Aerodynamic drag analysis and reduction strategy for satellites in Very Low Earth Orbit

Abstract

Research interest in operating satellites in Very Low Earth Orbit (VLEO) is growing due to their potential applications for high quality Earth observation and telecommunication. In VLEO, atmospheric drag is not only a critical issue affecting the attitude control and orbit prediction of satellites, but also a key factor limiting the operational life of satellites. In this work, we first employ the direct simulation Monte Carlo (DSMC) method to calculate the aerodynamic drag of elementary shapes including flat plate, cylinder, and sphere in the VLEO region, which are validated and compared with the free molecular flow (FMF) theory. Then, we calculate the aerodynamic drag of a conceptual VLEO satellite model, and the effects of the orbital altitude, accommodation coefficient of surfaces, and the molecular speed ratio on the aerodynamic drag coefficient are analyzed. Two drag reduction strategies, referred to as lateral side smoothing and shape optimization, are investigated in detail by DSMC calculations. We propose that combining these two drag reduction strategies can achieve better drag reduction effect. In addition, we modify the optimum aspect ratio theory by considering the rarefied gas effect to give a better prediction of the optimum aspect ratio for aerodynamic drag at lower orbital altitudes.