Gas-Surface Scattering Dynamics in Very Low Earth Orbit

A physics-based framework for gas-surface interactions will be developed that maintains its predictive power regardless of the material (surface) or the prevailing operating conditions. This universal framework will expedite the spacecraft material selection process and facilitate a direct transition to the prototype phase for systems in VLEO. Aerodynamic performance in VLEO is exclusively determined by the interplay of atomistic interactions of gases with material surfaces. These interactions range from purely specular (no energy exchange) to fully diffuse (complete energy exchange). Presently, most drag predictions rely on idealized models of specular or diffuse interactions. Quantities of interest (drag or concentration) can differ by an order of magnitude between these two extremes. Models for gas-surface interactions beyond these idealized limits have been developed but are constrained to specific materials and a limited set of fixed conditions.