The S-IVB also ongoing to thrust at a lower level by venting gaseous hydrogen, to help keep propellants settled in their tanks and stop gaseous cavities from forming in propellant feed lines. This venting also taken care of safe pressures as liquid hydrogen boiled off during the gasoline tank. https://ultralowpowermcu32981.popup-blog.com/33019079/details-fiction-and-apollo-mcu