A nozzle (1) for a space vehicle engine (M), the nozzle comprising a stationary portion (2) and a movable portion (3), the nozzle (1) including a pneumatic deployment system (4) comprising: a deployment actuator (5) for deploying the movable portion (3) of the nozzle (1); a high unlocking actuator (6); a low unlocking actuator (7); and an ejector (41); the deployment system (4) including a feed system (8) configured so as to, sequentially: move the deployment actuator (5) from its support position towards its deployment position; move the high and low unlocking actuators (6, 7) into their high and low unlocking positions; and actuate the ejector so as to eject the deployment system (4) from the nozzle (1).