This illumination distribution results from a microwave converter spacing given by: An analysis by Raytheon revealed that 87.5% of the waste heat generated in the microwave converter tubes would be radiated towards the antenna support structure, with the remaining 12.5% being radiated out of the opposite side of the antenna surface toward earth. Thermal analyses of the following key problems were performed using the above values for the MPTS parameters: Geometry of beam cap elements, temperature difference between beam caps, column temperatures, and effect of microwave converter spacing on the waste heat profile with its attendant effect on beam and column temperatures. 3.3.2.1 Geometry of Beam Cap Elements This study involved determining the maximum temperature and the temperature difference within structural members having tubular, high-hat and triangular cross-sections (Fig. 3.3-11 and 3.3-12). Maximum temperature is important from the materials selection and strength standpoint, while temperature gradient is important because of the induced thermal stresses. The structural members considered in this study are those that make up the beam cap and are in a plane parallel to the antenna surface (Fig. 3.3-11). (Members in a perpendicular plane were considered separately.) They are heated by radiation from the hot antenna surface below it. For this study the antenna surface at the center was taken to have an. effective temperature of 600° K which is approximately the situation when the antenna is 1.0 km in diameter and transmitting 6.45 GW with a microwave converter efficiency of 75%. The temperature analyses were performed by subdividing the particular geometry into nodes (between 8 and 11, depending on the shape) and determining the radiation couplings between the nodes themselves and between the nodes and the antenna surface as well as deep space (Fig. 3. 3-13). The computer programs CONFAC (CONfiguration FA Ctor) and AF1 (script F) were used to determine the 50 or so significant radiation couplings. Conduction effects were neglected, which is a conservative approach, pending material and thickness selections. Once the mathematical model of a geometry was established the computer program SSTA1 (Steady-State Thermal analysis 1) was run to evaluate temperatures. The results of the investigation are discusse ext. 3.3.2.2 Tubular Cross-Section Figure 3. 3-- resents the maximum temperature that a structural member with a tubular cross-section will experience as a function of the effective antenna surface
RkJQdWJsaXNoZXIy MTU5NjU0Mg==