page_title: Mark 6 exploder
section_title: Development
hierarchical_section_title: Mark 6 exploder / Development
caption_attribution_description: English: Test of 1926 Mark 6 exploder prototype
context_page_description: The Mark 6 exploder was a United States Navy torpedo exploder developed in the 1920s. It was the standard exploder of the Navy's Mark 14 torpedo.
context_section_description: Early torpedoes used contact exploders. A typical exploder had a firing pin that stuck out from the warhead and was restrained by a transverse shear pin. The torpedo would hit the target with enough energy to break the shear pin and allow the firing pin to strike a percussion cap that ultimately detonated the warhead. An arming impeller was an additional safety device: the firing pin could not move until the torpedo had traveled a preset distance.
  Just before World War I, the Bureau of Ordnance (commonly called BuOrd) started developing an inertial exploder. The result was the Mark 3 exploder.
  Warships employed defenses against torpedoes. A new technology, torpedo blisters, appeared on capital ships. The torpedo would explode against the blister but do little damage to the hull. Torpedo blisters were tested on two battleships, the decommissioned South Carolina and the unfinished Washington; the conclusion was the Mark 10 torpedo, with its contact exploder, could not disable a major warship. Torpedoes would need to explode underneath a capital ship, where there were no blisters or other armor. The Mark 14 torpedo was designed at the Newport Torpedo Station (NTS), Newport, to replace the Mark 10, which had been in service since World War I. Its fairly small 643 lb (292 kg) warhead required it to explode beneath the keel where there was no armor.
  This led to the development of a magnetic influence feature, similar to the British Duplex and German models, all inspired by German magnetic mines of World War I. The Mark 6 was intended to fire the warhead beneath  the ship, creating a huge gas bubble which would cause the keel to fail catastrophically.
  The Mark 6 exploder, designated Project G53, was developed "behind the tightest veil of secrecy the Navy had ever created." In less than two years, Newport Torpedo Station produced a prototype with help from General Electric. The prototype exploder was fitted to a Mark 10 torpedo and test-fired in Narragansett Bay on 8 May 1926; the submarine USS L-8 was the target.
  In the first test, the torpedo ran underneath the target submarine but did not explode; a second test was successful.  Those two shots were the only live-fire tests until World War II. After several redesigns, General Electric in Schenectady made 30 production units, at a cost of US$1,000 apiece. The exploder was tested at the Newport lab and in a small field test aboard USS Raleigh.
  At the urging of Lt. Ralph W. Christie, who headed the Mark 14's design team, equatorial tests were later conducted by 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.
  Due to budgetary constraints, very few live-fire trials of the torpedo or exploder were ever conducted. The goal of most exercise firings was to get the torpedo to run under the target, after which it was assumed the magnetic influence feature would do the work. This misplaced trust in the magnetic exploder helped mask the depth problems encountered by early torpedoes, for if the exploder were to work properly a depth error of a few feet would not matter. Chief of Naval Operations William V. Pratt offered the hulk of Cassin-class destroyer USS Ericsson, but prohibited the use of a live warhead, and insisted 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."
caption: A failed 1926 test shot.
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