various techniques for smoothing out the Gaussian waste heat distribution. (An important byproduct of this smoothing will be smaller temperature differences between structural members.) Techniques for smoothing the distribution that should be mvestigated are: (1) the use of geometrically and spectrally selective radiators, (2) heat pipes to transport heat away from the center and (3) through the selection of the constant in the microwave converter spacing equation 1 = 1 min. exp . It is recognized that this constant will affect the microwave transmission efficiency and the total power that can be handled by the MPTS. A study that includes the effect on structural temperatures is required to establish the p value that results in the maximum power received on Earth. As part of this study to increase the power transmission capability of the MPTS and increase the choice of structural materials, it is recommended that the effect of coatings on reducing the maximum structural temperature be investigated. Selective use of coatings will also offer minimization of temperature differences between structural members. 4.3.1.2 Desired Outputs • Conceptual design of geometrically and spectrally selective radiators along with their attendant MPTS power level increments • Performance requirements, installation considerations, and redundancy aspects of heat pipe designs along with their predicted power level increments. Due to the high temperatures (300 - 500" K) the heat pipe designs will involve new developments • Selection criteria for the spacing constant that provides maximum power received on the ground for a given antenna size and maximum structural temperature • Candidate coatings for the structural members with their attendant power level increments. Consideration for minimizing temperature differences between elements by selectively coating the members should be part of this study. The degradation performance of the coatings must be examined so as to ensure the 30-jrear design life of the MPTS. A test program for obtaining the necessary degradation data should be outlined as part of this study. 4.3.2 Transient Analysis The greatest uncertainty in the stress levels that the structural members will experience is due to the stress induced by the different transient thermal responses of the various structural members. To ensure that the lightest possible structure is used
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