The fourth Barracuda type nuclear-powered attack submarine (SSN) for the French Navy (Marine Nationale) started its initial sea trials.
Fourth Suffren-class SSN, “De Grasse” (S638), begins maiden sea trials.
The De Grasse (S638) is the fourth Suffren-class SSN. The first sea trials, also known as “Alpha Trials”, was conducted off the Naval Group submarine shipyard of Cherbourg in Normandy, with the submarine setting sails 24 February 2024.
The submarine is named after Lieutenant général des armées navales François Joseph Paul, Comte de Grasse, Marquis of Grasse-Tilly, a French naval officer. The Comte de Grasse is best known for his crucial victory over the Royal Navy at the Battle of the Chesapeake in 1781 during the American Revolutionary War.
In a recent interview with Naval News, Admiral Xavier Petit, Commander, French submarine forces (ALFOST) explained that De Grasse features some improvements compared to the first three boats in the class: Among them are a new version of the submarine’s combat management system (known as SYCOBS – this new SYCOBS version brings new features to the CMS) and a new generation electronic warfare system.
Fourth Suffren-class SSN “De Grasse” starting sea trials (Credit: Naval Group)
A press release shared by Naval Group reads:
The first sea trial of the SSN De Grasse follows the dock tests carried out since the launch of the submarine in May 2025, as well as the commissioning of its nuclear reactor in December 2025. The operations successively took place in the assembly hall as well as in the dry and water-filled docks to test equipment and systems.
This new milestone marks an important step in the realization of the Barracuda program for which the first three SSNs have already been admitted to active duty (SSN Suffren in June 2022, SSN Duguay-Trouin in April 2024 and SSN Tourville in July 2025). The last two submarines of the program (SSN Rubis and SSN Casabianca) are currently under construction, at different stages of completion, and their deliveries will be staggered until the end of the decade.
Designed to meet the operational needs of today and tomorrow, the Barracuda-class SSNs are more versatile, higher performing and better armed than their predecessors. Among the world’s stealthiest submarines, they provide the French Navy with a real superiority in combat, notably thanks to MBDA’s naval cruise missiles (NCM) which provide them with a precise deep-strike capability. They are also equipped with the F21 heavyweight torpedo produced by Naval Group and the SM39 anti-ship missile from MBDA. These SSNs are also equipped with enhanced capabilities for discrete deployment of Special Forces underwater.
De Grasse starting sea trials (Credit: Naval Group)
First submarine of the class, Suffren, was delivered in November 2020. It entered “active duty” in June 2022 and completed its first operational deployment in January 2023. The second boat-in-class Duguay-Trouin was delivered in August 2023 and was commissioned in April 2024. The third Suffren-class submarine, Tourville, was delivered in November 2024 and was commissioned in July 2025.
Two SSNs of the class remain to be launched. Naval News understands that Rubis is set to begin sea trials next year while the final boat of the class, Casabianca, could be handed over to the French Navy in 2029 (which would be a year ahead of schedule compared to the initial contractual date).
Suffren-class submarines in numbers:
- Surface displacement: 4,700 tons
- Diving displacement: 5,100 tons
- Length: 99 meters
- Diameter: 8.8 meters
- Maximum depth: > 350 meters
- Speed: > 25 knots
- Armament: naval cruise missiles, F21 heavy-weight wire-guided torpedoes, modernized Exocet SM39 anti-ship missiles, FG-29 mines, D-19 UUV (future development)
- Hybrid propulsion: pressurized water reactor (150MW) derived from the reactors on board the Triomphant-class SSBN and Charles-de-Gaulle aircraft carrier, one propulsion turbine, two turbo generators and two electric motors
- Crew: 63 crew members + approx. 15 commandos
- Endurance: 70 days at sea (or until food supplies run out)
- Availability: > 270 days per year.
Innovation for naval combat
Suffren-class SSNs are equipped with numerous innovations that allow them to demonstrate differentiating capabilities in many areas. The French Navy’s new class of submarines is able to strike deep behind enemy line all while remaining stealthy thanks to the torpedo tube-launched naval cruise missile (MdCN). The integration of state-of-the-art sensors also gives it superior anti-submarine warfare and intelligence, surveillance, reconnaissance (ISR) capabilities. The non-penetrating optronic masts (by Safran Electronic and Defense) are a disruptive technology. They bring unmatched high quality (4K) imagery and every sailor in the CIC can access them. Finally, these submarines comes with systems that facilitate the deployment of naval special forces. In particular, the Dry Deck Shelter, a removable deck hangar, allows the deployment of the new PSM3G swimmer delivery vehicle (SDV) and a dozen combat swimmers.