This research proposes a structural identification method with variable geometric parameters extending the concept of self-identification. The method is formulated by using the change of eigenvalues and eigenvectors according to the change of variable geometric parameters. The method is then numerically examined through the identification of the stiffness matrix of a two-dimensional variable geometry truss. As a result, the stiffness matrix is identified with a set of linearly independent eigenvectors corresponding to the one vibration mode changed by one variable length member of the truss. Also, the results show that the identification performance using only one variable length member is relatively equal to that using three variable stiffness members without geometric change when multiple vibration modes data are available. Further, it is shown that the identification error with the variable length member depends on the vibration mode and the stiffness ratio between the stiffness of the variable length member and that of the other members to be identified. Finally, the increment of degree-of-freedom of the identified matrix to the identification error is investigated.

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The influence of exhausted beam ions from ion thrusters on Earth's environment and communication was analyzed by the detailed modeling of the exhausted ions' and electrons' motion and the energy exchange process between the exhausted ions and the circumferential particles. The analytical results showed that the density distribution of plasma components near the earth will change locally by the energy input of exhausted ions trapped by the geomagnetic field if the large scale operation of ion thrusters is performed, but its influence on earth's environment will be small compared with that by the natural phenomena such a magnetic storm. However, the influence on GPS communication will be large and the electrical charge of spacecraft will be progressed.

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Public outreach activity is one of the most important issues in space development. Improvement in Internet and information technologies enables us to consider effective outreach strategy using digital contents. NICT made experiments on Email distribution of Earth images captured by Micro-OLIVe experiments as a trial of public outreach using digital contents. In this paper, outline of the experiment is introduced. The analysis on the distribution process of participants and the results of a questionnaire survey are also discussed to consider how we improve future digital contents of space activities.

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An arc-heater using a zirconium cathode was developed as an atomic-oxygen generator. With pre-mixed argon-oxygen injection, stable discharge was maintained for more than three hours, and the cathode erosion rate was as low as 1.7x10^-5 g/s. The plume temperature and velocity distributions were measured and chemical composition and total specific enthalpy was evaluated by laser absorption spectroscopy. As a result, in the center area of the plume, the degree of dissociation in oxygen was found almost 100% with the total specific enthalpy of 4.5±0.1 MJ/kg.

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A new sensitivity analysis method for membrane wrinkling is presented. The wrinkling phenomenon is modeled by the tension filed theory with a projection technique. In the technique, the total strain energy in wrinkled membranes is effectively decomposed into elastic energy and zero-strain energy parts using a projection matrix. The zero-strain energy part depends on only the zero-energy deformation caused by wrinkling, and is utilized for a quantifier of degree of membrane wrinkling at a material point. The wrinkle quantity of the discretized membrane element is obtained by the integral of the zero-strain energy over each element. The total wrinkle quantity of whole membrane is also obtained by the summation of the elemental wrinkle quantities. The sensitivity of the total wrinkle quantity is derived with respect to displacement vector and also design parameter. The latter is given by the semi-analytical differentiation method (SDM). The proposed sensitivity analysis method is applied to a shape design problem for wrinkle reduction of a square membrane to demonstrate its effectiveness.

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This paper presents a synthetic method that is based on both the algorithm of the geometry nonlinear feedback and nonlinear system optimal control of hierarchical differential feedback regulation. This method enables us to solve optimal feedback control problems without solving the Riccati Equations or adjoint vectors. Also, the method takes into consideration the avoidance of conjugate points, which is a important aspect of research in optimal control of nonlinear system. The present method is applied to two examples, one is a nonlinear attitude maneuver of spacecraft and the other is an airship optimal feedback tracking control. These applications have been studied numerically in order to show the performance of the present method applied to nonlinear optimal control for aerospace application.

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