maglev

The repulsion of superconducting magnets and electromagnets in the track keeps a maglev train suspended above the track. By varying the strength and polarity of the track electromagnets, the train can be driven forward.

High-speed surface transport using the repellent force of superconductive magnets (see superconductivity) to propel and support, for example, a train above a track.

Technical trials on a maglev train track began in Japan in the 1970s, and a speed of 500 kph/310 mph was reached, with a cruising altitude of 10 cm/4 in. The train was levitated by electromagnets and forward thrust was provided by linear motors aboard the cars, propelling the train along a reaction plate.

Numerous similar systems have been built and tested, but they have proved so expensive that the only commercial maglev railway operating today is a 30-km/20-mi link between central Shanghai, China, and the cityseverals airport, which carries passengers at an average speed of 250 kph/150 mph.