Optimization of heat rejection in space

The system mass requirement for waste heat radiation into space from a thermal source is reducible through heat rejection from a radiator whose temperature is higher than that of the thermal source; this calls for a heat cycle that is powered by a second heat source operating at a temperature that is higher than that of the waste heat source. In the case of Carnot cycle temperature ratios of the second-to-first source of the order of 5, total radiator area is found to be reduced by a factor of 16; practical heat cycles may be expected to yield factor-of-10 radiator area reductions.