5. Mass Properties To determine the range of weights of the satellite, the following process was used. The three estimates of system efficiencies presented in figure IV-2 were used to define the solar array area necessary to provide 10-GW power output to two rectennas (5 GW each) for each estimate. The resulting areas were as follows. increased 4.3 percent to compensate for solar angle-of- incidence losses (see sec. IV-B-IV). For each subelement of the satellite, a "minimum," "nominal," and "maximum" unit weight was estimated. In this case, the minimum and maximum terms have the inverse meaning of that applied to the efficiency estimates. For example, the minimum weight is the best that might be achieved, whereas the maximum can be achieved with virtual certainty. Table IV-2 sunwarizes the minimum, nominal, and maximum unit weight estimates for the various subelements of the satellite. If the three subelement estimates are applied to each of the three array sizes and the two different configurations, a total of 18 (3 by 3 by 2) weight estimates are obtained. The resulting range, or envelope, of weights is presented in figure IV-7. The satellite mass is seen to be in a range between 47 000 and 124 000 metric tons. Note that this weight is associated with a satellite that provides 10 GW of power to two rectennas via two 1-km transmitting antennas. A satellite weight breakdown for 6 of the 18 estimates is presented in table IV-3. The six estimates presented are identified by symbols in figure IV-7. The breakdowns indicate the significance of the solar cell blankets to the total weight, approaching 50 percent in all cases. The SECS structure, on the other hand, is not a major contribution to the total, varying from 1 to 6 percent of the total for cases presented. The microwave generators contribute approximately 15 percent of the total weight. Note that the klystron was assumed for all estimates. Experience has shown that the total mass invariably grows during the course of any aerospace program, the amount depending on the degree of technology advancement involved. Fifty percent growth from the initial concept weight can reasonably be expected for a program of this nature. Accordingly, the totals obtained by summing the estimates of subelements have been increased by 50 percent. This weight growth has been included in the weights presented in figure IV-7.
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