• The optimized graphite/epoxy triangular hat longeron design is shown in Fig. 2-19 for a 450°K environment. The 20 mil thick material is composed of ten layers of 2-mil graphite fibers. • The range of thermally induced deflections and local slope are presented in Fig. 2-20. Variations in slope with variations in orbital position exceeds 1 arc-min for an aluminum structure. The slope variations from a mean or average deformity is well within limits for graphite/epoxy. Assessment of secondary structure deformation shows that the worst deflections occur at the tips of the antenna, with maximum deflections not to exceed 10. 5 mm over any one 18 x 18m subarray. 2.2.4 Assembly 2.2.4.1 Detail Parts Assembly Sensitivity analysis of various levels of ground prefabrication compared to corresponding levels of orbital assembly was performed to determine the most cost effective approach to antenna structural assembly. Figure 2-21 outlines the three approaches which span the possible options for detail part fabrication. Case I assumes manufacture of articulated lattice tri-beams on the ground. These designs can be compressed to 1/30 of its deployed length for convenient packaging in the Orbiter. Case II assumes that the ground fabricates the longerons and intercostal elements of the tri-beam and that assembly of the beam is performed in a space station. Case HI assumes ground personnel prepares flat stock with appropriate coatings for installation into an automatic manufacturing module in space. Figure 2-22 summarizes the pertinent characteristics of these approaches. Although the articulated lattice beam is an efficient packaging arrangement, the packaging density in the Orbiter is extremely poor. As much as 440 Shuttle flights would be required for delivery of the 470 Klb (213 x 10$ Kg) antenna structure. Transport of beam elements provides an improved packaging density, depending upon the cross-section selected. The number of crew members, however, required to fabricate the finished beam in space in a reasonable time would require deployment of as many as 24 12-man space stations. In-orbit automatic manufacture of the structural members appear to provide the clearest road to a low cost detail parts assembly method.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==