O'Neill cylinder
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The O'Neill cylinder also called Island Three is a space habitat design proposed by physicist Gerard K. O'Neill in his book, The High Frontier. In the book O'Neill proposes the colonization of space for the 21st century, using materials from the Moon.
An Island Three consists of two very large counter rotating cylinders, 3 km radius and 20 km long, that are connected at each end by a rod via a bearing system. They rotate so as to provide spin gravity on their inner surfaces.
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[edit] Background
While teaching undergraduate physics at Princeton University in 1969, he had students design large structures in space, with the intent to show that living in space could be desirable. Several of the architectures were able to provide areas large enough to be suitable for human habitation. This cooperative result inspired the idea of the cylinder and was first published by O'Neill in a 1974 article in Physics Today.
[edit] Islands One, Two and Three
O'Neill's created three reference designs:
- Island One was basically a sphere measuring one mile in diameter which rotated, and people lived on the equatorial region. See Bernal Sphere
- Island Two was a toroidal shape, also known as the Stanford torus
- Island Three consists of two counter-rotating cylinders each two miles (3 km) in radius, and capable of scaling up to twenty miles (30 km) long. [1] Each cylinder has six equal-area stripes that run the length of the cylinder; three are windows, three are "land." Furthermore, an outer agriculture ring, as seen in the picture on the right, 10 miles (15 km) in radius, rotates at a different speed for farming. The manufacturing block is located at the middle (behind the satellite dish assembly) to allow for minimized gravity for some manufacturing processes.
These habitats were to be built with materials launched into space with a kind of magnetic catapult called a mass driver.
[edit] Artificial gravity
The cylinders rotate to provide artificial gravity on their inner surface. Due to their very large radius, the habitats would rotate about once per minute, while giving a standard Earth gravity. NASA experiments in rotating reference frames indicate that almost no-one would experience motion sickness because of coriolis effects in their inner ears due to this low rotation speed. People would be able to detect spinward and antispinward directions by turning their heads, however and dropped items would be deflected by a few centimetres.
The central axis of the habitat would be a zero gravity region, and it was envisaged that it would be possible to have recreational facilities located there.
[edit] Atmosphere and radiation
The habitat was intended to use a reduced air pressure of about half Earth sea-level. This saved gas as well as reducing the necessary thickness of the habitat walls.
At this scale, the air within the cylinder and the shell of the cylinder provide adequate shielding against cosmic rays.
[edit] Sunlight
To permit light to enter the habitat, large windows run the length of the cylinder. These were not to be single panes, but would be made up of individual sections, of considerable thickness, so as to be able to handle the pressure of the atmosphere in the habitat. Occasionally a meteorite would break one of these panes, which would cause some loss of the atmosphere, but calculations showed that this would not be an emergency, due to the very large volume of the habitat.
Large mirrors are hinged at the back of each stripe of window. The unhinged edge of the windows points toward the Sun. The purpose of the mirrors is to reflect sunlight into the cylinders through the windows. Night is simulated by opening the mirrors, letting the window view empty space; this also permits heat to radiate to space. During the day, the reflected Sun appears to move as the mirrors move, creating a natural progression of Sun angles. Although not visible to the naked eye, the Sun's image might be observed to rotate due to the cylinder's rotation. As an aside, the light reflected from the mirrors is polarized, which might confuse bees.
[edit] Attitude control
Although the counter-rotating habitats have no gyroscopic effect, it's highly desirable to be able to control the pointing ("attitude") of the habitats to keep the mirrors correctly angled towards the sun. To do this, O'Neill and his students carefully worked out a method of aiming the habitats. First, the pair of habitats can be rolled by operating the cylinders as momentum wheels. If one habitat's rotation is slightly retarded, the two cylinders will rotate about each other. Once the plane formed by the two axes of rotation is perpendicular (in the roll axis) to the orbit, then the pair of cylinders can be yawed to aim at the sun by exerting a force between the two sunward bearings: away from each other will cause both cylinders to gyroscopically precess, and the system will yaw in one direction, towards each other will cause yaw in the other direction.
[edit] O'Neill cylinders in science fiction
Robert A. Heinlein, in his 1963 novelisation Orphans of the Sky (compiling two stories published in 1941), introduced revolving cylinders to emulate gravity. In this case there were many concentric levels, at which gravity stepwise-decreased towards the centre of the structure, resulting in zero gravity at the very centre.
In the Harry Harrison-edited SF-artwork book "mechanismo", an illustration of "island three" is shown alongside technical notes (Mechanismo 1978, page 68)
In the Rama series of books by Arthur C. Clarke, gigantic alien spacecraft similar to O'Neill cylinders are explored by astronauts. Perhaps due to its design for interstellar travel, Rama lacks the mirrors and windows of an O'Neill cylinder, but does have lights arranged in three strips along its length, paralleling the placement of the windows. Note that Rendezvous with Rama was published (1973) in the period between O'Neill running the classes in which his cylinder design was produced and his publication, therefore the designs are likely entirely independent.
Jerry Pournelle and John F. Carr edited an anthology of SF stories set in O'Neill cylinders or other types of space colonies, published in 1979 as The Endless Frontier volumes 1 and 2.
In the Gundam anime science fiction series, O'Neill cylinders are common—especially in the Universal Century, where nine billion human beings live in these colonies. The Gundam series space colony design is usually portrayed with a rotational speed much faster than the original O'Neill design. This is in part for visual effect.
Vonda N McIntyre's Starfarers series of novels is set on the Starfarer, a classic O'Neill double-cylinder space colony adapted to make FTL interstellar jumps.
The Hyperion Cantos by Dan Simmons makes multiple references to a massive war effort between mankind and an offbranch subspecies of humanity who travel through deep space using what essentially amount to O'Neill cylinders mounted on engines. They are affectionately referred to as 'canships' by the universe's more vulgar population.
The science-fiction television series Babylon 5 concerned an O'Neill-style space station five miles (8 km) long. While the single cylinder Babylon 5 did not feature a counter-rotating section, its predecessor Babylon 4 did (Babylon 4 echoes the "Island One" concept). Like Rama, Babylon 5 lacks the mirrors and windows of an O'Neill cylinder, but does have a fixed central light source. Day and night are simulated as the landscape below revolves around the light source.
In Ken Macleod's Learning The World, the 'Sunliner' Slow interstellar travel vessel But the Sky, My Lady! the Sky!, is based around an O'Neil Cylinder with a central artificial 'sunline' (a miniature star strung out like an oversized tubular fluorescent bulb) that is simply activated and deactivated on a 24 hour cycle, rather than relying on windows. On either end is a 'cone' together containing a bridge, maintenance systems, spare reaction fuel and propulsion/power grid systems.
Alexis A. Gilliland, a science fiction writer, proposed a "dragon scale mosaic mirror". This would consist of a cone of aimable mirrors around each habitat. These could provide illumination, generate power, and defend the habitat. The area of the array would be much larger than that of O'Neill's design, but wouldn't have to be built to take the stress of rotating with the habitat.
An O'Neill cylinder similar to those found in the Gundam series provides the setting for a stage in the game Tekken 5. The arena consists of a glass platform mounted near the axis at one end of the habitat, with the rotating cylinder providing the backdrop. The stage is called "The Final Frontier", and the exterior can be seen in a cutscene. The view through the window would suggest that the facility is much nearer to the earth than the typical scenario.
Peter F. Hamilton's The Night's Dawn trilogy makes several references to an O'Neill halo orbiting Earth. The books aren't specific, but imply that's it built out of asteroid materials. Also the Edenist culture of the books are said to inhabit huge Habitats that are slight variation on the O'Neill Cylinder, though biologically made with a central light tube running through the centre of the structure rather than the mirror panels proposed in the original design. His Commonwealth Saga books also describe the character Ozzie Isaacs' home, which is an O'Neill cylinder located within an asteroid.
Hideo Kojima's science fiction adventure game, Policenauts , takes place in an O'Neill space colony located at the L5 Lagrange Point. These structures can also be seen in shooting games like Axelay (stage 2), Zone of the Enders (stage 1), Super Earth Defense Force (stage 4), R-Type Final (stage 1), Thunder Force IV (Ruin stage), GG Aleste (stage 1), and probably many more...
The Neyel, a fictional race in the Star Trek novel The Sundered (by Andy Mangels and Michael A. Martin), were originally Earth humans who lived on Vanguard, an O'Neill-type habitat constructed inside an asteroid. (The name 'Neyel' is itself derived from O'Neill.)
The Galactic Whirlpool, a Star Trek novel written by David Gerrold, focused on an O'Neill-style space station that had been retro-fitted as a generational interstellar ship.
In the video game series Halo, the Halo itself was a ring-shaped megastructure bearing some similarities to an O'Neill cylinder.
Gene Wolfe's series The Book of the Long Sun take place on a Generation ship, essentially a massive O'Neill cylinder, where the inhabitants have long forgotten that they are on a ship or journey. The series is followed by The Book of the Short Sun and is also linked to Wolfe's master work, The Book of the New Sun.
Orson Scott Card's novel Ender's Game concerns mostly the events taking place on Battle School, a short O'Neill cylinder, which houses the all-important Battle Room in the center of its rotation, which keeps it at null gravity.
In the Italian science fiction comic book Nathan Never, Earth has spawned a number of space colonies in the form of O'Neill cylinders.
[edit] See also
[edit] References
- O'Neill, Gerard K. (1977). The High Frontier: Human Colonies in Space. William Morrow & Company. ISBN 0-688-03133-1.
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