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Hydrazine $\ce{N2H4}$ and dinitrogen tetroxide $\ce{N2O4}$ form a hypergolic fuel and oxidizer pair widely used in spacecraft including Akatsuki (あかつき, 暁, "Dawn") also known as the Venus Climate Orbiter (VCO) and Planet-C.

Wikipedia states:

Hydrazine can be monoprotonated to form various solid salts of the hydrazinium cation ($\ce{N2H5+}$) by treatment with mineral acids. A common salt is hydrazinium sulfate, $\ce{[N2H5]HSO4}$, also called hydrazine sulfate. Hydrazine sulfate was investigated as a treatment of cancer-induced cachexia, but proved ineffective.

Double protonation gives the hydrazinium dication ($\ce{H3NNH3^2+}$), of which various salts are known

A comment below the Space SE question How did salt prevent Akatsuki's insertion burn? says:

Every article I see seems to parrot the same thing. I'm guessing this is yet another translation issue (Japanese to English) and the deposits are a hydrazine reaction product... which you could call a "salt". It's an interesting failure case that I hadn't heard of, thanks for the question.

Question: Are there possible reaction products from hydrazine and dinitrogen tetroxide alone that could form an ionic assembly of cations and anions and considered a salt, or would this require some additional contaminant, perhaps water or some organic material to be involved?

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    $\begingroup$ How about with the reaction chamber and nozzle? Of what are they made? $\endgroup$
    – DrMoishe Pippik
    Commented Sep 23, 2019 at 3:05
  • $\begingroup$ @DrMoishePippik I've annotated the image from this answer here: i.sstatic.net/wMImf.png I've mentioned "water, or some organic material contamination" in the question because these are common contaminations that can come from a wide variety of sources, and I think you are right that can include the reaction chamber and nozzle. Water could be (and probably is) a reaction product and could be plentiful, but my knowledge of chemistry is low and I don't know if that's enough to make something that might be considered a salt. $\endgroup$
    – uhoh
    Commented Sep 23, 2019 at 3:37
  • $\begingroup$ @DrMoishePippik The valve could potentially be pretty far away from them in terms of tubing, but I don't know much about rocket engines or what keeps the high pressure from the combustion chamber from pushing reaction products upstream in this case. $\endgroup$
    – uhoh
    Commented Sep 23, 2019 at 3:37
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    $\begingroup$ BTW, you might enjoy reading *Ignition! An Informal History of Liquid Rocket Propellants," by John D. Clark, library.sciencemadness.org/library/books/ignition.pdf $\endgroup$
    – DrMoishe Pippik
    Commented Sep 23, 2019 at 3:45

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