Predicting high‐speed particle impact damage in spacecraft thermal protection systems

Abstract

All spacecraft use some sort of thermal insulation, or thermal protection system (TPS), in their design. TPS materials vary, ranging from ceramic tiles or phenolic ablators for heatshields to lightweight multi-layer insulation (MLI) blankets. Since TPS is usually placed on the spacecraft's exterior, it is susceptible to impacts by meteoroids and orbital debris. These high-speed impacts can damage the TPS to a point where the protection it offers is below acceptable limits. As such, it is important to be able to characterize expected TPS damage levels stemming from such high-speed impacts. In this paper, we present the results of a study that sought to characterize the high-speed impact damage that would be sustained by two TPS materials that have recently gained attention for possible use in future interplanetary missions. Empirical equations were developed for TPS crater depths, as well as maximum and minimum crater mouth dimensions. In the event of TPS perforations, empirical equations were developed for the maximum and minimum through-hole dimensions. As part of the analyses performed, ballistic limit equations (BLEs) for these TPS configurations were also developed where possible. The validity of the equations developed was assessed by comparing their predictions against test data. In nearly all cases, the empirical equations developed herein were seen to adequately capture the magnitudes of the measured damage parameters.