Introduction of Research

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Research on propulsion system for space debris removal

Overview of research

As the last step in the debris removal sequence, the debris should be deorbited using some kind of propulsion system. And given the preference for using a smaller spacecraft to remove large debris objects, a highly efficient deorbit propulsion system is required.

One prospective candidate for debris removal is “electric propulsion”—a popular means of space propulsion in recent decades. Electric propulsion generates thrust using electric or electromagnetic force. Although the thrust of electric propulsion is generally small compared with that of chemical propulsion, its exhaust velocity is much higher. Thus, electric propulsion can ultimately provide larger impulse at lower propellant consumption as the operation time becomes longer. In this research, we studied what kind of electric propulsion is best suited for the debris removal system. We also conducted experiments and analyses on Hall effect thrusters toward achieving our targets, such as a smaller system, longer service life, and lower cost. Fig. 1 shows a Hall effect thruster experiment conducted in a space chamber.

The electrodynamic tether (EDT) is another candidate for future debris removal systems. The EDT is a unique propulsion system that utilizes the interaction between the geomagnetic field and electric current flowing through the long conductive tether, and thus needs no propellant to generate thrust (Fig. 2). This feature allows us to make a simple propulsion system, and simplicity is important for realizing low-cost debris removal systems. We are conducting research on tethers, electron emitters and other technologies required for the EDT system, by utilizing the experience gained from the in-orbit experiment (called “KITE”) conducted on the HTV-6 in 2017.

Fig. 1. Hall effect thruster experiment
Fig. 2. Image of debris deorbit using EDT

Research achievements

Publications
  • M. Chono, N. Yamamoto, K. Kubota, G. Fujii, K. Kinefuchi, “Development of 200 W Class Hall thruster system,” Proceedings of 61st Space Sciences and Technology Conference, JSASS-2017-4538, 2017 (in Japanese).
  • S. Kawamoto, Y. Ohkawa, T. Okumura, K. Iki, H. Okamoto, “Performance of Electrodynamic Tether System for Debris Deorbiting: Re-evaluation Based on the Results of KITE Experiments,” Proceedings of 69th International Astronautical Congress, IAC-18-A6.6.5, 2018.
  • Y. Ohkawa, K. Iki, T. Okumura, S. Kawamoto, Y. Horikawa, K. Inoue, Y. Kobayashi, T. Uchiyama, T. Kasai, “A Quick Review of an Electrodynamic Tether Experiment on the H-II Transfer Vehicle,” Proceedings of 35th International Electric Propulsion Conference, IEPC-2017-359, 2017.
  • T. Okumura, Y. Ohkawa, K. Koga, S. Kawakita, S. Kawamoto, Y. Kobayashi, T. Kasai, “Charging of the H-II Transfer Vehicle at Rendezvous and Docking Phase,” Journal of Spacecraft and Rockets, 2018, DOI :10.2514/1.A34068.