Abstract: To enable better task accomplishment of space tethered-combination in space debris removal, we propose a de-orbit strategy using Bang-Bang thrust, which is closer to the engineering application. Firstly, a Bang-Bang controller with differential clearance is used to realize the Bang-Bang thrust acceleration of space tethered-combination. In the process of de-orbit using Bang-Bang thrust, the engine needs to be switched on and off repeatedly. Therefore, a new passive winch mechanism is designed to avoid the negative effects of engine switching. A sliding mode controller with input constraints is designed for radial thrust to suppress the in-plane swing of the tether-combination in the process of de-orbit, and the control is also realized by Bang-Bang thrust. The simulation results show that Bang-Bang thrust can achieve similar results with continuous thrust that suppress the in-plane swing angle in a narrow range. The de-orbit strategy can make space tethered-combination complete the mission that drag space debris to graveyard orbit on the basis of ensuring the attitude stabilization control.

Key words: space debris removal, tether-tugging de-orbit, de-orbit strategy, Bang-Bang thrust, space tethered-combination