Unscripted and unedited, just a guy sharing info about submarines. The submarines being built today are nothing like the ones from 100 years ago. Yet one critical element has remained the same since the 1920s. The torpedo tubes are all the same size. 533 millimeters (21 inches) in diameter. You see this in the specs of U.S. Navy, Russian Navy, French, Chinese, British, and even North Korean Subs. Here is why, and some history and exceptions.