Optimal rescue trajectories for manned maneuvering unit

Based on Hill guidance, the optimization of trajectories for the manned maneuvering unit rescuing an astronaut or equipment that becomes separated from a space station is studied because of minimum fuel, rendezvous accuracy, and time constraint requirements. The Hill guidance targeting errors induced by navigation error, target measurement error, and actuation error are analyzed. The minimum fuel solutions for 17 typical cases are found, and designing rules for the rescue trajectories are developed. A multi-impulse Hill guidance scheme is presented for simultaneously realizing accurate rendezvous and saving energy. Simulation results reveal that the multi-impulse scheme is much more superior to the conventional double-impulse Hill guidance scheme in rendezvous accuracy and consumes nearly the same amount of fuel as the later does.