The goal of artificial-gravity spacecraft design has always been to support the long-term human habitation of outer space - to provide a "home away from home". But, the reasons behind that goal have changed from time to time.
In the early days, the spread of humanity beyond the confines of Earth was seen as a natural extension of terrestrial colonization - for adventure, freedom, and new opportunities. Tsiolkovsky wrote: "Earth is the cradle of humanity, but one cannot live in the cradle forever" . "Man will not always stay on Earth; the pursuit of light and space will lead him to penetrate the bounds of the atmosphere, timidly at first, but in the end to conquer the whole of solar space" . Oberth wrote: "This is the goal: To make available for life every place where life is possible. To make inhabitable all worlds as yet uninhabitable, and all life purposeful" .
In the Cold War, space habitation became not an option, but an imperative. Collier's editorialized in 1952 that "the U.S. must immediately embark on a long-range development program to secure for the West 'space superiority.' If we do not, somebody else will ... A ruthless foe established on a space station could actually subjugate the peoples of the world" .
The imperative became less military and more econo-environmental upon the publication in 1972 of "Limits to Growth". This report, produced by a group of international experts in business, economics, and technology (which came to be known as the Club of Rome) set out to chart the future of the global economy. Their conclusions were not optimistic. Unless there are drastic changes in industrial civilization at a global scale before the year 2000, their model points toward Malthusian disaster - global economic collapse and famine - within the next century. They predicted that zero population growth by itself would not be sufficient to prevent collapse. The only solution seemed to be an equilibrium steady-state global economy that would cap industrial growth as well [5, 6]. Subsequent studies essentially confirmed these conclusions. Robert Heilbroner concluded in 1974 that "[if] we ask whether it is possible to meet the challenges of the future without the payment of a fearful price, the answer must be: No, there is no such hope" .
Those dire predictions assume that Earth is a closed system. In rebuttal, O'Neill and others point out that continued growth is possible if extraterrestrial resources are utilized. "The material reserves in the asteroid belt are sufficient to permit the construction of new land area totaling 3000 times that of the Earth ... I've argued that a growth rate about a tenth as large as our present explosive increase would be sufficient to make the difference between stasis and change ... For that moderate rate of growth, the resources of the asteroids would be sufficient for at least four thousand years" . This is the vision that motivates populist space-advocacy groups such as the Space Studies Institute, the National Space Society, and the Space Frontier Foundation.
Although NASA sponsored three summer studies in the mid 1970's devoted to large-scale space colonization [9, 10, 11], its current interest in artificial gravity is limited to small scale "utilitarian" applications such as manned missions to Mars. Nevertheless, the dream of colonization is alive in individual employees of NASA and its contractors, many of whom are active in the advocacy groups mentioned above. The frequent use of "romantic" imagery to sell spacecraft projects to the Congress and the People further implies the ultimate goal of large-scale human access to space. Why commission artists' renderings of a space station if nobody but the crew will ever see the thing? If the goals are strictly utilitarian, show the product: space-manufactured crystals, pharmaceuticals, and so on. A space station that is forever off-limits to the general population warrants no more public enthusiasm than any other miscellaneous laboratory equipment.
It may appear that "utilitarian" "engineering" concerns and "aesthetic" "architectural" concerns are at opposite ends of a spectrum. I maintain that both utilitarian and aesthetic considerations are relevant for all habitats, large or small, near-term or far-term. The design goal must always be optimal habitability by the widest possible sample of the general population with the least possible training and acclimation. Limited habitability should be due strictly to technical or economic constraints, not to "pre-compromised" goals. Some significant steps toward habitability may be relatively easy to implement, but the possibility of discovering these may be precluded by pessimistic goals that assume a harsh environment for a carefully-selected highly-trained crew. Furthermore, with highly-disciplined individuals there is always the question of whether symptoms of maladaptation are absent or merely repressed.
Thus, the remainder of this chapter addresses the problem of applying general architectural theory to artificial-gravity environments, to support a heterogeneous population in long-duration space habitation. The next several sections introduce various aspects of architectural theory, with reference to actual micro-gravity experience where possible. Potential applications to artificial gravity are discussed in the final section. For the purposes of this study, I assume a first-generation space population with strong cultural and psychological ties to the Earth. It is both futile and unnecessary for us to guess how space architecture might evolve after several generations of extraterrestrial civilization.