THE STUDY ON STRUCTURE OF LARGE REFLECTOR FOR SPACE SOLAR POWER SYSTEMS (SSPS)

摘要

SSPS converts solar energy into microwave or laser beam in the geostationary orbit (GEO), and the microwave and laser beam are transmitted to the earth even in day or night and even in cloudy or rainy day. Therefore this system is expected as a means to solve energy and environment problems in the future. The microwave based SSPS has large reflector for gathering of solar light, solar panel and microwave power transmitter. They are large structure of km size. Now as a first step toward realizing SSPS, we study how to assemble structure of 100m size like reflector and panel for antenna and generator on orbit. The author made structure models of reflector in different styles of 100m size. These models are analyzed for structural properties (mass, stiffness, strength). Furthermore, these models are analyzed the relation between flatness of their models deformed by the disturbances and rate of gathering solar light. From the results of these analyses, the author tries to select the best model of reflector in the size of 100m for SSPS. Therefore, the purpose of this study is to determine proper structure and configuration of model of reflector for SSPS from these models. The model of reflector is composed of ten thousand segmented mirrors, main truss structure, and bus equipment. Each mass of mirrors, structure and bus is 1000kg. Each segment mirror is a film mirror of 1m×1m square. The structural properties of models were analyzed on finite element method (FEM) by treating mirrors and bus equipment as the point mass. Aluminum alloy is used as main structural material. Furthermore, the author used the data of distribution of illumination of a commercial film mirror which was measured flatness and analyzed in the case that the mirror is exposed to the sun. The author analyzed total distribution of illumination in reflector by superposing this data of one mirror. The deformation of models is caused by disturbances (orbital and attitude control, solar pressure, gravity gradient and atmospheric drag). From the results of these analyses the author made trade-off of these models and selected the best model of reflector in the point of stiffness (natural frequency), deformation, major principal stress, buckling stress, distribution of illumination, light collection efficiency and ratio of nonuniformity of illumination. The standard model of reflector is 100m×100m square. Performances of other models are evaluated by comparison with this standard model. This paper shows the result of trade-off in analyzed models and the best models the author selected.