Low-thrust de-orbiting from Low Earth Orbit through natural perturbations

This paper investigates two strategies that exploit low-thrust propulsion and natural effects for the complete de-orbiting of spacecraft from a Low Earth Orbit (LEO). The first strategy aims to actively lower the perigee altitude by low-thrust propulsion to achieve passive drag-induced re-entry. The second strategy aims to actively move the spacecraft by low-thrust propulsion to reach a specific condition that can provoke passive orbital decay by means of the coupled effect of natural perturbations. For each strategy, a sub-time-optimal closed-loop steering law, which is proved to be stable, is designed with the Lyapunov method. Then a set of maps that show the costs of de-orbiting from LEO (i.e., the Δv-budget and de-orbiting time) are plotted as a function of the initial conditions for the two strategies. In this way, the feasible initial conditions to apply the two strategies are identified by comparing the Δv-budget. Before plotting the maps, the averaged low-thrust motion is derived, to reduce the computational load for the orbital propagation of low-thrust motion.