Editing Space settlement (section)

==Requirements==
[[File:Stanford torus configuration.gif|right|thumb|Configuration of a Stanford torus]]

The requirements for a space settlement are many. They would have to provide all the material needs for hundreds or thousands of humans, in an environment out in space that is very hostile to human life.<ref>{{cite journal |last1=Chen |first1=Muhao |last2=Goyal |first2=Raman |last3=Majji |first3=Manoranjan |last4=Skelton |first4=Robert E. |title=Review of space habitat designs for long term space explorations |journal=[[Progress in Aerospace Sciences]] |date=2021 |volume=122 |pages=100692 |doi=10.1016/j.paerosci.2020.100692}}</ref>

===Regulation===
The governance or regulation of space settlements is crucial for responsible habitation conditions. The physical as well as socio-political architecture of a space settlement, if poorly established, can lead to tyrannical and precarious conditions.<ref name="g324">{{cite journal | last=Cockell | first=C. S. | title=Essay on the Causes and Consequences of Extraterrestrial Tyranny | journal=Journal of the British Interplanetary Society | volume=63 | date=2010 | issn=0007-084X | pages=15–37 | url=https://ui.adsabs.harvard.edu/abs/2010JBIS...63...15C/abstract | access-date=2024-08-07}}</ref>

===Initial capital outlay===
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|date=February 2011}} 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.<ref name="Pournelle, Jerrold E. 1977"/><!--Sad to say, I don't have these at hand...but it's in there.-->

===Location===
[[File:Figure4.13, Baseline transportation system, Space Settlements, A Design Study.NASA.gif|thumb|A 1970s NASA concept for routs and locating a [[Stanford torus]] in [[cis-lunar space]]]] 
The optimal settlement orbits are still debated, and so [[orbital stationkeeping]] is probably a commercial issue. The lunar {{L4}} and {{L5}} orbits are now thought to be too far away from the Moon and Earth. 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|date=June 2018}} This provides quick, inexpensive access to both raw materials and the major market. Most settlement designs plan to use [[tether propulsion|electromagnetic tether propulsion]], or [[mass driver]]s used instead of rocket motors. The advantage of these is that they either use no reaction mass at all, or use cheap reaction mass.{{Citation needed|date=February 2011}}

===Protection from radiation===
If a space settlement is located at [[Lagrangian point#L4 and L5|L4 or&nbsp;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#Human exposure|proton exposure]] from the [[solar wind]] (see ''[[Health threat from cosmic rays]]'').

Protection can be attained through passive or active shielding.<ref name="h447">{{cite web | title=Radiation Shielding Techniques for Human Spaceflight | website=Professor Robert B. Laughlin, Department of Physics, Stanford University | date=2015-07-17 | url=http://large.stanford.edu/courses/2015/ph241/clark1/ | ref={{sfnref | Professor Robert B. Laughlin, Department of Physics, Stanford University | 2015}} | access-date=2024-08-08}}</ref> Passive shielding through the use of materials has been the method to shield current spacecrafts.

Water walls or ice walls can provide protection from solar and cosmic radiation, as 7 cm of water depth blocks approximately half of incident radiation.<ref>{{cite report|title=Water Walls Architecture: Massively Redundant andn Highly Reliable Life Support for Long Duration Exploration Missions|url=https://ntrs.nasa.gov/api/citations/20190001191/downloads/20190001191.pdf|access-date=November 13, 2022|publisher=NASA}}</ref> Alternatively, rock could be used as shielding; 4 metric tons per square meter of surface area could reduce radiation dosage to several mSv or less annually, below the rate of some populated [[background radiation|high natural background areas]] on Earth.<ref>[https://web.archive.org/web/20100531210412/http://settlement.arc.nasa.gov/75SummerStudy/5appendE.html "Mass Shielding"], Appendix E, ''Space Settlements: A Design Study''. NASA (SP-413), 1975.</ref>

Alternative concepts based on active shielding are untested yet and more complex than such passive mass shielding, but usage of magnetic and/or electric fields, like through spacecraft encapsulating wires,<ref name="z986">{{cite web | last=Williams | first=Matt | title=Plans for a modular Martian base that would provide its own radiation shielding | website=Phys.org | date=2018-10-17 | url=https://phys.org/news/2018-10-modular-martian-base-shielding.html | access-date=2024-08-08}}</ref> to deflect particles could potentially greatly reduce mass requirements.<ref name = spacecraftshielding>{{cite web | url= http://engineering.dartmouth.edu/~simon_g_shepherd/research/Shielding/ | title= Spacecraft Shielding | author= Shepherd, Simon George | website= dartmouth.edu | publisher= Thayer School of Engineering, Dartmouth College | access-date= 3 May 2011}}</ref>

===Atmosphere===
[[File:Cupola above the darkened Earth.jpg|thumb|The [[airglow]] above the horizon at the atmospheric and orbital [[Outer space#Boundary|boundary to space]], captured from the [[International Space Station|ISS]]]]
Air [[pressure]], with normal partial pressures of [[oxygen]] (21%), [[carbon dioxide]] and [[nitrogen]] (78%), is a basic requirement of any space settlement. Basically, most space settlement designs concepts envision large, thin-walled pressure vessels. The required oxygen could be obtained from lunar rock. Nitrogen is most easily available from the Earth, but is also recycled nearly perfectly. Also, nitrogen in the form of ammonia ([[ammonia|{{chem|NH|3}}]]) may be obtainable from comets and the moons of outer planets. Nitrogen may also be available in unknown quantities on certain other bodies in the [[outer Solar System]]. The air of a habitat could be recycled in a number of ways. One concept is to use [[photosynthesis|photosynthetic]] [[gardening|garden]]s, possibly via [[hydroponics]], or [[forest gardening]].{{Citation needed|date=November 2009}} However, these do not remove certain industrial pollutants, such as volatile oils, and excess simple molecular gases. 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 (element)|mercury]] vapor, and noble gases that cannot be catalytically burned. {{Citation needed|date=November 2009}}

===Food production===
[[Organic chemistry|Organic]] materials for food production would also need to be provided. At first, most of these would have to be imported from Earth. {{cn|date=January 2018}} After that, feces recycling should reduce the need for imports.{{cn|date=January 2018}} One proposed recycling method would start by burning the cryogenic distillate, plants, garbage and sewage with air in an electric arc, and distilling the result.{{Citation needed|date=November 2009}} The resulting carbon dioxide and water would be immediately usable in agriculture. The nitrates and salts in the ash could be dissolved in water and separated into pure minerals. Most of the nitrates, potassium and sodium salts would recycle as fertilizers. Other minerals containing iron, nickel, and silicon could be chemically purified in batches and reused industrially. 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. It is likely that methods would be greatly refined as people began to actually live in space settlements.

===Artificial gravity===
{{Main|Artificial gravity}}
{{unreferenced section|date=February 2011}}
Long-term on-orbit studies have proven that zero gravity weakens bones and muscles, and upsets calcium metabolism and immune systems. Most people have a continual stuffy nose or sinus problems, and a few people have dramatic, incurable motion sickness. Most habitat designs would rotate in order to use [[inertia]]l forces to [[Artificial gravity|simulate gravity]]. NASA studies with chickens and plants have proven that this is an effective physiological substitute for gravity.{{Citation needed|date=November 2009}} 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. Centrifuge studies show that people get motion-sick in habitats with a rotational radius of less than 100 metres, or with a rotation rate above 3 rotations per minute. However, the same studies and statistical inference indicate that almost all people should be able to live comfortably in habitats with a rotational radius larger than 500 meters and below 1 RPM. Experienced persons were not merely more resistant to motion sickness, but could also use the effect to determine "spinward" and "antispinward" directions in the centrifuges.{{Citation needed|date=November 2009}}

===Meteoroids and dust===
The habitat would need to withstand potential impacts from [[space debris]], [[meteoroid]]s, dust,&nbsp;etc. Most meteoroids that strike the earth vaporize in the atmosphere. Without a thick protective atmosphere meteoroid strikes would pose a much greater risk to a space settlement. [[Radar]] will sweep the space around each habitat mapping the trajectory of debris and other man-made objects and allowing corrective actions to be taken to protect the habitat.{{citation needed|date=September 2012}}<!-- on what basis is this claim made? "will sweep ..." and "allowing corrective action...". Even in low-Earth orbit, these orbital speeds are thousands of meters per second, and there is no source to show that large habitats might easily avoid them with radar. -->

In some designs (O'Neill/NASA Ames "Stanford Torus" and "Crystal palace in a Hatbox" habitat designs have a non-rotating cosmic ray shield of packed sand (~1.9 m thick) or even artificial aggregate rock (1.7 m ersatz concrete). Other proposals use the rock as structure and integral shielding (O'Neill, "the High Frontier". Sheppard, "Concrete Space Colonies"; Spaceflight, journal of the B.I.S.) In any of these cases, strong meteoroid protection is implied by the external radiation shell ~4.5 tonnes of rock material, per square meter.<ref>{{cite web| url=http://www.quadibloc.com/science/spaint.htm | title=A Space Habitat Design | website=quadibloc.com | date= | access-date= 8 February 2021 }}</ref>

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.

Proposals are available to move even kilometer-sized NEOs to high Earth orbits, and reaction engines for such purposes would move a space settlement and any arbitrarily large shield, but not in any timely or rapid manner, the thrust being very low compared to the huge mass.

===Heat rejection===
The habitat is in a vacuum, and therefore resembles a giant thermos bottle. Habitats also need a [[radiator]] to eliminate heat from absorbed sunlight. Very small habitats might have a central vane that rotates with the habitat. In this design, [[convection]] would raise hot air "up" (toward the center), and cool air would fall down into the outer habitat. Some other designs would distribute coolants, such as chilled water from a central radiator.

===Attitude control===
Most mirror geometries require something on the habitat to be aimed at the Sun and so [[Spacecraft attitude control|attitude control]] is necessary. The original O'Neill design used the two cylinders as [[momentum wheel]]s to roll the colony, and pushed the sunward pivots together or apart to use [[precession]] to change their angle.