Colonization of the Moon

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An artist's rendering of a lunar base. (NASA)

Permanent human habitation on a planetary body other than the Earth is a central theme in science fiction. As technology has improved and concerns about the future of humanity on Earth increase, some argue that space colonization is an achievable and worthwhile goal. Because of its proximity to Earth and the early telescopic observation of familiar land forms, such as mountains and plains, the Moon has long been seen as a candidate for a possible human colony in space. However, the Apollo program, while demonstrating the feasibility of travel to the Moon (albeit at a high cost), dampened enthusiasm for such a lunar colony because rock and dirt samples brought back by astronauts proved extremely low in the lighter elements required as a condition for life.

Many space colonization advocates have since turned their attention to Mars, which has a more Earth-like environment, but others continue to believe that the Moon is a logical first step. The possibility of clean fusion power from Helium 3 fuel mined on the Moon is cited by some as a potential economic justification for a lunar base. NASA's long range Vision for Space Exploration plan includes a return to the Moon.

History

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

Noted science author Arthur C. Clarke proposed a lunar base of inflatable modules covered in lunar dust for insulation in 1954. A spaceship, assembled in low Earth orbit, would be launched towards the Moon. It would land on Mare Imbrium, near Mons Piton, 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 electronmagnetic cannons to launch cargo and fuel to interplanetary vessels in space.[1] (http://www.marsinstitute.info/rd/faculty/dportree/rtr/ft01.html)

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 was, at the time this concept was outlined, theories that there could be mile-deep dust oceans on the Moon. The design proposed consisted of a half-cylinder with half-domes at both ends. A micrometeoroid shield is then placed above the base. [2] (http://www.marsinstitute.info/rd/faculty/dportree/rtr/ft04.html)

The Project Horizon was a 1959 study regarding the U.S. Army's plan to establish a fort on the Moon by 1967. 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. [3] (http://www.marsinstitute.info/rd/faculty/dportree/rtr/ft05.html)

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 aggressive russian 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. 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 favoured 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 could be useful. [4] (http://www.marsinstitute.info/rd/faculty/dportree/rtr/ft07.html)

Manned exploration of lunar surface began in 1968 when the Apollo 8 spacecraft orbited the Moon with three astronauts on board. This was humankind'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 the Apollo 13, the Apollo 14 was 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. The Apollo 16 made first landing among the rugged lunar highlands.

However, interest in further exploration of the Moon was beginning to wane among the American public. The 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. Apparently 1974 saw the scuppering of the Soviet Moonshot, two years after 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 rekindled some discussion, as did the potential growth of a Chinese space program that contemplated its own mission to the Moon.

Spurred by the prospect of a Chinese lunar base, in 2004, US 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.

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.

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. Some proposals include using electric acceleration devices to propel objects off the Moon without building rockets. Nonetheless, the Moon does have significant gravity, which, experience to date indicates, may be vital for long-term human health.

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 of 384,400 km. This proximity has several benefits:

The energy (or delta V) required to send objects from Earth to the Moon is lower than for most other bodies.
Transit time is short. The Apollo astronauts made the trip in three days. Earth-crossing asteroids require somewhat less energy, but the months of travel required would necessitate a safe habitat for humans that would more than offset any savings.
The short transit time would also allow emergency supplies to reach a Moon colony from Earth in a short time. This could be an important consideration when establishing the first human colony.
The round trip communication delay to Earth is only a few seconds, allowing direct voice and video communications. The delay for other solar system bodies would be measured in minutes or hours. This again would be of particular value in an early colony, where life-threatening problems requiring Earth's assistance would be expected to occur. (See, for example: Apollo 13)
On the lunar near side, the Earth appears large and is nearly always visible, whereas when Earth is visible at all on Mars, it is 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.

Disadvantages

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

The long lunar night would impede reliance on solar power (except, perhaps, at the polar regions) and require a colony to be designed that could withstand large temperature excursions. The sole exception to this restriction are the so-called "peaks of eternal light" located at the lunar poles.
The Moon lacks the light elements (volatiles) that are needed for life, though there is some evidence of hydrogen near the north and south poles. Volatiles would need to be imported, perhaps eventually from the outer planets, but from Earth initially. This would limit the colony's rate of growth and keep it dependent on Earth. However, 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.
There is continuing uncertainty over whether the low 1/6 g gravity on the Moon is strong enough to prevent detremental effects to human health in the long term. Exposure to weightlessness over month-long periods has been demonstrated to cause deterioration of physiological systems, such as loss of bone and muscle mass. Similar effects could occur in a low gravity environment.
The lack of a substantial atmosphere for insulation, which also results in temperature extremes, and makes the Moon's surface conditions somewhat like a deep space vacuum.

Locations

Russian astronomer Vladislav V. Shevchenko proposed in 1988 three criteria that a lunar outpost should meet:

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.

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

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. 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. 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.
Its proximity to Shackleton Crater (116 km) 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.
The nearby Shoemaker and other craters are in constant deep shadow, and contain valuable concentrations of hydrogen. These volatiles could provide liquid water, oxygen, and rocket fuel, among many other things.
At around 5,000 metres elevation, it offers line of sight communications over a large area, as well as to Earth.
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.

At the north pole, the rim of Peary crater has been proposed as a favorable location for a base. 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). As a result the temperature conditions are expected to remain very stable at this location, averaging -50° C (-58° F). This is comparable to coastal winter conditions in Antarctica. The Peary crater interior may also harbor hydrogen deposits.

Although hydrogen appears to be concentrated at the poles, the presence of water ice has not yet been confirmed. Data from the Clementine mission suggested the presence of water ice around the south pole. [5] (http://www.cmf.nrl.navy.mil/clementine/clementine.html) [6] (http://www.sciencemag.org/cgi/content/short/274/5292/1495) This would have been detected in the large Shackleton crater near the Moon's South pole. [7] (http://www.spacedaily.com/news/lunar-03s.html) The Lunar Prospector spacecraft detected possible water ice not only at the south pole, but also at the north pole — actually more so. [8] (http://lunar.arc.nasa.gov/results/ice/eureka.htm) On the other hand, Cornell News reported the results of a radar experiment (using the Arecibo radio telescope) that did not show any hints of water on the Moon. [9] (http://www.news.cornell.edu/releases/Nov03/radar.Moonpoles.deb.html)

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. 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 is Oceanus Procellarum. Several probes have landed in that area. There are many areas and features that should be subject to long-term study, such as the Reiner Gamma anomaly and the dark-floored Grimaldi crater. Furthermore, measurements from ground-based telescopes as well as from the Zond 6 spacecraft, reveal the presence of oxygen-bearing minerals in the area.

Far side

The lunar far side lacks direct communication with Earth, though a communication satellite at the L2 Lagrangian point would cover the far side. It might be a good location for a large radio telescope because it is well shielded from the Earth. Its topography differs from the near side and there had been no ground exploration of the far side to date.

Scientists have estimated that the highest concentrations of He-3 will be found on the marias on the far side, as well as near side areas containing concentrations of the titanium-based mineral ilmenite. On the near side the Earth partially shields the surface from the solar wind during each orbit. But the far side is fully exposed, and thus should receive a greater proportion of the ion stream.

Structure

Habitat

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A lunar base with an inflatable module. Conceptual drawing. (© NASA)

There have been numerous proposals regarding the habitat modules. The designs have evolved throughout the years as humankind's knowledge about the Moon has grown, and as the technological possibilities have changed. The proposed habitats range from the actual spacecraft landers or the 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. 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. 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. As of 2004, existence of lava tubes on the Moon has not been confirmed.

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.

Energy

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

Nuclear power

A nuclear fission reactor could possibly be able to fill 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 type of fusion reactions is abundant on the Moon. However, it's possible that reliable, efficient fusion reactors will 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.

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 in situ. 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 could 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 creater near the north pole. See Peak of Eternal Light.

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 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.

Transport

On the surface

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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 (DLB Lunokhod 1-3/LEK) and the L5 for possible use on future manned missions to the Moon or Mars. These rover designs were all pressurised for longer missions.

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 can lead to rapid loss of life.

For difficult areas, it could 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.

Surface to space

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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 realtively 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's 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. 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.

Economic development

For long term sustainability, a space colony should be close to self sufficient. In situ 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 lower 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 could be attractive.

Exporting material to Earth in trade is more problematic due to the high cost of transportation. One suggested candidate is Helium-3 from the solar wind, which may have accumulated on the Moon's surface over billions of years, which may prove to be a desirable fuel in fusion reactors, and which is rare on Earth. Neither the abundance of Helium-3 on the lunar surface nor the feasibility of its use in fusion power plants have been established, however.

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 allowing the physically enfeebled to continue to enjoy an active lifestyle. Large, pressurized domes or caverns would permit human-powered flight, which may result in new sports activities.

Moon colonies in fiction and film

Moon colonies are found in many science fiction novels, short stories and films. Not all have the Moon colony itself as central to the plot. Here are some notable examples:

Books

The Moon is a Harsh Mistress, a classic science fiction novel by Robert A. Heinlein, tells the story of a lunar rebellion against control by Earth-based governments.
The short story People Came From Earth by Stephen Baxter. It can be found in The Year's Best Fantasy and Horror: Thirteenth Annual Collection.
In the novel Rendezvous with Rama by Arthur C. Clarke, a meeting is held at a lunar colony to decide how to deal with the Rama object.
The 1993 book Assemblers of Infinity by Kevin Anderson and Doug Beason featured a lunar base and a mysterious structure being assembled on the far side by tiny machines. ISBN 0-553-29921-2.
Transmigration of Souls by William Barton, published in 1996, had an expedition from a moon base discovering an alien base with technology that allowed teleportation and time travel. ISBN 0-446-60167-5.
The Moonrise and Moonwar books by Ben Bova tell the story of a lunar base built by an American corporation, which eventually rebels against Earth control. The books form part of the "Grand Tour" series.
Moonfall by Jack McDevitt features a comet heading for a collision with the Moon just as the first base is being opened. ISBN 0061050369.
In 1993, the fictional Dutch travel guide De Maan was written by Carl Koppeschaar, and later translated into English as Moon Handbook: A 21st-Century Travel Guide. ISBN 1-56691-066-8.

Television

The British television show Space: 1999 featured the Moonbase Alpha on a Moon that had been blasted out of its orbit at phenomenal velocity.
Moonbase 3 was another British science fiction television show about a lunar base that aired briefly in 1973 for 6 episodes.
Planet ES is a 2003 japanese anime film at a time when travel to the Moon has become an everyday occurance.

Film

2001: A Space Odyssey by Arthur C. Clarke included a scene at a lunar administrative base in Clavius crater.

References

Mars Institute Footholds: Outposts, Bases, and Settlements (http://www.marsinstitute.info/rd/faculty/dportree/rtr/rtr-ft.html). Retrieved December 17, 2004.
Department of the Navy Clementine (http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=2004-030A). Retrieved December 18, 2004.
Science Magazine The Clementine Bistatic Radar Experiment (http://www.sciencemag.org/cgi/content/short/274/5292/1495). Retrieved December 18, 2004.
Space Daily Lunar Polar Ice Not Found With Arecibo Radar (http://www.spacedaily.com/news/lunar-03s.html). Retrieved December 18, 2004.
NASA Ames Research Center EUREKA! ICE FOUND AT LUNAR POLES (http://lunar.arc.nasa.gov/results/ice/eureka.htm). Retrieved December 18, 2004.
Cornell News Arecibo radar shows no evidence of thick ice at lunar poles (...) (http://www.news.cornell.edu/releases/Nov03/radar.Moonpoles.deb.html). Retrieved December 18, 2004.
NASA Johnson Space Centre Liftoff! Moon Base Alpha (http://aerospacescholars.jsc.nasa.gov/HAS/cirr/em/8/1.cfm). Last checked January 20, 2005.
Encyclopedia Astronautica Subcategory: - Manned - Lunar rover - (http://www.astronautix.com/craft/mancraft.htm). Retrieved December 20, 2004.

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Categories: Moon | Space colonization