Acoustic - Aircraft laid


♦ Mk52

The first of a postwar series of modular antisubmarine mines, Mk 52 was the 1000-lb-class air-laid weapon. The World War II air-laid mines (such as Mks 25 and 36) used components plugged into the side of the mine; the Mk 50 series used an instrument rack inserted at one end of the mine to carry the firing mechanism, clock mechanism, sterilizer, and associated batteries. The tail cover had 3 openings for target-detecting devices in contact with the sea, and there was a well for the hydrostatic arming device. When it appeared, Mk 52 offered more flexibility in fewer different components in one package than ever before. The mine could be dropped either in cylindrical form with box fins (for internal carriage) or in streamlined form with a round nose and a pointed tail (with pop-out fins). It used new influence field detectors and 3 types of associated firing mechanisms: pressure, acoustic, magnetic. Versions: Mod 0 (pressure), Mod 1 (acoustic, 1130 lb), Mod 2 (magnetic, 1170 lb), Mod 3 (pressure-magnetic, 1190 lb), Mod 4 (pressure-acoustic), Mod 5 (magnetic-acoustic, 1200 lb), and Mod 6 (pressure-acoustic-magnetic, 1235 lb). Mod 7 (magnetic) and Mod 8 (pressure-magnetic) were abortive. In each case, dimensions were 18.8 x 70.2 in, and the charge was 625 lb of HBX-1. Mk 52 could deal with a submarine moving at only 3 kt and could be adjusted in sensitivity. It had a 30-count ship counter and a 1-hr to 90-day delay arming mechanism. It could be used in place of a standard unstreamlined 1000-lb AN-series GP bomb.

As disclosed to the North Vietnamese in 1973 (as part of Operation End Sweep), Mk 52 Mod 2 had a 2-look, reverse polarity, magnetic-induction fuze, with selectable magnetic sensitivities, interlock, dead periods, intership dead periods, ship counts, and preset self-sterilization/self-destruction times.

Mk 52 was part of the U.S. Long-Range Mine Program begun in 1948 and was released for production in January 1954 (operational evaluation began in October 1956). It became operational in 1961. Mod 1 was withdrawn soon after, to be superseded by the other versions, of which Mod 4 was with-drawn from service in 1978. Mk 52 was produced in West Germany and may have been exported to other allied navies. In FY60 each of 2500 Mk 52 mines cost about $4900.

The Actuation Mine Mk 52 is a recoverable, inert-loaded mine. It is normally planted by B-52H Stratofortress, P-3C Orion, or F/A-18A/D Hornet aircraft, but may also be planted minus its flight gear from surface craft. It is planted to help mine countermeasures personnel develop their mine sweeping skills and techniques. If air delivered, it also serves to enhance aircrew proficiency in carrying mines and planting minefields at sea.

The mine weighs approximately 1,000 pounds, consisting of a mine case, instrument rack, tail cover, pyrotechnic (colored smoke) signal and a float inside a drill section, and flight gear (only if air delivered). It does not contain explosives and is ballasted with concrete to maintain its necessary negative buoyancy. The mine does contain magnetic (Mod 2) or acoustic/magnetic (Mod 5) firing mechanisms that, instead of exploding the mine, operate a pyrotechnic signal which surfaces to provide a visual indication of mine actuation. A search coil inside the mine’s case senses magnetic stimuli, while a hydrophone (Mod 5 only) responds to acoustic signals. After a preset time, the float is freed to rise to the water’s surface. This float pays out a 200-foot recovery line that is secured to the mine case, enabling mine recovery by surface craft without the use of divers. The float will operate in this delayed manner whether or not mine actuation (pyrotechnic signal release) has occurred. The mine’s case is
painted either white with orange stripes or orange with white stripes.

Three OAs exist for the Actuation Mine Mk 52. For OA-03B, Fin Mk 10 or 20 is fitted. OA-06B calls for a Fairing, Nose & Tail Mk 19. For both of these air-delivered OAs,
a Parachute Pack Mk 35 is also used. OA-05E is assembled minus any sort of flight gear for surface planting.



Derick S. Hartshorn - 2009-present
Last Modified: