Degaussing is a procedure developed during WW II, which allows to neutralize a ship's own magnetic signature
in order to protect it against magnetic mines. The term "making a ship invisible" very likely was meant as "making
a ship invisible to magnetic mines".
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Principles of Magnetism and Stray Currents
A steel-hulled ship is like a huge floating magnet with a large magnetic field surrounding it
Degaussing aims at reducing a ship's magnetic signature and is carried out by a network of current-carrying cables arranged
through the inner hull of a vessel. These operate like little panel beaters whose job is to smooth out magnetic bumps.
However this signature is not constant and the magnetic "dent" changes its shape at varying latitudes.
What is degaussing?
Degaussing makes a ship invisible to magnetic mines:
The magnetic mine was the most dangerous and
destructive type. All steel ships have magnetism built into
them. When a steel vessel passes over a magnetic mine,
the magnetic forces in the ship trigger a mechanism in the
mine that sets off an explosion under the hull. To
counteract these mines, some ships were degaussed.
DEGAUSSING SYSTEMS (DEGS)
Degaussing of Ships & Submarines
USN DEGAUSSING SHIPS
The Philadelphia Experiment
"Degaussing is a process in which a system of electrical cables are installed around the
circumference of ship's hull, running from bow to stern on both sides. A measured
electrical current is passed through these cables to cancel out the ship's magnetic field.
And that's roughly how "degaussing" came about:
derived from a brilliant German mathematician, Karl Friedrich
Gauss (1777-1855), who had achieved the honor of having his
name, Gauss, denote a unit of intensity of a magnetic field.
FEN has been involved in the area of naval magnetism from the very beginning, having designed and manufactured degaussing systems for steel surface vessels
and low magnetic signature MCM vessels for the Italian Navy among others.
During 50 years of experience in this field, IFEN has designed, manufactured, tested, installed and calibrated degaussing systems for over 150 ships.