Generalized Treatment of Energy Accommodation in Gas-Surface Interactions for Satellite Aerodynamics Applications

TL;DR

This paper introduces a generalized model for gas-surface interactions in satellite aerodynamics, improving accuracy in energy accommodation representation across various flow regimes, including hypothermal and hyperthermal conditions.

Contribution

It derives a new general expression for the temperature ratio of reflected to impinging particles, valid for any molecular speed ratio, enhancing existing models for GSI in VLEO.

Findings

New general temperature ratio expression derived

Hyperthermal approximation shown as an asymptote of the general model

Improved modeling accuracy demonstrated in VLEO scenario

Abstract

In the context of satellite aerodynamics in the Very-Low-Earth-Orbit (VLEO) regime, accurate modeling of gas-surface interactions (GSI) is crucial for determining aerodynamic forces and torques. Common models such as Sentman's assume that gas particles are reflected diffusely from a surface, which leads to the incorporation of energy accommodation into the model. This technical note discusses the limitations of existing approaches for handling energy accommodation and provides a generalized treatment thereof that is valid for any molecular speed ratio. A new general expression for the temperature ratio of reflected to impinging particles is derived, which, when used in a GSI model, retains its validity even in hypothermal flows. Additionally, a simplified hyperthermal approximation is presented, proven to be an asymptote of the general expression, and shown to be an improvement upon existing approximations by comparison for a realistic VLEO scenario. The results contribute to a better understanding and modeling of GSI, potentially benefiting scientific investigations and operational applications in satellite aerodynamics.