French submarine Nautilus (1930)

The French submarine Nautilus was a Saphir-class submarine built for the French Navy in the mid-1930s. Laid down in August 1927, it was launched in March 1930 and commissioned in July 1931. Nautilus was disarmed at Bizerte, Tunisia and captured there on 8 December 1942 by Italian forces. On 31 January 1943, it was sunk at Bizerte during an Allied air raid. Nautilus was raised but not repaired and finally stricken on 12 August 1947.

Design
66 m long, with a beam of 7.1 m and a draught of 4.3 m, Saphir-class submarines could dive up to 80 m. The submarine had a surfaced displacement of 761 LT and a submerged displacement of 925 LT. Propulsion while surfaced was provided by two 1300 hp Normand-Vickers diesel motors and while submerged two 1100 hp electric motors. The submarines electrical propulsion allowed it to attain speeds of 9 kn while submerged. Their surfaced range was 7000 nmi at 7.5 kn, and 4000 nmi at 12 kn, with a submerged range of 80 nmi at 4 kn.

The Saphir-class submarines were constructed to be able to launch torpedoes and lay mines without surfacing. The moored contact mines they used contained 220 kg of TNT and operated at up to 200 m of depth. They were attached to the submarine's exterior under a hydrodynamic protection and were jettisoned with compressed air. The Saphir-class submarines also featured an automatic depth regulator that automatically flooded ballast tanks after mines were dropped to prevent the risk of the submarine surfacing in the middle of enemy waters.