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1、Oneofthegreatestinventionsthatchangedourlives——AirplaneForthousandsofyears,ourancestorshaddreamedtoflylikebirds.Finallyoneday,thedreamcametrue.Nowadays,wecanflyfasterthanbirds,wecanflyfurtherthanbirds,andwecan fly higher than birds.Nomatterhowfarthedestinationwas,nomatteritwasabusinesstriportravelin
2、g,wewenttherebyairplanes.Airplaneshavechangedourlives.Itdeliveredconveniencetous.Well,hereweare.1.EarlyhistoryCayley'sfirstinnovationwastostudythebasicscienceofliftbyadoptingthewhirlingarmtestrigforuseinaircraftresearchandusingsimpleaerodynamicmodelsonthearm,ratherthanattemptingtoflyamodelofacomplet
3、edesign.In1799hesetdowntheconceptofthemodernairplaneasafixed-wingflyingmachinewithseparatesystemsforlift,propulsion,andcontrol.In1804Cayleyconstructedamodelgliderwhichwasthefirstmodernheavier-than-airflyingmachine,havingthelayoutofaconventionalmodernaircraftwithaninclinedwingtowardsthefrontandadjust
4、abletailatthebackwithbothtailplaneandfin.Amovableweightallowedadjustmentofthemodel'scenterofgravity.In1848hehadprogressedfarenoughtoconstructagliderintheformofatriplanelargeandsafeenoughtocarryachild.Alocalboywaschosenbuthisnameisnotknown.Hewentontopublishin1852thedesignforafull-sizemannedglideror"g
5、overnableparachute"tobelaunchedfromaballoonandthentoconstructaversioncapableoflaunchingfromthetopofahill,whichcarriedthefirstadultaviatoracrossBromptonDalein1853.Attheageofsteam,Henson's1842designforanaerialsteamcarriagebrokenewgrounddrawingdirectlyfromCayley'swork.Althoughonlyadesign,itwasthefirsti
6、nhistoryforapropeller-drivenfixed-wingaircraft.2.TheWrightBrothersUsingamethodologicalapproachandconcentratingonthecontrolabilityoftheaircraft,thebrothersbuiltandtestedaseriesofkiteandgliderdesignsfrom1900to1902beforeattemptingtobuildapowereddesign.Theglidersworked,butnotaswellastheWrightshadexpecte
7、dbasedontheexperimentsandwritingsoftheir19th-centurypredecessors.Theirfirstglider,launchedin1900,hadonlyabouthalfthelifttheyanticipated.Theirsecondglider,builtthefollowingyear,performedevenmorepoorly.
