magnetic levitation

magnetic levitation or maglev măgˈlĕv [key], support and often propulsion of objects or vehicles by the use of magnets. The magnets used in magnetic levitation suspend an object free of contact with any surface, making it particularly appropriate for high-speed (275–300 mph/435–475 km/h) transportation, where it greatly reduces friction and allows for fast, quiet operation. In a typical system, the vehicle, which resembles a railroad or monorail car, travels along a guideway; use of a low-pressure tube to enclose the guideway, reduce drag, and increase speeds by two to three times standard maglev speeds has been proposed.

In one version of the guideway system, magnets of like polarity repel each other to lift the train above the guideway; in another, magnets of opposite polarity attract the part of the car suspended below the guideway up toward the guideway, raising the rest of the car above it. By continuously changing the polarity in alternate magnets, a series of magnetic attractions and repulsions is created that moves the vehicle along the track. The electrical energy required for such a system is great and an obstacle to wide use, but the use of magnets made of superconducting materials (see superconductivity) reduces energy needs.

A maglev transportation system was first proposed by Robert Goddard in 1909, but research into such systems has been conducted only since the 1960s, in the United States, Great Britain, Japan, Germany, and other nations. Research into the use of a low-pressure tube to enclose a maglev train was begun in the 21st cent. Maglev technology was applied in England in the construction of a fully automated, low-speed shuttle in Birmingham, but the line was closed because of maintenance problems. In 1996 funding was approved in Germany for a maglev train linking Berlin and Hamburg, but it was canceled in 2000. In 2004 a maglev line linking Shanghai's financial district with its airport began commercial operation; the train can reach speeds of 268 mph (432 km/h) along its 18.6 mi (30 km) route.

See I. Baldea, New Ways: Tiltrotor Aircraft and Magnetic Levitating Vehicles (1991).

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