Control strategy of launch vehicle and lander with adaptive landing gear for sloped landing

Abstract

The ability to perform safe landing is of great concern for reusable launch vehicles and landers; however, sloped terrains severely limit the degree of landing safety. To ensure that the launch vehicle and lander land safely, a novel control strategy was built for them. The control strategy depends on the slopes of terrains, which are measured by laser scanning machines. If the measured slope of a terrain is higher than 18% (10°), the lift of vehicle is increased by its engines to allow it to leave the terrain. When the measured slope of a terrain is lower than 18% (10°), the launch vehicle and lander are allowed to land on the terrain. To ensure that the launch vehicle and lander land on a sloped terrain safely, a new adaptive landing gear was designed for them. In the adaptive landing gear, each landing strut contains a shock absorber and an actuating cylinder. The actuating cylinders are controlled to adjust the angles of landing struts to ensure that all landing struts touch down simultaneously. To analyze the landing responses of landing struts, landing dynamic models were established for them. A set of vertical drop tests were used to validate the landing dynamic models. After the validation, dynamic simulations were used to analyze the influence of the adaptive landing gear on the landing responses of landing struts. The landing struts of the adaptive landing gear touched down simultaneously, and their landing responses were compared with traditional landing struts. The comparison verified that the adaptive landing gear decreased the maximum axial force of the most compressed shock absorber. As the maximum axial force of the shock absorber was decreased, its buffer efficiency was increased to 83%. The adaptive landing gear increased the slope limit of terrain when it was equipped on launch vehicles and landers. The launch vehicle with the adaptive landing gear landed on a 55% (29°) sloped terrain safely, and the lander with the adaptive landing gear landed on a 78% (38°) sloped terrain safely.