Forebody precompression effects and inlet entry conditions for hypersonic vehicles

The efficiently provide precompressed air to the engine inlets, a hypersonic forebody requires a design with potentially contradictory optimization goals: a high static pressure for the inlet entry flow and a large air mass flow to reduce engine size and hence vehicle drag, the maximization of the total kinetic energy for the inlet air, an a small Mach number and flow distortion across the inlet face to guarantee the undisturbed operation of inlets and engines. Starting with basic elliptic, fiat, and concave cross sections of the forebody's bottom side, 11 sharp-nosed, hypersonic-flight-test-vehicle-type forebodies of varying cross-sectional shapes were designed for a numerical investigation of their influence on propulsion and aerodynamic performance, Three dimensional Euler calculations were carried out flight Mach numbers 3.5 and 6.8 at angles of attack of 0 and 6 deg. Slim narrow forebodies provide the highest air mass low rates for the engines and result in the lowest total pressure losses for the inlet entry area. Their external aerodynamic behavior is characterized by low drag and large lift components. Elliptical and concave cross-sectional shapes of the forebody's bottom side are preferable to flat geometries.