Electric propulsion using xenon is not practical due to the huge amount of propellant required to transport space solar power satellites because the production of xenon is limited. Significant mass reductions in high-pressure tanks and entire systems can be achieved by using sublimable materials that are solid at ambient temperature and pressure. Further mass reduction is also expected because sublimable materials tend to have high molecular weights, which increases the thrust density of an ion engine and reduces its size. The operational test of an ion engine using adamantane is presented and the results are compared with those of argon.

  Solar power satellite (SPS), which consists of a large scale power generation and transmission panel, generates electricity by sunlight in orbit and sends energy to the ground with microwave beams. One of the issues to realize SPS is the thermal deformation of the panel due to the temperature difference between the front and back of the SPS. Therefore, it is required to maintain the flatness of the panel. To solve this problem, we are studying the flatness control of panels by carbon nanotube actuators (CNA). CNA is a polymer actuator whose main component is carbon nanotubes, and has excellent electrical properties. And it is expected to be applied to space in the future. In this paper, we report on basic study on SPS application of CNA.

  We are studying and developing a hybrid structure that combines a thin film structure and a bulk structure in order to significantly reduce the mass of solar power satellite (SPS). One of the issues of realization for SPS is the enormous number of space transportations. Therefore, to reduce the number of space transportations, we're considering replacing some of the functions installed in the bulk structure with a lightweight and thin flexible structure. In addition, it is necessary to consider thermal deformation due to periodic changes in the amount of solar radiation from the viewpoint of microwave power transmission for the SPS. In this paper, we described the results of thermal analysis of hybrid structures that combines the thin film and the bulk structure for SPS. We evaluated the thermal deformation of hybrid structure. Also, we suggested hybrid structure that satisfies a requested value which is from the microwave power transmission of the tethered SPS.

  Microwave rocket has been studied as a first stage rocket. The high-power millimeter-wave oscillator gyrotron, which is necessary for the launch of Microwave rocket, is currently capable of oscillating millimeter-wave between 1 and 1,000 GHz, and in principle Microwave rocket can be realized at any frequency. In this study, we investigated how the launch cost changes when the oscillation frequency is changed. As a result, in the case of the fixed-focus transmission system, the optimum frequency is 28 GHz because the aerodynamic drag loss is dominant when the frequency is too small, while the atmospheric attenuation loss is dominant when the frequency is too large. On the other hand, in the case of the variable-focus transmission system, the optimum frequency is 5.8 GHz, where the atmospheric attenuation loss is the lowest, because the beam spread does not affect the receiving antenna diameter.

  Japan Space Systems has been promoting and engaged in the development of the SSPS since 1993, and now, according to the road map established in the FY2007, the phased development project to realize the operational in the year of the 2050 is under progress. In the current phase of the project, the development of the power generation and transmission panel, the improvement of the efficiency of the microwave power amplifier stage and the demonstration of the long distant power transmission have been on going to clear the outline of the next phase space demonstration activities from the LEO satellites.

  An ultralight antenna panel structure made of CFRP thin plate was proposed to realize Space Solar Power Systems. In the proposed antenna structure, thermal deformation occurs due to the difference in the coefficient of thermal expansion and causes negative effects in the antenna system, especially for the thin plate structure. In this study, theoretical analysis was conducted against a thin plate structure with a single antenna patch using the equivalent inclusion method for plates. The results were validated with finite element analysis. Furthermore, sensitivity studies regarding the layer thickness were conducted and a new structure was proposed.

  The Multiple Folding Array Antenna can furl and deploy many panels with ordinary hinges, and can be easily developed to two-dimensional deployment. On the other hand, the performance of the antenna is impaired because of steps between the panels when the antenna is deployed. The panel steps are corrected in phase in the normal direction of the antenna, but can not be fully corrected off the normal direction. In this paper, we obtain the panel step distribution in an antenna deployed in two dimensions, assuming that the antenna is installed on an actual satellite. The radiation characteristics of the deployed antenna are calculated so that the radiation pattern changes depending on the panel step will be clarified.

  A gyrotron is a vacuum tube which generates millimeter waves from kinetic energy of gyro motion of electrons. In the University of Tokyo, a gyrotron with power of 600 kW, frequency of 94 GHz and pulse duration of 100 microseconds has been developed for the purpose of thrust generation experiments of Microwave Rocket. In order to maximize the energy conversion efficiency, the distribution of magnetic field by the super conducting magnet was measured and the gyrotron was installed. The withstand voltage of 40 kV was confirmed before the beam extraction was examined.

  High altitude platform station (HAPS) is a telecommunication platform in the stratosphere and its communication area is expected to expand in developing countries and mountain areas. Microwave power transmission (MPT) is considered as a stable power for long-term operation of HAPS, regardless of day or night. In this paper, we study the MPT system based on the transmission efficiency, including beam transmission and rectification efficiencies, and also study the transmitter antenna shape, frequency, and flight path.

  A demonstration experiment using a small satellite is planned to realize space solar power system (SPS). In this experiment, accurate evaluation of the beam shape transmitted from the satellite is needed. So, the beam shape had been reproduced and evaluated as a parabola antenna. In this paper, the antenna changed to a phased array antenna for more realistic situation. Then, a guideline for base station placement was shown, and the pattern was reconstructed by the two-dimensional minimum square method to confirm its effectivity. In addition, the orbit passing through Usuda as well as Katsuura were shown.

  Solar power satellite (SPS), which consists of a large scale power generation and transmission panel, generates electricity by sunlight in orbit and sends energy to the ground with microwave beams. One of the issues to realize SPS is the thermal deformation of the panel due to the temperature difference between the front and back of the SPS. Therefore, it is required to maintain the flatness of the panel. To solve this problem, we are studying the flatness control of panels by carbon nanotube actuators (CNA). CNA is a polymer actuator whose main component is carbon nanotubes, and has excellent electrical properties. And it is expected to be applied to space in the future. In this paper, we report on basic study on SPS application of CNA.

  Microwave Rocket is being studied as the first stage of a launch vehicle to transport a large amount of space cargo for future space solar power satellite construction. The high-power electron tube, which is indispensable for the launch of Microwave Rocket, is currently capable of oscillating at frequencies from the microwave band to millimeter-wave band. We investigated how the cost of launching Microwave Rocket changes when the transmission frequency is changed. As a result, the optimum frequency for the fixed-focus transmission system was 28 GHz, because the aerodynamic drag loss was dominant when the frequency was too small, while the atmospheric attenuation loss was dominant when the frequency was too large. On the other hand, in the case of the variable-focus transmission system, the optimum frequency was 5.8 GHz, where the atmospheric attenuation loss was the lowest, because the beam spread did not affect the rocket diameter.