The Mark 14 Torpedo

From Wonder Weapon to Wartime Scandal

Sep 5, 2008 Paul Crozier

At the beginning of World War II, the Mark 14 steam torpedo was the main weapon of the U.S. Navy's submarine service.

While the Mark 14's overall performance and payload was marginal compared to similar German and Japanese torpedoes, its detonating features were felt to give it a significant advantage. The torpedo possessed two exploders: the Mark 5 which detonated the warhead on contact with the target, and the Mark 6 which was triggered by a steel hull’s magnetic field. Developed by the Bureau of Ordnance, the magnetic exploder feature was thought to be so significant that its existence was a closely guarded secret.

Misses, Duds and Prematures

Immediately following the Pearl Harbor attack, U.S. submarines began offensive war patrols. As captains closed with the enemy expecting to sink their targets, they experienced premature detonations, torpedoes that passed harmlessly underneath ships, and the hollow thud of dud warheads smashing into the sides of hulls.

Staff confidence in the Mark 14 was so high that blame was set on the submariners themselves. They were accused of conducting faulty attacks and improper torpedo maintenance. Skippers were silenced when they made their increasing skepticism about the Mark 14 known.

Running Deep

One commander, Admiral Charles Lockwood, listened to his men. He authorized the test firing of several torpedoes at a fishing net. When the net was raised, holes made by the torpedoes revealed the Mark 14s had run on average ten feet deeper than their designated settings. This flaw enabled the torpedoes to pass beneath targets without triggering the exploder. Orders for corrections were issued to the fleet. But the torpedoes still failed to explode as designed.

Mark 5 Contact Exploder

Despite bureaucratic resistance, Lockwood conducted another field test by firing torpedoes at the cliffs off Kahoolawe, Hawaii. Torpedoes fired at a 90 degree angle to the cliff failed to explode. But as the angle opened, so did the frequency of detonation. By performing an additional series of drop tests they discovered that the firing pin in the contact exploder was too light. Damage on impact rendered it useless. New firing pins were crafted and issued. Yet the torpedoes still detonated prematurely during attacks.

Mark 6 Magnetic Exploder

Many skippers suspected the magnetic exploder to be the culprit. The feature had been investigated and abandoned by other countries prior to the war. But the Bureau of Ordnance insisted it was sound. However, as the submariners investigated the problem it was learned that ships’ magnetic fields flattened to a disk shape near the equator, extending the field away from the hull. This irregularity caused the torpedoes to explode away from the hull when the field was first encountered. Ultimately, the Bureau admitted only two actual tests had been conducted on the exploder prior to certification, only one of which worked. After some heated exchanges, the Mark 6 exploder was ordered deactivated.

Results

By the end of 1943, with depth keeping and firing pin modifications in place and the magnetic feature deactivated, the Mark 14 began to perform. More importantly, the cloud of suspicion and scandal lifted as submarines went to sea with increased confidence in their weapon. However, two years of missed opportunities, and an unknown number of submarines relying on faulty torpedoes to see them through, had been lost in the process.

References:

Christley, Jim. US Submarines 1941-1945, Botley: Osprey Publishing, 2006.

Kimmett, Larry and Regis, Margaret. U.S. Submarines in World War II, Seattle: Navigator Publishing, 1996.

The copyright of the article The Mark 14 Torpedo in Military History is owned by Paul Crozier. Permission to republish The Mark 14 Torpedo in print or online must be granted by the author in writing.

Mark 14 Torpedo