The effect of atomic oxygen flux and impact energy on the damage of spacecraft metals

Abstract

High-energy atomic impacts represent one of the biggest threats to material performance in both the low earth orbit (LEO) and deep space environment. However, while significant test data exists for LEO atomic oxygen (AO) collisions, further research is needed on the effect of high-energy collisions that can potentially occur in deeper space. As such, this study investigated using the ReaxFF force field in molecular dynamics to simulate the impact of atomic oxygen on two common spacecraft metals, silver and aluminum. This study used a Wigner-Seitz defect analysis to track the damage evolution of the remaining substrate during impact. Results indicated that for both silver and aluminum the number of defects and depth of damage increased linearly with impact energy. While silver was shown to have a higher erosion yield than aluminum, its substrate formed less defects at all impact energies considered. The source of this discrepancy was attributed to the lower energy needed to form vacancies in aluminum as compared to silver. Our results show that while erosion is certainly an important parameter in measuring the damage to a material by high-energy impacts, it is not sufficient to describe the amount of damage and state of the remaining substrate. Overall, this study demonstrates the potential for molecular dynamics simulations to be used to compare material performance and degradation in harsh deep space environments where testing may not be possible.