Advanced guidance scheme for lunar descent and landing from orbital speed conditions

Precise landing technology is one of the most important technologies for future lunar or planetary exploration missions. To achieve a precise landing, an advanced guidance scheme is necessary. This paper outlines a comparison of different solution methods for motion control equations utilized in guidance schemes for lunar descent, and proposes an advanced solution that allows a full depiction of descent vehicle motion from orbital states down to the final landing event. In the conventional solution methods, there exist some poor assumptions such as during descent, constant vertical gravitational acceleration is the only other force acting on the descent vehicle. This inadequate postulation limits the validity of the system solutions within a very low altitude terminal descent area; that is, close to the lunar surface. In this paper, an advanced descent solution is proposed where the centrifugal acceleration term is retained along with the gravitational acceleration term. It allows a complete representation of the descent module motion from orbital speed conditions down to the final landing state. Mathematical derivations of the new scheme are verified in terms of a conventional scheme, and comparative simulation results for a fully integrated solution, conventional schemes and a proposed advanced scheme are demonstrated to test the performance.