Originally Posted by
B Fraser
The fuel in the tanks will need to slosh to the bottom of those tanks so the engines are not chewing on vapour at the re-light, otherwise, it gets very exciting very quickly and very briefly.
Not necessarily - at least if the vapor is 'designed for'. The early Saturn V's had so-called 'ullage motors' to get the fuel to the tank fuel outlets for staging and in-flight restarts. However they gradually discovered the ullage motors were not really needed and got rid of them.