Space Settlement Basics

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 nobody 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. 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 of the Earth.

What?

• Rather than live on the outside of a planet, settlers will live on the inside of gigantic spacecraft. Typical space settlement designs are roughly one half to a few kilometers across. A few designs are much larger.
• Settlements must be air tight to hold a breathable atmosphere, and must rotate to provide psuedo-gravity. Thus, people stand on the inside of the hull.
• Enormous amounts of matter, probably lunar soil at first, must cover the settlements to protect inhabitants from radiation. On Earth our atmosphere does this job, but space settlements need about five tons of matter covering every square meter of a colony's hull to protect space settlers from cosmic rays and solar flares.
• Each settlement must be an independent biosphere. All oxygen, water, wastes, and other materials must be recycled endlessly.

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 (NEO's -- asteroids and comets), there are many advantages to orbital colonies. Advantages include:

• Earth-normal 'gravity'. The Moon and Mars have a surface gravity much less than Earth normal (which called 1g - the g stands for 'gravity'). The lunar surface is at roughly 1/6g and Mars is a 1/3g planet. Children raised in low-g cannot be expected to develop bones and muscles strong enough to visit Earth except in desperation -- it will be too painful and exhausting. For example, this author weighs 73kg (160 pounds). If I went to a 3g planet, the equivalent of moving from Mars to Earth, I would weigh 225 kg (almost 500 pounds) and would have great difficulty getting out of bed. For children raised on the Moon or Mars, attending college on Earth will be out of the question.

  By contrast, orbital colonies can rotate to provide any g level desired, although it's not true gravity. Spinning the colony creates a force called pseudo-gravity, that feels a lot like gravity. Pseudo-gravity is much like what you feel when a car takes a sharp turn at high speed. Your body is pressed up against the door. Simillarly, as an orbital space colony turns, the inside of the colony pushes on the inhabitants forcing them to go around. The amount of this force can be controlled and for reasonable colony sizes and rotation rates the force can be about 1g. For example, a colony with an 895 meter (a bit less than 1000 yards) radius rotating at one rpm (rotations per minute) provides 1g at the hull. Children raised on orbital colonies should have no trouble visiting Earth for extended periods.

• Rapid resupply from Earth. The Moon is a few days away from Earth, and trips to Mars take many months. Early colonies in Earth orbit will be only hours away. This is a huge logistical advantage for a large project like building space settlements.
• Continuous, ample, reliable solar energy. In orbit there is no night. Solar power is available 24/7. Most places on the Moon or Mars are in darkness half of the time (the only exception is the lunar poles). Mars, in addition, is much farther from the Sun and so receives about half the solar power available at Earth orbit. Mars also has dust storms which interfere with solar power.
• Great views from Earth (and eventually other planets). Space colonization 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 magnificient view of the stars at night. Any settlement on the Moon or Mars will also have a view of unchanging, starkly beautiful, dead-as-a-doornail, rock strewn surface. However, settlements in earth orbit will have one of the most stunning views in our solar system - the living, ever-changing Earth.
• 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 a space colony 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 weightlessness is fun. Acrobatics, sports and dance go to a new level when constraints of gravity are removed. It's not going to be easy to keep the kids in 1g areas enough to satisfy Mom and Dad that their bones will be strong enough for a visit to Disneyland.
• Zero-g construction means bigger colonies. Space colonists will spend almost all of their time indoors. It is impossible for an unprotected human to survive outside for more than few seconds. In this situation, obviously bigger colonies are better. Colonies on the Moon or Mars won't be much bigger than buildings on Earth, especially at first. However, in orbit astronauts can easily move spacecraft weighing many tons by hand. Everything is weightless and this makes large scale construction much easier. Colonies can be made so large that, even though you are really inside, it feels like the out-of-doors.
• Much greater growth potential. The Moon and Mars together have a surface area roughly the size of Earth. But if the single largest asteroid (Ceres) were to be used to build orbital space colonies, the total living area created would be approximately 150 times the surface area of the Earth. Since much of the Earth is ocean or sparsely inhabited, settlements built from Ceres alone could provide uncrowded homes for more than a trillion people.
• Economics. Near-Earth orbital colonies can service Earth's tourist, energy, and materials markets more easily than the Moon. Mars is too far away to easily trade with Earth. Space colonies, wherever they are built, will be very expensive. Supplying Earth with valuable goods and services will be critical to paying for colonization.

Mars and the Moon have one big advantage over most orbits: there's plenty of materials. However, this advantage is eliminated by simply building orbital settlements next to asteroids. It may even be easier to mine asteroids for materials than the Mars or the Moon as there is much less gravity. Fortunately, there are tens of thousands of suitable asteroids in orbits near that of Earth alone, and far more in the asteroid belt. 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 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. How?

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.

• Materials. Launching materials from Earth is very expensive, so bulk materials should come from the Moon or Near-Earth Objects (NEOs - asteroids and comets with orbits near Earth) where gravitational forces are much less, there is no atmosphere, and there is no biosphere to damage. Our Moon has large amounts of oxygen, silicon and metals, but little hydrogen, carbon, or nitrogen. NEOs contain substantial amounts of metals, oxygen, hydrogen and carbon. NEOs also contain some nitrogen, but not necessarily enough to avoid major supplies from Earth.
• Energy. Solar energy is abundant, reliable and is commonly used to power satellites today. Massive structures will be needed to convert sunlight into large amounts of electrical power for settlement use. Energy may be an export item for space settlements, using microwave beams to send power to Earth.
• Transportation. This is the key to any space endeavor. Present launch costs are very high, $2,000 to $ 14,000 per pound from Earth to Low Earth Orbit (LEO). To settle space we need much better launch vehicles and must avoid serious damage to the atmosphere from the thousands, perhaps millions, of launches required. One possibility is airbreathing hypersonic air/spacecraft under development by NASA and others. Transportation for milllions of tons of materials from the Moon and asteroids to settlement construction sites is also necessary. One well studied possibility is to build electronic catapults on the Moon to launch bulk materials to waiting settlements.
• Communication. Compared to the other requirements, communication is relatively easy. Much of the current terrestrial communications already pass through satellites.
• Life support. People need air, water, food and reasonable temperatures to survive. On Earth a large complex biosphere provides these. In space settlements, a relatively small, closed system must recycle all the nutrients without "crashing." The Biosphere II project in Arizona has shown that a complex, small, enclosed, man-made biosphere can support eight people for at least a year, although there were many problems. A year or so into the two year mission oxygen had to be replenished, which strongly suggests that they achieved atmospheric closure. For the first try, one major oxygen replenishment and perhaps a little stored food isn't too bad. Although Biosphere II has been correctly criticized on scientific grounds, it was a remarkable engineering achievement and provides some confidence that self sustaining biospheres can be built for space settlements.
• Radiation protection. Cosmic rays and solar flares create a lethal radiation environment in space. To protect life, settlements must be surrounded by sufficient mass to absorb most incoming radiation. This can be achieved with left over from processing lunar soil and asteroids into oxygen, metals, and other useful materials.

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.
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, Canada, Europe, 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 arrys, 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 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.

Why?

Growth

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:

• Great Views. Many astronauts have returned singing the praises of their view of Earth from orbit. Low earth orbit settlements, and eventually settlements near Jupiter and Saturn, will have some of the most spectacular views in the solar system. Of course, all space settlements will have unmatched views of the stars, unhindered by clouds, air pollution, or (with some care) bright city lights.
• Low-g recreation. Consider circular swimming pools around and near the axis of rotation. You should be able to dive up into the water! Sports and dance at low or zero-g will be fantastic. For dancers, note that in sufficiently low gravity, always available near the axis of rotation, anyone can jump ten times higher than Baryshnikov ever dreamed.
• Environmental Independence. On Earth we all share a single biosphere. We breathe the same air, drink the same water, and the misdeeds of some are visited on the bodies of all. Each space settlement is completely sealed and does no share atmosphere or water with other settlements or with Earth. Thus if one settlement pollutes their air, no one else need breathe it.
• Custom living. Since the entire environment is man-made, you can really get what you want. Like lake front property? Make lots of lakes. Like sunsets? Program sunset simulations into weather system every hour. Like to go barefoot? Make the entire environment foot-friendly.

Survival

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

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.

When?

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.

Unless...

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 mechanosythesis 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 fromorbit 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 the same as 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 diamonoid 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

DISCLAIMER: This web site is not a policy statement. It is intended to be an accessible introduction to the ideas developed in the Stanford/NASA Ames space settlement studies of the 1970s to support the annual NASA Ames Student Space Settlement Design Contest.

Curator: Al Globus
NASA Responsible Official: Dr. Ruth Globus		Last Updated: June 01, 2016
If you find any errors on this page contact Al Globus.