Device for modulating a gas ejection section

A rocket nozzle of variable throat section comprising a throat, a diverging portion, and a modulator device for modulating a gas ejection section, said modulator device being placed in the nozzle upstream from said throat, the modulator device comprising a partial shutter member for partially shutting the throat, a control guide for the partial shutter member, a main piston, and a primer piston, the control guide being movable between a retraction position in which the partial shutter member is held at a distance from the throat and a shutting position in which the partial shutter member is in contact with the throat;

• the primer piston being movable between a rest position in which the primer piston locks the main piston against moving, and a priming position in which the primer piston unlocks movement of the main piston, said primer piston moving from the rest position to the priming position when a pressure in the modulator device reaches a first predetermined value;
• and
• the main piston being movable between a first position in which movement of the control guide is locked in the retraction position, and a second position in which movement of the control guide is unlocked, the main piston moving from the first position to the second position when the primer piston is in the priming position and when the pressure in the modulator device reaches a second predetermined value less than the first predetermined value.