Takeo Watanabe

An Application of Input Shaping For Electrodynamic Tether System

** In the present study, Input Shaping method is applied to reduce the initial vibrations of electrodynamic tether system. In the initial phase of the propulsion, the electrodynamic force induces vibrations on the tether. Libration and string vibration are undesirable for any missions of the system. These are caused by the flexibility or orbital motion of the system. The different shapers are applied for the vibrations and the input command is designed by multiplying the both shapers respectively. As examples, two cases of de-orbit missions of space debris are analyzed numerically. The results of this study show significant performances of suppressing by employing the Input Shaping applications for tether system.

Experimental Study on Penetration Performance for Sampling of Asteroid Mission

** ** *** * ** *** Target of the asteroid probe known by HAYABUSA is the clarification of origin and evolution of solar system and life. One of the missions is the sample collection of the asteroid. A large amount of sample collection and the collection of the subsurface material and the stratified sample collection etc. have been enumerated To the achievement item of this mission, and the sampling system that is appropriate for respectively is examined. In the stratified sample collection, the Harpoon & Penetrator method (H&P method) is examined. In the present study, the sampling system by the method is tested executed from two aspects. In the first, we study element affecting the performance of penetration. The penetration velocity is changed as a parameter in order to study the relation between the penetration depth and the penetration velocity, and the velocity necessary for 300mm sampling is examined. In addition, influence by the difference of the corer shape is studied by changing the outer diameter of the corer, the relation between the penetration depth and the load is also studied in order to study the effect of the load on penetration. In addition, empirical formula and theory formula in both experiments are established, and compared. In this paper, the results are reported obtained by both of the experimental results.

Periodic motion of compound-tether satellite system on elliptic orbits

Abstract Periodic motion is analyzed on nonlinear attitude motion of a double compound-tether satellite on elliptic orbits. The compound-tether satellite consists of a mother satellite and two subsatellites connected through tether. An elliptic motion is obtained for the attitude motion when the eccentricity is small and the motion is linear. The motion turns to chaotic motion under the influence of the orbit eccentricity when the eccentricity increases to a certain value. The nonlinear attitude motion is studied through the method of nonlinear analysis including the Poincare map and the Lyapunov exponent. The initial condition for the periodic solution of the nonlinear motion is analyzed by an analytical method.

Combined Optimization for Configuration and Control Algorithm, of A Tehtered Space Solar Power Satellite

Abstract Control of a tethered space solar power satellite is studied in this paper. The attitude is gravity-gradient stabilized with employment of tether system. The buss part connected by tether to the solar panel is treated as the proof-mass-actuator. The controllability and controlled performance is analyzed resulting in numerical simulation with sufficient capability of controlling the attitude motion of the present tethered space solar power satellite.