High capacity power systems for space

Candidate high-power supply systems for future space missions are discussed. Solar cells, particularly made from GaAs materials, are projected to be amenable large arrays that will have a 10 yr lifetime with a 15 percent efficiency at the end. Concentrator arrays using GaAs cells could furnish over 200 W/sq m with 100 suns irradiance. Different battery systems, other than the present low-power NiCd storage systems, will be required, and could be either fuel cell systems or NiH2 batteries. The flywheel also offers promise, especially if integrated within the attitude control system. Solar thermal systems are also possible, featuring SiGe thermocouples, or boron alloys or rare earth calcogenides in thermoelectric generators or thermionic converters equipped with alkali metal elements. Mechanical systems, notably the Brayton cycle engine, offer multihundredwatt performance and higher, with at least 3.5 yr lifetimes. Experimentation is still needed to characterize the power supply interaction with the spacecraft environment and to design efficient and long-lasting radiators if heat engines are implemented.