Dynamics analysis and optimal strategy of pyramid deorbit sail

For space debris mitigation, post mission disposal of constellation spacecrafts in Low Earth Orbit (LEO) is considered as a necessary measure. In LEO region, the deorbit sail device provides an efficient way to accelerate the deorbit process by enlarging the effective area to increase the atmospheric drag and solar radiation pressure (SRP) effects. By considering the two effects, the aim of this paper is to propose an optimal strategy for deorbit sail device in LEO deorbit missions. The deorbit sail is modeled as a pyramid, and the coupled attitude and orbit dynamics of the system is studied. The geometry parameters of the pyramid deorbit sail, such as the number and length of support booms and the flare angle, as well as the position of the spacecraft bus are not limited. In this paper, assume that the deorbit process of the deorbit sail system can be divided into atmospheric drag dominant region and SRP dominant region when either one dominates over the other, and the mixed region when both effects are considered. By simplifying the attitude dynamics model in the orbital plane, two key parameters are proposed to evaluate the stability of the deorbit sail system for different dominant regions. With the key parameters, the influence of geometries on the attitude stability is analyzed for pyramid deorbit sails, and further conclusions about the optimal configuration are obtained from the analysis results. Finally, the attitude planner is designed to make full use of the effect of SRP while ensuring that the surface-to-mass ratio reaches the expected value in mixed region. The attitude control system could make the pyramid deorbit sail system keep the best attitude throughout the deorbit process to obtain the highest efficiency.