REFERENCE SYSTEM CHARACTERIZATION AND COST OVERVIEW Robert 0. Pi land NASA/Johnson Space Center - Houston, Texas 77058 Studies conducted during the Solar Power Satellite Concept Evaluation Program have considered a variety of system design approaches. Each of these design approaches has advantages and disadvantages. Considerable additional work would be required before a final or preferred system can be defined. For the immediate purposes of the evaluation program, however, a reference system has been defined to provide a basis for assessing alternate technical approaches, environmental factors and to serve as a basis for preliminary cost studies. Reference System Description A description of the system is presented in reference 1. Major elements of the system are depicted in figure 1. They include a cargo launch vehicle, a low earth orbit staging base, a cargo orbital transfer vehicle, a geosynchronous construction base, and the energy system consisting of the satellite and a ground receiving station or rectenna. Additional program elements include personnel launch and orbital transfer vehicles, launch and recovery facilities, and industrial production facilities. More detailed characteristics of the satellite and rectenna are presented in figure 2. The satellite consists of the solar array and the microwave transmitting antenna. The solar array includes a graphite composite truss structure and a blanket of silicon solar cells. An alternate reference option involves the use of gallium aluminum arsenide solar cells in a trough-like structure. A yoke arrangement provides the interface between the solar array and the transmitting antenna. Its mechanization allows the solar array to track the sun while the antenna tracks the rectenna at a fixed position on the earth. The antenna consists of a primary and a secondary structure, on which are mounted approximately 7000, 10 meter by 10 meter, subarrays. The subarrays include 100,000 DC-RF power amplifiers and wave guides. The rectenna consists of a series of panels, oriented toward the satellite, consisting of an open-screen ground plane, on which are mounted a large number of half-wave dipole antennas. The power, collected by the antennas, is fed to Schottky barrier diodes for conversion to D.C. power. The dimensions of the satellite and rectenna are shown in the figure. The satellite weighs 51,000 metric tons. Cost Overview The detailed definitions of the satellite, rectenna and other program elements have provided basic information necessary for preliminary cost estimates. A number of estimates have been developed during the Concept Evaluation Program; however, the concept has not matured sufficiently to establish an official estimate. The estimates presented, however, are illustrative, and have been found to be useful in establishing the relative importance of the various program elements from a cost standpoint.
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