Section 1 INTRODUCTION The objective of the Grumman study effort is to provide refined inputs for mechanical systems, structure and thermal control for Raytheon’s overall investigation of the Microwave Power Transmission System (MPTS). This system will be used to transmit, receive and control large amounts of power from space. Grumman’s efforts identified structural design options, the driver parameters for both weight and cost, and established requirements for the structural and flight operations systems. An orbiting electric power station has several major elements: the power source or converter, the electrical power distribution system and the microwave generator/ transmitting antenna. An antenna can be hypothesized that would be independent of the power source except for the mechanical control system interface. The purpose of Task 1, Preliminary Design, was to evaluate this mechanical interface. To achieve the depth needed to gain an understanding of accuracy and stability, a power source and spacecraft had to be selected. Because more data on physical characteristics were available on the Satellite Solar Power Station (SSPS), this power source/spacecraft was used in the preliminary assessment. Selection of the antenna structure required evaluation of 1) basic antenna geometry, 2) the impact of MW conversion thermal waste on structural material selection and feasible structural flatness, and 3) the mode of transportation and assembly. A broad matrix of antenna geometries, structural materials and transportation modes have been evaluated. Figure 1-1 summarizes this matrix of design options considered during the Task 1 Preliminary Design Phase. The three materials, aluminum, graphite/epoxy and Kevlar polyimide, were selected on the basis that they represent a broad range of strength, weight, cost and thermal characteristics. Aluminum represents a low cost, high weight option that would thermally limit the power level selected for the system. Graphite/epoxy represents a material with excellent thermal expansion characteristics, high strength and low weight. Kevlar polyimide would be low weight at modest cost with a resin that could withstand a high temperature environment.
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