Experimental and Numerical Study of Launcher Configurations with Retro-Propulsion in the Hypersonic Wind Tunnel Cologne H2K

Abstract

Retro-propulsion, a deceleration technique where the thrust is pointed towards the direction of flight, is the driving technology for vertically landing, reusable launchers. Experiments, which are indispensable for the full comprehension of this technology, are accompanied by serious challenges. The key factors to facilitate meaningful results of supersonic and hypersonic retropropulsion experiments are addressed in this study. Similarity parameters for sub-scale experiments are evaluated, the interaction of retro-propulsion flows with the test facility is investigated, and condensation within these flows is analyzed. For this purpose, Computational Fluid Dynamics simulations were performed; subsequently, cold gas experiments for a generic retro-propulsion launcher configuration with a single, central nozzle were carried out in the Hypersonic Wind Tunnel Cologne H2K at the German Aerospace Center. Based on this data, an improved similarity parameter related to the exit condition of the engine exhaust flow is proposed and a universally applicable scaling law for supersonic retro-propulsion wind tunnel models is derived. Various condensation mitigation techniques for the conducted experiments are presented and their varying effectiveness is highlighted. Ultimately, improvements for future wind tunnel models and experimental setups are suggested. Thus, this study sets the groundwork for prospective experiments of retro-propulsion configurations in the H2K.