portion 17 towards the lower portion 16 upon impact of rocket motor exhaust gas 45 directed thereon as shown in fig5 b the plugs 55 a 55 b may incorporate a tapered shape or alternatively may comprise a stepped shape not shown while these two shapes configurations are described with respect to the plugs 55 a 55 b the embodiments herein are not restricted to a particular geometric configuration of the plugs 55 a 55 b as any type of configuration that permits breach of the plugs 55 a 55 b is permitted additionally the system 10 a further includes a layer of meltable material 60 over the upper portion 17 of the plenum 15 and a layer of fire resistant material 65 under the layer of meltable material 60 in one embodiment the material used for the layer of fire resistant material 65 is the same material used for the plugs 55 a 55 b thus the plugs 55 a 55 b are fire resistant and the release of the plug 55 a is dictated by the force of the exhaust gas 45 rather than the heat generated by the gas 45 the layer of fire resistant material 65 may be configured to be substantially aligned with the plugs 55 a 55 b due to the fire resistant qualities of the plugs 55 a 55 b the floor 16 of the plenum 15 is protected from the deleterious effects of the gas 45 without the need of a gas blast protector 30 additionally once.