Vaporisation dEcomposition thermique de dimethylhydrazine, d'hydrate d'hydrazine de leur melange UH25

Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An addition of a small amount of hydrazine hydrate N2H4×H2O was proposed to increase the thermal stability of UDMH. The mixture where the mass ratio (CH3)2NNH2/N2H4×H2O is equals to 75/25, is called UH25. These propelling agents are unstable when they are heated and the optimisation of burning conditions requires a good knowledge of their vaporisation and of their thermal decomposition kinetics.