Spies, Lies and Secret Weapons (2001)

Maximum speed of 60 to 80 km/h! Whether submarine or torpedo - it is not possible to go faster under water according to the established rules of physics. Friction and turbulence prevent higher speeds in such a "dense" medium. In addition, a well-known problem that submarine engineers have been fighting with for centuries emerges, because it can destroy any normal ship's propeller at too high a rotational speed: cavitation - a rare phenomenon that the Russian Marines and the US Navy now want to use for firing underwater and maybe even high-speed submarines. During the hot phase of the Cold War in the 60s, using the motto "If you can't prevent it, use it," the Russian scientist Mikhail Merkulov came upon the bold idea of artificially generating such a cavitation bubble, which is so big that a torpedo has space inside, where it is protected and virtually free from friction and turbulence, to reach speeds beyond those that had up till then been possible.