The Vulcain is a gas generator liquid oxygen / liquid hydrogen booster engine which powers the Ariane 5 cryogenic core stage.  The Vulcain development program began in 1988 with engine tests commencing in April of 1990 and final qualification occuring by the end of 1994.  SEP has already started work on the Vulcain 2 as part of the Ariane 5 performance improvement program.  The Vulcain 2 will operate at a higher mixture ratio to produce more thrust and use a larger area ratio to improve engine efficiency (higher Isp).

In the Ariane 5 mission sequence, the Vulcain engine is ignited prior to liftoff and burns for 585 seconds, generating 256,000 lb of thrust and providing the bulk of the Ariane 5's velocity change. The Vulcain is fully gimballed to provide thrust vector steering.