Mar 8, 2015


Admiral Raeder ordered a court-martial investigation which found out that the construction of the fuses were not be done carefully and that there was only insufficient experimentation before the war.

The German Navy was already short in financial resources, so it was not easy to realise in peace the exact war conditions.

To fire a live torpedo on a real target is even an enormous cost for a big navy.

That's why certainly the US Navy had the same problems as the German. The torpedoes run to deep, the magnetic ignition worked to early or not at all and the impact ignition was even worse than the German.

Admiral Riedel one of the responsible officer in the German naval arms office suicided.
A number of U-boats had been equipped with a new type of firing pistol with four bladed propellers which was liable to fail to function. These torpedoes with the pistol had never been adequately tested by the Germans.. On April 20th 1940, as a result of this accumulation of torpedoes failures during the Norwegian operations, the Commander-In-Chief set up a Torpedo Commission to investigate the problems. As a result to the already known causes, the Commission established the fact that the contact pistol showed a very considerable percentage of failures due to faulty action of the striker & the ineffectiveness of the initial charge, and that the pistol was liable to fail when the angle of incidence of a hit was less than 50*. The pistol had been constructed for an angle of incidence of 21*. These German torpedoes in question was the Mark G7a and the Mark G7e As a result of the findings, the Commander-In-Chief set up a Court of Inquiry into investigations that led to the trial by court martial & punishment of the personnel of the Torpedo Institute who were responsible.


Peter Maas account of the exploder failures.
In his book, “The Terrible Hours”, Maas presents an interesting account of the American torpedo exploder failures and the solution to the problem – an incident remarkably similar to the German experience. When the torpedo failures became untenable, Adm. Lockwood COMSUBPAC brought then Captain “Swede” Momsen aboard to solve the problem which BUORD was either unwilling or unable to undertake. Momsen proposed to shoot live torpedoes against the underwater cliffs of Kahoolawe where those that failed to explode could be recovered in the relatively shallow water. His plan was approved and Momsen and a team of Navy divers accompanied by the submarine Muskellunge and support vessel Widgeon proceeded to the area and commenced firing torpedoes. 

They were able to repeat the submariners’ experience that the failure to fire was in some way associated with the angle at which the torpedo struck the target (cliff). Head on impact failed to explode the torpedo; a glancing impact fired the torpedo. Of course firing procedure called for the torpedo to strike the target head-on at a right angle to the target’s track which almost always guaranteed an exploder failure.

Unexploded torpedoes were recovered, disassembled, and examined which resulted in the determination that the problem was caused by the combination of firing pin inertia and friction in the pin guides; in short – the pins were too heavy. A number of firing pins were machined down in the shops at Pearl Harbor to reduce the mass. Modified exploders were tested which showed the lightening of the firing pin solved the problem.

Submarine Barb put to sea with a load of twenty modified torpedoes headed for the Japanese shipping lanes and as Lockwood reported later – “All major exploder problems suddenly disappeared.”


The torpedo problems of the US and Germany have an eerie number of parallels.

They had three major problems:
1) They ran much deeper than set
2) The magnetic exploder did not function properly
3) The impact detonator did not function well for dead on hits, only for glancing blows.

Torpedo development in the US was conducted by the powerful, and independent Bureau of Ordnance. They came up with the magnetic influence exploder in tremendous secrecy. The magnetic field exploder used the magnetic field of a ship to detonate the torpedo beneath a ship. This not only made the torpedo more deadly in general, but it also made the torpedo much more effective against battleships and other capital ships by striking below their massive anti-torpedo armor belts.

The magnetic influence exploder was seen as a great breakthrough device, and so was kept in total secrecy. Crews never practiced with it, and (this is key) it was never thoroughly tested in actual war-like conditions - no open ocean live fire tests: it was too secret to be tested properly. So the bugs never were worked out. Secrecy, not cost, was the reason for poor pre-war testing.

Then the war started. None of the problems were suspected, and they masked and confused each other. In addition, the US sub fleet was having tremendous leadership problems: pre-war skippers, picked by seniority, lacked aggressiveness, and were being sacked wholesale: up to one-third of all sub commanders were relieved for cause during these early war patrols. US crews were also very green, like the rest of the US military.

Add to this a critical torpedo shortage. The US sub force spent much of 1942 on the verge of running out of torpedoes. Since the magnetic exploder was seen as a 'shot multiplier', a 'one hit one kill' weapon, crews were ordered to use it regardless. Commanders who used too many torpedoes to sink a ship were severely criticized. More than a few sub commanders disobeyed orders to use the magnetic exploders, and used contact detonators, but faked their logs to hide their disobedience. The result was that high command felt the exploder must work, as some people had good results with them....

Continued field reports of bad torpedoes were dismissed as mistakes by poorly trained crews, or excuses by inferior, or cowardly, commanders.

Finally, it was realized that the torpedoes tended to go too deep (Admiral Lockwood finally fired some torpedoes though a fishing net and measured where the holes were), about 15 feet deeper than set. This was mostly because the 'atmospheric' diaphragm inside the torpedo that serves as a pressure reference for depth keeping tended to leak. Since a sub's internal pressure usually climbs during submerged operations from air being vented into the boat, the 'reference' diaphragms gradually had too high a pressure, leading the torpedo to go too deep. This is virtually the same problem as the Germans had, and solved, a few years earlier. By the way, the British also had, and solved, this problem... in WWI.

Then, against increasing field evidence, the magnetic influence exploder was gradually withdrawn from service, though Admiral Christie (who helped develop it) dragged his feet a great deal. Many of the problems of the magnetic exploder were the same as the Germans: it tended not to explode, or premature. Real world magnetic fields were more complex than the tightly controlled, ideal tests done by the bureau of ordnance. The bureau of ordnance had done hundreds of magnetic exploder tests using actual torpedoes and ships, but not in the open ocean.

The final problem was due to the contact detonator design. In the US design physical impact with the target released the firing pin, which travelled down some metal guides to hit the detonator. In a hard, direct, near 90 degree impact the impact was so hard that the front of the torpedo crumpled, and the guide rails bent, before the firing pin was finished traveling, jamming it. Either it didn't finish travelling, or it hit with too little force to set off the detonator. Glancing blows did not crush the nose as much, and the firing pin would travel down the guide pins as designed.

As relayed above, test shots against a cliff from a sub finally confirmed this. Finally drop tests on land onto a steel plate held at varying angles revealed the total problem. A redesign was made to isolate the guiderails, and make the firing pin lighter.

The Germans also had the same problem with their impact detonator, with the firing mechanism being crushed before it could operate in a direct, head on blow.

In both cases the torpedo bureaucracies, instead of acting with concern when field reports poured in with complaints about their weapon, became defensive and refused to even look at the problem till forced to by higher command.

In the end both sub services ended up with good weapons, though I think the US had the harder time of it. 


The Japanese were generally considered to have the 'best' torpedo, or at least a very advanced torpedo, in the Type 95 sub torpedo. This is very similar to the Type 93 'long lance' torpedo used by surface ships.

The Type 95 was a 21" steam torpedo, but used liquid oxygen, not air, for propulsion, giving it far more power and range. It could go 9km (about 6 miles) at 49 knots, several times as far as what air driven steam torpedoes of other nations could do.

However, it was very rare for a sub fired torpedo to strike anything at long range, and anything beyond a few thousand yards was tactically useless.

More important, the type 95 carried a 900lb warhead, about twice the size of early US torpedoes. (Since most of the volume of steam torpedo is really a compressed air tank, I presume the use of more compact liquid oxygen instead of air allowed for a larger warhead.)

In Boyd and Yoshida's "The Japanese Submarine Force and WWII" a Japanese officer is quoted as saying that Japanese torpedoes tended to go deep, up to 100ft, for the first few hundred yards of their run. Since they were designed for battle in the open ocean this was not seen as important. It would be a handicap fighting in shallow waters, as US subs often did.

The major thing about Japanese torpedoes is that they reliably ran in the direction they were sent, at the depth they were set to, and actually exploded when they hit something (with twice the warhead). That was something of a rarity in torpedoes in WWII.