I'm trying to make a small Vacuum chamber for some hobby experiments to simulate high altitudes.. I really don't know that much about Vacuum physics so was hoping someone could comment. My idea is to get a vacuum pump and pump out a 55 gallon steel or plastic drum to 1/3 bar. My calculation is that the hoop stress, o=P*t/d If we have 1 bar on the outside and 1/3 bar on the inside, then we have P=2/3bar=67e3 Pa. The drums are 22.5 inches (.572 m) in diameter and 33.5 inches (.850 m) high. So if we assume the steel drum is A36 with yield stress of 250MPa then, 250e6=67e3*t/.572 -> t=2.13e3 m so min thickness is 2.13e3 m? I'm not sure how thick these steel drums are but after googling, http://www.skolnik.com/blog/steel-drums-thickness-can-preclude-re-use/ says drums could be .6mm (24 gauge). So that means crushing pressure=2.4e11 Pa = 240 000 bar? Something seems to be wrong with my calculations. Can someone comment if my sealed 55gallon steel drum would hold up to being pumped down to 1/3 bar? Also, I don't know much about vacuum pumps, can I find an appropriate pump cheap on ebay that I can run 24/7 and maintain a vacuum of 1/3 bar? Thanks in advance for all the help.