Aggressive-class minesweeper

USS Constant (MSO-427) in 1988
Class overview
Name:	Aggressive class
Operators:	United States Navy Republic of China Navy Belgian Navy Royal Norwegian Navy Royal Netherlands Navy Philippine Navy
In commission:	1953–Present
Completed:	53
Preserved:	2
General characteristics
Type:	Minesweeper
Displacement:	853 tons (full load)
Length:	172 ft (52 m)
Beam:	35 ft (11 m)
Draft:	10 ft (3 m)
Propulsion:	4 × aluminum block Waukesha diesels, 2,400 bhp (1,800 kW) 2 × shafts 2 × controllable pitch propellers
Speed:	14 knots (26 km/h; 16 mph)
Complement:	7 officers, 70 enlisted
Sensors and processing systems:	AN/SQQ-14 mine hunting sonar
Armament:	1 × twin 20 mm gun 2 × .50 cal (12.7 mm) twin machine guns

The Aggressive-class minesweepers are a class of US-built minesweepers. They are designated as MSO (Mine Sweeper Ocean), 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.

Background

Minesweeping, or the disposal of naval mines, by these vessels is performed in different ways:

• Sweeping proper, with an underwater cable cutting the mooring cables of moored mines. The mines then come to the surface and are destroyed by gunfire.
• Acoustic sweeping, with a towed device producing noise to trigger acoustic mines.
• Magnetic sweeping, with a towed device producing a magnetic field to trigger magnetic mines. To protect the minesweeper itself against magnetic mines, the hull and superstructure of the ship are made of wood. Other components are made of non-magnetic materials, and any magnetic materials are strictly controlled.

Construction and disposition

Of the 53 constructed for the United States Navy, 10 were built at Higgins Corp., New Orleans, Louisiana, 9 at J.M. Martinac Shipbuilding Corp., Tacoma, Washington, 8 at Wilmington Boat Works Inc., Wilmington, California, 6 at Luders Marine Construction Co. of Stamford, Connecticut, 4 at Broward Marine Inc, Fort Lauderdale, Florida, 4 at Martinolich Shipbuilding Co., San Diego, California, 3 at Burger Boat Company, Manitowoc, Wisconsin, 3 at Colberg Boat Works, Stockton, California, 2 at Fulton Shipyard, Antioch, California, 2 at Norfolk Naval Shipyard and 2 at Seattle Shipbuilding and Drydocking Co., Seattle, Washington.

33 of the class were decommissioned before the mid-1970s. Four ex-USN ships were sold to the Republic of China Navy 1994 and re-classed as Yung Yang-class minesweepers. They were still in active service in 2012. USS Implicit was decommissioned 30 September 1994 in Tacoma, Washington and was the last Aggressive-class minesweeper in US Navy active service.

General development of minesweeping

Minesweepers have been in operation since World War I and originally involved a simple metal detector, which sailors used to locate naval mines. This practice was dangerous not only from the risk of missing and detonating a mine, but also because the enemy would be making the task harder for the sweepers by keeping them under constant, heavy fire. Minesweepers were greatly admired by their peers because of their bravery.

Aggressive-class minesweepers used AN/SQQ-14 mine hunting sonar to locate moored or bottom mines. They used electromagnetic cables to set off mines or other cables to cut their mooring lines, and various magnetic and acoustical devices to set off mines. Toward the end of their use, the class also employed remote submersibles like Super Sea Rover to locate and classify mines.

Today, active minesweepers or minehunters are frequently used. The Royal Navy of the United Kingdom uses small submarines that are controlled by wireless operators on board the several minesweeping frigates that it possesses. Sweden produced a robotic Self-propelled Acoustic/Magnetic Minesweeper (SAM), which proved its worth during Operation Desert Storm, when it was successfully used for minesweeping by the US Navy. SAMs are currently in service with the Swedish Navy, the Japanese Navy, the Royal Navy and the US Navy, though not necessarily aboard Aggressive-class minesweepers.

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  A crewman monitors a mine detection and classification sonar console aboard the ocean minesweeper USS Conquest

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  A crewman monitors a mine detection and classification console aboard the ocean minesweeper USS Conquest

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  A paravane used for mine sweeping aboard USS Conquest

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  USS Illusive lowers an acoustical device during an exercise.

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  USS Illusive lowers a different acoustical device for training.

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  USS Illusive deploys a mineweeping cable.

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  USS Constant deploying the "mag-tail", used to simulate the magnetic field of a vessel, are towed behind the ship to trigger magnetic mines.

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  A remote control mine-seeking system, Super Sea Rover, aboard USS Conquest

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  USS Esteem deploys a marker, for marking mines or mine fields.

Units

See also

• HNLMS Onverschrokken (M886) - Dutch Aggressive-class minesweeper

References

External links

• FAS - MSO-422 class
• GlobalSecurity - MSO-422 class
• ex MSO 483