Erosion of Spacecraft Metals due to Atomic Oxygen: A Molecular Dynamics Simulation

Atomic oxygen (AO) impacts on spacecraft materials represent one of the biggest threats to material performance in low Earth orbit (LEO). However, testing material performance in LEO is difficult and can be cost prohibitive. As a result, research has shown the potential to use the reactive force field (referred to as ReaxFF here) in molecular dynamics to describe the degradation process of several commonly used polymers. However, no research has been conducted on using ReaxFF to model AO impacts on spacecraft metals such as silver and gold. Therefore, the purpose of this study is to investigate whether ReaxFF can accurately model the impact of high-energy AO on silver and gold. These simulations studied both the erosion and temperature evolution of the slab as a function of the number of impacting oxygen atoms. Overall, after impact with 100 oxygen atoms, the erosion coefficient of silver closely matched previously reported results for erosion in LEO. To verify the process, the simulations were also run with gold: a metal known to resist degradation. Unlike the silver slab, gold showed very little erosion after 100 impacts. These results clearly demonstrate the potential of ReaxFF as a cost-effective method to simulate test conditions in the LEO.