Toru Tsukano
(Muroran Institute of Technology, Japan)

Stirling engine is an effective electric generator in space. This is because the conversion efficiency of solar energy is high, the influence of the space radiation is little, and the light-weight thermal energy storage system with high energetic density can be used at eclipse. This study is on the thermal energy storage system to generate electric power in the eclipse. We conducted the experimental study and the numerical analysis on the thermal energy storage system. We compared two kinds of thermal storage materials, which are a molten salt and a metal. Lithium chloride and Aluminum were chosen as the candidates of these thermal storage materials in this study. The heat transfer characteristics of lithium chloride and aluminum as the thermal energy storage system were evaluated. Results show that Aluminum can be more effective on the condition where Stirling engine works, even though the latent heat of the Aluminum is smaller than that of Lithium chloride. This is because the thermal conductivity of the Lithium chloride is much smaller than that of the Aluminum. Therefore it is difficult to use the whole thermal energy of lithium chloride.

Ryotaro Sasaki
(University of Kobe, Japan)

It is essential to establish the microwave-beam control system for the realization of the Solar Power Satellite (SPS). The retrodirective antenna is a very promising technology using pilot signal, which is radiated from the receiving site to the transmitting antenna. The active phased array antenna with the retrodirective antenna is already established by the demonstration at the International conference in Toronto, 2009. We have to improve our active phased array antenna from the short transmission to the long distance such as the SPS at geosynchronous orbit for the next step. We brought our active phased array antenna improved for the tests at long distance to Hawaii. The transmission antenna consists of nine panels that can radiate microwave power of 180W at the frequency of 2.45GHz from Mt. Mauna Loa in the big island. On the other hand, the receiving system consists of a pilot transmitter and receiving antenna to measure the received power level of the microwave at Mt. Haleakala in Maui Island. The result of the experiment indicates our transmitting antenna system can be established for the real SPS at the geosynchronous orbit. While, we obtained the interesting data on the transmission at the long distance.

Yoshihide Fujikawa
(University of Kobe, Japan)

Many excellent applications can be realized if small devices such as RFID on the ground can be electrically supplied from orbiting satellites. For example, they may be to survey the ecologies of animals, to observe positional variations on the ground for investigation of the movement of the earth's crust, and so on. We have to develop new microwave transmitters of high power with high gain antenna and to improve devices on the ground for the reduction of the consumption power below negligible power level. We have a plan of the preliminary experiment with power transmitting and receiving system using active phased array antenna in the near future. In the experiment, the high power microwave is transmitted from the active phased array antenna, which has a high gain and can control the microwave beam toward the target devices. The frequency of the received microwave is up-converted to radiate by the devices with some information. The other active phased array antenna, which can be controlled at the same direction as the power transmitting antenna, can receive the returned signal from the devices. The main purpose of this experiment is to examine the possibility of the power transmission from the satellites.

Soichiro Etani
(University of Kobe, Japan)

We believe to establish our retrodirective antenna system for the microwave beam control for Solar Power Satellite with our successes on the wireless power transmission demonstrations in Toronto and in Hawaii. Therefore, we have newly started the design on the sandwich panels for the Practical Solar Power Satellite, which can generate electricity, converted it to microwave and transmit it to the rectenna on the ground. One of the technical issues on the design is a thermal control system, because the highly concentrated solar energy makes the panels to be a very high temperature. We are designing the antenna elements for the microwave power transmission and the configuration of the solar cells in order to use both of the whole faces of the sandwich panels as the radiators. The other issue is to reduce weight and thickness of the sandwich panels as lightly and thinly as possible, which can reduce the transportation cost. Therefore, we are improving the connections between the antenna elements and the high power FET amplifiers, the distribution system of the microwave and electric power which are supplied to the FET amplifiers and so on. We will describe our detailed design on the sandwich panels at our presentation.

Ryota Noda
(University of Kyusyu Institute of Technology, Japan)

In the satellite development, advancements have been made toward higher power operating at a high voltage. As a result, though, the electrical discharge accidents on solar arrays have been confirmed. The electrical discharge causes serious problems for the power generation, halting operation of the satellite. To prevent these electrical discharges, the ground examination becomes important. The state in which the satellite surface potential sinks negatively is called normal gradient potential. It is assumed that a large amount of charge flows into the electrical discharge point; thus, a present ground check generally tests for the discharging current in a normal gradient potential at one point and moves on with other tests. However, the current seems to flow to not only the electrical discharge point but also to other inter connectors when the image during an electrical discharge is examined. So, to examine how the discharge truly acts in a normal gradient potential, the current that flowed to an electrical discharge point and peripheral inter connector was measured with a current probe. The amount of charge that is accepted into the electrical discharge point and peripheral inter connectors when a discharge occurs in a normal gradient was examined.