Sjöormen-class submarine

RSS Chieftain
Class overview
Builders:	Kockums
Operators:	Swedish Navy  Republic of Singapore Navy
Preceded by:	Draken-class
Succeeded by:	Näcken-class
Planned:	5
Completed:	5
Active:	4
Retired:	1
General characteristics
Displacement:	Surfaced: 1,125 t (1,107 long tons; 1,240 short tons) Submerged: 1,400 t (1,400 long tons; 1,500 short tons)
Length:	50 m (164 ft 1 in)
Beam:	6.1 m (20 ft 0 in)
Draught:	5.1 m (16 ft 9 in)
Propulsion:	1 shaft 2× Pielstick diesel 1× ASEA electric motor
Speed:	Surfaced: 15 kn (28 km/h; 17 mph) Submerged: 20 kn (37 km/h; 23 mph)
Complement:	23
Sensors and processing systems:	FAS
Armament:	4× 533 mm (21 in) Torpedo tubes 2× 400 mm (16 in) Torpedo tubes Mines

The Sjöormen class were a group of submarines built for the Swedish Navy in the late 1960s. They had a teardrop shape and were capable of diving to 150m. At the time of their deployment they were regarded as one of the most advanced non-nuclear submarine-classes in the world, incorporating many new features including x-rudder and anechoic tiles. Both speed and underwater endurance was at this time very high for a conventional submarine. The submarines were retired by Sweden in the early 1990s. In the late 1990s, four submarines were acquired by the Republic of Singapore Navy and relaunched as the Challenger-class following modernisation and tropicalisation.

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Wikipedia