Ground-Effect Machine, Marine

(marine GEM; also called marine air-cushion vehicle [ACV]), a vessel that is supported above the surface of the water by air forced underneath, which thereby reduces resistance to the vessel’s forward motion. The first design for a vessel that would glide on a layer of compressed air between the vessel’s underside and the surface of the water was proposed by the Swedish scientist E. Swedenborg in 1716. One of the first marine GEM’s was a torpedo boat built in 1916 for the Austrian Navy.

The theoretical basis for transport on an air cushion was formulated by K. E. Tsiolkovskii in 1927. The first Soviet marine GEM was developed under the direction of Professor V. I. Levkov; it was tested in 1934 and 1935 on water, snow, and land. In the mid-1960’s, marine GEM’s began routine service in the navy and as passenger vessels.

In plenum-chamber machines, air is fed under the dome-shaped hull from a centrally located fan. In air-curtain machines, air is forced through nozzles located around the perimeter of the hull. A GEM gliding over choppy water is stabilized by confining the air cushion to the area under the hull, thus preventing heeling and trim differences. In marine GEM’s designed to remain fully above the water, the air cushion is confined to the vessel’s perimeter by flexible elements, such as articulated skirts. Vessels of this type are driven by airscrews or air-breathing jet engines and are capable of speeds of 100–150 km/hr. Marine GEM’s with flexible or rigid aprons that remain immersed in the water reach speeds of 60–100 km/hr; they are driven by conventional or water-jet propellers.

Marine GEM’s are used as car and passenger ferries, naval landing craft, and the like.