Abstract:

We develop a spacecraft rendezvous policy that ensures safe, collision-free trajectories under various thrust failure scenarios. We use backward reachable sets to characterize the unsafe region where, if a failure occurs, a collision between a chaser and a target spacecraft cannot be avoided with the remaining available thrust. The chaser spacecraft is guided towards the target via model predictive control that ensures abort-safety by avoiding the unsafe region, which is locally convexified with half-spaces. Simulations of the rendezvous policy on various orbits demonstrate that the approach ensures safe aborts in the event of multiple thruster failures, passive abort safety under total thruster failure, and achieves some robustness to unmodeled orbital perturbations.