Abstract A novel dynamic stability test device based on the free-oscillation measurement technique has been developed for wind-tunnel applications covering flow regimes from subsonic to hypersonic conditions. The device offers high versatility through interchangeable cross-springs, enabling free-oscillation tests in pitch, yaw, and roll, and accommodating models with a wide range of moments of inertia and aerodynamic stiffness characteristics. It is suitable for both capsule-type and lifting-body space vehicle configurations. The first application of the device was a dynamic pitch stability test of the ReFEx (Reusable Flight Experiment) model, representing a lifting-body space vehicle, where dynamic stability along the designed trajectory was demonstrated. Oscillation data were evaluated using both cross-spring sensor signals and Schlieren image analysis, showing excellent agreement and thereby validating the applied signal-processing approach. A second application involved dynamic pitch stability testing of an inflatable heat shield model within the EFESTO-2 Horizon Europe project. Measurements were conducted using two cross-springs with different stiffness values, resulting in tests at different reduced frequencies. Additional Reynolds number variations were performed, allowing the influence of reduced frequency and Reynolds number on the extracted dynamic stability derivatives to be systematically assessed.
Zhai et al. (Thu,) studied this question.