in that part of the antenna. Further work will be required on a control system for the switchgear and on the degree and location of power supply regulation. 7. Structure A compression hoop structural concept was developed in an effort to minimize structural weight. Primary structure consists of four concentric polygons of 6, 12, 18, and 24 sides joined by tension cables (fig. IV-14). The polygon sides are rectangular frames 65 by 130 m. A secondary structural matrix adapts the antenna subarrays to the primary structure such that each subarray is attached at three points. Thermal distortion should be minimized in view of the radial symmetry of the structure and the power density. Figure IV-14.- Antenna primary structure. 8. Rotary Joint The rotary joint provides a structural connection between the SECS and the transmitting antenna, a means of transferring electrical energy from the SECS to the transmitting antenna, and a drive system to rotate the joint continuously about one axis and roughly 1°, oscillating daily, about a second axis. Several approaches were identified and evaluated in general terms, and a promising concept was selected for more detailed examination. This concept, illustrated in figure IV-15, consists of a ball joint approximately 25 ft in diameter. The spherical contact surface is split into two halves, and supports structural loads and transfers electrical energy by means of sliding brushes.
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