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French Start Next-Generation Ballistic Nuclear Missile Submarine Program

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French Minister for the Armed Forces Florence Parly last week announced the launch of the full-scale development phase of the SNLE 3G program, which calls for the construction of France’s third-generation nuclear-powered ballistic-missile submarines (SSBNs).

The Feb. 19 event took place at the French General Directorate of Armaments (DGA) hydrodynamics test center located in Val-de-Reuil, Normandy.

The 2019-2025 Military Plan Law, France’s military planning legislation, calls for the replacement of the four Le Triomphant-class SSBNs with four third-generation SSBNs (SNLE 3G) beginning in 2035. This is to ensure the continuity of France’s at-sea deterrence capability with a minimum of one SSBN on patrol at sea at all times.

The French Armed Forces and the DGA (Direction Générale de l’Armement, or the French Government Defense procurement and technology agency), which is responsible for overall project management, is conducting the SNLE 3G program. It is the subject of a framework agreement with the industry for the development, industrialization, logistics and production of the four SSBNs. Naval Group is the prime contractor for the overall manufacture of the submarines, in a joint venture with TechnicAtome, which is in charge of nuclear boilers construction.

The first contract, which will be awarded in 2021, covers the development studies until the end of 2025, the realization of the first elements of the hull and the boiler room of the first SNLE 3G, as well as the adaptation of the industrial manufacturing means of Naval Group for this program.

During her speech, Parly said that “the third-generation SSBN will be slightly longer and heavier compared to the Le Triomphant-class SSBN. It will hear better and defend itself better. It will be quieter: it will not be noisier than a shoal of shrimp, which is absolutely exceptional. It will be able to blend in perfectly with the ambient sounds of the sea, which is a guarantee of operational superiority.”

More than 200 companies from the French defense industrial and technological base will work with Naval Group to provide design or construction services for equipment and systems.

In the end, over the next 30 years, this program will represent up to 100 million hours of work, including 15 million hours of design and more than 80 million hours of construction.

At the Naval Group submarine shipyard in Cherbourg, more than 300 employees work in design activities and construction represents more than 2,000 employees. The teams in Cherbourg will build the platform – hull, structure and part of the internal modules – integrate the equipment and systems into the platform, and carry out the commissioning and testing of the submarine’s facilities.

As part of the SNLE 3G program, the DGA has signed a memorandum of understanding with Thales for the development of a complete sonar suite, including a broad range of sonar arrays and associated processing systems.

Thales will provide new-generation flank arrays and bow-mounted sonars, a towed linear array based on optical technology (ALRO), and all the other equipment making up the sonar suite (intercept arrays, echo-sounders, underwater telephones).

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The ALICIA sensor data processing system (Analyse, Localisation, Identification, Classification Intégrées et Alertes), with a user interface designed to handle the diversity and volume of available data, will optimize operator workload and provide decision support.

The new sonar suite will be deployed incrementally, with the first technological building blocks and system versions due to be installed on second-generation SSBNs (SNLE 2G) starting in 2025, and on the third-generation submarines (SNLE 3G) starting in 2035.

TechnicAtome is in charge of the design, construction and commissioning of the nuclear propulsion reactor, in partnership with Naval Group, which has overall responsibility for the vessels.

According to the company, the design of the reactor for the third-generation SSBN benefits from 50-plus years of know-how in compact reactors with the permanent integration of innovations to increase the military performance of the reactor, its availability, the energy capacity of its core and nuclear safety guarantees. In this respect, the nuclear propulsion reactor of the SNLE 3G program is a link between the lower-power reactor of the Barracuda-class submarine and the reactor of the future PANG aircraft carrier. Known as K22, this reactor will deliver significantly higher power. Their design studies have just started following the December 8, 2020 decision of French President Emmanuel Macron.

The overall design of SNLE 3G seems to be an evolution of the SNLE 2G (Le Triomphant-class SSBNs) rather than a revolution. Like its predecessor, it features a sail cusp: a single-piece composite fairing structure attached to the submarine sail and hull. It improves hydrodynamic performance by allowing smooth laminar flow of water over its surface. It also features a pump-jet. The stern arrangement is reminiscent of the Suffren-class SSN (X-rudder configuration) but incorporates a centerline fin for a towed array. According to the artist’s impression, the hull of SNLE 3G is entirely covered with anechoic tiles. The current class of French SSBNs have tiles too, but only in a few key areas of the hull. Anechoic tiles are rubber or synthetic polymer tiles, which help absorb the sound waves of active sonar as well as the lower sounds emitted from the submarine itself.

According to submarine expert H I Sutton, the bow arrangement, with the entire nose dedicated to a sonar dome, implies a very large spherical sonar array. This is similar to the Le Triomphant-class. The design only shows four torpedo tubes, mounted behind the sonar dome. These must be angled outwards to go around it, which may limit the speeds at which torpedoes can be launched.

Talking to Naval News during the event, the French Navy’s (Marine Nationale) SNLE 3G program officer explained that the future SSBNs will be equipped to cope with the threats from 2035 and beyond, especially in the field of sonar detection.

SNLE 3G by the numbers

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Length: About 150 meters
Displacement: 15,000 tons (submerged)
Crew complement: About 100 sailors


  • 16x modernized M51 SLBM(likely known as M51.4)
  • 4x torpedo tubes for F21 heavyweight torpedo and probably the FCASW (Future Cruise and Anti-Ship Weapon)

First steel cut: 2023
Delivery of first-in-class SSBN to French Navy: 2035
Out of service year (for the class): 2090