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Avenger Class Navy Mine Hunters

June 2012 Military Power

Jason Thompson
Jun 1, 2012
The U.S. Navy’s Secret Weapon In The Persian Gulf
About three decades ago, the U.S. Navy began development of a new mine countermeasures (MCM) force, which included two new classes of ships and minesweeping helicopters. The importance of an updated MCM force was made clear in the Persian Gulf during the eight years of the Iran-Iraq war, and in Operations Desert Shield and Desert Storm in 1990 and 1991. These Avenger Class ships were designed as mine sweepers capable of finding, classifying, and destroying moored and bottom mines that lay on the sea floor. The last three MCM ships were purchased in 1990, bringing the total to 14 fully deployable, oceangoing Avenger Class ships. These ships use sonar and video systems, cable cutters, and other remotely controlled mine-detonating devices. The ships have a wooden hull construction sheathed in fiberglass, so they are less likely to set off magnetic mines.
Photo 2/5   |   The mine countermeasures ship USS Gladiator (MCM 11) transits the Arabian Gulf; an SH-60 Sea Hawk flies alongside.
Sea Mines = More Bang for the Buck
Mines are relatively cheap compared to the damage they can do to an expensive vessel. Mines manufactured and sold in a global market have stealth technology, computer controls, irregular shapes, nonmagnetic natures, ship counters, anechoic (sound-deadening) coatings, remote control features, and delayed arming devices, which make the U.S. Navy’s job of finding them very challenging. This is compounded by the anti-sea-mine warfare program’s history of neglect and underfunding, according to a report by Captain Gregory J. Cornish in 2003. He believes the United States forgets about the importance of mine countermeasures—conflict after conflict going all the way back to the Revolutionary War. The report concludes advances have been made, but mine countermeasures is a less glamorous area compared to others—although it is very important.
Diesel Power Battles Mines
According to the report from Naval Engineer Agnes Mayeaux at the Massachusetts Institute of Technology (MIT), the four diesel engines found in the Avenger Class MCM ships have a prelube oil priming pump. Under normal cruising, each shaft is driven by either one or two main propulsion diesel engines through a flexible coupling, a pneumatically operated tube-type friction clutch, and a single-stage Philadelphia Gear reduction. When the ship is going less than 8 knots, or when the crew wants to minimize noise, the propellers can be directly connected to the electric motors. The diesel engines provide power for the electric generators. They also emit low sound and magnetic signatures.
Mine Countermeasures Ships: Avenger Class
Builder: Peterson Shipbuilders, Sturgeon Bay, Wisconsin, and Marinette Marine, Marinette, Wisconsin
Propulsion: Four Waukesha (early production) or four Isotta Fraschini (later production) diesel engines; two 200hp electric motors; one gas turbine generator; one 350hp electro-hydraulic bow thruster; and two inboard turning, controllable-pitch propellers
Model: Isotta Fraschini 36 SS6 V-AM, non-reversing, four-cycle diesel
Rated load: 600 hp
Cylinders: Six
Bore and Stroke: 6.693x6.693 inches
Piston Displacement: 235 cubic inches
Compression ratio: 13:2:1
Turbochargers: Twin
Length of Ship: 224 feet
Beam: 39 feet
Displacement: 1,312 tons with a full load
Speed: 14 knots (16 mph)
Crew: 8 Officers and 76 enlisted




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