Design Studies for the Development of a Dual Mode Ramjet Flight Test Vehicle

Kurzfassung

With view to potential future space launchers or other hypersonic vehicles the demonstration of high speed airbreathing propulsion, and especially of the dual mode ramjet combining subsonic and supersonic combustion, is still of great interest. After the national hypersonic researcj and technology programs in Germany and France (German Hypersonics Technology Program and French Research and Technology Program for Advanced Hypersonic Propulsion - PREPHA), the mastery of high-speed airbreathing propulsion technologies is not sufficient to allow the development of an operational vehicle. Therefore, ONERA and DLR decided to join in a common research program that investigates an airbreathing propulsion system operating from Mach 4 to Mach 8. The general goal of this project, named JAPHAR (Joint Airbreathing Propulsion for Hypersonic Application Research), is to demonstrate the feasibility of the dual mode ramjet and to develop a methodology for onground and in-flight performance demonstration. Concurrently with engine studies, the project includes conceptional design studies to define an experimental vehicle for dual mode ramjet testing between Mach 4 and Mach 8 and to find a methodology to evaluate its in-flight performances. Furthermore, this vehicle is the baseline configuration for the different component studies within the project and it is used for the global synthesis of the obtained results. In order to be able to obtain results at different Mach numbers between Mach 4 and 8, the vehicle is boosted up to Ma*=8 and then performs a few combustion periods on a decelerating trajectory. In order to be representative for a full scale scramjet operation, the engine height was chosen equal to 100 mm. This results in a global vehicle length of I = 11m and a weight of about 2 tons. During the first design cycle ONERA provided a first definition of the vehicle engine. Using this engine ONERA studied a preliminary vehicle based on the wing-body concept and DLR additionally defined a waverider configuration (Fig. 1). Trajectories were defined and in order to choose the best solution for the project continuation both configurations were compared in detail. During the definition of the associated propulsion datasets the considered forebodies were analyzed based on Navier-Stokes calculations with perfect gas and equilibrium gas assumption. The study covered the complete Mach number range of the trajectory and the expected range of angle of attack. Special attention was paid to the flowfield at the entrance of the air intake (Fig. 2). The comparison of both vehicles included aerodynamic performances, weight estimations, vehicle global design and trim calculations with full bookkeeping along the chosen trajectory. The results show, that a combination of the two considered concepts will allow the combination of the excellent characteristics of a waverider forebody with the good volumetric efficiency and the small trim losses of a wing-body-combination (Fig. 3) The proposed paper will contain an introduction of the project JAPHAR and a detailed discussion of the design studies investigated until now.