geosynchronous Earth orbit. Once the structure is in GEO additional beam packages are transported and docked to the structure as required. The assemblers proceed to build outward from the center until the total 2520 cube support structure is complete. 1.2 Microwave Power Transmission System Studies (Reference 2) The Raytheon/Grumman Aerospace Companies, under contract to NASA-Lewis, has also derived a concept for the construction of the support structure for the microwave power station (Figure 2). The concept contains 69 structural modules which are 350 ft. square by 120 ft. deep. The total assembly measures 1 Km (3,270 ft.) in diameter and 120 ft. deep, excluding the gimbal mounting structure. Detailed space assembly techniques were not the prime consideration during the design of this structure. Figure 3 shows a detailed view of one of the Raytheon/Grumman 350 x 120 ft. structural elements which make up the 1 Km microwave antenna. The base structure is composed of 36 modules approximately 59 ft. square by 16 ft. deep. Each of these 36 module elements is ringed by a 115 ft. wall composed of cable supported beams. Figure 4 shows a cross section detail of a segment of the Raytheon/ Grumman microwave antenna structure. This design uses four basic beam sizes: 18 m (59 ft.) x 3 m (9 ft.); 35 m (115 ft.) x 3 m (9 ft.); 18 m (59 ft.) x 1 m (3 ft.); and 5 m (15 ft.) x 1 m (3 ft.). Each of the beam segment junctions are supported by tension cables that must be emplaced after the beams are assembled. This drawing shows both the support structure and waveguide array. 1.3 Design Differences The key antenna design differences between the Raytheon/Grumman and the Martin Marietta concepts are shown in Table I. The MMC has a study groundrule that all structural components be compatible with the Shuttle cargo bay while GAC assumed that the beams are assembled in space.
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