Hypersonic Retrograde Propulsion Experiments - A Basis for Validation of CFD within RETPRO

Abstract

The paper focuses on wind tunnel tests of the hypersonic re-entry part of the RETPRO descent trajectory. The re-usable rocket launcher configuration is investigated including active retro-propulsion at Mach 5.3 and 7.0 in the Hypersonic Wind Tunnel (H2K) of DLR, Cologne. Results from high-speed Schlieren imaging, force and unsteady wall pressure measurements are output for CFD accuracy assessment and validation. Variations of the number of active engines, thrust coefficient, jet temperature and angle of attack are performed to gather detailed information on sensitivities of characteristic mean and dynamic flow features. It is shown that the dynamic behavior of the retro-propulsion flow field is significantly altered by the engine configuration. A stable quasi-steady mode with overlaying shock oscillation is found for the one engine case, while three engine operation leads to a turbulent flow field with random flipping between a short and a long jet penetration mode. The oscillation frequency and temporal characteristics of the retro-propulsion flow field are found to be sensitive to the thrust coefficient and jet reservoir temperature.