Le Vigilant

History

Le Vigilant (S618) is the third of four Triomphant-class nuclear-powered ballistic missile submarines built for the French Navy by Naval Group. The keel was laid in 1997, and the submarine was launched on 19 September 2003. It was commissioned into active service on 26 November 2004 and is based at Île Longue near Brest. The estimated acquisition cost was 4.282 billion euros (2010 values).

On 6 October 2026, Le Vigilant conducted the first M51.3 ballistic missile launch from a nuclear submarine. The acceptance test, carried out under Operation SMERTRIOS off the coast of Finistère without a nuclear warhead, validated the submarine's strategic weapon system following a maintenance and modernization period exceeding 18 months. The firing confirmed the vessel's readiness to resume its role in France's operational deterrence cycle.

Design

Le Vigilant displaces approximately 14,200 tonnes submerged. The hull is 138 m long with a beam of 12.50 m and a draught of 10.60 m. The submarine achieves speeds over 25 knots and can operate at test depths exceeding 400 m. Nuclear propulsion provides an unlimited operating range and a design service life of 20 to 25 years without conventional refuelling constraints.

The missile compartment carries 16 M51 submarine-launched ballistic missiles. The M51 is a three-stage solid-propellant missile with a mass of approximately 54 tonnes and an intercontinental range approaching 10,000 km depending on warhead configuration. Its guidance architecture includes stellar position updating to maintain accuracy during flight. The current M51.3 variant, which entered operational service on 24 October 2025, introduces the TNO-2 oceanic nuclear warhead and improves range, accuracy, and penetration performance over earlier M51 configurations.

Operational history

Le Vigilant serves in the Force océanique stratégique (FOST), France's strategic oceanic force, alongside the other three Triomphant-class submarines: Le Triomphant, Le Téméraire, and Le Terrible. The four vessels rotate between at-sea deterrent patrols, training, and maintenance periods to maintain a continuous French nuclear presence at sea.

The 6 October 2026 M51.3 acceptance launch followed an extended IPER (periodic maintenance and repair overhaul) in Brest. The missile was tracked throughout its flight by assets of the DGA missile test branch, including the instrumentation ship Monge, to a designated impact area in the North Atlantic. The French Ministry of the Armed Forces confirmed the successful firing validated the submarine's full operational capability for the strategic mission. Development of the successor M51.4 variant began in 2025 under a contract awarded to ArianeGroup, the prime contractor for the M51 system.

Operators

• France – 1 submarine in active service with the Force océanique stratégique

Specifications (Le Vigilant, S618)

General characteristics

• Class and type: Triomphant-class ballistic missile submarine
• Displacement (submerged): approximately 14,200 t
• Length: 138 m
• Beam: 12.50 m
• Draught: 10.60 m
• Test depth: over 400 m

Performance

• Speed: over 25 kn
• Range: unlimited; design life 20–25 years
• Propulsion: nuclear

Armament

• Ballistic missiles: 16 × M51
• Electronic warfare and decoys: ARUR 13 system