Fast-response measurements of shock layer radiation in the High Enthalpy Shock Tunnel Göttingen (HEG)

The development of reentry aerodynamic configurations requires examination of surface heat flux. Reentry-relevant freestream conditions are suitably generated by shock tunnels such as the High Enthalpy Shock Tunnel Göttingen (HEG). Surface heating due to radiation at high-enthalpy stagnation conditions has been shown to comprise a significant portion of the total measured surface heat flux on reentry configurations. Earlier studies of surface heat flux at or near the stagnation region on blunt sphere-cones and capsules indicated substantial underprediction of surface heating by numerical calculations compared with what was measured in experiments. The conclusion of recent tests in the HIEST at JAXA was that this extra heating component measured in shock tunnel experiments was due to radiation within the shock layer. Previous observations made at the HEG of stagnation point flows have demonstrated fluctuations within the radiating shock layer. The objective of the current experiments is to probe the shock layer and thereby investigate the fluctuations of radiation heat flux within the shock layer. This will be combined with synchronised imaging of the shock front to correlate fluctuations of the shock front geometry with fluctuations in measured heat flux due to shock layer radiation