ENERGY IN SPACE

The usual way to provide energy for space vehicles is to use solar photovoltaic panels, or produce electric energy from fuel cells [AtE Jul 77], i.e., from chemically stored energy in fuels taken along from the earth. The main constraint is weight per power, which is now from 6 to 10 kg per kW, including regulation, control and battery-charging electronics; but NASA would like to reduce the ratio to 5 kg/kW by the end of the decade, and to 1 kg/kW by the end of the century. This constraint pretty well rules out nuclear power; the lead shielding makes reactors too heavy.

One proposal under consideration for powering a number of space vehicles is to have a central, stationary space power satellite that would collect solar energy and beam it to other spacecraft.

An alternative is to use the incident sunlight to power the "pump" of a laser. The pump is a device using high-intensity incoherent (i.e., regular) light to stimulate the atoms in a gas, which then emit coherent laser light, a very pure, penetrating, powerful type of light that could carry the energy in thin, precisely controllable beams.