Figure 2. SPS Requirements/Environments Table 1. Major Structural Components/Status machine-made beams ranges from near total reliance on machine capability to monitoring of critical parameters. Beam-to-beam joint design inspectability and repairability remain to be studied. At Rockwell, visibility on several of these issues has been achieved through the results of structural analyses in support of system studies of solid-state configurations. Structural analyses were performed to assess the structural feasibility of a hexagonal compression frame/tension cable array primary structure for the MPTS antenna. The orthotropic tension cable array provides support for the solid-state sandwich panels without obstruction of either the solar cell or microwave surface. Figure 3 illustrates the peak eclipse-induced thermal loads relative to the initial closed force cable pretension/frame compression loading. These loads are due to the thermal gradient between the tension cables and frame machine-made beam caps. Both elements are of graphite composite material (cl = 0.36 x 10'® m/m°C). The peak thermal loads are 1 to 3%. With aluminum, the percentage changes would be 20 to 40%. Figure 4 illustrates the two principal thermal sources causing hexagonal frame deflection and deviation from surface flatness. These sources are thermal gradients across the tri-beam structure due to shadowing by the sandwich panel array and temperature differentials between the discrete groups of X-bracing, denoted by solid and dashed lines. The peak thermal deflections of point H are shown parametrically for the antenna apertures shown and for tri-beams designed to the surface restrictions shown as the abscissa. It is noteworthy that the 12-cm deflection
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