Of the potential volume of a liquid fueled rocket's propellant tank, how much of that volume is actually dedicated to propellants (since ullage is needed because of pressurization, boiloff, etc.)?

Particularly, I'm looking for this measure with respect to the following fuels

  • RP-1,
  • LOX, and
  • LH2 fuels.

Note the gaseous hydrogen in the Ariane 5 EPC: that's the ullage space I'm asking about.


1 Answer 1


This report has the ullage volume of the LOX tank on the X-34 at 6%, and RP-1 at 0.5 to 1.5%.


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