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A space settlement (also called a space habitat, spacestead, space city or space colony) is a settlement in outer space, sustaining more extensively habitation facilities in space than a general
space station A space station (or orbital station) is a spacecraft which remains orbital spaceflight, in orbit and human spaceflight, hosts humans for extended periods of time. It therefore is an artificial satellite featuring space habitat (facility), habitat ...
or
spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...
. Possibly including
closed ecological system Closed ecological systems or contained ecological systems (CES) are ecosystems that do not rely on matter exchange with any part outside the system. The term is most often used to describe small, man-made ecosystems. Such systems can potentially ...
s, its particular purpose is permanent habitation. 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. Space settlements include orbital settlements (also called orbital habitat, orbital stead, orbital city or orbital colony) around the Earth or any other celestial body, as well as
cycler A cycler is a potential spacecraft on a closed transfer orbit that would pass close to two celestial bodies at regular intervals. Cyclers could be used for carrying heavy supplies, life support and radiation shielding. Concept A cycler encoun ...
s and
interstellar ark An interstellar ark is a conceptual starship designed for interstellar travel. Interstellar arks may be the most economically feasible method of traveling such distances. The ark has also been proposed as a potential habitat to preserve civiliz ...
s, as generation ships or ''world ships''. Space settlements are a form of extraterrestrial settlements, which more broadly includes habitats built on or within a body other than Earth, such as a settlement developed from a
moonbase A moonbase (or lunar base) is a human outpost on or below the surface of the Moon. More than a mere site of activity or temporary camp, moonbases are extraterrestrial bases, supporting uncrewed spaceflight, robotic or crewed spaceflight, human a ...
, a Mars habitat or an asteroid.


Definition

A space settlement is any large-scale habitation facility in outer space, or more particularly in an orbit. The
International Astronautical Federation The International Astronautical Federation (IAF) is an international space advocacy organization based in Paris, and founded in 1951 as a non-governmental organization to establish a dialogue between scientists around the world and to lay t ...
has differentiated space settlements to space habitats and space infrastructure the following way: While not automatically constituting a colonial entity, a space settlement can be an element of a space colony. The term "space colony" has been viewed critically, prompting
Carl Sagan Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist and science communicator. His best known scientific contribution is his research on the possibility of extraterrestrial life, including e ...
to propose the term ''space city.''


History

The idea of space settlements either in fact or fiction goes back to the second half of the 19th century. " The Brick Moon", a fictional story written in 1869 by Edward Everett Hale, is perhaps the first treatment of this idea in writing. In 1903, space pioneer
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (; rus, Константин Эдуардович Циолковский, p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj, a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) was a Russi ...
speculated about rotating cylindrical space settlements in ''Beyond Planet Earth''. In 1929
John Desmond Bernal John Desmond Bernal (; 10 May 1901 – 15 September 1971) was an Irish scientist who pioneered the use of X-ray crystallography in molecular biology. He published extensively on the history of science. In addition, Bernal wrote popular boo ...
speculated about giant space settlements. 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''.


O'Neill – The High Frontier

Around 1970, near the end of
Project Apollo The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...
(1961–1972), Gerard K. O'Neill, an experimental physicist at
Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...
, was looking for a topic to tempt his physics students, most of them freshmen in engineering. He hit upon the idea of assigning them feasibility calculations for large space-settlements. To his surprise, the habitats seemed feasible even in very large sizes: cylinders in diameter and long, even if made from ordinary materials such as steel and glass. 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 published an article about these colony concepts in ''
Physics Today ''Physics Today'' is the membership magazine of the American Institute of Physics. First published in May 1948, it is issued on a monthly schedule, and is provided to the members of ten physics societies, including the American Physical Society. ...
'' in 1974. He expanded the article in his 1976 book '' The High Frontier: Human Colonies in Space''.


NASA Ames/Stanford 1975 Summer Study

The result motivated
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
to sponsor a couple of summer workshops led by O'Neill. Several concepts were studied, with sizes ranging from 1,000 to 10,000,000 people, including versions of the
Stanford torus The Stanford torus is a proposed NASA design for a space settlement capable of housing 10,000 permanent residents. It is a type of rotating wheel space station, consisting of a ring with a diameter of about 1.8 km, its rotation providing about ...
. Three concepts were presented to NASA: the Bernal Sphere, the Toroidal Colony and the Cylindrical Colony. O'Neill's concepts had an example of a payback scheme: construction of solar power satellites from lunar materials. 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. He and other participants presumed that once such manufacturing facilities had started production, many profitable uses for them would be found, and the colony would become self-supporting and begin to build other colonies as well. The concept studies generated a notable groundswell of public interest. One effect of this expansion was the founding of the L5 Society in the U.S., a group of enthusiasts that desired to build and live in such colonies. The group was named after the space-colony orbit which was then believed to be the most profitable, a kidney-shaped orbit around either of Earth's lunar
Lagrange point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the gravitational influence of two massive orbiting bodies. Mathematically, this involves t ...
s 5 or 4.


Space Studies Institute

In 1977 O'Neill founded the Space Studies Institute, which initially funded and constructed some prototypes of the new hardware needed for a
space colonization Space colonization (or extraterrestrial colonization) is the human settlement, settlement or colonization of outer space and astronomical bodies. The concept in its broad sense has been applied to any permanent human presence in space, such ...
effort, as well as producing a number of feasibility studies. One of the early projects, for instance, involved a series of functional prototypes of a
mass driver A mass driver or electromagnetic catapult is a proposed method of non-rocket spacelaunch which would use a linear motor to Acceleration, accelerate and catapult Payload (air and space craft), payloads up to high speeds. Existing and proposed mass ...
, the essential technology for moving
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...
s efficiently from the Moon to space colony orbits.


Motivation

There are a range of arguments for space settlements, including: * As a base for crewed
space exploration Space exploration is the process of utilizing astronomy and space technology to investigate outer space. While the exploration of space is currently carried out mainly by astronomers with telescopes, its physical exploration is conducted bo ...
* Relieving Earth of industry and population pressure * Recreational habitation, either as visitors or residents at space (see space hotel) * Economic growth, developing access to resources in space and a space economy, without destroying
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
s and displacing
peoples The term "the people" refers to the public or common mass of people of a polity. As such it is a concept of human rights law, international law as well as constitutional law, particularly used for claims of popular sovereignty. In contrast, a ...
on Earth *
Space colonization Space colonization (or extraterrestrial colonization) is the human settlement, settlement or colonization of outer space and astronomical bodies. The concept in its broad sense has been applied to any permanent human presence in space, such ...
, claiming extraterrestrial space for settler colonial independence * For survival of human
civilization A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
and the
biosphere The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
, in case of a disaster on the Earth (natural or man-made)


Advantages

A number of arguments are made for space settlements having a number of advantages:


Access to solar energy

Space has an abundance of light produced from the Sun. In Earth orbit, this amounts to 1400 watts of power per square meter. This energy can be used to produce electricity from
solar cells A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.
or
heat engine A heat engine is a system that transfers thermal energy to do mechanical or electrical work. While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, pa ...
based power stations, process ores, provide light for plants to grow and to warm space settlements.


Outside gravity well

Earth-to-space settlement trade would be easier than Earth-to-planetary habitat trade, as habitats orbiting Earth will not have a
gravity well A sphere of influence (SOI) in astrodynamics and astronomy is the oblate spheroid-shaped region where a particular celestial body exerts the main gravitational influence on an orbiting object. This is usually used to describe the areas in the ...
to overcome to export to Earth, and a smaller gravity well to overcome to import from Earth.


In-situ resource utilization

Space settlements may be supplied with resources from extraterrestrial places like
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
,
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
s, or the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
(
in-situ resource utilization In space exploration, in situ resource utilization (ISRU) is the practice of collection, processing, storing and use of materials found or manufactured on other astronomical objects (the Moon, Mars, asteroids, etc.) that replace materials th ...
SRU see
Asteroid mining Asteroid mining is the hypothetical extractivism, extraction of materials from asteroids and other minor planets, including near-Earth objects. Notable asteroid mining challenges include the high cost of spaceflight, unreliable identification ...
). One could produce breathing oxygen, drinking water, and rocket fuel with the help of ISRU. It may become possible to manufacture solar panels from lunar materials.


Asteroids and other small bodies

Most asteroids have a mixture of materials, that could be mined, and because these bodies do not have substantial gravity wells, it would require low delta-V to draw materials from them and haul them to a construction site. 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.


Population

A 1974 estimate assumed that collection of all the material in the main
asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...
would allow habitats to be constructed to give an immense total population capacity. Using the free-floating resources of the Solar System, this estimate extended into the trillions.


Zero g recreation

If a large area at the rotation axis is enclosed, various zero-g sports are possible, including swimming,
hang gliding Hang gliding is an air sports, air sport or recreational activity in which a pilot flies a light, non-motorised, fixed-wing aircraft, fixed-wing heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium al ...
and the use of
human-powered aircraft A human-powered aircraft (HPA) is an aircraft belonging to the class of vehicles known as human-powered transport. As its name suggests, HPAs have the pilot not only steer, but power the aircraft (usually propeller-driven) by means of a system ...
.


Passenger compartment

A space settlement can be the passenger compartment of a large spacecraft for colonizing
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
s, moons, and planets. It can also function as one for a
generation ship A generation ship, generation starship or world ship, is a hypothetical type of interstellar ark starship that travels at sub- light speed. Since such a ship might require hundreds to thousands of years to reach nearby stars, the original occup ...
for travel to other planets or distant stars (L. R. Shepherd described a generation starship in 1952 comparing it to a small planet with many people living in it.)


Requirements

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.


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.


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. 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 Delta-''v'' (also known as "change in velocity"), symbolized as and pronounced , as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or l ...
from the desired habitat location.


Location

The optimal settlement orbits are still debated, and so orbital stationkeeping is probably a commercial issue. The lunar and 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. This provides quick, inexpensive access to both raw materials and the major market. Most settlement designs plan to use electromagnetic tether propulsion, or
mass driver A mass driver or electromagnetic catapult is a proposed method of non-rocket spacelaunch which would use a linear motor to Acceleration, accelerate and catapult Payload (air and space craft), payloads up to high speeds. Existing and proposed mass ...
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.


Protection from radiation

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 In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
for approximately two-thirds of the time (as happens with the Moon), putting residents at risk of proton exposure from the
solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
(see '' Health threat from cosmic rays''). Protection can be attained through passive or active shielding. 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. 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 high natural background areas on Earth. 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, to deflect particles could potentially greatly reduce mass requirements.


Atmosphere

Air
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...
, with normal partial pressures of
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
(21%),
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
and
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
(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 ( ) 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 Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sol ...
. The air of a habitat could be recycled in a number of ways. One concept is to use
photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...
garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...
s, possibly via
hydroponics Hydroponics is a type of horticulture and a subset of #Passive sub-irrigation, hydroculture which involves growing plants, usually crops or medicinal plants, without soil, by using water-based mineral Plant nutrition, nutrient Solution (chemi ...
, or forest gardening. 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 nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear weapons, nuclear-armed. Nuclear submarines have considerable performance advantages over "conventional" (typically Marine diesel engine, diesel-elect ...
, a similar form of closed environment, is to use a
catalytic Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...
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.


Food production

Organic materials for food production would also need to be provided. At first, most of these would have to be imported from Earth. After that, feces recycling should reduce the need for imports. 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. 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 Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...
, 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

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 Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...
l forces to simulate gravity. NASA studies with chickens and plants have proven that this is an effective physiological substitute for gravity. 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.


Meteoroids and dust

The habitat would need to withstand potential impacts from
space debris Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...
,
meteoroid A meteoroid ( ) is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than ''asteroids'', ranging in size from grains to objects up to wide. Objects smaller than meteoroids are classifie ...
s, dust, 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 Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
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. 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. 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 A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics. A radiator is always a ...
to eliminate heat from absorbed sunlight. Very small habitats might have a central vane that rotates with the habitat. In this design,
convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...
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 attitude control is necessary. The original O'Neill design used the two cylinders as
momentum wheel A reaction wheel (RW) is an electric motor attached to a flywheel, which, when its rotation speed is changed, causes a counter-rotation proportionately through Angular momentum#Conservation of angular momentum, conservation of angular momentum. ...
s to roll the colony, and pushed the sunward pivots together or apart to use
precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...
to change their angle.


Interior design

The interior of a space settlement should always have areas out of sight, to avoid the psychological effect of all reality being visible simultaneously, while also allowing for landscapes and wide vistas, so there is no sensation of living in a theater stage-like situation. Because of psychological reasons, the design should also avoid the perception that everything is human-controlled (for example, by having random artificial weather, or vegetation developing in a natural way).


Concepts


Base concepts

The two common original concepts are the Bernal sphere and the O'Neill cylinder.


Dumbbell-shape assembly concept

A dumbbell-like spacecraft or habitat, connected by a cable to a
counterweight A counterweight is a weight (object), weight that, by applying an opposite force, provides balance and stability of a machine, mechanical system. The purpose of a counterweight is to make lifting the load faster and more efficient, which saves e ...
or other habitat. This design has been proposed as a Mars ship, initial construction shack for a space habitat, and orbital hotel. It has a comfortably long and slow rotational radius for a relatively small station mass. Also, if some of the equipment can form the counter-weight, the equipment dedicated to artificial gravity is just a cable, and thus has a much smaller mass-fraction than in other concepts. 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. 11–15 February 2007. Retrieved 18 December 2010 This speculative design was also considered by the NASA studies. Small habitats would be mass-produced to standards that allow the habitats to interconnect. A single habitat can operate alone as a bola. However, further habitats can be attached, to grow into a " dumbbell" then a "bow-tie", then a ring, then a cylinder of "beads", and finally a framed array of cylinders. Each stage of growth shares more radiation shielding and capital equipment, increasing redundancy and safety while reducing the cost per person. This concept was originally proposed by a professional architect because it can grow much like Earth-bound cities, with incremental individual investments, unlike those that require large start-up investments. The main disadvantage is that the smaller versions use a large structure to support the radiation shielding, which rotates with them. In large sizes, the shielding becomes economical, because it grows roughly as the square of the colony radius. The number of people, their habitats, and the radiators to cool them grow roughly as the cube of the colony radius.


Further concepts

* Island One, a Bernal sphere settlement for about 10,000–20,000 people. *
Stanford torus The Stanford torus is a proposed NASA design for a space settlement capable of housing 10,000 permanent residents. It is a type of rotating wheel space station, consisting of a ring with a diameter of about 1.8 km, its rotation providing about ...
: an alternative to Island One. * Lewis One, a cylinder of radius 250 m with a non-rotating radiation shielding. The shielding protects the micro-gravity industrial space, too. The rotating part is 450m long and has several inner cylinders. Some of them are used for agriculture. * Island Three or O'Neill cylinder, an even larger cylindrical design (3.2 or 4 km radius and 32 km long). * McKendree cylinder, another concept that would use carbon nanotubes, a McKendree cylinder is paired cylinders in the same vein as the Island Three concept, but each 460 km in radius and 4600 km long (versus 3.2-4 km radius and 32 km long in the Island Three). * Kalpana One, revised, a short cylinder with 250 m radius and 325 m length. The radiation shielding is 10 t/m2 and rotates. It has several inner cylinders for agriculture and recreation. It is sized for 3,000 residents. *Bubbleworld or Inside/Outside concept, originated by Dandridge M. Cole in 1964, calls for drilling a tunnel through the longest axis of a large metallic asteroid and filling it with a volatile substance, possibly water. A very large solar reflector would be constructed nearby, focusing solar heat onto the asteroid, first to weld and seal the tunnel ends, then more diffusely to slowly heat the entire outer surface. As the metal softens, the water inside expands and inflates the mass, while rotational forces help shape it into a cylindrical form. Once expanded and allowed to cool, it can be spun to produce centrifugal pseudogravity, and the interior filled with soil, air and water. By creating a slight bulge in the middle of the cylinder, a ring-shaped lake can be made to form. Reflectors would allow sunlight to enter and to be directed where needed. This method would require a significant human and industrial presence in space to be at all feasible. The concept was popularized by
science fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...
author
Larry Niven Laurence van Cott Niven (; born April 30, 1938) is an American science fiction writer. His 1970 novel ''Ringworld'' won the Hugo Award for Best Novel, Hugo, Locus Award, Locus, Ditmar Award, Ditmar, and Nebula Award for Best Novel, Nebula award ...
in his
Known Space Known Space is the fictional setting of about a dozen science fiction novels and several collections of short stories by American writer Larry Niven. It has also become a shared universe in the spin-off ''Man-Kzin Wars'' anthologies. The Inter ...
stories, describing such worlds as the primary habitats of the Belters, a civilization who had colonized the asteroid belt. **"Bubbleworld" is also the name of a different concept of space settlement thought of by Dani Eder in 1995 (it is alternatively known as an Ederworld). This is a relatively thin, spherical shell surrounding a mass of gas great enough to be held together by gravity. If hydrogen is used as the gas, the shell would have a radius of about 240,000 km. The outside of the shell would have a living space 2,400 km thick (filled with breathable air) with an additional outer shell (possibly made of 500 m of steel) above it to hold in the air. * Asteroid terrarium, a similar idea to the bubble world, in the 2012 novel '' 2312'' by
hard science fiction Hard science fiction is a category of science fiction characterized by concern for scientific accuracy and logic. The term was first used in print in 1957 by P. Schuyler Miller in a review of John W. Campbell's ''Islands of Space'' in the Novemb ...
writer
Kim Stanley Robinson Kim Stanley Robinson (born March 23, 1952) is an American science fiction writer best known for his ''Mars'' trilogy. Many of his novels and stories have ecological, cultural, and political themes and feature scientists as heroes. Robinson has ...
. * Bishop Ring, a speculative design using
carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range ( nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized: * ''Single-walled carbon nanotubes'' (''S ...
s: a torus 1000 km in radius, 500 km in width, and with atmosphere retention walls 200 km in height. The habitat would be large enough that it could be "roofless", open to outer space on the inner rim.


Space station projects

Space settlements are in principle space stations, developments in space station construction therefore share many elements. The following projects and proposals, while not truly space settlements, incorporate aspects of what they would have and may represent stepping stones towards eventually building of space settlements. The
Lunar Gateway The Lunar Gateway, or simply Gateway, is a planned space station which is to be assembled in orbit around the Moon. The Gateway is intended to serve as a communication hub, science laboratory, and habitation module for astronauts as part ...
is a planned lunar space station, the first outside of
Low Earth Orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...
, therefore being the first spacecraft designed in unshielded space. 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 ISS module would have an outside diameter of with a ring interior cross-section diameter and would provide 0.08 to partial gravity. This test and evaluation centrifuge would have the capability to become a Sleep Module for ISS crew. The subsequent vehicle design would be a long-duration crewed space transport vehicle including the artificial gravity compartment intended to promote crew-health for a crew of up to six persons on missions of up to two years duration. The partial-g torus-ring
centrifuge A centrifuge is a device that uses centrifugal force to subject a specimen to a specified constant force - for example, to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby ...
would utilize both standard metal-frame and inflatable spacecraft structures and would provide 0.11 to if built with the diameter option. The Bigelow Commercial Space Station was announced in mid-2010. Bigelow has publicly shown space station design configurations with up to nine modules containing of habitable space. Bigelow began to publicly refer to the initial configuration as "Space Complex Alpha" in October 2010.


In fiction

Space settlements have been elements of different science-fiction stories, across different media, from books to movies like
Elysium Elysium (), otherwise known as the Elysian Fields (, ''Ēlýsion pedíon''), Elysian Plains or Elysian Realm, is a conception of the afterlife that developed over time and was maintained by some Greek religious and philosophical sects and cult ...
(2013) for a wheel shaped
Stanford torus The Stanford torus is a proposed NASA design for a space settlement capable of housing 10,000 permanent residents. It is a type of rotating wheel space station, consisting of a ring with a diameter of about 1.8 km, its rotation providing about ...
type and Interstellar (2014) for a cylindrical O'Neill type.


See also

*
Arcology Arcology, a Blend word, portmanteau of "architecture" and "ecology",. is a field of creating architectural design principles for very densely populated and Sustainable development, ecologically low-impact human habitats. The term was coined in ...
*
Bioastronautics Bioastronautics is a specialty area of biological and astronautical research which encompasses numerous aspects of biological, behavioral, and medical concern governing humans and other living organisms in outer space; and includes the design o ...
*
Closed ecological system Closed ecological systems or contained ecological systems (CES) are ecosystems that do not rely on matter exchange with any part outside the system. The term is most often used to describe small, man-made ecosystems. Such systems can potentially ...
*
Domed city A domed city is a hypothetical structure that encloses a large urban area under a single roof. In most descriptions, the dome is airtight and pressurized, creating a habitat that can be controlled for air temperature, composition and quality, typ ...
*
Dyson sphere A Dyson sphere is a hypothetical megastructure that encompasses a star and captures a large percentage of its power output. The concept is a thought experiment that attempts to imagine how a spacefaring civilization would meet its energy re ...
* Floating cities and islands in fiction *
Human outpost Human outposts
(artificially created controlled human habitat) * Locomotion in space *
Megastructure A megastructure (or macrostructure) is a very large artificial object, although the limits of precisely how large vary considerably. Some apply the term to any especially large or tall building. Some sources define a megastructure as an enorm ...
* Planetary chauvinism * * Space architecture * * Space stations and habitats in fiction *
Spaceflight Spaceflight (or space flight) is an application of astronautics to fly objects, usually spacecraft, into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such ...
*
Space station A space station (or orbital station) is a spacecraft which remains orbital spaceflight, in orbit and human spaceflight, hosts humans for extended periods of time. It therefore is an artificial satellite featuring space habitat (facility), habitat ...
* Spome * Underground living * Underground city *
Underwater habitat Underwater habitats are underwater structures in which people can live for extended periods and carry out most of the Circadian rhythm, basic human functions of a 24-hour day, such as working, resting, eating, attending to personal hygiene, and ...


Notes


References


NASA's table of contents for the studies
See the "online books" about halfway down the page.


External links


Gallery about space habitats
in
Wikimedia Commons Wikimedia Commons, or simply Commons, is a wiki-based Digital library, media repository of Open content, free-to-use images, sounds, videos and other media. It is a project of the Wikimedia Foundation. Files from Wikimedia Commons can be used ...
.
Lifeboat Foundation Space Habitats
a space habitat advocacy group.
''Space Settlements: A Design Study''
1977 book by NASA about designing a space settlement * *
NASA video about space habitats and space settlements construction as seen around 1970"s (5 min)

Video explaining rotating space habitats

Opening the High Frontier
a video about affordable spaceflight and building a spacefaring civilization.
The 1975 space habitat video credited with inspiring Blue Origin (Jeff "Amazon" Bezos as a boy).Segits.com
a website that refers to Space habitats as Segits or Self-sufficient Extra-terrestrial Green-habitat Intentional Transparent self-replicating communities. {{DEFAULTSORT:Space Habitat Human habitats Space farming