Aerodynamic shape optimization of space vehicle in very-low-earth-orbit

Space vehicles orbiting in Very-Low-Earth-Orbit (VLEO, h = 200∼300 km) experience considerably large aerodynamic drag due to high air-density in comparison with Low-Earth-Orbit (LEO, h = 600 ∼ 700 km). Therefore, the optimization of vehicle shape via minimization of aerodynamic drag is essential for accurate estimation of satellite lifetime and fuel budget at the design stage. In this study, the aerodynamic drag is computed with direct simulation Monte Carlo (DSMC) because even in VLEO, whose free stream Knudsen number is sufficiently large, some errors are still found in the prediction using free molecular approach. In order to find the optimized configuration, we vary the shape of frontal surface normal to the flight direction. Interestingly, the effects of such geometrical change appear distinctively depending on the gas-surface interaction (GSI, diffuse or specular) which can be represented by the thermal accommodation coefficient. The satellite aerodynamic characteristics including force, torque, and thermal loading are also identified by changing the pitch and the side angle.