Monomethylhydrazine (MMH) (CH3)NHNH2 is currently used as fuel for spacecraft engine combustion chambers. The Aestus engine of the upper stage of Ariane 5 is
fed with MMH under pressure of 16 bars. The propellant, initially at room temperature, is about 393 K when introduced into
the combustion chamber, due to heating up through the regenerative circuit. As MMH is unstable above 373 K, it has been necessary
to check its decomposition rate and vapor pressure under such conditions.
The vapor pressure of this propellant has been measured in a pressure vessel and the thermal decomposition rate was determined
with the same device up to 500 K.