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Both nitrous oxide (N2O) and dinitrogen tetroxide (N2O4) are used in storable propellant combinations, so, simply as a continuation, can the higher oxides of nitrogen (N2O5, N2O6, etc.) still be used in an engine? Is it practical but just lacking in performance, or unstable/difficult like ozone?

I know this is very probably a silly question and is absolutely made in total ignorance, but I just couldn't find anything on it and from a highly peripheral point of view it seems like a good idea, or is at least interesting.

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  • $\begingroup$ I don't think N2O6 exists. $\endgroup$ Commented Dec 4, 2021 at 2:38

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Not likely

N2O5
Well, the stuff IS a very strong oxidizer.

But considering that the solid form is a hard white salt-like substance, and it melts at 41 °C, and boils at 47 °C, so it can be a wee bit tricky to pump through an engine.

Add the fact that it quite happily decomposes down to NO2 + O2 at temperatures well below its freezing point, and you have one spectacularly uncooperative oxidizer.

N2O6 is so unstable, it decomposes before it can be detected. Same for N3O6.

N4O6, more properly N(NO2)3, does exist in that it can be made in a lab, but it refuses to sit still in large enough quantities and for long enough for its physical properties to be examined. This does not bode well for its use in a rocket engine.

As a rough rule of thumb, the more N and O one crams into a single molecule, the more the molecule will resemble high explosives rather than usable rocket oxidizer.

Could I not interest you in more tractable oxidizers, like dioxygen difluoride, better known by the cuddly name of "FOOF"? It should be more stable, and deliver better Isp than these higher order oxides of nitrogen. (And yet appeal to the masochistic mad scientist that wanted to play with high order nitrogen oxides.)

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    $\begingroup$ The classic succinct rundown on the hair-eliminating nature of FOOF is Derek Lowe's science.org/content/blog-post/… , which features the word "explosion" rather more often than your Kerbals will like. He describes the report of one hardy explorer: "If the paper weren't laid out in complete grammatical sentences and published in JACS, you'd swear it was the work of a violent lunatic. I ran out of vulgar expletives after the second page." $\endgroup$ Commented Dec 1, 2021 at 15:18
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    $\begingroup$ @TomGoodfellow I've managed to find the original paper by A. G. Streng: andrew.cmu.edu/user/jklein2/O2F2.pdf $\endgroup$ Commented Dec 1, 2021 at 19:47
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    $\begingroup$ Not the worst idea. Somebody wanted to use O17 ozone. $\endgroup$
    – Joshua
    Commented Dec 1, 2021 at 21:36
  • $\begingroup$ @RedwolfPrograms - just ... wow! coming from Lowe's reference my expectations of that paper were already high but it exceeded them just the same. Thank you kindly for that early Xmas gift. $\endgroup$ Commented Dec 1, 2021 at 23:42
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    $\begingroup$ Even if N2O5 is a solid, it could still be very useful. I'd heard of some theoretical solid motors that use solid LOX just for the performance so surely something as efficient (compared to other solids) as N2O5 would be perfect, especially considering its (probably) hypergolic $\endgroup$
    – R. Hall
    Commented Dec 2, 2021 at 4:24

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