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/cm2 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/m2 and a specific impulse of about 5000-6000 seconds at the ion beam energy density of 4 kJ/cm2 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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Main-lobe energy transmission using an optical phased array is proposed. Effects of spatial and temporal coherence of rectangular-symmetric laser arrays on energy transmission performance are evaluated in terms of the main-lobe beam quality factor and the main-lobe energy transmission efficiency. As a result, the efficiency is found independent of the number of laser elements and their spectral broadening, and sensitive to the aperture fill factor. The main-lobe beam quality factor remains constant for any cases.

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A systematic and efficient procedure for optical scan along the geostationary orbit (GEO) has been designed to determine the numerous orbits passing near the GEO. The scan corresponds to alternate monitoring of two points on the GEO. Therefore, follow-up observation enables orbits with high orbital inclinations to be captured despite large errors in measurement. The validity of the procedure was confirmed through experimental observation using a 35-cm optical telescope located at the Kashima Space Research Center.

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The surrface accuracy of a rectangular membrane element subjected to anisotropic tension in a faceted reflector surface is investigated. The rectangular membrane element is assumed to be placed at an arbitrary place on the reflector surface with an arbitrary rotation angle between the side of the membrane and the direction of the principal curvature of the reflector surface. Rectangular membranes with two kinds of boundaries are considered. One is a coincident-edge membrane whose boundary coincides with the approximate parabolic surface at the local point where the membrane is placed. The other membrane is a coincident-optimum-edge membrane, which is obtained by minimizing the rms error using normal translation of the coincident-edge membrane. The deflection and the surface error of the membrane are calculated based on an analytical solution of the linear membrane equation. In a certain range of parameters, it is found that the appropriate tension ratio reduces the surface error of a membrane element as compared with isotropic tension. The surface error of a slender membrane becomes lower if the longer side of the membrane is loaded with higher tension. The more slender the membrane, the smaller the surface error. The minimum surface error is obtained when the longer side is placed parallel to the direction of the larger principal curvature at the location and the longer side is loaded with higher tension. The ratio of the surface error of a coincident-optimum-edge to that of a coincident-edge membrane is approximately 0.4 - 0.5 and depends only on the ratio of the aspect ratio of the membrane and the tension ratio parameter.

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