Tether Dynamics Analysis and Guidance and Control Design for Active Space-Debris Removal

TLDR

Active space‑debris removal has become a major research focus, exemplified by ESA’s proposed tether‑based mission to deorbit Envisat. This study designs a guidance and control system for the tethered chaser and examines how tether parameters affect mission performance. Using a lumped‑mass tether model, nine combinations of length, stiffness, and damping were evaluated with a sliding‑mode controller and compared to an LQR, while an open‑loop throttle controller tested three thrust levels. Stiffer tethers with higher thrust consume less propellant, and longer tethers provide superior collision‑avoidance performance if main engines fail.

Abstract

Recent years have seen a steep increase in research being performed toward active space-debris removal. In particular, the ESA has proposed a mission in which a robotic chaser satellite would use a tether to interface with the derelict Envisat and deorbit it. This study focuses on the preliminary design of a guidance and control system to achieve this, as well as on the influence of different tether parameters on mission performance. The lumped-mass model was used to model the tether, and the influence of the number of nodes used was investigated. Then, the mission performances of nine combinations of tether length, stiffness, and damping were evaluated. This was done using a sliding-mode controller for closed-loop relative orbit control and attitude control of the chaser satellite, the performance of which was compared against a linear-quadratic regulator. An open-loop throttle-control system was used for the main engines, for which three different thrust levels were considered. It was found that higher thrust levels with stiff tethers require significantly less mission propellant. Furthermore, long tether designs offer the best performance in case of collision avoidance, if the main engines were to fail during a burn.