Navy lags in mine-fighting technology

In early 1942 as the United States hurried to prepare for World War II, German U-boats laid hundreds of mines along the Eastern Seaboard of North America. Taken by surprise, shipping stopped at harbors from Canada to the Gulf of Mexico as the US struggled to clear away the threat. One crucial port, Charleston, S.C., was blocked for 16 days. ``The Germans effectively closed everything down,'' says a mine expert for a Washington defense firm.

Forty-five years later this humble weapon continues to give the US Navy fits. Recent events in the Persian Gulf have shown that mine warfare is still low on the Pentagon's list of priorities.

But even as the Defense Department rents merchant ships for service as instant minesweepers in the Gulf, experts say the most important question is whether the US could prevent its own ports from being blocked in the event of a superpower conflict.

Adm. Carlisle Trost, chief of naval operations, said in an interview this spring with Armed Forces Journal that the Soviet Union is clearly better at mine warfare than the US and will be ``for the foreseeable future.''

Many classes of Soviet submarines, as well as bombers and ships, are capable of laying mines. A Pentagon source claims the USSR has a stockpile of 100,000 moored mines, which are set off by contact with a ship, and 200,000 newer types, which are exploded by the sound of propellers or the magnetic field of a hull.

One of the most modern Soviet mines, code-named Cluster Gulf by NATO, is essentially a torpedo that waits on the bottom of the continental shelf. When it hears a passing ship or sub, this weapon ignites a rocket motor. Guided by internal sensors, it zooms up toward its target. The Soviets are also thought to have a small number of nuclear mines.

``In the last several years the Soviets have developed a deep-water, open-ocean mine capability,'' said Everett Pyatt, assistant Navy secretary for shipbuilding, at a recent Pentagon briefing.

Clearing an area of moored contact mines, such as those found in Gulf waters, can be done with straightforward sweeping. A ship or helicopter drags an arrangement of wires and sharp cutters through the water, much as if it were mowing a lawn.

Clearing mines that explode from magnetism, sound, or pressure and rest on the bottom can be more difficult. The US plans to do it with helicopters towing sleds that imitate the attributes of a larger ship. One sled, the MK-104, uses a propeller in a tube to imitate the sound of powerful ship engines; another, the MK-105, uses energized electrodes to create a ship's magnetic field. These, however, only work in relatively shallow waters.

The navies of a number of US allies now employ mine-hunting submersibles - tiny remote-control submarines that swim around searching for mines, and destroy those they find by dropping explosive charges. One such sub, the French PAP 104, is used by six nations. The Italian MIN and German Pinguin B3 are similar.

A US mine-hunting submersible, the MNS, is being developed by Honeywell. As yet the US has no mother ship to run it from.

The first of 14 proposed modern Avenger-class minesweepers, with nonmagnetic hulls of oak and fir, is now on sea trials. The project is years late though because of engine and electronics development problems. Smaller MHC-51 coastal mine-hunters are also on order. The MHC program replaces an ambitious air-cushion minesweeper whose design troubles caused it to be canceled in 1986.

Along with 23 Sea Stallion helicopters, the US minesweeping force now includes 21 aging ships, with only three on active duty. Some experts say that to build up its force the US should buy off-the-shelf items from its allies rather than wait for its own designs. One possibility is the Tripartite minesweeeper built by a Netherlands-France-Belgium consortium and outfitted with a PAP submersible.

``Except for helicopters, our allies have better minesweeping technology than we do,'' says Scott Truver, a naval analyst at Information Spectrum Inc.