Air-breathing hypersonic cruise: Prospects for Mach 4-7 waverider aircraft

Abstract

There is currently a renewal of world-wide interest in hypersonic flight. Vehicle concepts being considered range from cruise missiles to SSTO and TSTO vehicles. The new characteristics of these vehicles are that they will be powered by airbreathing engines and have long residence times in the air-breathing corridor. In the Mach 4-7 regime, waverider aircraft are being considered as candidates for both long-range and short-range cruise missions, as hypersonic missiles, and as high LID highly maneuverable vehicles. This paper will discuss the potential for near-term and far-term application of air-breathing engines to the above waverider vehicle concepts and missions. In particular, the cruise mission is discussed in detail and attempts are made to compare and contrast it with the accelerator mission. Past criticisms levied against waveriders alleged low volumetric efficiency, lack of engine/airframe integration studies, poor offdesign performance, poor take-off and landing capability, have been shown by on-going research to be unfounded. A discussion is presented of some of the technical challenges and on-going research aimed at realizing such vehicles: from turboramjet and scramjet technology development, propulsionairframe integration effects on vehicle performance, aeroservothermoelastic systems analysis, hypersonic stability and control with aeroservothermoelastic and propulsion effects, etc. A unique and very strong aspect of hypersonic vehicle design is the integration and interaction of the propulsion system, aerodynamics, aerodynamic heating, stability and control, and materials and structures. This first - order multidisciplinary situation demands the ability to integrate highlycoupled and interacting elements in a fundamental and optimal fashion to achieve the desired performance. Some crucial technology needs are found in propulsion-airframe integration and its role in configuration definition, hypersonic boundarylayer transition and its impact on vehicle grossweight and mission success, scramjet combustor mixing length and its impact on engine weight and, CFD (turbulence modeling, transition modeling, etc) as a principal tool for the design of hypersonic vehicles. Key technology implications in thermal management, structures, materials, and flight control systems will also be briefly discussed. It is concluded that most of the technology requirements in the Mach 4-7 regime are relatively conventional making cited applications near-term, yet offering very significant advancements in aircraft technology.