H I Sutton story with additional reporting by Xavier Vavasseur.
Submarines thrive on stealth, especially those carry a country’s nuclear deterrence. They do not want to be heard and tracked using sonar, which is why modern nuclear submarines are built to be extremely quiet. But as adversaries get ever better at detecting them, newer submarines have to be even quieter. In an exclusive interview with Naval News, the French Navy (Marine Nationale) officer in charge of the program explained that:
“The submarine will be so quiet that its radiated noise may be less than the ambient noise in the ocean”.
SNLE-3G Program Officer, French Navy
Together with a massive leap in its own sonar and non-acoustic sensors, this should maintain survivability against future foes. “This is key because they are expected to serve from 2035 until the latter part of the century” the officer explained.
Full scale development of the new submarine, known as SNLE-3G (Sous-marin nucléaire lanceur d’engins – 3rd generation), was launched by the French Minister for the Armed Forces, Florence Parly, on February 19. The new class, which has not yet received a ship name, will replace the current Le Triomphant-class nuclear-powered ballistic missile submarines (SSBN). Like the current boats the new submarines will be built by Naval Group.
At first glance the new submarine is similar in size and form to the current Le Triomphant-class. But it is an entirely new design and is actually almost 10 meters (30 ft) longer. The main driver for this increased size is stealth. The machinery space will be longer to incorporate an even quieter machinery. This may have some technologies already found on France’s latest nuclear submarine, the Suffren-class attack submarine. Outwardly these include the X-form rudders and pumpjet propulsor.
But between the two upper rudders is a difference from the Suffren. A small fin contains a next-generation towed sonar array known as ALRO. This will use optical technology. While this array may in itself be a capability leap, the most important aspect is that it is part of a holistic sensor suite known as ALICIA.
Thales’ ALICIA (Analyse, Localisation, Identification, Classification Intégrées et Alertes) combines a wide range of sensors into the SYCOBS 3.0 data processing system. These include large new flank array sonars and a new bow sonar. The exact technology in the bow sonar has not been reported but Naval News believes that it will have moved beyond traditional cylindrical arrays.
ALICIA will be capable of Ultra-Low Frequency (ULF) detection meaning that even the quietest adversaries may be tracked and identified. “The challenge will be processing the massive amounts of data gathered by the new sensors. The data is expected to be an order of magnitude more than on current boats” the SNLE-3G Program Officer told us. However artificial intelligence will help the crew identify contacts, greatly aiding their work. This will help with both technical and tactical classification. The latter can be based on intelligence which usually leads to a decision from the submarine commander.
Other updates include an upgraded reactor based on the proven K15 family. This will have improved safety features to keep pace with expected standards and more power.
Naturally the crew will be mixed gender. Because the submarine is being designed from outset for mixed crews the additional hygiene facilities can be designed in. This is much cheaper and better than the modernizations which can be required on legacy subs.
Last but not least, asked to comment on the main differences between Le Triomphant-class and SNLE-3G, the Program Officer told Naval News:
“One important factor in designing SNLE-3G is the heritage. We take possession of the best of what our elders did, we modernize it and digitize it. SNLE-3G main difference will be its unique processing power and an incremental combat system which will be future proof and batch-upgradable throughout the life of the submarine. Each new batch will learn from the previous batches. This is SYCOBS 3.0, the future combat management system of SNLEG-3G, under development by Naval Group. SNLE3G is being designed to face and survive the future threats likely to emerge after 2035.”
This new generation of ballistic missile submarines will preserve France’s strategic deterrent. The new technologies involved are challenging but the gains could be massive.