Editing Space colonization (section)

==Implementation==
Building colonies in space would require access to water, food, space, people, construction materials, energy, transportation, [[communication]]s, [[life support system|life support]], [[simulated gravity]], [[radiation]] protection, migration, governance and capital investment. It is likely the colonies would be located near the necessary physical resources. The practice of [[space architecture]] seeks to transform spaceflight from a heroic test of human endurance to a normality within the bounds of comfortable experience. As is true of other frontier-opening endeavors, the capital investment necessary for space colonization would probably come from governments,<ref>{{cite journal |author=Hickman |first=John |date=November 1999 |title=The Political Economy of Very Large Space Projects |url=http://www.jetpress.org/volume4/space.htm |url-status=live |journal=Journal of Evolution and Technology |volume=4 |issn=1541-0099 |archive-url=https://web.archive.org/web/20131204190958/http://www.jetpress.org/volume4/space.htm |archive-date=4 December 2013 |access-date=14 December 2013}}</ref> an argument made by John Hickman<ref>{{cite book |first=John |last=Hickman |date=2010 |title=Reopening the Space Frontier |publisher=Common Ground |isbn=978-1-86335-800-2}}</ref> and [[Neil deGrasse Tyson]].<ref>{{cite book|first=Neil deGrasse |last=Tyson |date=2012 |title=Space Chronicles: Facing the Ultimate Frontier |publisher=W.W. Norton & Company |isbn=978-0-393-08210-4}}</ref>

===Life support===
{{Further|Effect of spaceflight on the human body|Space medicine|Space food}}

[[File:Mars Food Production - Bisected.jpg|alt=|thumb|upright=1.2|Depiction of [[NASA]]'s plans to grow food on [[Mars]]]]

In space settlements, a life support system must recycle or import all the nutrients without "crashing." The closest terrestrial analogue to space life support is possibly that of a [[nuclear submarine]]. 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"—extracting oxygen from seawater, and typically dumping [[carbon dioxide]] overboard, although they recycle existing oxygen.<ref>{{Cite web|url=https://www.airitilibrary.com/Publication/alDetailedMesh?DocID=P20100106003-200911-201004190023-201004190023-1642-1650|title=A Novel Application of the SAWD-Sabatier-SPE Integrated System for CO2 Removal and O2 Regeneration in Submarine Cabins during Prolonged Voyages|last=Huang|first=Zhi|website=Airiti Library|access-date=10 September 2018}}</ref> Another commonly proposed life-support system is a [[closed ecological system]] such as [[Biosphere 2]].<ref>{{cite book | title=Manmade Closed Ecological Systems | first1= I. I. |last1=Gitelson | first2= G. M. |last2=Lisovsky | first3= R. D. |last3=MacElroy | publisher= [[Taylor & Francis]] |date=2003 | isbn = 0-415-29998-5}}</ref>

==== Solutions to health risks ====
{{See also|Bioastronautics}}
Although there are many physical, mental, and emotional health risks for future colonists and pioneers, solutions have been proposed to correct these problems. [[Mars500]], [[HI-SEAS]], and SMART-OP represent efforts to help reduce the effects of loneliness and confinement for long periods of time. Keeping contact with family members, celebrating holidays, and maintaining cultural identities all had an impact on minimizing the deterioration of mental health.<ref>{{Cite web|url=https://anxiety.psych.ucla.edu/nasa-study-stress-management-and-resilience-training-for-optimal-performance-smart-op|title=NASA Study: Stress Management and Resilience Training for Optimal Performance (SMART-OP) – Anxiety and Depression Research Center at UCLA|language=en-US|access-date=4 March 2019|archive-url=https://web.archive.org/web/20190404154812/https://anxiety.psych.ucla.edu/nasa-study-stress-management-and-resilience-training-for-optimal-performance-smart-op|archive-date=4 April 2019|url-status=live}}</ref> There are also health tools in development to help astronauts reduce anxiety, as well as helpful tips to reduce the spread of germs and bacteria in a closed environment.<ref>{{Cite web|url=https://phys.org/news/2017-09-e-mental-health-tool-key-astronauts.html|title=E-mental health tool may be key for astronauts to cope with anxiety, depression in space|website=Phys.org|language=en-us|access-date=4 March 2019|archive-url=https://web.archive.org/web/20190404154812/https://phys.org/news/2017-09-e-mental-health-tool-key-astronauts.html|archive-date=4 April 2019|url-status=live}}</ref> Radiation risk may be reduced for astronauts by frequent monitoring and focusing work to minimize time away from shielding.<ref name=":0">{{Cite web |title=Keeping Astronauts Healthy in Space |url=https://www.nasa.gov/vision/space/travelinginspace/30sept_spacemedicine.html |url-status=live |archive-url=https://web.archive.org/web/20190202103324/https://www.nasa.gov/vision/space/travelinginspace/30sept_spacemedicine.html |archive-date=2 February 2019 |access-date=5 March 2019 |website=NASA.gov |publisher=NASA |language=en}}</ref> Future space agencies can also ensure that every colonist would have a mandatory amount of daily exercise to prevent degradation of muscle.<ref name=":0" />

====Radiation protection====
{{see also|Health threat from cosmic rays}}

[[Cosmic rays]] and [[solar flare]]s create a lethal radiation environment in space. In orbit around certain planets with magnetospheres (including Earth), the [[Van Allen belts]] make living above the atmosphere difficult. To protect life, settlements must be surrounded by sufficient mass to absorb most incoming radiation, unless magnetic or plasma radiation shields are developed.<ref name = spacecraftshielding>[http://engineering.dartmouth.edu/~simon_g_shepherd/research/Shielding/ Spacecraft Shielding] {{Webarchive|url=https://web.archive.org/web/20110928223044/http://engineering.dartmouth.edu/~simon_g_shepherd/research/Shielding/ |date=28 September 2011 }} engineering.dartmouth.edu. Retrieved 3 May 2011.</ref> In the case of Van Allen belts, these could be drained using orbiting tethers<ref name="mirnov1996">{{cite journal |last1=Mirnov |first1=Vladimir |last2=Üçer |first2=Defne |last3=Danilov |first3=Valentin |author-link3=Valentin Danilov |date=10–15 November 1996 |title=High-Voltage Tethers For Enhanced Particle Scattering In Van Allen Belts |journal=APS Division of Plasma Physics Meeting Abstracts |volume=38 |pages=7 |bibcode=1996APS..DPP..7E06M |oclc=205379064 |id=Abstract #7E.06}}</ref> or radio waves.<ref>{{Cite web |title=NASA Finds Lightning Clears Safe Zone in Earth's Radiation Belt - NASA |url=https://www.nasa.gov/news-release/nasa-finds-lightning-clears-safe-zone-in-earths-radiation-belt/ |access-date=11 December 2023 |language=en-US}}</ref>

Passive mass shielding of four metric tons per square meter of surface area will reduce radiation dosage to several [[Sievert#Yearly dose examples|mSv]] or less annually, well below the rate of some populated [[Background radiation#Natural background radiation|high natural background areas]] on Earth.<ref>NASA SP-413 [http://settlement.arc.nasa.gov/75SummerStudy/5appendE.html Space Settlements: A Design Study. Appendix E Mass Shielding] {{Webarchive|url=https://web.archive.org/web/20130227031349/http://settlement.arc.nasa.gov//75SummerStudy/5appendE.html |date=27 February 2013 }} Retrieved 3 May 2011.</ref> This can be leftover material (slag) from processing lunar soil and asteroids into oxygen, metals, and other useful materials. However, it represents a significant obstacle to manoeuvering vessels with such massive bulk (mobile spacecraft being particularly likely to use less massive active shielding).<ref name = spacecraftshielding/> Inertia would necessitate powerful thrusters to start or stop rotation, or electric motors to spin two massive portions of a vessel in opposite senses. Shielding material can be stationary around a rotating interior.

====Psychological adjustment====
The monotony and loneliness that comes from a prolonged space mission can leave astronauts susceptible to cabin fever or having a psychotic break. Moreover, lack of sleep, fatigue, and work overload can affect an astronaut's ability to perform well in an environment such as space where every action is critical.<ref>Clynes, Manfred E. and Nathan S. Kline, (1960) "Cyborgs and Space," Astronautics, September, pp.&nbsp;26–27 and 74–76.</ref>

===Law, governance, and sovereignty===
{{Main|Space law|Space policy|Common heritage of humanity|Extraterrestrial real estate}}
A range of different models of transplanetary or extraterrestrial governance have been sketched or proposed. Often envisioning the need for a fresh or independent extraterrestrial governance, particularly in the void left by the contemporarily criticized lack of space governance and inclusivity.

{{anchor|Exonationalism}}It has been argued that space colonialism would, similarly to terrestrial [[settler colonialism]], produce colonial national identities.<ref name="Eller 2022 pp. 148–160">{{cite journal |last=Eller |first=Jack David |date=15 September 2022 |title=Space Colonization and Exonationalism: On the Future of Humanity and Anthropology |journal=Humans |volume=2 |issue=3 |pages=148–160 |doi=10.3390/humans2030010 |issn=2673-9461 |doi-access=free}}</ref>

[[Federalism]] has been studied as a remedy of such distant and autonomous communities.<ref name="u501">{{cite book | last=Crawford | first=Ian A. | title=The Meaning of Liberty Beyond Earth | chapter=Interplanetary Federalism: Maximising the Chances of Extraterrestrial Peace, Diversity and Liberty | series=Space and Society | publisher=Springer International Publishing | publication-place=Cham | date=2015 | isbn=978-3-319-09566-0 | doi=10.1007/978-3-319-09567-7_13 | pages=199–218}}</ref>

Space activity is legally based on the [[Outer Space Treaty]], the main international treaty. But [[space law]] has become a larger legal field, which includes other international agreements such as the significantly less ratified [[Moon Treaty]] and diverse national laws.

The Outer Space Treaty established the basic ramifications for space activity in article one: "The exploration and use of outer space, including the Moon and other celestial bodies, shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development, and shall be the province of all mankind." And continued in article two by stating: "Outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means."<ref name=unoda>{{cite web | url=http://disarmament.un.org/treaties/t/outer_space | title = Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies | access-date = 7 November 2020 | publisher= [[United Nations Office for Disarmament Affairs]]}}</ref>

The development of international space law has revolved much around outer space being defined as [[common heritage of mankind]]. The ''Magna Carta of Space'' presented by William A. Hyman in 1966 framed outer space explicitly not as ''[[terra nullius]]'' but as ''[[res communis]]'', which subsequently influenced the work of the [[United Nations Committee on the Peaceful Uses of Outer Space]].<ref name="Durrani 2019"/><ref>{{cite web |author=Lock |first=Alexander |date=6 June 2015 |title=Space: The Final Frontier |url=https://blogs.bl.uk/digitisedmanuscripts/2015/06/space-the-final-frontier.html |access-date=2 November 2020 |website=The British Library – Medieval manuscripts blog}}</ref>

===Economics===
{{Main|Space-based economy}}
Space colonization can roughly be said to be possible when the necessary methods of space colonization become [[Economic behavior|cheap enough]] (such as space access by cheaper launch systems) to meet the cumulative funds that have been gathered for the purpose, in addition to estimated profits from [[commercial use of space]].<ref>{{cite web|title=Space Settlement Basics |first=Al |last=Globus |website=National Space Society |url=https://www.nss.org/settlement/nasa/Basics/wwwwh.html |access-date=19 April 2025}}</ref>

====Overcoming access-to-space barriers====
Although there are no immediate prospects for the large amounts of money required for space colonization to be available given traditional launch costs,<ref>[http://settlement.arc.nasa.gov/Basics/wwwwh.html Space Settlement Basics] {{Webarchive|url=https://web.archive.org/web/20120706031203/http://settlement.arc.nasa.gov/basics/wwwwh.html |date=6 July 2012 }} by Al Globus, NASA Ames Research Center. Last Updated: 2 February 2012</ref> there is some prospect of a radical reduction to launch costs in the 2010s, which would consequently lessen the cost of any efforts in that direction. With a published price of {{USD|56.5}}{{nbsp}}million per launch of up to {{convert|13150|kg|abbr=on}} payload<ref name=sxCapabilitiesSvcs20131211>{{cite web |title=SpaceX Capabilities and Services |url=http://www.spacex.com/about/capabilities |year=2013<!-- copyright date; no other date provided --> |publisher=SpaceX |access-date=11 December 2013 |archive-url=https://web.archive.org/web/20131007205105/http://www.spacex.com/about/capabilities |archive-date=7 October 2013 |url-status=dead }} <!-- SpaceX refers to these prices as the "PAID IN FULL STANDARD LAUNCH PRICES (2013)" --></ref> to low Earth orbit, [[SpaceX]] [[Falcon 9]] rockets are already the "cheapest in the industry".<ref name=fp20131209/> Advancements currently being developed as part of the [[SpaceX reusable launch system development program]] to enable reusable Falcon 9s "could drop the price by an order of magnitude, sparking more space-based enterprise, which in turn would drop the cost of access to space still further through economies of scale."<ref name=fp20131209>{{cite news |last=Belfiore |first=Michael |title=The Rocketeer |url=https://foreignpolicy.com/articles/2013/12/02/the_rocketeer_elon_musk |access-date=11 December 2013 |newspaper=Foreign Policy |date=9 December 2013 |archive-url=https://web.archive.org/web/20131210233009/http://www.foreignpolicy.com/articles/2013/12/02/the_rocketeer_elon_musk |archive-date=10 December 2013 |url-status=live }}</ref> If SpaceX is successful in developing the reusable technology, it would be expected to "have a major impact on the cost of access to space", and change the increasingly [[competition (economics)|competitive market]] in space launch services.<ref name="bbc20130930">{{cite news |url=https://www.bbc.co.uk/news/science-environment-24331860 |title=Recycled rockets: SpaceX calls time on expendable launch vehicles |work=BBC News |last=Amos |first=Jonathan |date=30 September 2013 |access-date=2 October 2013 |archive-url=https://web.archive.org/web/20131003085420/http://www.bbc.co.uk/news/science-environment-24331860 |archive-date=3 October 2013 |url-status=live }}</ref>

The [[President's Commission on Implementation of United States Space Exploration Policy]] suggested that an [[Inducement prize contest|inducement prize]] should be established, perhaps by government, for the achievement of space colonization, for example by offering the prize to the first organization to place humans on the Moon and sustain them for a fixed period before they return to Earth.<ref>[http://www.nasa.gov/pdf/60736main_M2M_report_small.pdf A Journey to Inspire, Innovate, and Discover], {{Webarchive|url=https://web.archive.org/web/20121010151959/http://www.nasa.gov/pdf/60736main_M2M_report_small.pdf|date=10 October 2012}}, Report of the [[President's Commission on Implementation of United States Space Exploration Policy]], June 2004.</ref>

==== Money and currency ====
Experts have debated on the possible use of money and currencies in societies that will be established in space. The Quasi Universal Intergalactic Denomination, or QUID, is a physical currency made from a space-qualified polymer [[Polytetrafluoroethylene|PTFE]] for inter-planetary travelers. QUID was designed for the foreign exchange company Travelex by scientists from Britain's National Space Centre and the University of Leicester.<ref>{{Cite web|url=https://www.space.com/4454-scientists-design-space-currency.html|title=Scientists Design New Space Currency|last=Christensen|first=Bill|date=10 October 2007|website=Space.com|access-date=21 January 2019|archive-url=https://web.archive.org/web/20190121232640/https://www.space.com/4454-scientists-design-space-currency.html|archive-date=21 January 2019|url-status=live}}</ref> Other possibilities include the incorporation of [[cryptocurrency]] as the primary form of currency, as suggested by [[Elon Musk]].<ref>{{Cite web|last=Delbert|first=Caroline|date=29 December 2020|title=Elon Musk Says Mars Settlers Will Use Cryptocurrency, Like 'Marscoin'|url=https://www.popularmechanics.com/space/moon-mars/a35085273/elon-musk-says-mars-settlers-will-use-cryptocurrency-like-marscoin/|access-date=24 February 2021|website=Popular Mechanics|language=en-US}}</ref>

====Socio-economic issues ====
[[Human spaceflight]] has enabled only temporarily relocating a few privileged people and no permanent space migrants.

The societal motivation for space migration has been questioned as rooted in colonialism, questioning the fundamentals and inclusivity of space colonization. Highlighting the need to reflect on such socio-economic issues beside the technical challenges for implementation.<ref name="m794">{{cite journal | last=Shaw | first=Debra Benita | title=The Way Home: Space Migration and Disorientation | journal=New Formations: A Journal of Culture/Theory/Politics | publisher=Lawrence & Wishart | volume=107 | issue=107 | date=15 February 2023 | issn=1741-0789 | pages=118–138 | doi=10.3898/NewF:107-8.07.2022 | url=https://muse.jhu.edu/article/881496 | access-date=14 May 2024 }}</ref><ref name="l879">{{cite journal | last=Klass | first=Morton | title=Recruiting new "huddled masses" and "wretched refuse": a prolegomenon to the human colonization of space | journal=Futures | publisher=Elsevier BV | volume=32 | issue=8 | year=2000 | issn=0016-3287 | doi=10.1016/s0016-3287(00)00024-0 | pages=739–748}}</ref>

===Resources===
{{Further|Asteroid mining}}

====Raw materials====
Colonies on the Moon, Mars, asteroids, or the metal-rich planet [[Mercury (planet)|Mercury]], could extract local materials. The Moon is deficient in [[Volatile (astrogeology)|volatiles]] such as [[argon]], [[helium]] and compounds of [[carbon]], [[hydrogen]] and [[nitrogen]]. The LCROSS impacter was targeted at the [[Cabeus (crater)|Cabeus crater]] which was chosen as having a high concentration of water for the Moon. A plume of material erupted in which some water was detected. Mission chief scientist Anthony Colaprete estimated that the Cabeus crater contains material with 1% water or possibly more.<ref>{{Cite news | url=http://www.sfgate.com/science/article/NASA-s-moon-blast-called-a-smashing-success-3213973.php | work=The San Francisco Chronicle | first=David | last=Perlman | title=NASA's moon blast called a smashing success | date=10 October 2009 | access-date=19 July 2015 | archive-url=https://web.archive.org/web/20150721235224/http://www.sfgate.com/science/article/NASA-s-moon-blast-called-a-smashing-success-3213973.php | archive-date=21 July 2015 | url-status=live }}</ref> Water [[ice]] should also be in other permanently shadowed craters near the lunar poles. Although helium is present only in low concentrations on the Moon, where it is deposited into [[regolith]] by the solar wind, an estimated million tons of He-3 exists over all.<ref>{{cite web|title=The Second Moon Race: It's the USA vs. China vs. India vs. ... Nigeria?|url=http://www.satnews.com/stories2007/4588/ |archive-url= https://web.archive.org/web/20120308151604/http://www.satnews.com/stories2007/4588/|archive-date=8 March 2012}}</ref> It also has industrially significant [[oxygen]], [[silicon]], and metals such as [[iron]], [[aluminium]], and [[titanium]].

Launching materials from Earth is expensive, so bulk materials for colonies could come from the Moon, a [[near-Earth object]] (NEO), [[Phobos (moon)|Phobos]], or [[Deimos (moon)|Deimos]]. The benefits of using such sources include: a lower gravitational force, no [[Drag (physics)|atmospheric drag]] on cargo vessels, and no biosphere to damage. Many NEOs contain substantial amounts of metals. Underneath a drier outer crust (much like [[oil shale]]), some other NEOs are inactive comets which include billions of tons of water ice and [[kerogen]] hydrocarbons, as well as some nitrogen compounds.<ref>{{cite conference |title=Discovery of Abundant, Accessible Hydrocarbons nearly Everywhere in the Solar System |last1= Zuppero|first1= Anthony |year= 1996 |publisher= [[American Society of Civil Engineers|ASCE]] |book-title= Proceedings of the Fifth International Conference on Space '96 |doi= 10.1061/40177(207)107|isbn= 0-7844-0177-2}}</ref>

Farther out, [[Colonization of the outer Solar System#Jupiter trojans|Jupiter's Trojan asteroids]] are thought to be rich in water ice and other volatiles.<ref>{{Cite news|last=Sanders|first=Robert|title=Binary asteroid in Jupiter's orbit may be icy comet from solar system's infancy|date=1 February 2006|publisher=UC Berkeley|url=http://www.berkeley.edu/news/media/releases/2006/02/01_patroclus.shtml|access-date=25 May 2009|archive-url=https://web.archive.org/web/20181211102116/https://www.berkeley.edu/news/media/releases/2006/02/01_patroclus.shtml|archive-date=11 December 2018|url-status=live}}</ref>

[[Recycling]] of some raw materials would almost certainly be necessary.

====Energy====
[[Solar energy]] in orbit is abundant, reliable, and is commonly used to power satellites today. There is no night in free space, and no clouds or atmosphere to block sunlight. Light intensity obeys an [[inverse-square law]]. So the solar energy available at distance ''d'' from the Sun is ''E'' = 1367/''d''<sup>2</sup> W/m<sup>2</sup>, where ''d'' is measured in [[astronomical unit]]s (AU) and 1367 watts/m<sup>2</sup> is the energy available at the distance of Earth's orbit from the Sun, 1 AU.<ref>McGraw-Hill Encyclopedia of Science & Technology, 8th Edition 1997; vol. 16, p. 654.</ref>

In the weightlessness and vacuum of space, high temperatures for industrial processes can easily be achieved in [[solar ovens]] with huge parabolic reflectors made of metallic foil with very lightweight support structures. Flat mirrors to reflect sunlight around radiation shields into living areas (to avoid line-of-sight access for cosmic rays, or to make the Sun's image appear to move across their "sky") or onto crops are even lighter and easier to build.

Large solar power photovoltaic cell arrays or thermal power plants would be needed to meet the electrical power needs of the settlers' use. In developed parts of Earth, electrical consumption can average 1 kilowatt/person (or roughly 10 [[watt-hour|megawatt-hours]] per person per year.)<ref>[http://www.unescap.org/esd/energy/information/ElectricPower/1999-2000/access.htm UNESCAP Electric Power in Asia and the Pacific], {{webarchive|url=https://web.archive.org/web/20110213083253/http://www.unescap.org/esd/energy/information/ElectricPower/1999-2000/access.htm|date=13 February  2011}}.</ref> These power plants could be at a short distance from the main structures if wires are used to transmit the power, or much farther away with [[wireless power transmission]].

A major export of the initial space settlement designs was anticipated to be large [[solar power satellite]]s (SPS) that would use wireless power transmission (phase-locked [[microwave]] beams or lasers emitting wavelengths that special solar cells convert with high efficiency) to send power to locations on Earth, or to colonies on the Moon or other locations in space. For locations on Earth, this method of getting power is extremely benign, with zero emissions and far less ground area required per watt than for conventional solar panels. Once these satellites are primarily built from lunar or asteroid-derived materials, the price of SPS electricity could be lower than energy from fossil fuel or nuclear energy; replacing these would have significant benefits such as the elimination of [[greenhouse gases]] and [[nuclear waste]] from electricity generation.<ref>{{Cite web|url=http://large.stanford.edu/courses/2015/ph240/gaertner1/|title=Solar vs. Traditional Energy in Homes|website=large.stanford.edu |first=Ryan|last=Gaertner|date=9 November 2015|access-date=26 February 2019|archive-url=https://web.archive.org/web/20181024050207/http://large.stanford.edu/courses/2015/ph240/gaertner1/|archive-date=24 October 2018|url-status=live}}</ref>

Transmitting solar energy wirelessly from the Earth to the Moon and back is also an idea proposed for the benefit of space colonization and energy resources. Physicist Dr. David Criswell, who worked for NASA during the Apollo missions, proposed the idea of using power beams to transfer energy from space. These beams, microwaves with a wavelength of about 12&nbsp;cm, would be almost untouched as they travel through the atmosphere. They could also be aimed at more industrial areas to keep away from humans or animal activities.<ref name="i2massociates.com">{{Cite web |url=http://www.i2massociates.com/downloads/AAPG_Memoir_101-July18-2012.pdf |title=Nuclear Power and Associated Environmental Issues in the Transition of Exploration and Mining on Earth to the Development of Off-World Natural Resources in the 21st Century |access-date=18 September 2017 |archive-url=https://web.archive.org/web/20150214125331/http://i2massociates.com/downloads/AAPG_Memoir_101-July18-2012.pdf |archive-date=14 February 2015 |url-status=live }}</ref> This would allow for safer and more reliable methods of transferring solar energy.

In 2008, scientists were able to send a 20 watt microwave signal from a mountain on the island of Maui to the island of Hawaii.<ref>{{Cite journal|last=Dance|first=Amber|date=16 September 2008|title=Beaming energy from space|journal=Nature|doi=10.1038/news.2008.1109|issn=0028-0836}}</ref> Since then [[JAXA]] and Mitsubishi have been working together on a $21&nbsp;billion project to place satellites in orbit which could generate up to 1 gigawatt of energy.<ref>{{cite web|url=https://www.popsci.com/technology/article/2011-06/satellites-could-gather-energy-sun-and-beam-it-down-earth/ |title=Space Based Solar Power |first=Corey|last=Binns|archive-url=https://web.archive.org/web/20170927054041/http://www.popsci.com/technology/article/2011-06/satellites-could-gather-energy-sun-and-beam-it-down-earth |archive-date=27 September 2017|publisher=Popular Science| date=2 June 2011}}</ref> These are the next advancements being done today to transmit energy wirelessly for space-based solar energy.

However, the value of SPS power delivered wirelessly to other locations in space will typically be far higher than to Earth. Otherwise, the means of generating the power would need to be included with these projects and pay the heavy penalty of Earth launch costs. Therefore, other than proposed demonstration projects for power delivered to Earth,<ref name="NatSecSpaceOffice2007">{{cite web |date=10 October 2007 |title=Space-Based Solar Power As an Opportunity for Strategic Security: Phase 0 Architecture Feasibility Study |url=https://apps.dtic.mil/sti/pdfs/ADA473860.pdf |url-status=live |archive-url=https://web.archive.org/web/20220926134325/https://apps.dtic.mil/sti/pdfs/ADA473860.pdf |archive-date=26 September 2022 |access-date=26 September 2022 |website= |publisher=U.S. National Security Space Office}}</ref> the first priority for SPS electricity is likely to be locations in space, such as communications satellites, fuel depots or "orbital tugboat" boosters transferring cargo and passengers between low Earth orbit (LEO) and other orbits such as [[geosynchronous orbit]] (GEO), [[lunar orbit]] or [[Highly elliptical orbit|highly-eccentric Earth orbit]] (HEEO).<ref name="Lewis-1996"/>{{rp|132}} The system will also rely on satellites and receiving stations on Earth to convert the energy into electricity. Because this energy can be transmitted easily from dayside to nightside, power would be reliable 24/7.<ref>{{cite magazine|url=https://www.wired.co.uk/article/moon-solar-energy-power |title=Beaming solar energy from the Moon could solve Earth's energy crisis |archive-url=https://web.archive.org/web/20171011044359/http://www.wired.co.uk/article/moon-solar-energy-power |archive-date=11 October 2017 |date=29 March 2017 |magazine=Wired |first=David |last=Warmflash}}</ref>

[[Nuclear power]] is sometimes proposed for colonies located on the Moon or on Mars, as the supply of solar energy is too discontinuous in these locations; the Moon has nights of two Earth weeks in duration. Mars has nights, relatively high gravity, and an atmosphere featuring [[Climate of Mars#Effect of dust storms|large dust storms]] to cover and degrade solar panels. Also, Mars' greater distance from the Sun (1.52 astronomical units, AU) means that only ''1/1.52<sup>2</sup>'' or about 43% of the solar energy is available at Mars compared with Earth orbit.<ref>{{cite web|url=https://www.sciencedaily.com/releases/2009/10/091004020806.htm |title='Trash Can' Nuclear Reactors Could Power Human Outpost On Moon Or Mars |archive-url=https://web.archive.org/web/20170918154323/https://www.sciencedaily.com/releases/2009/10/091004020806.htm|archive-date=18 September 2017 |date=4 October 2009 |website=ScienceDaily}}</ref> Another method would be transmitting energy wirelessly to the lunar or Martian colonies from solar power satellites (SPSs) as described above; the difficulties of generating power in these locations make the relative advantages of SPSs much greater there than for power beamed to locations on Earth. In order to also be able to fulfill the requirements of a Moon base and energy to supply life support, maintenance, communications, and research, a combination of both nuclear and solar energy may be used in the first colonies.<ref name="i2massociates.com"/>

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

===Self-sustainment===
{{see also|von Neumann probe|Self-replicating machine|molecular nanotechnology}}

====In situ manufacturing====
[[Space manufacturing]] could enable self-replication. Some consider it the ultimate goal because it would allow an [[exponential growth|exponential]] increase in colonies, while eliminating costs to, and dependence on, Earth.<ref>{{Cite magazine |first=Ian |last=Crawford |title=Where are they? |magazine=Scientific American |volume=283 |number=1 |date=July 2000 |pages=38–43 |jstor=26058784 |url=https://www.jstor.org/stable/26058784}}</ref> It could be argued that the establishment of such a colony would be Earth's first act of [[self-replication]].<ref>{{cite journal | last1 = Margulis | first1 = Lynn | author-link = Lynn Margulis | last2 = Guerrero | first2 = Ricardo | year = 1995 | title = Life as a planetary phenomenon: the colonization of Mars | journal = Microbiología | volume = 11 | pages = 173–84 | pmid = 11539563 }}</ref> Intermediate goals include colonies that expect only information from Earth (science, engineering, entertainment) and colonies that just require periodic supply of light weight objects, such as [[integrated circuit]]s, medicines, [[DNA|genetic material]] and tools.

====Sustaining a population====
In 2002, the [[Anthropology|anthropologist]] [[John H. Moore]] estimated<ref>{{Cite web |url=https://www.newscientist.com/article/dn1936-magic-number-for-space-pioneers-calculated |title="Magic number" for space pioneers calculated |date=15 February 2002 |work=New Scientist |first=Damian |last=Carrington}}</ref> that a population of 150–180 would permit a stable society to exist for 60 to 80 generations—equivalent to 2,000 years.

Assuming a journey of 6,300 years, the astrophysicist Frédéric Marin and the particle physicist Camille Beluffi calculated that the minimum viable population for a [[generation ship]] to reach [[Proxima Centauri]] would be 98 settlers at the beginning of the mission (then the crew will breed until reaching a stable population of several hundred settlers within the ship).<ref>{{cite journal |arxiv=1806.03856|last1=Marin|first1=F|title=Computing the minimal crew for a multi-generational space travel towards Proxima Centauri b|journal=Journal of the British Interplanetary Society|volume=71|pages=45|last2=Beluffi|first2=C|year=2018|bibcode=2018JBIS...71...45M}}</ref><ref>{{cite magazine |url=https://www.technologyreview.com/2018/06/22/142160/this-is-how-many-people-wed-have-to-send-to-proxima-centauri-to-make-sure-someone-actually/ |magazine=[[MIT Technology Review]] |title=This is how many people we'd have to send to Proxima Centauri to make sure someone actually arrives |date=22 June 2018 |quote="We can then conclude that, under the parameters used for those simulations, a minimum crew of 98 settlers is needed for a 6,300-year multi-generational space journey towards Proxima Centauri b," say Marin and Beluffi.}}</ref>

In 2020, Jean-Marc Salotti proposed a method to determine the minimum number of settlers to survive on an extraterrestrial world. It is based on the comparison between the required time to perform all activities and the working time of all human resources. For Mars, 110 individuals would be required.<ref>{{cite journal |last1=Salotti |first1=Jean-Marc |title=Minimum Number of Settlers for Survival on Another Planet |journal=Scientific Reports |date=16 June 2020 |volume=10 |issue=1 |page=9700 |doi=10.1038/s41598-020-66740-0 |pmid=32546782 |pmc=7297723 |bibcode=2020NatSR..10.9700S |doi-access=free }}</ref>