E AMEICA SOCIEY O MECAICA EGIEES 2G4 4 E. 4 St., Yr, .Y. 00 e Sociey sa o e esosie o saemes o oiios aace i aes o i Ms. cussio a meeigs o e Sociey o o is iisios o Secios, o ie i is uicaios. iscussio is ie oy I e ae is uise i a ASME oua. aes ae aaiae om ASME o iee mos ae e meeig. ie i USA. Copyright © 1992 by ASME Arrthn prn Cr: rpt fr Mh 4 Wvrdr Arrft Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1992/78941/V002T02A040/2401661/v002t02a040-92-gt-437.pdf by guest on 27 September 2021 ISAIA M. AKSO yesoics eseac iisio aioa Aeoauics a Sace Amiisaio Wasigo, C ABSTRACT situation demands the ability to integrate highly- There is currently a renewal of world-wide interest coupled and interacting elements in a fundamental in hypersonic flight. Vehicle concepts being and optimal fashion to achieve the desired considered range from cruise missiles to SSTO and performance. Some crucial technology needs are TSTO vehicles. The new characteristics of these found in propulsion-airframe integration and its role vehicles are that they will be powered by air- in configuration definition, hypersonic boundary- breathing engines and have long residence times in layer transition and its impact on vehicle gross- the air-breathing corridor. In the Mach 4-7 regime, weight and mission success, scramjet combustor waverider aircraft are being considered as mixing length and its impact on engine weight and, candidates for both long-range and short-range CFD (turbulence modeling, transition modeling, etc) cruise missions, as hypersonic missiles, and as high as a principal tool for the design of hypersonic LID highly maneuverable vehicles. This paper will vehicles. Key technology implications in thermal discuss the potential for near-term and far-term management, structures, materials, and flight control application of air-breathing engines to the above systems will also be briefly discussed. It is concluded waverider vehicle concepts and missions. In that most of the technology requirements in the Mach particular, the cruise mission is discussed in detail 4-7 regime are relatively conventional making cited and attempts are made to compare and contrast it applications near-term, yet offering very significant with the accelerator mission. Past criticisms levied advancements in aircraft technology. against waveriders alleged low volumetric efficiency, lack of engine/airframe integration studies, poor off- I. INTRODUCTION design performance, poor take-off and landing capability, have been shown by on-going research to Following nearly 15 years of relative inactivity, sev- be unfounded. A discussion is presented of some of eral countries have initiated research and technology the technical challenges and on-going research aimed programs to develop various types of at realizing such vehicles: from turboramjet and aero/spacecraft. Their ultimate goal is direct, scramjet technology development, propulsion- reliable and easy access to space (Ref 1). In Europe, airframe integration effects on vehicle performance, Russia, Japan, India, etc., hypersonic programs are aeroservothermoelastic systems analysis, hypersonic directed toward vehicles such as Hermes, Sanger, stability and control with aeroservothermoelastic and Hotol, Hope, Hyperplane, etc. Concepts for propulsion effects, etc. A unique and very strong hypersonic vehicles powered by air-breathing aspect of hypersonic vehicle design is the integration engines are also evolving as part of these programs. and interaction of the propulsion system, In the U.S., the National Aerospace Plane (NASP) aerodynamics, aerodynamic heating, stability and program is developing the key technologies required control, and materials and structures. This first - for the successful operation of air-breathing order multidisciplinary hypersonic aerospace vehicles. The general goal of esee a e Ieaioa Gas uie a Aeoegie Cogess a Eosiio Cooge, Gemay ue 4, 2 is ae as ee accee o uicaio i e asacios o e ASME iscussio o i wi e accee a ASME eaquaes ui Seeme 0, 2 the NASP program is the construction and testing of stands at Mach 5.2, held by a ramjet-powered Martin an experimental, fully-reusable vehicle, designated Marietta ASALM missile that disobeyed a fuel shut- the X-30, that will be used as a manned demonstrator down signal. The cruise application, specifically for for hypersonic flight. The vehicle will use Mach 4-7, is the focused topic of this paper. The hydrogen-fueled, air-breathing ramjet/scramjet purpose in addressing this application separately is engines and will be capable of horizontal takeoff and that there are technologies which are specific to landing. It will be designed to expand the envelope Mach 4-7 cruise. There are also technologies which of high speed flight in and beyond the atmosphere to are common to cruise and other hypersonic missions. the point that access to low earth orbit can be These are discussed in this paper. The paper offers an in-depth investigation of the most pertinent achieved. The uniqueness of NASP lies in its highly- Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1992/78941/V002T02A040/2401661/v002t02a040-92-gt-437.pdf by guest on 27 September 2021 integrated scramjet, special structures and materials technology issues associated with hypersonic cruise requirements, absence of suborbital stages, and and also addresses issues associated with one class of inherent payload return capability. NASP addresses vehicles which is fundamentally suited for hypersonic SSTO (single-stage-to-orbit) as well as aspects of cruise waveriders. A summary of the status of several accelerator/interceptor applications, but does waverider technology for air-breathing missions is not adequately address the technology aspects unique provided so that the extremely important to cruise applications. For either class of vehicle, technologies that must be developed for the benefit of however, a tradeoff between engine thrust-to-weight the entire hypersonic vehicle development ratio and specific fuel consumption is necessary. community are stressed with a perspective of applicability to real missions. Also, some of the In this paper, the prospects for air-breathing hyper- technologies for waveriders are actually specific to sonic vehicles, especially hydrocarbon-fueled Mach waveriders, and must be addressed in the context of a 4-7 vrdr aircraft, are examined. Prospects for waverider discussion. Because air-breathing generic air-breathing hypersonic vehicles (Mach 5- hypersonic vehicles are multidisciplinary systems, 25) were previously discussed in Refs 2 and 3. brief discussions about the technical areas which Figure 1 shows flight block time as a function of impact the design of such vehicles are presented. global range fraction for several cruise Mach numbers. The shaded regions indicate the global Mach 4-7 is an attractive segment of hypersonics as range fractions and Mach numbers believed to be of it offers a combination of very high speed capability primary interest for future high-speed civil transport and use of relatively conventional technologies. This aircraft and military.reconnaissance/strike aircraft. range of speeds offer dramatic reductions in travel Cruise Mach numbers of 2 to 3 for civil aircraft, time compared to subsonic or even supersonic speeds which are consistent with Concorde and current as shown in Fig. 1. This range of speeds may also be operational military aircraft, would reduce the block very competitive (depending on mission) with higher time for trans-pacific flights from about 14 hours to speeds of Mach 8 to 12 over distances up to 12,000 about 4-6 hours. Mach 5-6 military aircraft could nmi (or half the way around the earth). Such speed provide worldwide coverage in about 4 hours. Mach capability has a number of useful applications numbers greater than about 10-15 provide an including first stage of a two-stage-to-orbit vehicle, insignificant improvement in block time for both interceptor, recce, and transports. civil and military aircraft. Much greater distances Though the need for high speed travel has remained are required for these higher speeds to pay off in roughly constant constant over time (perhaps block time. The Earth simply isn't big enough to increasing with the advent of integrated global socio- warrant aircraft that cruise faster than about Mach economic ties), the availability or maturity of 10-15. technologies for the Mach 4 to 7 range has been As already noted, most national and international progressing. In the past few years several key hypersonic activities are focused on transatmospheric enabling technologies have matured to significant flight with the goal of constructing air-breathing levels. These technologies include high temperature single-stage-to-orbit second generation shuttles or hydrocarbon fuels, high temparature materials, two-stage transports that incorporate an air-breathing practical combined cycle engines (e.g. turboramjets first stage. An obvious intermediate regime, and and scramjets), and highly efficient perhaps spin-off technology from the above concepts, vehicle/aerodynamic shapes. is the development of extremely high-speed civilian One element of the latter, which is a key driver in and military vehicles designed for sustained flight in the overall concept of a Mach 4 to 7 vehicle is the the range of Mach 4-25. At the high end of this advent of modern efficient waverider concepts. anticipated air-breathing flight corridor, sustained These concepts have the potential of excellent levels orbital flight at Mach 25 is now routine. At the low of performance in at least three key areas of I, end, the speed record for air-breathing vehicles 2 volumetric efficiency, and stability and control. a sound interpretation of the Breguet range equation. Though the shape of candidate Mach 4 to 7 This classification of aircraft shapes is shown in Fig waverider vehicle concepts are relatively simple, 2 (Ref. 5). The progression of optimum "cruising" they are nonetheless the result of extensive analytical engines as a function of flight speed is also shown.