A hovercraft, also known as an air-cushion vehicle (ACV), is a versatile marine, land, or amphibious vehicle which supports its weight on a high-pressure air cushion maintained by one or more horizontal fans. Because this minimizes the friction between the craft and the ground, vertical fans can maintain speeds up to 160km/h (100mph), even over difficult surfaces. Hovercraft are invaluable for negotiating swamps, and are used as marine ferries and military vehicles. Smaller, less speedy craft have been developed as runabouts.
A hovertrain is a high-speed train that uses an air cushion to support it just above a special track. Ground-effect machines (GEMs) are sometimes distinguished from ACVS as, like airplanes, they derive most of their lift from their aerodynamic design and forward motion.
The air-cushion principle was rediscovered by the British engineer Christopher Cockerell in the early 1950s.
Related category TECHNOLOGY
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