NOT KNOWN FACTS ABOUT APOLLO 3.5 BLUE PLUS PROCESSOR

The S-IVB also continued to thrust at a small level by venting gaseous hydrogen, to keep propellants settled inside their tanks and stop gaseous cavities from forming in propellant feed strains. This venting also taken care of safe pressures as liquid hydrogen boiled off while in the fuel tank. This venting thrust simply exceeded aerodynamic drag.[