Configuration The tension web-compression frame antenna structure concept consists of three major elements: (1) the tension web to which the dc-to-RF conversion and transmission hardware are attached; (2) a cantenary rope system which is attached to the perimeter of the tension web, and (3) a hexagonal compression frame. The tension web resists the lateral pressure loading described in Section 1.3. This loading is transmitted to the vertices of the hexagonal compression frame via the catenary rope system. The compression frame members are loaded in pure compression and can be analyzed as columns. Three of the six catenary-to-compression-frame vertice attachments are fixed. The other three attachments at every other intersection have lateral adjustment jacks. The three fixed attachments describe a plane perpendicular to the desired boresight and the adjustable attachments maintain the tension web as a flat surface. All six catenary rope/compression frame attachments have in-plane tensioning devices which maintain the tension web flat within the design limits described in Section 1.2. Antenna elevation (north-south) adjustments are accomplished by gimbals in the trunnion structure which attaches the antenna to the rotary joint. Azimuth adjustments are made by the rotary joint. Design Requirements The basic design requirements for the compression frame-tension web concept are as follows: • 1-km diameter surface (or equivalent) • Surface flatness « +0.75 cm under environmentally and operationally induced loads and temperatures • Optimize for lightweight • Compatible with on-orbit fabrication and assembly • Compatible with operational equipment • Service life: >30 years The surface flatness requirement of +0.75 cm is the allowable out-of- plane tolerance which would cause less than a 1-percent loss in microwave beam efficiency. Compatibility with on-orbit fabrication and assembly dictates that the construction equipment utilized for the solar array structure would have the capability to construct the antenna structure (i.e., no antennapeculiar construction equipment would be necessary). Design Environment The design environment selected as a precursor to the structural analysis effort is a function of physical loading perpendicular to the tension web surface only. The source and magnitude of these loads for two extreme conditions along with the selected design condition of 40.8 newtons (9.18 pounds) are indicated in Figure 2.1-17. The variation in gravity gradient force is
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