Abstract: The casing comprises a combustion chamber and a nozzle, consisting of a subsonic and a supersonic sections with an external structural envelope and a fire wall having a ribbed external surface. The regenerative cooling passage is formed between the envelope and the fire wall. The fire wall is made from copper or a copper alloy, and the external structural envelope is made from steel or a nickel alloy. The fire wall has a metal coating stratified in the region of the nozzle throat over a length of not less than 0.3 diameter of the nozzle throat in the longitudinal direction. The first layer of the coating is nickel 50 &mgr;m to 1000 &mgr;m thick, and the second layer is chromium 10 &mgr;m to 500 &mgr;m thick.