transmits a small fraction of the total power in each beam in the correct direction to produce a given power beam. Thus, it is not necessary at the power source to have huge electrical components such as turbines, generators, closely packed klystrons, batteries, cables or other devices which are expensive to build and maintain. The lunar power system is not highly integrated physically as is the SPS or any terrestrial power facility. Rather, the integration is through electronic phasing conducted in very large scale integrated circuits. The technology is very well understood because of the development of phased array radars. Costs of these systems are decreasing rapidly. Recent industrial studies indicate the overall reasonableness of producing VLSI circuits in space (13). Production of simpler solar converters will be far less challenging. We estimate the mass of machinery to emplace 1 MW every 24 hr of power generation and transmission capacity over the course of a year to be approximately 600 tons. The choice of 1 MW every 24 hr is arbitrary. Lower initial rates would likely be sensible and feasible. The mass estimate includes habitats for 20 people to oversee the operation. Approximately 50 kg of system components are needed from Earth per MW of beamed power. Compare this to the 10,000 kg per MW for SPS. We estimate the system returns its electrical energy of construction, including the energy to import components from Earth, in a few 10s of days. The addition of two orbiters to the Space Transportation System would permit the deployment to orbit about Earth is less than one year of the components, transfer rockets and people to establish the demonstration lunar power base. Oxygen derived from lunar materials in LEO can be provided at an early date and hydrogen scavenged from External Tanks taken to orbit during deployment of the lunar base. Either strategy would eliminate the need for additional space shuttle flights. A third key to the Lunar Power Concept is that most of the machines used to build lunar power components from lunar materials can themselves be built of lunar materials. MIT (18) studies noted that SPS factories could be built in space primarily from lunar materials. We estimate that 90% of the installation unit can be made from lunar derived materials. Approximately 60 people would need about 600 tons of manufacturing facilities, tools and habitats to produce one installation unit in 30 days. One installation unit is the complete collection of machines (much as depicted in Fig. 3) required to initially install 1 MW of power transmission capacity on the moon in 24 hr. Figure 4 qualitatively depicts the potential power of this approach. The cross- hatched boxes are complete installation units such as depicted in Fig. 3. The first would be deployed completely from Earth. It would be used to install the power units shown as clear boxes at the bottom of this figure. A complete box might correspond to several 10s of MW of installed power capacity. The increasing numbers below the axis indicate the cumulative power output of all the completed power plots. On completion of a demonstration period a manufacturing unit (black box) would be transported from Earth. Production of installation units would begin and accelerate as experience is acquired. Thereby the installation rate of power units can be increased in essentially an exponential manner. Table 1 contains the production and power ratios used to estimate the masses of both the installation machinery and manufacturing facility. Few if any factors (such as launch costs) would limit the downward trending costs of producing LPS as industrial experience is acquired on the moon. For instance, components of LPS needed from Earth can be decreased. Progressively fewer people will be required to operate the installation units. The production units can begin to build components on the moon of other production units. Industrial learning
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