Technology: Assault on an Air Cushion

• Share

The 65-ft. landing craft that skittered across the water and up a Lake Erie beach last week looked like a product out of science fiction, a warship from some future conflict. Huge fans to port and starboard blasted downward into sand and foam; giant propellers in the stern shoved the vehicle along as it carted its cargo of armed marines through a mock invasion. The strange craft moved at speeds up to 80 m.p.h. without touching either land or water.

To the military observers on the shore, though, the scene was less a picture of the future than a promise of a new and better landing craft for today's troubles. The Bell Aerosystem's Hydro-skimmer was built for the Navy, but it is only one of a score of air-cushion vehicles now being developed for military and commercial usage by such old-hand defense contractors as Republic Aviation, Grumman Aircraft, General Dynamics and Martin-Marietta.

The aluminum Hydroskimmer moves on a thin cushion of air; it gets its lift from the powerful blast of the four turbine-driven fans in the ship's hull. Once the skimmer is balanced on its air cushion, the two propellers in the stern roar into action. Starting from a spot 25 miles off the Erie beach, the Hydro-skimmer landed its marines in less than 30 minutes, traversed the last 600 yds. in less than 40 sec., minimizing exposure to potential enemy fire, maximizing the element of surprise. In addition, the marines were landed on the beach itself instead of being dumped into shallow water; none of them suffered from the assault trooper's nemesis, seasickness.

One successful test, however, does not make a fleet of Hydroskimmers, and numerous problems remain to be solved. For one, the craft moves so fast as it approaches a beach that the helmsman has almost no time to avoid bad landing spots. Little is known about how the Hydroskimmer handles in a rough sea, and a heavy surf might damage the craft's engines.

But some of these same bugs have already been worked out of smaller air-cushion vehicles, such as the 40-ft. British-made Hovercraft that Bell was demonstrating last week for oil company executives in Galveston Bay. Wearing a rubber skirt around its waist to prevent leakage of the air cushion and to ward off obstacles, this vehicle even cleared a 4½-ft. fence to show off its agility. In what may be the first military use of an air-cushion vehicle, the British plan to send a pair of armed Hovercraft to Borneo late this month for use against Indonesian terrorists.