TheUnassuming hinted (thanks!) at efficient N-N coupling by O2
+catalyst or by electrolysishttp://www.chemicalforums.com/index.php?topic=97919.msg345959#msg345959https://pubs.acs.org/doi/10.1021/jacs.8b05245
which achieves molecules as crowded as tetraphenylhydrazine, so cyclopropylmethylhydrazines
look accessible. This needs a good path to dicyclopropylamine, as some previous compounds here do.
The dicyclopropyldimethyl would be slightly flammable but a mix with heavier compounds shall improve it and lower the freezing point, the isomers being welcome too.
The Osiris applet estimates that these hydrazines are harmless (but it considers Udmh as slightly carcinogenic).
The seemingly cheap N-N coupling would apply to other compounds here like diazetidyl.
Cyclopropyls are expected to weaken the N-N bond further. Bad for the heat stability, but it may improve the hypergolic ignition with N2
Marc Schaefer, aka Enthalpy