For hypersonic transport vehicles with combined turbo-ramjet engines operating in the Mach 0 to 6+ regime the exhaust nozzle/aftbody configuration is one of the most important areas. The variable and controllable hot gas single expansion ramp nozzles coupled with different bypass and boundary layer flows represent highly integrated propulsion/airframe-systems. These exhaust systems influence considerably the vectorial force and moment balance of the total aircraft. This paper presents examples of some concept studies of generic nozzle configurations calculated by different computational fluid dynamic methods for selected flight regimes. The following aspects are mainly discussed: Bookkeeping system of the single expansion ramp nozzle and aircraft aftbody, the application of different CFD-codes, a critical comparison of typical examples and calculation methods and finally some considerations about future investigations and experimental correlation.

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Engine/aircraft integration is a major factor for performance characteristics of hypersonic propulsion. A two-dimensional analysis of an airbreathing combined turbofan-ramjet propulsion system is presented with special emphasis on integration aspects of mixed compression air inlets and single expansion ramp nozzles. Based on performance analysis a real-time engine simulation program, integrated into a flight simulator, is presented. In a realistic flight-mechanical analysis of hypersonic aircraft, steady state and dynamic propulsion system performance have to be considered, with thrust and lift components and resulting pitching moments. Active thrust vector control has to be performed using variable inlet and nozzle geometry. At high flight Mach numbers the net thrust vector is very sensitive to inlet ramp deflection angles and angle of attack. The net thrust vector can easily be turned to more than 90°. Various propulsion system failure scenarios are presented.

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