Hiroyuki Koizumi / Associate Professor / Division of Transdisciplinary Sciences
Department of Advanced Energy / / Space Propulsion, Small Spacecraft

Career Summary
2000: B.S., Department of Mechanical Engineering, Keio University
2002: M.E., Department of Aeronautics and Astronautics, the University of Tokyo
2003: Research Associate, the University of Tokyo
2006: Ph.D., Department of Aeronautics and Astronautics, the University of Tokyo
2007: Assistant Professor, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
2011: Associate Professor, the University of Tokyo
Educational Activities
Graduate school: Propulsion and Energy Systems, Advanced Energy Conversion
Undergraduate school: Space Propulsion I and II, Introduction to space engineering (School of Engineering)
Research Activities
Our recent major areas of interest are micro-propulsion for small spacecraft and electric propulsion using plasmas. Small spacecraft provide low-cost access to space and enable even universities and venture companies to enter the space industry. The potential of small spacecraft will be fully realized with the advent of micro-propulsion systems. Electric propulsion, which has been studied for a long time, eventually entered the application era around 2000. It has higher propellant efficiency than conventional propulsion and its utilization has become a new standard for spacecraft.
1) Small ion thruster
We are currently working on a microwave-driven small ion thruster that will be installed on a small 50-kg satellite. The plasma source has a 1-cm diameter and an extracted/accelerated ion beam provides 200-400 micro-N thrust and 1000-1500 s specific impulse. We have already developed two flight systems using these small ion thrusters for a small satellite, HODOYOHI-4, and a small space probe, PROCYON, that were launched in 2014.

Small ion thruster
2) Small solid thruster
We are also working on a small solid thruster using boron-potassium-nitrate propellant for 1-kg CubeSats to 100-kg satellites. The solid propellant provides a simple, lightweight structure suitable for small satellites. We are currently investigating a 150-Ns thruster that weighs just 500 g. The single thruster is suitable for a CubeSat and the clustering enables application to a wide range of satellites. These thrusters provide a quick, high thrust useful for de-orbiting satellites.

Combustion test of small solid thruster
3) Helicon-wave plasma thruster
We are carrying out a basic study on 100-kW-class electric propulsion for future advanced missions such as manned Mars exploration and asteroid exploration. Such high power electric propulsion requires an electrodeless structure for both plasma generation and plasma acceleration. We propose a combination of helicon-wave plasma and inductive acceleration to provide electrodeless, high power electric propulsion.

Helicon-wave plasma and conceptual diagram of thruster
1) Koizumi, H., Komurasaki, K., Aoyama, J., and Yamaguchi, K., "Engineering Model of the Miniature Ion Propulsion System for the Nano-satellite," Trans. JSASS Space Tech. Japan, vol. 12, pp. Tb_19-Tb_24, 2014.
2) Masuda, Y., Koizumi, H., Hayashi, T., Nakano, M., Komurasaki, K., and Arakawa, Y., "Increase in Performance of Laser Ignition Micro Solid Rocket by Control of Combustion Chamber Pressure," The Japan Society for Aeronautical and Space Sciences , vol. 61(1), 9-15, 2013.
Other Activities
The Japan Society for Aeronautical and Space Sciences (JSASS)
Future Plan
The goal of our research into space propulsion is to create new opportunities for the utilization and exploration of space. Transportation in space is vastly different from that on Earth. Spacecraft must carry propellant that is to be exhausted to generate a reaction force, and what missions may be possible are determined by the type of propulsion system employed. We believe that innovation in space propulsion systems leads to innovation across the whole of space activity research. Our recent major areas of interest are micro-propulsion for small spacecraft and electric propulsion using plasmas. Whilst mainly performing experimental research, we also employ numerical simulations to understand physical phenomena and provide support for the design of new devices.
Messages to Students
Any attractive research/project comes with a lot of difficulties. We believe the most important element for our activities is enthusiasm to challenge these difficulties, and we always welcome motivated students who enjoy addressing and settling a number of such problems.