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.
- Rather than live on the outside of Earth, space colonists will live on the inside of gigantic spacecraft.
Typical space settlement designs are 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.
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
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.
- 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 about 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.
Similarly, 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
Mars also has dust storms which interfere with solar power.
- Great views of 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 magnificent view of the stars at night.
Any settlement on the Moon or Mars will also have a view of an 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.
See Earth Views from Space
for a fine collection of views of Earth from space.
- 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 that weightlessness is fun.
and dance go to a new level when the constraints of gravity are removed.
It's not going to be easy to keep the kids in the 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 a 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
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.
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.
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
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
- 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)
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 air breathing hypersonic air/spacecraft under development by NASA and others.
Transportation for millions 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 current terrestrial communications already pass through
- 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 archived
with materials 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:
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.
- 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.
- Within 5 years 3,000 tourists will have been to space.
- Within 15 years sub-orbital tourism will be affordable, and 50,000 people will have flown.
- Within 15 years the first, expensive orbital tourist flights will have happened.
- Within 25 years orbital tourism will be affordable.
- 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.
- 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
- 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.
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:
- 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.
- The ultimate gated community. On Earth it is essential that
diverse groups learn to live in close proximity.
It's hard to live with five
or six billion homo sapiens, and some people
can't seem to do it gracefully.
Space settlements offer an alternative to changing human nature or
endless conflict -- the ability to live in fairly homogeneous groups,
as has been the norm throughout hundreds of thousands of years of human existence.
Those who can't get along can be separated by millions of miles of
hard vacuum, which in some cases seems necessary.
All entry into a space settlement must be through an airlock, so controlling
immigration should be trivial.
- 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 the weather system every hour. Like to go barefoot? Make the
entire environment foot-friendly.
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.
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
How long did it take to build New York? California? France?
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.
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
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
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