CMS Propellant Tank Bulkheads

The bulkheads of our tanks were some of the most complex parts on the entire rocket. We have 3 bulkheads: upper, common, and lower. They were 6.625” in diameter and made from 6061 aluminum. The first operations were done on a lathe, which cut the OD of the part. The rest of the operations, including boring out the bowls themselves, were done on a 5-axis CNC mill. A ballnose endmill gave us a much better surface finish on the bowl than the boring bars available at BIDC. The top parts of the bulkheads required simultaneous 5-axis machining to get the required features. While this added complexity to the toolpaths, the machine was more than capable of running them and gave very good results. Custom soft jaws were made to ensure the 1/8” thick bulkheads would not be crushed by the clamping force. I also had to get creative in how to clock the upper bulkhead, as it had a post in the bowl that needed to be aligned to the top of the bulkhead. I was able to use some drills, a parallel, and a dial indicator to align the part rotationally to ensure all features lined up as they should. After the bulkheads were complete, they were sent off along with some aluminum tube sections to be welded together. The tanks then passed proof testing and all subsequent coldflows and hotfires.