3.2.5 Antenna Weight and Mass Properties Weight of the structural installation for the SSPS microwave antenna evolved from considerations and analysis of the effect of weight on antenna size, materials and coatings, type of construction, manufacturing tolerances, deployment and space assembly, carrier system integration, SSPS life requirements in space environment, and thermal design requirements. The assumptions, weight drivers, weight trades and the resulting detail weight estimate for the antenna structure is included in the following discussion of study results. 3.2.5.1 Antenna Structure Weight Weight of the antenna structure itemized in Fig. 3.2-16 is 410920 kg (904032 lb). The assumptions made to estimate weight are: • Antenna diameter: 1 Km • Material: Graphite/epoxy with thermal coatings (weight of graphite/poly imide is same as for graphite/epoxy) • Primary Structure: Rectangular grid beams at 108 meter intervals. The structure is built up from structural beams 18 meters long, each of which is constructed from three longitudinal members 18 meters long braced at 3 meter intervals. The height of the primary structure is 35 meters • The secondary structure is built up from 18 meter beams braced at three meter intervals. The secondary structure height is 5 meters and forms the grid for antenna electronic equipment support and spans across the primary structure spacing of 108 meters. • Weight penalties for the power distribution bus are not included. 3.5.2. Alternate Materials and Structural Shape Study Weight study results considering two types of structural shapes (tubular and triangular hat sections) and two materials (2024 T-6 Aluminum and graphite/epoxy) show that graphite/ epoxy is 41% lighter than aluminum for a tubular section and 21% lighter for the triangular hat section. The triangular hat section is 40% heavier than the tubular section (in graphite/ epoxy) (Fig. 3.2-17 and 3.2-18). 3.2 .5.3 Weight Parametrics and Drivers • Loads - The primary antenna loads are introduced into the antenna by the control actuators which must overcome the slip ring force. Gravity gradient, atmospheric, and magnetic forces are small when compared to the actuator force.
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