Overview of aerodynamic drag calculation and reduction design for very low Earth orbit satellites

In recent years, Very Low Earth Orbit（VLEO）satellites have become a research hotspot in the field of space technology due to their great advantages in terms of Earth observation resolution, data transfer speed, and communication capacity over traditional satellites. In the VLEO environment, the atmospheric drag caused by collisions between atmospheric molecules and the satellite surface cannot be ignored, and has become 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. This paper starts with the fundamentals of satellite aerodynamic drag and discusses several key factors that determine aerodynamic drag, with a particular focus on the computational analysis of drag coefficients. The gas flow in the VLEO environment belongs to the regime of free molecular flow, where collisions between gas molecules can be neglected. The models for gas-surface interaction between gas molecules and the satellite surface play a crucial role in evaluating the drag coefficient. The fundamental characteristics and common calculation methods for free molecular flow are introduced and evaluated, followed by a focused review of several typical gas-surface interaction models. Furthermore, based on the computational analysis of aerodynamic drag characteristics of satellites, a review of the research progress in drag reduction configuration design is conducted, focusing on three aspects: increasing the aspect ratio, shape optimization, and lateral side smoothing. Finally, several key issues that require significant attention in the future of this field are also discussed.