The Mark 10torpedo was a torpedo put into use by the United States in 1915. It was derived from the Mark 9 aircraft torpedo converted to submarine use. It was used as the primary torpedo in the R- and S-class submarines. It used alcohol-water steam turbine propulsion. It was succeeded by the problematic Mark 14 torpedo, but remained in service in S-boats & fleet submarines through the Pacific War. The Mark 10 featured the largest warhead of any U.S. torpedo developed at that time. Stockpiles of Mark 10 Mod 3 torpedoes were used extensively during the first part of World War II due to short supply of the newer and longer used essentially the same control package as the newer Mark 14 for depth and direction. The running depth could be set to between. The gyro angle could be set for a new course up to 90 degrees port or starboard from the current course of the submarine before launch. The Mark 10 would run out of the tubestraight ahead for the "reach", then turn to a new, pre-set course, through a total angular targeting of 180 degrees over the end of the submarine, and then run on this intercept course straight to the target. To use a Mark 10 Mod 3 torpedo in fleet submarine tubes required a gyro angle setting spindle adapter be slipped into the torpedo housing to extend the reach of the spindle into the torpedo. In pre-fleet submarines, the gyro setting machinery was on the outside of the tube, while the fleet submarine gyro spindles are on the inside of the tube. The Mark 10 torpedo had the same "deep running" problem as the Mark 14. By January 5, 1942 the Bureau of Ordnance informed Commander, Submarines, Pacific Fleet the Mark 10 torpedoes ran four feet deeper than set. Because the Mark 10 used Mark 3-1 and Mark 3-3 exploder mechanism with contact-only firing, it suffered none of the problems with prematures or duds the Mark 14 did. However, for a short periodat the beginning of the war, the Mark 10 was viewed as more reliable, and in some cases preferred over the Mark 14.
