Kiyoshi Yatsui

Efficiency of Ablation by Pulsed Ion Beam and Propulsion Performance

This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam based on the ion bea m and solid fuel target interaction. We used a one -dimensional hydrodynamic model, which mostly focused on an ion beam energy deposition phenomena and analyze it as a rocketlike model to explain and examine hydrodynamic variables. These variables were esti mated by the concept of ablation driven implosion in terms of ablated mass fraction, ratio of target velocity, and ablation velocity and thrust efficiency. Hydrodynamic efficiency of 17.5% by means of thrust conversion efficiency was achieved. The results show maximum energy efficiency of the ablation process (ablation efficiency) of about 70% meaning the efficiency with which pulsed ion beam energy E ionbeam is converted into exhaust kinetic energy in the solid fuel material. Moreover, propulsion performanc e with specific impulse of 3600 s was briefly reviewed. An effect of an ablation depth to hydrodynamic efficiency was also tested.

Application of Ablation Acceleration by Pulsed Ion Beam to Space Propulsion

Our recent advanced research into ablation plasma acceleration produced by the irradiation of an intense pulsed ion beam has focused on ablation propulsion as a possible application to interplanetary missions. For this purpose, a one-dimensional hydrodynamic model, based on the interaction between target material and ion beam irradiation has been numerically analyzed the fundamental study of flyer acceleration in both flyer velocity and ablation plasma pressure. The results were in fairly good agreement with previous experimental data with a maximum flyer velocity of 8 km/s and maximum ablation pressure of about 80 GPa instantly reached at the ion beam energy density is 4 kJ/cm. From these results, two propulsion performance indicators namely thrust of 2000 N and specific impulse of 5000 seconds are estimated for space propulsion respectively. Here, we obtained energy transfer efficiency about 10%. In addition, this paper presents the factors effect these indicators and we have found that changing acceleration voltage of ion beam, energy density, power, and the duration of ion beam irradiation can control both performances. Total energy density affects specific impulse whereas beam power influences thrust and flyer acceleration. Furthermore, the latest results confirm that controlling acceleration voltage relates directly not only to system capability but also economy.