Minesweeping is the practice of removing explosive naval mines, usually by a specially designed ship called a minesweeper using various measures to either capture or detonate the mines, but sometimes also with an aircraft made for that purpose. Minesweeping has been practiced since the advent of naval mining in 1855 during the Crimean War. The first minesweepers date to that war and consisted of British rowboats trailing grapnels to snag the mines. [1]
A sweep is either a contact sweep, a wire dragged through the water by one or two ships to cut the mooring wire of floating mines, or a distance sweep that mimics a ship to detonate the mines. The sweeps are dragged by minesweepers, either purpose-built military ships or converted trawlers. Each run covers between 100 and 200 meters (330 and 660 ft), and the ships must move slowly in a straight line, making them vulnerable to enemy fire. This was exploited by the Turkish army in the Battle of Gallipoli in 1915, when mobile howitzer batteries prevented the British and French from clearing a path through minefields.
If a contact sweep hits a mine, the wire of the sweep rubs against the mooring wire until it is cut. Sometimes "cutters", explosive devices to cut the mine's wire, are used to lessen the strain on the sweeping wire. Mines cut free are recorded and collected for research or shot with a deck gun. [2] Before the First World War, the Imperial Russian Navy officer Pyotr Kitkin invented "mine protectors" to break a sweeping wire before it could cut the mine's mooring wire. [3]
Minesweepers protect themselves with an oropesa or paravane instead of a second minesweeper. These are torpedo-shaped towed bodies, similar in shape to a Harvey Torpedo, that are streamed from the sweeping vessel thus keeping the sweep at a determined depth and position. Some large warships were routinely equipped with paravane sweeps near the bows in case they inadvertently sailed into minefields—the mine would be deflected towards the paravane by the wire instead of towards the ship by its wake. More recently, heavy-lift helicopters have dragged minesweeping sleds, as in the 1991 Persian Gulf War. [4] [ failed verification ]
The distance sweep mimics the sound and magnetism of a ship and is pulled behind the sweeper. It has floating coils and large underwater drums. It is the only sweep effective against bottom mines.
During the Second World War, RAF Coastal Command used Vickers Wellington bombers Wellington DW.Mk I fitted with degaussing coils to trigger magnetic mines. [5]
Modern influence mines are designed to discriminate against false inputs and are much more difficult to sweep. They often contain inherent anti-sweeping mechanisms. For example, they may be programmed to respond to the unique noise of a particular ship-type, its associated magnetic signature and the typical pressure displacement of such a vessel. As a result, a mine-sweeper must accurately guess and mimic the required target signature to trigger detonation. The task is complicated by the fact that an influence mine may have one or more of a hundred different potential target signatures programmed into it. [6]
Another anti-sweeping mechanism is a ship-counter in the mine fuze. When enabled, this allows detonation only after the mine fuze has been triggered a pre-set number of times. To further complicate matters, influence mines may be programmed to arm themselves (or disarm automatically—known as self-sterilization) after a pre-set time. During the pre-set arming delay (which could be days or weeks) the mine would remain dormant and ignore any target stimulus, whether genuine or faked. [6]
When influence mines are laid in an ocean minefield, they may have various combinations of fuze settings configured. For example, some mines (with the acoustic sensor enabled) may become active within three hours of being laid, others (with the acoustic and magnetic sensors enabled) may become active after two weeks but have the ship-counter mechanism set to ignore the first two trigger events, and still others in the same minefield (with the magnetic and pressure sensors enabled) may not become armed until three weeks have passed. Groups of mines within this mine-field may have different target signatures which may or may not overlap. The fuzes on influence mines allow many different permutations, which complicates the clearance process. [6]
Mines with ship-counters, arming delays, and highly specific target signatures in mine fuses can falsely convince a belligerent that a particular area is clear of mines or has been swept effectively because a succession of vessels have already passed through safely.
Aircraft can also be used for minesweeping. During the Second World War, fifteen British Vickers Wellington bombers were modified to carry a large magnetic induction loop and an electrical generator. The "Directional Wireless Installation" (DWI), a cover story for the true purpose of the magnetic loop, was used successfully on 10 May 1940, to sweep a path for the escape of the Dutch royal family to the UK. The DWI was used most successfully in the Mediterranean Theatre, particularly over the Suez Canal and Alexandria Harbour. Their use revealed the limitations of the technique, in that it only works effectively in very shallow water (such as canals and harbours). From about 1943, German Junkers Ju 52 transports were similarly converted. Blohm & Voss BV 138 MS tri-motor flying boats were also used for this purpose.
The MH-53E Sea Dragon helicopter is used primarily by the United States Navy to tow several types of mine hunting or mine sweeping gear through the water. It replaced the earlier, RH-53A and RH-53D variants of the Sikorsky CH-53 Sea Stallion. Other examples of minesweeping helicopters include the RH-3A variant of the Sikorsky SH-3 Sea King, as well as the Mi-14BT variant of the Mil Mi-14 and the MCH-101 variant of the AgustaWestland AW101.
A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any vessel or a particular vessel type, akin to anti-infantry or anti-vehicle mines. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to protect friendly vessels and create "safe" zones. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake an expensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where the greatest concentration of enemy firepower will be encountered.
A minesweeper is a small warship designed to remove or detonate naval mines. Using various mechanisms intended to counter the threat posed by naval mines, minesweepers keep waterways clear for safe shipping.
USS Chandler (DD-206/DMS-9/AG-108) was a Clemson-class destroyer in the United States Navy. She was the only ship named for William Eaton Chandler, who served as Secretary of the Navy from 1882 to 1886.
The Aggressive-class minesweepers are a class of US-built minesweepers. They are designated as MSO, distinguishing them from the smaller coastal MSCs and inshore MSIs. Besides the US Navy, this class of vessels has also been used by the Belgian Navy and the Norwegian Navy, among others.
Type 352 Ensdorf-class minesweepers are a class of five minesweepers of the German Navy. They are Type 343 Hameln-class minesweepers that have been upgraded with the Troika Plus system of minesweeping drones
An Oropesa is a streamlined towed body used in the process of minesweeping. The role of the Oropesa is to keep the towed sweep at a determined depth and position from the sweeping ship. Oropesa are standard devices used on Avenger-class mine countermeasures ships.
The North Sea Mine Barrage, also known as the Northern Barrage, was a large minefield laid easterly from the Orkney Islands to Norway by the United States Navy during World War I. The objective was to inhibit the movement of U-boats from bases in Germany to the Atlantic shipping lanes bringing supplies to the British Isles. Rear Admiral Lewis Clinton-Baker, commanding the Royal Navy minelaying force at the time, described the barrage as the "biggest mine planting stunt in the world's history." Larger fields with greater numbers of mines were laid during World War II.
Destroyer minesweeper was a designation given by the United States Navy to a series of destroyers that were converted into high-speed ocean-going minesweepers for service during World War II. The hull classification symbol for this type of ship was "DMS." Forty-two ships were so converted, beginning with USS Dorsey (DD-117), converted to DMS-1 in late 1940, and ending with USS Earle (DD-635), converted to DMS-42 in mid-1945. The type is now obsolete, its function having been taken over by purpose-built ships, designated as "minesweeper (high-speed)" with the hull classification symbol MMD.
USS Threat (AM-124) was an Auk-class minesweeper acquired by the United States Navy for the dangerous task of removing mines from minefields laid in the water to prevent ships from passing.
Caracara (AMc-40), an Accentor-class minesweeper placed in service by the U.S. Navy for use during World War II. The vessel was named after the Caracara, a large South American bird of prey.
USS Scurry (AM-304) was a steel-hulled Admirable-class minesweeper constructed for the U.S. Navy during World War II. She was crewed by sailors who were trained in minesweeping, and quickly sent to the Pacific Ocean to clear minefields so that Allied forces could invade Japanese-held beaches. For this dangerous work, often under enemy fire, she was awarded four battle stars.
USS Redhead (AMS-34/YMS-443) was a YMS-1-class minesweeper of the YMS-135 subclass built for the United States Navy during World War II. She was the first U.S. Navy ship to be named for the Redhead duck.
USS Auk (AM-38) was a Lapwing-class minesweeper acquired by the United States Navy after World War I to remove mines that had been placed during the war.
The Royal Naval Patrol Service (RNPS) was a branch of the Royal Navy active during both the First and Second World Wars. The RNPS operated many small auxiliary vessels such as naval trawlers for anti-submarine and minesweeping operations to protect coastal Britain and convoys.
Operation End Sweep was a United States Navy and United States Marine Corps operation to remove naval mines from Haiphong harbor and other coastal and inland waterways in North Vietnam between February and July 1973. The operation fulfilled an American obligation under the Paris Peace Accord of January 1973, which ended direct American participation in the Vietnam War. It also was the first operational deployment of a U.S. Navy air mine countermeasures capability.
The Natya class, Soviet designation Project 266M Akvamarin, were a group of minesweepers built for the Soviet Navy and export customers during the 1970s and 1980s. The ships were used for ocean minesweeping.
HMS Shoulton (M1182) was a Ton-class minesweeper of the Royal Navy. Constructed by the Montrose Shipyard in Montrose, Scotland and launched on 10 September 1954, the minesweeper was converted into a prototype minhunter in 1957. The vessel was used as a test bed in the mid-1960s for new propulsion technologies. Shoulton was among the vessels assigned to salvage operations following the Aer Lingus Flight 712 crash off Rosslare. In 1977, Shoulton took part in the naval review marking the Silver Jubilee of Elizabeth II and was paid off on 23 November 1979. The ship was sold for scrap in 1981 and broken up at broken up in Blyth.
A Sperrbrecher, was a German auxiliary ship of the First World War and the Second World War that served as a type of minesweeper, steaming ahead of other vessels through minefields and detonating them with their reinforced hull. Also used as anti-aircraft ships, the Sperrbrecher suffered heavy losses in the war.
The Fleet-class unmanned surface vessel, also called the Common Unmanned Surface Vessel (CUSV) and later the Mine Countermeasures Unmanned Surface Vehicle, is an unmanned surface vessel designed for the United States Navy to be deployed from Freedom and Independence-class littoral combat ships and intended to conduct mine and anti-submarine warfare missions. As of 2012 four units of the class have been built; the first was delivered to the U.S. Navy in 2008.