constant temperature difference existed between upper and lower caps, the structure could be built with members prestressed such that when the temperature difference was applied the antenna would straighten out and become flat. However as the MPTS travels around an orbit the temperature difference between beam caps will vary. An analysis was performed to assess the temperature difference between beam caps, both on a daily and yearly basis. Figure 3. 3-24 presents results of the analysis and shows several things. The first is that the greater the separation distance between elements, the greater the temperature difference between them. There is virtually no temperature difference between elements located 6 meters and 1 meter above the antenna surface, except near the perimeter where the difference is approximately 3°K. The difference in temperature between elements at 41 meters and 1 meter varys from about 5°K near the center to nearly zero and then over 14° K at the perimeter. (Note that calculations for temperatures did not include the effects of partial shading that will occur during parts of an orbit and lead to an asymmetrical temperature profile about the center of the antenna.) Another item of importance shown in Fig. 3.3-24 is that the orbital variation in the temperature difference between the 41 and 1 meter locations is for the most part less than 2°K; and this is true any time of the year. The orbital variation in the temperature difference between the 6 and 1 meter locations is insignificant - it is lost in the thickness of the line. It is now apparent that the orbital variations in temperature difference are not large and therefore by properly rigging the structure the thermally induced deflections can be nulled out on an orbital average basis. The additional time varying deflections may prove negligible, especially if organic matrices are used, if not it may be possible to electronically compensate for them by "phasing" the microwave converters several times a day. It is instructive to consider the temperature differences that are produced by a more uniform waste heat distribution. Figure 3. 3-25 shows the situation for the scale factor meters which yields a power ratio of 5 to 1 in comparison with the 10 to 1 of Figure 3.3-24. A comparison of the two figures shows that the more nearly uniform the distribution, the smaller the temperature difference between beam caps. This is a second advantage to having a large scale factor; the first advantage of yielding a lower maximum temperature was mentioned earlier. 3. 3.2.7 Column Temperatures Temperature predictions for the columns or vertical members tying the beam caps together as well as the antenna surface to the beams are shown in Fig. 3.3-26. (Columns not shown will have temperatures intermediate to the center and perimeter column
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