Unlike the Germans, the Americans lacked combat experience with torpedoes. By the time America entered World War I, the primary naval mission was protecting Allied shipping from German torpedoes. Only 11 U.S. torpedoes were fired in anger, all of which either missed or were aimed at phantom targets.
Still, American submariners had confidence in their torpedoes. The Navy's World War I-era "S-boats" used the Mark 10 steam torpedo, an impact weapon of proven reliability. For the more modern boats that eventually followed, the Torpedo Station at Newport, R.I., developed the much more capable Mark 14 steam torpedo, which could use either an impact detonator or the new, top-secret Mark 6 magnetic influence detonator.
However, funding was very scarce during the 1920s and 1930s, so the Mark 14 and the Mark 6 detonator were developed and tested on a shoestring budget. The Torpedo Station conducted only one test using live warheads, with hand-built Mark 6 detonator prototypes installed in old Mark 10 torpedoes. In two shots on the Newport test range using a decommissioned submarine as the target, one torpedo passed beneath without exploding, apparently running too deep, but the other exploded below the keel, quickly sinking the sub.
Subsequent tests at sea near the equator seemed to demonstrate that the detonator performed as designed regardless of variations in the earth's magnetic field. However, the cruiser used as a target was an operational warship, so the test torpedoes carried only exercise heads. Instead of an explosion, a photoelectric sensor called an "electric eye" activated a film camera to record the shadow of the target's hull as the torpedo passed beneath, and the detonator ignited a small amount of guncotton to show it was activated by the ship's magnetic field.
The influence detonator went into production with no additional testing. To ensure that it remained a closely guarded secret, the Mark 14 torpedo entered service with only the impact detonator installed. Not until the summer of 1941 were the first fleet boat crews introduced to the Mark 6 detonator and told that it would enable them to sink a ship with a single torpedo.
(Top) The Mark 14 was the only torpedo carried by U.S. fleet boats when the Japanese attacked Pearl Harbor on Dec. 7, 1941. (Bottom) The Mk 6, Mod 1 magnetic influence detonator, photographed at the U.S. Naval Torpedo Station, Newport, R.I. (U.S. Navy photos courtesy of Norman Polmar)
Ignoring the Failures
Once hostilities began, American submarine commanders encountered the same problems as the Germans: premature detonation, failure to detonate, and running too deep. Some skippers took great pains and incurred great risks to investigate and document these problems during war patrols—to no avail. Unlike the German submarine leadership, American shore-based commanders had no combat experience and felt little solidarity with their embattled skippers.
Before the war, the American submarine service had demanded excessive caution from its skippers. As a result, higher-level commanders had to weed out timid, unproductive skippers in the early days of the war. Driving their sea-going subordinates to achieve results, shore-based commanders persistently dismissed complaints about malfunctioning torpedoes and blamed skippers and their crews for failing to get hits. Occasionally, someone might refer a complaint to the Bureau of Ordnance (BUORD) and the Torpedo Station, but these organizations invariably concurred with the operational leadership in blaming the failures on poor shipboard maintenance or faulty combat procedure.
Correcting the Depth Problem
The first problem to get addressed was excessive depth. Pre-war tests at the Torpedo Station indicated the Mark 10 and Mark 14 both ran four feet too deep because of calibrating with exercise heads, but submariners in the Far East were not informed until nearly a month after Pearl Harbor. After assuming command of U.S. submarines based in Fremantle, Australia, in May 1942, Rear Adm. Charles Lockwood, decided to conduct his own tests. A series of realistic trials in June and July revealed that the Mark 14 ran an average of 11 feet below the depth setting.
The Torpedo Station not only failed to account for the different buoyancies of exercise heads and warheads, it also neglected to simulate combat launch conditions or allow for the deterioration of depth control apparatus over time. It even failed to check torpedo performance against an absolute standard, relying instead on test sensors installed in the torpedoes themselves, which merely echoed the incorrect readings of the weapons' own depth and roll sensors. Not until August 1942, eight months after Pearl Harbor, did BUORD determine that the torpedoes were running about 10 feet too deep and issue instructions to solve the problem
Meanwhile, the first defect of the impact detonator was detected and resolved in the spring of 1942. To prevent the explosion of one torpedo in a spread from prematurely detonating another, the detonator included a diaphragm that, when subjected to the pressure of a shock wave, drove a small pin into the firing mechanism, blocking detonation. But the diaphragm was far too sensitive, so even normal water pressure at periscope depth could drive in the pin. The solution was simply to disconnect the pressure override.
Eliminating the Magnetic Influence Detonator
By February 1943, when Rear Adm. Lockwood took command of the Hawaii-based submarines under Pacific Fleet Commander-in-Chief Adm. Chester Nimitz, complaints about the Mark 6 influence detonator had become so strident that even BUORD was having second thoughts. However, the Bureau incorrectly concluded that the malfunctions were caused by variations in the earth's magnetic field, so its recommendations, issued May 7, proved ineffective.
Frustrated by clear evidence of Mark 6 malfunctions in decoded Japanese communications, Lockwood took the bull by the horns and persuaded Nimitz to order the Mark 6 disconnected for good. Nimitz's order, however, did not apply to the submarines based in Australia, which were part of the Seventh Fleet, reporting to Gen. Douglas MacArthur. The commander of those submarines, Rear Adm. Ralph Christie, was an MIT-trained engineer who had been personally involved in developing the Mark 6. Christie continued to insist that his boats use the flawed detonator right up to the end of 1943, when a new Seventh Fleet commander finally ordered it deactivated.
The Last Problem
Elimination of the influence detonator exposed grave defects in the impact detonator. On July 24, 1943, yet another skipper went to great lengths to document torpedo failures, systematically firing torpedo after torpedo at the same tanker under near-perfect conditions until he had recorded 11 hits with no effect. Lockwood then authorized the experimental firing of impact torpedoes against a Hawaiian cliff face, which began on Aug. 11.
Examination of the first failed torpedo revealed that the fragile detonator mechanism, distorted by the impact, prevented the firing pin from striking with sufficient force to initiate an explosion. Subsequent drop tests on land with dummy warheads showed that a perfect hit at 90 degrees crushed the detonator and prevented it from working, whereas a glancing blow at 45 degrees left it sufficiently intact to set off an explosion. Twenty-one months after Pearl Harbor, the last major torpedo malfunction was finally identified. While the fleet made interim fixes, the Torpedo Station conducted follow-up tests and ordered a redesign.
A German G7e electric torpedo on display at the Naval Undersea Museum in Keyport, Wash. U-boats carried both the pioneering wakeless G7e and the G7a steam torpedo from the outset of World War II.
(Photo courtesy of Naval Undersea Museum).
Remembering the Lessons
America and Germany learned the hard way that torpedoes are finicky weapons that cannot tolerate shortcuts. The most complex naval weapons of World War II, they demanded meticulous design, rigorous testing and intensive maintenance—not to mention exacting targeting and launch procedures. Lack of rigor at any stage from initial design to the torpedo's use in combat could result in failure, and the many opportunities for mistakes made it hard to tell where the fault lay, even after the weapon's poor performance became obvious.
Seen in this light, German and American torpedo failures are quite understandable. Only in hindsight is it apparent that the more complicated torpedoes developed for World War II demanded an unprecedented level of technical and operational evaluation. And even Germany's veteran submarine leaders never thought to second-guess their Torpedo Directorate until the problems became obvious.
Germany fixed most of her torpedo problems in less than half the time it took the United States because her submarine leadership was more experienced and because submarines were the mainstay of her navy. Doenitz and his staff knew from the start how to establish a trusting relationship with U-boat skippers and how to evaluate their reports. Senior American submariners had to learn those skills on the job. U-boats took the lead in Germany's naval war, while American submarines played second fiddle to battleships before Pearl Harbor and to aircraft carriers afterwards. If U.S. carriers had lost the Battle of Midway because their bombs failed to explode, it's safe to say the problem would have gotten a lot more attention than torpedo failures did.
Fortunately, American submariners and their technical establishment took the torpedo failures very much to heart. The rigorous testing program established after the war continues to ensure the reliability and effectiveness of U.S. torpedoes to this day. The need for excellence in all aspects of torpedo development and handling—above all in technical and operational evaluation—has never been greater than it is now, and as budget constraints loom once more, the need to bear in mind the bitter lessons of World War II has never been clearer.
Anyone interested in learning more can begin with the three sources used for this article: Hitler's U-Boat War, the Hunters, 1939-1942, by Clay Blair; Blair's monumental Silent Victory, the U.S. Submarine War against Japan; and Ship Killers, a History of the American Torpedo, by Thomas Wildenberg and Norman Polmar. (U.S. Navy photos used in this article are from Ship Killers.)
Mr. Patrick is UNDERSEA WARFARE Magazine's senior editor.
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