Super-cold LOX gives advantages in performance for a rocket. But it isn't used in all rockets. SpaceX's Merlin 1D rocket engine uses super-cold LOX. Also NK-33 use sub-cooled LOX. Could super-cold LOX be used in every rocket engine? Does it needs modification with new parts or does it need a new design of the entire engine?

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    $\begingroup$ It'd take a fundamental redesign for use in the Space Shuttle SRB. ;) $\endgroup$ Commented Feb 25, 2017 at 16:35
  • $\begingroup$ Is there meant to be a distinction here between "subcooled" and "super-cold"? Subcooled seems to be an actual term used in spaceflight. $\endgroup$
    – uhoh
    Commented Feb 26, 2017 at 5:58
  • $\begingroup$ When Space-X talks about supercooled oxygen they mean it is just a few degrees above it's freezing point, as opposed to common LOX that is just under it's boiling point. $\endgroup$ Commented Feb 27, 2017 at 5:09
  • $\begingroup$ Afaik there is a difference between super-cold and supercooled, the latter being a term with specific definition of "under the freezing temperature but still not frozen" $\endgroup$
    – jkavalik
    Commented Mar 1, 2017 at 7:22
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    $\begingroup$ SpaceX is misusing the term 'supercooled' (as @jkavalik says, that means the liquid is below freezing point). Subcooled is the correct term. $\endgroup$
    – Hobbes
    Commented Mar 1, 2017 at 13:06

1 Answer 1


Short answer: No, lots of them don't use oxygen at any temperature or density

Long answer: Less no. If you take an engine that uses liquid oxygen and put subcooled liquid oxygen into it, it will be subject to additional thermal stresses and the turbopumps involved will be pumping a liquid denser than they were designed for. If neither of those problems destroy it or prevent it from starting, it will work but the turbopumps will almost certainly not be delivering the oxygen at the correct rate because of the increased density.

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    $\begingroup$ If the mixture gets too oxygen rich by using subcooled LOX, damages by excess oxidation of combustion chamber and nozzle are possible. $\endgroup$
    – Uwe
    Commented Mar 3, 2017 at 9:02
  • $\begingroup$ Good point. Hadn't thought of that one. $\endgroup$ Commented Mar 3, 2017 at 12:39

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