The evolution of modern torpedoes goes back to just before the Civil War, when they could only maintain a straight course and preset depth. By the time World War I rolled around, navies around the world had developed a complicated manual procedure using slide rules. During World War II, almost all of the countries involved simultaneously developed analog guidance systems for their torpedoes.
The Torpedo Data Computer was developed by the U.S. Navy, which was way ahead of other guidance systems at the time due to it’s ability to automatically track a target. This distinct advantage not only helped American subs attack more accurately, it also became the standard for torpedo fire control. Dials and switches were used to perform trigonometric calculations for the torpedo to intercept it’s target. Although it was a large addition to a sub, it’s target tracking functions allowed crews to update the direction and other data as the ship was moving.
The original Mark I was completed in 1938, but was too complicated. Despite this, it was fitted to many of the existing submarines in service. In 1940, the first sub designed to use the TDC launched with the Mark III version on board. It was this version that became what is considered the best torpedo control system of the war.
