#torpedoes

1,198 lives were lost

Failure to test is.. testing to fail. Or something like that. Insert whatever butchered saying you want, but new stuff, especially anything complicated, really needs to be tested in real-world conditions. You know what would definitely fall into that category? A brand-new design of torpedo.

I wrote earlier about ship defenses against mines and torpedoes. In the era of WWII, torpedoes and mines would detect the magnetic signature of a ship to know when to explode. This was essential, in fact, because a contact torpedo would simply hit the side armor of a ship. A magnetic field detector would get the thing underneath the ship instead.

Needless to say, the mechanism for this being in a torpedo was very complicated and expensive.

The torpedo in question here is called the Mark 14, although these problems also affected other designs. The design process started in the 1920s. Key to the Mark 14 was a magnetic detector, dubbed the Mark 6 exploder. This technology was brand-new to the US. In fact, it was created by disassembling German mines collected from World War I.

The Mark 6 was top-secret, particularly because of its inspiration. If an enemy nation figured out exactly how an American torpedo detects ships, it'd become easier to make countermeasures. As that earlier post with degaussing showed, counter they did once they had it figured out.

Actual testing took place during the 1930s, a period marked by decreased spending on basically anything. And testing real torpedoes that cost $10,000 ($220k today) apiece? Nah. We'll use a floating dummy torpedo instead. The test torpedo had a buoyant front so it'd be retrievable after testing.

They also couldn't use one to sink a real ship: Nobody was willing to pay to refloat and repair the target. So instead it just had a camera that'd trigger when it was appropriately beneath the target.

As you might imagine, the dummy torpedo did not really match the performance of a real one. It weighed less, it floated, the depth setting was all wrong. But with zero live testing, the Mark 14 started production. Very slowly, at 3 built per day, the Navy got its Mark 14 torpedoes ready for the day war would come.

When war did come, the torpedoes were still not being produced fast enough! There was an immediate torpedo shortage. Speeding up production lead to quality issues, and still nobody could afford to actually test them.

Naval officers quickly found out about the shortcomings of the Mark 14. In December 1941, Commander Tyrell Jacobs fired eight torpedoes, with not a single one working. He fired two more torpedoes. Still nothing. He used yet another aimed absolutely perfectly and missed. This experience was repeated all across the Navy.

How many $10,000 production torpedoes got used like this because not a single one could be spared for testing?

Out of 800 torpedoes used in 1942, 80% failed to work! But the Bureau of Ordnance refused to believe the Mark 14 had a problem, because that would be an expensive fix. It took until August 1942 to acknowledge a problem.

The problem was exactly what you'd think. The calibration for depth was right for the light dummy warhead, but not for a real torpedo. In action, the Mark 14 would be 10 feet deeper, causing it to sail right past a target.

Advisements to user a lower (higher?) depth setting didn't entirely fix the problem. The Mark 6 exploder was still failing. The Bureau of Ordnance had still not actually tested any of their suggestions! There was yet another problem in that the Mark 6 exploder didn't work at the distance and depth needed for the Mark 14 torpedo.

Now, how could someone know this? The Mark 6 had a manual written. Of course, since it was top-secret technology, said manual was also classified and not printed instead of distributed to the people aiming the torpedoes.

The Bureau of Ordnance continued sticking its fingers in its ears, singing "I can't hear you", so Navy command instructed commanders to just disable the fancy magnetic exploder entirely and rely on contact detonation. And presto, the Mark 14 was effective again!

"Gyroscopes allowed for torpedoes to be launched sideways off a vessel in nearly any direction at or below 90° to target. This meant that the only real requirement for a firing solution was determining where the torpedo would meet the path of the target. This, as in gunfire, requires deflection. To determine deflection, tubes were initially equipped with rudimentary director equipment mounted on the launchers like a gunsight. An operator would use a series of interlocking slide rules, very similar to a course solver (or Dumaresq) in gunnery, to set the sights. The primary inputs required for this "torpedo triangle" were line of sight to target, target course, and torpedo course. The "Deflection Triangle" replaced it during WWI, using line of sight, torpedo path, and perpendicular line across line of sight to link the two.

Once target data was known, typically acquired optically, torpedo speed had to be chosen; torpedoes had multiple speed settings. Faster speed meant less range, while slower speeds time to evade. Speed determined run time, the final measurement required to create a firing solution. The output was gyroscope angle, which dictated the torpedo course; this was applied by turning a lever or spindle protruding from the launcher. However, the run time required for the gyro to stabilize led to a "reach" period - which did not follow the trigonometry of the original firing solution, and made gyroscopic torpedoes unpopular at first.

Tube-mounted directors were local affairs, subject to the judgement of operators and reliant on verbal communications from the bridge. This was insufficient for complex tactical scenarios, so bridge-mounted directors were developed in the wake of WWI. These devices were essentially bearing transmitters combined with a computer on a pedestal with a telescopic sight, to be covered in the next post.

Here, the operator of a torpedo tube aboard an early British destroyer fires a torpedo using a triangle director and sight."