Unsymmetrical dimethlyhydrazine or "UDMH" is a propellant which has been used by Russian, American, European, Chinese, and Indian rockets.

unsymmetrical dimethylhydrazine

Russian rocket engineers nickname it "heptyl". Why was this name chosen, especially when it means a compound with 7 carbon atoms, and UDMH has only two?

Addendum: As several commenters also seem to believe, my suspicion is that the name was chosen as a codeword during the Cold War to deceive enemies. However, that is merely a guess, which I why I originally asked

(Support your answer with sources; no speculation please.)

The article cited by Wikipedia states only

To be specific, the Proton-M — a booster rocket used for decades to carry commercial and military payloads — relies on a combination of unsymmetrical dimethylhydrazine (better known as heptyl fuel) and nitrogen tetroxide.

without providing any source for that claim, and no reason why that name was chosen.


  • $\begingroup$ sometimes I'll post links to my chemistry-related questions in The Periodic Table but I don't know if it would be helpful in this case $\endgroup$ – uhoh Apr 10 at 2:51
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    $\begingroup$ From Wikipedia: "UDMH (which is referred to as "heptyl" [codename from Soviet era] by Russian engineers" If it was a codename, it should not be related to seven carbon atoms. The name should give no information about the compound to the cold war enemies. $\endgroup$ – Uwe Apr 10 at 8:31
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    $\begingroup$ There is C7H20N2O4S called Heptylhydrazine sulphate. It has 7 carbon atoms. May be the cold war code name should indicate this compound while in fact UDMH was used. $\endgroup$ – Uwe Apr 10 at 8:44
  • $\begingroup$ There is also Heptylhydrazine C7H18N2 $\endgroup$ – Uwe Apr 10 at 14:04
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    $\begingroup$ @Uwe A codename could be chosen to deliberately give the wrong information rather than to give no information. $\endgroup$ – Russell Borogove Apr 10 at 17:38

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