Elon Musk has stated that he wants to make human beings a “multiplanetary species” by establishing a self-sustaining human colony on the planet Mars. While this is a sensible and laudable goal for the immediate future, in the long run there are much better places to establish human colonies in the Solar System. The best way to move humanity off Earth was outlined forty-nine years ago by visionary Gerard O’Neill in his book The High Frontier.
There are very significant challenges in constructing a human colony on Mars. The environment is harsh. The average surface temperature on Mars is about minus 80 F, and the planet is subject to abrasive dust storms that can last for months. The atmospheric pressure of Mar’s carbon dioxide atmosphere is only 1 percent that of Earth’s. Mars lacks a magnetic field, and human beings on the surface will be exposed to damaging levels of both cosmic and solar radiation. Mars’ gravity is 38 percent that of Earth, and people living under low gravity for long periods of time may experience health problems including bone density loss, muscle atrophy, and cardiovascular disease. Perhaps most worrisome of all is the lack of a reliable and powerful energy source. Potential solar power on Mars is only 40 percent that of Earth due to increased distance from the Sun and blockage by dust in the Martian atmosphere. The importation of nuclear power from Earth is possible, but only at great expense and difficulty.
None of the preceding challenges are insurmountable, but there are much better places establish human colonies in space. As Gerard O’Neill explained, it’s entirely feasible to construct artificial cities in space near Earth-Moon LaGrange points L4 and L5. These locations are 585 times closer to Earth than Mars and there is sufficient space to house a human population that is of the order of 10 billion, comparable to Earth’s present population of 8.2 billion. Living conditions in these stations will resemble the Garden of Eden, unsurpassed in comfort and quality of life.
A significant advantage to O’Neill colonies is the availability of vast amounts of power from solar insolation. Solar power on Earth is limited by atmospheric blockage, the Earth’s rotation, and oblique impingement at most latitudes. Altogether, the intensity of solar radiation in outer space is about 5 to 7 times higher than can be harvested on Earth. Furthermore, this number can be increased arbitrarily by focusing and reflecting sunlight onto photovoltaic panels with mirrors. Compared to the surface of Mars, the solar power potential will be at least ten to twenty times greater.
Human beings require 100 percent Earth-normal gravity for optimal health. This is easily provided on an O’Neill colony by rotation. O’Neill described rotating spheres or pairs of cylinders that can house 10,000 to as many as 10,000,000 people. While living quarters can be maintained at Earth-normal gravity, other areas of these space cities will experience much lower gravity which can be exploited for recreational activities such as human-powered flying.
No one wants to live in a sterile, artificial environment that is cramped, without trees, grass, sunlight, parks, gardens, or flowers. All of these amenities will be present in an O’Neill colony. Sunlight can be brought inside through mirrors and windows. Every personal residence will have a garden and perhaps an orchard. There will be green spaces, parks, and bodies of water. Both plants and animals can be introduced to form stable ecological communities. Butterflies, honey bees, and hummingbirds will be included, but obnoxious species such as ticks, mosquitos, and cockroaches will be strictly excluded. Weather will be perfect, day after day, year after year. Both temperature and humidity will be set at optimum levels for human comfort. Natural hazards will be absent. There will be no earthquakes, tsunamis, hurricanes, volcanic eruptions, landslides, floods, droughts, tornadoes, or wildfires. On Earth, it’s virtually impossible to stop an epidemic disease like Covid, influenza, or the Bubonic Plague from spreading through the entire human population. In space it will be a relatively simple matter to confine and limit a plague through quarantines. While it is true that space itself provides hazards in the form of radiation and meteorites, shields can be constructed to protect from these.
Given sufficient energy, information, and raw materials, anything permitted by the laws of nature is feasible. Nearly all of the materials needed to construct space cities can be found either on the Moon or in the Asteroid Belt. The Moon is rich in silicon, oxygen, iron, aluminum, titanium, and magnesium. Water can be found in permanently sheltered craters. Because the Moon’s gravity is relatively weak, raw materials can be efficiently and inexpensively lifted into space using a nuclear-powered catapult. Volatile elements such as carbon, nitrogen, and sulfur are scarce on the Moon, but can be mined from asteroids. Moving materials from the Asteroid Belt to near-Earth orbit will be a challenge, but is facilitated by the fact that the transport will in effect be downhill, toward the Sun and lower potential energy. Rocket fuel itself can be obtained from carbonaceous asteroids by extracting and processing carbon, hydrogen, and oxygen. Perhaps the greatest challenge will be locating and moving quantities of nitrogen, essential for agriculture and to generate Earth-like atmospheres.
Food production on an O’Neill-type space colony will be straightforward. Human beings have extensive experience growing plants under controlled conditions in greenhouses. In space, production of edible plants will be engineered for optimization of light, temperature, and humidity. There will be no need to use pesticides, because all harmful weeds, insects, viruses, and fungi will be excluded from the beginning. Greenhouse atmospheres can be supplemented with carbon dioxide to speed plant growth. Techniques such as vertical farming and hydroponics will be utilized. All plant nutrients, water, and human waste products will be recycled endlessly. What makes such ideal systems feasible is the availability of virtually unlimited electric power from solar energy. Animal husbandry in space will be more challenging. Aquaculture of fish is certainly possible. Chickens and turkeys need relatively little space, pigs a little more. Cows require significant space, about one acre per animal, but it’s possible to envisage specialized structures entirely devoted to meat and milk production. The maximum human living area on a large O’Neill colony is about 800 square kilometers (197,684 acres), so a specialized colony could support approximately 100,000 animals. Even if this rough estimate is too high by a factor of ten, production facilities with 10,000 animals could supply significant amounts of food.
The construction of human colonies in space will undoubtedly be the greatest engineering and construction project in human history. While this superficially appears to be a hopelessly difficult and complex task, it can be easily accomplished by breaking it down into small steps. This is a principle known to every computer programmer. Large and complex programs are written as a series of short subroutines. Once the subroutines are tested, they can be assembled into a large program that runs flawlessly. There is nothing new about incrementalism. A lever is a form of mechanical incrementalism, whereby small movements are used to move heavy weights. The Gothic Cathedrals of the High Middle Ages were constructed by repeating relatively simple patterns of ribbed vaults and pointed arches. Stone blocks were chiseled to standard sizes and dimensions using molds and templates.
Since O’Neill published The High Frontier in 1976, much of what was then speculation is now a straightforward extrapolation of existing and well-established trends. The development of reusable rockets, technological advances, commercialization, and economy of scale have caused the cost of moving material out of the Earth’s gravity well to drop by nearly two orders of magnitude, from about $50,000 (2020 $US) per kilogram to $100 to $1500. There have been significant advances in machine learning, artificial intelligence (AI), and robotics. AI will be able to write perhaps 80 to 90 percent of the computer code necessary. The abilities of humanoid robots are in a nascent, but rapidly evolving stage. At the present time, robots can replace humans in perhaps 30 percent of tasks, but it is likely that this number will rise to 70 or 80 percent in a few decades. In the last 50 years, the efficiency of photovoltaic cells that provide electric power has approximately doubled, from about 10-12 percent to 23-25 percent. Research panels have reached efficiencies in the range of 40-50 percent.
The rate at which space colonies are constructed will be slow at first. There will be a period of initial investment before construction activity can begin. The establishment, for example, of lunar and asteroid mining operations will require significant allocation of resources with little to no return for several years. There will be continuous increases in efficiency and productivity though trial-and-error, and the rate of construction will increase dramatically as time passes.
The prospect of living in an artificial structure in space no doubt incurs horror and revulsion in some people. But the move to space is only the culmination of a long-term trend that began hundreds of thousands of years ago when people first sought to shelter themselves by stretching animal hides over wooden poles. No one desires to live naked in the woods. And there is a great advantage to a large human population. Larger populations facilitate the specialization of labor that drives human progress. There will be more people who can innovate, maintain, and transmit knowledge and complex skills.
The movement of humanity into space will also increase human freedom and reduce conflict and war. Historically, the leading causes of war have been competition for resources, territorial disputes, and disagreements concerning religion, economics, and culture. Space offers abundant resources for everyone. Solar energy is unlimited, and the amount of raw material that is available in the Solar System is enormous. Incentives for theft and depredation will be removed. At some point, the technology will be sufficiently advanced that a structure capable of housing a million people can be constructed by simply pushing a button. People with different ideas, cultures, and religions will be able to live any way they choose. An Islamic space city, for example, could be governed by Sharia Law. A libertarian city would minimize regulations and the size of government. And communists can construct utopian communities with shared property and guaranteed income.
Most people will choose to live in space because the quality of life in space will be superior to that on Earth. Human population on Earth will be reduced to a caretaking staff, and the entire planet can be turned into a park and nature preserve. The Earth’s natural environment will be both preserved and restored. Toxic waste dumps and environmental damage will be cleaned up and repaired by robotic labor. Millions of bison will once again roam the Great Plains of North America, and wolves will repopulate the continent. People will visit Earth the same way they visit Yellowstone Park today.
The movement of humanity into space is not the end, but a beginning. It will be a prelude to interstellar travel and the slow spread of human colonies throughout the galaxy. The experience and knowledge gained in robotics and artificial intelligence will be used to send robotic probes to promising stars. Once it arrives, a probe will survey a chosen stellar system to see if that system has the raw materials and energy to sustain human life. If so, each autonomous probe by itself will begin reproducing and constructing the machines necessary to fabricate an entire world suitable for human habitation. This is the process nature itself uses when an oak tree grows from an acorn: a small amount of initial energy combined with information is utilized to gather energy and materials from the environment to fabricate a structure of arbitrary size and complexity. The process of interstellar migration will be slow, due to the enormous distances involved, but it is conceivable, if not inevitable, that biological science will be capable of extending human lifespan. The future is just beginning.
