submarines

Submarines are watercraft capable of operating underwater for extended periods. They use ballast tanks to submerge and expel ballast to surface, enabling stealth and surprise in naval warfare and science exploration.

Most modern submarines rely on sealed pressure hulls to withstand water pressure at depth. Propulsion ranges from diesel-electric systems on many non-nuclear submarines to nuclear reactors on ballistic missile and many attack submarines, which provide extended range and endurance. Diesel-electric submarines typically operate on batteries while submerged, surfacing or snorkelling to recharge. Nuclear submarines can remain submerged for months, limited mainly by crew endurance and food supply.

Submerged navigation and operations rely on sonar, inertial navigation, and periscopes or optronic masts to observe above water. Ballast-control systems enable diving and maintaining depth. Submarines carry a mix of weaponry, typically torpedoes and, on some classes, missiles housed in vertical or packaged tubes. Ballistic missile submarines provide stealth-based strategic deterrence, while attack submarines hunt surface ships and collect intelligence. Submarines also support covert intelligence, reconnaissance, and special operations.

Historically, attempts to build underwater vessels date to the 19th century, with significant development during the two World Wars, especially German U-boats. The postwar period saw the advent of true submarines with diesel-electric propulsion, followed by the introduction of nuclear-powered submarines in the 1950s. Since then, submarine design has evolved toward greater stealth, endurance, automation, and precision strike capability.