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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!

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    $\begingroup$ +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
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    $\begingroup$ 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

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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.

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  • $\begingroup$ 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

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