Experimental determination of aerodynamic coefficients of simple-shaped bodies free-flying in hypersonic flow

Abstract

The aerodynamic drag, lift and pitching moment of basic geometric bodies in hypersonic flows has been measured. Therefore, simple geometries like spheres, cubes and cylinders were studied at a Mach number of 7.0. Furthermore, the influence of the flight attitude on aerodynamic coefficients and the static stability behaviour of these objects have been investigated. This should enhance the understanding of atmospheric re-entry of rotating objects as well as the improvement of available codes to predict re-entry trajectories of satellites, meteoroids and space stations. Experiments were carried out in the Hypersonic Wind Tunnel (H2K) at the German Aerospace Center (DLR) in Cologne using a free-flight technique. This technique allows a continuously rotation and avoids the influence of stings or balances to determine the forces and moments onto an object. The model motion is tracked by a nonintrusive stereo tracking system with two high-speed cameras. Markers are utilized on the model surface to apply a digital image correlation algorithm. Thus, the three-dimensional trajectories and attitudes of the free-flying objects are reconstructed. After a careful post-processing of the high-resolution motion data, the aerodynamic coefficients are determined. Furthermore, the unsteady flow structures are visualized with high-speed schlieren photography. As a result, the aerodynamic coefficients of cubic and cylindrical bodies are a function of the pitch angle.