Consumable port cover for ducted integral rocket-ramjet engine

In an integral rocket-ramjet engine comprising an engine casing provided with at least one air inlet at one end thereof and an exhaust outlet at the other end, at least one intake duct operably connected to said air inlet and extending forward of the combustion chamber defined by said casing for supplying ram air to said combustion chamber, means for supplying ramjet fuel to said combustion chamber, a rocket motor positioned within said combustion chamber, a removable port cover for covering each of said air inlets for preventing backflow of booster gases prior to substantial completion of rocket motor burn and allowing ingress of ram air at the substantial completion of said rocket motor burn, the improvement wherein said port cover is a laminate material consisting of alternating plies of Pd and Al in approximately equimolar quantities, having at least 6 Pd—Al interfaces, with Pd on the outside faces, wherein said port cover has a thickness in the approximate range of 0.020 inch to 0.100 inch, and wherein said port cover has a plurality of ignition tabs attached thereto, said ignition tabs extending into said rocket motor.