O'Neill cylinder
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The O'Neill cylinder is a space habitat design proposed by Gerard K. O'Neill in his book The High Frontier. O'Neill was a physicist at Princeton. In 1969 he taught undergraduate physics. Dr. O'Neill decided to teach by having students design large structures in space. To the surprise of everyone, several designs appeared that used ordinary materials (steel and glass), and could provide large areas suitable for human habitation. This cooperative result was first published by O'Neill in a 1974 article in Physics Today.
O'Neill's reference design, "Island Three", consists of two counter-rotating cylinders each two miles (3 km) in radius, and twenty miles (30 km) long. Each cylinder has six equal-area stripes that run the length of the cylinder. Three of the stripes are windows. Three are "land." Furthermore, an outer agriculture ring , as seen on the picture on the right, of 10 miles (15 km) in radius will be rotating at a different speed for farming. The manufacturing block will be located at the middle (behind satellite dish part) to have minimized gravity for some manufacturing processes.
The cylinders rotate to provide simulated gravity on their inner surface. NASA experiments in rotating reference frames indicate that almost no-one would experience motion sickness because of coriolis effects in their inner ears. People would be able to detect spinward and antispinward directions by turning their heads, however. At this scale, the air within the cylinder and the steel shell of the cylinder provide adequate shielding against cosmic rays.
Large mirrors are hinged at the back of each stripe of window. The unhinged edge of the windows points toward the Sun. The intent 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 permits heat to radiate to space. During the day, the Sun moves as the mirrors move, creating a natural progression of Sun angles. However, the Sun's image might be observed to rotate. The light reflected from the mirrors is polarized, which might confuse bees.
As they orbit, the gyroscopic effect of the rotating cylinders would naturally cause the habitat's mirrors to stop pointing at the sun. 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 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.
O'Neill cylinders in science fiction
- In the Universal Century, After War and Cosmic Era timelines of 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. In the Universal Century, the group of colonies are known as Sides. The Gundam series space colony design is currently the most recognized and realistic. In a pinch, their highly durable design made for an effective weapon of mass destruction if a faction could defend it long enough to send it into the atmosphere.
- 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.
- The science-fiction television series Babylon 5 starred an O'Neill style space station five miles long (sans windows). While the single cylinder Babylon 5 did not feature a counter-rotating section, its predecessor did.
- In the Rama series of books by Arthur C Clarke, gigantic alien spacecraft similar to O'Neill cylinders are explored by astronauts.
- The Hyperion Cantos 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.
- A variation of the O'Neill cylinder is found in Greg Bear's novel Eon. The Stone is a giant hollowed-out asteroid containing six vast rotating chambers, two of which contain abandoned cities. The Stone's seventh chamber appears to extend to infinity.
- An O'Neil 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.