Ubåde

Ubåde, Danish for submarines, are watercraft designed for independent operation underwater. They can remain submerged for extended periods, using ballast tanks to dive and to surface. Modern submarines have sealed, pressure-resistant hulls and life-support systems to sustain crew and equipment during submerged missions.

Propulsion varies by class. Many conventional submarines use diesel-electric power: diesel engines run on the surface or with a snorkel to recharge batteries, while electric motors drive the propeller when submerged. Nuclear-powered submarines employ a reactor and turbines to provide long-endurance propulsion without surfacing. Some designs use air-independent propulsion to extend submerged endurance.

Military submarines fulfill three broad roles: attack submarines armed with torpedoes and missiles; ballistic-mullet submarines for strategic deterrence; and special-purpose submarines for intelligence, mine-laying, or rescue. Civilian and scientific submarines perform deep-sea research, underwater archaeology, maintenance, and tourism, including crewed submersibles and bathyscaphes.

Key design features include a pressure hull to withstand depth, ballast tanks for buoyancy control, sonar and other sensors, periscopes or photonics for surface observation, and life-support systems. The history of submarines extends from early diving bells and experimental craft to modern fleets and research platforms. The first practical submarines emerged in the 19th century and later played major roles in the world wars. The postwar era brought nuclear propulsion, enabling continuous submerged operation and reshaping naval strategy.

Note: Ubåde is Danish for submarines; other languages use different terms such as ubåt or ubåter.