French submarine Gymnote (S655)

Gymnote (S655) was an experimental submarine of the French Navy. She was a trials submarine for Submarine-launched ballistic missiles and powered by diesel electric engines. She is named in honour of the Gymnote, the world's first all-electric submarine built in France in the late 19th century.

The French planned a nuclear propelled submarine in the late 1950s and laid down a hull (no Q244). Because France had not developed uranium enrichment facilities at the time, the planned power plant was to be a heavy water reactor, which could utilize natural uranium. But French engineers were unable to produce a reactor small enough to fit into the submarine, which led to the project being canceled in 1959.

In the early 1960s the French government decided to develop an independent nuclear deterrent based on SLBM's. Hull Q244 was redesigned as a trials submarine with four missile tubes in an extended casing. The Gymnote was commissioned in 1966 and fired the first M-1 Missile in 1968. The M-1 Missile was subsequently deployed aboard the Redoutable class submarines. She was extensively rebuilt in 1977-79 to enable trials of the new M-4 Missile. The Gymnote was decommissioned in 1986.