E

Mechanical Methods

Mechanical devices have been used to counter mines with varying degrees of success. Such devices include:

• Bottom trawls. Based on the British use of bottom trawls drawn from the fishing trade to remove mines lying proud of the bottom, along with moored mine anchors, during World War II, experiments were carried out by the Woods Hole Oceanographic Institution in the 1950s and by the Navy in the early 1980s. As with the British wartime experience, these tests indicated that only slightly modified bottom trawls, whose lower edge penetrates a few inches into relatively soft sand or mud bottoms, were successful in picking up all bottom mines in their path except for those completely buried. Operationally, ensnared mines would be towed periodically from the channel being cleared and deposited in a holding area for later neutralization. The depth of water must be sufficient for the trawler and its operation.
• Heavy chains. The previously noted, joint amphibious mine countermeasures (JAMC), including a heavy chain drawn over the ground by two D-7 or D-8 bulldozers to clear surface-resting and partially buried land mines, is intended primarily for use in clearing mines from an assault beach and, perhaps with the addition of a snorkel, out to the surf zone. Bulldozers use plows to clear mines from their own path. However, the plow must cover the full width of the bulldozer, not just the tracks, or the bulldozer itself will become a victim of magnetic and tilt-wand mines passing between the plows. Because of the difficulty of insertion and hookup on a mined beach (particularly one with obstacles), the slow rate of clearance, the vulnerability of the chain to tilt-wand and sensitive magnetic mines, and the unlikelihood of effectively clearing tough obstacles, it would seem that JAMC is best suited to the larger cleanup job following the initial assault.
• Clausen Power Blade (CPB). The Clausen Power Blade offers a single unique feature: a conveyor belt made from the street track of a dozer, capable of running in either direction and oriented vertically across the front of a D-7. In trials conducted on land, the system has demonstrated its ability to clear an 11-foot swath of land mines buried down to around 10 inches, removing obstacles of up to 4,000 pounds. Mines, obstacles, and the excavated material are stacked in the berm to one side of the vertical conveyor belt mounted above the narrow cutting blade. In these tests, the relatively slow rate of advance, cushioning of the excavated material, and manner in which the smooth surface of the conveyor belt shifts the material to one side reduce the chance that pressure mines will be detonated. To the knowledge of the panel, tests have not been run against magnetic, tilt-wand, and trip wire mines. Neither has the vulnerability of the cutting blade and the conveyor system to a mine blast been tested. The absorption of explosive energy by the mound of dirt before the conveyor may reduce damage to some degree. The conveyor system is a unique addition to the mechanical removal of land, beach, and surf zone mines and obstacles. However, the CPB suffers from difficulty of insertion during the early phases of an assault; its rate of clearance is relatively slow; the berm containing removed mines must be dealt with; and likely delays due to the vulnerability of the blade and conveyor system to mine blast make this, like JAMC, more suited to the larger removal job following the initial assault.
• Wattenberg Plow (WP). Designed at LLNL and recommended for consideration by the JASONs during Desert Shield, the Wattenberg Plow is a new approach to the mine plow concept. The strongback with vertical cutting knives at 4-inch spacings, behind a blanket of cross-linked chains, is towed from a distance of 600 feet by a helicopter at speeds up to 20 knots. The knives are torque mounted so that they ride over immovable objects to prevent breaking, and the chain mat is there to keep the system stable and on the ground under tow. A wire basket is mounted on the chain mat to catch mines that are excavated and pass over the strongback. Half-scale tests have indicated that the system can be towed effectively at speeds up to 20 knots, and the system as a whole can perform and survive very well. Static tests with an antitank mine indicated that the system suffered only minor damage that could be repaired quickly and inexpensively in the field. The vulnerability of the helicopter makes it unlikely that the system would be used in the early phases of an amphibious assault or in the breaching of a land minefield subject to cover by artillery. Demonstration of the prototype indicates that although it is useless against obstacles, the plow can be effective in removing mines from inland minefields and from the surf and craft landing zones and would be particularly useful in humanitarian demining. Tests have also demonstrated the helicopter's ability to pick up the WP system and redeploy it for another pass.
• Guinea pig ships and barges. Platforms with a signature large enough to activate mines, and "ruggedized" to accept several mine blasts before suffering incapacitating damage, constitutes an old MCM concept. Liberty ships of around 10,000-ton displacement with skeleton crews standing on mattresses to prevent broken bones were used to sweep against U.S. forces' pressure influence mines in the waters around the home islands of Japan following World War II. The Minesweeper Special (MSS) program of the 1960s modified a ship of similar size by using water ballast to reduce shock wave impedance, styrofoam to provide extra buoyancy in case of flooding, deck-mounted long-stem Marion Tregurtha outboard power plants in case of shaft misalignment or propeller damage to the ship's own power system, and a shock-mounted pilot house for the seven-man crew. Tests indicated that the MSS suffered only minor structural damage, and no personnel damage, from a 2,000-pound mine detonated 35 feet off the beam at a depth of 65 feet. A modified tank landing ship (LST) was used as a guinea pig to proof the Haiphong harbor minefields cleared by Operation Endsweep. The guinea pig concept has been tested, it has utility under certain MCM conditions, and it should not be allowed to drop from the corporate memory.

The panel notes the utility of an unmanned, remotely controlled, GPS-navigated barge with sufficient independent compartments, filled with buoyant material such as hardened polymer foam, to withstand several mine blasts of the type expected in the surf zone to high water mark. Once larger mines have been cleared from the deeper water where they will most likely occur, such a barge could provide a channel of its own width to the beach. Precise tracking of the barge as it proceeded would allow accurate definition of a "proven" channel and would allow similarly GPS-equipped assault vehicles to transit safely to the beach. The guinea pig barge could be remotely controlled or have a one- or two-man crew on a shock-mounted platform at the stern. It could also carry enough rigid polyurethane foam material to build a mine-masking road from its bow to the back-beach area, with sufficient bearing strength to be used by vehicles up to the size and weight of tanks. The barge could, of course, be stopped at the first line of obstacles, which may extend as far seaward as the surf zone.