The MK-57 is a 2,000-pound submarine-laid moored mine designed for use against high-speed and deep-water submarines. It contains 360 pounds of HBX-3 and utilizes a total-field magnometer-type magnetic influence firing device. Consisting of a fiberglass case and a cast-steel anchor the Mk 57 is designed for launching from the standard 21-inch torpedo tube. Upon deployment, the mine sinks to the bottom of the water where the case/anchor separation and the mid-freeing sequences take place as in the Mk 56 mine. However, case depth for the Mk 57 is determined by a cable-measuring device in the anchor. When the preset depth has been determined, an electrical signal is sent to an explosive device which locks the cable to prevent further payout. If the mine becomes buried in bottom sediment, a slow-burning propellant in the anchor is ignited, which frees the mine from the bottom. Scuttling features are the same as those of the Mk 56. If the hydrostat fails, or if the mine becomes separated from its mooring cable, the mine will fill with water automatically and neutralize itself to prevent detection and possible hazards to friendly ships.
Variations include the aircraft-laid MK-56.
||LENGTH:||121-1/16 inches||DIAMETER:||21 inches||WEIGHT:||2059 pounds|