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Thermal power systems for use in space normally reject energy as heat
by radiating it into space. Since fluid-filled radiators are generally
quite heavy, it has been suggested that this energy be converted to electricity
and the current run through lighter resistors to dissipate the energy as heat.
What do you think of this idea? Energy transfer as heat from a space
vehicle must take place by radiation. The weight of a space radiator
is proportional to its area, which is determined by the rate at which the
energy must be radiated as heat: the rate of energy radiation is
proportional to the product of the area and the fourth power of the
radiator temperature. Consider a reversible 2T engine giving a fixed
amount of power and operating with a fixed source temperature. Show that
the least radiator weight is obtained when the radiator temperature is
0.75 times the source temperature.
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