Tuesday, June 3, 2008

O'Neil Cylinders

O'Neil Cylinders: The Exciting Future of Space Colonization
By Ryan Haecker

In a 1798 essay entitled 'an Essay on the Principle of Population', Thomas Robert Malthus speculated, with knowledge of the 18th century English and American population boom, about the potential problems associated with an unsustainable population growth. Before the first modern census(1801) Malthus had correctly foreseen that the population of the western world was rapidly and uncontrollably increasing. With the population of the world expected to approach 9 billion by 2050, the problems of overpopulation and global environmental sustainablility have today an increasing relevance. Since this problem of overpopulation became apparent, futurists and science fiction writers such as K. Drixler, Gerard O'Neil, and Micheal Savage have speculated about the possibility of overcoming the 'Malthusian population limit' through the habiation of artificial worlds outside the confines of the earth. After the Civil War, American writer Edward Everett Hale was the first to write about space habitation in his novel, a 'Brick Moon'. Later in the 19th century, a Russian writer named 'Konstantin Tsiolkovsky tackled the idea more technically in a 1895 science-fiction story, and in 1903 expanded his description to include rotation for artificial gravity, the use of solar energy, and even a space greenhouse with a closed ecosystem...The notion of a rotating wheel-shaped station was introduced in 1929 by Herman Noordung in his Das Problem der Befahrung des Weltraums (The Problem of Space Flight). He called his 30-meter-diameter station "Wohnrad" (Living Wheel) and suggested it be placed in geostationary orbit.'

Space colonization affords man the previously undreamt of oppurtunity of expanding outside the confines of the Earth's habitable biosphere. However, there daunting engineering hurdles that will forestall and inhibit all future attempts to domesticate the vaccuum of space. The first difficulty is that immediate problem of protecting onself from solar radiation. Within the Earth's biosphere, the oxygen rich atmosphere effectively eliminates all harmful radiations. Outside of this protective barrier, humans will be forced to provide their own means of survival. Additionally, there is the problem of interplanetary debrees and micrometeriorites that pose a lethal danger to all artificial spaceborne human environments. To effectively encase a human settlement in the extraterrestrial armor needed to overcome these difficulties will require an enormous space platform to support the necessary thick walls. However this same lethal solar radiation is also essential for human survival. Without the sunlight, either natural or artificial, plantlife cannot grow. Without plants, there can be no natural ecosystem. More importantly, human beings require a natural cycle of day and night to live comfortably and heathily. Any large scale colonization effort will therefore have to reconcile the contradictory demands of providing sunlight while protecting the inhabitants from harmful solar radiation.

Once the problems of atmospheric containment a radiation are overcome, the chief hazard, which will forever inhibit the human habitaiton of space will be that of gravitation. In an environment which lacks the Earth's tremendous gravity, man's bones and muscles will quickly atrophe and whither away. Barring the constructiong of a space outpost with a mass equal to that of the earth, the surest means of overcoming this obstacle will be to find some means of artificially simulating the force of gravity. The aforementioned Konstantin Tsiolkovsky(1903) was the first to write about the possibility of using the centrifugal force of a rotating wheel to produce artificial gravity in space. A wheel shaped space station, once set in motion, could perpetually generate centrifugal force, providing artificial gravity as effortlessly as on the earth. This wheel shaped space station design has proven popular in Hollywood and science fiction, featuring prominently in the Stanley Kubrick masterpiece, 2001: A Space Odyssey. As a circle is the natural extension of any rotating vessel, a spinning wheel is similarly the most logical and efficient design for a small orbital space outpost.

While this wheel shaped design might forseeably serve as a small space station, any signifcant human colonization of space will require a much larger installation. By extending the wheel shape along it's Z-axis we can multiply the amount of habital space within any rotating space colony many times over. Just such a cylindrical space colony was first proposed by Gerard O'Neil in 1974 in his book 'The High Frontier'. Gerard O'Neil's designed called for the construction of a 'gargantuan cylinder with hemispherical end caps, 32 kilometers (20 miles) long and 6.4 kilometers (four miles) in diameter, with a habitable surface area of 325 square kilometers (125½ square miles) or 32,500 hectares (80,310 acres) supporting a population in the tens of millions...Orbiting with one end facing the sun, it’s divided lengthwise into six alternating “ground” and “sky” panels, so only half of the inner surface is actually available for habitation. Three mirrors project outward at a 45° angle from the end facing away from the Sun and reflect sunlight through the translucent “sky” panels to the landscaped “ground” panels opposite them.' This so called 'sunflower' arrangement is the most efficient means of directing natural sunlight unto a rotating orbital platform.

Each of the three valleys within the colony is an elongated rectangle 32 kilometers (20 miles) long and 3.2 kilometers (two miles) wide, yielding a total area of 105 square kilometers (40 square miles). The six cities and their associated suburbs cover an area of 41.4 square kilometers (16 square miles) each. The three rural areas cover an area of 20.7 square kilometers (eight square miles) each, which must be shared evenly between the two urban/suburban centers at either end. WIthin these cylinders, gravity will be 'simulated' through the centrifugal force of the rotating colony.'The simulated “gravity” resulting from the rotation varies from one “G” at the base of the mountain to zero-G at the apex. The drop-off is linear—at the 1.6-kilometer (one-mile) level, midway (45°) up the mountainside, the pseudo-gravity is 50% (½ G). You can calculate the acceleration that produces this pseudo-gravity using the formula F=rω²/g, where F is the resulting acceleration, r is the distance from the central axis, ω is the angular velocity (a constant equal to 2π times the number of rotations per second) and g is the acceleration due to gravity experienced on Earth (9.80665 m/s² or 32.174 ft/s²).'

The three problems which inhibit the human colonization of space are: One, the problem of effective solar lighting and a day and night cycle. Two, the necessity of artificial gravity. And three, the containment of the atmosphere and protection from the radiation and vacuum of space. O'Neil's design was important because it is the most logical and efficient design to handle all three of these design problems. Through his rotating cylindrical design, O'Neil overcomes the problem of artificial gravitation. With the mirrors and windows reflecting solar light, O'Neil's design creates an artificial day and night cycle, as well as generating solar energy. Finally, the massive quartz windows and moon rock exterior effectively protects and contains the internal atmosphere.

Although O'Neil cylinders are technically constructable with existing technology, their enormous size and requisite expense will prevent anything of this sort from being built in the near future. In the distant future, as space flight becomes more practicable and population pressures become more acute, we may come to consider the necessity and enjoyment of living outside the Earth's atmosphere. For this purpose, O'Neil cylinders offer humanity a bright and hopeful, ecologically sustainable future.

Additional Reading:

No comments: