If there is a maximum temperature allowable for radiation, then there is an upper bound on the amount of heat that can be radiated per unit area. The amount of heat that can be radiated per square meter from one face is given by the expression: In the Solar Power Satellite the total area available for heat radiation is the backside of the transmitting antenna which is one kilometer in diameter or 785,000 square meters in the reference design. The microwave generators are integrated into the antenna as shown in Figure 1 [2], Magnetrons are shown distributed on the back of the antenna in the illustration but the same distribution would occur for other types of converters. This illustration also shows that the heat must be disposed of locally. It cannot logically be transported over long distances to other radiating sites. If the entire back side of the transmitting antenna were available for radiating heat, and the insulation was perfect, the situation shown in Figure 2 would result. Assuming black body radiation, as much as 6.1 kW/m2 could be radiated into black space, and 4.7 kW/m2 with the complete absorption of the sun’s radiant flux impinging directly upon it.
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