The Mark 14 was the primary U.S. submarine torpedo in WW2 and has gone down as one of the biggest boondoggles in naval history. Designed during the Great Depression to replace the obsolete Mark 10, budget cuts, interdepartmental bickering, and production holdups meant the first live-fire test was conducted in the Philippines when U.S. sub-mariners were sent to sink Japanese ships.

The Mark 14 had a state-of-the-art depth sensor, so it could run at whatever depth the crew set, and the top-secret Mark 6 Exploder, a device that detected the magnetic fields of large metal ships and detonated the torpedo’s warhead when it got within range. With this, the Bureau of Ordnance (BuOrd) was sure they had created the ultimate weapon.

The Philippines engagements told a different story. Torpedoes were exploding too early, or too late. They were smashing into ships and bouncing off, or just sailing under ships without doing anything.

BuOrd issued a statement forbidding anyone from wasting torpedoes by testing them and blaming everything on incompetent crews.

This seemed plausible at the time, as no one had trained with the torpedoes.

However, as the war progressed, reports of torpedo failure became too common to ignore, and eventually the navy decided to run some tests anyway.

The problem was the Mark 14s going too deep, and the tests showed that they levelled out an average of 11 feet below the target depth, sending them safely under the enemies’ keels.

BuOrd was furious that their orders had been disregarded, but the cat was out of the bag, and they were forced to admit that there may be some small flaw in the depth sensor.

The depth sensor was the Mark 14 in miniature, more flaw than machine, but the amazing part is how this went unnoticed.

When BuOrd was calibrating the sensor, they replaced the live warhead with a mock-up. However, they made the mock-up lighter than the warhead so the torpedo would float and could be recovered. 

So the Mark 14 was calibrated perfectly as long as you removed the 300 kg warhead and replaced it with a pool float.

Once the depth sensor was fixed, it was time for the Mark 6 Exploder to prove its worth.

Crews began reporting that their torpedoes were exploding early, simply showering the target in spray.

Magnetic detonators need to account for the earth's magnetic field, and that field is different from place to place. The Mark 6 Exploder worked fine in weaker fields of the testing ground, but where the fighting was happening, getting anywhere near a ship would be enough to trip the sensor.

BuOrd issued another statement about how everything was fine, but the navy had learned a valuable lesson about taking BuOrd seriously and quickly deactivated the Exploders. They would rely on the backup contact detonator. Even BuOrd couldn’t mess that up.

Except...

The navy was flooded with reports of torpedoes smashing into ships and bouncing off without exploding.

BuOrd denied everything again, but they were ignored.

The firing pin in the detonator was perpendicular to the torpedo, so when it hit something, the deceleration would jam the pin against the side of its housing, preventing it from moving. The torpedo had to be redesigned with an ball switch detonator, and by that time it was two years into the war.

The Mark 14 is remarkable not just for its poor design, but for the obstructionist attitude of its designers. 

It is perhaps fitting that the improved Mark 14 torpedo would remain in U.S. service until 1980, outliving BuOrd by 21 years.

If you are interested in the improved version, the declassified manual can be found Here.

Sources

Taliesin Rouleau

Taliesin is a student at Algonquin College. He was raised in the woods by Neo-Pagans and studies Medieval combat from old manuscripts as a hobby.