Engine* Study led to the definition of a power supply system that could be used to furnish power for lunar shelters, portable equipment and lunar vehicles at bases to be occupied by as few as two men for three months to as many as 18 men for periods extending to several years. The results of the earlier LESA studies have many elements in common with more recent studies [3-5] and some interesting differences. Some consideration from our LESA studies include the following: • After initial siting, the power system for a lunar base must be capable of orderly expansion from an initially low activity level to higher levels as lunar exploration and development progress. The power system must be capable of providing the relatively large power demands of permanently installed equipment at one central location and also must provide the mobile power for vehicles, portable power supplies, other similar devices associated with exploration and scientific activities remote from the main base, and the processing of lunar materials. • Along with power system reliability, it is apparent that power cost per kW-hr is a dominant factor in system selection. It is also apparent that, in order to reduce transportation costs associated with logistically supplied fuel and materials, it is desirable to use nuclear power to the maximum extent practicable. • The relationship of the different power sources and options is presented in Fig. 1. The condition in which all power requirements are met by fuel logistically supplied from earth (non-regeneration option) is shown, along with the second condition, in which reaction products are regenerated using power from a central station nuclear or solar plant. • The limitation of the solar power system—fuel processing during the lunar day only—results in a regeneration plant having double the capacity of one required when nuclear power is employed. Comparison With Recent Lunar Base Studies Both the earlier LESA and more recent lunar basing scenarios assume phased development from initial exploration and site selection through growth of the permanent base. Comparisons in Table I and Fig. 2 show major differences in the lunar base evolution schedules and the estimated power demands. The lunar base scenario of Ref. [3] continues for 20 years or a factor of five longer than the LESA projection before building up to a crew level of 18 where the base is self-sustaining. A shorter base development schedule may be more desirable in order to avoid the potential loss of public and political support for the cost of transferring many metric tons of logistic materials over such a long period of time. Solar Versus Nuclear Energy As noted above, the lunar night cycle imposes limits on the solar power system option that requires a significant increase in the fuel regeneration system capacity. Other * Where ‘engine' is a generic term meaning a device which converts energy into a useful form including direct energy conversion devices (fuel cells, photovoltaic cells) and dynamic devices such as Stirling engines.
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