France Launches SyLEx Sounding Rocket Carrying Experiments for Its Next M51.4 Nuclear Missile

France’s defense procurement agency launched an ArianeGroup SyLEx sounding rocket from Biscarrosse overnight on November 3–4, carrying experiments for the payload of the future M51.4 submarine-launched ballistic missile. The single-stage, solid-propellant Block 1 rocket followed a trajectory outside the atmosphere and is designed to carry up to 300 kilograms of experiments. The mission was the second SyLEx flight and the first to carry a French government payload, following ArianeGroup’s November 2025 demonstration. The November flight followed a separate October 2026 acceptance firing of an unarmed M51.3 missile from the submarine Le Vigilant.