Rev 2 of the stressed skin approach to the bulkhead. Holes are added to the PMMA disk, and covers are added over the holes. Each cover is 1.495″ in diameter, to fit through the 1.6″ diameter throat.
Material is changed to 7075-T6 for the aluminum parts to increase the FOS. Contours are simplified to make machining simpler. Top and bottom of sandwich are now identical parts.
The holes through the PMMA are 1.3″ in diameter. This give a full area just under 4 square inches, compared to 2 square inches for the nozzle throat. This should ensure that there is no sonic lock in the flow as it goes through the delay disk. Having sonic flow into the aft chamber would result in a large increase in heat flux into the walls of the chamber, and should be avoided if at all possible.