We know that oxygen is the "king" of oxidizers:

  • non-toxic (unlike fluorine)
  • cheap
  • only an oxidizer (potassium nitrate, for example, comes with K and N which aren't what we want)
  • no need for catalysis ($H_2O_2$)

But with all that being said, we still have to contain it inside a very cold tank (90K) or a very pressurized one (so very heavy…).

With all that in mind, would it be a good idea to use nitrogen dioxide ($NO_2$) and/or dinitrogen tetroxide($N_2O_4$) to stabilize the $O_2$? (I mean raising its boiling point.) It would reduce the need for cooling machines (not cheap) while letting the mix be a good oxidizer.

EDIT 1 : As Organic Marble pointed out it seems that $N_2O_4$ could replace $NO_2$ in the question. But because $NO_2$ and $N_2O_4$ are always in chemical equilibrium, filling a tank with one of them is, I guess, filling it with both of them ?

And if any of you think of another good oxidizer that would do the trick, feel free to share the idea!

  • 1
    $\begingroup$ +Nathan Tuggy Thank you for the correction :) $\endgroup$
    – YaJBoy
    Sep 24, 2016 at 22:55
  • $\begingroup$ Interesting question. My usual sources make no mention of it being used as rocket oxidizer, although an Air Liquide fact sheet lists it as a use. It seems to be quite toxic but that hasn't prevented the use of other propellants. $\endgroup$ Sep 25, 2016 at 2:09
  • $\begingroup$ @OrganicMarble wikipedia says " it was used in the Titan rockets, to launch Project Gemini, in the maneuvering thrusters of the Space Shuttle, and in unmanned space probes sent to various planets" (en.wikipedia.org/wiki/Nitrogen_dioxide#Uses) $\endgroup$
    – YaJBoy
    Sep 25, 2016 at 6:08
  • 1
    $\begingroup$ No, that is nitrogen tetroxide, a different compound. Is that what you are really asking about? $\endgroup$ Sep 25, 2016 at 13:29
  • $\begingroup$ @OrganicMarble It is said in this page that nitrogen tetroxide stay in an "equilibrium mixture" with $NO_2$. So I didn't made the distinction. it's (I think) the same question ... no? $\endgroup$
    – YaJBoy
    Sep 25, 2016 at 14:55

1 Answer 1


If you want to mix LOX with other gases, those gases should be liquid at the temperature of LOX. But NO2 is solid at only -11.2 °C and N2O4 at -11 °C. The turbo pumps might be destroyed by a mixture of a liquid with solids and the valves and injectors for the oxidizer might be blocked. I doubt that a liquid mixture of O2, NO2 and N2O4 would contain more than very little O2.

  • $\begingroup$ I didn't thought it that ...And at the end of the day, using a gas that work with those criteria wouldn't help to carry the mixture I guess... So disappointing ! $\endgroup$
    – YaJBoy
    Sep 26, 2016 at 12:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.