JOURNAL OF PROPULSION AND POWERVol. 20, No. 1, January–February 2004

A Century of Ramjet Propulsion Technology Evolution

Ronald S. FryJohns Hopkins University, Columbia, Maryland 21044

A general review is presented of the worldwide evolution of ramjet propulsion since the Wright brothers rstturned man’s imagination to y into a practical reality. A perspective of the technological developments fromsubsonic to hypersonic ight speeds is provided to allow an appreciation for the advances made internationallyfrom the early 1900s to current times. Ramjet, scramjet, and mixed-cycle engine types, and their operation andrationale for use are considered. The development history and principal contributing development programs arereviewed. Major airbreathing technologies that had signi cant impact on the maturation of ramjet propulsionand enabled engine designs to mature to their current state are identi ed. The general state of ight-demonstratedtechnology is summarized and compared with the technology base of 1980. The current status of ramjet/scramjettechnology is identi ed. Ramjet and scramjet propulsion technology has matured dramatically over the yearsin support of both military and space access applications, yet many opportunities remain to challenge futuregenerations of explorers.

Introduction

H ISTORY and technologyreviewsare writtenand readfor manypractical reasons,1 including their usefulness to managers andengineers engaged in the advanced technology developments. Al-though history does not repeat itself, similar situations often havesimilar results, and thoughtful study of past technology develop-ments can help us to recognize and avoid pitfalls to make desiredoutcomes more likely. In any event, study of history lets us see cur-rent problems more clearly. Because of the cyclic nature of researchand developments, it is remarkable how many times something hadto be rediscovered.This is a real and costly problem, and without aconcerted effort to avoid it, it is apt to get worse in the future. So-lutions have been suggested, which include staying current in ourrespective elds, capitalizing on making the knowledge explosionmore tractable, and making new technology available to industry.Einstein ably characterized advances in technology as “If I haveseen farther than others, it is because I stand on the shoulders ofgiants.” Thus, this historical paper draws on the many outstandingchronicles of selected elements of airbreathingpropulsion develop-ment, assembled and presented for your appreciationof how far thehistory of ramjet technology has come in the last 100 years. Ram-jet technology has evolved from the early simple subsonic “ yingstovepipe” to its role in the complex combined or mixed cycle con-cepts embedded within military and space access vehicle designsof today. This evolution spans far more than just years; it is also a

Ronald S. Fry has madecontributionsto combustionand propulsiontechnology for the developmentof advancedairbreathing military applications for over 30 years. He has made contributions to the developmentof conventionalstandoff missiles, cluster weapon systems involvingself-forging fragment technology, and military weapon systemsinvolving fuel–air explosive and insensitive high-explosive technologies while in the U.S. Air Force from 1974 to1979. He led and contributed to dramatic advances in the U.S. state of the art in metallized solid fuel ramjettechnology while with Atlantic Research Corporation from 1979 to 1993. More recently, he has contributed to thedevelopmentof aU.S.nationalplanforthe advancementofhypersonics science andtechnology.R. S. Fry is currentlya Senior Research Engineer at JohnsHopkins University, Chemical PropulsionInformation Agency, a Departmentof Defense Information Analysis Center. He has received awards for outstanding sustained achievement from theJANNAF Airbreathing Propulsion Subcommittee, the National Defense Service Medal for Active Duty Serviceduring the Vietnam War, and multiple U.S. Air Force commendation medals for outstanding performance. Hehas a B.S. in aerospace engineering and two M.S. in engineering in aerospace engineering and naval architectureand marine engineering from the University of Michigan. R. S. Fry performed his graduate work under thementorship of A. Nicholls, whose early demonstration of stabilized detonation waves in a supersonic hydrogen–airstream contributed to the feasibility of supersonic combustion ramjet technology.He is a Senior Member of AIAA.

Received 25 August 2003; revision received 20 November 2003; accepted for publication 19 November 2003. Copyright c° 2003 by Ronald S. Fry. Publishedby the American Institute of Aeronautics and Astronautics, Inc., with permission. Copies of this paper may be made for personal or internal use, on conditionthat the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0748-4658/04$10.00 in correspondence with the CCC.

vast revolution in development technologies. A brief review of thisevolution, is provided; a rigorous presentation is beyond the scopeof this manuscript.

The history of man’s desire to y has evolved from the imagi-nation of Greek mythologists through the thoughts, designs, data,and experiencesof many notable individuals, all whom contributedin various ways to the Wright brothers’ rst demonstration of level ight under power in 1903. It would seem this was the catalyst thatinitiated the evolution of ramjet technologybecause the rst knownreference to ramjet propulsion dates from 1913.

Review of the worldwide evolution of ramjet technology beginswith ramjet engine types, operation, and motivation. Ramjet de-velopment history is reviewed. Principal internationaldevelopmentprograms are reviewed. Discussionsare concluded with a review ofthe maturation of ramjet design technology,and the general state oframjet/scramjet/mixed cycle technology.

Key enabling technologies, components, or events that had sig-ni cant impact on the maturation of ramjet and scramjet propulsionand engine designs are summarized in Table 1. These signi cantelements are discussed in further detail throughout the paper andinclude the air induction system, vehicle aerodynamics,combustordesign and materials, fuels, injection and mixing, solid propellantboosters, ejectable and nonejectable components, thermochemicaland engine performance modeling, and ground-test facilities andmethods.

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Table 1 Top 10 enabling technologies for ramjet propulsion

1) High speed aerodynamics analysisCFD code analysis and validation methodologies(external and internal ow)Improved design tools and techniques

2) Air induction system technologyFixed and variable geometrySubsonic, internally/externally ducted supersonicand dual- owpath designsMixed cycle owpath developmentImproved design tools/integration with the airframeImproved materials, especially in the cowl region

3) Combustor technologyImproved design tools and techniques, such asmapping fuel and heat-transfer distributionsImproved insulators (ablative, nonablative)Advanced structural materialsCombustion ignition, piloting and ameholding, and mixing

4) Ramjet/scramjet fuelsHigher-energy liquid and solid fuelsLow-temperature liquid fuelsEndothermic fuels

5) Fuel management systemsLiquid fuel injection and mixingImproved injectors; wider range of operation,tailoring of atomization, and spray distributionSolid ramjet and ducted rocket fuel grain designSolid ducted rocket fuel value designVariable-geometry injection systems, especially for DRImproved feed systems, including turbopumpsImproved feedback control systems

6) Propulsion/airframe integration, materials, and thermal managementCFD code analysis and validation methodologiesHigh-temperature metals and alloysHigh-temperature structuresPassive and active coolingCarbon–carbon and ceramic metal matrix composites

7) Solid propellant booster technologyTandem boostersIntegral rocket–ramjet boostersSelf-boosted ramjet (mixed cycle RBCC, TBCC, etc.)

8) Ejectable and nonejectable component technologyInlet and port coversFixed- and variable-geometry nozzle technology

9) Thermochemical modeling and simulation developmentThermochemical tablesRamjet cycle analysis and performance modeling

10) Ground-test methodologiesDirect-connectSemifreejet and freejetAir ow quality improvementsInstrumentation advancesComputational tools and ight-test correlation

Ramjet Design and Concept of OperationDescription of Ramjet Propulsion Systems

Simple in concept, the ramjet uses xed components to compressand accelerate intake air by ram effect. The ramjet has been calleda ying stovepipe, due to the absence of rotating parts that charac-terize the turbine engine. The ramjet gets its name from the methodof air compression because it cannot operate from a standing startbut must rst be accelerated to a high speed by another means ofpropulsion. The air enters the inlet and diffuser, which serve thesame purpose as a compressor. Compression depends on velocityand increases dramatically with vehicle speed. The air delivered toa combustion chamber is mixed with injected fuel. This mixture isignited and burns in the presenceand aid of a ameholder that stabi-lizes the ame. The burning fuel imparts thermal energy to the gas,which expands to high velocity through the nozzle at speeds greaterthan the entering air, which produces forward thrust. Because thruststrongly depends on compression, the ramjet needs forward veloc-ity to start the cycle. Typically a booster rocket provides this, eitherexternally or internally. All modern ramjet missiles use the inte-gral rocket–ramjet concept, which involves solid propellant in the

Fig. 1 Elements of ramjet power cycle and owpath.

aft combustion or mixing chamber to boost the system to ramjet-operating conditions. On decay of rocket pressure, the nozzle andassociatedcomponentsare jettisonedand ramjet power begins. Lowejecta booster design trades involve using the less ef cient ramjetnozzle in a tradeoff for volume, performance, and operational con-siderations. Elements of the ramjet power cycle and owpath fromAvery2 and Thomas3 are shown in Fig. 1. Note that variation instation nomenclature began early.

A typical Mach number–altitude airbreathing ight corridor isshown4 in Fig. 2. Design challenges are compounded by ight con-ditions that become increasingly severe due to the combination ofinternalduct pressure,skin temperature,and dynamicpressureload-ing. These constraints combine to create a narrow corridor of possi-ble conditionssuitable for ight based on ram air compression.Rel-ativelyhigh dynamicpressureq is required,compared to a rocket, toprovide adequate static pressure in the combustor (generally morethan 12 atm) for good combustion and to provide suf cient thrust.As speed increases, there is less need for mechanical compression.The upper boundary is characterized as a region of low combus-tion ef ciency and narrow fuel/air ratio ranges thereby establishinga combustion limit. The lower boundary is a region of high skintemperature and pressure loading thereby establishing design andmaterial limits. The far right, high Mach number edge of the enve-lope is a region of extreme dissociation,where nonequilibrium owcan in uence compression ramp ow, induce large leading-edgeheating rates, and create distortionsin the inlet ow, while in uenc-ing fuel injection and mixing, combustion chemistry, nozzle ow,and, ultimately, performance. A region of low compression ratio isexperienced at the very low Mach number region. The current stateof the ramjet operational envelope, examined in further detail in the nal section, has seen dramatic expansions from its early history,through the 1980s, to today.

The basic ramjet engine consists of an inlet, diffuser, combustorand exhaust nozzle (Fig. 1). The inlet collects and compresses airand conducts it via the diffuser to the combustor at reduced velocitythereby developing ram pressure and an elevated temperature. Thecombustoradds heat and mass to the compressedair by the injectionand burning of fuel. Finally, the nozzle converts some of the energyof the hot combustion products to kinetic energy to produce thrust.Because the ramjet depends only on its forward motion to compressthe air, the engine itself has no moving parts and offers higher Machnumber capability than turbojet engines. However, unlike a turbojetor rocket engine, the ramjet requires an auxiliary boost system toaccelerate it to its supersonic operating regime.

There are numerous reasons for using airbreathing engines in-stead of rockets: All of the oxidizer necessaryfor combustionof the

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Fig. 2 Typical airbreathing ight corridor.

fuels comes from the atmosphere, the engines produce much higherengine ef ciency over a large portion of the ight and a longerpowered range than rockets, there is thrust modulation for ef cientcruise and acceleration, they have the ability to change ef cientlypowered ght path and maneuverability, and they are reusable notjust refurbishable.An additional feature for space access is a shortturnaroundtime, with a potentialcost reductionof 10–100 times perpound of payload.

Possible applications for scramjets include hypersonic cruise ve-hicles, hypervelocity missiles, and airbreathing boosters for spaceapplications.Hydrogen fuel is desirable for high Mach number ap-plicationsdue to its high-energycontent,fastreactions,andexcellentcooling capabilities. For hypersonic missile applications and air-breathing systems operating below Mach 6, hydrocarbon fuels arepreferredbecauseof volumetricand operationalconstraints.Makinguse of the enhanced cooling capabilities of endothermic hydrocar-bon fuels can increase the maximum speed for hydrocarbon-fueledmissiles and vehicles to Mach 8. Attractive mission identi ed forscramjet-powered vehicles include a Mach 8 cruise missile as astandoff fast-reaction weapon or long-range cruise missile or boostpropulsionfor standofffast-reactionweapon or airbreathingboosterfor space access.

Subsonic Combustion (Ramjet) Cycle BehaviorConceptual schematics of subsonic combustion ramjets and hy-

bridor combinedcycle derivativesare shown in Figs. 3 and 4 follow-ing Waltrup,5 whose past contributionshave been most noteworthy.Figure 3a shows the traditionalcan-typeramjet (CRJ), liquid-fueledramjet (LFRJ), and gaseous-fueled ramjet (GFRJ) with a tandembooster attached.A tandem booster is required to provide static andlow-speed thrust, which pure ramjets alone cannot provide. Here,M0 > M1 > 1, but the air is diffused to a subsonic speed (typicallyMach 0.3–0.4) through a normal shock system before reaching sta-tion 4. Fuel is then injected and burned with the air at low subsonicspeeds before reaccelerating through a geometric throat (M5 D 1)and exit nozzle (M6 > 1). The position of the normal shock systemin this and all subsonic combustion ramjets is determined by the ight speed, air captured, total pressure losses up to the inlet’s ter-minal normal shock, amount of heat addition, inlet boundary layerand ow distortion, and exit nozzle throat size.

A more recent alternative to this concept is to use a commoncombustion chamber, commonly referred to as an integral rocketramjet (IRR), for both the boost and sustain phases of ight. Thisgenerally requires a dump-type rather than a can-type combustor,but the cycle of operationof the ramjet remains the same. Figure 3bis a schematic of this concept for a liquid-fueled IRR (LFIRR) andFig. 3c shows a solid-fueled IRR (SFIRR). In some applications,SFIRRs are preferred over LFIRRs, GFRJs, or CRJs because ofthe simplicity of the fuel supply, but only when the fuel throttlingrequirements are minimal, that is, when ight altitude and Mach

a) Conventional can combustor ramjet (CRJ)

b) Integral rocket/dump combustor ramjet (LFIRR)

c) SFIRR

d) ADR

Fig. 3 Schematics of generic ramjet engines.

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a) ATRJ

b) ATR

c) ERJ

Fig. 4 Schematics of generic hybrid (mixed cycle) ramjets that pro-duce static thrust.

number variations are limited. The air-ducted rocket (ADR), shownin its IRR form in Fig. 3d, operates under the same engine cycleprinciples. Here, a fuel-rich monopropellant is used to generate alow-to-moderatepressuregaseousfuel supply for the subsoniccom-bustor. The choice of an ADR is generally a compromise betweenthe fuel supply simplicity of an SFIRR and the unlimited throt-tleability of the LFIRR, GFRJ, or CRJ. An ADR is generally usedwhen the total fuel impulse does not adversely impact the poweredrange. The performance of the LFIRR or GFRJ is typically superiorto the other four variants shown.

Although the ramjets shown conceptually in Figure 3 are viablevehicle propulsionsystems,none can produce static thrust. Figure 4shows three types of hybrid or combined cycle ramjet engine cyclesthat can. The rst embeds a turbojet engine within the main ramjetengine and is usually liquid fueled and called an air-turboramjet(ATRJ) (Fig. 4a). Here, the turbojet produces the required static andlow-speed thrust for takeoff (and landing if required) that may ormay not be isolated from the main ramjet ow at supersonicspeeds.An alternative to the ATRJ is the air-turborocket (ATR) in whicha low-to-moderate pressure rocket motor is used to drive a turbineand to providea gaseous fuel for the ramjet (Fig. 4b). The turbine, inturn, drives a compressor, the combinationof which produces staticthrust. At supersonicspeeds, the compressor,again,may be isolatedfrom the main ramjet ow and the turbine idled so that the vehiclecan operate as an ADR. The nal hybrid ramjet cycle capable ofproducing thrust is ejector ramjet (ERJ) shown in Fig. 4c. Here, arocket motor or gas generator produces a high-pressure, generallyfuel-rich, supersonicprimary or ejector ow that induces secondaryair to ow through the engine even at static conditions.The ejectoref uent and air then mix and burn (at globally subsonic speeds) and nally expand in the convergent–divergent exit nozzle.

There are three basic types of integral/rocket ramjet engines,namely, the LFRJ, the solid-fueled ramjet (SFRJ), and the ductedrocket (DR) as shown in Fig. 3. In the LFRJ, hydrocarbon fuel isinjected in the inlet duct ahead of the ameholder or just beforeentering the dump combustor. In the SFRJ, solid ramjet fuel is castalong the outer wall of the combustor with solid rocket propellantcast on a barrier that separates it from the solid ramjet fuel. In thiscase, fuel injection by ablation is coupled to the combustion pro-cess. An aft mixer or other aid is generally used to obtain goodcombustion ef ciency. The DR is really a solid fuel gas generatorramjet in which high-temperature, fuel-rich gasses are supplied tothe combustor section. This provides for ame piloting and utilizesthe momentum of the primary fuel for mixing and increasing to-

tal pressure recovery. Performance of the DR may be improved byaddinga throttlevalveto the primary fuel jet, therebyallowing largerturndown ratios. This is known as a variable ow DR (VFDR). Thereader is directed to Zucrow,6 Dugger,7 and others8 for additionalramjet fundamentals.

Supersonic Combustion (Scramjet) Cycle BehaviorTurning now to supersonic combustion engines, Fig. 5 shows a

generic scramjet engine and two hybrid variants. Figure 5a shows atraditional scramjet engine wherein air at supersonic or hypersonicspeedsis diffusedto a lower, albeitstill supersonic,speedat station4.Fuel (eitherliquidor gas) is then injectedfromthe walls (holes,slots,pylons, etc.) and/or in-stream protuberances (struts, tubes, pylons,etc.), where it mixes and burns with air in a generally divergingarea combustor. Unlike the subsonic combustion ramjet’s terminalnormal shock system, the combined effects of heat addition anddiverging area in the scramjet’s combustor, plus the absence of ageometric exit nozzle throat, generate a shock train located at andupstream of the combustor entrance, which may vary in strengthbetweenthe equivalentof a normaland no shock.The strengthof thisshock system depends on the ight conditions, inlet compressionorinlet exit Mach number M4 , overall engine fuel/air ratio ER0 , andsupersonic combustor area ratio (A5=A4/.

The uniquecombinationof heatadditionin a supersonicairstreamwith a variablestrengthshocksystemplus the absenceof a geometricthroat permits the scramjet to operate ef ciently over a wide rangeof ight conditions, that is, as a nozzleless subsonic combustionramjet at low ight Mach numbers, M0 D 3–6, and as a supersoniccombustion ramjet at higher ight Mach numbers, M0 > 5. At lowM0 and high ER, the combustionprocessgeneratesthe equivalentofa normal shock system and is initially subsonic, similar to that of aconventionalsubsoniccombustionramjet, but accelerates to a sonicor supersonic speed before exiting the diverging area combustor,which eliminates the requirement for a geometric throat. As ERdecreases at this same M0 , the strength of the precombustionshocksystem will also decrease to the equivalentof a weak oblique shock,and the combustion process is entirely supersonic.At high M0 , thestrength of the shock system is always equivalent to either a weakoblique shock or no shock, regardless of ER. This is referred to asdual-mode combustionand permits ef cient operationof the enginefrom M0 D 3 to M0 D 8–10 for liquid hydrocarbon fuels and up to

a) Supersonic combustion ramjet

b) DCR

c) ESJ

Fig. 5 Schematics of generic supersonic combustion engines.

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orbital speeds for gaseous (hydrogen) fuels. The upper limit forthe liquid-fueled cycle is, of course, due to energy consumptionby dissociating and ionizing species at elevated temperatures thatcannot be compensated for by additional fuel as in the case of, forexample, a diatomic gas such as hydrogen.

The supersonic combustion ramjet (scramjet) engine (Fig. 5) isa hypersonic airbreathing engine in which heat addition, due to thecombustionof fuel and air, occurs in a ow that is supersonicrelativeto the engine. The potential performance of scramjet engines usinghydrogen fuel and variable geometry covers a wide Mach numberrange, from M0 D 4 to 15C. Scramjet missiles using hydrocarbonfuels are usually of xed geometry, except for inlet starting provi-sions, to minimizeweightandcomplexity.Variablegeometryscram-jets can improve performance somewhat and are more suitable forvehicle applications where a broad Mach number range is needed.Both axisymmetric and two-dimensional scramjets have been de-veloped. Axisymmetric engines are usually lighter weight but aremore representative of high drag pod-mounted engines, whereastwo-dimensionalengines can be more easily integrated into a vehi-cle body.

Unlike a conventionalramjet engine, where the incoming air owis decelerated to a subsonic speed by means of a multishock intakesystem, the ow in a scramjet is allowed to remain supersonic.In this case, the amount of compression performed by the inletcan be signi cantly reduced and normal shock losses eliminatedwith a corresponding increase in total pressure recovery. This canmore than compensate for the high heat addition losses (Rayleighlosses) encountered. In addition, the reduced level of compressionresults in lower static temperatures and pressures at the entry to thecombustor, which reduces the severity of the structural loads. Thereduced temperature allows more complete chemical reaction inthe combustor and can reduce the losses due to nite-rate chemicalreactions in the nozzle.9 In reality, ow in the scramjet combustorcan be mixed ow at this Mach number with regions of subsonic ow near surfaces and supersonic ow in the core.

Two attractive approaches for providing (a broader Mach num-ber operational range) scramjets with a lower Mach number ca-pability are the dual-mode scramjet (DMSJ) engine in which bothsubsonic and supersonic modes of combustion are possible withinone combustor and the hypersonic dual-combustor ramjet (DCR)engine. The dual-mode supersonic combustion ramjet engine wasproposed in the early 1960s, U.S. Patent 3,667,233 by Curran andStull, and was subsequently developed by the Marquardt Corpo-ration (Marquardt) in their early DMSJ Engine. James Keirsey ofJohns Hopkins University/Applied Physics Laboratory (JHU/APL)invented the DCR cycle in the early 1970s.

Characterizationof the complex ow- eld in DMSJs ( rst intro-duced by Curran and Stull in 1963) has been the subject of a num-ber of previous investigations. Billig and Dugger,10 Billig et al.,11

and Waltrup and Billig12;13 rst provided analysis of experimentaldata and analytic tools, which allow a prediction of the ow eldsuch as upstream interaction and required isolator length for mid-speed scramjet combustorcon gurations.A well-knowncorrelationfor upstream interaction distance was formulated with dependencespeci ed in terms of heat release (downstream pressure rise) andthe entering momentum characteristics of the boundary layer be-fore isolator separation. Heiser and Pratt14 provide a thorough andextended treatment of dual-mode ow elds.

Although the scramjet offers these unique capabilities, it also re-quires special fuels or fuel preparation to operate ef ciently aboveM0 D 6 because of low static temperatures and short combustorresidence times (

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Fig. 6 Characteristic performance by engine type.

Fig. 7 Engine options as function of Mach number.

over the rst forty years and supplemented his work in 1999.21

There has been a considerable amount of laboratory testing andground testing of scramjet engines in various countries, describedin the citedreferencesand brie y reviewedwithin this paper.A basicunderstanding of the supersonic combustion process has improvedsigni cantly over the years.

Selection of engines for high speed vehicles is dependent on theintended mission and the speed range of interest. Figure 7 showsa summary of various options as a function of Mach number. Thechoice of propulsion options and the operating range can be broad-ened by combining differentpropulsion options to create combinedcycle or combination cycle engines, as discussed in the precedingsections.

Rationale favoring a Mach 6–8 missile includes providing sub-stantially improved capabilities over a Mach 4 missile in terms ofranges attained within a given ight time or less ight time fora given range with the accompanying improved survivability. Thehigher kinetic energy and speed are additionally essential for in-creasing the probability of neutralizing various target types.

Having introduced the ramjet and scramjet cycles, let us nowreturn to the evolution of ramjet engines for powered ight.

History of Ramjet and Scramjet DevelopmentSubsonic Combustion History

Many excellent historical accounts chronicle the early years oframjet development.2;5;20;22;23;35;36 Highlights of this history are re-viewed here. Avery2 was among the rst to review progress fromthe beginning years, while focusing on a 25-year period from theearly 1930s, when testing of practical designs rst began in 1955.Waltrup5 provideda very thoroughreviewof internationalairbreath-ing engine development from the beginning years to 1987, withan emphasis on the development of supersonic combustion ramjet(scramjet)engines. In 1996, Waltrup et al. provideda historyof U.S.Navy ramjet, scramjet and mixed-cyclepropulsiondevelopments.22

Kuentzmann and Falempin provide an account of French and inter-national ramjet and scramjet development history.24;34

The history of ramjet concepts began in the early 1900s, withactual testing not beginningfor another 30 years. While many inter-national researchers were focusing on solving the thrust to weightchallenges of internal combustion engines for ight, Lake (in theUnited States) and Lorin (in France) and their colleagues were ex-amining jet propulsion devices that did not have in-stream obstruc-tions, currently called ejector ramjets. The rst patent of a sub-sonic ramjet cycle device, an ejector ramjet, was issued to Lakein 1909. Lorin published the rst treatise on subsonic ramjets in1913, but did not address high subsonicor supersonic ight. Morize(France,1917)andMelot (France,1920)engineeredthe ejectorram-jet concept, with testing occurring in France during World War I(WWI) and in the United States in 1927. Although tests demon-strated an increase in static thrust, interest in this engine cyclewaned until the late 1950s. Carter (in Great Britain) patented the rst practical ramjetlike device for enhancing the range of artilleryshells in 1926. Carter’s designs showed considerable insight forthe time and employed a normal shock inlet with either a conicalnose/annular duct or central cylindrical duct. The rst recognizableconical-nosedLFRJ patentwas given to Fono (in Hungary) in 1928.These designs included convergent–divergent inlet diffuser, fuel in-jectors, ameholders,combustor, and convergent–divergentnozzle.Althoughthese systems were designedfor supersonic,high-altitudeaircraft ight, they did not advance beyond the design stage.

Actual construction and testing of viable ramjet designs did notoccur until the mid-1930s in France, Germany, and Russia. Leduc(France) ground tested a conical ramjet up to Mach 0.9. Work ona full-scale ramjet-powered aircraft had begun by 1938, with com-ponent ground tests conducted up to Mach 2.35 by 1939. WorldWar II (WWII) temporarily halted further testing. In Germany,Trommsdorff led a successful effort in 1935 to develop artilleryshells poweredby multiple-shock,conical-inletLFRJs. These shellsactually accelerated from Mach 2.9 to 4.2 in tests conducted in1940. Sänger and colleagues (in Germany) examined designs foran aircraft-launched ramjet-powered cruise missile but never con-structed or tested one. The Germans did eld the rst operationalramjet-powered missile in the form of the V-1 buzzbomb poweredby a subsonic ight speed pulsejetengine.Strechkin(in Russia) alsobegangroundtestingof ramjet componentsat speedsup to Mach 2 inthe 1930s. Under Merkulov’s direction, Russia successfully ighttested a tandem-boosted ADR using magnesium/aluminum solidfuel in 1939. These activities were subsequently replaced with de-signs to augment the thrust of existing aircraft using wing-mountedramjet pods. Attempts were also thwarted by the events of WWIIfollowing initial ight testing in 1940. Reid (in the United States)and Marquardt (in Great Britain) began ramjet development effortsin the early1940sin the form of aerial-guidedprojectilesandaircraftperformanceaugmenters,respectively.These effortscontinuedafterWWII and resulted in weapon systems such as the Bomarc (U.S. AirForce), Talos (U.S. Navy), and Bloodhound (Great Britain) antiair-craft missiles, as well as numerous basic and applied experimentsat national research centers in both countries.

The ramjet engine began to receive attention during the second-half of the 1940s and reached a relative peak during the 1950s witha number of operational systems being deployed.France developedseveral operational ramjet missiles (VEGA, CT-41, and SE 4400)in the late 1950s and early 1960s. The ramjet, always needing anauxiliary propulsion system for starting, got squeezed between im-proved turbine engines and rockets during the 1950s and did notrecover until reignited by the Russian SA-4, SA-6 and SS-N-19design revolutions in the late 1960s and early 1970s. This periodwitnessed a surge in development activity by the United Statesand Russia in the development of low-volume IRR missile designs.The Russian activity led to the operational missiles SS-N-22 andAS-17/Kh-31.

The ramjet received expanded international development at-tention beginning in the 1980s, which continues today. Duringthe 1980s France developed the operational Air-So MoyennePortee-Ameliore (ASMP) and ight-tested Missile Probatoire Stato

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Rustique (MPSR)/Rustique. The United States invested effort in su-personic low-altitude target (SLAT) and VFDR. During the 1990s,France continuedits long history of developmentactivity in ramjetswith activity on MARS, MPSR/Rustique, Anti-Naivre Futur/Anti-Navire Nouvelle Generation ANF/ANNG, Vesta, and the next-generation ASMP-A. The People’s Republic of China began de-velopment of a long-rangeantiship variant (C-301) of its C-101 andthe more advanced Hsiung Feng. South Africa began developmentof a long-range air-to-air missile (LRAAM). Russia continued todemonstrate its understanding of this technology by beginning thedevelopment of AA-X-12 and SS-N-26. Israel entered the ramjetcommunity by beginningdevelopmentof a ramjet-powered versionof Gabriel for extended range. Germany began development of anantiradiationmissile ARMINGER. India began development of thePJ-10/Brahmos, a derivative of the Russian SS-N-26. The 2000shave seen this developmentactivity continueand expand yet furtherin the United States supersonicsea skimming target (SSST), genericsupersonic cruise missile (GSSCM), and high-speed antirachationdemonstration (HSAD), The United Kingdom beyond visual rangeair-to-airmissile (BVRAAM/Meteor),France(MICA/RJ), andelse-where. These and other internationaldevelopmentprograms are re-viewed in further detail later in this paper as a means of betterunderstanding the evolution in ramjet technology.

Supersonic Combustion HistoryMany excellenthistoricalaccountschronicleinternationalscram-

jet development. Curran provided a review of the rst 40 years ofinternational scramjet engine development in 1997.20 Waltrup re-viewed internationalsupersonic combustiondevelopment in 1987,5

and Waltrup et al. reviewedU.S. Navy scramjet and mixed-cycleen-gine development in 1996.22 Van Wie25 chronicled the 59-year his-tory of JHU/APL contributions to the development of high-speedvehicles, highlighting ve great APL propulsion pioneers, Avery,Dugger, Keirsey, Billig, and Waltrup in 2003. Andrews26 provideda very thorough historical review of scramjet developmentand test-ing in the United States in 2001. McClinton et al.28 provided aworthy review of engine development in the United States for spaceaccess applications in 2001. Escher27 provided an excellent reviewof U.S. developments in combined airbreathing/rocket propulsionfor advanced aerospace applications in 1999.

Ef cient airbreathing engines for operation into the hypersonicspeed regime have been studied for over 40 years. The heart of theseengine systems is the supersonic combustion ramjet (scramjet) cy-cle. Scramjet engine concept development, test facilities and instru-mentation development, analysis method re nement, and compo-nentand enginetestinghave been pursuedcontinuallysince the early1960s. Efforts to integrate the scramjet with higher and lower speedpropulsion devices for space access have been investigatedsporadi-callysincethe 1960sandcontinuouslysince1984.McClintonetal.28

reviewed U.S. hypersonic airbreathing launch vehicle propulsiondevelopment efforts. The review addresses experiences and majoraccomplishments of historic programs; the goals, coordination be-tween, and status of current programs in 2001; and a view of thefuture of hypersonic airbreathing propulsion development in theUnited States for future launch vehicles.

In 2001 McClinton et al.28 discussed scramjet development inthe United States in terms of generations, rst generation 1960–1973, second generation 1969–1984, third generation 1984–1994,and fourth generation from 1995-today. Each generation wasdistinguishedby its unique contributionsof the level of understand-ing of supersonic combustion.

First Generation Scramjet Development (Beginning: 1960–1973)The origins of employing combustion in supersonic ows in the

United States can be traced back to interest in burning fuels in exter-nal streams to either reduce the base drag of supersonic projectilesor to produce lift and/or thrust on supersonic and hypersonic air-foils in the early 1950s.5 In Europe, interest in supersonic combus-tion paralleled that in the United States throughout the 1960s and1970s. The most extensive of the early ( rst generation) scramjetdevelopment programs in the United States was the NASA hyper-

sonic research engine (HRE) program. The HRE program, startedin 1964, was crafted to develop and demonstrate ight-weight,variable-geometry, hydrogen-fueled and- cooled scramjet enginescramjet technology. In France, both fundamental and applied re-search was being pursued, with initial connected pipe testing beingconducted by ONERA at Mach 6 conditions in the early 1970s. InGermany, most of the reported work was on supersonic combustionwas of a more fundamental nature. Russia had an extensive pro-gram in supersonic combustion and scramjet propulsion since the1960s. Canadian interest in supersonic combustion began in 1960at MacGill University in hypersonic inlet aerodynamics and gun-launched scramjet ight testing.

The rst Generationwitnessed the start of several major scramjetdevelopment programs in the U.S. during the mid-1960s, follow-ing the rst scramjet demonstration by Ferri in 196029 and stud-ies that veri ed the bene ts of scramjet propulsion. The U.S. AirForce, NASA, and U.S. Navy sponsoredprograms tested six scram-jet engines/ owpaths throughmajor contractsat Marquardt,GeneralElectric, United TechnologyResearch Center (UTRC), Garrett, andGeneral Applied Sciences Laboratory (GASL). Engine owpathsfrom all of these contractors were tested at low hypersonic speeds(up to Mach 7). Most tests utilized hydrogen fuel, but the U.S. AirForce also funded hydrocarbon-fueledscramjet tests for missile ap-plications,and the U.S. Navy (APL) performed severaldifferenthy-drocarbonstudies in the SupersonicCombustion Ramjet (SCRAM)project. However, the U.S. Air Force withdrew from scramjet re-search and development, not to return until the National AerospacePlane (NASP) program in 1984. Following successful demonstra-tion of scramjet performance, operabilityand structural/systems in-tegration, NASA turned to developmentand validation of airframe-integrated engine owpaths.

Second Generation Scramjet Development (Airframe Integration:1973–1986)

The technology development focus in the United States shiftedin the second generation to integration of hydrogen-fueled scram-jet engines on a hypersonic vehicle following the rst generationhypersonic propulsion demonstrators. A Mach 7 cruiser con gura-tion was selected with turbojet low-speed and scramjet high-speedsystems, in an over–under arrangement. NASA Langley ResearchCenter (LaRC) led this effort, which focused on the sidewall com-pression scramjet engine. This engine included fuel injector strutsand xed geometry to minimize weight. Much of the research ef-fort was placed on tool development. This included facilities, testmethodologies, cycle analysis, data analysis, and computational uid dynamics, (CFD). This time frame was also characterized bya downturn in research in the United States, and facility availabil-ity became an issue. Therefore, facilities were developed at NASALaRC for ef cient scramjet testing. Modest-sized facilities also re-mained available at GASL and were used to handle higher pressurevalidation tests. Component test facilities were also developed, in-cluding a combustion-heateddirect-connectcombustor facility anda Mach 4, high-pressure inlet test facility.

Component tests were performed to establish rules-of-thumbdesign models/tools. These models30 were not incorporated intothe U.S. scramjet toolbox until the late 1980s. Component testswere also used to develop databases for veri cation of analyticaland computational methods. These second generation cycle analy-sis methods are simplistic by today’s standards of CFD methods,nevertheless feature internal calculations such as shear and heattransfer to the combustorwall, fuel mixing, and estimated nite-ratechemistry effects on combustion. Scramjet tests for the three-strutengine were performed at NASA LaRC and GASL.

Aerodynamic and propulsion-airframe integration (PAI) assess-ment is required to set scramjet performance requirements. Aero-dynamic and PAI tests were performed to quantify inlet capture,external nozzle performance,and scramjet-poweredvehicle perfor-mance. Aerodynamic wind-tunnel tests were performed at ightconditions up to Mach 8. Structural designs for the sidewall com-pression engine were developed, including primary structure, cool-ing jackets, and thermal management. These designs used cooling

34 FRY

channels rather than the offset n approach used in the HRE, butmaintained the high-temperaturesteel. France launched the ESOPEprogram, inspired at least in part by NASA’s HRE activity.

During the mid-1970s, the sidewall compression owpath testsdemonstrated the required thrust, operability, and fuel cooling re-quirementsto allow a crediblevehicledesign.About 1000tests wereperformed on three engines. In addition, these studies validated thepredicted scramjet performance and providedsome justi cation forstarting the NASP program.

Scramjet module and direct-connect research and testing usinggaseoushydrocarbonfuels was startedat NASA LaRC in late 1970sand was subsequently interrupted by the NASP program. AfterNASP, the U.S. Air Force took the lead in this area. Tests wereperformed using methane, ethane, and ethylene injected from thehydrogen fuel injectors.

Third Generation Scramjet Development (NASP: 1986–1994)In the early 1980s the U.S. NASP program was formulated,

with the objectiveof developinga single-stage-to-orbit “hypersoniccombined-cycleairbreathingcapable”31 engine to propel a researchvehicle, the X-30. The NASP program promise of ying a single-stage vehicle, powered by a combined cycle engine that utilizedscramjet operation to Mach 25 was aggressive, when the state oftechnology in 1984 is considered.Subsequentdevelopmentactivitybacked off such an aggressive approach. Neither scramjet enginesnor owpaths had been tested above Mach 7. In addition, no cred-ible, detailed analysis of scramjet performance, operability, loads,or structural approaches had ever been performed for ight pastMach 7. Also, what was good enough for Mach 7 vehicle opera-tion was not re ned enough for the low-thrust margin (energy fromcombustion vis-à-vis air kinetic energy) at double-digit ight Machnumbers.30 In other words, second generation scramjet technologywas a good starting point, but considerablere nement and develop-ment was needed.

Internationalactivity in this period includedmany developments.Germany began developmentof Sänger II in the late 1980s as a pro-posedtwo-stage-to-orbit(TSTO) conceptvehicle.Japanpursuedde-velopmentof combined cycle engine technologyfor yback boosterTSTO applications. Russia developed Kholod as a rst generationhypersonic ying laboratory,derived from the SA-5 (S-200 family)surface-to-air missile. Russia initiated the comprehensive hyper-sonic research and development in the ORYOL program with thepurpose of developing combined propulsion systems for advancedreusablespace transportation.Finally,Russiaemployedanother rstgeneration ight-test vehicle GELA Phase I testbed for the devel-opment of Mach 3 ramjet missile propulsion systems. France initi-ated PREPHA aimed at developinga knowledge base on hydrogen-fueled dual-mode ramjet technology for single-stage-to-orbit appli-cations.

Fourth Generation Scramjet Development (Resurgence: 1995–Today)Following the NASP program, three new directions were taken

in the United States. The U.S. Air Force went back to hydrocarbon-fueled scramjet missiles; NASA aeronautics went on to demon-strate the most advanced parts of the NASP propulsion technology,that is, scramjets; and the NASA rocket community embraced theengine technology afforded by rocket-airbreathing combined cy-cle engines. These three programs, HyTech/HySet, Hyper-X, andSpaceliner, are mentioned here, and their program contributionsand status are reviewed later. The United States has since incor-porated the development of high-speed airbreathing technologywithin an overarching approach called the National Aerospace Ini-tiative (NAI). It is a partnership between the Department of De-fense (DOD) and NASA designed to sustain the U.S. leadershipthrough technology development and demonstration in three pil-lar areas of high speed/hypersonics, space access, and space tech-nology. Ronald Sega, Director of the U.S. Defense Research andEngineering Agency (DARPA), points out that NAI will providemany bene ts: never-before-available military capabilities to sat-isfy a broad range of needs; technologies required to provide re-liable and affordable space transportation for the future, develop

launch systems, and satisfy exploratorymission needs; and, nally,spur innovation in critical technology areas and excite and inspirethe next-generationhigh-technologyscience and engineeringwork-force in the United States.

HyTech/HySET. The goal of the U.S. Air Force Hyper-sonic Technology/Hydrocarbon Scramjet Engineering Technology(HyTech/HySET) program is to advance technology for liquidhydrocarbon-fueledscramjets.Although this technologywill be ap-plicable to scramjet-powered strike, reconnaissance, and space ac-cess missions, the initial focus is on missile scale and applications.

The HyTech/HySET program has made signi cant advance-ments over the past 8 years in the following issues associated withliquid hydrocarbon-fueled scramjet engine development: ignitionand ameholding methodologies, endothermic fuels technology,high-temperaturematerials, low-cost manufacturingtechnology forscramjet engines, and detection and cleaning procedure for cokedheat exchangers. The engine development addressed issues associ-ated with weight, cost, and complexity.An effective xed-geometryscramjet engine was developed for operation over the Mach 4–8speed range. HySET was unique in having developed scramjet per-formance and structural durability of complete engine con gura-tions not just owpaths.

Hyper-X. NASA initiated the joint LaRC and Dryden FlightResearch Center hypersonicX-plane (Hyper-X) program in 1996 toadvance hypersonic airbreathing propulsion (scramjet) and relatedtechnologies from the laboratory to the ight environment. Thisis to be accomplished using three small (12-ft long), hydrogen-fueled researchvehicles(X-43) ying at Mach 7 and 10. The Hyper-X program technology focus is on four main objectives requiredfor practical hypersonic ight: Hyper-X (X-43) vehicle design and ight-test risk reduction, ight validationof design methods, designmethods enhancement, and Hyper-X phase 2 and beyond.

Hyper-X Phase 2 and beyond activities32 include program plan-ning, long-term, high-risk research, and re nement of vision vehi-cle designs. Propulsion related development activity in this arenaincludes the evaluation of the pulse detonation engine (PDE) forhypersonicsystems,magnetohydrodynamics(MHD) scramjet stud-ies, and design developments leading to highly variable-geometryscramjets. Powered takeoff and landing and low-speed operation ofa hypersonic shaped vehicle using remotely piloted vehicles willaddress the low-speed PAI issue identi ed in NASP. Finally, thisarena was active in planning/advocating future directions for spaceaccess vehicle and airbreathing propulsion development.19

Third Generation Space Access. During the late 1990’s NASAestablishedlong term goalsfor access-to-space.NASA’s third gener-ation launch systems are to be fully reusable and operational (IOC)by 2025.33 The goals for third generation launch systems are toreduce cost by a factor of 100 and improve safety by a factor of10,000over currentconditions.NASA’s MarshallSpace Flight Cen-ter in Huntsville,AL has the agency lead to developthird generationspace transportationtechnologies.Development of third generationlaunchvehicle technologyfalls under NASA’s Space TransportationProgram. The programs have had names like Spaceliner, AdvancedSpace TransportationProgram (ASTP), and the Hypersonic Invest-ment Area of Next Generation Launch Technology (NGLT). Theseprograms focus development of technologies in two main areas:propulsion and airframes. The program’s major investment is inhypersonic airbreathing propulsion since it offers the greatest po-tential for meeting the third generation launch vehicle goals. Theprogram is maturing the technologiesin three key propulsion areas,scramjets, rocket-based combined cycle and turbine-based combi-nation cycle. Ground and ight propulsion tests are underway orplanned for the propulsion technologies.Airframe technologiesarematured primarily through ground testing. Selection and prioritiza-tion of technology is guided by system analysis for third generation“vision” vehicles. These vehicles are generally two-stage-to-orbit

FRY 35

vehicles, which can be interrogated for safety, reliability and costimpacts of the proposed technologies.

Flight-tests supporting NASA’s Third Generation Space Accessfocuseson incrementaldevelopmentand demonstrationof key tech-nology that can not be demonstrated to a Technology ReadinessLevel (TRL) of 6 in ground tests. These start with scramjet per-formance, operability and airframe integration (X-43A, X-43C andX-43D) for ightMach numbersfrom 5 to 15. These rst demonstra-tors are expendable to reduce test costs. The next step is integrationof low-speed (Mach 0 to 3C) with the scramjet system in a reusable“combined cycle” ight demonstration (RCCFD). The rst step forRCCFD is a Mach 0-7 reusable air-launchedresearch vehicle, sim-ilar in size to the X-15. The nal step would be a larger vehiclecapable of operation to full airbreathing Mach number required forthe 2025 IOC vehicle.

International activity in this period continued to include manydevelopments. A joint French/Russian program Wide Range Ram-jet (WRR) was initiated to develop technology for reusablespace launcher applications. France also began the developmentof Joint Airbreathing Research for Hypersonic Application Re-search (JAPHAR) in cooperation with Germany as follow-on tothe PREPHA (France) and Sänger (Germany) programs to pur-sue hypersonic airbreathing propulsion research for reusable spacelauncher applications. Furthermore France initiated Promethéeaimed at developing fully variable-geometry endothermic hydro-carbon fuel dual-mode ramjet technology for military applications.The French effortsare leadingtoward LEA, a new ight-testdemon-strationof a high-speeddual-mode ramjet propelledvehicle at ightconditions of Mach 4–8 in the 2010–2012 time frame. In this era,Russia began openly discussing their development of AJAX, aninnovativehypersonicvehicle concept envisionedto capture and re-cycle energy otherwise lost in ight at high Mach numbers. Russiaalso initiated second generation hypersonic ying laboratory workwith Gela Phase II and the Mig-31 HFL. Australia conducted, withinternationalsupport, the world’s rst veri ed demonstrationof su-personic combustion in a ight environment under HyShot.

The development of vehicles for space access applications re- ected maturation in propulsion technology and the technical in-terests of the times. Initial concepts, for example, the GermanSänger–Bret Silbervögel of 1938, postulated single-stage-to-orbit(SSTO) vehicles based on pure rocket systems, or rocket-loftedboost-gliders,such as the U.S. Dyna-Soar. The U.S. Air Force sup-ported Spaceplane development followed, which spawned imag-inative upper atmospheric high-Mach air collection and oxygenextraction technologies. The understanding of scramjet technol-ogy had began. By the early 1960s, the maturation of advancedairbreathing technology encouraged a redirection toward complexfully reusable TSTO vehicles with airbreathing rst stages (withcombinations of turbojets, turboramjets, or ramjets/scramjets) androcket-boosted second stages. The economic realities of the 1970sdictated using semi-expendable, pure-rocket approaches, typi edby the space shuttle. The potentialitiesof the advanced airbreathingscramjet of the 1980s led to NASP and horizontal takeoff and land-ing concepts for airbreathingSSTO vehicles using complex propul-sion systems dependent on new high-energy fuel concepts and theair collection and oxygen extraction technologies developed pre-viously. The 1990s witnessed less ambitious goals of developingeither pure advanced rocket systems (X-33 and X-34) or systemsusing straightforward scramjet technology (X-43A Hyper-X). The rst ight demonstrationof scramjet-propelledvehicledesignswithtrue potential for enabling space access promises to become realityin 2003–2004.

These andotherinternationaldevelopmentprogramsarereviewedin furtherdetail lateras a meansof betterunderstandingthe evolutionin scramjet technology.

Evolution in Ramjet and ScramjetDevelopment Programs

The development of ramjet technology for multiple applicationshas proceeded in parallel throughout history. Applications haveranged from boost- to main-propulsionfor aircraft, gun projectiles,

missiles, and space launch vehicles. The intent here is to highlightinternational activity and selected programs as a means of identi-fying sources of technologyadvances, often resulting from parallelefforts in multiple applications.

The key enabling technologies, components, or events that hadsigni cant impacton the maturationof ramjetpropulsionand enginedesigns, summarized in Table 1, are brie y discussedrelevant to theworldwide development of vehicle concepts and systems. The his-tory of the worldwide subsonic and supersonic combustion ramjetevolution is summarized by era in Tables 2–6 from the turn of thecentury to today. Presented in Tables 2–6 for each ramjet/scramjetsystem are known historicalera, originatingcountry,engine/vehiclename, engine cycle type, development dates, design cruise Machnumber, altitude and range performance, system physical charac-teristics, and state of development. The ranges provided are a mixdepending on the engine/vehicle development status: operationalrange for operationalsystems, predicted range for concept vehicles,or demonstrated range for ight-test vehicles. Additionally, thoseengines/vehicles that are discussed and illustrated in this paper areindicated. Many observations can be drawn from the data shown inTables 2–6 and include the following.

1) Ramjet technology development has been consistently pur-sued internationally from very early days, accompanied by steadyincreases in airbreathing system capabilities.

2) Ramjet engineshave receivedsubstantiallymore attentionthanscramjet engines, with scramjet development increasing steadilysince the early 1990s, which re ects the accelerating pace in thesolution of the challenges of high speed ight.

3) Although at the verge of success, ight testing of ramjet-powered engine concepts at hypersonic speeds has yet to be ac-complished. At this writing the U.S. X-43A Hyper-X is planned fora second ight test in January 2004.

Ramjet Development 1918–TodayRamjet Development: 1918–1960

This era saw the birth of ramjet-powered aircraft ight and itsrapid maturing of technology into primarily missile applicationsand its transition from subsonic to supersonic ramjet ight. Table 2summarizes ramjet evolution in the era from 1918 to 1960 and pro-vides originatingcountry, engine/vehicle name, developmentdates,performance, physical characteristics, and state of development.Countries actively engaged in development in this era were France,Germany, the United States, the United Kingdom and Russia.

The Germans ew the rst operational ramjet-powered missilein 1940 in the form of the V-1 buzzbomb (Fig. 8) powered by asubsonic ight speed pulsejet engine launched by a solid propel-lant booster. The V-1 could be considered the rst cruise missile.German engineer,Paul Schmidt, working from a design of the Lorintube, developed and patented (June 1932) a ramjet engine (Arguspulse jet) that was later modi ed and used in the V-1 Flying Bomb.The German V-1 technologywas transferredto other countriesafterWWII.

The rst ramjet-powered airplane was conceived and variantstested by Leduc of France. The rst powered ight of a ramjet-powered aircraft, Leduc-010 (Fig. 9), took place in April 1949

Fig. 8 German V-1 operational WW II missile (1933–1945).

36 FRY

Tabl

e2

Wor

ldw

ide

ram

jete

volu

tion

1918

–196

0

Pow

ered

Tota

lTo

tal

Cru

ise

Cru

ise

rang

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ngth

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eter

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rM

ach

no.

altit

ude,

ftn

mile

Lau

nche

rin

.in

.lb

mde

velo

pmen

t

1918

–194

5F

ranc

eM

elot

rese

arch

ER

J19

18–1

927

0.4

——

——

——

——

——

——

Com

pone

ntte

sts

1930

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5F

ranc

eL

educ

airc

raft

aL

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d-fu

eled

1933

–195

10.

4–2.

110

,000

——

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und

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——

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Flig

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ram

jet(

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hkin

rese

arch

LFR

J19

33–1

936

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2.0

——

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Com

pone

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man

yV

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t19

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312

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800

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1945

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000

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100

——

200,

000

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1936

–193

90.

3—

——

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——

——

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test

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1942

–194

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320

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145

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l13

48

——

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rati

onal

1945

–196

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nite

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ates

Cob

rab

LFR

J19

45–1

946

2.0

20,0

00—

—R

ail

——

624

0F

light

test

sU

nite

dSt

ates

Gor

gon

IVL

FRJ

1945

–195

50.

420

,000

——

——

——

——

——

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htte

sts

Uni

ted

Stat

esK

DM

-1D

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bL

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1945

–194

92

35,0

0060

Rai

l26

430

1,60

0O

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tion

alU

nite

dSt

ates

P-51

/F-8

0/B

-26

LFR

J19

45–1

955

0.4

20,0

00—

—A

ir—

——

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test

sU

nite

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NA

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958

3.25

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1,05

048

120,

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948

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U.S

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LFR

J19

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950

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0025

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958

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1950

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3515

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-7a

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84,0

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6—

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test

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avy

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saL

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1950

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02.

770

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120

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l38

628

7,72

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pera

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SL

FRJ

1950

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7—

——

——

——

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eG

riff

onII

bA

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J19

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961

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——

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test

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tion

/SSG

ML

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1951

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83.

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1955

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1956

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050

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78

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375

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4400

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1957

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722

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l—

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200

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l33

316

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test

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nite

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1957

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12

23,0

0010

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306

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a Sys

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d

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).

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Com

pany

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f M

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tics

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AR

C).

g

Nor

th A

mer

ican

Avi

atio

n de

sign

atio

n (N

AV

AH

O).

FRY 37

Tabl

e3

Wor

ldw

ide

ram

jete

volu

tion

1960

–198

0

Pow

ered

Tota

lTo

tal

Cru

ise

Cru

ise

rang

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ngth

,D

iam

eter

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eigh

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ate

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ount

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ceE

ngin

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ngin

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rM

ach

no.

alti

tude

,ft

nm

ile

Lau

nche

rin

.in

.lb

mde

velo

pmen

t

1960

–197

0Fr

ance

Stat

alet

exb

LF

RJ

1960

–197

03.

8–5

25,0

00—

—R

ail

——

——

——

Flig

htte

sts

U.S

.Arm

yR

edhe

adR

oadr

unne

rbL

FR

J19

60–1

980

2.5

0–60

,000

217

Rai

l29

812

900

Flig

htte

sts

Uni

ted

Kin

gdom

Sea

Dar

taL

FR

J19

60–1

975

3.5

80,0

0035

Rai

l17

315

.61,

200

Ope

rati

onal

Uni

ted

Sta

tes

Hyp

erje

tbL

FR

J19

60–1

966

5C30

,000

——

Air

——

——

——

Flig

htte

sts

Uni

ted

Sta

tes

D-2

1aL

FR

J19

63–1

980

41,

00,0

002,

600

Air

730

60—

—O

pera

tion

alR

ussi

aSA

-4/G

anef

aL

FR

J19

64–

415

,000

30R

ail

346

345,

500

Ope

rati

onal

U.S

.Air

Forc

eL

AS

RM

b

c

h

i j

g

LF

IRR

1964

–196

72.

50–

6,00

050

Air

168

151,

566

Flig

htte

sts

U.S

.Nav

yA

TP

/TA

RS

AM

-ER

AD

R19

65–1

971

3.8

50,0

00–7

0,00

016

0R

ail

348

13.5

6,42

0C

ompo

nent

test

sU

.S.N

avy

AT

P/T

AR

SA

M-M

Rc

AD

R-I

RR

1965

–197

13.

850

,000

–70,

000

80R

ail

200

13.5

1,75

0C

ompo

nent

test

sU

.S.A

irFo

rce

ASA

LM

aL

FIR

R19

65–1

980

2.5–

410

,000

–80,

000

56A

ir16

820

2,41

5F

light

test

sR

ussi

aSA

-6/G

ainf

ula

DR

IRR

1965

–2.

855

,000

15R

ail

244

13.2

1,32

0O

pera

rtio

nal

Fran

ceSE

X42

2aL

FR

J19

65–1

967

230

,000

——

Rai

l39

420

4,19

0F

light

test

sU

.S.N

avy

IRR

-SA

ML

FIR

R19

66–1

970

3.3

80,0

00—

—R

ail

220

14.7

52,

200

Com

pone

ntte

sts

U.S

.Nav

yA

LVR

J-ST

Ma

LF

IRR

1968

–197

93.

00–

40,0

0028

–100

Air

179

151,

480

Flig

htte

sts

1970

–198

0U

.S.N

avy

IRR

-SSM

LF

IRR

1971

–197

42.

550

,000

——

Rai

l20

014

.75

2,00

0F

ree-

jett

ests

Rus

sia

SS-N

-19/

Shi

pwre

cka

LF

RJ

1972

–2

034

0R

ail/s

ub39

433

15,4

30O

pera

tion

alU

.S.N

avy

GO

RJE

bL

FIR

R19

72–1

976

2.6

035

Air

168

1275

0S

emi-

free

-jet

test

sU

.S.N

avy

ASA

Rd

LF

IRR

1972

–198

13.

880

,000

——

VL

S22

016

2,65

0S

emi-

free

-jet

test

sFr

ance

Scor

pion

aL

FR

J19

73–1

974

670

,000

325

Rai

l—

——

——

—C

ompo

nent

test

sU

.S.N

avy

MR

Ee

LF

IRR

1973

–197

73.

030

,000

–70,

000

150

Air

168

151,

500

Fre

e-je

ttes

tsR

ussi

aG

EL

Aph

ase

IaL

FR

J19

73–1

978

30–

55,0

00—

—T

U-9

5—

——

——

—F

light

test

sU

.S.N

avy

IRR

-TT

Vf /T

TM

fL

FIR

R19

74–1

985

3.0

60,0

00—

—Su

bmar

ine

246

213,

930

Com

pone

ntte

sts

U.S

.Air

Forc

eA

SAL

M–P

TV

aL

FIR

R19

76–1

984

2.5–

410

,000

–80,

000

56A

ir16

820

2,41

5F

light

test

sU

.S.A

irFo

rce

LF

RE

DL

FIR

R19

76–1

980

330

,000

——

Air

——

——

——

Com

pone

ntte

sts

U.S

.Nav

yL

IFR

AM

LF

IRR

1976

–198

03:

0C—

—15

0A

ir14

48

650

Sem

i-fr

ee-j

ette

sts

U.S

.Nav

ySO

FR

AM

SFI

RR

1976

–198

13:

0C—

—15

0A

ir14

48

650

Fre

e-je

ttes

tsG

erm

any

EFA

SFD

R19

76–1

980

——

——

——

——

——

——

——

Flig

htte

sts

U.S

.Nav

yFi

rebr

andb

LF

RJ

1977

–198

23

044

Rai

l20

014

1,20

0F

light

test

vehi

cle

U.S

.A

irFo

rce

DR

ED

DR

1977

–197

93

30,0

00—

——

——

——

——

—C

ompo

nent

test

sR

ussi

aSS

-N-2

2/S

unbu

rna

LF

IRR

1977

–2.

50

270

Rai

l36

028

8,80

0O

pera

tion

alR

ussi

aA

S-17

/Kh-

31a

LF

IRR

1977

–3

044

–90

Rai

l20

414

1,32

2O

pera

tion

alFr

ance

Rus

tique

MPS

R-1

bU

FD

R19

78–1

985

340

,000

35R

ail

144

836

0F

light

test

sPe

ople

’sR

epub

lic

C-1

01b

LF

RJ

1978

–1.

80

30R

ail

295

214,

070

Ope

rati

onal

ofC

hina

U.S

.Arm

ySP

AR

KS

FRJ/

IRR

1978

–198

13

0—

—R

ail

——

——

——

Flig

htte

sts

U.S

.Air

Forc

eD

R–P

TV

FFD

R19

79–1

986

3.5

60,0

00—

—A

ir—

——

——

—F

ree-

jett

ests

a Sys

tem

disc

usse

dan

dsh

own.

bS

yste

m

cA

ugm

ente

d th

rust

pro

puls

ion/

thru

st a

ugm

ente

d su

rfac

e-to

-air

mis

sile

-ext

ende

d ra

nge,

and

-m

ediu

m r

ange

(A

TP/

TA

RS

AM

-ER

, -M

R).

d

Adv

ance

d su

rfac

e-to

-air

ram

jet

disc

usse

d.(A

SAR

).

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oder

n ra

mje

t eng

ine

(MR

E).

f

Tor

pedo

tube

veh

icle

/torp

edo

tube

mis

sile

(T

TV

/TT

M).

g

Duc

ted

rock

et e

ngin

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velo

pmen

t (D

RE

D).

h

Liq

uid

fuel

ram

jet e

ngin

e de

velo

pmen

t (L

ER

ED

).

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uid

fuel

ram

jet

mis

sile

(L

IFR

AM

).

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lid f

uel r

amje

t mis

sile

(SO

FRA

M).

38 FRY

Tabl

e4

Wor

ldw

ide

ram

jete

volu

tion

1980

–tod

ay

Cru

ise

Pow

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lTo

tal

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ise

alti

tude

,ra

nge,

leng

th,

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met

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wei

ght,

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teof

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ntry

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vice

Eng

ine/

vehi

cle

Eng

ine

type

Dat

es,y

ear

Mac

hno

.ft

nm

ileL

aunc

her

in.

in.

lbm

deve

lopm

ent

1980

–199

0Fr

ance

/Ger

man

yA

NSc

LF

IRR

1980

–199

22.

50

44R

ail

204

141,

322

Flig

htte

sts

Fran

ceA

SMPa

LF

IRR

1980

–3

018

5A

ir21

015

1,84

8O

pera

tion

alU

.S.N

avy

AC

IMD

/AA

AM

aL

FIR

R19

81–1

989

3.2

80,0

0015

0A

ir14

49.

559

0C

ompo

nent

test

sU

.S.A

irFo

rce

BSF

RJd

Tec

hS

FRJ

1982

–198

73

70,0

0030

0A

ir—

——

——

—C

ompo

nent

test

sU

.S.N

avy

Van

dal(

Talo

s)a

LF

RJ

1983

–2.

20

43.5

Rai

l43

428

8,21

0O

pera

tion

alU

.S.N

avy

SFIR

RS

FIR

R19

84–1

989

2.5

050

Air

168

18—

—C

ompo

nent

test

sU

.S.N

avy

SLA

Ta

LF

IRR

1986

–199

22.

50

50R

ail

218

212,

445

Flig

htte

sts

U.S

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Forc

eB

EC

ITE

eS

FIR

R19

87–1

990

370

,000

300

Air

——

——

——

Com

pone

ntte

sts

U.S

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Forc

eV

FDR

aD

R19

87–1

997

350

,000

50A

ir14

47

360

Com

pone

ntte

sts

U.S

./Ger

man

yC

oope

rativ

ete

chni

calp

rogr

amS

FDR

1989

–199

93

50,0

0050

Air

144

736

0C

ompo

nent

test

s19

90–2

000

Fran

ceA

SLP

D2

LF

IRR

1990

–199

62–

3.5

——

——

Air

——

16—

—C

ompo

nent

test

sFr

ance

MA

RS

bL

FIR

R19

90–1

996

4–5

90,0

00—

—A

ir22

015

——

Com

pone

ntte

sts

Indi

aA

KA

SHb

DR

IRR

1990

–3.

550

,000

15R

ail

256

131,

445

Flig

htte

sts

Uni

ted

Sta

tes/

Fran

ceC

oope

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chni

calp

rogr

amU

CD

R19

91–1

997

350

,000

50A

ir14

47

360

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pone

ntte

sts

Peop

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Rep

ubli

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naC

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bL

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J19

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388

3010

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rati

onal

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ted

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nC

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chni

calp

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amV

FD

R19

92–1

997

350

,000

50A

ir14

47

360

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pone

ntte

sts

Fran

ceR

usti

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MPS

R-2

bU

FD

R19

93–1

997

3.5

80,0

0030

Rai

l15

87.

944

0F

light

test

sR

ussi

aM

A-3

1/A

S-17

bL

FIR

R19

94–

4.5

044

–90

Rai

l20

014

1,40

0F

light

test

sSo

uth

Afr

ica

LR

AA

Mb

LF

IRR

1994

–4

80,0

0045

Air

144

736

0F

light

test

sU

.S.N

avy

LD

RJ/

LC

MS

bL

FIR

R19

95–1

999

4.0

7,00

070

0A

ir25

621

3,40

0F

light

test

sFr

ance

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man

yA

NF/

AN

NG

bL

FIR

R19

95–2

000

345

,000

18A

ir20

014

1,44

0C

ompo

nent

test

sR

ussi

aA

A-X

-12a

DR

1995

–3.

570

,000

65A

ir14

28

390

Flig

htte

sts

Isra

ilG

abri

elIV

bL

FIR

R19

95–

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ail

190

17.6

2,10

0C

ompo

nent

test

sPe

ople

’sR

epub

lic

ofC

hina

Hsi

ung

Feng

IIIb

LF

IRR

1995

–2.

50

320

Rai

l19

017

.62,

100

Com

pone

ntte

sts

Uni

ted

Kin

gdom

FMR

AA

Mb

VF

DR

1995

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93

70,0

0010

0A

ir14

47

400

Dev

elop

men

tFr

ance

Ves

tab

LF

IRR

1996

–200

34

018

6A

ir20

014

1,84

8F

light

test

sFr

ance

Ras

calb

LF

IRR

1996

–2–

40–

65,0

00—

——

——

—8–

14—

—C

ompo

nent

test

sFr

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bL

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R19

98–

40

270

Air

200

141,

848

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rati

onal

Ger

man

yA

RM

IGE

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DR

IRR

1996

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6–17

38

500

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pone

ntte

sts

Rus

sia

SS-N

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R19

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,000

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350

27.5

5,50

0F

light

test

sIn

dia/

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sia

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rahm

osb

LF

IRR

1998

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80–

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0016

2R

ail

354

288,

000

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rati

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ted

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gdom

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RA

AM

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1999

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0054

Air

144

740

0C

ompo

nent

test

sU

.S.N

avy

SFR

JTe

chP

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FRJ

1999

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80,0

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l/V

LS

168–

256

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2000

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l14

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540

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nent

test

sPe

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lic

ofC

hina

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g-Ji

12b

LF

IRR

2000

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20,0

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200

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nent

test

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aV

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S16

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2002

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580

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——

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in.

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deve

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1955

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erna

lbur

nbE

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1957

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——

——

——

——

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sia

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tink

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chE

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1957

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——

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1973

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nent

test

s19

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U.S

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yW

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1977

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——

——

——

——

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1986

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Fig. 9 France’s rst ramjet-propelled ight tested airplane (1933–1951).

Fig. 10 German Sänger I Hypersonic Concept Vehicle (1936–1945).34

as an air-launched vehicle from another aircraft. Re ned versionsof this aircraft followed over the years with the subsequentdevelop-ment of the Grif n II. Throughout this chronology, the dates in the gure captions are intended to re ect a total time interval includingdevelopment, tes