meteoritic bombardment of the surface. These iron grains can be extracted with a simple magnet attached to the front of the tractor. The tractor can extract approximately its own mass in iron per hr. The iron and adhered glass is taken by the tractor to a solar furnace and melted. The iron is then formed into rolls of wire. Molten glass is formed into support sections and metal coated glass fibers to make into segmented microwave reflectors (not shown in this drawing). Remaining glass is placed in a refractory hopper in the tractor. Returning to the emplacement area with iron and molten glass the tractor forms north-south aligned ridges of lunar soils. It sprays the soil surfaces with the molten glass to form a hard surface. Iron wires to collect the solar electricity are placed under the soil and some iron is vapor deposited on the surface glass to complete one side of the electric circuit. A thin film of amorphous silicon (extractable from the lunar materials) or other thin film photoconversion materials brought from Earth (very small quantities) are then deposited over the iron. A second layer of iron is then vapor deposited over the photoconverter and hooked into the subsurface grid. A thin protective layer of clear glass might be placed over the final tracery of iron. The photoconversion surfaces are sloped so that the geometry of solar exposure approximately levels the electrical output of a given power plot over the course of the 14 days of lunar daylight. Many types of photoconversion and power storage devices can be built from native lunar materials and installed on the moon. Figure 3 illustrates only one approach. At first only low efficiency devices may be used, possibly 1 to 5% overall conversion efficiency. Higher efficiencies are clearly within the state of the art of solar conversion systems. Several reasonable factors (denser arrays, higher photoconversion efficiency, increased photocell area, orbiting mirrors, and higher duty cycles for multiple bases) allow growth of the system from 2 MW to 1,000 MW (1GW) per km2 of transmission area. On the lunar surface power is collected over only a small area such as is qualitatively indicated by the three small rectangular power plots just beyond the astronaut. Power is brought by the buried iron wires into a collection of many solid state microwave transmitters indicated by the dots at the center of each power plot. Common subsets of transmission elements in front of each billboard (not shown in Fig. 3) are phased by local absolute clocks or a fiber optics network laid underground between the many transmitter sites. Each common subset of transmission elements produces at least one power beam. These transmitters do not beam power toward Earth. Rather, the diodes in a given plot illuminate a microwave reflective billboard at the edge of the power plot opposite the Earth. When viewed from the general direction of Earth these reflective billboards appear to overlap into the one huge aperture which fills the local region. Billboards are formed primarily from lunar derived glass. The frames are made of foamed glass rods. The reflective surface is made of native lunar glass which is drawn into threads, coated with iron and then woven into a grid with a spacing of '/io the wavelength of the micro wave beam. The microwave reflector is essentially transparent to sunlight. The completely anhydrous nature of lunar soils makes it very likely they can be used to construct not only reflectors but a wide range of other components of the lunar power system (1,16). Distributed systems are the second key to the lunar power system (LPS). The power is not collected in one or a few large flows inside electrical conductors. Instead, the power is collected at low levels at many small “power plots.” The power to be directed to a given place in space is then summed up in the electromagnetic (microwave) beam in free space. Each subset of transmitters in each plot
RkJQdWJsaXNoZXIy MTU5NjU0Mg==