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Mark 14: The Torpedo That Couldn’t


During the Industrial Revolution, many fields underwent incredibly disruptive evolutions in incredibly short periods of time. One of those fields was that of naval engineering; for the longest time, ships had been made of wood, and cannons had been simple cast iron shells. But with industrialization, both of these changed; ships dropped their wooden hulls in favor of iron ones, and since cannon shots ceased being effective against armored ships, new explosive shells were designed to compensate.

Yet, as with all arms races, this was not enough, and soon a new weapon was designed to gain an edge over rivals: the torpedo, a self-propelled explosive that would explode underneath the water and sink a ship from below. Though torpedoes today are among some of the most advanced weapons available to a modern military, it took some time to get there, as well as many, many failures. Today, we have for you one of those failures. This is the story of the Mark 14 Torpedo, probably the worst torpedo in history.

War on the Waters

The first “modern” torpedo was invented in 1866 by two men – Giovanni Luppis, an Austro-Hungarian naval officer, and Robert Whitehead, an English engineer. Luppis was the “ideas guy” in this relationship, while Whitehead designed the actual torpedo. Before that point, the term “torpedo” was typically used to refer to anything from naval mines to so-called “spar torpedoes”, i.e. bombs on the end of sticks like those harpoons on the cars from Mad Max: Fury Road.

But with Whitehead’s invention, this new weapon proliferated far and wide. France and Germany had their own versions of Whitehead’s torpedo soon after he built it, and by 1900, “torpedo” exclusively meant a self-propelled underwater explosive weapon. Whitehead himself continuously improved on his design for the rest of his life, and by 1890 he had made torpedoes capable of traveling up to 30 knots (56 km/hr). He also built a torpedo factory in Portland Harbour, England, which continued in operation until the end of World War II. And what a segue that is.

World War II was quite different from World War I in terms of naval warfare. In the latter, there had been one serious naval engagement in the entire four years of the war; this time, the war on the sea became a critical theater of the conflict. German U-boats were raiding commerce shipping in the Atlantic, and the Imperial Japanese Navy, at the time the third-largest navy on the planet, would ply the waters of the Pacific. Which takes us to America.

In 1931, the US Navy allocated funding for designing a new torpedo. This weapon was going to be a bold step into the future – incompatible with older submarines and torpedo boats, and exclusively to be used by the new “fleet” submarines. They called it the Mark 14. It was 20 feet and 6 inches long, 21 inches in diameter, and weighed over 3,000 lbs. It had a maximum speed of 46 knots (85 km/hr), a maximum range of 9,000 yards, and a 643-pound warhead of Torpex, a type of powerful explosive.

The Mark 14 was to be a replacement for the Mark 10, the former standard torpedo for the US Navy. Of course, to be a replacement, it has to be better than the thing it’s replacing. Strictly speaking, that was true – torpedoes are made up of subsystems, and on paper, the Mark 14’s were much improved from the Mark 10’s. We described all of the standard design specifics already, but the Mark 14 had one new technology that set it apart: a magnetic influence exploder. Put simply, this ingenious little piece of tech was designed to detect the difference in the Earth’s magnetic field when it passed underneath a ship, and would blow the torpedo when it did so. This was a game changer, since an explosion under the keel of a ship would often sink it immediately. This meant that the torpedo didn’t need a huge warhead to sink a huge ship.

But we’re saying all of these nice things to get to the main part of our story, which is where we stop being so nice. And, not coincidentally, where the Mark 14 stops working.

Contact Failure

The problems with the Mark 14 began before it was even adopted into the Navy. Testing of the weapon, as well as the fancy magnetic detonator, were carried out through the 1930s, although interestingly enough the Navy never signed off on live-fire drills with the torpedoes. That might seem odd, since one would expect that there would be interest in making sure the torpedoes actually worked, but the Navy declined.

Why? Well, America was in the middle of the Great Depression and money was tight. Mark 14’s were costing around $10,000 each, or around $170,000 in today’s money, and an exploded torpedo obviously can’t be used again. That was money that the Navy wasn’t keen on spending, to the point that while discussing torpedo drills with the USS Ericsson as a practice ship, the Navy insisted on someone else paying to refloat it should it accidentally be sunk. The best part? The USS Ericsson was due to be scrapped, whether it was sunk or not. The Navy literally didn’t want to pay for a second target.

Completely out of character frugality from the US military aside, the tests showed that the magnetic detonator, at least, worked as intended. Or so they thought, as you’ll see. With the lack of live-fire drills, there were significant issues in the design which would become glaringly apparent after the Japanese attack on Pearl Harbor. But we’re not done with ancillary problems, yet.

Following America’s entry into World War II, America struggled to even build enough torpedoes to supply their submarines. This had been a problem during World War I as well, and America hadn’t learned from it. The thing about torpedoes was that scaling them up for mass production was more challenging than, say, tanks or aircraft. In 1937, the primary torpedo construction facility in America was producing torpedoes at the blistering pace of one and a half torpedoes per day. That had improved to 23 per day by the time Pearl harbor happened, but it was still nowhere near the quantity required by the Navy. Even so, with the war begun, America was ready to show the world this great new weapon. Specifically, show the world how little America had bothered to test it.

The Mark 14 had three major problems. Firstly, the torpedo had the tendency to run about 10 feet, or 3 meters, deeper than what it was set to. You can understand how this would cause problems for aiming the thing, and indeed, there were many cases where the torpedo ended up underneath a ship that it otherwise might have hit. That might be considered a good thing, because of that fancy magnetic detonator that would detect the ship above it, right?

Well, no, because the detonator was the second major problem. The magnetic exploder was a finicky, difficult little piece of engineering that often either detonated the warhead prematurely, or failed to detonate the torpedo at all. So, when the torpedo was fired and it passed under the target ship, it sometimes sailed harmlessly past it, with the enemy ship none the wiser to the fact that a submarine was shooting at them.

But even accounting for both of these issues, the third problem rather overshadowed them both, and that had to do with the contact detonator. See, this is a highly technical problem, so try to bear with us: when a torpedo hits a target, it’s supposed to explode. Hard to follow, we know. But the Mark 14 couldn’t even do that, again down to the lack of testing. Many times crews would score direct hits, only for it to clang off the hull and do nothing.

These problems, glaring as they were, were not unfixable. The thing is, they tended to hide each other. When it became clear that the torpedoes were failing to explode as they passed under the ships, some submariners disabled the magnetic detonator, believing it was faulty, and went for old-fashioned contact hits instead. When those failed, everyone was left confused as to what the actual cause of the problem was, since torpedoes, as stated before, were complicated.

All this is to say that the torpedo was so damn broken, that no one was entirely sure how to fix it. And so, the improvements had to come slowly, over time.

Marginal Improvements

Mark 14 Steam Driven Torpedo by Wally Gobetz is licensed under CC-BY-NC-ND

The easiest problem to fix was the depth. A test was carried out that conclusively proved the Mark 14 ran ten feet deeper than it was set to. This was primarily due to weight differences between the tested torpedoes and the live weapon torpedoes, and was fixed by tweaking the depth and pressure sensors to be more accurate.

But still, torpedoes weren’t scoring any sinkings. Instead, they were blowing up far too early, due to the magnetic detonator. It turned out that the depth problem was related to this; as the torpedoes were deeper in the water, they wouldn’t be detecting the ships above them as they passed underneath. Since they were now traveling higher up, this overcompensated for the detonator, and the torpedoes were hitting the detonation threshold some fifty meters before reaching the enemy ships.

The detonator was messing up, again, for a number of reasons. Sometimes the depth wouldn’t be stable when the torpedo armed, and the magnetic field would shift and cause a detonation. Other times, the torpedo wouldn’t be aimed under the ship, but at the side of it, and this would cause it to explode before it had actually reached the ship.

The designers went back and looked at the detonators, too, but at this point submarine crews were getting understandably sick of this torpedo. The last straw for many of them was in June of 1943, when a group of American submarines managed to infiltrate Tokyo Harbor undetected. Instead of scoring easy hits on ships sitting in port and getting some payback for Pearl Harbor, every single Mark 14 torpedo failed and the squadron had to humiliatingly leave empty-handed. The navy finally recommended that submarine crews disable the magnetic detonator, which submarine crews had already been unofficially doing.

Whatever the case, the detonator was disabled in most cases, and crews were instructed to go for contact hits instead. That stopped the problem of premature detonations, replacing it with the problem of no detonations. As it turned out, the firing pin of the torpedo was defective, too. Ironically, a solid 90-degree angle hit was more likely to be a dud, and sometimes the torpedoes would even lodge into the hulls of Japanese ships without detonating.

What was wrong this time? It had to do with speed. The Mark 14 actually had two speeds, 31 knots and 46 knots. Most of the limited tests during the 30s were done at 31 knots, where the detonator mostly worked fine; however, it often failed at 46 knots, and so a torpedo could score a direct hit on a ship, but if it was going 46 knots, it would just not work. To solve the problem, crews were advised to fire their torpedoes at oblique angles until they could replace the firing pin system with something more reliable.

Finally, with that fix, the torpedo seemed to work alright, and it only took two years. Sinkings rose noticeably, and at the same time, the US Navy started inflicting more and more defeats on the Imperial Japanese Navy, until Japan’s eventual defeat. But there’s one more thing we’d be remiss about not including. Allegedly, the Mark 14 had a tendency to run in circles due to problems with the internal gyro-system. So, a submarine would shoot the torpedo at a ship, and then the torpedo would circle back around, and hit the submarine that fired it. Again, there’s no definitive proof that ever happened, but honestly, at this point, something as spiteful as that wouldn’t be that out of the ordinary.

Progress Through Time

Following the end of the war, the Mark 14 was very quickly replaced by the Mark 16, an updated version of the design. This one, at least, took in most of the lessons learned from the previous design, such as “actually test your weapon before a war starts.” Today, the US Navy utilizes the Mark 48, which is basically a computer with a bomb strapped to the front of it. And it seems that improvement does come, eventually; the Mark 48 was so well-designed that it’s been in service in some form or another since 1972, and there are no signs of it being retired anytime soon. But when you think of the frankly scary capabilities of the Mark 48, spare a thought for its troubled cousin and the headaches it caused submariners across the seas, all those years before.

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