I propose the hydrogen cyanide - fluorine rocket.
It has the fabulous potential for a vacuum Isp of up to 380s, with a propellant mix density of 1023 kg/m^3, handily beating methalox mixes. It is non-cryogenic and burns at over 4000K.
Exhaust is 43.3% hydrogen fluoride.
oh......... oh good gods.
43.3% HF exhaust? good fucking gods that's scary. I would be interested in seeing a thrust test with an engine burning that though..... for RCS type engines it might be worth the danger..... but then again we have udmh for that which works very well for RCS.
As long as tested on a different planet, in a different solar system, I'm ok with this
What a NIMBY
Not in my low earth orbit.
Seriously, who needs foliage, or lungs, or skin, or bones....