Forebody precompression performance of hypersonic flight test vehicles

Abstract

The forebody's geometry greatly influences the overall performance of a hypersonic vehicle. In order to achieve high propulsion efficiency, the forebody must provide precompressed air to the engine's inlets. Demands from the propulsion system include a high static pressure of the precompressed air at the inlet face, a large inlet air mass flow, minimized total pressure losses, and a small Mach number at the inlet face. The undisturbed operation of inlets and engines requires small gradients of all flow parameters and a tolerable distortion across the inlet face. Concerning the external aerodynamic performance of the forebody's shape, high lift, low drag, and stability requirements broaden the complexity of the design task for hypersonic forebodies. The aerodynamic performance of different forebody modifications for two hypersonic flight test vehicles (HYTEX R-A3, RADUGA Drone D2), which were studied within the German Hypersonics Technology Program, was numerically investigated. The results of three-dimensional Euler calculations comprise precompression data sets for a flight Mach number range between 3.5 and 6.8 at angles of attack between 0 deg and 9 deg. To describe the inlet entry conditions, which decisively affect inlet design, static and total pressure ratios for the captured stream tubes, inlet entry Mach numbers, and stream tube area ratios (inlet air mass flows) were calculated. This evaluation enables the consideration of the aerodynamic interaction between the forebody and the inlets in order to optimize the performance of the complete propulsion system. Lines of constant Mach numbers, pressure ratios, local angles of attack, and local angles of yaw allow conclusions on the flow quality and the distortion within the area of the inlet face and contribute to the understanding of the threedimensional flowfields around the forebody geometries.