Illustrations of O’Neill’s proposed space colony.

The following are excerpts from Gerard O’Neill’s 1974 Physics Today article, “The Colonization of Space.” Supported by with graphs and calculations, it was the first appearance of his ideas to be shared with the general public:

It is orthodox to believe that Earth is the only practical habitat for Man, and that the human race is close to its ultimate size limits.

But I believe we have now reached the point where we can, if we so choose, build new habitats far more comfortable, productive and attractive than is most of Earth.

We can colonize space, and do so without robbing or harming anyone and without polluting anything.

If work is begun soon, nearly all our industrial activity could be moved away from Earth’s fragile biosphere within less than a century from now.

The technical imperatives of this kind of migration of people and industry into space are likely to encourage self-sufficiency, small-scale governmental units, cultural diversity, and a high degree of independence.

The ultimate size limit for the human race on the newly available frontier is at least 20,000 times its present value.

How can colonization take place? It is possible even with existing technology, if done in the most efficient ways. New methods are needed, but none goes beyond the range of present-day knowledge.

The challenge is to bring the goal of space colonization into economic feasibility now, and the key is to treat the region beyond Earth not as a void but as a culture medium, rich in matter and energy. To live normally, people need energy, air, water, land and gravity. In space, solar energy is dependable and convenient to use; the Moon and asteroid belt can supply the needed materials, and rotational acceleration can substitute for Earth’s gravity.

A Cylindrical Habitat. The geometry of each space community is fairly closely defined if all of the following conditions are required: normal gravity, normal day and night cycle, natural sunlight, an earthlike appearance, efficient use of solar power and of materials.

The most effective geometry satisfying all of these conditions appears to be a pair of cylinders.

The economics of efficient use of materials tends to limit their size to about four miles in diameter, and perhaps about 16 miles in length. In these cylinder pairs, the entire land area is devoted to living space, parkland and forest, with lakes, rivers, grass, trees, animals and birds, an environment like most attractive parts of Earth; agriculture is carried on elsewhere.

Environmental Control. The agricultural areas are separate from the living areas, and each one has the best climate for the particular crop it is to grow.

Gravity, atmosphere, and insolation are earthlike in most agricultural cylinders, but there is no attempt there to simulate an earthlike appearance.

Selected seeds in a sterile, isolated environment initiate growth, so that no insecticides or pesticides are needed. (The evolution time for infectious organism is long, and resterilization of a contaminated agricultural cylinder by heating would not be difficult.)

All food can be fresh, because it is grown only 20 miles from the point of use. The agricultural cylinders can be evenly distributed in seasonal phase, so that at any given time several of them are at the right month for harvesting any desired crop.

Axial Rotation and Transport. A key element in the design of the space colony is the coupling of two cylinders by a tension cable and a compression tower to form a system that is able to maintain its axis pointed toward the Sun without the use of thrusters.

Life in the Colonies. With an abundance of food and clean electrical energy, controlled climates and temperate weather, living conditions in the colonies should be much more pleasant than in most places on Earth.

For the 20-mile distances of the cylinder interiors, bicycles and low-speed electric vehicles are adequate. Fuel-burning cars, powered aircraft, and combustion heating are not needed; therefore, no smog.

For external travel, the simplicity of engineless, pilotless vehicles probably means that individuals and families will be easily able to afford private space vehicles for low-cost travel to far distant communities with diverse cultures and languages.

The “recreational vehicles” of the colonial age are therefore likely to be simple spacecraft, consisting of well-furnished pressure shells with little complexity beyond an oxygen supply and with much the same arrangement of kitchen facilities and living space as are found today in our travelling homes.

All Earth sports, as well as new ones, are possible in the communities. Skiing, sailing, mountain climbing (with the gravity decreasing linearly as the altitude increases) and soaring are examples. As an enthusiastic glider pilot, I have checked the question of thermal scales: The soaring pilots of the colonial age should find sufficient atmospheric instability to provide them with lift.

At high altitudes, man-powered flight — a nearly impossible dream on Earth — becomes easy. A special, slowly rotating agricultural cylinder with water and fish can have gravity 10-2 or 10-3 times that on Earth for skin diving free of pressure-equalization problems. Noisy or polluting sports, such as auto racing, can easily be carried out in one of the cylinders of the external ring.

The self-sufficiency of space communities probably has a strong effect on government. A community of 200,000 people, eager to preserve its own culture and language, can even choose to remain largely isolated. Free, diverse social experimentation could thrive in such a protected, self-sufficient environment.

Our New Options. If we drop our limitation to present technology, the size of a community could be larger. One foreseeable development is the use of near-frictionless (for example, magnetic) bearings between a rotating cylinder and its supporting structure, which need not be spun.

I hesitate somewhat to claim for space-colonization the ability to solve one other problem, one of the most agonizing of all: the pain and destruction caused by territorial wars.

Cynics are sure that humanity will always choose savagery even when territorial pressures are much reduced. Certainly the maniacal wars of conquest have not been basically territorial.

Yet I am more hopeful; I believe we have begun to learn a little bit in the past few decades. The history of the past 30 years suggests that warfare in the nuclear age is strongly, although not wholly, motivated by territorial conflicts; battles over limited, non-extendable pieces of land.

From the viewpoint of international arms control, two reasons for hope come to mind. We already have an international treaty banning nuclear weapons from space, and the colonies can obtain all the energy they could ever need from clean solar power, so the temptations presented by nuclear-reactor byproducts need not exist in the space communities.

To illustrate the power of space-colonization in a specific, calculable situation, we trace the evolution of a worst-case example: Suppose the present population-increase rate were to continue on Earth and in the space colonies. In that case the total human population would increase 20,000-fold in a little over 500 years. Space-colonization would absorb even so huge a growth.

Building the First Colony. A responsible proposal to begin the construction of the first colony must be based on a demonstration, in some detail, of one workable plan with realistic cost estimates.

I emphasize two points about any such plan: The details presented should be thought of simply as an existence proof of feasibility; and many variations are possible. The optimum design and course of action can only be decided on after study and consultation among experts in a number of fields.

I hope I have conveyed at least a little of the sense of excitement that I have enjoyed over the past few years as each serious problem has appeared to yield to a solution, as well as how much more remains to be done and how much need there is for good ideas and hard work.


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