[Author note: I have invented very little, if anything, new concerning space colonies. Most information about them in Robot Dawn comes from the studies of Gerard K. O’Neill at Stanford University in the 1970s, although I have deviated from his concepts in significant ways. I attended Stanford University in 1968 and received my master’s degree in astronautical engineering from there in 1969, several years before O’Neill’s space colony study.]
In the year 2070, several space colonies populate the Solar System. First of all, and although it isn’t actually a “space” colony, the lunar colony at the south pole of the Moon — situated on the lip of the Shackleton crater — was the first constructed. It was designed and initial construction started in the 2020s but wasn’t completed until the early -30s. Tourism to the south pole in 2070 was still heavy but constitutes only twenty-five percent of industry there. Morale is poor and worker turnover high. Population at any one time is estimated at two-hundred, with another three-hundred robots working the mines for precious materials. Several other lunar colonies followed, most around the lunar equator and in lunar lava tubes, one located at the volcanic domes in Marius Hills and another at Mons Hadley, a massif in the Moon’s northern hemisphere.
First on Mars in significant numbers toward the end of the 2020s, private corporations built the initial stages of a settlement they named Ares Interplanetary Colony, AIC, at Chryse Planitia, where the first Viking lander touched down in 1976. Five years later they sold it to the United Federation of the Solar System, the Uni-Feds, when the presence of poisonous perchlorate, which had been known to exist everywhere on Mars from the time of NASA’s Phoenix Lander in 2008 but was thought to be a minor problem, proved to be an overriding issue. Inadvertent contact with perchlorate had led to the deaths of five colonists. Since then, the abandoned development now in the hands of government professionals had grown substantially to house upwards of 1,500 colonists, all affiliated with the government. Renamed the Percival Lowell District of Mars (Lowell DM), it functioned as the hub of a complex network of buildings for both scientific research and tourism, plus of course a large mining and manufacturing component, mostly for use at Lowell and other smaller government facilities scattered about.
The total population of Mars approached 10,000 men, women, and children. The largest concentrations were at Valles Marineris, where mining operations were everywhere, and industrial resources congregated; and Hellas Planitia, the huge impact basin in the southern hemisphere. The rest were primarily scientific enterprises scattered all over the planet but under the auspices of the University of Mars. Thought to be a desert during the initial decades of robotic exploration, Mars proved to have subsurface water everywhere, as were the resources to purify it, the technology cheap, readily available, and easily implemented. Once proved safe for human habitation, colonization of Mars happened quickly.
The largest space station is at Lagrange point SE-L4, where the two interconnected O’Neil colony cylinders, each 5 miles (8 kilometers) in diameter and 20 miles (32 kilometers) long, reside. Since the cylinders have to spin about their longitudinal axis to provide one-g at the internal edge, they have to occur in pairs to counteract gyroscopic precession. O’Neil was built primarily from materials mined on the Moon at a collection of temporary sites all over the surface. More recently, materials have been obtained by mining capture astroids brought close to SE-L4 by spacetugs.
The second largest is the military complex at EM-L5, where all configuration information is top secret.
The above figure shows the relationship between the diameter of a space colony cylinder and its required rotation rate to produce one-g on the interior. Note that as the diameter of the cylinder gets larger, the required rotation rate for one-g goes down. For the DSO Torus it is one revolution per minute. For the O’Neil cylinder, it is almost one-half revolution per minute. The governing equation is:
Gs = r x ω^2
Research has shown that one rpm is comfortable for humans, but some can withstand four rpm without a great deal of disorientation. Coriolis forces are the primary concern.