Rubis class

   In 1964 the French Navy began the design of a 4 000-ton nuclear-powered attack submarine. This was cancelled in 1968, before construction started. A smaller design was then initiated, based on the hull form of the diesel-electric Agosta class and with basically the same fire-control, torpedo-launching and sonar detection systems.

   The resulting SNA72 class built at Cherbourg is the smallest SSN type in operational service with any navy, and was made possible by the French development of a small 48-megawatt integrated reactor-heat exchanger system driving two turbo-alternators and a main electric motor. The hull depth was increased compared with the Agosta class, and has allowed the typical three-deck layout of larger SSNs to be used for the areas forward and immediately aft of the fin. The forward diving planes of the Agostas have been relocated to the fin to improve underwater maneuverability.

   The first boat, the Rubis, was laid down at Cherbourg in 1976, and was commissioned in February 1983. It was followed by three further boats, the Saphir, the Casabianca, and the Emeraude, which were commissioned between 1984 and 1987. All submarines, except the Casabianca, are named after gemstones.

   The French Navy had originally planned for two squadrons of these SSNs, one to be based at Brest to cover the SSBN base, and the other at Taulon. In the event, all of the boats are based at Taulon, together with the two boats of the follow-on Amethyste class. All, however, operate frequently in the Atlantic.

   Originally, the Rubis class were tasked primarily with anti-surface warfare. Endurance, limited primarily by the amount of food which can be carried, is estimated at 45 days.

   All of the boats carry versions of the F 17 and L5 torpedoes and, from the middle of the 1980s, have been equipped with the underwater-launched, encapsulated SM.39 Exocet anti-ship missile.

   However, in the early 1990s, they were joined by two improved boats, the Amethyste and the Perle. Built to the same basic design, but stretched by about two meters, the new boats were designed primarily as anti-submarine platforms. They have a more advanced sonar and electronic fit, and are quieter than the original boats.

   Between 1989 and 1995 the early boats underwent the AMETHYSTE modernization programme. Standing for AMElioration Tactique HYdrodynamique Silence Transmission Ecoute it brings them up to the standard of their successors. The programme included upgrades to the sonar, reshaping of the hull form and bow to improve silencing. Additional upgrades were made to electronics.

   A new, larger class of SSN is currently in development, and is expected to enter service some time after 2010.