The Contact Exploder Problem

In June 1943, after many of the boats disconnected the magnetic feature of the Mark 6 Exploder, the problem of duds was discovered. The contact exploder device was a backup to the magnetic feature of the exploder, but it too was flawed because it frequently failed to detonate the warhead when the torpedo struck the ship’s hull. It failed most often when impacting at right angles (a perfect 90o angle to the ship’s centerline), the optimum position. The better job the submarine commander did in aligning the target, according to the preferred tactic, the greater chances were of a dud!

To find this problem the Fleet conducted another series of tests in mid 1943 by firing several warshot torpedoes at a submerged vertical cliff-face in Hawaii. These tests showed that the weak exploder mechanism was crushed in a perfect 90o shot. To find out why, some drop tests were conducted using concrete filled dummy warheads. When the warheads were set to hit a steel plate head-on most of the exploders failed, but when the plate was tilted 45o there were fewer failures.

This turned out to be a simple mechanical problem: the firing pin jammed. The direction of motion of the firing pin (activated by a spring) was not along the axis of the Mark 14 Torpedo but lay perpendicular to it. Under the shock of torpedo impact, sufficient friction was created between the firing pin and its guide walls to slow down the action of the pin against the primer cap (the pin did not always travel far enough or fast enough to strike the primer cap with enough energy to activate it). That is, if the impact shock didn’t break the pin and/or guides first. More than just a stronger spring would be needed; the firing pin had to be redesigned.

At Pearl Harbor the solution was to produce a lighter weight firing pin. They were able to find enough high strength, light weight metal from the propeller blades of downed Japanese Pearl Harbor raiders (a novel method of recycling).

By the fall of 1943 solutions had been found for the major problems with the Mark 14 Torpedo. But, a few more issues needed to be resolved. There was a tendency for some torpedoes to immediately make a circular run upon launch with unfortunate consequences for the submarine (at least one submarine fell victim to this problem). And there was a problem with the wake generated by the steam driven propulsion system which could alert the target (the Mark 18 electric torpedo prevented this).

All the bugs were eventually worked out and the Mark 14 Torpedo did prove effective. The Mark 14, and to some extent its successor the Mark 18, sent to the bottom some 5 million tons of enemy shipping and damaged 2.5 million tons more. The Mark 14 itself sent 4 million tons of Japanese war material to the bottom. Mass production was eventually achieved with production rates reaching 12,000 torpedoes during the first 6 months of 1944. According to BuOrd, January 1944 saw this particular controversial chapter in its history draw to a close.

Actions Taken By BuOrd To Resolve The Torpedo Problems

Continue Range Testing

BuOrd continued funding, and authorizing, range testing of torpedoes (but not enough emphasis was placed on tracking the depth of the torpedo). Aircraft were used by the range at Newport to look for any erratic performance and to observe torpedo deflections. BuOrd even used submerged nets on a few occasions but found the results misleading and the effort very expensive and cumbersome. The nets did not hang straight down, but swung up from the vertical in the most mild current; and the distance from the top of the net to the hole made by the torpedo was not the same in water as it was when the net was taken out of the water. So when the net results differed from the depths recorded by the torpedo, the data from the net testing was ignored.

In the summer of 1943 BuOrd conducted a series of test firings of torpedoes against steel plates lowered in the water and reproduced the problem of the sticky firing pins. They were working on their own solution when word came of the approach taken by Pearl Harbor (and they quietly left that issue alone).

As a direct result of the feedback from the Fleet on the operating capabilities of the Mark 14 Torpedo and its Mark 6 Exploder BuOrd decided it had to improve the method of tracking torpedoes. The tracking range at Newport was eventually improved during the later stages of the war through the use of several sets of acoustic tracking hydrophones that allowed both the speed and deflection of a torpedo to be monitored during its run down the range (but still without the capability to monitor depth). A similar acoustic tracking range was established at Keyport, Washington.

Continue To Improve The Mark 14 Torpedo

BuOrd continued making modifications to the Mark 14 Torpedo and to the Mark 6 Exploder, always maintaining faith in the ultimate success of the Mark 6. It was even redesigned once to remove a small electrical generator in favor of a battery as the power source, and the arming distance was increased.

It can be appreciated that efforts to improve the exploder (and BuOrd’s credibility) really took off in the summer of 1943 when the entire Pacific Fleet (submarines and destroyers) refused to use the magnetic influence feature. BuOrd hoped a modified and reliable exploder could eventually be “sold” to its only customer, the operating forces (and also quell the heated rhetoric between them and the Fleet).

Continue New Torpedo Development

Efforts continued toward developing the Mark 18 electric torpedo as a replacement for the Mark 14. By late 1944 the Mark 18 (modeled after the German G7e recovered from the captured U-570 and some that were found intact on U.S. east coast beaches in 1942) entered Fleet service. The new torpedo eliminated the bubbles that followed in the wake of the Mark 14 Torpedo, but was much slower, and occasionally there were fires or hydrogen explosions from its batteries.

A Matter Of Priority

As important as the Mark 14 was, it was not given the highest priority at Newport by BuOrd. The aircraft launched Mark 13 Torpedo had the highest priority - and its greatest hour of glory came on 7 April 1945 when it was used to sink the battleship YAMATO and several other Japanese warships, but such success came only after years of working out its bugs. Then there was work to be done on the Mark 15 surface launched torpedo for destroyers, though at a lower priority than the Mark 13 & Mark 14

Many thanks to CHARLIE GUNDERSEN for this, as usual, outstanding piece of research writing. We look forward to more from CHARLIE and - what about YOU? We welcome writings by Members, whether of a technical, historical or personal nature.

More Mark 14 Torpedo

The Silent Service WWII USN Mark 14 Submarine Torpedo. Part 1 [# 120]
The Silent Service WWII USN Mark 14 Submarine Torpedo. Part 2 [# 121]
The Silent Service WWII USN Mark 14 Submarine Torpedo. Part 3 [# 122]
The Silent Service WWII USN Mark 14 Submarine Torpedo. Part 4 [# 123]
The Silent Service WWII USN Mark 14 Submarine Torpedo. Part 5 [# 124]