5,200-Ton Hunter-Killer Submarine ‘Rubis’ Built For French Navy Rolls Off The Production Line

The fifth of the six Suffren-class nuclear attack submarines is ready to be fitted out and undergo trials. Built for the French Navy by Naval Group, the Rubis, or S639, is the latest addition to the fleet and is set to replace the Rubis-class, which has remained in service since the 1980s.

The 99-metre-long sub left the construction yard on October 16, 2026, in Cherbourg. Its main superstructure is almost complete, with only a few touches remaining, after which it can go for further systems integration and fitting of combat and electrical equipment.

The submarine would begin its sea trials next year, though no official dates have been announced yet. If Rubio clears the trials, she would enter the French submarine fleet as its latest addition. The sixth Suffren-class submarine, the Casablanca, would be built over the coming years.

Developed under the Barracuda Program, the Suffren-class submarines are an upgrade over the Rubio-class and enable the French Navy to maintain its undersea warfare capabilities until the middle of the century.

What differentiates the Suffren-class submarines is their X-shaped rear rudder, their control system, and pump-jet propulsion system. The new subs also reduce noise while operating and have greater stealth features, which make them difficult to identify and track.

With only the last unit of the new class remaining, the older submarines will be replaced entirely by the end of this decade, if everything goes as planned. The Suffren-class of subs has a water reactor derived from the Le Triomphant-class SSBNs and the Charles de Gaulle aircraft carrier.

The submarines would have a speed of 23-25 knots and an unlimited operational range, with the constraint being food supplies, which need to be restocked every 70 days. They would have a crew of 60 to 65 personnel.

Coming to the armament and payload, the submarines have four torpedo tubes measuring 533 mm with 20 storage slots.

They support weapons including F21 heavyweight torpedoes, MdCN land-attack cruise missiles, Exocet SM.39 Block 2 anti-ship missiles, and FG29 naval mines.

The submarines have a dry deck shelter and a mobile docking capsule interface to deploy commandos and unmanned undersea vehicles.

SSNs like these are built for at-sea combat, surveillance, intelligence gathering, and to act as a deterrent. Some have land-attack capabilities and can be utilised in special missions which require stealth, such as delivering combat divers to disputed or conflict-prone waters.

The French Navy plans to modernise the Suffren-class periodically over its lifespan rather than allowing it to become technologically obsolete.