Aggressive-class minesweeper

USS Constant (MSO-427)
Class overview
Operators:	United States Navy  Republic of China Navy  Belgian Navy  Royal Norwegian Navy  Philippine Navy
In commission:	1953–1994
Completed:	53
General characteristics
Displacement:	853 tons (full load)
Length:	172 ft (52 m)
Beam:	35 ft (11 m)
Draft:	10 ft (3.0 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)
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 floating 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 of the ship is made of wood.

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 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 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 (MSO-488)

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  A crewman monitors a mine detection and classification console aboard the ocean minesweeper USS Conquest (MSO 488).

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  A paravane used for mine sweeping aboard USS Conquest (MSO-488)

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  USS Illusive (MSO-448) lowers an acoustical device during an exercise.

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  USS Illusive (MSO-448) lowers an different acoustical device for training.

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  USS Illusive (MSO-448) deploys a mineweeping cable.

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  USS Constant (MSO-427) deploying the "mag-tail", used to simulate the magnetic pull of a vessel, are towed behind the ship to attract magnetic mines.

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  A remote control mine-seeking system, Super Sea Rover, aboard USS Conquest (MSO-488).

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  USS Esteem (MSO-438) deploys a marker, for marking mines or mine fields.

Units

Ship Name	Hull No.	Builder	Commission– Decommission	Fate	Link
Aggressive	422	Luders Marine Construction Co. of Stamford, Connecticut	1953–1971	Sold for scrap 1980
Avenge	423	Luders Marine Construction Co. of Stamford, Connecticut	1954-1970	Destroyed by fire, sold for scrapping 1969
Bold	424	Norfolk Naval Shipyard	1953-1971	Sold for scrap 1981
Bulwark	425	Norfolk Naval Shipyard	1953-1971	Sold for scrap 1980
Conflict	426	Fulton Shipyard, Antioch, California	1954-1973	Sold for scrap 1973
Constant	427	Fulton Shipyard, Antioch, California	1954-1992	Sold for scrap 2001
428 - 431 were US Dash class minesweepers
Dynamic	432	Colberg Boat Works, Stockton, California	1953-1971	Sold or loaned to Spain as Guadalete M41, 1971.
Engage	433	Colberg Boat Works, Stockton, California	1953-1991	Scrapped 2002
Embattle	434	Colberg Boat Works, Stockton, California	1954-1972	Sold to be scrapped 1976, privately held until scrapped by USACE in 1993.
Endurance	435	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1954-1972	Sold for scrap 1973
Energy	436	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1954-1972	Loaned to Philippines 1972 Sold for scrap 1977
Enhance	437	Martinolich Shipbuilding Co., San Diego, California	1955-1970 1971-1991	Sold for scrap 2000
Esteem	438	Martinolich Shipbuilding Co., San Diego, California	1955-1970 1971-1991	Sold for scrap 2000
Excel	439	Higgins Corp., New Orleans, Louisiana	1955-1992	Sold for scrap 2000
Exploit	440	Higgins Corp., New Orleans, Louisiana	1954-1993	Sold for scrap 2002
Exultant	441	Higgins Corp., New Orleans, Louisiana	1954-1993	Sold for scrap 2002
Fearless	442	Higgins Corp., New Orleans, Louisiana	1954-1990	Sold for scrap 1992
Fidelity	443	Higgins Corp., New Orleans, Louisiana	1955-1989	Sold for scrap 1990
Firm	444	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1954-1972	Loaned to Philippines 1972 Scrapped 1977
Force	445	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1973	Sunk after a fire
Fortify	446	Seattle Shipbuilding and Drydocking Co., Seattle, Washington	1954-1992	Scrapped 2002
Guide	447	Seattle Shipbuilding and Drydocking Co., Seattle, Washington	1955-1972	Sold for scrap 1973
Illusive	448	Martinolich Shipbuilding Co., San Diego, California	1953-1990	Sold for scrap 1993
Impervious	449	Martinolich Shipbuilding Co., San Diego, California	1954-1991	Scrapped 2002
450 - 454 built at Bellingham Shipyards Co., Bellingham, Washington for France, not necessarily Aggressive class ships.
Implicit	455	Wilmington Boat Works Inc., Wilmington, California	1954-1994	Sold to Taiwan 1994
Inflict	456	Wilmington Boat Works Inc., Wilmington, California	1954-1990	Sold for scrap 1992
Loyalty	457	Wilmington Boat Works Inc., Wilmington, California	1954-1972	Sold for scrap 1973
Lucid	458	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1976 Currently being restored by the Stockton Historical Maritime Museum as a museum ship
Nimble	459	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1981
Notable	460	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1971
Observer	461	Higgins Corp., New Orleans, Louisiana	1955-1972	Sold for scrap 1979
Pinnacle	462	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1978
Pivot	463	Wilmington Boat Works Inc., Wilmington, California	1954-1971	Initially loaned then sold to Spain as Guadalmedina M42, 1974
Pluck	464	Wilmington Boat Works Inc., Wilmington, California	1954-1990	Sold for scrap 1992
Prestige	465	Wilmington Boat Works Inc., Wilmington, California	1954-1958	Grounded and sunk, 1958 in the Naruto Strait
Prime	466	Wilmington Boat Works Inc., Wilmington, California	1954-1970	Sold for scrap 1976
Reaper	467	Wilmington Boat Works Inc., Wilmington, California	1954-1972	Sold for scrap 1976
Rival	468	Luders Marine Construction Co. of Stamford, Connecticut	1954-1970	Sold for scrap 1971
Sagacity	469	Luders Marine Construction Co. of Stamford, Connecticut	1955-1970	Grounded at Charleston Harbor then sold for scrap 1970.
Salute	470	Luders Marine Construction Co. of Stamford, Connecticut	1955-1970	Sold for scrap 1971
Skill	471	Luders Marine Construction Co. of Stamford, Connecticut	1950-1970	Sold for scrap 1979, scrapped 1983.
Valor	472	Burger Boat Company, Manitowoc, Wisconsin	1954-1970	Sold for scrap 1971
Vigor	473	Burger Boat Company, Manitowoc, Wisconsin	1954-1972	Sold to Spain as Guadiana M44, 1972. Scrapped by Spain after 1999.
Vital	474	Burger Boat Company, Manitowoc, Wisconsin	1955-1972	Sold for scrap 1979
475 - 487 built for France, Portugal, Spain, Belgium and the Netherlands, not necessarily Aggressive class ships.
Conquest	488	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1970 1971-1994	Sold to Taiwan 1994
Gallant	489	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1994	Sold to Taiwan 1994
Leader	490	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1970 1971-1991/92	Sold for scrap 1994
Persistent	491	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1956-1971	Initially loaned in 1971 then sold to Spain as Guadalquivir M43
Pledge	492	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1956-1994	Sold to Taiwan 1994
Stalwart	493	Broward Marine Inc, Fort Lauderdale, Florida	1956-1966	Caught fire pier side at San Juan, Puerto Rico, sunk 1966. Later raised and sunk as an artificial reef.
Sturdy	494	Broward Marine Inc, Fort Lauderdale, Florida	1957-1971	Sold for scrap 1978
Swerve	495	Broward Marine Inc, Fort Lauderdale, Florida	1957-1971	Sold for scrap 1978
Venture	496	Broward Marine Inc, Fort Lauderdale, Florida	1958-1971	Sold for scrap 1978
MSO-497	497	Cancelled, never built

References

External links

• FAS - MSO-422 class
• GlobalSecurity - MSO-422 class