NASA SP-413 Space Settlements - Saint Ann's School

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92 NASA SP-413 — SPACE SETTLEMENTS — A Design Study Figure 5-18 — Energy flow in the colony. Within the habitat itself the largest energy input is the insolation of the agricultural areas (the bulk of which is transferred to water evaporated from the foliage) and the residential areas (see fig. 5-18). A smaller but significant portion of the total input is the electrical power supplied to the colony from its solar-electric power station. The habitat’s electrical power consumption per capita is 3 kW, a figure obtained by doubling that of the current U.S. per capita consumption to account for the need to recycle all materials in the colony. The energy removed from the atmosphere is transferred to the working fluid of the radiator. Assuming a radiator temperature of 280 K, corresponding to a black body radiation of 348 W/m 2 , the required area of a 60 percent effective radiator is 6.3 X 10 5 m 2 . An increase of 50 percent in the area to handle peak daytime solar loads is appropriate; therefore, the required area is 9.4 X 10 5 m 2 . Woodcock’s estimate (ref. 10) of 2.5 kg/m 2 for the mass of a radiator leads to the habitat requiring 2400 t of radiator mass. PRODUCTION AT L5 Stopping for a mug of Space Blitz on the way back to your apartment you happen to catch the Princeton-Stanford ball game on television from Earth and learn that, to everyone at the bar, the three-dimensional ball game played in the central hub is much more thrilling. You find that really only the name of the game played at the colony is the same since the liberating effects of low gravity and the Coriolis accelerations make all shots longer, faster, and curved, thus completely changing the rules and the tactics of the game. Later the TV news carries a story on difficulties encountered in building the new SSPS. There have been several unforeseen problems with all phases of the production process but in particular with the extraction facility which, to avoid pollution of heavy industry and to isolate a possible source of industrial accident from the habitat, is placed outside the habitat, south of the hub some 10 km away. Although the plant is operated remotely so that it can be left exposed to the vacuum of space, there are a number of small spheres attached to the plant where maintenance can be performed in a “shirt sleeve” environment. The plant has its own solar furnaces and a 20O MW electric power station run by solar energy. Bulk products such as aluminum ingots, oxygen gas, plate glass, expanded soil and shielding material, are brought to the fabrication sphere by small tugs. However, small items and people make the trip through a pressurized transport tube which seems to be developing structural problems near its remote end. In the bar, a construction foreman tells you he is convinced the problem derives from torsional fatigue, but no one seems to be worried since many such problems in the system have been quickly solved in the past. On learning you are a newcomer the foreman offers to act as guide on a quick visit to the fabrication facilities where the major effort of the colony is concentrated and, if possible, down the connecting tube to the extraction plant. Pleading fatigue you head home. At your apartment, you put your feet up and read some descriptive material on the fabrication facilities. Chapter 5 — A Tour Of The Colony
NASA SP-413 — SPACE SETTLEMENTS — A Design Study 93 Productivity in Space Construction Productivity in space is difficult to estimate (see appendix D). The zero g and high vacuum in some situations increases productivity above that obtainable on Earth and decreases it in others. The only basis for estimation is experience on Earth where the models of industrial productivity used are based on factors of man-hours of labor per kilogram, per meter, per cubic meter, etc. Table 5-6 presents estimates of productivity of humans performing some basic operations of industry and construction. These numbers were derived from estimating factors commonly used on Earth (ref. 8) in 1975, which were modified somewhat on the basis of limited experience in the space program. Generally, because cost estimating factors are closely guarded proprietary figures in terrestrial industry, reliable information is difficult to obtain. Therefore, the estimates in table 5-6 are used, recognizing appreciable uncertainty in their values. A more detailed discussion of estimated productivity is given in appendix D. Manufacture of Satellite Solar Power Stations In addition to constructing new colonies, the manufacture of satellite solar power stations is the second major industry. Such power stations provide the chief commercial justification of the colony. Placed in geosynchronous orbit they satisfy the Earth’s rapidly increasing demand for electrical energy by capturing the energy streaming from the Sun into space and transmitting it to Earth as microwaves where it is converted to electricity and fed into the power grids. While such satellite power stations could be built on Earth and then placed in orbit (refs. 9 and 10), construction in space with materials from the Moon avoids the great expense of launching such a massive and complex system from Earth to geosynchronous orbit. The savings more than offset the higher costs of construction in space. Analysis shows that 2950 man-years are needed to build a satellite solar power station to deliver 10 GW to Earth. A summary of the man-years required for different options for constructing part of the system on Earth and part in space, or for using a photovoltaic system rather than a turbogenerator, is given in table 5-7. Other Commerce There are commercial activities of the colony other than those of constructing satellite solar power stations or new colonies. The easy access to geosynchronous orbit from L5 puts the colonists in the satellite repair business. TABLE 5-6 — REPRESENTATIVE PRODUCTIVITIES Industry or product Primary aluminum (Hall process) Titanium mill shapes Household freezers Light frame steel erection Piping, heavy industrial Productivity 97 kg/man-hr 8.8 kg/man-hr 20 kg/man-hr 28.57 kg/man-hr 0.26 m/man-hr Thermal SPSS, 10 GW Complete SPSS Generator (SPSS w/o transmission) Heating furnace only Photovoltaic SPSS, 5 GW Complete SPSS Generator (SPSS w/o transmission) Notes: TABLE 5-7 — OFF EARTH LABOR REQUIREMENTS FOR SPSS’S Labor, man-years Communications satellites, which otherwise might be abandoned when they fail, can be visited and repaired. Furthermore, the solar power stations themselves require some maintenance and may even have crews of from 6 to 30 people who are periodically rotated home to L5. There are also commercial possibilities only just being appreciated. In high vacuum and zero g adhesion and cohesion effects dominate the behavior of molten material. Products such as metal foams and single crystals are more easily made in space than on Earth In fact in 1975 McDonnell Douglas Astronautics Company (ref. 11) concluded that the growing of single-crystal silicon strip using an unmanned space factory would be economically advantageous. Certain features are common to all commercial ventures in space. High cost of transportation makes shipment of goods to Earth from space uneconomical except for products with a high value per unit mass that are impossible to make on Earth. Advantages of high vacuum and reduced weight often enhance productivity. Availability of large quantities of low-cost solar energy permits production processes in space which consume such large amounts of energy that they are impractical on Earth. The expense of providing human workers encourages reliance on automation which, because of the expense of repairs and maintenance, is pushed to extremes of reliability and maintainability. The expense of replacing lost mass places strong emphasis on making all production processes closed loops so that there is very little waste. Extraction Processes for Lunar Ores 2950 1760 1600 2540 1800 Assumes the use of lunar material in productive facilities already in place and high-technology equipment supplied from Earth. The thermal data are based on Woodcock (see ref. 26, ch. 4) and the photovoltaic data on Glaser (see Ref. 25, ch. 4). Production at L5 is strongly influenced by the processes available by which to refine needed materials from the lunar ores. These processes in turn specify the mass of ore required, necessary inventories of processing chemicals, and masses of processing plant. Figure 4-25 depicts the sequence of processing to produce aluminum from lunar soil. The soil is melted in a solar furnace at a temperature of 2000 K then quenched in water to a glass. The product is separated in a centrifuge and the resultant steam condensed in radiators. (Table 5-8 lists the Chapter 5 — A Tour Of The Colony
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NASA SP-413 Space Settlements - Saint Ann's School

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