Radar Characterization of Hypersonic Wake Plasma in a High-Enthalpy Shock-Tunnel Flow: RCS, Micro-Doppler and Electron-Density Analysis

Abstract

The plasma sheath that forms around vehicles at hypersonic speed can change the radar signature substantially. A common approach to predict the impact of plasma on radar observation is to combine computational fluid dynamics (CFD) and computational electromagnetics (CEM). Due to the lack of experimental reference data, however, these predictions often remain unvalidated and their accuracy unclear. As part of an initiative to improve this situation, this paper presents radar signatures of a turbulent flow around an 8 cm diameter sphere measured at high enthalpy conditions in the High Enthalpy Shock Tunnel Göttingen (HEG) at the site of the German Aerospace Center (DLR) in Göttingen. The radar return and microwave transmission of this instationary and turbulent hypersonic flow were acquired with the wideband Multi-application Software Defined Radar (Masodera) system. Besides a strong radio blackout on the transmission channel, characteristic Micro-Doppler features were also observed. Reference CFD and CEM simulations were carried out and are compared with the measured data.