Colonization of the Moon

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The colonization of the Moon has long been seen by science fiction writers and advocates of space exploration as a logical first step in establishing permanent human communities beyond the Earth.

Permanent human habitation on a planetary body other than the Earth is one of science fiction's central themes. As technology has advanced, and concerns about the future of humanity on Earth have increased, the argument that space colonization is an achievable and worthwhile goal has gained momentum. Because of its proximity to Earth, the Moon has been seen as a prime candidate for the location of humanity's first permanently occupied extraterrestrial base.

Should attempts at colonization go ahead, economic concerns are likely to lead to settlements being created near mines and processing centers, or near the poles where a continuous source of solar energy can be harnessed. While it would be relatively easy to resupply a lunar base from Earth (albeit with higher delta v[3]), in comparison to a Martian base, the Moon is likely to play a large role in the development of long-duration closed-loop life support systems. Duplicating the ecology of Earth so that wastes can be recycled is essential to any long term effort of space exploration. The wealth and knowledge gained by extracting and refining resources on the Moon would positively affect efforts to build colonies elsewhere in the Solar System.

NASA's long range Vision for Space Exploration plan includes a return to the Moon, with a manned mission in 2020 and permanent staffing of a polar base by 2024.^[1][2] A Chinese space scientist has said that the People's Republic of China could be capable of landing a human on the moon by 2022 (although the country has announced no formal plans for human lunar exploration)^[3] , and Japan is now talking about plans for a lunar base by 2030. ^[4]

Contents 1 History 1.1 Exploration phase 2 Advantages and disadvantages 2.1 Advantages 2.2 Disadvantages 3 Locations 3.1 Polar regions 3.2 Equatorial regions 3.3 Far side 4 Structure 4.1 Habitat 5 Energy 5.1 Nuclear power 5.2 Solar energy 5.3 Fuel cells 6 Transport 6.1 Earth to Moon 6.2 On the surface 6.3 Surface to space 6.4 Surface to and from cislunar space 7 Economic development 7.1 Space based materials processing 7.2 Exporting material to Earth 7.3 Tourism 7.4 Technology spin off 7.5 Solar power satellites 8 See also 9 References 10 External links

[edit] History

Space colonization

Mercury Venus Earth Moon Mars Asteroids Ceres Outer solar system Jupiter Europa Saturn Titan Pluto Kuiper Belt and Oort Cloud

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The notion of siting a colony on the Moon originated before the space age; Konstantin Tsiolkovsky, among others, suggested such a step^{[citation needed]}. From the 1950s onwards, a number of concepts and designs have been suggested by scientists, engineers and others.

Noted science fiction author Arthur C. Clarke proposed a lunar base of inflatable modules covered in lunar dust for insulation in 1954^{[citation needed]}. A spaceship, assembled in low Earth orbit, would be launched towards the Moon, and astronauts would set up the igloo-like modules and an inflatable radio mast. Subsequent steps would include the establishment of a larger, permanent dome; an algae-based air purifier; a nuclear reactor for the provision of power; and electromagnetic cannons to launch cargo and fuel to interplanetary vessels in space.

In 1959, John S. Rinehart suggested that the safest design would be a structure that could "[float] in a stationary ocean of dust," since there were, at the time this concept was outlined, theories that there could be mile-deep dust oceans on the Moon^{[citation needed]}. The design proposed consisted of a half-cylinder with half-domes at both ends, with a micrometeoroid shield placed above the base.

The Project Horizon was a 1959 study regarding the U.S. Army's plan to establish a fort on the Moon by 1967.^[5] H. H. Koelle, a German rocket engineer of the Army Ballistic Missile Agency (ABMA) was leading the Project Horizon study. The first landing would be carried out by two "soldier-astronauts" in 1965 and more construction workers would soon follow. Through numerous launches (61 Saturn I and 88 Saturn V), 245 tons of cargo would be transported to the outpost by 1966.

[edit] Exploration phase

Exploration of the lunar surface by spacecraft began in 1959 when the Soviet Luna 2 mission crash-landed into the surface. The same year, the Luna 3 mission radioed photographs to Earth of the Moon's hitherto unseen far side, marking the beginning of a decade-long series of unmanned lunar explorations.

Responding to the Soviet program of space exploration, US President John F. Kennedy in 1961 told the U.S. Congress on May 25: "I believe that this nation should commit itself to achieving the goal before this decade is out of landing a man on the moon and returning him safely to the Earth." The same year the Soviet leadership made some of its first public pronouncements about landing a man on the Moon and establishing a lunar base.

In 1962, John DeNike and Stanley Zahn published their idea of a sub-surface base located at the Sea of Tranquility^{[citation needed]}. This base would house a crew of 21, in modules placed 4 meters below the surface, which was believed to provide radiation shielding as well as the Earth's atmosphere does. They favored nuclear reactors for energy production, because they are more efficient than solar panels, and it would also overcome the problems with the long lunar nights. For life support system, an algae-based gas exchanger was proposed.

Manned exploration of the lunar surface began in 1968 when the Apollo 8 spacecraft orbited the Moon with three astronauts on board. This was mankind's first direct view of the far side. The following year, the Apollo 11 lunar module landed two astronauts on the Moon, proving the ability of humans to travel to the Moon, perform scientific research work and bring back sample materials.

Additional missions to the Moon continued this exploration phase. The Apollo 12 mission landed next to Surveyor 3 spacecraft, demonstrating precision landing capability. Following the near-disaster of Apollo 13, Apollo 14 was the last mission on which astronauts were quarantined on their return from the Moon. The use of a manned vehicle was demonstrated with the Lunar Rover during Apollo 15. Apollo 16 made the first landing within the rugged lunar highlands.

However, interest in further exploration of the Moon was beginning to wane among the American public. Apollo 17 was the final Apollo lunar mission, and further planned missions were scrapped at the directive of President Nixon. Instead, focus was turned to the Space Shuttle and manned missions in near Earth orbit. Responding to this new direction, the Soviet government also decided to direct their energies toward building a matching shuttle system, though in the 1970s they did land two robotic rovers on the Moon in the Lunokhod program and returned three lunar soil samples as part of the Luna program. 1974 also saw the end of the Soviet Moonshot, two years after the last American manned landing.

In the decades following, interest in exploring the Moon faded considerably, and only a few dedicated enthusiasts supported a return. However the discovery of hydrogen at the lunar poles^[6] rekindled some discussion, as did the potential growth of a Chinese space program^{[citation needed]} that contemplated its own mission to the Moon. Subsequent research indicated that there was far less ice present than had originally been thought, but that there may still be some usable deposits of hydrogen in other forms.^[7]

Spurred by the prospect of a Chinese lunar base^{[citation needed]} , in 2004, U.S. President George W. Bush called for a plan to return manned missions to the Moon by 2020. Propelled by this new initiative, NASA issued a new long-range plan that includes building a base on the Moon as a staging point to Mars. This plan envisions a Lunar outpost at one of the moon's poles by 2024, which, if well-sited, might be able to continually harness solar power; at the poles, temperature changes over the course of a lunar day are also less extreme^{[citation needed]} and reserves of water and useful minerals may be found nearby^{[citation needed]}.

[edit] Advantages and disadvantages

Putting aside the general questions of whether a human colony beyond the Earth is feasible or desirable (see: space colonization for a discussion of this question), proponents of space colonization point out that the Moon offers both advantages and disadvantages as a site for such a colony.

[edit] Advantages

Placing a colony on a natural body would provide an ample source of material for construction and other uses, including shielding from radiation. The energy required to send objects from the Moon to space is much less than from Earth to space. This could allow the Moon to serve as a construction site or fueling station for spacecraft^{[citation needed]}. Some proposals include using electric acceleration devices (Mass driver) to propel objects off the Moon without building rockets. Others have proposed momentum exchange tethers(see below). Furthermore, the Moon does have some gravity, which, experience to date indicates, may be vital for longterm human health^{[citation needed]}. Whether the Moon's gravity (roughly one sixth of Earth's) is adequate for this purpose remains to be seen.

In addition, the Moon is the closest large body in the solar system to Earth. While some Earth-crosser asteroids occasionally pass closer, the Moon's distance is consistently within a small range close to 384,400 km. This proximity has several benefits:

• The energy required to send objects from Earth to the Moon is lower than for most other bodies. Earth-crossing asteroids require a somewhat less delta V, but the months of travel required would necessitate a safe habitat for humans. The extra weight would likely more than offset any delta-V savings.
• Transit time is short. The Apollo astronauts made the trip in three days. Other chemical rockets such as would be used for any Moon missions in the next one to two decades at least, would take a similar length of time to make the trip.
• The short transit time would also allow emergency supplies to quickly reach a Moon colony from Earth, or allow a human crew to evacuate relatively quickly from the Moon to Earth in case of emergency. This could be an important consideration when establishing the first human colony.
• The round trip communication delay to Earth is less than three seconds, allowing normal voice and video conversation. The delay for other solar system bodies is minutes or hours; for example, round trip communication time between Earth and Mars ranges from about eight minutes to about forty minutes. This again would be of particular value in an early colony, where life-threatening problems requiring Earth's assistance could occur. (See, for example: Apollo 13)
• On the lunar near side, the Earth appears large and is always visible as an object 60 times brighter than the Moon does on Earth, unlike more distant locations where the earth would be seen merely as a star-like object, much as the planets appear from Earth. As a result, a Lunar colony might feel less remote to humans living there. The Apollo 8 astronauts, when behind the Moon, were the first humans to have no view of the Earth.
• A lunar base would provide an excellent site for any kind of observatory^{[citation needed]}. As the Moon's rotation is so slow, visible light observatories could perform observations for days at a time. It is possible to maintain near-constant observations on a specific target with a string of such observatories spanning the circumference of the Moon. Radio observatories could be considerably larger than the Arecibo radio observatory, due to the Moon's low gravity^{[citation needed]}. The fact that the Moon is geologically inactive along with the lack of widespread human activity result in a remarkable lack of mechanical disturbance, making it far easier to set up interferometric telescopes on the lunar surface, even at relatively higher frequencies such as visible light^{[citation needed]}.
• Perhaps most importantly, from a psychological point of view, the Moon is the only body in the Solar System that is visible as a disk with the naked eye from Earth. The ability to look up at the Moon and contemplate on other humans living their lives somewhere other than Earth would be a constant reminder that Earth need not be the only location for humans to live. Psychologically, it would be an important "first step" in colonizing other parts of our solar system.

[edit] Disadvantages

There are several disadvantages to the Moon as a colony site:

• The long lunar night would impede reliance on solar power and require a colony to be designed that could withstand large temperature extremes. An exception to this restriction are the so-called "peaks of eternal light" located at the lunar north pole that are constantly bathed in sunlight. Other areas near the poles that get light most of the time could be linked in a power grid.
• The Moon lacks light elements (volatiles), including hydrogen, carbon, and nitrogen, although there is some evidence of hydrogen near the north and south poles. Additionally, oxygen, though one of the most common elements in the regolith constituting the Moon's surface, is only found bound up in minerals that would require complex industrial infrastructure using very high energy to isolate. Some or all of these volatiles are needed to generate breathable air, water, food, and rocket fuel, all of which would need to be imported from Earth until other cheaper sources are developed. This would limit the colony's rate of growth and keep it dependent on Earth. The cost of volatiles could be reduced by constructing the upper stage of supply ships using materials high in volatiles, such as carbon fiber and other plastics, although converting these into forms useful for life would involve substantial difficulty. The 2006 announcement^{[citation needed]} by the Keck Observatory that the binary Trojan asteroid 617 Patroclus, and possibly large numbers of other Trojan objects in Jupiter's orbit, are likely composed of water ice, with a layer of dust, and the hypothesized large amounts of water ice on the closer, main-belt asteroid 1 Ceres, suggest that importing volatiles from this region via the Interplanetary Transport Network may be practical in the not-so-distant future. However, these possibilities are dependent on complicated and expensive resource utilization from the mid to outer solar system, which are not likely to become available to a Moon colony for a significant period of time. One of the lowest delta-V sources for volatiles for the Moon is Mars, suggesting that developing colonies on Mars first may in the long run be the easiest and least expensive way to establish a colony on the Moon.
• There is continuing uncertainty over whether the low one sixth g gravity on the Moon is strong enough to prevent detrimental effects to human health in the long term^{[citation needed]}. Exposure to weightlessness over month-long periods has been demonstrated to cause deterioration of physiological systems^{[citation needed]}, such as loss of bone and muscle mass and a depressed immune system. Similar effects could occur in a low-gravity environment, although virtually all research into the health effects of low gravity has been limited to zero gravity. Countermeasures such as an aggressive routine of daily exercise have proven at least partially effective in preventing the deleterious effects of low gravity^{[citation needed]}.
• The lack of a substantial atmosphere for insulation results in temperature extremes and makes the Moon's surface conditions somewhat like a deep space vacuum. It also leaves the lunar surface exposed to just as much radiation as in interplanetary space, although lunar materials would potentially be useful as a simple radiation shield for living quarters, shielding against solar flares during expeditions outside is more problematic.
• Also, the lack of an atmosphere increases the chances of the colonial site being hit by meteors, which would impact upon the surface directly, as they have done throughout the Moon's history. Even small pebbles and dust have the potential to damage or destroy insufficiently protected structures.
• Moon dust is an extremely abrasive glassy substance formed by micrometeorites and unrounded due to the lack of weathering^{[citation needed]}. The Apollo moon suits were worn out after just a few hours on the surface due to its abrasive properties^{[citation needed]}. It may well also be toxic^{[citation needed]}, and could cause Silicosis.

[edit] Locations

Russian astronomer Vladislav V. Shevchenko proposed in 1988 three criteria that a lunar outpost should meet^{[citation needed]}:

• good conditions for transport operations;
• a great number of different types of natural objects and features on the Moon of scientific interest; and
• natural resources, such as oxygen. The abundance of certain minerals, such as iron oxide, varies dramatically over the lunar surface.^[8] See: Geology of the Moon.

While a colony might be located anywhere, potential locations for a lunar colony fall into three broad categories.

[edit] Polar regions

There are two reasons why the lunar poles might be attractive as locations for a human colony. First, there is evidence that water is present in some continuously shaded areas near the poles^{[citation needed]}. Second, because the Moon's axis of rotation is almost perfectly perpendicular to the ecliptic plane, it may be possible to power polar colonies exclusively with solar energy. Power collection stations can be located so that at least one is in sunlight at all times, yet all are close enough to each other to be connected in an electrical grid^{[citation needed]}. Some sites have nearly continuous sunlight. For example, Malapert mountain, located near the Shackleton crater at the lunar south pole, offers several advantages as a site:

• It is exposed to the sun most of the time; two closely spaced arrays of solar panels would receive continuous power^{[citation needed]}.
• Its proximity to Shackleton Crater (116 km, or 69.8 mi) means that it could provide power and communications to the crater. This crater is potentially valuable for astronomical observation. An infrared instrument would benefit from the very cold temperatures. A radio telescope would benefit from being shielded from Earth's broad spectrum radio interference^{[citation needed]}.
• The nearby Shoemaker and other craters are in constant deep shadow, and might contain valuable concentrations of hydrogen and other volatiles^{[citation needed]}.
• At around 5,000 meters (16,500 feet) elevation, it offers line of sight communications over a large area, as well as to Earth^{[citation needed]}.
• The South Pole-Aitken basin is located at the south lunar pole. This is the largest known impact basin in the solar system, and should provide geologists access to deeper layers of the Moon's crust.

NASA chose to use a south-polar site for the lunar outpost reference design in the Exploration Systems Architecture Study chapter on Lunar Architecture.^[9]

At the north pole, the rim of Peary crater has been proposed as a favorable location for a base^{[citation needed]}. Examination of images from the Clementine mission appear to show that parts of the crater rim are permanently illuminated by sunlight (except during lunar eclipses)^{[citation needed]}. As a result, the temperature conditions are expected to remain very stable at this location, averaging −50° C (−58° F)^{[citation needed]}. This is comparable to winter conditions in the Pole of Cold in Siberia, or in some parts of Antarctica. The Peary crater interior may also harbor hydrogen deposits^{[citation needed]}.

Although hydrogen appears to be concentrated at the poles, the presence of water ice has not yet been confirmed. A bistatic radar experiment performed during the Clementine mission suggested the presence of water ice around the south pole. ^{[10] [11]} The Lunar Prospector spacecraft reported enhanced hydrogen abundances not only at the south pole, but also at the north pole — actually more so. ^[12] On the other hand, results reported using the Arecibo radio telescope have been interpreted by some to indicate that the anomalous Clementine radar signatures are not indicative of ice, but surface roughness.^[13] This interpretation, however, is not universally agreed upon.^[14]

[edit] Equatorial regions

The lunar equatorial regions are likely to have higher concentrations of Helium-3 because the solar wind has a higher angle of incidence.^{[citation needed]} They also enjoy an advantage in launching material from the Moon, but the advantage is slight due to the Moon's slow rotation.

One site mentioned by Shevchenko as meeting his criteria^{[citation needed]} is Oceanus Procellarum. Several probes have landed in that area. There are many areas and features that could be subject to long-term study, such as the Reiner Gamma anomaly and the dark-floored Grimaldi crater.

[edit] Far side

The lunar far side lacks direct communication with Earth, though a communication satellite at the L2 Lagrangian point, or a network of orbiting satellites, could enable communication between the far side of the Moon and Earth. It is also a good location for a large radio telescope because it is well shielded from the Earth^{[citation needed]}. To date, there has been no ground exploration of the far side.

Scientists have estimated that the highest concentrations of He-3 will be found in the maria on the far side,^{[citation needed]} as well as near side areas containing concentrations of the titanium-based mineral ilmenite.^{[citation needed]} On the near side the Earth and its magnetic field partially shields the surface from the solar wind during each orbit. But the far side is fully exposed, and thus should receive a somewhat greater proportion of the ion stream.^{[citation needed]}

[edit] Structure

[edit] Habitat

There have been numerous proposals regarding habitat modules. The designs have evolved throughout the years as mankind's knowledge about the Moon has grown, and as the technological possibilities have changed. The proposed habitats range from the actual spacecraft landers or their used fuel tanks, to inflatable modules of various shapes. Early on, some hazards of the lunar environment such as sharp temperature shifts, lack of atmosphere or magnetic field (which means higher levels of radiation and micrometeoroids) and long nights, were recognized and taken into consideration.

Some suggest building the lunar colony underground, which would give protection from radiation and micrometeoroids. This is not the only advantage to this option. The average temperature on the moon is about -5 Degrees. The day period (2 weeks) has an average temperature of about 107 degrees celsius (225 degrees fahrenheit), although it can rise as high as 123 degrees celsius (253 degrees fahrenheit). The night period (2 weeks as well) has an average temperature of about -153 degrees celsius (243 degrees fahrenheit). ^[15] Underground, both periods of the day would be around 24 degrees celsius (75 degrees fahrenheit), and humans could install basic air conditioners {ref needed}. The construction of such a base would probably be more complex; one of the first machines from Earth might be a remote controlled boring machine to excavate living quarters. Once created, some sort of hardening would be necessary to avoid collapse, possibly a spray-on concrete-like substance made from available materials.^[16] A more porous insulating material also made in situ could then be applied. Inflatable self-sealing fabric habitats might then be put in place to retain air. As an alternative to excavating, it is possible that large underground extinct lava tubes might exist on the Moon.^[17]

A possibly easier solution is to build the lunar base on the surface, and cover the modules with lunar soil. Others have put forward the idea that the lunar base could be built on the surface and protected by other means, such as improved radiation and micrometeoroid shielding. Artificial magnetic fields have been proposed as a means to provide radiation shielding for long range deep space manned missions, and it might be possible to use similar technology on a lunar colony. Some regions on the Moon possess strong local magnetic fields strengths that might partially mitigate against exposure to charged solar and galactic particles.^[18]

[edit] Energy

A lunar base would need power for its operations, from fuel production and communications to life support systems and scientific research.

[edit] Nuclear power

A nuclear fission reactor could possibly be able to fulfill most of the need for power. The advantage it has against a fusion reactor is that it is an already existing technology. One advantage of using a fusion reactor is that Helium-3, which is required for a certain type of fusion reaction, is abundant on the Moon. However, fusion reactors are far from being a practical power source at present and may not be available at the time of lunar colonization. Radioisotope thermoelectric generators could be used as backup and emergency power sources for solar powered colonies.

[edit] Solar energy

Solar energy is a strong candidate. It could prove to be a relatively cheap source of power for a lunar base, especially since many of the raw materials needed for solar panel production can be extracted on site. However, the long lunar night (14 Earth days) is a drawback for solar power on the Moon. This might be solved by building several power plants, so that at least one of them is always in daylight. Another possibility would be to build such a power plant where there is constant or near-constant sunlight, such as at the Malapert mountain near the lunar south pole, or on the rim of Peary crater near the north pole. See Peak of Eternal Light. The fact that solar power plants can store energy needed to run a whole moon colony would help, except the same amount of normal power used on Earth in the day would be needed for two weeks.

The solar energy converters need not be silicon solar panels. It may be more feasible to use the larger temperature difference between sun and shade to run heat engine generators. Concentrated sunlight could also be relayed via mirrors and used in Stirling engines or solar trough generators or it could be used directly for lighting, agriculture and process heat. The focused heat can also be employed in materials processing to extract various elements from lunar surface materials.

[edit] Fuel cells

Unlike solar and nuclear power, fuel cells are not a way to generate energy, but only a way to store it temporarily.

Fuel cells on the Space Shuttle have operated reliably for up to 17 days at a time. On the Moon, they would only be needed for 14.75 days - the length of the Lunar night. During the lunar day, solar panels (either photo voltaic or solar thermal) could be used as well as providing the electricity necessary to convert the water ('waste' from the fuel cells) back into hydrogen and oxygen ready for the next lunar night.

Current fuel cell technology is far more advanced than the Shuttle's cells - PEM (Proton Exchange Membrane) cells produce considerably less heat (requiring smaller, lighter radiators) and are physically lighter - more economical to launch from Earth. For an initial colony or base, the Shuttle's fuel cells would be more than satisfactory.

[edit] Transport

[edit] Earth to Moon

Conventional rockets have been used for most lunar exploration to date. The ESA's SMART-1 mission from 2003 to 2006 used Hall effect thrusters. NASA will use chemical rockets on its Ares V booster and Lunar Surface Access Module, being developed for a planned return to the Moon around 2021. The construction workers, location finders, and other astronauts vital to building, will be taken in NASA's Orion.

[edit] On the surface

Lunar colonists will want the ability to move over long distances, to transport cargo and people to and from modules and spacecraft, and to be able to carry out scientific study of a larger area of the lunar surface for long periods of time. Proposed concepts include a variety of vehicle designs, from small open rovers to large pressurised modules with lab equipment, and also a few flying or hopping vehicles.

Rovers could be useful if the terrain is not too steep or hilly. The only rovers that operated on the surface of the Moon as of 2004 were the Apollo Lunar Roving Vehicle (LRV), developed by Boeing and the unmanned Soviet Lunokhod. The LRV was an open rover for a crew of two, and a range of 92 km during one lunar day. One NASA study resulted in the Mobile Lunar Laboratory concept, a manned pressurised rover for a crew of two, range would be 396 km. The Soviet Union developed different rover concepts in the Lunokhod series and the L5 for possible use on future manned missions to the Moon or Mars. These rover designs were all pressurised for longer missions.^[19]

Once multiple bases have been established on the lunar surface, they can be linked together by permanent railway systems. Both conventional and magnetic levitation (Mag-Lev) systems have been proposed for the transport lines. Mag-Lev systems are particularly attractive as there is no atmosphere on the surface to slow down the train, so the vehicles could achieve velocities comparable to aircraft on the Earth. One significant difference with lunar trains, however, is that the cars will need to be individually sealed and possess their own life support systems. The trains will also need to be highly resistant to derailment, as a punctured car could lead to rapid loss of life.

For difficult areas, it might be a good idea to use a flying vehicle. Bell Aerosystems proposed their design for the Lunar Flying Vehicle as part of a study for NASA. Bell also developed the Manned Flying System, a similar concept.

[edit] Surface to space

A lunar base will need efficient ways to transport people and goods of various kinds between the Earth and the Moon and, later, to and from various locations in interplanetary space. One advantage of the Moon is its relatively weak gravity field, making it easier to launch goods from the Moon than from the Earth. The lack of a lunar atmosphere is both an advantage and a disadvantage; while it is easier to launch from the Moon because there is no drag, aerobraking is not possible, which makes it necessary to bring extra fuel in order to land. An alternative, which may work for supplies, is to surround the payload with impact-absorbing materials, something that was tried in the Ranger program. This can be efficient if the impact protection is made of needed lighter elements that are absent from the Moon (Ranger used balsa wood).

One way to get materials and products from the Moon to an interplanetary waystation might be with a mass driver, a magnetically accelerated rail. Cargo would be picked up from orbit or an Earth-Moon Lagrangian point by a shuttle craft using ion propulsion, solar sails or other means and delivered to Earth orbit or other destinations such as near-Earth asteroids, Mars or other planets, perhaps using the Interplanetary Transport Network. If a lunar space elevator ever proves practical, it could transport people, raw materials and products to an orbital station at Lagrangian points L1 or L2. A "Pop Gun" concept has also been proposed, using heated gas to launch packets of material to orbit.

[edit] Surface to and from cislunar space

A cislunar transport system has been proposed using tethers to achieve momentum exchange^[20]. This system requires zero net energy input, and could not only retrieve payloads from the lunar surface and transport them to Earth, but could also soft land payloads on to the lunar surface.

[edit] Economic development

For long term sustainability, a space colony should be close to self sufficient. On site mining and refining of the Moon's materials could provide an advantage over deliveries from Earth – for use both on the Moon and elsewhere in the solar system – as they can be launched into space at a much lower energy cost than from Earth. It is possible that vast sums of money will be spent in interplanetary exploration in the 21st century, and the cost of providing goods from the Moon might be attractive^{[citation needed]}.

[edit] Space based materials processing

In the long term, the Moon is likely to be very important in supplying zero gravity factories with raw materials^{[citation needed]}. By taking advantage of uninterrupted solar power, and a microgravity environment, stations in orbit around the Sun, either ahead of, or behind, the Earth could become the economic powerhouses of space exploration^{[citation needed]}. Zero gravity allows materials to be processed in ways impossible on Earth, such as 'foaming' metals, where a gas is injected into a molten metal, and then the metal is annealed slowly. On Earth, the gas bubbles rise and burst, but in a zero gravity environment, that does not happen. Annealing is a process that requires large amounts of energy, as a material is kept very hot for an extended period of time. This allows the molecular structure to align in the strongest possible way. Materials which cannot be alloyed or mixed on Earth because of the gravity field effects on density differences could be combined in space, resulting in composites which could have exceptional qualities. No one knows, because no one has been able to experiment along these lines on any scale. However, it is possible that a material or process will be identified which will be highly valuable on Earth, but impossible to make here.

[edit] Exporting material to Earth

Exporting material to Earth in trade from the Moon is more problematic due to the high cost of transportation. One suggested candidate is Helium-3 from the solar wind, which has accumulated on the Moon's surface over billions of years, and which is rare on Earth. Helium is present in the lunar regolith in quantities of ten to a hundred (weight) parts per million, and 0.003 to 1 percent of this amount (depending on soil). 2006 market price for He3 was about $46,500 per troy ounce ($1500/gram, $1.5M/kg), more than 120 times the value per unit weight of Gold and over eight times the value of Rhodium.

In the long term future He3 may prove to be a desirable fuel in thermonuclear fusion reactors.

Gerald Kulcinski's group at the Fusion Technology Institute of the University of Wisconsin-Madison has operated an experimental He3 fusion reactor for an extended period, on a non-governmental research budget^[21], however the reactor has not achieved energy balance or breakeven. Commercial He3 reactors are long way in the future.

[edit] Tourism

Other economic possibilities include the tourism industry; manufacturing that requires a sterile, low-gravity environment in a vacuum; research and processing of potentially dangerous life forms or nanotechnology, and long-term storage of radioactive materials. The low gravity may find health uses such as allowing the physically disabled to continue to enjoy an active lifestyle. Large, pressurized domes or caverns would permit human-powered flight, which may result in new sports activities.

[edit] Technology spin off

Technology developed for a Lunar colony would likely have application to other potential space venues, including near-Earth asteroids and Mercury, which has many similarities to the Moon. See Colonization of Mercury.

[edit] Solar power satellites

Gerard O'Neill, noting the problem of high launch costs in the early 1970s, came up with the idea of building Solar Power Satellites in orbit with materials from the Moon.^[22] Launch costs from the Moon are about 100 times lower than from Earth, due to the lower gravity. This 1970s proposal was predicated on the then advertised future launch costs of NASA's space shuttle.

On 30 April 1979 the Final Report "Lunar Resources Utilization for Space Construction" by General Dynamics Convair Division under NASA contract NAS9-15560 concluded that use of lunar resources would be cheaper than terrestrial materials for a system comprising as few as thirty Solar Power Satellites of 10GW capacity each.^[23]

In 1980, when it became obvious NASA's launch cost estimates for the space shuttle were grossly optimistic, O'Neill et al published another route to manufacturing using lunar materials with much lower startup costs ^[24] This 1980s SPS concept relied less on human presence in space and more on partially self-replicating systems on the lunar surface under telepresence control of workers stationed on Earth.

[edit] See also

[edit] References

[edit] External links

• Science Magazine The Clementine Bistatic Radar Experiment. Retrieved December 18, 2004.
• Space Daily Lunar Polar Ice Not Found With Arecibo Radar. Retrieved December 18, 2004.
• NASA Ames Research Center EUREKA! ICE FOUND AT LUNAR POLES. Retrieved December 18, 2004.
• Cornell News Arecibo radar shows no evidence of thick ice at lunar poles (...). Retrieved December 18, 2004.
• NASA Johnson Space Centre Liftoff! Moon Base Alpha. Last checked January 20, 2005.
• Encyclopedia Astronautica Subcategory: - Manned - Lunar rover - . Retrieved December 20, 2004.
• DigitalSpace Concepts A Multi-Function "Service Station" for Lunar Telerobotic Base Preparation. Checked January 29, 2006.
• The vision for space exploration, NASA.
• How Stuff Works - What if we lived on the moon? Retrieved 15 March 2007.