Vaporization and thermal decomposition of dimethylhydrazine, hydrazine hydrate and their UH25 mixture

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