Space Settlement Basics


You. Or at least people a lot like you. Space settlements will be a place for ordinary people.

Presently, with few exceptions, only highly trained and carefully selected astronauts go to space. Space settlement needs inexpensive, safe launch systems to deliver thousands, perhaps millions, of people into orbit. If this seems unrealistic, note that a hundred and fifty years ago no one had ever flown in an airplane, but today nearly 500 million people fly each year.

Some special groups might find space settlement particularly attractive: The handicapped could keep a settlement at zero-g to make wheelchairs and walkers unnecessary. Some religious groups might prefer to live away from "non-believers." Penal colonies might be created in orbit as they should be fairly escape proof. People who wish to experiment with very different social and political forms could get away from restrictive social norms.

Although some colonies may follow this model, it's reasonable to expect that the vast majority of space colonists will be ordinary people. Indeed, eventually most people in space settlements will be born there, and some day they may vastly exceed Earth's population. Based on the materials available, the human population in orbit could one day exceed ten trillion living in millions of space colonies with a combined living space hundreds of times the surface area of the Earth.


A space settlement is a home in orbit. Pictures of space colonies.
Lewis One space settlement design.


In orbit, not on a planet or moon. Why should we live in orbit rather than on a planet or moon? Because orbit is far superior to the Moon and Mars for colonization, and the other planets and moons are too hot, too far away, and/or have no solid surface.

For an alternate view, see Robert Zubrin's powerful case for Mars exploration and colonization. Mars' biggest advantage is that all the materials necessary for life may be found on Mars. While materials for orbital colonies must be imported from the Moon or Near Earth Objects (NEOs -- asteroids and comets), there are many advantages to orbital colonies. Advantages include:

The best place to live on Mars is not nearly as nice as the most miserable part of Siberia. Mars is far colder, you can't go outside without a space suit, and it's a months-long rocket ride if you want a Hawaiian vacation. The Moon is even colder at night, and it's literally boiling during the day. By contrast, orbital colonies have unique and desirable properties, particularly 0g recreation and great views. Building and maintaining orbital colonies should be quite a bit easier than similar sized homesteads on the Moon or Mars. Colonies in orbit are better positioned to provide goods and services to Earth. For these reasons, orbital colonies will almost certainly come first, with lunar and Martian colonization later.

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 easily available materials of the asteroid belt. Eventually the solar system will become too crowded, and some settlements will head for nearby stars.

Interstellar travel seems impractical due to long travel times. But what if you've lived in space settlements for fifty generations? Do you really care if your settlement is near our Sun or in transit to Alpha Centuri? So what if the trip takes a few generations? If energy and make up materials for the trip can be stored, a stable population can migrate to nearby stars. At the new star, local materials and energy can be used to build new settlements and resume population growth.


With great difficulty. Fortunately, although building space colonies will be very difficult, it's not impossible. Building cities in space will require materials, energy, transportation, communications, life support, and radiation protection.

Space settlement feasibility was addressed in a series of summer studies at NASA Ames Research Center in the 1970's. These studies concluded that space settlement is feasible, but very difficult and expensive. For additional information see the bibliography.

Although we know generally how to build space colonies, we have yet to find an economic path from where we are now to construction of the first colony. One approach is to develop a series of profitable, private industries. For example:

  1. Sub-orbital tourism. The key to space colonization is transportation from the Earth's surface to LEO. The key to inexpensive, economic transportation is the same as learning a musical instrument: practice, practice, practice. To date, there have been only a few thousand space launches and only a few hundred people have been to space. Traditional uses of space, such as communication, Earth resources, military, exploration and science won't require a whole lot more in the next few decades. However, hundreds of thousands of people say they would travel to space if the price was right. Tourism is a market that may provide the necessary practice.

    Making a profit on space tourism seems like a ridiculous dream, but it has already happened. Burt Rutan's Scaled Composites flew their privately developed rocket, SpaceShipOne, into space three times in 2004, winning the $10 million Ansari X-Prize in the process. Not only did they win the prize, but they sold the technology to Richard Branson's Virgin Galactic for over $20 million, becoming profitable on their first space tourism venture. Virgin Galactic has put up another $50 million to develop five larger vehicles to carry tourists into space for a profit. The price is expected to be around $200,000 per flight.

    In a late 2004 talk, Rutan made the following predictions:

    Time will tell if these are accurate.
  2. Orbital Tourism. SpaceShipOne went almost straight up 100km to get into space, and then came nearly straight down again. This sub-orbital flight is much easier than orbital flight, which requires the spacecraft to go nearly 30,000 km/hr horizontally to avoid crashing back to Earth. Surprisingly, the first paying orbital tourists have already flown. The Russians have taken Dennis Tito and Mark Shuttleworth to the International Space Station (ISS) developed by the U.S., Russia, Europe, Canada, Japan and other partners. However, even at $20 million a trip, this business only makes economic sense because the international partners spent tens of billions of dollars developing the ISS for other reasons. Nonetheless, if Rutan's prediction is correct we will see affordable orbital tourism within the lifetime of most people reading this. Successful orbital mass tourism will mean not only people, but solar power satellites can be launched from the ground to orbit affordably.
  3. Solar Power Satellites Electrical power is a multi-hundred billion dollar per year business today. We know how to generate electricity in space using solar cells. For example, the ISS provides about 80 kilowatts continuously from an acre of solar arrays. By building much larger satellites out of hundreds of solar arrays, it is possible to generate a great deal of electrical power. This can be converted to microwaves and beamed to Earth to provide electricity with absolutely no greenhouse gas emissions or toxic waste of any kind. If transportation to orbit is inexpensive following development of the tourist industry, much of Earth's power could be provided from space, simultaneously providing a large profitable business and dramatically reducing pollution on Earth.
  4. Asteroidal Metals John Lewis, in Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets estimates that the current market value of the metals in 3554 Amun, one small nearby asteroid, is about $20 trillion. There's $8 trillion worth of iron and nickel, $6 trillion worth of cobalt, and about $6 trillion in platinum-group metals. Once we can easily launch thousands of people into orbit, and build giant solar power satellites, it shouldn't be too difficult to retrieve 3554 Amun and other asteroids to supply Earth with all the metals we will ever need.
Each of these steps is potentially profitable on its own merits. Once they are completed, we will be able to put people in orbit inexpensively, generate large amounts of power, and supply ample materials from NEOs and perhaps the Moon -- all the elements needed to build the first space colony.



Why build space settlements? Why do weeds grow through cracks in sidewalks? Why did life crawl out of the oceans and colonize land? Because living things want to grow and expand. We have the ability to live in space (see the bibliography), therefore we will -- but not this fiscal year.

The key advantage of space settlements is the ability to build new land, rather than take it from someone else. This allows a huge expansion of humanity without war or destruction of Earth's biosphere. The asteroids alone provide enough material to make new orbital land hundreds of times greater than the surface of the Earth, divided into millions of colonies. This land can easily support trillions of people.

A Nice Place to Live

A few features of orbital real estate are worth mentioning:


Someday the Earth will become uninhabitable. Before then humanity must move off planet or become extinct. One potential near term disaster is collision with a large comet or asteroid. Such a collision could kill billions of people. Large collisions have occurred in the past, destroying many species. Future collisions are inevitable, although we don't know when. Note that in July 1994, the comet Shoemaker-Levy 9 (1993e) hit Jupiter.

If there were a major collision today, not only would billions of people die, but recovery would be difficult since everyone would be affected. If major space settlements are built before the next collision, the unaffected space settlements can provide aid, much as we offer help when disaster strikes another part of the world.

Building space settlements will require a great deal of material. If NEOs are used, then any asteroids heading for Earth can simply be torn apart to supply materials for building colonies and saving Earth at the same time.

Power and Wealth

Those that colonize space will control vast lands, enormous amounts of electric power, and nearly unlimited material resources. The societies that develop these resources will create wealth beyond our wildest imagination and wield great power -- hopefully for good rather than for ill.

In the past, societies which have grown by colonization have gained wealth and power at the expense of those who were subjugated. Unlike previous colonization programs, space colonization will build new land, not steal it from the natives. Thus, the power and wealth born of space colonization will not come at the expense of others, but rather represent the fruits of great labors.


How long did it take to build New York? California? France? Even given ample funds the first settlement will take decades to construct. No one is building a space settlement today, and there are no immediate prospects for large amounts of money, so the first settlement will be awhile. If Burt Rutan's prediction of affordable orbital tourism in 25 years is correct, however, it's reasonable to expect the first orbital colony to be built within about 50 years.

If the first settlement is designed to build additional settlements, colonization could proceed quite rapidly. The transportation systems will already be in place and a large, experienced workforce will be in orbit.

How much will it cost?

How much did Canada cost? Chicago? San Francisco? A lot. Space settlements will be even more expensive because all the basic life support the Earth gives us for free must be built, and transportation costs will be very high. On the other hand, children cost a lot of money and many people are only too happy to pay.

Unless ...

Space colonization is extraordinarily expensive because launch vehicles are difficult to manufacture and operate. For example, the current (2004) cost to put an individual into orbit for a short time is about $20 million. To enable large scale space tourism by the middle class, this cost must be reduced to about $1,000-10,000, a factor of 3 to 4 orders of magnitude. Space tourism has launch requirements similar to space settlement suggesting that a radical improvement in manufacturing technology may be necessary to enable space colonization. Note that current launch costs vary from $2,000-14,000 per pound for operational vehicles.

One candidate for a major improvement in manufacturing technology is molecular nanotechnology. An important branch of nanotechnology is concerned with developing diamonoid mechanosynthesis. This means building things out of diamond-like materials, placing each atom at a precise location (ignoring thermal motion). Diamond is 69 times stronger than titanium for the same weight and is much stiffer. If spacecraft were made of diamonoid materials rather than aluminum, they could be much lighter allowing more payload. For an excellent analysis applying nanotechnology to space development see McKendree 1995.

Diamond mechanosynthesis may enable a radical transportation system that could allow millions of people to go to orbit each year -- an orbital tower. An orbital tower is a structure extending from the Earth's surface into orbit. To build an orbital tower, start construction at geosynchronous orbit. Extend the tower down towards Earth and upwards at the same rate. This keeps the center-of-mass at geosynchronous orbit so the tower stays over one point on the Earth's surface. Extend the tower all the way to the surface and attach it. Then an elevator on the tower can move people and materials to and from orbit at very low cost. There are many practical problems with orbital towers, but they may be feasible.

An orbital tower is in tension so it won't collapse, but it must be very strong or it will break. The point of greatest strain is at geosynchronous orbit, so an orbital tower must be thickest at that point. The ratio of the diameter of the tower between geosynchronous orbit and the ground is called the taper factor. For steel, the taper factor is greater than 10,000 making a steel orbital tower completely impractical. However, for diamonoid materials the taper factor is 21.9 with a safety factor according to McKendree 1995. Thus, a diamonoid orbital tower 1 meter thick at the ground would be only 22 meters thick at geosynchronous orbit. Fullerene nanotechnology, using carbon nanotubes, may be even better than diamond allowing a smaller taper factor. Calculations suggest that the materials necessary for construction of such an orbital tower would require one asteroid with a radius between one and two kilometers. These calculations assume the tower is built from diamonoid material with a density of 4 g/cm^3 and the asteroid has a density of 1.8 g/cm^3 and is 3% carbon.

Thus, molecular nanotechnology may enable space settlement.

To the space settlement home page.

Author: Al Globus

[NASA] [Ames Research Center]
WebWork: Al Globus, Bryan Yager, and Tugrul Sezen
[LifeSciences] [Space Settlement]