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Space colonization, also called space settlement and space humanization, is the concept of permanent autonomous (self-sufficient) human habitation of locations outside Earth. The first step is the permanent human presence in space, as with the International Space Station.

It is a major theme in former science fiction and nowadays science.

While most people think of space colonies on the Moon or Mars, others argue that the first colonies will be in orbit (see International Space Station). Several design groups at NASA and elsewhere have examined orbital colony feasibility. They have determined that there are ample quantities of all the necessary materials on the Moon and Near Earth Asteroids, that solar energy is readily available in very large quantities, and that no new scientific breakthroughs are necessary, although a great deal of engineering would be required.

Current NASA chief Michael Griffin has identified space colonization as the ultimate goal of current spaceflight programs, saying:

"...the goal isn't just scientific exploration... it's also about extending the range of human habitat out from Earth into the solar system as we go forward in time. . . . In the long run a single-planet species will not survive... If we humans want to survive for hundreds of thousands or millions of years, we must ultimately populate other planets. Now, today the technology is such that this is barely conceivable. We're in the infancy of it... I'm talking about that one day, I don't know when that day is, but there will be more human beings who live off the Earth than on it. We may well have people living on the moon. We may have people living on the moons of Jupiter and other planets. We may have people making habitats on asteroids... I know that humans will colonize the solar system and one day go beyond." *

Method

Building colonies in space will require people, food, construction materials, energy, transportation, communications, life support, gravity (acceleration), and radiation protection. Colonies will presumably be situated to help optimise access to these resources.

Materials

Colonies on the Moon and Mars could use local materials, although the Moon is deficient in hydrogen, carbon and nitrogen. For orbital colonies, launching materials from Earth is very expensive, so bulk materials could come from the Moon or Near-Earth Objects (NEOs - asteroids and comets with orbits near Earth), Phobos, or Deimos where gravitational forces are much less, there is no atmosphere, and there is no biosphere to damage. Our Moon has large amounts of oxygen, silicon and metals, but little hydrogen, carbon, or nitrogen. NEOs contain substantial amounts of metals, oxygen, hydrogen and carbon. NEOs also contain some nitrogen, but not necessarily enough to avoid major supplies from Earth.

Energy

Solar energy in orbit is abundant, reliable and is commonly used to power satellites today. There is no night in space, and no clouds or atmosphere to block sunlight. The solar energy available, in watts per square meter, at any distance, d, from the Sun can be calculated by the formula E = 1366/d2, where d is measured in astronomical units.

Particularly in the weightless conditions of space, sunlight can be used directly, using solar ovens made of lightweight metallic foil so as to generate thousands of degrees of heat at no cost; or reflected onto crops to enable photosynthesis to proceed.

Large structures would be needed to convert sunlight into significant amounts of electrical power for settlers use. On Earth people use on average roughly 2-6 kilowatts per person.

Energy might be an export item for space settlements, perhaps using microwave beams to send power to Earth or the Moon.

The Moon has nights of two Earth weeks in duration and Mars has night, dust, and is farther from the Sun, reducing solar energy available by a factor of about 1/2.3, and possibly making nuclear power more attractive on these bodies.

For both solar thermal and nuclear power generation in airless environments, such as the Moon and space, and to a lesser extant the very thin Martian atmosphere, one of the main difficulties is dispersing the inevitable heat generated. This requires fairly large radiator areas.

Transportation

Space Access
Transportation to orbit is often the limiting factor in space endeavors. Present-day launch costs are very high - $5,000 to $ 30,000 per kilogram from Earth to Low Earth Orbit (LEO). To settle space, we need much better launch vehicles and must avoid serious damage to the atmosphere from the thousands, perhaps millions, of launches required. One possibility is air-breathing hypersonic air/spacecraft under development by NASA and other organizations, both public and private. There are also proposed projects to build a space elevator.

Cislunar and Solar System travel

Transportation of large quantities of materials from the Moon, Phobos, Deimos, and Near Earth asteroids to orbital settlement construction sites is likely to be necessary.

Transportation using off-Earth resources for propellant in relatively conventional rockets would be expected to massively reduce in-space transportation costs compared to the present day; propellant launched from the Earth is likely to be prohibitively expensive for space colonization, even with improved space access costs.

Other technologies such as tether propulsion, VASIMR, Ion drives, Solar thermal rockets, Solar Sails, and Nuclear thermal propulsion can all potentially help solve the problems of high transport cost once in space.

For lunar materials, one well-studied possibility is to build electronic catapults to launch bulk materials to waiting settlements. Alternatively, Lunar space elevators might be employed (unlike Terrestrial elevators, Lunar elevators could be built using existing technology).

Communication

Compared to the other requirements, communication is relatively easy for orbit and the Moon. Much of the current terrestrial communications already pass through satellites. Communications to Mars suffer from significant delays due to the speed of light, making voice conversation impractical. Other means of communication, such as e-mail and voice mail, should pose no problem.

Life support

People need air, water, food, gravity and reasonable temperatures to survive for long periods. On Earth a large complex biosphere provides these. In space settlements, a relatively small, closed system must recycle all the nutrients without "crashing."

The closest terrestial analogue of space life support is possibly that of Nuclear submarines. Nuclear submarines use mechanical life support systems to support humans for months without surfacing, and this same basic technology could presumably be employed for space use. However, nuclear submarines run "open loop" and typically dump carbon dioxide overboard, although they recycle oxygen. Recycling of the carbon dioxide has been approached in the literature using the Sabatier process or the Bosch reaction.

Alternatively, and more attractive to many, the Biosphere 2 project in Arizona has shown that a complex, small, enclosed, man-made biosphere can support eight people for at least a year, although there were many problems. A year or so into the two-year mission oxygen had to be replenished, which strongly suggests that they achieved atmospheric closure.

The relationship between organisms, their habitat and the non-Earth environment can be:

Note that plant based life support systems are very inefficient in their use of energy; about 1-3% energetic efficiency is common. This means that 97-99% of the light energy provided to the plant ends up as heat and needs to be dissipated somehow to avoid the temperature of the habitat going too high.

A combination of the above technologies is also possible.

Radiation protection

Cosmic rays and solar flares create a lethal radiation environment in space. In Earth orbit, the Van Allen belts make living above the Earths atmosphere difficult. To protect life, settlements must be surrounded by sufficient mass to absorb most incoming radiation. Somewhere around 5-10 tons of material per square meter of surface area is required. This can be achieved cheaply with leftover material (slag) from processing lunar soil and asteroids into oxygen, metals, and other useful materials.

Self-replication

Self-replication is an optional attribute, but many think it the ultimate goal because it allows a much more rapid increase in colonies, while eliminating costs to and dependence on Earth. It could be argued that the establishment of such a colony would be Earth's first act of self-replication. Intermediate goals include colonies that expect only information from Earth (science, engineering, entertainment, etc.) and colonies that just require periodic supply of light weight objects, such as integrated circuits, medicines, genetic material and perhaps some tools.

See also: von Neumann probe, clanking replicator, Molecular nanotechnology

Population size

In 2002, the anthropologist John H. Moore estimated that a population of 150–180 would allow normal reproduction for 60 to 80 generations—equivalent to 2000 years.

A much smaller initial population of two female humans should be viable as long as human embryos are available from Earth. Use of a sperm bank from Earth also allows a smaller starting base with negligible inbreeding.

Researchers in conservation biology have tended to adopt the "50/500" rule of thumb initially advanced by Franklin and Soule. This rule says a short-term effective population size (Ne) of 50 is needed to prevent an unacceptable rate of inbreeding, while a long‐term Ne of 500 is required to maintain overall genetic variability. The N_e = 50 prescription corresponds to an inbreeding rate of 1% per generation, approximately half the maximum rate tolerated by domestic animal breeders. The N_e = 500 value attempts to balance the rate of gain in genetic variation due to mutation with the rate of loss due to genetic drift.

Effective population size Ne depends on the number of males Nm and females Nf in the population according to the formula:

N_e = \frac{4 \times N_m \times N_f} {N_m + N_f}

Laws and law fiction

International space citizens would be submitted to the International law (i.e. the Moon is a res communis). In the future, they can have double nationality (terrestrial nationality and moon nationality). See Outer Space Treaty.

Location

Location is a frequent point of contention between space colonization advocates.

The location of colonization can be:

Planetary Locations

Planetary colonization advocates cite the following potential locations:

Mars

Mars is a frequent topic of discussion. Its overall surface area is similar to the dry land surface Earth, it may have large water reserves, and has carbon (locked as carbon dioxide in the atmosphere).

Mars may have gone through similar geological and hydrological processes as Earth and contain valuable mineral ores, but this is debated. Equipment is available to extract in situ resources (water, air, etc.) from the Martian ground and atmosphere. There is a strong scientific interest in colonizing Mars due to the possibility that life could have existed on Mars at some point in its history, and may even still exist in some parts of the planet.

However, its atmosphere is very thin (averaging 800 Pa or about 0.8% of Earth sea-level atmospheric pressure); so the pressure vessels necessary to support life are very similar to deep space structures. The climate of Mars is colder than Earths. Its gravity is only around a third that of Earth, it is unknown whether this is sufficient to support human beings for long periods (all long term human experience to date has been at 100% Earth gravity or zero-g).

The atmosphere is thin enough, when coupled with Mars' lack of magnetic field, that radiation is more intense on the surface, and protection from solar storms would require radiation shielding.

Mars is often the topic of discussion regarding terraforming to make the entire planet or at least large portions of it habitable.

See also: Exploration of Mars, Martian terraforming

Mercury

There is a suggestion that Mercury could be colonized using the same technology, approach and equipment that is used in colonization of the Moon. Such colonies would almost certainly be restricted to the polar regions due to the extreme daytime temperatures elsewhere on the planet.

Venus

While the surface of Venus is far too hot and features atmospheric pressure at least 90 times that at sea level on Earth, its massive atmosphere offers a possible alternate location for colonization. At a height of approximately 50 km, the pressure is reduced to a few atmospheres, and the temperature would be between 40-100° C, depending on the height. This part of the atmosphere is probably within dense clouds which contain some sulfuric acid. Even these may have a certain benefit to colonization, as they present a possible source for the extraction of water.

See also: Venusian terraforming

Gas Giants

It may also be possible to colonize the three furthest gas giants with floating cities in their atmospheres. By heating hydrogen balloons large masses can be suspended underneath at roughly Earth gravity. Jupiter would be less suitable for habitation due to its high gravity, escape velocity and radiation. Such colonies could export Helium-3 for use in fusion reactors if they ever become practical.

Satellite locations

The Moon

Due to its proximity and relative familiarity, Earth's Moon is also frequently discussed as a target for colonization. It has the benefits of close proximity to Earth and lower escape velocity, allowing for easier exchange of goods and services. A major drawback of the Moon is its low abundance of volatiles necessary for life such as hydrogen and carbon. Water ice deposits thought to exist in some polar craters could serve as significant sources for these elements. An alternative solution is to bring hydrogen from Earth and combine it with oxygen from the Moon. Structural components of supply craft could be made of hydrogen-rich plastics.

The moon's low surface gravity is also a concern (it is unknown whether 1/6g is sufficient to support human habitation for long periods - see microgravity -).

Europa

The Artemis Project designed a plan to colonize Europa, one of Jupiter's moons. Scientists were to inhabit igloos and drill down into the Europan ice crust, exploring any sub-surface ocean. This plan also discusses possible use of "air pockets" for human inhabitation.

See also: Colonization of the outer solar system

Phobos and Deimos

Phobos may possess water in the form of ice. Due to the low delta-v needed to reach the Earth, this would permit delivery of propellant and other materials to cis-lunar space as well as transport around the Martian system. This makes these locations economically advantageous, since it is within easy reach of much of the solar system, as they have resources at a high potential energy. Phobos and Deimos themselves are probably suitable for sourcing materials for production of space habitats, or for living within.

Free Space Locations

Space habitats

Free space locations in space would necessitate a space habitat, also called space colony and orbital colony, or a space station which would be intended as a permanent settlement rather than as a simple waystation or other specialized facility. They would be literal "cities" in space, where people would live and work and raise families. Many design proposals have been made with varying degrees of realism by both science fiction authors and engineers.

A space habitat would also serve as a proving ground for how well a generation ship could function as a long-term home for hundreds or thousands of people. Such a space habitat could be isolated from the rest of humanity for a century, but near enough to Earth for help. This would test if thousands of humans can survive a century on their own before sending them beyond the reach of any help.

See also: Orbital Megastructures

Earth orbit

Compared to other locations, Earth orbit has substantial advantages and one major, but solvable, problem. Orbits close to Earth can be reached in hours, whereas the Moon is days away and trips to Mars take months. There is ample continuous solar power in high Earth orbits, whereas all planets lose sunlight at least half the time. Weightlessness makes construction of large colonies considerably easier than in a gravity environment. Astronauts have demonstrated moving multi-ton satellites by hand. 0g recreation is available on orbital colonies, but not on the Moon or Mars. Finally, the level of (pseudo-) gravity is controlled at any desired level by rotating an orbital colony. Thus, the main living areas can be kept at 1g, whereas the Moon has 1/6g and Mars 1/3g. It's not known what the minimum g-force is for ongoing health but 1g is known to ensure that children grow up with strong bones and muscles.

The main disadvantage of orbital colonies is lack of materials. These must be imported from the Moon, which has ample metals, silicon, and oxygen, or Near Earth Asteroids, which have all the materials needed with the possible exception of nitrogen.

Lagrange points

Another near-Earth possibility are the five Earth-Moon Lagrange points. Although they would generally also take a few days to reach with current technology, many of these points would have near-continuous solar power capability since their distance from Earth would result in only brief and infrequent eclipses of light from the Sun.

The five Earth-Sun Lagrange points would totally eliminate eclipses, but only L1 and L2 would be reachable in a few days' time. The other three Earth-Sun points would require months to reach.

However, the fact that Lagrange points tend to collect dust and debris, as well as requiring active station-keeping measures to maintain a stable position, make them somewhat less suitable places for habitation than was originally believed.

The Asteroids

Many small asteroids in orbit around the Sun have the advantage that they pass closer than Earth's moon several times per decade. In between these close approaches to home, the asteroid may travel out to a furthest distance of some 350,000,000 kilometers from the Sun (its aphelion) and 500,000,000 kilometers from Earth.

Disadvantages are a lack of significant gravity, and inability to support a sizeable population; thus self sufficiency may be far in the future on/in very small asteroids. Unmanned supply craft should be practical with little technological advance even crossing 1/2 billion kilometers of cold vacuum. The colonists would have a strong interest in assuring that their asteroid did not hit Earth or any other body of significant mass.

Outside the Solar system

Colonization of the entire Solar system would take hundreds or thousands of years. Looking beyond our solar system, there are billions of potential suns with possible colonization targets. This topic begins to exceed the scope of encyclopedia articles and enters the realm of science fiction. Even there, however, some work has been done to explore the possibilities.

Starship

An interstellar colony ship would be similar to a space habitat, except with major propulsion capabilities and independent power generation.

Concepts proposed in hard science fiction include:

Example

The star Tau Ceti, about eleven light years away, has an abundance of cometary and asteroidal material in orbit around it. These materials could be used for the construction of space habitats for human settlement.

Terrestrial analogues to space colonies

The most famous attempt to build an analogue to a self-sufficient colony is Biosphere 2, which attempted to duplicate Earth's biosphere.

Many space agencies build testbeds for advanced life support systems, but these are designed for long duration human spaceflight, not colonization.

Remote research stations in inhospitable climates, such as the Amundsen-Scott South Pole Station or Devon Island Mars Arctic Research Station, can also provide some practice for off-world outpost construction and operation. The Mars Desert Research Station has a habitat for similar reasons, but the surrounding climate is not strictly inhospitable.

Justification

In 2001, the space news website SPACE.com asked Freeman Dyson, J. Richard Gott and Sid Goldstein for reasons why some humans should live in space. Their respective answers * were:

Louis J. Halle, formerly of the United States Department of State, wrote in Foreign Affairs (Summer 1980) that the colonization of space will protect humanity in the event of global nuclear warfare. *

The scientist Paul Davies also supports the view that if a planetary catastrophe threatens the survival of the human species on Earth, a self-sufficient colony could "reverse-colonize" the Earth and restore human civilization.

The author and journalist William E. Burrows and the biochemist Robert Shapiro proposed a private project, the Alliance to Rescue Civilization, with the goal of establishing an off-Earth backup of human civilization.

Another important reason used to justify Space is the effort to increase the knowledge and technological abilities of Humanity.

Advocacy

Space advocacy organizations:

Objections

There are many who object to the idea of colonizing space as being too expensive and a waste of time. There is nothing in space that we really need, they say, adding that moving beyond the solar system is totally impractical in any reasonable time scale.

The pragmatic argument to 'live together on the earth we have' is a powerful one, suggesting that if even half the money of space exploration were spent for terrestrial betterment, there would be greater good for a greater number of people, at least in the short term.

The anti-space arguments have gone so far as to suggest that space colonization is a remnant of historical colonization - it is (the idea at least) a lingering desire left over from a romanticized notion of the 'founding fathers' and the conquest of territory on earth. As such, the argument goes, space exploration wins the hearts and minds of voters but does little else. Worse still, it could be said that the objective of colonizing space adds fuel to the patriotic dogma of conquest, and thus reinforces negative national prejudice rather than helping to unify earth.

As an alternative for the future of the human race, many science fiction writers have instead focused on the realm of the 'inner-space', that is the (computer aided) exploration of the human mind and human consciousness. Perhaps one example of this trend is the popular movie The Matrix, where all the action takes place on (under the surface of) Earth, and in a computer generated reality in cyberspace.

Counter Arguments

The argument of cost: Very many people greatly overestimate how much money is spent on space, and underestimate how much money is spent on defense or health care. For example, as of June 13, 2006, over $320 billion has been allocated by the US Congress for the current war in Iraq, in comparison it only cost $2 billion to create the Hubble Space Telescope, and NASA's yearly budget averages only about $15 billion a year, in other words the money that has been spent on the Iraq war could have funded NASA for approximately 21 years. They also underestimate the extent that space technologies such as communications and weather satellites help them in their everyday lives. This argument also assumes that money not spent on space would automatically be spent in ways that would benefit humanity.

The argument of Nationalism: Space proponents counter this argument by pointing out that humanity as a whole has been exploring and expanding into new territory since long before Europe's colonial age, going back into prehistory; that seeing the Earth as a single, discrete object instills a powerful sense of the smallness and connectedness of the human environment and of the immateriality of political borders; and that in practice, international collaboration in space has shown its value as a unifying and cooperative endeavor. Pale Blue Dot: A Vision of the Human Future in Space, Carl Sagan

The argument of 'Inner Space': This form of exploration need not be exclusive to space colonization, as exemplified by Transhumanist philosophies.

See also

References

External links

Space colonization | Space exploration

Colonización del Espacio | Kolonisasi angkasa | Colonizzazione dello spazio | מושבת חלל | 宇宙移民 | Colonização espacial | Колонизация космоса | Avaruuden kolonisaatio | 宇宙殖民地

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Space colonization".

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