J. C. Jones, L. E. Livingston & J. D. Bradley Spacecraft Design Division IV-A-4 CONFIGURATIONS A number of SPS configurations have been studied and a variety of possible arrangements are illustrated in Figures IV-A-4-1 through 13. These figures illustrate the major components of the SPS, which are the solar array, the antenna, and the rigidizing structure. During configuration design, consideration was given to the following basic requirements: (1) Minimize external disturbing forces, primarily gravity gradient forces, by providing an inertially balanced structure (i.e., for solar orientation Ix = ly = Iz; for perpendicular to the orbit plane (P.O.P.) orientation Ix = Iz). For a discussion of external disturbing forces see Section IV-B-4. (2) Locate the antenna or antennas so that pointing requirements are most readily satisfied and forces acting on the antenna/antennas are symmetrical with respect to the SDS center of mass. (3) Select a geometric shape and arrangement which can be fabricated and assembled with a minimum amount of complexity. The configuration should be such to allow efficient fabrication in space by the use of automatic machinery. (4) For a discussion of the primary and secondary structure of large satellites in orbit see Section IV-B-3. Figure IV-A-4-1: Configuration 76B-2 illustrates an arrangement which is counterweighted to achieve equal mass moments of inertia about two axes (Ix = Iz). The solar array is oriented perpendicular to the orbit plane. The structure for this configuration consists of three major compression column members stabilized with cables. This configuration has two antennas, each beaming one half the power towards its own separate ground based rectenna. Two antennas are required for a symmetrical arrangement to avoid unbalanced torques. It appears that the shape of this configuration will require a more complex technique for the fabrication and assembly than some of the other geometric shapes, namely rectangular or square. Figure IV-A-4-2 (Config. 76D-1): This configuration is similar to configuration 76B-2 except that the array is solar oriented and is configured to provide equal mass moments of inertia about the three primary axes, using counterweights. Solar orientation allows a 4% smaller area for the same power output. Figure IV-A-4-3 & 4 (Config. 76J): In this configuration the array is oriented perpendicular to the orbit plane. This orientation allows a simpler antenna axes arrangement. The structural concept is similar to the previous configurations (76B-2 and 76D-1) except this
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