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DMS
Destroyer Minesweeper
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 number for such a ship began "DMS". Forty-two ships were so converted, beginning with the USS Dorsey (DD-117), converted to DMS 1 in late 1940, and ending with the 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 hull numbers beginning MMD.
The original ships were obsolete four-stack destroyers built during and after World War I with usable power plants. The number 4 boiler, fourth stack, and torpedo tubes were removed,depth charge racks repositioned forward from the stern and angled outboard, and the stern modified to support sweep gear: davits,winch,paravanes, and kites. Two 60-kilowatt turbo-generators replaced the three original 25-kilowatt generators to improve capability for sweeping magnetic and acoustic mines.
Conversion of the initial seventeen ships was completed in October and November 1940, and included eight Wickes class and nine Clemson class destroyers. An additional Wickes class destroyer was converted in 1941. The fictional USS Caine from Herman Wouk's novel The Caine Mutiny was such a ship. The 24 later ships in the series were Gleaves class destroyers built during the war.
Minehunters are mine countermeasure vessels that actively detect and destroy individual naval mines. Minesweepers, on the other hand, clear mined areas as a whole, without prior detection of mines. A vessel that combines both of these roles is known as a mine countermeasures vessel (MCMV). A minehunter uses an imaging sonar to detect and classify targets and then sends out divers or remotely operated vehicles to inspect and neutralise the threat, often using small charges that are detonated remotely. As minehunters will often be operating in close proximity to mines, they are designed so as to reduce their own acoustic and magnetic signatures, two common forms of trigger for mines. For example, they are often soundproofed by mounting machinery on shock absorbers or by using quiet electrical drive and usually have a wood, glass-reinforced plastic (GRP) or non-ferrous metal hull, or are degaussed to reduce magnetic signature. Minehunters are generally small, shallow-draught vessels, as they are often called upon to work in enclosed bodies of water such as shipping channels or harbours. As manoeuvrability in such areas is critical the Voith-Schneider cycloidal propulsor is commonly used, allowing the engine thrust to be transmitted in any direction. A number of modern vessels use catamaran hulls to provide a large, stable working platform with minimal underwater contact; this reduces draught whilst lowering acoustic transmission and reducing the fluid pressure generated by the moving hull that may otherwise detonate mines with a hydraulic pressure trigger.
A mine countermeasures vessel or MCMV is a type of naval ship designed for the location of and destruction of naval mines which combines the role of a minesweeper and minehunter in one hull. The term MCMV is also applied collectively to minehunters and minesweepers
Minesweepers are equipped with mechanical or influence sweeps to detonate mines. The modern minesweeper is designed to reduce the chances of it detonating mines itself; it is soundproofed to reduce its acoustic signature and often constructed using wood, glass-reinforced plastic (GRP) or non-ferrous metal, or is degaussed to reduce its magnetic signature. Mechanical sweeps are devices designed to cut the anchoring cables of moored mines, and preferably attach a tag to help the subsequent localization and neutralization. They are towed behind the minesweeper, and use a towed body (e.g. oropesa, paravane) to maintain the sweep at the desired depth and position. Influence sweeps are equipment, often towed, that emulate a particular ship signature, thereby causing a mine to detonate. The most common such sweeps are magnetic and acoustic generators. There are two modes of operating an influence sweep: MSM (mine setting mode) and TSM (target setting mode or target simulation mode). MSM sweeping is founded on intelligence on a given type of mine, and produces the output required for detonation of this mine. If such intelligence is unavailable, the TSM sweeping instead reproduces the influence of the friendly ship that is about to transit through the area. TSM sweeping thus clears mines directed at this ship without knowledge of the mines. However, mines directed at other ships might remain.
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