美国隐形轰炸机B2.docx

美国隐形轰炸机B2.docx

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美国隐形轰炸机B2

NorthropGrummanB-2Spirit

Overview

TheNorthrop（laterNorthropGrumman）B-2Spirit,alsoknownastheStealthBomber,isanAmericanheavystrategicbomber,featuringlowobservablestealthtechnologydesignedforpenetratingdenseanti-aircraftdefenses;itisablendedwingbodydesignwithacrewoftwo.Thebombercandeploybothconventionalandthermonuclearweapons,suchaseighty500lb（230kg）-class（Mk82）JDAMGlobalPositioningSystem-guidedbombs,orsixteen2,400lb（1,100kg）B83nuclearbombs.TheB-2istheonlyknownaircraftthatcancarrylargeair-to-surfacestandoffweaponsinastealthconfiguration.

Developmentoriginallystartedunderthe"AdvancedTechnologyBomber"（ATB）projectduringtheCarteradministration,anditsperformancewasoneofhisreasonsforthecancellationofthesupersonicB-1Abomber.ATBcontinuedduringtheReaganadministration,butworriesaboutdelaysinitsintroductionledtothereinstatementoftheB-1programaswell.Programcostsrosethroughoutdevelopment.DesignedandmanufacturedbyNorthropGrumman,thecostofeachaircraftaveragedUS$737million（in1997dollars）.Totalprocurementcostsaveraged$929millionperaircraft,whichincludesspareparts,equipment,retrofitting,andsoftwaresupport.Thetotalprogramcostincludingdevelopment,engineeringandtesting,averaged$2.1billionperaircraftin1997.

Becauseofitsconsiderablecapitalandoperatingcosts,theprojectwascontroversialintheU.S.CongressandamongtheJointChiefsofStaff.Thewinding-downoftheColdWarinthelatterportionofthe1980sdramaticallyreducedtheneedfortheaircraft,whichwasdesignedwiththeintentionofpenetratingSovietairspaceandattackinghigh-valuetargets.Duringthelate1980sand1990s,Congressslashedplanstopurchase132bombersto21.In2008,aB-2wasdestroyedinacrashshortlyaftertakeoff,thoughthecrewejectedsafely.Atotalof20B-2sremaininservicewiththeUnitedStatesAirForce,whichplanstooperatetheB-2until2058.

TheB-2iscapableofall-altitudeattackmissionsupto50,000feet（15,000m）,witharangeofmorethan6,000nauticalmiles（11,000km）oninternalfuelandover10,000nauticalmiles（19,000km）withonemidairrefueling.Thoughoriginallydesignedprimarilyasanuclearbomber,itwasfirstusedincombatdroppingconventionalordnanceintheKosovoWarin1999andsawfurtherserviceinIraqandAfghanistan.

Design

TheB-2SpiritwasdevelopedtotakeovertheUSAF'svitalpenetrationmissions,abletotraveldeepintoenemyterritorytodeploytheirordnance,whichcouldincludenuclearweapons.TheB-2isaflyingwingaircraft,meaningithasnofuselageortail.Theblendingoflow-observabletechnologieswithhighaerodynamicefficiencyandlargepayloadgivestheB-2significantadvantagesoverpreviousbombers.Lowobservabilityprovidesagreaterfreedomofactionathighaltitudes,thusincreasingbothrangeandfieldofviewforonboardsensors.TheU.S.AirForcereportsitsrangeasapproximately6,000nauticalmiles（6,900mi;11,000km）.AtcruisingaltitudetheB-2refuelseverysixhours,takingonupto50shorttons（45t）offuelatatime.

Duetotheaircraft'scomplexflightcharacteristicsanddesignrequirementstomaintainvery-lowvisibilitytomultiplemeansofdetection,boththedevelopmentandconstructionoftheB-2requiredpioneeringuseofcomputer-aideddesignandmanufacturingtechnologies.TheB-2bearsaresemblancetoearlierNorthropaircraft:

theYB-35andYB-49werebothflyingwingbombersthathadbeencanceledindevelopmentintheearly1950s,allegedlyforpoliticalreasons.TheresemblancegoesasfarasB-2andYB-49havingthesamewingspan.

AsofSeptember2013about80pilotsflytheB-2.Eachaircrafthasacrewoftwo,apilotintheleftseatandmissioncommanderintheright,andhasprovisionsforathirdcrewmemberifneeded.Forcomparison,theB-1BhasacrewoffourandtheB-52hasacrewoffive.TheB-2ishighlyautomatedand,unlikemosttwo-seataircraft,onecrewmembercansleepinacampbed,useatoilet,orprepareahotmealwhiletheothermonitorstheaircraft;extensivesleepcycleandfatigueresearchwasconductedtoimprovecrewperformanceonlongsorties.

Armamentsandequipment

TheB-2,intheenvisagedColdWarscenario,wastoperformdeep-penetratingnuclearstrikemissions,makinguseofitsstealthycapabilitiestoavoiddetectionandinterceptionthroughoutmissions.Therearetwointernalbombbaysinwhichmunitionsarestoredeitheronarotarylauncherortwobomb-racks;thecarriageoftheweaponsloadoutsinternallyresultsinlessradarvisibilitythanexternalmountingofmunitions.TheB-2iscapableofcarrying40,000poundsofordnance.NuclearordnanceincludestheB61andB83nuclearbombs;theAGM-129ACMcruisemissilewasalsointendedforuseontheB-2platform.

Itwasdecided,inlightofthedissolutionoftheSovietUnion,toequiptheB-2forconventionalprecisionattacksaswellasforthestrategicroleofnuclear-strike.TheB-2featuresasophisticatedGPS-AidedTargetingSystem（GATS）thatusestheaircraft'sAPQ-181syntheticapertureradartomapouttargetspriortodeploymentofGPS-aidedbombs（GAMs）,latersupersededbytheJointDirectAttackMunition（JDAM）.IntheB-2'soriginalconfiguration,upto16GAMsorJDAMscouldbedeployed;anupgradeprogramin2004raisedthemaximumcarriablecapacityto80JDAMs.

TheB-2hasvariousconventionalweaponsinitsarsenal,abletoequipMark82andMark84bombs,CBU-87CombinedEffectsMunitions,GATORmines,andtheCBU-97SensorFuzedWeapon.InJuly2009,NorthropGrummanreportedtheB-2wascompatiblewiththeequipmentnecessarytodeploythe30,000lb（14,000kg）MassiveOrdnancePenetrator（MOP）,whichisintendedtoattackreinforcedbunkers;uptotwoMOPscouldbeequippedintheB-2'sbombbays,theB-2istheonlyplatformcompatiblewiththeMOPasof2012.Asof2011,theAGM-158JASSMcruisemissileisanupcomingstandoffmunitiontobedeployedontheB-2andotherplatforms.ThisistobefollowedbytheLongRangeStandoffWeaponwhichmaygivetheB-2astandoffnuclearcapabilityforthefirsttime.

Avionicsandsystems

InordertomaketheB-2moreeffectivethanpreviousbombers,manyadvancedandmodernavionicssystemswereintegratedintoitsdesign,thesehavebeenmodifiedandimprovedfollowingaswitchtoconventionalwarfaremissions.OnesystemisthelowprobabilityofinterceptAN/APQ-181multi-moderadar,afullydigitalnavigationsystemthatisintegratedwithterrain-followingradarandGlobalPositioningSystem（GPS）guidance,NAS-26astro-inertialnavigationsystem（firstsuchsystemtestedontheNorthropSM-62Snarkcruisemissile）andaDefensiveManagementSystem（DMS）toinformtheflightcrewofpossiblethreats.TheonboardDMSiscapableofautomaticallyassessingthedetectioncapabilitiesofidentifiedthreatsandindicatedtargets.

Forsafetyandfault-detectionpurposes,anon-boardtestsystemisinterlinkedwiththemajorityofavionicsontheB-2tocontinuouslymonitortheperformanceandstatusofthousandsofcomponentsandconsumables;italsoprovidespost-missionservicinginstructionsforgroundcrews.In2008,manyofthe136standalonedistributedcomputersonboardtheB-2,includingtheprimaryflightmanagementcomputer,werebeingreplacedbyasingleintegratedsystem.Theavionicsarecontrolledby13EMP-resistantMIL-STD-1750Acomputers,whichareinterconnectedthrough26MIL-STD-1553B-busses;othersystemelementsareconnectedviaopticalfiber.

Inadditiontoperiodicsoftwareupgradesandtheintroductionofnewradar-absorbentmaterialsacrossthefleet,theB-2hashadseveralmajorupgradestoitsavionicsandcombatsystems.Forbattlefieldcommunications,bothLink-16andahighfrequencysatellitelinkhavebeeninstalled,compatibilitywithvariousnewmunitionshasbeenundertaken,andtheAN/APQ-181radar'soperationalfrequencywasshiftedinordertoavoidinterferencewithotheroperator'sequipment.ThearraysoftheupgradedradarfeatureswereentirelyreplacedtomaketheAN/APQ-181intoanactiveelectronicallyscannedarray（AESA）radar.

TokeeptheB-2relevantagainstincreasinglysophisticatedairdefenseswithgreatercomputerprocessingpowerthatmaybeabletodetecttheaircraftthroughitsstealthmeasures,theAirForceisworkingtoupgradetheDefensiveManagementSystem（DMS）,whichusessensors,passivereceivers,andcomputerstoalertcrewaboutthelocationofenemyairdefensesystems.Thoughitwillnotcounterairthreats,itwillbemorecapableofidentifyingandlocatingthembeforetheaircraftentersstrikerange.TheupgradedDMSwillhelpdetectradaremissionsfromairdefensestoallowchangestotheauto-router'smissionplanninginformationwhilein-flightsoitcanreceivenewdataquicklytoplanaroutethatminimizesexposuretodangers.TheDMSupgradeisslatedtoenterserviceby2021.

Flightcontrols

Inordertoaddresstheinherentflightinstabilityofaflyingwingaircraft,theB-2usesacomplexquadruplexcomputer-controlledfly-by-wireflightcontrolsystem,thatcanautomaticallymanipulateflightsurfacesandsettingswithoutdirectpilotinputsinordertomaintainaircraftstability.Theflightcomputerreceivesinformationonexternalconditionssuchastheaircraft'scurrentairspeedandangleofattackviapitot-staticsensingplates,asopposedtotraditionalpitottubeswhichwouldnegativelyaffecttheaircraft'sstealthcapabilities.Theflightactuationsystemincorporatesbothhydraulicandelectricalservoactuatedcomponents,anditwasdesignedwithahighlevelofredundancyandfault-diagnosticcapabilities.

Nor