The images below are from the Astronautix page. THe first one shows both fuel (kerosene) and oxidizer tanks (50:50 N2O4, NHO3) about two-thirds full, with (presumably sliding) bulkheads separating the liquid from 600 PSI gas, labeled as ullage.
- Do the ullage bulkheads really slide? If so, how do they work? O-rings?
- Why is there an additional "intermediate bulkhead" in the middle of the liquid oxidizer? What is it for, how does it work?