In this paper, we showed the performance of a propulsion system in space by ablation plasma produced by pulsed ion beam and its controllability. First, the fundamental study of flyer acceleration with ablation plasma produced by irradiation of an intense pulse ion beam was explained numerically. Here, we used a one-dimensional hydrodynamic model based on the stopping power taking the interaction between the flyer material and ion beam into account. Using this numerical model, a maximum flyer velocity of about 8 km/s and ablation pressure of 20 GPa could be obtained at the ion beam energy density of 4 kJ/cm 2 and the pulse width of an incident ion beam of 60 ns. Moreover, our numerical results agreed well with experimental ones. From these results, we could estimate performance of the space propulsion system with ablation plasma produced by pulsed ion beam which is an impulse bit of 2000 Ns/m 2 and a specific impulse of about 5000-6000 seconds at the ion beam energy density of 4 kJ/cm 2 and the pulse width of an incident ion beam of 60 ns. In addition, this paper also discussed the controllability of impulse bit, and specific impulse and we finally found that changing ion beam acceleration voltage, energy density, power density, and the duration of ion beam irradiation could control both performances. Furthermore, we found that the important factors are to control the acceleration voltage and pulse width in order to improve the space propulsion performance of this system.

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This paper presents the hydrodynamic efficiency of ablation plasma produced by a pulsed ion beam, as obtained on the basis of the ion beam–target interaction concept. We used a one-dimensional hydrodynamic model to explain the ablation acceleration behavior. Hydrodynamic variables are evaluated in terms of ablation velocity, conversion efficiency and ablation efficiency. We obtained 18% value for the energy conversion efficiency, while an ablation efficiency of about 70% is achieved at an ion-beam energy density of 60J cm$^{-2}$ (beam power density of $\approx$1 GW cm$^{-2}$). A thrust producing capability is also investigated.

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This paper investigates the acceleration performance of a disk-shaped magnetohydrodynamics (MHD) accelerator. Quasi-1-dimensional (Q1D) numerical simulation employing the MacCormack scheme was developed. For the longer channel length of 0.9 m, thermal loss was estimated at over 60% and effective acceleration could not be achieved owing to large heat loss and large friction loss. For shorter channel lengths, thermal loss can be reduced below 20% owing to the smaller heat and the friction losses. However, with too short a channel length, accelerator performance was decreased by the MHD compression due to excessive Faraday current density. The effect of ratio of cross sectional area on performance was also studied. For a larger area ratio, the gas can be accelerated smoothly throughout the MHD channel. However, for the excessive expansion case of a sevenfold channel, gas velocity near the exit decreased due to transition to a ''generator mode''. For the best acceleration performance, the design channel length should be as short as possible preventing compression at the channel inlet. The area ratio should be large enough to prevent the compression but not too large, to prevent transition to a ''generator mode''.