Abstract: Aiming at the autonomous rescue mission under the thrust failure condition of the launch vehicle, an online capability assessment and autonomous planning method was studied based on the indirect method. The optimal control problem with the maximum energy at the orbit injection point was constructed. Under the constraints of the inclination of the orbit and the path angle of the orbit injection point, the relationship between the speed of the orbit injection point, the height of the apogee, the height of perigee and the height of the orbit injection point was discussed through a numerical method. A feature quantity was designed to perform the orbital capability evaluation. Taking the highest perigee height as the selection criterion for rescue orbit, an autonomous online planning strategy was proposed based on the orbital capability evaluation. When it was judged that it can enter the circular orbit, the secant method was used to solve the largest circular orbit. Otherwise, the Newton method was used to solve the highest elliptical orbit. Simulation results show that the autonomous planning method proposed meets the requirement of online guidance in terms of effectiveness, convergence and realtime performance.

Key words: launch vehicle, indirect method, feature quantity, capability evaluation, autonomous planning