Ryotaro Kaneko
(University of Tokyo, Japan)

A two-dimensional hybrid plasma model of a magnetic-layer type Hall thruster has been developed to predict channel wall erosion due to accelerated ions, and the computed erosion rate has been compared with experimental results. In this model quasi-neutrality is assumed and ions are treated as particles and electrons as fluid. Moreover, electron mobility and diffusion coefficient are presented in a tensor representation in the diffusion equation, since the values depend on directions of magnetic field lines. In order to solve pre-sheath electric field, Dirichlet potential condition was applied to the edge of sheath where ions enter the sheath at Bohm velocity. Resulting radial electric fields accelerate ions to the wall in the discharge channel. In a near-wall region, electron temperature must be decreased because of interference with the wall and the effect of ionization cannot be neglected in the diffusion equation. Therefore, influence of ionization at a near wall region on the electric field is discussed.

Tomohito Enoki
(Nagoya University, Japan)

An electrodeless thruster with radio frequency wave is developed and its operation characteristics are experimentally investigated. Propellant gas is fed through four radial branch tubes made of Pyrex glass, in which it is ionized through inductive coupling. The ICP plasma is introduced to a central tube also made of Pyrex glass. The AC currents supplied to the four coils around the branch tubes are set so that rotating magnetic field (RMF) is produced in the central tube. Electrons are expected to be frozen along the magnetic lines of force to yield azimuthal current. A steady-state magnetic field is superimposed to produce Lorentz force to accelerate the propellant plasma. So far the aforementioned plasma production was experimentally confirmed, thereby conducting further operation experiments.

Akeru Takagi
(Shizuoka University, Japan)

Currently, various new space propulsion systems without propellant are proposed, studied and developed to practical use. Electrodynamic tether (EDT) is one of the most expected systems among them. EDT system generates thrust by using the interaction between electric current flow in a conductive tether and the geomagnetic field. To flow the current in the tether, the tether system has to collect and emit electrons from and to the plasma on the orbit. Orbital Motion Limit theory (OML theory) is proposed as a collection theory of charged particles including electrons by the tether, but it is not proven that this theory is able to apply in orbital environment because this theory can only be applied in the isotropic and static plasma. To verify the OML theory in space, a charged particles collection experiment of bare electrodynamic tether was performed at the end of August 2010 by using a sounding rocket. This study shows the brief overview of the experimental results and discusses the applicability of OML theory in the orbital environment by comparing the experimental results with the estimated values by OML theory and the numerical simulation by PIC method.

Takanori Yoshimura
(Shizuoka University, Japan)

Recently, development of Micro-Satellite becomes active for academic education and commercial use, and the high efficiency propulsion system has been requested for boosting Micro-Satellite. An electrodynamic tether (EDT) system has been expected to use for deboost of space debris and orbital keeping of satellites, because the EDT system can be propelled without propellant and high efficiency. The EDT is made of an electroconductive wire, that can be propelled by using the Lorentz force generated by the interaction between the tether current and the geomagnetic field. If we use a bare tether as collector of electrons, the collection efficiency becomes better than that using a conventional spherical metal collector or hollow cathode. In this study, one year operation of Micro-Satellite using bare tether was assumed, and the analysis was done for orbital keeping and deboosting capability of Micro-Satellite. Also, the analysis of attitude dynamics of Micro-Satellite during the operation time was performed, and the attitude control method of Micro-Satellite was discussed.