A nozzle for a space vehicle engine, the nozzle comprising a stationary portion that is stationary relative to the engine, and a movable portion that is movable relative to said stationary portion, the stationary portion presenting a free end, the movable portion presenting a proximal end and a distal end, the free end of the stationary portion and the proximal end of the movable portion being adapted to be locked together by engagement, the nozzle having a pneumatic deployment system for deploying the movable portion and arranged in the stationary portion of the nozzle, the pneumatic deployment system comprising: • a deployment actuator adapted to move from a support position in which the movable portion of the nozzle is retracted over the stationary portion of the nozzle, and a deployed position in which the proximal end of the movable portion of the nozzle is engaged with the stationary portion of the nozzle; • a high unlocking actuator adapted to move from a high locking position in which it holds the deployment system in the stationary portion of the nozzle to a high unlocking position in which it disengages the deployment system of the nozzle from the stationary portion of the nozzle; • a low unlocking actuator adapted to move from a low locking position in which it locks the deployment system to the movable portion, and a low unlocking position in which it disengages the deployment system of the nozzle from the movable portion of the nozzle; and • an ejector adapted to exert a thrust force tending to eject the deployment system from the nozzle; and • a pneumatic pressure feed system for actuating the deployment actuator, the high unlocking actuator, and the low unlocking actuator, and the ejector, said feed system being configured in such a manner as to, sequentially: • move the deployment actuator 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 from the nozzle. • a deployment actuator adapted to move from a support position in which the movable portion of the nozzle is retracted over the stationary portion of the nozzle, and a deployed position in which the proximal end of the movable portion of the nozzle is engaged with the stationary portion of the nozzle; • a high unlocking actuator adapted to move from a high locking position in which it holds the deployment system in the stationary portion of the nozzle to a high unlocking position in which it disengages the deployment system of the nozzle from the stationary portion of the nozzle; • a low unlocking actuator adapted to move from a low locking position in which it locks the deployment system to the movable portion, and a low unlocking position in which it disengages the deployment system of the nozzle from the movable portion of the nozzle; and • an ejector adapted to exert a thrust force tending to eject the deployment system from the nozzle; and • a pneumatic pressure feed system for actuating the deployment actuator, the high unlocking actuator, and the low unlocking actuator, and the ejector, said feed system being configured in such a manner as to, sequentially: • move the deployment actuator 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 from the nozzle.