Microwave Rocket is a space transportation system that uses millimeter-wave energy oscillated from gyrotrons on the ground to generate thrust. A gyrotron with a frequency of 94 GHz, output power of 600 kW, and pulse duration of 100 μs has been developed at the University of Tokyo for millimeter-wave discharge experiments. The gyrotron tube axis was aligned with magnetic field axis and the oscillation output was improved by a factor of about three. The oscillation output was estimated to be 26.31 kW, and the energy conversion efficiency was 4.1%. However, considering that the theoretical efficiency is about 17%, further study is needed for optimization of the axis position and the oscillation output measurement method.

  For the realization of the Tethered-SPS, the thermal feasibility of the power generation/transmission panel should be confirmed. In this study, we performed thermal analysis of the panel and showed the necessity of thermal countermeasures against high temperature. As a result, comparing multiple methods for thermal countermeasure, it was shown that the improvement of power generation efficiency of solar cells from 20% to 50% can work as a countermeasure. As another countermeasure, the improvement of thermal conductivity between the power generation surface and power transmission surface is attempted by connecting them by a high thermal conductor. It was shown that the required power generation efficiency can be suppressed to 40% by using the high thermal conductor.

Wireless Power Transmission (WPT) technology using a satellite-to-satellite system represents a valuable and convenient technology for transferring power wirelessly among Space Solar Power Satellites (SSPS) to Satellite and potential upcoming interplanetary missions. This direct transmission offers a possible solution to deliver continuous, convenient, and unlimited energy supply to satellites to help replace traditional power storage and reduce the weight and ultimately the costs of launching satellites. Satellite industries traditionally use photovoltaic cells and nuclear generators to satisfy the needed electricity by spacecraft. Current power generation and effective management systems occupy up to 10-25% of the satellite's mass. The concept of laser-based WPT from Energy Satellite (E-Sat) can overcome substantial problems. This consistent idea can be adopted for spacecraft by developing a constellation of E-Sat called Energy Orbit (E-Orbit) to supply sufficient power to spacecraft within range. It will increase the impressive performance and operational lifetime. In addition, creating 1600 E-Sat’s constellations to fulfill the power demand in Low Earth Orbit. The overall efficiency variation depends on the selection of Laser, transmitter, transmission distance, and photovoltaic cells, the same as increasing the maximum transmission efficiency of information in a wireless communication network. Consequently, in general, and adequate guidelines of the satellite-to-satellite power transmission system design in practice. The development and demonstration of this technology can help fulfill Space Solar Power Satellite’s idea to transfer gigawatts of renewable energy to Earth.

  Utilizing the phase-controlled magnetron technology, we examined a long-distance high-power microwave wireless power transmission system. We suggest constructing a phased array of high-power microwave output using the phase-controlled magnetrons. The phase-controlled magnetrons have completed which achieved within ± 1° phase accuracy, and high-efficiency power combining can be realized. The transmission beam control is performed from the injection signal which can avoid the loss due to the high-power phase shifter. In this paper, we designed a 12-kW power transmission system using sixteen 5.8-GHz band magnetrons and examined a high-power microwave power transmission system. We also conducted cost evaluations for actual experiments.

  A large amount of propellant is consumed for the construction and maintenance of space solar power systems. As a propulsion system suitable for mass transportation, a miniature water Hall thruster is being developed. An anode, a main discharge part, was successfully discharged by water, and the performance was estimated to be 130 W of discharge power, 3.4 mN of thrust, and 460 s of specific impulse. A cathode, an electron supply part, was conducted spectroscopic measurements, and the performance was estimated to be 110 W of power consumption and 490 mA of electron current. In the future, the discharge of the anode will be maintained and the electron current from the cathode will be extracted, and then a coupling operation will be performed.

  We are developing high power microwave antennas whose power is more 100 W/m² for spacecrafts. Discharge may occur a lot of noise, energy losses and microwave system malfunctions. Therefore, we must suppress discharge phenomena on the antennas. In the space environment, their mechanism is different from one in the ground. And it depends on their shape and material. In this study, we used vacuum chamber simulated space environment and observe discharge phenomena on high power microwave antennas using optical cameras. From the results, we estimated their mechanism and tested for effectiveness of their suppression methods.

  NASA / DOE designed the concept of SSPS in the 1970s. In this system, the solar panel was always directed toward the sun in geosynchronous orbit, and the microwave beam radiator was oriented toward the rectenna on the earth. Between these, a rotary joint capable of transmitting high power is required. However, it was difficult to manufacture a rotary joint capable of transmitting high power. Since then, a structure in which a solar cell panel and a microwave antenna are integrated has been proposed. This time, we examined a rotary joint using liquid metal. We report that it has possibility to transmit GW class DC power directly, generate little heat, and make it lightweight and compact.

  The Multiple Folding Array Antenna has a large deployment and storage ratio and can be deployed in two-dimensions. Compared with parabolic antennas, it is easier to install in small satellites and space probes because it is based on square panels. In addition to the panel shape, the element arrangement is also an important parameter in the array antenna. In this paper, the configuration of the power transmission antenna is considered in the case that CubeSat is applied to beam power transfer. The radiation characteristics of the main beam and side lobe shapes are discussed and compared. We also compare the square arrangement and the checkerboard one.