Free Flight Testing in Hypersonic Flows: HEXAFLY-INT EFTV

Abstract

This study reports the application of free flight testing in a hypersonic wind tunnel for the aerodynamic characterization of a hypersonic vehicle. Sub-scale models of ESA’s HEXAFLY-INT EFTV geometry were released into hypersonic flow and motion was measured through a combination of high-speed video analysis and on-board gyroscopes and accelerometers. These measurements allow aerodynamic coefficients to be determined and give insight into the stability of the design. Models were fabricated using both 3D printing and CNC milling techniques. A light-weight instrumentation system was assembled to measure angular movements (pitch, roll and yaw) and accelerations and transmit the sensor data via a Bluetooth transceiver to an off-board computer for post processing. The University of Southern Queensland’s short-duration hypersonic wind tunnel (TUSQ) was used for testing. It produces a quasi-steady test flow of approximately 200 ms at nominally Mach 6. Results are presented from two separate test campaigns. The first is a comprehensive repeatability study of the free flight technique and the second is the preliminary results of testing a new model design with interchangeable flap angles. The repeatability study showed that the free flight technique is inherently repeatable, despite large variations in model movement between experiments. As expected, lift coefficient showed less scatter than pitching moment coefficient, due to accelerations being measured directly as opposed to angular accelerations which required differentiation of the gyroscope data. Preliminary data from the new hybrid metallic-plastic models showed static stability in all cases. The models themselves proved to be robust, surviving all experiments with minimal damage.