Tatsuaki Hashimoto

Lunar or planetary exploration is scientifically meaningful because they can give us the hint to throw a light on the origin and evolution of the solar system or the earth, the inner structure of planets, etc. In lunar or planetary exploration missions, it is important to save the weight of spacecraft. Light weight spacecraft leads to low cost and getting more chance to go to the space. Conventionally a lander carries a rover to the surface of the celestial body and the rover traverses the rough terrain to explore in wide region. If the lander and the rover are united, however, the total weight of the spacecraft could be reduced. The authors have already proposed a novel pulley suspension mechanism, which is called Load Equalization Pulley Suspension mechanism: LEPS mechanism, for rovers. The performance of the proposed mechanism as a suspension mechanism of rovers has been evaluated. In this paper, the application of LEPS mechanism to the landing gears of the lander is discussed. By applying the proposed mechanism to the landing gears, the lander can move around the wide region of the surface after landing. The landing dynamics model of the proposed "Movable lander" with LEPS mechanism is introduced. The landing performance is evaluated by 2-dimensional model. The simulation results show that LEPS mechanism has an advantage over normal landing gears.

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.