Design of guidance law for lunar ascent phase of manned lunar module

A closed-loop guidance law based on explicit guidance is designed for ascent from moon surface and injection of lunar module in manned lunar landing mission. Both coplanar and noncoplanar injection dynamics are presented. Under the condition of constant thrust, both explicit guidance and fuel-optimal guidance based on Pontryagin maximum principle are derived and compared. The numerical simulation is conducted under the condition of the given parameters of Apollo lunar module. The results indicate that explicit guidance is better comprehensively considering saving fuel, anti-interference, ensuring accuracy etc. and it can well solve the problem of noncoplanar injection with a small angle. Therefore, explicit guidance is more suitable for engineering application due to its higher reliability and flexibility.