US Subs in 1942
I think long ago that issue was settled on the idea that the torpedoes wouldn't be compatible on US subs. And there is the whole issue of trying to get the idea passed the Torpedo Mafia. Though I vaguely recall something about the older US subs (S-class?) having more reliable older torpedoes than in Hawaii and elsewhere. Is that true?
Correct, on torpedoes. While the British Mark VIII was a 21 in torpedo, it was incompatible with mechanisms for setting controls in the US tubes and with the target solutions developed by the TDC (electro mechanical, so it isn't a software fix) designed for the Mark 14. Different weights, ranges, and speeds. Settings could be calculated manually and set on the war shot prior to loading in the tube, but could not be adjusted after it is in the tube (not good). So, the British Mark VIII was not a solution even if the "torpedo Mafia" could be convinced (even though it would fit in the tube).
The older US Mark 10 torpedoes, used in the S-boat would have the same problem in the Fleet Boat. Also, the Mark 10 had a "light warhead (497 lb TNT), had a very short range (3,500 yds), and was slow (31 kts). While its contact exploder worked properly and it ran at the correct depth (more on this a little later), but it was obsolete (as was the S-boat).
On 8 December 41, the USN had
46 Fleet Boats (Mark 14 armed) and
36 S-boats (Mark 10 armed) in commission. The US commissioned 14 additional fleet boats by May 42 and 21 more by December 42.
Only S-boats operated out of the PI prior to its fall, but fleet boats operated out of Pearl and Freemantle throughout the war. There had also been a submarine base and tender at Guam. Some S-boats operated out of Freemantle, but were moved out during 1942.
US submarines sunk 493,000 tons of Japanese merchant shipping during 1942.
Virtually all of that was
sunk by fleet boats using Mark 14 torpedoes. The S-boats did sink some Japanese shipping using the Mark 10, but the Mark 10 was not a solution to the Mark 14 problem (In fact, due to institutional Torpedo development stupidity, it was part of the problem).
The Mark 14 had 4 major problems: 1) ran too deep; 2) magnetic exploder did not work; 3) contact exploder was too weak; and 4) circular runs. The circular runs were pretty rare (thank the stars) and were not easily fixed. Two very significant problems were related to the fact that the depth sensing mechanism and contact portion of the exploder were copied from the Mark 10. Relative to the Mark 10, the Mark 14 had a more overall mass, a significantly heavier warhead and ran 15 kts faster. Increased rate of water flow over the depth sensor caused the sensor to register a lower pressure and adjust the depth downward, and the heavier nose also affected the depth calibration. Hence, the torpedo ran 10 ft too deep. Depth problem was proven in the minds of the sub force commanders and submarine skippers by June 42 (Lockwood's net tests in Freemantle). Simple setting change and the torpedo hits. Sub skippers also noted
early in the war that the shots which ran under enemy ships did not explode and they rightfully suspected the magnetic exploder. A large but unknown percentage of sub skippers
disabled the magnetic portion of the exploder after leaving port (in spite of what the Torpedo MFWIC claimed) from early 1942 onward. The contact exploder was designed for the lighter, slower Mark 10 torpedo and was physically too weak for the impact force of the Mark 14. A perfect, square hit would virtually never explode, but it would work some percentage of the time when it hit on an angle. Hence, the US subs were sinking ships. The contact exploder problem was finally recognized in July 43 and quickly fixed with field expedient fixes. The magnetic exploder was never really fixed during the war, but was disabled in the field.
