Space settlement

No space settlement has been constructed yet, but many design concepts, with varying degrees of realism, have been introduced in science-fiction or proposed for actual realization.

Dandridge M. Cole in the late 1950s and 1960s speculated about hollowing out asteroids and then rotating the to use as settlements in various magazine articles and books, notably Islands In Space: The Challenge Of The Planetoids.

[11] Around 1970, near the end of Project Apollo (1961–1972), Gerard K. O'Neill, an experimental physicist at Princeton University, was looking for a topic to tempt his physics students, most of them freshmen in engineering.

Also, the students solved problems such as radiation protection from cosmic rays (almost free in the larger sizes), getting naturalistic Sun angles, provision of power, realistic pest-free farming and orbital attitude control without reaction motors.

O'Neill did not emphasize the building of solar power satellites as such, but rather offered proof that orbital manufacturing from lunar materials could generate profits.

One of the early projects, for instance, involved a series of functional prototypes of a mass driver, the essential technology for moving ores efficiently from the Moon to space colony orbits.

[21] This energy can be used to produce electricity from solar cells or heat engine based power stations, process ores, provide light for plants to grow and to warm space settlements.

[15] There is estimated to be enough material in the main asteroid belt alone to build enough space settlements to equal the habitable surface area of 3,000 Earths.

[22] A 1974 estimate assumed that collection of all the material in the main asteroid belt would allow habitats to be constructed to give an immense total population capacity.

[12] If a large area at the rotation axis is enclosed, various zero-g sports are possible, including swimming,[23][24] hang gliding[25] and the use of human-powered aircraft.

The physical as well as socio-political architecture of a space settlement, if poorly established, can lead to tyrannical and precarious conditions.

[4] Even the smallest of the settlement designs mentioned below are more massive than the total mass of all items that humans have ever launched into Earth orbit combined.

[citation needed] Prerequisites to building settlements are either cheaper launch costs or a mining and manufacturing base on the Moon or other body having low delta-v from the desired habitat location.

A more modern proposal is to use a two-to-one resonance orbit that alternately has a close, low-energy (cheap) approach to the Moon, and then to the Earth.

[citation needed] If a space settlement is located at L4 or L5, then its orbit will take it outside of the protection of the Earth's magnetosphere for approximately two-thirds of the time (as happens with the Moon), putting residents at risk of proton exposure from the solar wind (see Health threat from cosmic rays).

The standard method used on nuclear submarines, a similar form of closed environment, is to use a catalytic burner, which effectively decomposes most organics.

Further protection might be provided by a small cryogenic distillation system which would gradually remove impurities such as mercury vapor, and noble gases that cannot be catalytically burned.

The small fraction of remaining materials, well below 0.01% by weight, could be processed into pure elements with zero-gravity mass spectrometry, and added in appropriate amounts to the fertilizers and industrial stocks.

Long-term on-orbit studies have proven that zero gravity weakens bones and muscles, and upsets calcium metabolism and immune systems.

[citation needed] Turning one's head rapidly in such an environment causes a "tilt" to be sensed as one's inner ears move at different rotational rates.

In any of these cases, strong meteoroid protection is implied by the external radiation shell ~4.5 tonnes of rock material, per square meter.

[34] Note that Solar Power Satellites are proposed in the multi-GW ranges, and such energies and technologies would allow constant radar mapping of nearby 3D space out-to arbitrarily far away, limited only by effort expended to do so.

The original O'Neill design used the two cylinders as momentum wheels to roll the colony, and pushed the sunward pivots together or apart to use precession to change their angle.

For a long-term habitation, however, radiation shielding must rotate with the habitat, and is extremely heavy, thus requiring a much stronger and heavier cable.

Each stage of growth shares more radiation shielding and capital equipment, increasing redundancy and safety while reducing the cost per person.

The ISS Centrifuge Demo was proposed in 2011 as a demonstration project for an artificial gravity compartment, preparatory for a similar module of a Nautilus-X Multi-Mission Space Exploration Vehicle (MMSEV).

The partial-g torus-ring centrifuge would utilize both standard metal-frame and inflatable spacecraft structures and would provide 0.11 to 0.69g if built with the 40 feet (12 m) diameter option.