Abstract: Blanking-cap system for an orifice of a duct, in particular for an orifice of an air-intake duct into the combustion chamber of a ramjet. The blanking-cap system (16) includes a glass blanking cap (15) and a destruction device (17) which comprises a projectile (18) capable of destroying the blanking cap (15), and a controllable projection means (19), which is capable of projecting the said projectile (18) and which is arranged outside the conduit (7) while being oriented in such a way as to be able to project the said projectile (18) onto the said blanking cap (15).