crane, a movable manipulator crane with a manned end-effector and teleoperator arms. The manipulator is described in some detail, and reference is made to NASA's remote manipulator simulation facility. In addition, Ref. E5 forecasts advances in the areas of robots and teleoperators. Ref. E4 is the most definitive document on orbital assembly even though it considers only the support structure. It reports on a Martin Marietta study which was based on the Raytheon/Grumman design as a baseline. Ref. E4 states that "we found that the structure was not designed for easy assembly in orbit and not totally compatible with the presently defined space transportation system." The reference then describes a redesign which would utilize such techniques as thermite-type fusion welding for fastening, triangular trusses, and telescoping tubular tension members. An automated mobile assembler was also conceived for the highly repetitious operations, and it is reported that this would minimize the number of manned, direct activities. With two mobile assemblers, it was estimated that it would take nine months at 24 hours per day to complete a support structure. It is not clear that such a rapid construction schedule is desirable. Ordinarily large-scale terrestrial power plants require several years for construction. 6. Energy Conversion While the photovoltaic method has been given primary consideration as the energy conversion method for satellite power systems, seven approaches have been studied, viz: • Solar-Photovoltaic • Solar-Thermal, direct radiation cooled • Solar-Brayton, actively cooled • Solar-Brayton, closed cycle • Cascaded-Solar Thermionic/Brayton cycle • Nuclear Thermionic • Nuclear Brayton Since these approaches involve a wide range of conversion techniques, several technological areas are of interest. These include solar cell/array technology, thermionic converters, Brayton turbine technology, and nuclear power
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