A high specific impulse ion thruster (HiIsp-IT) operated at a voltage of over 10 kV has been studied and the problems of direct ion impingement on the accelerating grid and of production and impingement of charge-exchange ions have been considered. In order to investigate these problems and to facilitate the grid systems design, a three-dimensional particle simulation code that employs an energy compensation method, a simplified pre-sheath definition method, a region sharing method was developed. This code also simulates the production and subsequent motion of charge-exchange ions. Using this code, results obtained quickly using a personal computer are shown to be in good agreement with experimental data associated with: the crossover impingement under low-beam-current condition and the star-shaped pattern of ion beam cross section as it passes through the accelerating grid. It argued that this code is a useful tool for rapid preliminary analysis and design of HiIsp-IT grid systems.

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This paper presents the membrane construction and the evaluation of the structural characteristics of the rigidizable membrane for space inflatable structures. The single-layer triaxial woven fabric composite is proposed to the rigidizable membrane because of its quasi-isotropic characteristics in just one layer. To maintain the dimensional stability of a single rigidizing layer, a triaxial woven fabric composite with low fabric construction was developed. We compare the structural characteristics of inflatable tubes constructed with the proposed membrane and an existing membrane using biaxial woven fabric composite. The inflatable structure that uses the proposed triaxial woven fabric is lightweight and offers excellent foldability and durability. Rigidizing test using a 2.1 m diameter inflatable torus was conducted to confirm the complete rigidization of the proposed rigidizable membrane.

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This paper describes the rigidization characteristics of a rigidizable membrane used for the inflatable structures with photoinitiated composites. The test pieces are obtained from the photoinitiated rigidizing prepreg irradiated by the xenon lamp. The DSC (differential scanning calorimetry) test, the residual styrene measuring, the sectional view and tensile modulus measuring are conducted to evaluate the rigidization characteristics. The acceptable rigidization is confirmed from these measurements. Feasibility of the rigidizing membrane used for the inflatable structures is also clarified.

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A new control method for the orbital transfer of the Space Solar Power Systems (SSPS) by the solar electric propulsion is presented. In this method, SSPS is launched from a place near the equator such as the Christmas Island, both yaw and pitch angles of the thrust direction are fixed to zeros, and the thrust-off periods are assigned optimally near the perigee in the final stage of the transfer. This method, especially for large spacecrafts such as SSPS, has the advantage that the heavy momentum wheel for the thrust vector control is not necessary.

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An extendible nozzle and a dual-bell nozzle are considered to be feasible devices to improve performance of booster engines for near future reusable launch vehicles. Hot firing tests were conducted at a high altitude test stand, using four kinds of nozzles as follows: a standard bell nozzle, a fixed step nozzle simulating the transient nozzle position during nozzle extension, a dual-bell nozzle and a movable extendible nozzle. Measured nozzle performance, pressure distribution and heat transfer characteristics were compared with those of CFD analysis. The dual-bell nozzle performance was shown to be lower than those of the standard bell nozzle and the step nozzle. Reverse flow of combustion gas through the gap between fixed nozzle and movable extendible nozzle was not observed during nozzle extension.

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This paper newly presents what the optimal guidance strategy is for the vehicles, which fly along the so-called aerodynamic ascent path. As commonly utilized, the paper first shows the optimization results via the DCNLP method, while the paper secondly shows the other results via the SQP, direct optimization method. The latter is efficiently and easily carried out taking the advantage of the steering angle expressed in a certain orthogonal functions. The primary result of the paper is the analytical description of the steering law, that relates to the optimization discussion. It is clearly concluded that a conventional linear tangent law is applicable only to non-lift vehicles. The conclusion, at the same time, indicates that the optimal guidance should take trigonometric functions in addition to those in the conventional linear tangent law. The results presented in the paper further extend the optimization process to the guidance scheme with numerical demonstrations. Since the linearized translation motion fits better for the analytical model, the results of the paper successfully could show the practical validity of it. The examples include the cases with the vehicle parameters varied from nominal and the sensitivity to those is also examined.

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