A SUMMARY OF XB-70 SONIC BOOM SIGNATURE DATA

are the pilot/copilot assignments,the maximumMach number and altitude obtainedon eachflight, andthetotal flight time. NotethatthehighestMachnumberandaltitudeflight (No. 74) of3.07 and73,000feet were achievedwith the 32nd flighl of aircraft #2 (Flight 2-32) on April 8,1966.The longestdurationof flight (No. 47), 3 hoursand40 minutes,waswith the 30thflight ofaircraft #1 (Flight 1-30)on January6, 1966.Sonicboominvolvingruns.- Of thethe two XB-70by the blacked-in(circlecirclesymbols)(square129 flightsaircraft,and squareand12 flightsII is presenteda hemeasurementsOf theseto a previouslyalmost5-yearwere acquired51 flights,39 relatedocumentedXB-70flightprogramon 51 flights(notedto the presenteffortelectronicdatabasesymbols).In Tableof the 39 flights(42 passes)for whichsonic boomswere obtainedduringthe March1965 throughMay 1966 time period, and are reportedin the present paper.Includedis the flight date, flight number, takeoff time and gross weight, total flight time, time ofsonic boom arrival at the measuringsite (accurateto within 15 minutes of actual boom time),the aircraft Mach number, altitude, and gross weight at the time of boom, and the aircraft landingweight. It is importantto note that Mach number and altitude conditionslisted for any given sonicboom run in Table II will, in most cases, not match up with those listed in Table I, since only themaximumMach number, altitude, and flight time duration attained on the flights are listed in thelatter.addedAlso shown in Table II is a column designatedDJM File #.to facilitatethe identificationof the sonic boom informationfiles and is discussedin moredetailAircraftin a later sectionFlightThis numberingsystem wascontainedon the electronicof this report.Plan and MeasurementSitesThe U.S. Air Force XB-70 Flight DemonstrationPrograminvolveda basic flight plan/groundtrack. As such, the sonic boom measurementlocationswere chosen based upon three key factors:the requirementfor an onmidirectionalover the instrumentedsite, the XB-70weather ,whichof the present1539andMeasurementtakeoffflightdurations- TheNevada;the east edgeof EdwardsEdwardsand designedsite,andboomsite.fivesonicfromweretwo sites at Edwardsdry lakeNevada.and designatedutilizedAFB, California;Of the two EdwardsLake0900twenty-four(24)at each site.measurementswere4Theand asfor the39 flightsone at Boron,areCalifornia;sites, one was locatedsets of measurementsat site 3.2 hours,hourshours.site and one was locatedEightpasses)1000-13006 milessite 3. The inset table in figure 2 lists the five site locations,acquiredofAFB,boomto aboutbeforebetweensitesthe stateslocal time to as late asminutesobtainedwere mademeasurements27a north-south(43 sonic0650 hours1 hour,pilotandwere out of EdwardsFor the 39 flightsaboutwithin2, and includestakeoffsas early as aboutmeasurementsboomwas containedin figureAll aircraftlandingand one at Coaldale,and the sets of measurementsthe Lakeas shownof the measurements2 and includeone at Beatty,wide,fromvarieda few sonicby the XB-70and Oregon.times rangedthe majoritysites.in figureIdaho,was also the designatedAlthoughlate as 1646 hours,long by 170 milesNevada,paper,hours27 minutes.illustrated- The basic flight area utilized600 milesCalifornia,radio range navigationstation to guide the XB-70flight plan, and the availabilityof radar trackingatnorthoftheir elevation,were acquiredelevationsof theseattwo

Edwards12 milessites are 2300 feet and 2700 feet above sea level, respectively.The Boron site is abouteast of EdwardsAFB and is at an elevationof 2400 feet. A total of twelve (12) sets from any obstructionsonicboomacquiredat thisat an elevationan elevationfor at sat the lowerof 4950TheBeattyfeet:site,the Coaldalethe XB-70flight track,forsite,usedonlyone(1)for eightthis was not alwaysfrom being directlyunder the aircraftto the right of the aircraft ground track.- Two basicmicrophoneof the figure,involvedflightarrangementsat the test sites and these are illustratedleft portionusedsetof(8) setsofof 4800 feet.All of the test sites were generallyflat and free1000 feet in any direction.Althoughthe intent was to locate thesite underneathsuch, the site locationsranged15 miles to the left and 8 milesboomsite.pathwerein figurepossible.Asto as muchasutilizedfor the sonic3. One arrangement,foul (4) microphones,threelocatedshownat groundlevelat 200-foot spacingsand one at a 20-foot elevation.The second arrangement,shown in the upperright portion of the figure, involved eight (8) microphones,six located at ground lever at 100-footspacings and two at a 20-foot elevationand also separatedby 100 feet. The 100-foot and nit does provideIn the majoritya measureof sonicfrom the loweris insufficientfor a measureof the measurementboombow-shockthe groundmicrophoneswerediaphragmstill parallelreflection,it is so minoroverpressure,shockover the entireit hadrise times,"milkstool"signaturessystem.was developedshown schematicallyd.c. amplifier,andlittleand signaturemadeAlthougheffectduration.few alteredand signaturesonicby NASAaboutonboomAlthoughtheand reflectedwere positionedat groundto the ground surface.This setupstool" arrangementwherein a few9 inchesthe 9-inchtheaboveheightmeasuredtheground,allowswas exmninedversionsin termsshapesmicrophonesystemusedin the 1961 time period(ref. 15).in figure 4(a), consistedof a modifiedcondenserFM tape recorderand had an overall flat frequencyThearrangementsto recordThis basicof aarrangements,placement.for any of the nonbasicinstrumentationofcoveringfrom the aspectsof the microphonebasicthefor a shocksignatureOn four runs, a very thin plasticwith the flush-mountedlevels- Thebandsof one microphonerelativelywereeffects reg'ardingoverpressurewere noted to be minor.rubbersurface.veryarrangementIn thesecomparisonsIn trumenta i0nbywith the ue to atmosphereoverpressures.microphoneslevel in a 3-foot by 3-foot board with their diaphragm parallelwas complementedon some of the later flights (8) with a "milkof thevariabilitylayers of the earth's boundarylayer).to completelyseparatethe incidentof "free-air"program,signaturethe boomanalogsystem,microphone,tuning unit,responseof from about0.1 Hz to 10 KHz.Playbacksof the analogsonic boom signaturedata into a recordingoscillographhaving 5 KHz galvanometerslimited the high frequencyresponseto 5 KHz.Thetransientresponseof the entire system was evaluated.The findings indicated that the sonic boominstrumentationsystem is capable of measuringrise times as short as 50 microseconds.Extensionof the low frequencyboomsignatureto extendend of the systemwas accomplishedthe low end frequencyKnowledgeof the frequencycourse,importantin regardto faithfullyby changingroll-offreproducethe configurationfrom aboutthe expansionportionof the microphoneof the sonicvent chamber10 Hz to 0.1 Hz (see fig. 4b).responsesof the measuring,recording,to the digitizingof the oscillographand playbacksystemscopies of the sonicis, ofboom

riginalof the opticalsignaturesscanningin reproductionrelatingto the ystem.whenaltitudeTheandgroundtypewerethe aircrafttracka 5 KHz10 KHzgalvanometer,in ordertheto maintainthetrackedand operatingby meanshardandby eachcopyaircraftsystemformat,information(to estimateconditionsof ground-basedprovidedin the originalnotConditionsand positionof informationand fuel remainingby the pilot fromthroughbe aboutand Operatingsite was acquiredincludedinvolved,conditionsPositionto the XB-70passes,playedshouldof the signatures.AircraftInformationweresystemradar and the XB-70duringthe time of theis discussedregardingweight)with respectthebelow.MachChasenumberat time of boomandwere obtainedinstrumentation.Groundtr lck. - A typical radar ground track of XB-70 #2, Flight #7 (DJM File #10) at a nominalMach number of 1.42 and at an altitude of 31,000 feet above mean sea level (MSL) is presentedinfigure5. Notethat the aircraftwas headingnorthand the measurementsite was located4500 feetto the right of the aircraft groundtrack.Also indicatedon the ground track line at 2-secondintervalsare time marks from which aircraft ground speed can be obtained.The approximatepointof originof the boompath where the booma standardatmosphereis alsoidentified(thatis, the positionof the aircraftalongwas generatedthat was measuredat the test site) and is calculated(ref. 16). In most of the sonic boom runs, the XB-70 maintainedits flightassumingstraight,steady, level flight for considerabledistancesup-trackfrom the point of origin of the boom.However,there are cases where file aircraft was in a slight turn. In all cases, however,the boomscan be ents.parameters.conditions- An indicationfor XB-70#1, Flightof the type of information#45 (DJMFile #36) obtainedflight data system,attack, and normalare presentedin figure 6. Time historiesaccelerationare shown at about 10-secondperiodsonicduringpositionof the correlatesof est.It can be seenfeet)than the radardataoriginoperatingconditionsreflectedin termsof Machof the onboardof altitude, Mach number, angle ofintervals for about a 90-secondtimeis usuallypointtakenof approachis the approximateradar control,one obtainedas the overheadfrompoint of originconditionsto theby the datanumberradartheaircraftof the sonicgroundtrackin figure6, it is apparentaltitude(Machand2.23andthat the XB-70and a slightlyof theseonboardlowerthere are two independentlygeneratedsets offiom the radar data and one from the aircrafttwo data sets, presenteddata showsMachnumbera slightly(aboutin figurehigheraltitude7, may be of(about0.02 M) than the radar2000resultssince the onboardsystem data were derived from local ambientthe radar data utilizes upper air atmosphereobservationsbased ona standardatmosphereor informationfrom actual sondefrom those of the aircraft.All of the aircraft operationalfrom the onboardby meansto the aircraftat lg.The correlationwould indicate.This is expectedconditionsin real time, whereasof zerosite (or closestonboardsteadySince the aircraft was always underdata for Mach numberand altitude,instrumentation.timeAlso notedFor the flightfeet) and was flyingonboardTheat the measurementto the measurementthe XB-7053,000boomrelatingflight data system.launchesat locationdata of the presentand times differentpaper are obtained

AtmosphericFor mostgroundweresonicboomflight tests, two typessurface-climatologicalutilizedsurfaceand documented.dataobservations(NOAA)files.(43 sonicboomsUpperDuringThesefromFollowingtheof weatherinformationthe subjectflight tests, data fiom rawinsondedata wereNationalis a descriptionrecentlyare catalogued:enhancedOceanographicwith archivalandof the atmosphericupperupperAtmospheredata associatedair andreleasesair andAdministrationwith these39 flightspasses).air temperaturein the .- During1966 time period,the XB-70,awinsondesonicupperboommeasurementair data wereeffortacquiredfromweather stations in the vicinity of the five measurementsites and also within an hour or so beforeor after the sonic boom run. The weather site was within 15 miles of the two Edwardsand Boron,California,locations.For the two Nevadasites,Beattyweatherstationsat Las Vegas and Winnemucca,100 miles south of Beatty and Winnemuccais aboutNASAdatasonicinputspredictionof temperaturerawinsonde5000boompackage;1.35.and windspecifically,feet or so aboveand perpendicularrelates to XB-70schemesaircraft(ref.informationweatherwas obtainedNevada,respectively.Las200 miles north of Coaldale.16), in existenceat the time,and, thus,a temperaturealtitudeand Coaldale,profileand correspondingcalledthis is all that wasfromnearprofilesVegassurfaceis aboutfor atmosphericgleanedlevelof the windfromcomponentsparallelstandardthe valuerawinsondeof thelaunchessonicrun.in this paper, particularlywith referenceto the influence of the atmosphereon signatureNOAA archival upper air data were acquired for the 39 days on which the sonic boomTheseto enhancefiles for eachpresenteddistortions,conducted.- In orderon electronicupperweredata.8 are provided8 whichat MachArchivalflightsairin figuretheto an altitudeto the aircraft flight track. An exampleof such data is given in figure#2, Flight #6 (DJM File #9) flying at an altitude of 33,000 feet MSLData of the type shownfromboomoccurredmeasurementstwiceperdayat1200 hours and 2400 hours at EdwardsAFB, California,and at Yucca Flat and Tonapah,Nevada.These latter two weather sites were used to representthe Beatty and caTheseFlat is aboutdata,40 mileseast of Beattylike all the atmosphericinformationon electronicfile and will consist of temperature,pressure,directionat significantaltitudes (about every 50 mb).Archivalsurface-climatologicaldata.- Surfaceand Tonapahis aboutcited in this ation,were not acquiredat the time of the actual sonic boom tests.are also availablefrom the NOAA archivalfiles for -climatologicaldata are includedon the electronicdata are providedpoint, wind speed and direction,cloud coverthat time closest to the sonic boom time.in hourly40 milesare availableand windwithand se dataand Yucca Flat andfiles of the presentintervalseast ofand containThis informationstudyeffort.temperature,is providedThedewat

SonicThissectionwill providean indicationBoomSignaturesof the qualityand characterof the measuredsonicboomsignaturetraces availableon the electronicfiles.It should be recalledthat at the timeinformationwas being acquiredand documentedin memorandumformat, its primaryuserelatingsonic boom overpressureassociatedwith the U.S. SST.confirmingand improvingthe atmospherelevels for the large aircraft to the predictedlevels that wouldThe XB-70 boom signatureresults were initiallyutilizedon the predictiveon signaturethiswasdistortion,techniquesespeciallyand providingin termsinsightof shockbeininto the influencefront rise timesofas it relatedtosubjectiveresponse.Much informationremains to be gleaned from the data set; thus, this sectionwill also address signaturevariabilityand specify wavefomlcategoriesand sonic boom signaturedescriptorsthat are consistentTypicaleachoscillographtraces.of the originalexampleof thesonic#7 (DJMmicrophoneboomelectronicof the type of sonicdocumenting#2, Flightfourof other sonic- An examplememorandais for XB-70consistedwith thoseboomtracesboomtest flightsoverthe Coaldale,File #10)arrangementsdata basesas shownthat are includedis givenin figure(refs. 6-10).in figureNevada,3.9.inThistest site whichSincetheB-58chaseaircraft was followingbehind the XB-70, its boom signaturewas also recordedat the site some3.6 secondslater. Because of the large size of the XB-70 and the fact that it is flying at a relativelylow Machwavenumber(as showngeneral,mostand altitude,for the B-58)of atmosphericthesignaturesof figureeffects.fromvariability.the XB-70is shownlevelmicrophones,microphone#42specifically,2 of XB-70(DJMobservedFile #35).on XB-70with longerof measured10. Th

The utilization of the sonic boom electronic data file in quantifying effects of atmospheric turbulence and molecular absorption on sonic boom waveforms is a major thrust. The purpose of this report is to provide a ha_d copy summary of the measured sonic boom signature data derived from the 39 supersonic flights of the XB-70 (43 passes) over .