Space settlement is the creation of permanent human communities beyond Earth, where people put down roots and stay rather than visit for a tour of duty and return. It is the long-term project of moving part of human civilization into space for good, and it is the idea the International Space Development Conference exists to advance.
That one-line answer hides a deeper and more interesting question. A research base is not a settlement. A space station is not a settlement. Neither is a flag planted on the Moon. So what actually separates a true settlement from everything that has come before it, and why has a single idea anchored an international conference for more than four decades? This is the vision behind ISDC, laid out plainly.
What Space Settlement Actually Means
It helps to separate two phrases that look almost identical. Space settlement is the general process of developing and settling space, while a space settlement is a specific place in space where people live, work, and raise families. One is the movement, the other is a destination within it.
The distinction matters because it rules out most of what people picture when they hear the term. The dictionary sense of “to settle” carries the idea of taking up residence, which implies permanence: a home, a job, family life, a community that intends to stay. A soldier deployed to a base or a scientist assigned to Antarctica for a season is not settling anywhere. They are visiting with a return ticket. By contrast, a settlement is built to last, populated by people who intend to make their lives there.
The clearest working definition comes from the National Space Society, the nonprofit that founded and runs ISDC. It is worth quoting in full, because it draws the line cleanly: a space settlement is a habitation in space or on a celestial body where families live on a permanent basis, and that engages in commercial activity which enables the settlement to grow over time, with the goal of becoming economically and biologically self-sustaining as part of a larger network of space settlements. Three ideas are doing the work there. Families and permanence. An economic engine that pays for itself rather than depending on government budgets. And self-sufficiency, the ability to keep going even if the supply line from Earth were cut.
How Space Settlement Differs From Exploration and Colonization
Three terms get used interchangeably in headlines, and keeping them apart clarifies what settlement is and is not.
Exploration is reconnaissance. Apollo astronauts explored the Moon. Rovers explore Mars. Exploration gathers knowledge and plants no roots, and the people who do it come home. Settlement begins where exploration leaves off, when people stop returning and start staying.
A station or base is a workplace, not a home. The International Space Station is the closest thing humanity has built to living in space, yet it is a rotating crew of professionals on assignment, resupplied constantly from the ground. By that standard, even a permanently staffed base on the Moon or Mars would still be an outpost if families do not live there, if no children are born there, and if it cannot survive without a steady stream of support from Earth. Size alone does not change this. A base with thousands of workers is still a base if everyone is on rotation.
Why Settle Space at All?
Building permanent homes beyond Earth would be one of the most expensive and difficult things our species has ever attempted. The honest question is why anyone should bother, and there are several answers. One of the most striking starts with a simple fact: there are vastly more resources in space than on Earth.
The numbers are staggering. The largest asteroid, Ceres, holds enough material to build orbital settlements with a combined living area more than a hundred times the land area of Earth. The energy reaching settlements from the Sun could exceed humanity’s current total energy use by a factor in the billions. From that abundance flow the reasons most often cited for settlement: economic growth and new wealth, clean energy beamed back to Earth from space-based solar power, and the long-term survival of a species that currently keeps all of its eggs in one planetary basket. Settlement is also framed as a way to relieve pressure on Earth’s biosphere, moving heavy industry off-world so the home planet can heal.
There is a quieter argument underneath the practical ones. Life spent four billion years confined to the oceans before moving onto land. We may be standing at a comparable threshold, the moment life begins to move off its planet of origin. The conviction at the heart of the vision is simple: a future with space settlement is a better future than one without it.
What Could a Space Settlement Look Like?
There is no single blueprint. Settlement could take root in several very different places, and they are best seen as complementary rather than competing.
The most striking concept is the free-space settlement, an enormous rotating habitat that orbits in open space rather than resting on a planet. Spun to generate artificial gravity and built from lunar or asteroid material, designs like the O’Neill cylinder imagine interior landscapes the size of a small region, complete with farmland, towns, rivers, and weather. We explore that idea in depth in our companion piece on O’Neill cylinders.
Surface settlements are the other path: permanent communities on the Moon and Mars. The Moon offers proximity, a few days from Earth, and the same lunar material that could supply orbital habitats. Mars offers something rarer, a world that may hold most of the raw ingredients a settlement needs to eventually stand on its own. Beyond them lie the asteroids, both a source of construction material and, in time, sites for settlements of their own.
These visions are not mutually exclusive. The likely future is many kinds of settlement at once, on worlds and in open space, linked into a single growing network.
Where the Vision Came From
The idea moved from science fiction to serious engineering in the 1970s. Princeton physicist Gerard K. O’Neill, working with NASA Ames Research Center and Stanford University, ran the numbers and concluded that large orbital settlements were achievable within known physics, that lunar and asteroid mines could supply the materials, and that the Sun could power it all. Those findings were gathered into NASA’s 1977 report Space Settlements: A Design Study, which remains a touchstone for the field. The work proved the idea was not fantasy but a hard engineering problem.
From that foundation grew an organized movement to make settlement real, captured in a vision of “people living and working in thriving communities beyond the Earth, and the use of the vast resources of space for the dramatic betterment of humanity.” That line, the Vision statement of the National Space Society, has been the through-line of ISDC since its earliest meetings.
The vision also has a concrete plan behind it: a Roadmap to Space Settlement that lays out twenty milestones running from where we are now to a settled solar system. The early milestones are recognizable from today’s headlines: continuous occupancy of low Earth orbit, cheaper and more frequent launches, an integrated transport system through the space between Earth and the Moon. Later ones reach further, to lunar and Martian bases that mature into true settlements, to orbital cities in open space, and ultimately toward the stars. Those milestones are, in effect, the agenda ISDC works through each year, treating settlement not as a someday dream but as a series of concrete, fundable steps.
Where the Vision Is Debated: The International Space Development Conference
A vision this large needs a place to be argued, refined, and pushed forward, and that is what the International Space Development Conference has been for more than four decades. ISDC, the annual flagship gathering of the National Space Society, is where the scientists, engineers, entrepreneurs, policymakers, students, and advocates working on every milestone of the roadmap come together in one place.
Across several days of parallel sessions, ISDC covers the full span of the settlement project, from space solar power and lunar development to Mars, asteroid resources, and space policy. It is also where the next generation enters the conversation: student finalists in the Gerard K. O’Neill Space Settlement Contest present their own settlement designs alongside the professionals. The conference is where the abstract idea of settlement becomes a working agenda, debated by the people actually building toward it.
The next gathering, ISDC 2027, takes place May 27 to 30, 2027, in Los Angeles. It is the clearest single window into where the vision of space settlement stands and where it is headed next.
Frequently Asked Questions
Does the International Space Station count as a space settlement?
No, and it would not become one even if it operated for centuries, because permanence of the structure is not the test. The station is a workplace its crews rotate through, not a home anyone settles into for good. A settlement turns on the opposite: families who stay, and an economy robust enough to sustain them.
How many people would a real space settlement need?
There is no magic number, and population alone does not make a settlement. A large base can still be a base. For long-term genetic health, estimates often cite a minimum in the hundreds, with several thousand being far more robust, though future advances in genetics and in robotic and 3D-printed manufacturing could lower the count needed to be self-sustaining.
When could space settlement actually happen?
No firm date exists, and settlement is best understood as a staged process rather than a single event. The roadmap’s earliest milestones are already underway, while true self-sustaining settlements on the Moon, Mars, or in orbit remain much further out. The prevailing view among advocates is that meaningful progress is achievable within the lifetimes of people alive today.
How can I get involved in space settlement?
The most direct route is to join the conversation where it happens. Students can enter the O’Neill Space Settlement Contest with original designs, and anyone can attend ISDC, follow the Roadmap to Space Settlement, or join the National Space Society directly to support the work and connect with others advancing it.