In many cases, single-break vacuum circuit breakers are used as circuit breakers, and so the characteristics of doublebreak vacuum circuit breakers have not received sufficient attention. This report describes our investigations of the interruption characteristics of double-break vacuum circuit breakers. We have investigated and clarified the relationship between the voltage distribution ratio and the post arc current in double-break vacuum circuit breakers by measuring the post arc current in the single-break vacuum circuit breaker, the voltage distribution ratio, and the post arc current in double-break vacuum circuit breakers. Our investigation has shown that the post arc current scatter of the spiral contact is much larger than that of the axial magnetic field contact. This result shows that the bias of the voltage distribution ratio was caused by the imbalanced post arc current in each vacuum interrupter in the double-break vacuum circuit breaker. Therefore, we conclude that axial magnetic field contacts are suitable for double-break vacuum circuit breakers.Index Terms-Double-break vacuum circuit breakers, grading capacitors, post arc current, vacuum interrupters.

The Japan Aerospace Exploration Agency (JAXA) is studying the feasibility of using the solar power sail as a new propulsion engine for deep space exploration missions. In this paper, the sail shape and equipment layout for missions utilizing small-sized solar power sails are proposed. The two-stage deployment method of the sail is also proposed. The sail need to be deployed statically at the first stage, and two types of deployment mechanisms are introduced. On the other hand the second stage of the deployment can be performed dynamically, and the oscillating motion of the membrane is converged by tethers connecting the membrane to the main body. The deployment motions are analyzed by numerical simulations using multi-particle models in order to verify the deployment. They are compared with the results calculated by finite element method models. The numerical simulation results are discussed from the technological viewpoint of the sail deployment dynamics and mechanisms.

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Miniaturization and high performance are always required for space equipments. But, it can be said that miniaturization and high performance are generally contradictory requirements. In this research, a fluid loop insulation and cooling system was built as a means of realizing both miniaturization and high voltage. For the working fluid of the system, fluorinated inactive liquids were used which can provide high electrical insulation and thermal conductivity. In this paper, to begin with, the electrical insulation property of the fluorinated inactive liquids was verified by an experiment. Then the dynamics model of the constructed insulation and cooling system was derived by a system identification experiment. Finally, a control law for temperature control was constructed using the estimated model and cooling performance of the system was examined by both numerical simulations and experiments.

In this paper, the attitude motion and attitude control strategy of spinning solar sail are discussed. As the spinning type solar sail does not have any rigid structure to support its membrane, the impulsive torque by the RCS can introduce oscillatory motion of the membrane. Thus, an “oscillation free” attitude controller is needed, which takes into account the flexibility of the membrane and avoid unnecessary oscillatory motion. First, the dynamics model and numerical model were introduced, and the validity of these models and dominant out-of-plane membrane vibration mode is examined by membrane vibration experiment and comparison between both models. Then, based on the analysis of the dynamics of torque-free motion, it was shown that a spinning solar sail has three oscillation modes of nutation, one of which is equal to the spinning rate of the spacecraft. The dominancy of each nutation mode was analytically and numerically discussed. Then, we discussed the spin axis maneuver control using conventional RCS. It was analytically shown that continual impulsive torque synchronizing the spin rate can excite nutation velocity and that a controller is needed to damp the nutation while controlling the spin axis at the same time. The authors proposed new controller named Flex-RLC and improved one. Their effectiveness was verified by numerical simulations using precise multi-particle numerical model which can express higher order oscillatory motion of the flexible membrane, and it was found that the proposed method can control the attitude of spinning solar sail while drastically reduces the nutation velocity compared with conventional control logic. So, it can be said that the proposed method is promising fast and stable controller for spinning solar sail.