Space Settlements, or Space Colonies, first received serious attention in the mid-1970's, with interest primarily fueled by two NASA-sponsored studies led by Dr. Gerard O'Neill and conducted at Stanford University during the Summers of 1975 and 1976. Participants in these studies published books and articles that first appeared in the aerospace technical community, and eventually were popularized through book clubs and general-circulation magazines. Science fiction authors wrote stories and novels about characters living on space settlements. Technical societies sponsored conferences where details of construction and operations were presented. Architects designed prototype communities as a model for how humans would live in space. College degrees were earned with Masters theses about space settlement design. At the peak of their popular attention, the counterculture Whole Earth Catalog enthused about the concept of space colonies, and Dr. Timothy Leary (yup, the LSD guy) did lecture tours, and interview shows on TV and radio, about how wonderful life would be in space.
From their beginnings, the most contentious issue concerning settlements-in-space was the huge development, maintenance, and logistics cost, primarily due to the expense of launching thousands of tons of goods and materials into orbit. In order to make the concept work, a compelling economic necessity had to be found, and conveniently presented itself in the energy crisis and oil embargo of the early 1970's. Solar Power Satellites became an almost obvious solution to the energy crisis: build a structure in space up to three miles wide and 20 miles long, cover the structure with solar panels, and generate ten gigawatts of electricity. Such large structures would, however, require humans to build them and human attention for maintenance. There would be demand for lots of Solar Power Satellites, so we would need places for their builders to live in space, and space settlements would provide an environment in which they could feel right at home. This whole scenario may have been a bit naive, but the studies were done, dreams were kindled, and a lot of people decided they would be ready to pack their belongings and go live on the new frontier in space just as soon as the first space settlement was ready to go. An organization called the L5 Society was founded, proclaiming in its By-laws that its last meeting would be held on the first space colony, its purpose for existing then having been fulfilled (the L5 Society merged with the National Space Society, and consequently that By-laws provision no longer exists).
Although numerous concepts were sketched for space settlements, the research of the 1970's produced three primary designs, each solving the design challenge with a somewhat different approach. Figure 1a shows an exterior view of a Stanford Torus, the design that the NASA-sponsored studies developed to an impressive level of detail. The torus is one mile in diameter, and rotates at one rpm in order to produce one g of acceleration to simulate gravity. The cross-section of the torus interior is about 420 feet, and it could accommodate a population of 10,000 living inside, with all agricultural crops and services required to sustain them. Other major features are a large mirror "floating" above the settlement, reflecting sunlight to solar panels that generate power and smaller mirrors around the hub that then direct daylight into the living areas of the torus; and a facility for refining lunar ores to be used in Solar Power Satellite construction, which is isolated from the habitable areas by a six-mile-long transportation tube. Figure 1b represents a residential area of the Stanford torus, and shows that the designers envisioned an environment with open space, greenery, and low-rise housing. Some artists' Stanford Torus interior views showed brooks and jogging trails.
The Bernal Sphere, shown in Figure 2a, was a spherical approach to the design problem. This design was also intended for a population of 10,000, who would live in the spherical volume in the middle. Sunlight is directed into the interior of the sphere by mirrors at either "end" of the spherical section. The banded toruses, extending from either side of the habitation sphere, house the agricultural areas. This shape made construction easier, and could afford the possibility of maintaining different climates or seasons in different toruses in order to grow a variety of crops. Figure 2b shows an interior view of a Bernal Sphere, again illustrating the designers' priority for providing green areas and the appearance of low-density housing.
The most ambitious of the space settlement designs was Island Three, shown in Figure 3a. The twin counter-rotating cylinders are four miles in diameter and twenty miles long, claimed to be large enough to accommodate a population of up to ten million people. The cylinders are made up of three land areas about two miles wide, alternated with three window areas of the same width; mirrors angled from one end of each cylinder reflect sunlight into the windows. The small pods ringed around the other end of each cylinder provide agricultural and manufacturing areas. The interior view shown in Figure 3b depicts almost a rural population density; written descriptions noted village-like population centers dotted over hundreds of square miles of terrain.
A general consensus of space settlement designers was that a logical place for these structures is at one of the Earth-Moon libration points. There are five Lagrange libration points in a system where a large body is in orbit around a much larger body (e.g., the Moon in orbit around the Earth); these are places where the gravitational forces due to both objects "balance out" in a way that enables a settlement to stay in one spot relative to both objects. Figure 4 shows these places, called "Libration Points". "L4" and "L5" are the most stable of the five; they are on the same orbital path as the Moon, one-sixth of the way around in either direction from where the Moon is (equivalent to the locations where the Trojan asteroids have collected in the Jupiter-Sun system). Because of the perturbations of other objects in the solar system, these are not discreet spots; objects placed in these areas will go into large orbits around the actual points. Indeed, a large number of space facilities could be placed "at" L4 and L5. The other three libration points act somewhat like "saddles"--if an object is perturbed and drifts a small distance, it will tend to continue drifting away until it assumes a more normal orbital path. Objects could, however, be kept in these locations if their engines are used to continually nudge them back where they belong.
Some of the best data developed during the NASA space settlement studies resulted from analyses of human needs. Excerpts from some of the Tables that presented these data are included.
In the late 1970's, NASA funding for space settlement research was discontinued, and gradually the enthusiasm waned. Most people forgot about the energy crisis, and for a time the priority of space enthusiasts was to save any manned space program at all. Only a few individuals expressed the conviction that it was still inevitable people would eventually live in space on a large scale, although they knew that the hoped-for timetables ("L5 in '95!") would not be met.
In the past few years, however, more brave souls have been revisiting the idea of large-scale habitats in space, and some venturesome individuals are again publicizing the idea that Solar Power Satellites are a reasonable alternative to conventional power plants. The key to a revival of serious consideration of space settlements is transportation costs. Government and industry are beginning to demonstrate a commitment to develop launch vehicles that could lift payload into orbit for as little as $500 per pound. That is still a huge expense, but makes some commercial ventures feasible that could not possibly generate a profit with today's launch costs of $2,500 to $10,000 per pound. There also is also finally a funded program for returning missions to the Moon; establishment of a lunar base could lead to mining operations that would provide a relatively inexpensive source of materials for space settlement construction.
|Public and semipublic|
|Rec. and entertain||1||3|
|Public open space||10||50|
|Plant growing areas||44||15|
|Food processing, collection, storage, etc.||4||15|
|Agriculture drying area||8||15|
|Dry Plant Produce||Wheat||180||608||130.1||3.6||24.3|
Beef steer: 1 steer for 11 persons Harvested at 400 kg after 16 months Metabolic requirements for 1 / 11 250 kg steer 300 g sorghum mix/day 200 g soybean mix/day Roasting Chicken: 5.6 chickens / person Harvested at 2.6 kg after 25 weeks Metabolic requirements for 5.6 kg at 1.1 kg each 37 g fish meal/day 150 g soybeans/day Rabbits Harvested at 3.4 kg after 125 days Metabolic requirements for 2.8 rabbits at 1.8 kg each 100 g sorghum/day 100 g soybeans/day 20 g corn/day Dairy Cattle 400 g cow produces 12.45 kg milk/day Metabolic requirements for 1 / 16.6 cow at 400 kg 350 g sorghum mix/day 100 g soybean mix/day Laying Hens 1.5 kg hen lays 5 eggs/week, 54 g/egg Metabolic requirements for 6/10 hen at 1.5 kg 20 g soybeans/day 30 g corn/day Fish Harvested at 2 kg in 1 year Metabolic requirements for 26 fish at 1 kg each 100 g soybeans/day 81 g animal meal/day
Anticipated Settlement Yields Crop g/m2 / season season g / m2 / day (days) -------------------------------------------------- Wheat 2800 90 31 Rice 3192 90 35 Soybeans 1800 90 20 Corn 5300 90 58 Sorghum 7560 90 83 Tomatoes & Lettuce 9240 70 132