Abstract: The present invention relates to a shut-off system for an orifice for introducing combustion air into a ramjet with a consumable auxiliary motor (14).According to the invention, this shut-off system comprises:an elastic system (28, 29, 31, 32) connected to the shut-off flap (20A, 20B); anda retaining element (33) for keeping the said elastic system in the said tense state during the initial phase of rocket operation, the said retaining element being sensitive to the hot gases emitted by the said consumable auxiliary motor (14) so that on completion of combustion thereof, the said retaining element (33) releases the said elastic system which spontaneously changes from its tense state to its relaxed state, bringing the said flap from its shut-off position to its open position.

Abstract: The combustion chamber of the ramjet is mounted on a support which allows partial freedom of longitudinal movement. A nozzle is arranged at the intake of the combustion chamber, with a flexible, fluid-filled bladder being disposed between the nozzle and the combustion chamber. Air is blown into the combustion chamber through the nozzle, and fuel is fed into the combustion chamber to achieve combustion. The pressure of the fluid in the bladder is measured.