HIFiRE-1 Surface Pressure Fluctuations from High Reynolds, High Angle Ground Test

Abstract

The HIFiRE-1 is a 7-degree half-angle circular cone with a 2.5-mm nose radius. A successful HIFiRE-1 flight experiment was carried out in March 2010. Due to an anomaly in the exoatmospheric pointing maneuver, the reentry angle of attack was higher than anticipated (5–15 degrees instead of �0). A test campaign in the H2K hypersonic wind tunnel at DLR Cologne was mounted to gather high-frequency pressure fluctuation data and global heat flux via infrared thermography at the high angles of attack and Reynolds numbers encountered in the as-flown trajectory. This paper describes the analysis and interpretation of the surface pressure fluctuations; thermographic analysis is contained in a companion paper. Pressure-fluctuation power spectra were computed at azimuths from the windward to leeward rays in 45° increments at ten sensor locations along the ray, and the expected laminar, transitional, and turbulent regimes were encountered. The disturbances along the windward and leeward rays are presumed to arise from amplified second-mode waves. At 6° angle of attack, 250-kHz disturbances were detected along the 135°-from-windward ray; it is unclear whether these fluctuations arise from second-mode or crossflow instabilities. At 9° angle of attack, similar pressure fluctuations occur along the 135° ray prior to separation near the leeward ray.