# How does the Blackbird SR-71 pressurize the cockpit at Mach 3?

I'd assume the Blackbird's engine that converted into a ramjet once at supersonic speed had no moving parts at ramjet phase. If the engines were off, how then did it pressurize the cockpit at cruise altitude to ensure pilot safety and that he/she did not pass out from lack of oxygen?

• @securitydude5 does a ramjet have moving parts? is a separate question, and one which can be easily answered by reading the wiki article on ramjets. – 0xdd May 18 '18 at 20:06