A new strategy for lunar soft landing
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A new strategy based on a windlass device is proposed to deal with the terminal descent of a lunar soft landing mission in this paper. The lunar lander considered here consists of a rover and an assist module (AM) which is equipped with three decelerating thrusters and a lateral thruster. The rover and the AM are connected by a tether (mass is negligible) which winds around the windlass. The dynamics of the terminal descent process is modeled. The guidance laws for the terminal descent phase are derived. Both fuel optimality and lander safety are considered.
The design of the terminal guidance laws in this paper are separated into three stages: firstly, finding the activation point of the decelerating thrusters to minimize fuel consumption; secondly, determining the tensile force of the tether for deployment; and finally, designing the tether’s tensile force to make the rover track the desired velocity-altitude profile. The proposed soft landing strategy needs only the measurements of altitude and vertical velocity. Therefore, it is easy to implement. It effectively prevents the decelerating thrusters’ plume from damaging the lander due to ground interference. Moreover, it is robust against the uncertainties of initial altitude and vertical velocity. Numerical simulation results illustrate the feasibility of the proposed soft landing strategy.
KeywordsVertical Velocity Tensile Force Lunar Surface Soft Landing Assist Module
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