Because we are planetary creatures, most people think of space settlements on Mars or perhaps Earth’s Moon. However, it turns out that life in orbit is very attractive. Instead of building a settlement on the outside of a planet, to live in orbit we must build giant spacecraft and live inside. In the 1970s Princeton physicist Gerard O’Neill and others showed that orbital space colonies were physically possible, attractive places to live, and may make economic sense. They found that orbit is a good place for an expanding, technological civilization.
An orbital space settlement is a giant spacecraft big enough to live in. Orbital settlements will travel endlessly through space while the folks inside work, play, socialize, raise families, etc. These spacecraft will be kilometers across, big enough to feel like you are ‘outside’ when you leave your house. The settlements will rotate so that you feel something very close to Earth normal gravity at the hull.
There are a number of reasons to believe that orbital living is the way to go.
Proximity to Earth. The first orbital settlements may well be built only a few hundred miles from Earth in ‘Low Earth Orbit’ (LEO). High LEO is far enough out that the settlement won’t crash into Earth but low enough for the Earth’s van Allen Belts to protect settlers from deadly solar storms. Travel back and forth to Earth should take only a few hours. Visits from relatives and friends will be common, and traveling to Earth for vacation or schooling should be easy. Perhaps more important, bringing supplies, materials, and specialized equipment from Earth to support construction will be relatively easy.
Continuous, ample, reliable solar energy. In a high enough orbit there is no night. Solar power is available 24/7 in most high orbits, although in high LEO there is some darkness during each orbit as a structure passes through the Earth’s shadow. Most satellites in Earth orbit use solar power today, deploying large solar cell arrays like wings stretching from the craft. The solar arrays for settlements must be huge in order to generate enough power. This power can be generated on separate solar power satellites and beamed to the settlement, much as power beamed from such satellites to Earth can play a major role in solving our energy problems.
Weightless construction. Zero-g construction means big settlements can be built with relative ease. On Earth, for example, you could not build a round structure that is several miles high because it would collapse under its own weight, but in zero-gravity it is entirely possible to build such large structures, and in orbit astronauts can move objects weighing many tons by hand. Space settlers will spend almost all of their time inside the settlement because it is impossible for an unprotected human to survive outside for more than a few seconds. In this situation, obviously, bigger settlements are better. Settlements can be made so large that, even though you are really inside, it feels like the out-of-doors.
Weightless recreation. Although space colonies will have 1g at the hull, in the center you will experience weightlessness. If you’ve ever jumped off a diving board, you’ve been weightless. It’s the feeling you have after jumping and before you hit the water. The difference in an orbital space settlement is that the feeling will last for as long as you like. If you’ve ever seen videos of astronauts playing in 0g, you know that weightlessness is fun. Acrobatics, sports and dance go to a new level when constraints of gravity are removed.
Great views of Earth (and eventually other planets). Space settlement is, at its core, a real estate business. The value of real estate is determined by many things, including “the view.” Any space settlement will have a magnificent view of the stars at night. Settlements in Earth orbit will have one of the most stunning views in our solar system: the living, ever-changing Earth.
Enormous growth potential. If the single largest asteroid (Ceres) were to be used to build orbital space settlements, the total living area created would be well over a hundred times the land area of the Earth. This is because Ceres is a solid, three dimensional object but orbital space settlements are basically hollow with only air on the inside. Thus, Ceres alone can provide the building materials for uncrowded homes for hundreds of billions of people, at least.
Economics. Near-Earth orbital settlements can service Earth’s tourist, energy, and materials markets. Space settlements, wherever they are built, will be very expensive. Supplying Earth with valuable goods and services will be critical to paying for settlement.
Early settlements can be expected to orbit the Earth. Later settlements can spread out across the solar system, taking advantage of the water in Jupiter’s moons or exploiting the materials of the asteroid belt. There is good reason to believe that orbital space settlements can provide terrific homes for ten trillion people, or perhaps even more. There is so much room for growth that the people of this world may realize that it is easier to build new land to live on rather than to fight over the limited resources that exist on the Earth. What a world that would be.
Annotated Bibliography of Recommended Reading
2017 papers:
Space Settlement: An Easier Way (PDF), Al Globus, Stephen Covey, and Daniel Faber, NSS Journal of Space Settlement, July 2017. Describes a relatively easy, incremental path to free space settlement by taking advantage of very low radiation levels in Equatorial Low Earth Orbit (ELEO) and higher rotation rates. Low levels of radiation in ELEO may permit settlements with little or no radiation shielding. Higher rotation rates permit much smaller settlements. Together this reduces settlement design mass by two to three orders of magnitude and places early settlements very close to Earth, radically reducing the difficulty of building the first space settlements and making launch from Earth practical. The mass model used in this paper is available here as an Excel spreadsheet.
Space Settlement Population Rotation Tolerance (PDF), Al Globus and Theodore Hall, NSS Journal of Space Settlement, June 2017. This paper reviews the literature to find that space settlement residents and visitors can tolerate at least four, and probably six, rotations per minute to achieve 1g of artificial gravity. This means settlements can be radically smaller, and thus easier to build, than previously believed. Combined with the next paper on radiation shielding, the first space settlements can be two orders of magnitude less massive and closer to Earth than previous designs, making launch from Earth practical.
Orbital Space Settlement Radiation Shielding (PDF), Al Globus and Joe Strout, NSS Journal of Space Settlement, April 2017. The major result of this paper is that settlements in low (~500 km) Earth equatorial orbits may not require any radiation shielding at all based on a careful analysis of requirements and extensive simulation of radiation effects. This radically reduces system mass and has profound implications for space settlement, as extraterrestrial mining and manufacturing are no longer on the critical path to the first settlements, although they will be essential in later stages. It also means the first settlements can evolve from space stations, hotels, and retirement communities in relatively small steps.
The High Frontier: Human Colonies in Space, by Gerard K. O’Neill. 1st Edition: William Morrow and Company, 1977; 2nd Edition: Space Studies Institute, 1989; 3rd Edition: Apogee Books, 2000. [NSS Review]. [Buy from Amazon]. The pioneering book by the late Princeton physicist, Gerard K. O’Neill. “A thought-provoking work of true historical significance.” — Thomas Paine, NASA Administrator, 1968-1970. “Changed our way of thinking of space, of space habitats, of the Moon and Sun as resources.” — Isaac Asimov. “As you read this book, I hope you will come to share some of this vision.” — Shuttle Astronaut Kathy Sullivan.
1st Edition 19772nd Edition 19893rd Edition 2000
“The High Frontier: An Easier Way” by Tom Marotta and Al Globus, 2018. [NSS Review] [Buy from Amazon]. A worthy update to Gerard K. O’Neill’s seminal 1977 book. Describes an interim, lower-cost approach to build smaller settlements in Equatorial Low Earth Orbit to help bridge the gap to O’Neill’s full vision.
“The Colonization of Space” by Gerard K. O’Neill, Physics Today, 27(9):32-40 (September, 1974). [Complete online copy]. The brilliant classic paper by O’Neill is now available online. “Careful engineering and cost analysis shows we can build pleasant, self-sufficient dwelling places in space…, solving many of Earth’s problems.”
Colonies in Space, by T. A. Heppenheimer: Stackpole Books, 1977. [NSS Review] [Complete online copy] [Buy from Amazon]. A comprehensive and factual account of the prospects for human colonization of space. “How warm and delightful to read about an expanding future for humanity! Mr. Heppenheimer takes us into the infinite world of the coming space age and tells us everything there is to know about it.” — Isaac Asimov.
Space Settlements: A Design Study, edited by Richard D. Johnson and Charles Holbrow: NASA SP-413, 1977. [Complete online copy] [Buy from Amazon]. Results of the 1975 summer faculty fellowship program in engineering systems design conducted by NASA, Stanford University, and the American Society for Engineering Education. “The people of Earth have both the knowledge and resources to colonize space. It is the principal conclusion of the study group that the United States, possibly in cooperation with other nations, should take specific steps toward that goal of space colonization.”
Space Manufacturing Facilities: Space Colonies, edited by Gerry Grey: American Institute of Aeronautics and Astronautics, 1977. [Online abstracts and some pages] [Buy from Amazon] [Interlibrary Loan OCLC #4900596]. Proceedings of the Princeton/AIAA/NASA Conference, May, 1975. The conference explored construction methods, productivity, and payoff to the Earth of permanent industrial habitats near the L-5 Earth-Moon Lagrange libration point. Discussions were based on the use of lunar surface raw materials and solar energy as the sources for a rapidly expanding industrial economy. See additional Space Manufacturing Conference proceedings for subsequent years.
Space Resources and Space Settlements, edited by John Billingham, William Gilbreath, and Brian O’Leary: NASA SP-428, 1979. [Complete online copy] [Buy from Amazon]. Technical papers derived from the 1977 Summer Study on Space Settlements and Industrialization Using Nonterrestrial Materials conducted at NASA Ames Research Center. Study Director was Gerard K. O’Neill. It was the largest and most comprehensive investigation of space manufacturing and habitation at the time, with forty senior researchers and ten students. Topics covered included regenerative life support, habitat design, electromagnetic mass drivers, asteroid resources for space manufacturing, and processing of nonterrestrial materials.
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“The High Frontier: An Easier Way” by Tom Marotta and Al Globus, 2018. [NSS Review] [Buy from Amazon]. A worthy update to Gerard K. O’Neill’s seminal 1977 book. Describes an interim, lower-cost approach to build smaller settlements in Equatorial Low Earth Orbit to help bridge the gap to O’Neill’s full vision.
“The Colonization of Space” by Gerard K. O’Neill, Physics Today, 27(9):32-40 (September, 1974). [Complete online copy]. The brilliant classic paper by O’Neill is now available online. “Careful engineering and cost analysis shows we can build pleasant, self-sufficient dwelling places in space…, solving many of Earth’s problems.”
Colonies in Space, by T. A. Heppenheimer: Stackpole Books, 1977. [NSS Review] [Complete online copy] [Buy from Amazon]. A comprehensive and factual account of the prospects for human colonization of space. “How warm and delightful to read about an expanding future for humanity! Mr. Heppenheimer takes us into the infinite world of the coming space age and tells us everything there is to know about it.” — Isaac Asimov.
Space Settlements: A Design Study, edited by Richard D. Johnson and Charles Holbrow: NASA SP-413, 1977. [Complete online copy] [Buy from Amazon]. Results of the 1975 summer faculty fellowship program in engineering systems design conducted by NASA, Stanford University, and the American Society for Engineering Education. “The people of Earth have both the knowledge and resources to colonize space. It is the principal conclusion of the study group that the United States, possibly in cooperation with other nations, should take specific steps toward that goal of space colonization.”
Space Manufacturing Facilities: Space Colonies, edited by Gerry Grey: American Institute of Aeronautics and Astronautics, 1977. [Online abstracts and some pages] [Buy from Amazon] [Interlibrary Loan OCLC #4900596]. Proceedings of the Princeton/AIAA/NASA Conference, May, 1975. The conference explored construction methods, productivity, and payoff to the Earth of permanent industrial habitats near the L-5 Earth-Moon Lagrange libration point. Discussions were based on the use of lunar surface raw materials and solar energy as the sources for a rapidly expanding industrial economy. See additional Space Manufacturing Conference proceedings for subsequent years.
Space Colonies, edited by Stewart Brand: A CoEvolution Book, Penguin Books, 1977. [Complete online copy] [Buy from Amazon]. This collection of assorted material from CoEvolution Quarterly includes four nice pieces by Gerard O’Neill (Congressional testimony, an article, an interview, and a discussion), a good summary by Eric Drexler, and an extensive section of unique and interesting pro and con debate on the subject.
Space Resources and Space Settlements, edited by John Billingham, William Gilbreath, and Brian O’Leary: NASA SP-428, 1979. [Complete online copy] [Buy from Amazon]. Technical papers derived from the 1977 Summer Study on Space Settlements and Industrialization Using Nonterrestrial Materials conducted at NASA Ames Research Center. Study Director was Gerard K. O’Neill. It was the largest and most comprehensive investigation of space manufacturing and habitation at the time, with forty senior researchers and ten students. Topics covered included regenerative life support, habitat design, electromagnetic mass drivers, asteroid resources for space manufacturing, and processing of nonterrestrial materials.
