data refer to The other is that the measured solar input horizon-to-horizon position of the Sun, whereas the overall reflector of the year. area is based on continuous irradiation between elevations of 40° or data are necessarily prehigher about the horizon. liminary. Nevertheless, the Due to light spillover, night light of intensity between midnight Sun and Cost figures depend on many assumptions and therefore are necessarily These numbers include a The reflectors with adjustable facets use structures of carbon epoxy and All parts are coated in space with the and membranes of kapton. ke-coated and serviced in 10-year fibers optically best material, sodium. At a sodium intervals, the reflectors should last 60 to 100 years. consumption of 1,500 tons annually, a service station may be established at libration point L-4 or L-5 in lunar orbit, supplied with sodium mined reflectors on the Moon (measured abundance 0.2 to 0.5 percent). The can commute to lunar orbit by a combination of sunlight pressure and electric propulsion. An important function of Agrisoletta could be the growth stimulation of biomass. The same reflector units as for Powersoletta could be used, only in smaller numbers and possibly in different orbital distribution. Production of chemical fuel through bioconversion, of course, is the only near-term alternative to coal and natural gas. Proposals have been made to grow plants specifically for conversion to energy in plantations of trees, grasses and kelp. It has been claimed that a 140-million acre ocean farm of a specific type of kelp could be converted to enough methane to meet the U.S. annual demand for natural gas. But Ocean crops would, for several reasons, be particularly actractive. whether land or marine plantations, the emphasis is on maximizing energy production, hence, minimizing planting-growing-harvesting cycles. Night illumination, or enhancement of solar irradiation during daylight by Space Light reflectors could accelerate the growing rate. research work is needed. More serious One ocean farm project is under way, funded by Federal authorities, the American Gas Association and General Electric Co. to produce pipelinequality methane from a quarter-acre undersea farm of giant kelp, five miles off the coast of California. If the experiment is successful (1.e. brings an estimated yield of about 300 mcf annually), giant farms could be feasible in the early 1990s when Agrisoletta systems could be available also. Earlier tests on the effectiveness of Space Light could be run in the second half of the 1980s. Agrisoletta also has the potential of preventing night frost damage and of influencing the quantity and timing of rainfall locally to some extent. A controlled Soletta/local weather interaction probably could only in rare cases be undertaken today. However, progress in meteorological research and of climatological research (including the important NASA-planned Solar-Terrestrial Observatory in space) should provide an adequate scientific foundation by the early 1990s, the time of earliest availability of an Agrisoletta large enough to carry out local weathermodifying functions. - A possibly unfavorable change in weather trends in different parts of the globe is anticipated by a number of scientists in this and other countries. In view of high global sensitivity to reductions in food production which will still exist in and beyond the 1990s -- a weather-influencing capability through Space Light could gain significant importance. It's another example of building options for the future, or at least assuring them, and making sure that the proverbial bridge that we are to cross when we are there, in fact exists. 24-215 O 78 - 36 THE LUNAR OPTION WE ARE VERY FORTUNATE TO HAVE SO CLOSE TO OUR UNIQUE PLANET A WORLD THAT THE LUNAR OPTION The lunar crust contains industrially valuable materials. The world reserves of some of these appear limited at present and, perhaps in some cases are, in fact, limited. But several factors seem to militate against major imports, in the next 20 to 30 years, to Earth of such materials as zinc, copper, nickel, manganese or titanium from space (aside from the fact that several of the scarce terrestrial materials are also not abundant on the Moon). In some cases, technological advancements will lead to commercial exploitation of progressively poorer grades, thereby enlarging terrestrial land reserves. Large mineral resources become accessible on the ocean floor. Progress in deep-shaft mining offers additional crustal reserves. Recycling and substitutions provide additional options for stretching terrestrial metal supplies. Job considerations in the primary (extractive) and secondary (refinement to semifinished products) metal industries are an additional factor. This leaves as comparatively closer prospect the advantages of the lunar environment (vacuum, low-g surface conditions, null-g in an orbiting lunar factory) for generating superior products (as in near-Earth factories) of comparatively high market value but larger masses than those that are most attractive for Earthorbiting factories, because of the availability of local resources and the low lunar gravitational pull. Access to low-gravity supplies can also be important for large space structures as are typically involved in the energy sector. For these, however with the notable exception of fusion-based power stations the most suitable construction materials (graphite composites, graphite fibers, epoxies, polyimides) are not available on the Moon. Therefore, there are only conditional and in most cases limited opportunities for taking advantage of lunar gravity to obtain construction materials for large space energy systems. But opportunities nevertheless exist. - Associated with the large masses of such systems are significant transportation requirements from Earth. If oxygen-hydrogen orbital transfer vehicles are used to lift a load of 100,000 tons from near-Earth orbit to geosynchronous orbit, the question whether the needed oxygen is delivered from Earth or from the Moon makes a difference of some 3.7 million tons of propellant burned in the a a tmosphere, with at least one million tons of water vapor released into the upper atmosphere. While this is not intolerable, it can nevertheless make lunar oxygen an attractive substitute, especially since it ranks second in abundance behind silicon. - - Lunar settlements offer an ideal and , compared to space colonies, inexpensive |