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 to 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 norms.

Although some settlements may follow this model, it's reasonable to expect that the vast majority of space settlers will be ordinary people. Indeed, eventually most people in space settlements may be born there, and some day they may vastly exceed Earth's population.

What?

• Rather than live on the outside of a planet, settlers will live inside of large spacecraft. Free-space settlement designs range from 100 meters to a few kilometers across. A few designs are much larger.
• Settlements must be air tight to hold a breathable atmosphere, and may rotate to provide psuedo-gravity. Thus, people stand on the inside of the hull.
• Settlements close to Earth and near the equator are protected from most space radiation by the Earth itself and the Earth's magnetic field. Further from Earth enormous amounts of matter, probably lunar regolith and asteroidal materials, must cover the settlements to protect inhabitants from radiation.
• 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 settlement. Mars' biggest advantage is that all the materials necessary for life may be found on Mars, although it will take a long time before Mars settlers can build everything they need. While materials for free-space settlements must be imported from Earth, the Moon or Near Earth Objects (NEO's -- asteroids and comets), there are many advantages to free-space settlements including:

• Proximity to Earth. Early settlements in Low Earth Orbit, say 500 km up, are 760 times closer than the Moon and 100,000 times closer than Mars at closest approach. The Moon is a few days away from Earth, and trips to Mars take many months. Early settlements in Earth orbit will be only hours away. This is a massive logistical advantage.
• 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, free-space settlements can rotate to provide any g level desired, although it's not true gravity. Spinning the settlement 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. Similarly, as a free-space settlement turns, the inside of the hull pushes on the inhabitants forcing them to go around. The amount of this force can be controlled and for reasonable settlement sizes and rotation rates the force can be about 1g. For example, a settlement with an 895 meter (a bit less than 1000 yards) radius rotating at one rpm (rotations per minute) provides 1g at the hull. At four rpm the necessary radius is 56 m (about half the length of a football field including end zones). Children raised on free-space settlements should have no trouble tolerating Earth gravity for extended periods.

• Continuous, ample, reliable solar energy. In high orbit there is little or no night. Solar power is available nearly 24/7. In low orbit night is only about 45 minutes out of each 90. 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 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. 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 settlements 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 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 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 settlements. Space settlers 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 settlements are better. Settlements on the Moon or Mars won't be much bigger than buildings on Earth, especially at first. However, in orbit astronauts can move spacecraft weighing many tons by hand. Everything is weightless and this makes large scale construction much easier. Settlements 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 free-space settlements, the total living area created would be hundreds of 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 free-space settlements can service Earth's tourist, energy, materials and other markets more easily than the Moon. Mars is too far away to easily trade with Earth. Space settlements, wherever they are built, will be very expensive. Supplying Earth with valuable goods and services will be critical to paying the bills.

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. Fortunately, there are tens of thousands of suitable asteroids in Near Earth orbits alone, and far more in the asteroid belt.

Early settlements can be expected to orbit the Earth where all the products of Earth's industrial might are available if transportation is sufficient for settlement in the first place. Later settlements can spread out across the solar system one step at a time eventually taking advantage of the water in Jupiter's moons or other icy bodies in the far reaches of the solar system. Eventually the solar system will become too crowded for some, and groups of 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 Proxima? 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.

Why?

Thrive

A key advantage of space settlements is the ability to build new land, rather than take it from someone else. This allows a thriving, expansive civilization 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 settlements. This land can easily support trillions of people.

Survive

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 an extensive branch of our civilization is in space 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 settlements 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 settlement programs, space settlement will build new land, not steal it from the locals as there simply are no locals. Thus, the power and wealth born of space settlement will not come at the expense of others, but rather represent the fruits of great labors.

A Nice Place to Live

There will be little enthusiasm for moving into space unless people want to live there. In that vein, 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 not 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.

How?

With great difficulty. Fortunately, although building space settlements will be very difficult, it's not impossible particularly if we start small and close to Earth. Studies suggesting that small settlements in Low Earth Orbit directly above the equator are practical mean that the first settlements can be much closer, much simpler, and much easier to build than previously believed. Nonetheless, building cities anywhere in space will require radiation protection, materials, energy, transportation, communications, and life support.

• Radiation protection. Cosmic rays and solar flares create a lethal radiation environment in space but settlements in Equatorial Low Earth Orbit (ELEO) are protected from most space radiation by the Earth itself and Earth's magnetic field. Further out, beyond Earth's magnetic field, settlements must be surrounded by sufficient mass to absorb most incoming radiation, about 7-11 tons per square meter depending on the material.
• Materials. Launching materials from Earth is expensive, so for far away settlements bulk materials such as radiation shielding 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, carbon, and at least some nitrogen.
• 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. 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. Transportation for millions of tons of materials from the Moon and asteroids to settlement construction sites is also necessary once settlements expand beyond Earth's magnetic field. One 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. Early settlements close to Earth can plug into Earth's communication system.
• 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.

The tallest poles in the space settlement development tent are launch, construction, and life support. Launch is expensive today because most vehicles are expendable. After a single flight they are thrown away. The keys to reusability are technology and launch rate. There are multiple efforts in progress to develop reusable rocket technology but today's flight rate, less than 100 per year, is completely insufficient. A single reusable vehicle that can fly twice a week can meet that demand. Somewhere above 10,000 flights per year is probably needed, and tourism -- at the right price -- can generate use that kind of flight rate. No other application, with the exception of space solar power, again at the right price, has the potential to require so many flights.

Space tourists will need hotels to stay in. A primitive space hotel is very similar to today's space stations, but does not need expensive scientific equipment. Should early space hotels be successful bigger and better hotels will be built. These hotels will need to provide life support, including recycling the air and water and perhaps even some agriculture. At some point the largest hotels will be the size of a small settlement (~100 m diameter). At that point building the first space settlement is not much more difficult than building yet another hotel.

Space solar power is the other source of high launch demand, although it cannot develop space hotels. 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 space energy systems, it is possible to generate a great deal of electrical power. This can be converted to microwaves or infra-red 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 creating a large profitable business and dramatically reducing pollution.

However, a few commercial firms are developing space stations which could double as space hotels. These may well be deployed in the next decade or perhaps even less. After that we are may need at least two or three decades of hotel development to get to the size of a small settlement. Construction of the first settlement could easily take most of a decade. Thus, somewhere in the neighborhood of 30-50 years from now people may be moving in to the first settlement. We cannot say when the first space settlement will be build but, with a little luck, the right unit of measurement is decades, not years or centuries. In the meantime, there's a lot to do. Better get started!

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 Student Space Settlement Design Contest.

Curator: Al Globus If you find any errors on this page contact Al Globus.

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