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CV60 -> RE: Question on naval mines (12/11/2016 6:29:00 PM)
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From "NAVSEA MINE FAMILIARIZER" (1982) (Unclassified) pg. 5, 10-11
Bottom mines are most effective in comparatively shallow waters....in very deep waters, surface vessels may pass over the mine without actuating its firing mechanisms or, in the event of an actuation, without suffering much damage. Of course a bottom mine planted in deep water is still effective against submarines.
Moored mines are used for deep-water plants and are effective against submarines and surface ships....
Drifting Mines float freely at or near the surface They have no anchoring devices. ...
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METHODS OF ACTUATION
Magnetic Mechanisms. Magnetic firing mechanisms employ either of two types of target detectors: the search coil or the magnetometer....Search coils, as used in standard bottom mines, function to sense changes in one axis of the earth's magnetic field as caused by the presence of a moving ship....search coils are ideal detectors for standard bottom mines since these mines assume an unchanging position on the sea bottom after planting. On the other hand, magnetometers, like search coils, also detect changes in the earth's magnetic fields as caused by the presence of a moving ship; but unlike search coils, magnetometers, as used in moored mines, are three dimensional or total field detectors.....
Acoustic Mechanisms-Using a hydrophone as a detector, acoustic firing mechanism convert underwater sounds from ships into electrical signals...If the acoustical inputs then meet the mechanism's programmed requirements for a valid target ship...the mine [detonates].
Pressure Mechanisms. Pressure detectors are electro-hydraulic sensors which convert negative pressure sensings into electrical signals ...If the analysis shows that the strength and duration of a given signal meets the programmed requirements for a valid target ship,... [the mine detonates]. In performing this function, the pressure detector senses a decrease in pressure caused by a moving ship as it displaces a given volume of water beneath its hull...It should be noted that ocean swells and surface waves may also be sensed and processed by the pressure detector. However, since the magnitude of the signals produced by these disturbances is small, the firing mechanism [ignores them]. Also worth of note is the fact that pressure firing mechanisms are not used alone, but rather in various combinations with magnetic and acoustic firing mechanisms. This provides a diversified mix that not only increases the mine's detection capability, but also makes countermining more difficult...
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