The S-IVB also ongoing to thrust at a lower level by venting gaseous hydrogen, to help keep propellants settled of their tanks and prevent gaseous cavities from forming in propellant feed strains. This venting also maintained safe pressures as liquid hydrogen boiled off while in the fuel tank. This https://collinqpmjf.blogdosaga.com/32658055/detailed-notes-on-apollo-4-plus