Prediction of Gas-Surface Interaction in Very Low Earth Orbit Using an Atomic Oxygen(AO)-Surface Chemistry Models
Abstract
Atomic oxygen (AO) is the predominant species of the atmosphere at altitudes ranging from 200 to 500 km, constituting what is known as very low Earth orbit (VLEO). In this region, oxygen molecules (O2) dissociate into AO through photodissociation, resulting in elevated AO density. AO is characterized as a free radical atom. Since AO is highly reactive and inherently unstable, AO engages in chemical reactions with surrounding species, thereby inducing changes in chemical composition of surface. The most frequent reaction involving AO is adsorption. Adsorption is an adherence of gases, liquids, solutions, or ions to solid or liquid surfaces. In VLEO, adsorption results in the accumulation of AO on spacecraft surface, potentially modifying gas-surface interaction (GSI) and impacting spacecraft aerodynamics. Therefore, precise prediction of AO-surface chemistry and GSI is essential for understanding spacecraft aerodynamics in VLEO. This study numerically investigates the surface reaction process of AO on the spacecraft in VLEO environment. The Direct Simulation Monte Carlo (DSMC) method is employed to simulate rarefied atmospheric flow in VLEO, while a finite-rate surface chemistry model is utilized to capture AO-surface chemistry. An adaptive GSI scattering kernel is developed to incorporate the influence of AO adsorbate. This innovative approach allows for accurate prediction of GSI dynamics without relying on a preconditioned energy accommodation coefficient. Validation of the scattering kernel is performed using flight test data. Finally, the transport of surface reaction products and their effect on the spacecraft is investigated.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 05, 2025
- Source ID
- FA23862414074
Entities
People
- Eunji Jun
Organizations
- Air Force Office of Scientific Research
- KAIST
- United States Air Force