INVESTIGATION OF INTERNAL MECHANISM OF ELECTRIC THRUSTERS AND THEIR PERFORMANCE ANALYSIS

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In electric propulsion, there are several kinds of electric thrusters, such as electrostatic type, electromagnetic type and electrothermal type. The drawbacks common to the thrusters are ; 1)low energy conversion efficiency, 2)not demonstrated endurability for long operation, and 3)not obtained scaling laws determining thruster performance. To overcome these drawbacks, it is necessary to investigate physical phenomena in thrusters, Such-as ionization and dissociation processes, plasma acceleration mechanism, and heat and energy transport processes, not only by theoretical analysis but also by experimental one.For this purpose, this study has been continued for three years since 1992. It was a co-operative work of researchers and engineers of universities and research institutes, and had joint-meetings for several times, exchanging informations and discussing research contents and current topics.As the resuit, it was concluded that ; 1) in ion thrusters, numerical code has been constructed, which can be used to estimate thruster performance for given geometrical design and operating parameters, 2) as for arcjet thrusters, arc dischrage behaviors were examined and clarified both by experimental observations and by numerical calculations, 3) MPD flow analyzes have been conducted to obtain a further understanding of the relations between plasma flow and arc discharge, indicating that non-equilibrium flow plays an important role on inoization and plasma acceleration processes.