Mark 14, U.S. Torpedo

Naval History and Heritage Command #NH 94117

Specifications:

The Mark 14 torpedo was the standard weapon on the more modern U.S. submarines by 1941. It had a sophisticated magnetic detonator that was supposed to set the weapon off directly under the keel of a ship, where it would break the ship's back. However, frugal budgets and an obsession with secrecy meant that it was live-tested exactly twice before being issued to the fleet, in 1926. One of the tests failed, which ought to have raised a red flag, but the Navy was reluctant to fund further live-firing tests. It took the Navy an astonishing two years from the start of hostilities in the Pacific to officially recognize that the weapon ran ten feet too deep, that the magnetic detonator was almost useless anywhere but the North Atlantic (and probably there as well), and that the contact detonator usually failed on normal impacts. In one notorious incident, a U.S. submarine commander crippled a large freighter with a spread of two torpedoes, then carefully squared off his boat and fired no less that thirteen additional torpedoes at a theoretically perfect angle of impact at the theoretically perfect range. Not one detonated. The problems with the Mark 14 were largely resolved by 1944, and U.S. submarines began to take a crippling toll of Japanese warships and merchantmen; but the Mark 14 never became a wonderful torpedo.

One reason why the magnetic detonators were retained for so long was that the Mark 14 had a relatively small warhead, little over half the weight of the Long Lance warhead. This was inadequate against the armor belts of capital ships, and could not even guarantee the sinking of a large merchantman. It was felt that the torpedo had to explode under the keel of the target to ensure destruction.

The 31 knot speed setting was rarely used during the war.

References

Campbell (1985)

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