Reactive Molecular Dynamics Simulations of Atomic Oxygen Degradation of a Polyimide Film

Polyimide films are widely used in multi-layer insulation (MLI) on spacecraft exteriors due to their favorable thermal properties and stability. In the Low Earth Orbit (LEO) environment, highly reactive atomic oxygen (AO) impinges on orbiting materials at high speed. Prolonged exposure to this AO flux causes surface erosion and degrades material properties. Here, we use fully-atomistic, reactive molecular dynamics simulations to investigate AO-induced damage to a Kapton film under simulated LEO conditions. We apply the reactive force field ReaxFF with parameters from Rahnamoun and van Duin, J. Phys. Chem. A 118, 2780-2787 (2014). We analyze key degradation metrics including mass loss, penetration depth, and the volatile species produced to determine how they depend on material composition, temperature, and AO flux. The results of this study aim to clarify fundamental polyimide erosion mechanisms and aid the development of physics-based predictive models to forecast material degradation based on space weather.