Nuclear Auxiliary Power Unit for Lunar Exploration

Unmanned soft lunar landing experiments by the United States are currently being planned by the National Aeronautics and Space Administration. All of these experiments will require some form of electrical power; and their success or failure will depend upon the development of a suitable, reliable electrical power generation system. The system utilized must be compact, lightweight and rugged. Certain requirements for such an experiment could be met by solar cell arrays. The reliability of solar cells has been well established; however, their usefulness for this mission is inherently limited. Experiments conducted during the lunar night require a large storage capacity, if solar energy is to be the spacecraft's only source of power. A radioisotope-fueled thermoelectric generator can fulfill all spacecraft power requirements continuously throughout the lunar day or night without special orientation. A radioisotope, such as Curium-242, may be used as the thermal energy source for a lunar experiment of short duration (90 to 120 days). Curium-242 does not occur in nature, but may be created by the neutron irradiation of Americium-241. This radioisotope requires very little radiation shielding to protect sensitive equipment, because of the low gamma flux associated with its decay. The rigors of the lunar "climate" produce an environment which present-day electronic equipment will not tolerate. By utilizing waste heat from the radioisotope generator, the electronics compartment temperature may be controlled within acceptable limits. All subsystems within the generator may be duplicated to improve its reliability.