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 into 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 engine providing a fixed amount of power output 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.