Hypervelocity impact fragment clouds in high pressure gas numerical and experimental investigations

Abstract

Space debris poses a threat to vehicles in near earth orbits. Due to the potential risk of catastrophic bursting under hypervelocity particle impact, pressurized vessels have been identified as high risk components. During recent experimental studies the principle failure mechanisms were investigated that lead to qualitative descriptions of the phenomenology. First experimental results from different studies showed that a strong interaction between cloud fragments and pressure gas occurred. In some cases the fragments were completely ablated inside the vessel. The aim of this study was the numerical simulation of the complex interaction between fragments and gas. The numerical work was performed in parallel to experiments, where hypersonic fragment clouds in pressure gas were photographed. The pictures obtained in the experiments showed black regions behind the leading edge of the cloud which are assumed to be filled with ablation products. A distinct blast wave formation behind the fragments was observed in the surrounding gas. Also, particularly at high pressures, a size dependent deceleration of the fragments leads to the formation of a jet-like spike along the impact axis. SPH hydrocode methods turned out to be an adequate tool for the simulation of the complex interaction mechanisms. Particularly the high density gradients and the fragment-gas interaction requires a flexible and robust simulation method. Despite some specific problems gridless methods proofed to be a promising discretization tool for the simulation of the mentioned experiments. A beta SPH version of AUTODYN-2D was used to simulate hypervelocity impact on a vessel pressurized to 10.5 bar. As a result a good correlation between experimental and numerical results was obtained. Features like the blast wave propagation and the formation of the jet-like spike at the tip of the fragment cloud compared well to the experimental results.