V. Employment

����������� Although some jobs will cater to the needs and wantsof the colonists, services and products will primarily drive the economy of�ther sold to earth.� Three primarysources of employment on �ther will be industries, research, and exploration.

V.A Industries

����������� Thelocale of the colony makes possible many novel techniques and resources, someof which have not been discovered hitherto.Solar power, asteroid mining, space tourism, satellite construction, andscientific missions would all be easier to attain through the use of thecolony.

V.A.1 Solar Power

����������� Solarpower has been touted as the ultimate non-polluting alternative to theenvironmentally costly ways of generating electricity today.� While some pollution would be released intothe atmosphere as a result of photovoltaic (PV) cell fabrication and launch ofsolar power satellites, these concerns could easily be side stepped if PV cellfabrication occurred in outer space, where the pollution would not harmterrestrial life.� Compounding the problemof pollution from existing power plants is the fact that global power demand isrising.� Population is growing at thesame time per capita energy use is growing, thus the global environment bearsthe brunt of ever escalating pollution.Modern power plants produce many types of pollution, coal-fired powerplants release carbon dioxide, sulfur oxides, and a host of other toxic metalsincluding some radioactive isotopes into the air; nuclear power plants do notrelease much pollution, but there is the problem of long-term storage ofnuclear wastes associated with it.While wind-driven power plants and other alternative sources of powerare coming into use, the predominant means of power generation is the combustionof fossil fuels.

The modular,self-deploying solar power satellites considered in NASA�s 1995 Fresh Lookstudy showed a significant cost decrease over the older models that had beenpreviously considered in the 1979 DOE-NASA study.

����������� Photovoltaicmaterials fall into two general categories: thick crystalline andthin-film.� Silicon and gallium arsenideare thick crystalline, while amorphous silicon and polycrystalline silicon arethin-film materials.

Mostphotovoltaic cells used today are made of single-crystal silicon.� Single-crystal photovoltaic cells require asource of 99.9999% pure silicon, which are grown into ingots; wafers are thensliced from this ingot and used for constructing the different parts of thecell.

Gallium arsenide(GaAs) is even more expensive than single-crystal silicon as gallium is morerare than gold, and arsenic requires careful handling.� However, the benefits are enormous, as GaAscells can reach efficiencies of 25-30%, are insensitive to high temperatures,have high absorptivity, are immune to radiation damage, and can have theircharacteristics precisely controlled by adding aluminum, phosphorus, antimony,or indium.

Amorphoussilicon is a non-crystalline form of silicon and absorbs light moreeffectively, thus a thinner layer is required.Amorphous silicon is usually deposited onto a substrate usingfabrication techniques that are less expensive than single-crystal siliconmethods.� However, efficiencies are onlyaround 5-7%.

Polycrystallinethin-film technologies utilize the sequential deposition of materials onto asubstrate to provide an inexpensive and easily scaled method of producingphotovoltaic cells.� However,polycrystalline photovoltaic cells suffer from poor durability and lowefficiencies.

By stackingseveral different types of cells, a multi-junction cell can be produced, withthe topmost cells absorbing the high-energy light, while the bottommost cellsabsorb the low-energy light.� Commonly,gallium arsenide is used as all or some of the component cells, but amorphoussilicon and copper indium diselenide component cells have also been used [ref37].� Multi-junction or cascade cellsprovide great design flexibility, achieve higher efficiencies, and offergreater resistance to radiation.Naturally, they are more expensive as they require more complex fabricationtechniques.

����������� Concentratorlenses can also raise power output as the cell is receiving stronger lightintensities.� However, they pose therisk of overheating the cell, and thus reducing efficiencies and destroyinglong-term stability.� The lenses mustalso be precisely aligned with the sun�s rays, otherwise they would be focusingthe light onto an unwanted point [ref 37].

����������� Thetechnology of choice to use for solar power satellites and for power generationon the colony seems to be crystalline silicon with concentrators.� Since silicon is abundant on the moon andcrystals with few imperfections can be grown in microgravity, crystallinesilicon cells would give the maximum efficiencies at acceptable costs.� The concentrators can be fashioned out of lunarsilicon and can be coated with thin layers of selectively transparentmaterials, so that the cells are shielded from unnecessary radiation that wouldcause heating.� Solar power satellitesmay contain longer-lasting gallium arsenide cells if longevity is of concern,but since the cells used for colony power generation can be easily replaced,less durable cells that are more economic may be used.

����������� Probablyone of the most important parts of a SPS system is the method by which powerwill be transmitted from the SPS to the paying customer.� Microwave provides the most efficient methodof power transmission, with recent transmission loss rates of only 18% [ref25].� In the scheme envisioned by NASAengineers, the solar power satellites would be outfitted with microwavetransponders, which would beam the energy to earth, where a large antenna wouldreceive it.� This system ideally wouldproduce no waste matter, no sulfurous emissions, and no greenhouse gasses.� Construction of the large antenna could takeplace in isolated or offshore areas relatively close to the markets it servesso as to reduce electric transmission losses, and all that is needed is to wirethem into the existing electrical grid.By using select microwave frequencies around 2.45 GHz, absorption ofenergy by water vapor and air can be avoided [ref 9].� Since microwave radiation is non-ionizing and possesses lessenergy than sunlight, radiation effects, such as increased risk of cancer,damage of genes in sex cells, and massive death of somatic cells, commonlyassociated with high-energy electromagnetic waves and heavy nuclei would not bepresent.� Thus the only effect of themicrowave beam would be the heating of the object inside the beam.� There is however, growing concern over the�Microwave Effect,� which seems to show that microwaves can indeed break thecovalent bonds inside DNA due to the formation of free radicals [ref 39].

The AmericanNational Standards Institute dictates that the general populace should not beexposed to more than 10 mW/cm² of microwave intensity, and currentdesigns for solar power satellite microwave transmission utilize a microwavebeam that possesses an intensity of 23 mW/cm² and an intensity of0.1 mW/cm² at the beam fringe [ref 9, 38].� The ground-based antenna could be constructed so that light canstill pass through, and the area directly underneath could be used for cropgrowing.� Birds and animals passingthrough the beam would experience only a slight heating, which would become anissue only on hot days.

V.A.2 Lunar Mining & Manufacturing

����������� Miningand processing the lunar soil and rocks for valuable metals would be easy sincethe infrastructure for such tasks would already be required for constructingthe colony.� Augmenting and maintainingthe existing facilities would be even easier than the task of establishing thelunar base, since by then a highly productive and accessible manufacturingcenter would be in place at �ther and on the moon.� Large-scale exploration and exploitation of lunar resources wouldbe made possible by a permanent presence on the moon, and different lunar baseswould be established to harvest the local minerals.� Expeditions to the lunar poles where ice is suspected to haveaccumulated would also be feasible, and may simplify many life support andmanufacturing needs.� Helium-3 depositedby solar winds can also be harvested and utilized in experimental fusionreactors.� Self-contained mobile units,which extract volatiles from the lunar crust and store them in pressurizedtanks, have been designed and could potentially gradually build up thestockpile of helium-3 needed for fusion.

V.A.3 Asteroid Mining

����������� Theasteroids that would be of main interest to asteroid-mining colonists would bethe Aten, Apollo, and Amor asteroids that have orbits close to the earth.� These asteroids contain many desirablematerials, such as water, methane, iron, nickel, cobalt, and many othersubstances that would garner high prices in today�s market.� In fact, about half of the nickel used todaycomes from an asteroid�s impact crater.Also, rare platinum and platinum-group metals are also present inasteroids and would fetch high prices in earth markets.� Nonmetals such as gallium, germanium, andarsenic would also be in demand in the semiconductor industry.

����������� Methodsof extracting those valuable ores and materials from asteroids would differbased on the type of asteroid.� If theasteroid is differentiated, that is if it had formed when it was molten hot,the elements would be separate from each other and quite possibly in convenientlocations.� If the asteroid isundifferentiated, then some chemical processes similar to those used forextracting metals from lunar soil and rocks might be required before thedesired substances can be acquired.Volatiles could be extracted using lightweight solar ovens that focussunlight and then stored cryogenically.These volatiles would include N₂, which would be integratedinto �ther�s atmosphere or used for a future space colony; H₂ usedfor fuel; O₂ used for oxidizer in chemical rockets or in habitableatmospheres; and CO₂, used for agriculture[http://www.seds.org/~rme/nea.htm].Mass drivers similar to the one on the moon would then be built or movedto the asteroid, and processed materials periodically sent back to �ther, themoon, or the earth.� Asteroid miners (orasteroid-mining robots) could be like parasites moving from asteroid toasteroid and devouring them piece-by-piece.Metal extraction and refinement in space could be of great benefit toearth�s environment, as earth-bound processes release much sulfur into the air,which in turn causes many pollution problems.

V.A.4 Space Tourism

����������� Tourismis centers around the idea of buying an unforgettable experience.� Thus, the exotic locale of the colony makesit ideal for tourism.� Space tourism hasalready begun on earth on a limited scale in the forms of MiG-25 flights andthe like.� However, before space tourismcan really bring in significant revenue, space flights must have a safetyrecord comparable to that of aviation.Fortunately, this goal would already be addressed since it is aprerequisite for colony construction.Tourist accommodations could be in the form of hotels inside the colony,or �cruise ships� that orbit around the moon and earth, offering spectacularviews.� Zero-g entertainment would alsobe a key �hook� for earth-based tourists.However, a CELSS designed for tourist use would have to take intoaccount that most tourists would want more food, water, etc. than the averagecolonist.� Specialty foods and beveragesthat could not be produced from the onboard CELSS would have to be importedfrom earth, making the price of such a hotel very expensive.� Considering that people do pay exorbitantsums for cruises, such a space industry is not very far fetched.

V.A.5 Satellite Construction

����������� Launchingsatellites from the colony would result in lower costs, as less fuel would beneeded to maneuver them into their final orbits.� Also, satellite construction would not have the restrictionsplaced on them by the use of earth-based launch vehicles; they would not haveto withstand the large forces exerted on them during liftoff and they would notbe limited to the payload capacity of the launch vehicle, thus eliminating theneed for modularization of the satellite and costly multiple launches.� Servicing of satellites that have brokendown would also be much more cheaper than current methods that involveearth-based astronauts.

����������� Largecommunications satellite constellations in low earth orbit would be able to providemany services to earth-bound humans, and they would have many advancements overcurrent satellites, including a stronger transmitter, larger antennae, betterheat rejection capabilities, increased intrasatellite communications abilities,better stationkeeping abilities, and more radiation shielding [9].� These satellites would be able to providemobile phone coverage, wireless internet services, and many othercommunications services.

V.B Research

����������� In the exotic environment of microgravity, many importantexperiments can be carried out.Particular topics of interest are microgravity fluid dynamics,astronomy, protein synthesis, nanotechnology, vacuum research, biotechnology,microbiology, growth of imperfection-free semiconductor and metallic crystals,and materials processing.� By analyzingthe behavior of normal processes in microgravity, knowledge about how gravityimpacts those processes can be derived, and thus methods can be devised andimplemented on earth to counter the negative effects of gravity.� Large telescopes can easily be constructedusing lunar materials, and relatively little computation will be needed tocorrect for aberrations in the image, since there is no atmosphere in space todistort the image.� Other data-gatheringinstruments, such as gamma ray, x-ray, radio, and microwave telescopes wouldalso be scaled up and be able to benefit from interference-free observing.

V.C Exploration

����������� Exploration of the Solar System and the universebeyond Pluto will be greatly accelerated by the construction of �ther.� Instead of facing exorbitant launch costs,scientists can build a custom-designed probe or use a generic probe and send itfar into the depths of space using maglevs that would accelerate them to theproper velocities.� Probes would alsonot suffer the mass restrictions placed on them by conventional earth launchesand thus would be able to record much more data in the same amount of time,since more instruments and larger radio dishes can be placed into a probe.� Planets only given a cursory glance at theexpense of millions and even billions of U.S. dollars would be thoroughlyexplored and analyzed, while planets and orbiting bodies never before exploredwould also enjoy a greater amount of attention.