Not Our Problem

Seventy yeears ago this morning, Commander Lawrence Daspit and his submarine, the USS Tinosa, were stalking their prey.

Their target, the 19,000 ton tanker Tonan Maru Number 3, was one of the largest tankers in the Japanese merchant fleet.  

And despite the fact that the war was a year and a half old by this point, Tonan Maru was not only proceeding at 13 knots (about 16 mph) without air or surface escorts, but wasn’t even zig-zagging. 

It was the naval equivalent of having a twelve point buck walk into your bar, order and chug down six Jägermeister shots, and insult your sister at the height of deer season. 

Daspit maneuvered his submarine directly perpendicular to the tanker’s course, so the torpedoes would impact the target squarely, just as the textbooks said.  He fired four Mark XIV torpedoes.  It was a textbook shot; short range, perfect visibility through the periscope, perfect angle on the target.

The torpedos all ran straight – but Daspit only saw two small gouts of water spout up alongside the ship.  Two torpedoes had apparently missed, and the other two misfired; the spouts may have been exploding compressed air flasks aboard the torpedoes.

Tonan Maru turned sharply away from the attack, and started accelerating – which was a slow process with a relatively big ship that wasn’t built for speed.  Daspit fired the remaining two torpedoes from his forward tubes – Tinosa had six facing forward and four more aft.  The angle was not ideal; Tonan Maru was making 13-14 knots, and Tinosa could only move at 8-9 knots underwater, so the torpedoes intersected the tanker’s course at a fairly sharp angle. 

But Daspit’s marksmanship was impeccable – and this was many years before guided torpedoes became common, and the Mark XIV was a straight-running torpedo.  Both torpedoes hit the Tonan Maru, exploding near the tanker’s stern.  Tonan Maru coasted to a stop. 

Daspit maneuvered Tinosa to a point 875 hards to the stopped tanker’s flank.  He lined up another shot.  The torpedo ran straight and true into the tanker’s side…

…and yielded another splash of water from the explosion of the compressed-air tanks.  For the fifth time in seven “fish”, the warhead had failed. 

Frustrated – and, so far, unmolested by Japanese anti-submarine warfare (ASW) forces, Daspit ordered his torpedomen to painstakingly inspect each Mark XIV torpedo before loading and firing it.  The torpedomen inspected each “fish”, pronounced them in perfect condition (as well they should; maintaining the torpedoes was what they did, all patrol, every patrol, like a Formula One racing crew doting over their cars). The torpedo room then loaded them into the torpedo tubes, spun them up, and fired them, one at a time, directly into the flank of Tonan Maru.

Nine more times. 

None of them exploded.  Daspit’s log noted each firing with the precision of an engineering experiment log – and tartly chronicled the failure of each successive Mark XIV.  Daspit planned to save his final torpedo – a plan that was punctuated when he saw a Japanese destroyer approaching through is periscope.  Tinosa sailed back to Pearl Harbor. 

Daspit barged into the office of Admiral Charles Lockwood, commander of US submarines in the Pacific, with a string of obscenities.  Lockwood understood.

Part of it was that 19,000 ton tankers were a frustrating target to lose. 

More than that?  It wasn’t a new problem. 

———-

It’d been over a year and a half since Pearl Harbor.  With its battle fleet sunk, and four aircraft carriers lost in the previous 18 months (Lexington at Coral Sea; Yorktown at Midway; Wasp and Hornet in the furious fighting in the Solomon Islands), the battle was largely the Submarine Service’s to fight.

And fight they did.  In the first days of the war, US submarines started pressing home attacks against Japanese ships all over the Pacific.

And a curious pattern emerged:  skippers of the “S-Class” submarines – built during World War I, and recommissioned from the reserve as war approached – were getting kills. 

They were old, and much slower than the newer “Fleet boats” that were the vast bulk of the fleet, and they had a tougher time getting into a firing position.  And they were designed for war in the much-smaller Atlantic, so they only rarely had the range to engage Japanese ships…

…but when they got a shot, the torpedoes – World War I-vintage Mark X “fish” – exploded.  Ships were sunk.

In the meantime, although the newer submarines were pressing home attacks aggressively, there was a distinct lack of results. 

The Navy was non-plussed.  Explanations ranged from the inexperience of the torpedo room crews to poor marksmanship to, occasionally, cowardice; at least a few sub commanders were releived of duty.

But as the war patrols ground on, and the same patterns kept reiterating themselves, Commander of Submarines/Pacific (COMSUBPAC) Admiral Lockwood started thinking the problem was the torpedoes themselves.  The Mark XIV torpedo had been designed by the Naval Torpedo Station (NTS), in Newport, Rhode Island, by a group of engineers that were considered among the world’s experts in the craft of building torpedoes.  The Torpedo Station was subordinate to the Bureau of Ordinance (BU-ORD), the bureaucracy that was in charge of designing and/or approving all of the fleet’s onboard weaponry, from anti-aircraft machine guns to 16-inch battleship guns, as well as the torpedoes carried on submarines, PT boats, destroyers and a few cruisers. 

The Mark XIV was a marvel of technology at the time; its turbine engine made it a much faster “fish” than the earlier Mark X.  Most importantly, it had a magnetic detonator, enabling it to explode beneath the enemy ship.  The explosion would create a huge cavity of gas under the ship, into which the ship would sag, fracturing the keel.  In theory.  (And the theory was a good one; it’s the same way the modern Mark 48 found on today’s submarines attacks surface ships). 

Admiral Lockwood – who, unlike most submarine admirals, had spent his entire career as a submariner – was suspicious of the hardware.  But the NTS was certain the problem was with the crews.  Or the maintenance.  Or something.  Not the bureaucracy.

Lockwood ordered one of his submarines to test-fire a series of torpedoes at some borrowed fishing nets – and found for starters that they were running much, much deeper than set. 

Torpedoes of the era could be set to run at different depths – to account for smaller or larger targets with shallower or deeper “drafts” (depth below the surface), or to strike below a battleship’s armor plating, or to take advantage of the magnetic detonators.  The depth sensor  – which operated by sensing the water pressure, and maneuvered the torpedo to the desired depth – had originally been located in the middle of the torpedo – but a technical chanage had pushed it aft, along the slope toward the propellor.  Where the onrushing water filling in behind the speeding torpedo had lower pressure, causing the torpedoes to swim deeper to find the pressure analogous to the depth setting. 

The NTS, afflicted with complacent hubris as much as Depression-era budget cuts, had relocated the sensor – and then skipped the testing process.  The change to the depth control went into combat without testing.

Lockwood’s staff advised the submarines to correct their depth settings.

It didn’t help.   Torpedoes still weren’t exploding.  And the NTS and BU-ORD still blamed the fleet. 

Lockwood’s suspicion turned next to the magnetic detonator itself.  Lockwood’s engineers discovered what German submariners had learned a year before; magnetic detonators operate by sensing the magnetic field around a large metal object like a ship – but that magnetic field changes in different parts of the world, just as does Earth’s magnetic field.  Without accounting for those changes, the detonator would be unreliable.

So Lockwhood ordered his skippers to disconnect the magnetic detonators, and rely on the good old-fashioned contact detonators – basically the same mechanism as the firing pin on a rifle. 

And so 70 years ago today the Tinosa fired 15 torpedoes, with two explosions – both of them from glancing blows at bad angles.  It was the only data point the engineers had; straight 90 degree hits – theoretically perfect hits – would go dud, while glancing blows at oblique angles would explode, sometimes. 

Orders when out to a fleet full of perplexed skippers; take shots at oblique angles.  Avoid straight-on hits.  Those were, of course, harder shots to hit – but the rate of explosions rose. 

Finally, Lockwood ordered a submarine to fire a load of torpedoes into a cliff on the Hawaiian coast.  As expected, only a few of the torpedoes exploded.  Divers recovered – veeery carefully – the dud fish, and the engineers at Pearl Harbor took them apart…

…and found out that the contact detonators – the “firing pin” assemblies for the torpedoes – were twisted out of shape by the impact with the target; the force of the impact with the cliffs, or ships, bent the system’s guide rails before the firing pin could strike the explosive primer.  It was mechanically nearly identical to the assembly on the older Mark X torpedoes…

…which were 15 mph slower than the Mark XIV.  The extra energy caused by all that extra speed released physical forces that were beyond the older assemblies’ design tolerances…

…except when the hit was an off-angle glancing blow.   Like the Tinosa’s two “hail Mary” shots. 

The NTS was non-plussed.  BU-ORD hushed the story up until long after the war.  They had never tested the firing mechanism under real-world conditions with the new, faster torpedoes.

Lockwood’s engineers built new guide rails – machined out of metal salvaged from the propellors of Japanese planes shot down at Pearl Harbor; lighter, stiffer, better able to stand up to the stresses involved in smacking into a steel wall at 45 knots (55 mph). 

And finally – over a year and a half into the war – the US Navy’s submarine service was truly ready for combat. 

The subs sank over half of the Japanese ships lost in the war; they actually accomplished with Japan what the Germans attempted to do with Britain – starved it out.  Japan was utterly dependent on overseas trade for most of its economy, especially oil – and without a merchant marine, there was no way for Japan to get oil, or most other raw materials.  There is a strong case to be made that the submarines did the lion’s share of the work defeating Japan.  And because of the difficulties with the Mark XIV torpedo, they really didn’t get a start on the job until late 1943. 

It came at a cost, of course; 22 US submarines were sunk in action, 20 are still missing in action – they still don’t know what happened to them, although it’s presumed they were lost in action – and 10 were lost in various training or testing accidents. Over 3,000 submariners died, making it the most dangerous job in the Navy.

Nobody knows how many of those subs were lost as they watched their torpedoes bounce ineffectually off the sides of their targets. 

And the Bureau of Ordinance and the Naval Torpedo Station, like most government bureucracies, never really did get called to account.   At least one senior submariner, after the war, moped that it was a shame they couldn’t have spared one atomic bomb for the Naval Torpedo Station.