An apparatus has a container with a cavity containing a medium, and the container is sealed with a membrane that ruptures at a rupture pressure. A pressurizer pressurizes the cavity to at least the rupture pressure, and a projectile is disposed externally to the cavity during the pressurization. The projectile is propelled by the medium following rupture of the membrane. Preferred containers include pressurized cylinders, gun barrels, and ammunition cartridges, and preferred media include air, pressurized air and explosives, and a particularly preferred apparatus is a toy rocket launcher.