On the validation of experimental results for the dynamic stability of re-entry capsules

The following document presents a trustworthy method for validating dynamic stability results obtained from wind-tunnel test campaigns. The first phase comprises the calibration of the electromagnetic test setup, in order to obtain a relation between the supplied current and the generated magnetic damping. In the validation phase this setup is attached to the dynamic stability forced oscillations test structure, outside of the wind tunnel. Several runs are performed with different oscillating speeds and a wide range of known values of magnetic damping for configurations with and without a spring element resembling the aerodynamic stiffness experienced by the model in the wind-tunnel. The Energy Method is then used to process the momentum and angular position recorded during the test and compute the damping acting on the system. The magnetically applied damping and the computed damping are then compared, in order to access the magnitude of the error. For the system without spring applied, results show that low values of error and uncertainty are obtained for most part of the considered curve. The magnitude of the error usually diminishes for an increase in the oscillating speed, but increases for lower values of damping.