Entry guidance law design for lunar return crew module

Aiming at entry guidance mission of a mooncraft with the second universe velocity more or less, the reentry guidance law which meets various constraints, including G-load, heating and landing site location constraints, was studied. The lunar return crew module is a ballistic-lift vehicle with low lift-to-drag ratio, the strategy calls for controlling the trajectory by modulation of the magnitude and sign of the vehicle's bank angle. The determination of the magnitude of bank angle was formulated as a nonlinear univariante root finding problem, while the sign of the angle was dependent upon the reversals in accordance with the lateral corridor, which was treated as a function of velocity. Integrated dispersions Monte Carlo simulations were performed to evaluate the performance of the proposed approach, and the results show that the downrange standard deviation is about 30 km, and the cross range standard deviation is smaller than 5 km. In addition, the working factors on bank rate are analyzed, and the relation between the feedback gain factor regulation and guidance precision is proposed.