SyLEx Rocket Completes First Operational Flight for M51.4 Missile

A flying test bench for the M51.4

The experiments support development of the M51.4, a future nuclear missile entrusted to ArianeGroup in September 2025. It is meant to gain range, accuracy and the ability to penetrate enemy defences, and is expected to enter service during the next decade. The DGA used radars and measurement assets at Biscarrosse and Hourtin, plus the test and measurement ship Monge, to track the flight. Armed Forces Minister Catherine Vautrin said the launch allowed "new experiments essential to the development of the M51.4".

The flight came less than a month after the 6 October firing of an M51.3 missile from the submarine Le Vigilant.

Civil uses and sovereignty

SyLEx, short for Système de Lancement d'Expériences, flew in its single-stage version. A two-stage version is in preparation, with a first flight planned by 2027. ArianeGroup quotes altitudes of 140 to 400 km depending on the version, and payloads of up to 300 kg with one stage or 600 kg with two.

The rocket is also aimed at civil, notably European, customers for microgravity experiments, with 4 to 5 minutes with one stage and more than 6 with two, as well as atmospheric reentry tests. Developed in under three years, it restores a French suborbital capability the country had lacked for decades. France even relied on an American rocket for the June 2023 first flight of its V-MaX hypersonic glider.