Molecular dynamics simulation of gas-solid interaction on the surface of ultra-low orbit spacecraft

In order to accurately simulate the aerodynamic characteristics and optimize the aerodynamic layout of spacecraft in ultra-low orbit, based on the physical mechanism of high-speed incoming gas and wall interaction faced by ultra-low orbit spacecraft, molecular dynamics methods were used to analyze the influence and mechanism of incoming gas parameters (gas temperature, macroscopic incoming gas velocity, velocity direction) and solid surface conditions (wall temperature) on the momentum and energy accommodation coefficient in the gas-surface interaction process. Research has shown that accurate calculation of momentum and energy accommodation coefficients requires consideration of the combined effects of gas dynamic parameters and wall conditions. Within the wall temperature range of 150-450 K, as the wall temperature increases, the tangential momentum accommodation coefficient remains almost unchanged, while the normal momentum accommodation coefficient and energy accommodation coefficient decrease. The tangential momentum exchange between gas and wall is not sensitive to the change of wall temperature. In the range of macroscopic inflow gas temperature from 500 K to 2000 K, as the macroscopic inflow gas temperature increases, the tangential momentum accommodation coefficient remains almost unchanged, while the normal momentum accommodation coefficient and energy accommodation coefficient increase. The magnitude and direction of macroscopic incoming gas velocity have a coupling effect on the accommodation coefficient. Within the range of macroscopic incoming gas velocity from 100 m/s to 1100 m/s, tangential velocity and normal velocity have opposite effects on the tangential momentum accommodation coefficient. An increase in tangential velocity leads to a decrease in the tangential momentum accommodation coefficient, while an increase in normal velocity leads to an increase in the tangential momentum accommodation coefficient. Therefore, the accurate momentum and energy accommodation coefficients are the result of the combined action of gas parameters and solid surface conditions.