Le Tonnant (S614) was a ballistic missile submarine operated by the French Navy between 1980 and 1998. One of the first of her kind with the Navy, the boat conducted deterrence patrols as part of the French nuclear triad during the Cold War. Her duties were ultimately replaced by the s, and the boat was dismantled in 2018.
Development and design During his premiership in the 1960s, Charles de Gaulle emphasized French autonomy from NATO and the Western Bloc, with a comprehensive military to maintain French sovereignty. A significant element of the doctrine was the development of a nuclear triad outside of American control, which became known as the . The seaborn leg of the triad required the domestic development of ballistic missile submarines, which became the main priority of the French Navy () for the next decade. The first series of French ballistic missile submarines were known as the .
The six Redoutable-class ballistic missile submarines measured long overall, with a beam of and a draught of . The boats displaced 7,500 tons surfaced and 9,000 tons submerged and carried a complement of 135. Propulsion was provided by a single-shaft nuclear power plant consisting of one pressurized water-cooled reactor, two steam turbines, two turbo-alternators, and one electric motor. This machinery produced and enabled a maximum speed of surfaced and submerged. Unlike earlier boats in the class, Le Tonnant was fitted with a metallic reactor core instead of an oxide core. An auxiliary diesel engine was carried onboard to get the submarines home if the reactor failed; the engine had a range of and an output of . Armament consisted of sixteen submarine-launched ballistic missile tubes and four bow-mounted torpedo tubes, with 18 torpedoes carried onboard. Sensors fitted included the DUVU-23 and DUUX-2 sonar systems, and the submarines could have a maximum depth of .
Service history Le Tonnant was the fifth of the class, and she was laid down at the Cherbourg Naval Base on October 1974, launched on 17 September 1977, and commissioned on 3 April 1980. She joined other members of the class and operated out of Île Longue in Brittany on patrols that lasted between two and three months. Two crews operated the boat in alternating patrols. The submarine was first deployed with the M2 ballistic missile, which was later replaced by the M20, and in turn the M4.
In the late 1990s, the was introduced to replace the Redoutable class on a one-to-one basis, although the last two Triomphant-class boats were cancelled. Le Tonnant was decommissioned in 1998 as the new boats began to enter service. The old submarine was laid up at Cherbourg and was dismantled between September 2018 and February 2020, the first of her class to have done so.
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