steve@ncsc.navy.mil (Mahan) (11/24/89)
From: steve@ncsc.navy.mil (Mahan)
Some current mines use magnetic detectors to pick up the magnetic fields
of passing ships. Some of the mines use this as an explosive trigger,
some only to initiate the next step in the sequence (torpedo launch, rise
to preset depth, etc.. ).
The older minesweepers and the new Avenger (MCM-1) class are constructed
with great attention given to minimizing magnetic signature. The hulls are
wood, there are strict limits on the sizes of metallic objects, and magnetic
objects must be shielded. The degaussing system on board includes separate
loops for the engine and other large metallic masses as well as 3-d loops
for the ship as a whole. The controller for the system is tied to the ships
navigation system and currents are varied according to the ships position
and heading in the geomagnetic field.
One sweeping technique is to drag a cable and pass large currents through
the water astern of the ship to create a magnetic field in the water. This is
combined with noisemakers and cable cutters as the mission requires.
Stephen Mahan
Naval Coastal Systems Center (formerly Mine Defense Laboratory)
Panama City, FL 32408-5000
ARPA: steve@ncsc.navy.mil