1、IIIIILSECURITY INFORMATION,. . .NACAEFFECTSOF STABILIZINGFINSANDA REAR-SUPPORTSTINGON THE BASEPRJZSSURESOF A BODY OF REVOLUTION INIRESEARCH TMEMORANDUMFREE FLIGHTAT MACH NUMBERS FROM 0.7TO 1.3ByRogerG.WrtkngleyAeronauticalLaboratxwyLangleyField,Va.cIMsmEDDxmdENr.NATIONALADVISORYCOMMITTEEFOR AERONAUT
2、ICSWASHINGTONSeptember22,1952IIIamiwiik- .- . -_ - .-_ ._ . .;. ,“Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-r -_“-_1 _/py - 2 m=!.i,$-?k,%t,mt.!J;,V/catmosphericpressure,lb/sqftbasepressure,lb/sqftP-pbase-pressurecoefficient,Reynoldsnumber,airs
3、ed,ftsecatmosphericdensity,slugs/cuft.atmosphericViscosity,lbsec/sqftd.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. MODEZS-P.N/WARML52E06 . 3Thetestconfigurationsareshowninfigures1to4. Allhadthesamefuselageshape- abodyofrevolutionoffinenessratio
4、U.formedbyjoininga ftieness-ratio-s.ogivalnosetoa cylinder.CoordfiatesofthenoseprtionarelistedintableI. Configurationconsistedofthisfuselagewithoutmodificationsorappendages.Theothertestconfigurationshadoneormoreofthefol.lowtig:a rear-supprtstingsimilartothoseusedinwtidtunnels,a rockettailnut,foursta
5、bi-lizingfins,anda pintednosesting.DataforconfigurationsE andCwereoriginallypresentedinreferences3and4,respectively.DataforthefinlessconfigurationsandforconfigurationGarepresentedhereinforthefirsttime.ConfigurationsC,E,andGwerestabilizedbyfourfinsspacedequallyaroundthebody.Theleadingedgeofeachfinwas
6、sweptback45,andthe,plauformwastaperedfroma rootchordof8.38inchestoatipchcmdof1.38inches.Theexsedfinaspectratiowas1.43.Thefinsmeasured0.091inchintbiclmessandwererectangularinsectionexceptforroundedleadingedges.Thefinlessmodelsdependedfortheirstabilityona specialconstructionwhichplacedthecenterofgravi
7、tyatstation9.7forconfigurationsA andD andatstation0.3 forconfigurationF. Thecylindricalpartofthefuselageconsistedofathinbalsa-woodshell.reinforcedbylightplywoodbulkheads.MercuryandleadballastwasusedinthenosesofconfigurationsA andD,anda lead-weightednosestingwasusedforconfigurationF. Thestingwasappro
8、ximatelyfivebodydiametersinlengthandhadatitsapexa coneofthesamegleasthenosetipwhichitreplaced.Themodelsweresmoothandfair.Metalsurfaceswerelished,andwoodsurfacesweresandedandfinishedwithclearlacquer.Plasticfillerswereusedtoeliminatesmallindentations.TESTSThefinlessmodelswerelaunchedandacceleratedtosu
9、personicspeedsbymodifiedWAR rocketmotors.(Seefig.4.) Thrustwasappliedbymeansofa steelthrusttube,whichextendedfromthenoseoftheboosterthroughthelightlyconstructedcyltidricalpmtionofthemodelandforwardtoheavierstructuralmembersh thenose.Afterburnoutthebooster,havinga higherdragdecelerationratethm themod
10、el,quicklyseprated.Thethrusttubewithdrewwiththebooster,andthemodelflewfreely._ . .- . - . -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4 NACARML52E06ConfigurationGemployeda two-stagepropulsionsystem.Thefirststage,or“booster,”waSanexternalEVARrock
11、etmotor.Thesecondstage,or“sustainer,”wasaninternal3.2S-inchMk7rocketmotor.Duringthefirstpartoftheflightthebposterengagedthesustainerbymeansofanozzleplugadapter.Shortlyaftertheboosterstoppedthrusting,themodelandboosterseparatedbecauseofa differenceintheirdragdecel-erationrates.Thenthesustainermotorfi
12、red,bringingthemodeltoitsmaximumspeed.Thedragdatawereobtainedduringthepsriodofcoastingflightaftersustainerburnout.ThemodelsweretrackedbyIbpplerradarvelocimeterandSCR-584radartheodolitetodeterminealtitude,speedanddirectionofflight,anddecel.erationalongtheflightpath.Atmosphericconditionsweremeasuredby
13、meansofradiosondeballoonsreleasedtiediatelyaftertheflights.Dragwasdeterminedfromthemodeldecelerationrateaftersubtractingthepropercomponentofgravity.Oneofthefinlessmodelswasinstrumentedforthetelemeteringofbasepressures.Bymeansofatwochanneltelemeter,pressuresontherimofthebaseandinsidethehollowbodywere
14、transmittedcontinuouslytoa groundreceivingstation.ConfigurationsBandA correspmdtothebase-pressuremodelbeforeandafterboosterseparation.Forthisflighttheboosterthrusttubewasmadetoresembleawind-tunnelrear-suppxtsting.ThemaJorsourcesoferrorindeterminingdragcoefficientsbythepreviouslydescribedtechniqueare
15、(1)inaccuraciesintheinstrumentsandinthereductionofinstrumentdata,(2inaccuracyinthemanufactureofmodels,and(3)aircurrents,whichcauseerrorsinairspeed.Assumingthatallofthesetendtobeofarandomnature,theprobableerrorcanbestbeestimatedbynotingthediscrepanciesamongfairedcurvesformodelsofthesameconfiguration.
16、Thishasbeendonefora numberofpreviouslytestedmodelsofconfigurationE. Onthatbasis,theprobableerrorindragcoefficierrthasbeenestimatedtobelessthan4percentforthepresenttestsInreducingthepresentdata,theairwasassumedtobeatrestrelativetotheground.Therefore,anycurrentmotionwhichmayhaveexistedatthetimeofthefl
17、ighttestshasresultedinanairspeederrorwhichisapproximatelyequaltothevelocitycomponentofthecurrentinthedirectionoftheflightpath.Sincetheaerodynamiccoefficientsarebasedon #pV2,thepercentageerrorinthecoefficientsduetocurrentsisabouttwicethatin V. Theairspeederrorwhichwouldberequiredtoproducealloftheobse
18、rvedscatterin CD wouldbeaboutWO feetpersecond.Thisvaluerepresentsanupper,limitfortheprobableerrorinairspeed.Thetruevalueis,accordingtootherindications,closer,tohalfthatvalue.TheprobableerrorinMachnumberisthenaboutiO.01. Provided by IHSNot for ResaleNo reproduction or networking permitted without lic
19、ense from IHS-,-,-.-NACARML52E06 5.ThemeasurementsofbasepressureandofatmosphericpressureareaccuratetoaboutiO.07poundpersquareinch.Theseerrors,togetherwithaMachnumbererrorof.01,leadtomaximumerrorsinbase-pressurecoefficientortO.030atMachnumber0.8andto.013atMachnumberl.=.Byusingthetheoryofreference5,st
20、abilitycalculationsweremadeforthefinlessbodywiththerearmostcenter-of-gravitylocation.Theresultsindicatedthatthemodelwouldtrimatanangleofattackoflessthan1. Althoughnoaugle-of-attackmeasurementsweremadeforthemodelsinflight,itisassumedherethatthevalueswhichexist-edwere,likethetheoreticalvalues,toosmall
21、tohaveappreciableeffectsondragorbasepressure.Total-dragcoefficientsforconfigurationsA,D,.E,F,andG,andbase-dragcoefficientsforconfigurationsA,B,andC arepresentedhereinfortherangesofMachnumbersandReynoldsnumbershowninfigure5.magnitudeofthesubsonicspeeds.rapidly,and,atRESULTSANDDISCUSSIONBase-PressureI
22、Bkafigure6,therear-suprtstingreducedtheabsolutebase-pressurecoefficientsbyaboutk(lpercentatWithincreasingMachnumbertheeffectdecreasedMachnumbersabove1.15,therear-suppmtstinghadnosignificanteffectonbasepressuresThroughoutthepresenttestrangethestabiliztigfinskd theeffectofdecreasingthebasedrag.Thiseff
23、ectisshowninfigures7 and8,wherebase-pressuredataforconfigurationsA andC arecompared.Inreference6,otherfinconfigurationslocatedsimilarlyona cylin-dricalbodywereshowntoincreasebasesuctionatsupersonicspeeds.Thisincreasewasattributedtothefin-pressurefieldsimpingtigonthe“dead-air”regionatthebaseofthebody
24、.E!ecauseoftherectangularsectionofthepresentfins,lowpressuresareconfinedtoa smallregionJustbehindtheblunttrailingedge.Itisbelievedthat,inthepresentcase,thepredominanteffectisthatoflow-momentumairfromthefin-bodyjuncturesbeingdrawnintotheregionbehindthebodyandrelievingthebasesuction.DragDataDragdatafo
25、rthefinlessconfigurationsA,D,andF areshowninfigure9 andthedataforthefin-stabilizedconfigurationsE andGareLshowninfigure10. Effectsofthetailnutandnosesttigareseento.-. . . . -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- . . -. #6 besmalJandwith th
26、etestaccuracy,thoughthedatainindicatethatthenosestingincreasesthedragsomewhat.NACARML52E06bothfiguresAnticrementof0.009in CD,whichisofthesameorderasthatnoted,canbeobtainedbyassuminga viscousdragcoefficientof0.0023toactoverthewettedcylindricalareaofthesting.Thedatainfigure9 indicatethatthenosestingal
27、sohadtheeffectofloweringtheforce-breakMachnumber.Sincethiseffectisfarlesspronouncedinfire10,itappearslikelythatsome,ifnotall,oftheshiftisduetoMachnumbererror.Fin-dragcoefficientsareshowninfigureU. Thesehavebeenobtainedfromthedrag-coefficientincrementsbetweenconfigurationsDandE andbetweenF andG,andth
28、eythereforeincludeinterferenceeffects.AgeementisgoodexceptintheMachnumberrangefrom0.9to1.0,wheretheapparentshiftsinforce-breakMachnumberhada largeeffectonthedrag-coefficientincrements.Includedinthisfigureisa curverepresentingthechangeinbasedragcausedbyaddtigfins.toconfigurationA. Theinterference-dra
29、gvalueshavebeenbasedonfinareaforcomparisonhere%Infigure12,coefficientsofforedrag(totaldragminusbasedrag)forconfigurationarecomparedwiththeoreticalestimatesoftheircomponents.FlightMachnumbersandbody-lengthReynoldsnumberswereusedtocalculate(bythemethodofref.7)theaverageviscous-dragcoefficientsforawhol
30、lyturbulentflatplate,andthesewereassumedtoactoverthewettedareaoftheforebody.UnpublishedsubsonicpressuredistributionsobtainedintheLangleyhigh-speed7-by10-foottunnelindicatethatthepressuredragonthenoseisnegligibleatMachnumbersbelow0.9.”Thus,theforedragconsistsalnostentirelyoftiscousdragattheseMachnumb
31、ers.Thelowlevelofthesubsonicfore-dragcoefficientindicatesthatlaminarflowexistedovera significantpartofthebody.Thesupersonicpressuredragwasestimatedbythemethodofrefer-ence8 andbythegraphicalmethodofreference9. AtMachnumbersfrom1.1to1.25,thedifferencebetweenestimatedandmeasuredfore-dragcoefficientsisn
32、earlyconstant.A largepartofthisdiscrepncymaybeduetotheassurtionofa-whollyturbulentboundarylayeronthebody.Inreference10,pressuredragcalculatedforabodybythegaphicalmethodwasfoundtobeingoodagreementwithexpsrimen%atMachnumbersaslowasl.m. Thisresultdidnotholdtrueinthepresenttests.Thepor agreementshownatM
33、achnumber1.05maybeduetothelowerfinenesstitioofthepresentnose. I. _._ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . NACARML52E06 7CONCLUDINGRJKRKSIsolatedfuselageswereflight-testedatMachnumbersfrom0.7to1.3inordertodeterminethecontributionsoftheb
34、odyandthefin-bodyinterferencetothetotaldragofpreviouslytestedcombinations.A setofstabilizingfinsofnearlyrectangularsectionwasfoundtodecreasethebodybasedragovertheMachnumberrangeofthetests.Oneofthefinlessbodieshada rear-supportstingsimilartothoseusedinwindtunnels.ThestingreducedbasesuctionbyabouthOpe
35、rcentatsubsonicspseds,buthadnomeasurableeffectatMachnumbersabove1.15.Ithasbeenfoundthata simplenonspinningogive-cylindricalbodycanbestabilizedbyinternalballasting.Thepresentresultsalsosuggestthat,whereinternalballastingisinadequatebecauseofboattailingorotherbodyshapefactors,aweightednosestingcanbeus
36、ed.Thus,thetesttechniquesdescribedhereinmaybeapplicabletomanyfuselagesofpracticalinterest.LangleyAeronauticalLaboratoryNationalAdsoryCommitteeforAeronauticsLangleyField,Va.?$J? _. _. .- . - - -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.8 , NACA
37、RML!52E06REFERENCES1.SW., 1 J I 1A -i- 1 I I I I/ / /. tiTTRiJJ.6 .7 .8 .9 1.0 1.1 1.2 1.3 1.4MFigure8.-Base-dragcoefficientsforconfigurationsA andCforwhichmeasuredrim-andcenter-basepressuresareassumedtoactovertheentirerespectiveareas.,.Provided by IHSNot for ResaleNo reproduction or networking perm
38、itted without license from IHS-,-,-z, .III!.5.4.3CD.2.1QJ 1 1 1 , , II I i+hptppq “1 o- A-H. Io_,DF FFl4 , I I I , II I I I I =Jw=I.6 .7 .8 .9 1.0 1.1 1.2 1.3 1.4 1.5MFie 9.-Drag data for the wingless, finleas fuselages. GProvided by IHSNot for ResaleNo reproduction or networking permitted without l
39、icense from IHS-,-,-.-. .-.-z . _. _G.18 NACARML52E06.6.5.4?0.3.10.6 .7 .8 .9 1.0 1.1 1.2 13 1.4MFigure10.-Dragdataforthefin-stabilizedbodies.03.02c. .%.010 Interference-.01.6 .7 .8 .9 1.0 1.1 1.2 1.3 1.4MFigure11.-Total-dragcoefficientsforthestabilizingfinsandtheireffectonbodybasedrag., . -Provided
40、 by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.4II!ic .,3.2.10w Measured - CDB. ViBoouB component (estimated for all-turbulent body) Total estimated CD - ODB (pressure drag by ref. 8)o Total estimated CD - CDB (pressure drag by ref. 9).6 .7 .8 .9 1.0 1.1 1.2 1.3 1.4MFigure 12,- Coefficients of fore drag and its estimated componentsconfiguration A.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
