新東京大学大学院領域創成科学研究科
Success in Thrust Enhancement of Microwave Rocket

Abstract

A Microwave Rocket model was successfully lifted up by microwave power irradiated from a ground-based power source, Gyrotron. By using a repetitively pulsed microwave beam, a metallic model rocket of 126g weight was propelled for 1.2m without any propellant consumption.

Content

The group of Prof. Kimiya KOMURASAKI, the Graduate School of Frontier Science, the University of Tokyo conducted the Microwave Rocket launch experiment in collaboration with the Japan Atomic Energy Agency (JAEA) as a Collaborative Research using JAEA facilities. A high power microwave generator, Gyrotron, whose oscillation frequency and output power are 170GHz and 1MW, respectively, was used as a ground-based power source and a metallic rocket model of 126g weight was propelled by a repetitively pulsed microwave beam for 1.2m without any propellant consumption.
Conventional rockets, such as Japanese H-II rockets, gain thrust via combustion of loaded propellants; such as liquid hydrogen and liquid oxygen. These propellants' weight is approximately 90% of the launch weight, which results in their huge thrust requirements and prevents significant launch-cost reduction. On the other hand, Microwave Rocket does not require combustion reactions and loading propellants, so that the launch-cost is expected to be reduced by 1/100 by downsizing and weight saving of a launcher and Microwave Rocket is recognized as one of the promising future space transportation systems which can contribute to space infrastructure constructions, such as Space Solar Power Satellite Systems or Lunar Bases.
Thrust is generated through the explosive expansion of the atmospheric air by microwave energy deposition at the focus of the microwave beam, which is similar to that of a peal of thunder: A pulsed microwave beam sent from the ground is focused inside the rocket and the air is heated up to 10,000 degrees Celsius very rapidly. Steady thrust can be generated by repetitively pulsed microwave irradiations.
The development of Gyrotron is done at the Naka Fusion Institute, Japan Atomic Energy Agency, for the plasma heating system of the International Thermonuclear Experimental Reactor (ITER). Because the Gyrotron was improved to steadily generate repetitive pulse microwave beam, the presented experiment was conducted.
In our experiment in 2003, a plastic rocket model weighing 9.5g was launched at 2m altitude by a single-pulse microwave beam (930kW, 0.4msec.) In this experiment, thrust was generated continuously for 1.2m vertical distance using a repetitively pulsed microwave beam (power: 600kW, pulse duration: 1msec, repetition frequency: 100Hz) and the thrust was enough to lift up a metallic rocket weighing 126g which was one order of magnitude heavier than the previous model.
Our future work is to launch a heavier rocket to a higher altitude by improving Gyrotron and optical transmission systems and by adding an intake, and eventually, to launch 100kg payload into earth orbits.
In addition, a long-range wireless power transmission was demonstrated in this series of experiments. To achieve a long-range microwave power transmission, the beam diameter was widen using a set of parabolic mirrors on the transmitter side and narrowed on the rocket side as well. Results showed that thrust was continuously generated in the range of 5m or longer. This technology implies the possibility of high-power wireless transmission for future applications including rocket propulsion.

Release schedule

Space Transportation Symposium http://www.isas.ac.jp/j/researchers/symp/2010/0114_yusou.shtml
(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(ISAS/JAXA), Sagamihara City, Kanagawa Pref., Jan. 14-15, 2010. The presentation is planned in the morning on Friday 15th.)

Contact

Graduate School of Frontier Science, the University of Tokyo. Prof. Kimiya Komurasaki
Tel/FAX : +81-3-5841-6607 (Hongo campus), +81-4-7136-3829 (Kashiwa campus)
E-mail address : komurasaki@k.u-tokyo.ac.jp

Glossary

Microwave
Electromagnetic waves used in kitchen microwaves, cell phones, etc.
Launch-cost
Cost to launch payload into earth orbit. \800,000 per kilogram to low-earth orbit (LEO) using H-IIA rocket.
Space Solar Power Satellite
A satellite in which solar energy is converted to electric energy in space and is transported to a receiver on the ground by a microwave or laser beam. The power generation capacity is envisioned to 1GW per one satellite whose solar panel size is of approximately a kilometer square.
Wireless Power Transmission
Technology to transmit power without electric wires, but with electromagnetic induction, electromagnetic irradiation or laser.
Graphics

Pictures, movie materials and supporting viewgraphs can be downloaded from the following web site.
URL : http://www.kml.k.u-tokyo.ac.jp/press/pr1001.htm

Figure
Figure : A picture of the vertical launch of the Microwave Rocket. One frame taken by a fast framing camera.

 

 

 

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