Deperming
Encyclopedia
Degaussing
Degaussing is the process of decreasing or eliminating an unwanted magnetic field. It is named after Carl Friedrich Gauss, an early researcher in the field of magnetism...
, is a procedure for erasing the permanent magnetism
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
from ships and submarines to camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
them against magnetic detection vessels and enemy marine mines.
A sea-going metal-hulled ship or submarine, by its very nature, develops a magnetic signature as it travels due to a magneto-mechanical interaction with the Earth's magnetic field. This signature can be exploited by magnetic mines, or facilitate the detection of a submarine by ships or aircraft with magnetic anomaly detection (MAD)
Magnetic anomaly detector
A magnetic anomaly detector is an instrument used to detect minute variations in the Earth's magnetic field. The term refers specifically to magnetometers used by military forces to detect submarines ; the military MAD gear is a descendent of geomagnetic survey instruments used to search for...
equipment. Navies
Navy
A navy is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake- or ocean-borne combat operations and related functions...
use the deperming procedure, in conjunction with degaussing
Degaussing
Degaussing is the process of decreasing or eliminating an unwanted magnetic field. It is named after Carl Friedrich Gauss, an early researcher in the field of magnetism...
, as a countermeasure against this.
Specialized deperming facilities, such as the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
's Lambert's Point Deperming Station
Lambert's Point Deperming Station
Lambert's Point Deperming Station is a United States Navy deperming facility located in the Elizabeth River just off Lambert's Point, Norfolk, Virginia, United States. It was built in the mid 1940's and services the U.S. Atlantic Fleet....
are used to perform the procedure. Heavy gauge copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
cables are wrapped around the hull and superstructure of the vessel, and very high electrical currents (as high as 4000 amps) are pulsed through the cables. This has the effect of "resetting" the ship's magnetic signature. It is also possible to assign a specific signature that is best suited to the particular area of the world in which the ship will operate. Over time the deperm will begin to degrade and the procedure must be redone periodically to maintain the desired effect.
During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
commissioned a specialized class of degaussing ships that were capable of performing this function. One of them, USS Deperm (ADG-10)
USS Deperm (ADG-10)
USS Deperm was a degaussing vessel of the United States Navy, named after the term deperm, a procedure for erasing the permanent magnetism from ships and submarines to camouflage them against magnetic detection vessels and enemy marine mines. Originally planned as a patrol craft escort ', she was...
, was named after the procedure.