page_title: Mark 14 torpedo
section_title: Development
hierarchical_section_title: Mark 14 torpedo / Development
caption_attribution_description: English: Test of 1926 Mark 6 exploder prototype
context_page_description: The Mark 14 torpedo was the United States Navy's standard submarine-launched anti-ship torpedo of World War II. This weapon was plagued with many problems which crippled its performance early in the war. It was supplemented by the Mark 18 electric torpedo in the last two years of the war. Nonetheless, the Mark 14 played a major role in the devastating blow U.S. Navy submarines dealt to the Japanese naval and merchant marine forces during the Pacific War.
  By the end of World War II, the Mark 14 torpedo was a reliable weapon ultimately remaining in service for almost 40 years in the U.S. Navy, and even longer with other navies.
context_section_description: The design of the Mark 14 started in January 1931; the Navy allocated $143,000 for its development. The Mark 14 was to serve in the new "fleet" submarines and replace the Mark 10 which had been in service since World War I and was standard in the older R- and S-boats. Although the same diameter, the Mark 14 was longer, at 20 ft 6 in (6.25 m), and therefore incompatible with older submarines' 15 ft 3 in (4.65 m) torpedo tubes. (Later in the war, the Bureau of Ordnance (BuOrd) stopped producing Mark 10s for the S-boats and provided a shortened Mark 14.)
  Torpedoes consist of several subsystems, and those subsystems evolved over time. Torpedoes are also tailored for their application. Submarine torpedoes, such as the Mark 14, are constrained by the dimensions of the submarine's torpedo tubes: 21 inches in diameter and a certain maximum length. Submarines are expected to close with their targets, so the torpedoes do not need a long range. In contrast, torpedoes fired by destroyers need greater range because their approach would be under fire from their targets. Improvements in the propulsion engine power output allowed the Mark 14 to have a top speed of 46 knots compared to the Mark 10 Mod 0's 30 knots. Steering is controlled by a gyroscope; the gyro on the Mark 10 Mod 0 was spun up in the torpedo tube and was not powered after launch; the gyro on the Mark 14 was continuously powered by its air flask. The depth control on the Mark 10 was slow — the depth would not stabilize quickly; the Mark 14 depth stabilization was improved.
  The design for the Mark 6 exploder used in the Mark 14 torpedo had started at the Naval Torpedo Station (NTS), Newport, in 1922. Ship's armor was improving with innovations such as torpedo belts and torpedo blisters (bulges). To circumvent these measures, torpedoes needed larger warheads or new technology.  One option would use a fairly small warhead but was intended to explode beneath the keel where there was no armor. This technology required the sophisticated new Mark 6 magnetic influence exploder, which was similar to the British Duplex and German models, all inspired by German magnetic mines of World War I. The Mark 14 shared this exploder with the concurrently-designed surface ship Mark 15 torpedo.
  The Mark 6 exploder, designated Project G53, was developed "behind the tightest veil of secrecy the Navy had ever created." Exploders were tested at the Newport lab and in a small field test aboard USS Raleigh.  At Ralph Christie's urging, equatorial tests were later conducted with USS Indianapolis, which fired one hundred trial shots between 10°N and 10°S and collected 7000 readings. The tests were done using torpedoes with instrumented exercise heads: an electric eye would take an upward-looking picture from the torpedo; the magnetic influence feature would set off some gun cotton. Inexplicably, no live fire trials were ever done with production units. Chief of Naval Operations William V. Pratt offered the hulk of Cassin-class destroyer Ericsson, but prohibited the use of a live warhead, and insisted the Bureau of Ordnance (commonly called BuOrd) pay the cost of refloating her if she was hit in error. These were strange restrictions, as Ericsson was due to be scrapped. BuOrd declined. A service manual for the exploder "was written—but, for security reasons, not printed—and locked in a safe."
  Torpedoes were sophisticated and expensive. The cost of a torpedo in 1931 was about $10,000 (equivalent to $168,000 in 2019).  The development of the Mark 13, Mark 14 and Mark 15 torpedoes was done frugally. The Navy did not want to do live fire tests that would destroy a $10,000 torpedo. The Navy was also reluctant to supply target ships. Consequently, there were no live-fire tests, and the designers had to rely on their judgment. Sadly, that judgment sometimes led to problems: a contact exploder that worked reliably at 30 knots (15 m/s) failed at 46 knots (24 m/s). In addition, the Navy had limited experience in using torpedoes in combat.
caption: The only live fire test of the magnetic influence exploder before the war occurred in 1926.  In this picture of the first shot, the Mark 10 torpedo with the experimental exploder ran underneath the target without exploding.  The second test shot exploded under the target submarine and sank it.  Although the Navy conducted other tests, those tests were nondestructive: the torpedoes would not be damaged by the tests.
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