橋本 樹明

Touchdown technology on target planet is important for detailed space exploration. Due to the limitation of mission time, safe landing in the vicinity of area of interest is essential even if the area is unsafe with slope or stepped surface. Conventional 4-leg landing gear has disadvantages for landing on slope because of tradeoff problem between shock absorption and attitude maintenance. In this paper, a novel landing gear is proposed for shock absorption and landing stability. Computer simulations of proposed landing gear in presence of horizontal velocity have demonstrated satisfactory performance.

In the lunar-planetary exploration, most of landers made a landing on flat areas of surface, because there are a lot of rocks craters and hills on lunar-planetary surface. For the next generation lunar-planetary exploration, the development of a highly accurate landing technology is demanded to land on the complex terrain. The navigation-guidance technology and hazard avoidance have been studied for the safe landing. Moreover the development of landing leg is required for the safe landing in the final phase of landing sequence. This paper presents the development of experimental system of active landing leg, and examine the landing shock response. In addition, we consider the effectiveness of active landing leg and the application to the control method of lander's overturn prevention.

On the landing of a spacecraft, a large shock load leads to undesirable responses, such as rebound and trip. The authors have discussed the control problem of these shock responses by momentum exchange impact dampers (MEIDs). The optimal design parameters of MEIDs for the landing of a spacecraft are investigated. The parameters are crucial for applications of MEIDs. This paper discusses the parameters of MEIDs with single-axis falling type problem, which is the most fundamental problem. It is found that the rebound height is proportional to the mechanical energy of the spacecraft. Thus, the optimal design parameters of the MEIDs correspond to the parameters that minimize the mechanical energy. Then, in order to improve the performance of the MEIDs, a novel MEID - HMEID (Active/Passive-Hybrid-MEID) has been proposed. The HMEID combines actuators with passive elements such as contact springs. Based on the optimal design result of the MEIDs, a stiffness control is applied to the HMEID in order to suppress the mechanical energy further. Simulation studies reveal that the HMEID can effectively reduce the influence of shock responses. The robustness of the HMEID against the stiffness of the landing ground is shown. The feasibility of the HMEID is also discussed. The effectiveness of the HMEID is superior to that of PMEID, even if the actuator has a dynamics with a large electric time constant or force constraint.

JAXA is developing the balloon-based operation vehicle as a new micro-gravity experimental device. The vehicle is carried to the stratosphere by a balloon and released. Micro-gravity environment is provided in the body during free-fall. The vehicle is retrieved in the sea because of safety and reuse. Therefore, there is the serious problem that the airflow dominate the decision of experiment. To solve the problem, pull-up maneuver is adopted after the free-fall experiment. The vehicle flies horizontally after the pull-up and guided to the sea area. This paper discussed about the effects of the maximum aerodynamic moment from the point of view of optimal control theory.

現在JAXA では,高々度気球からの自由落下を利用した微小重力実験装置の開発が進められている.この装置の特徴は,独特の二重殻構造を持つ点にあり,気球からの自由落下中に,内側の実験部を機体内部で浮遊させることで,30 秒から60 秒の良質な微小重力環境が得られる.落下中の機体姿勢制御,および実験部と機体内壁の隙間制御用に,合計16 基の50N 級コールドガスジェットスラスタが搭載されている.本稿では,微小重力実験装置用に開発されたガスジェットスラスタの設計と,その地上性能試験結果,飛行試験による実証結果について示す.