Moored-contact

Between the early 1890s and prior to World War I, contact mines were used primarily as defensive or blockade weapons and sometimes were employed as floating (drifting) weapons. Mines were ideally suited for harbor defense and while still in the development stage, offensive applications had yet to be developed..


U.S. Naval Historical Center Photograph # NH 101471
These may be Naval Blockade Mines (No Mark Number) on an unidentified US warship about 1909.
 Caption reads "Mines Ready for Drill" Designation assigned 1905. Spherical moored mine 43 inches (109 cm) in diameter. Used an inertial exploder of the pendulum type. Total weight 1,265 lbs. (574 kg) with a charge of 250 lbs. (113 kg) of wet gun cotton.
 

Between the early 1890s and World War I, moored contact mines were designed as defensive weapons, ideally suited for harbor defense. Among these were the Mk 2 and Mk 3.

The "K-pistol," a pre-World War I development, used on the Mark 6 moored contact mine, used a copper antenna which extended upwards to just below the surface. This was connected by a relay to a copper plate on the outside of the mine. Seawater acted as the electrolyte of a battery which would be formed when a ship with a steel hull approached and touched the antenna. The current running down the antenna operated the relay and exploded the mine. This method allowed each mine to cover a wider area, meaning that fewer mines could be used to cover a given area than with the horn type. In modern terms, the "K" device exploited the Underwater Electric Potential (UEP) effect.

The "K-pistol" of the Mark 6 used a copper antenna which extended upwards to just below the surface. This was connected by a relay to a copper plate on the outside of the mine. Seawater acted as the electrolyte of a battery which would be formed when a ship with a steel hull approached and touched the antenna. The current running down the antenna operated the relay and exploded the mine. This method allowed each mine to cover a wider area, meaning that fewer mines could be used to cover a given area than with the horn type. In modern terms, the "K" device exploited the Underwater Electric Potential (UEP) effect.

The antenna, an extension of the hertz horn, made the Mk 6 an ideal weapon for intercepting submarines , regardless of the depth in which they operated. The Mk 6 and its variations were instrumental in thwarting the U-boat menace and by late 1917, kept the German submarine fleet effectively bottled up in the Baltic Sea, allowing re-supply of the British Isles.

 

This antenna mine was developed during World War I for the North Sea antisubmarine barrage and subsequently became the main U.S. surface-laid contact weapon.


North Sea mine laying operation

♦ Mk 6

Mk 6 was used during World War II and was probably distributed to U.S. allies post-war. It was a 34-in sphere containing 300 lb of TNT (1400 lb total, including sinker) and could be moored in up to 3000 ft of water. Mod 3 had a 100-ft lower antenna, and Mod 4 a 50-ft lower antenna. Versions differ in type of sinker. All of these mines have Hertz horns in addition to their antennas (Mods 14 and 15, approved for service use in 1955 and 1964, respectively, were limited to contact operation). All versions of Mk 6 were withdrawn from U.S. service in 1970.

 

♦ Mk 16


Photo by Don DeCrona
Mk 16 mines in Mine Assembly Bldg. 104-6, Hawthorne NAD.

Mk 16 is a contact (Hertz horn) mine, ovoid in shape (Mk 6 is spherical). Mk 16 carries 600 lb of HBX-1, total weight being 2040 lb. Exported postwar, Mk 16 was originally conceived as a successor to the Mk 6 antenna mine. Mod 0 was a moored induction mine. Mod 1 was a contact mine similar in operation to Mk 6. Mod 2 was a moored acoustic mine.


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