown.
Airframe,canopyandlandinggear
Onmostaircraft,useoftitaniumwaslimitedbythecostsinvolved;
itwasgenerallyusedonlyincomponentsexposedtothehighesttemperatures,suchasexhaustfairingsandtheleadingedgesofwings.OntheSR-71,titaniumwasusedfor85%ofthestructure,withmuchoftherestpolymercompositematerials.Tocontrolcosts,Lockheedusedamoreeasilyworkedtitaniumalloywhichsoftenedatalowertemperature.ThechallengesposedledLockheedtodevelopnewfabricationmethods,andhavesincebeenusedinthemanufactureofotheraircraft.Weldingtitaniumrequiresdistilledwater,asthechlorinepresentintapwateriscorrosive;
cadmium-platedtoolscouldnotbeusedastheyalsocausedcorrosion.Metallurgicalcontaminationwasanotherproblem;
atonepoint80%ofthedeliveredtitaniumformanufacturewasrejectedonthesegrounds.
Thehightemperaturesgeneratedinflightrequiredspecialdesignandoperatingtechniques.Majorportionsoftheskinoftheinboardwingswerecorrugated,notsmooth.Aerodynamicistsinitiallyopposedtheconcept,disparaginglyreferringtotheaircraftasaMach3variantofthe1920s-eraFordTrimotor,knownforitscorrugatedaluminumskin.Theheatwouldhavecausedasmoothskintosplitorcurl,whereasthecorrugatedskincouldexpandverticallyandhorizontallyandincreasedlongitudinalstrength.
Fuselagepanelsweremanufacturedtoonlylooselyfitontheground.Properalignmentwasachievedastheairframeheatedupandexpandedseveralinches.Becauseofthis,andthelackofafuelsealingsystemthatcouldhandletheairframe'
sexpansionatextremetemperatures,theaircraftleakedJP-7fuelonthegroundpriortotakeoff.
Theouterwindscreenofthecockpitwasmadeofquartzandwasfusedultrasonicallytothetitaniumframe.Thetemperatureoftheexteriorofthewindscreenreached600°
F(316°
C)duringamission.
Coolingwascarriedoutbycyclingfuelbehindthetitaniumsurfacesinthechines.Onlanding,thecanopytemperaturewasover300°
C(572°
F).TheredstripesonsomeSR-71sweretopreventmaintenanceworkersfromdamagingtheskin.Nearthecenterofthefuselage,thecurvedskinwasthinanddelicate,withnosupportfromthestructuralribs,whichwerespacedseveralfeetapart.
TheBlackbird'
stires,manufacturedbyB.F.Goodrich,containedaluminumandwerefilledwithnitrogen.Theycost$2,300anddidnotlast20missions.TheBlackbirdlandedatover170knotsanddeployedadragparachutetostop;
thechutealsoactedtoreducestressonthetires.
Shapeandthreatavoidance
Thefirstoperationalaircraftdesignedaroundastealthaircraftshapeandmaterials,theSR-71hadseveralfeaturesdesignedtoreduceitsradarsignature.TheSR-71hadaradarcross-section(RCS)ofaround10squaremeters.Drawingonearlystudiesinradarstealthtechnology,whichindicatedthatashapewithflattened,taperingsideswouldreflectmostenergyawayfromaradarbeam'
splaceoforigin,engineersaddedchinesandcantedtheverticalcontrolsurfacesinward.Specialradar-absorbingmaterialswereincorporatedintosawtooth-shapedsectionsoftheaircraft'
sskin.Cesium-basedfueladditiveswereusedtosomewhatreduceexhaustplumesvisibilitytoradar,althoughexhauststreamsremainedquiteapparent.KellyJohnsonlaterconcededthatSovietradartechnologyadvancedfasterthanthestealthtechnologyemployedagainstit.
TheSR-71featuredchines,apairofsharpedgesleadingaftfromeithersideofthenosealongthefuselage.ThesewerenotafeatureontheearlyA-3design;
Dr.FrankRodgersoftheScientificEngineeringInstitute,aCIAfrontorganization,discoveredthatacross-sectionofaspherehadagreatlyreducedradarreflection,andadaptedacylindrical-shapedfuselagebystretchingoutthesidesofthefuselage.AftertheadvisorypanelprovisionallyselectedConvair'
sFISHdesignovertheA-3onthebasisofRCS,LockheedadoptedchinesforitsA-4throughA-6designs.
Aerodynamicistsdiscoveredthatthechinesgeneratedpowerfulvorticesandcreatedadditionallift,leadingtounexpectedaerodynamicperformanceimprovements.Theangleofincidenceofthedeltawingscouldbereducedforgreaterstabilityandlessdragathighspeeds,andmoreweightcarried,suchasfuel.Landingspeedswerealsoreduced,asthechines'
vorticescreatedturbulentflowoverthewingsathighanglesofattack,makingithardertostall.Thechinesalsoactedlikeleading-edgeextensions,whichincreasetheagilityoffighterssuchastheF-5,F-16,F/A-18,MiG-29andSu-27.Theadditionofchinesalsoenabledtheremovaloftheplannedcanardforeplanes.
Airinlets
TheairinletsallowedtheSR-71tocruiseatoverMach3.2whilekeepingairflowintotheenginesattheinitialsubsonicspeeds.Mach3.2wasthedesignpointfortheaircraft,itsmostefficientspeed.Atthefrontofeachinlet,apointed,movableconecalleda"
spike"
(Inletcone)waslockedinitsfullforwardpositiononthegroundandduringsubsonicflight.WhentheaircraftacceleratedpastMach1.6,aninternaljackscrewmovedthespikeupto26inches(66cm)inwards,directedbyananalogairinletcomputerthattookintoaccountpitot-staticsystem,pitch,roll,yaw,andangleofattack.Movingthespiketipdrewtheshockwaveridingonitclosertotheinletcowlinguntilittouchedjustslightlyinsidethecowlinglip.Thispositionreflectedthespikeshock-waverepeatedlybetweenthespikecenterbodyandtheinletinnercowlsides,andminimizedairflowspillagewhichisthecauseofspillagedrag.Theairslowedsupersonicallywithafinalplaneshockwaveatentrytothesubsonicdiffuser.
Downstreamofthisnormalshocktheairissubsonic.Itdeceleratesfurtherinthedivergentducttogivetherequiredspeedatentrytothecompressor.Captureoftheplaneshockwavewithintheinletiscalled"
StartingtheInlet"
.Bleedtubesandbypassdoorsweredesignedintotheinletandenginenacellestohandlesomeofthispressureandtopositionthefinalshocktoallowtheinlettoremain"
started"
.TheSR-71wassometimesmoreefficientatspeedshigherthanMach3.2intermsofpoundsoffuelburnedpernauticalmiletraveled,dependingonoutsideairtemperature.Duringonemission,SR-71pilotBrianShulflewfasterthanusualtoavoidmultipleinterceptionattempts;
afterwards,itwasdiscoveredthatthishadreducedfuelconsumption.
Intheearlyyearsofoperation,theanalogcomputerswouldnotalwayskeepupwithrapidlychangingflightenvironmentalinputs.Ifinternalpressuresbecametoogreatandthespikewasincorrectlypositioned,theshockwavewouldsuddenlyblowoutthefrontoftheinlet,calledan"
InletUnstart"
.Duringunstartsafterburnerextinctionswerecommon.Theremainingengine'
sasymmetricalthrustwouldcausetheaircrafttoyawviolentlytooneside.SAS,autopilot,andmanualcontrolinputswouldfighttheyawing,butoftentheextremeoff-anglewouldreduceairflowintheoppositeengineandstimulate"
sympatheticstalls"
.Thisgeneratedarapidcounter-yawing,oftencoupledwithloud"
banging"
noises,andaroughrideduringwhichcrews'
helmetswouldsometimesstriketheircockpitcanopies.Oneresponsetoasingleunstartwasunstartingbothinletstopreventyawing,thenrestartingthemboth.Lockheedlaterinstalledanelectroniccontroltodetectunstartconditionsandperformthisresetactionwithout
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