Drag analysis incorporating atomic oxygen adsorption in Very-Low-Earth-Orbit

Abstract

Very-Low-Earth-Orbit (VLEO) is gaining attention; however, spacecraft in VLEO are exposed to atomic oxygen (AO), which can significantly affect gas-surface interactions (GSI) and drag. To address this challenge, the AO adsorption adaptive a (AAA) method is developed, utilizing the surface chemistry framework within Direct Simulation Monte Carlo (DSMC) to simulate AO adsorption and desorption, and is integrated into the Maxwell GSI model. Validation with reference data derived from measured satellite drag using atmospheric model demonstrates that the AAA method accurately predicts the energy accommodation coefficient, a . To analyze drag in VLEO, the drag coefficient, C D , is decomposed into three mechanisms: adsorption, desorption, and gas-surface collisions without adsorption or desorption, based on momentum transfer to the surface. The drag coefficient from adsorption, C D,qdS , increases with altitude or reduced solar activity due to lower AO surface coverage, which results in higher adsorption probability. The drag coefficient from desorption, C D,deS , follows a similar trend but remains smaller than that from adsorption. The proportion of C D,adS and C D,deS relative to the total CD increases significantly, exceeding 79% at higher altitudes or under reduced solar activity.