The predominant species in the plume residues resulting from the incomplete combustion of methylhydrazine (MMH)/N,N-dimethylhydrazine (UDMH) and N 2 O 4 (NTO) in rocket engines are methylhydrazinium and N,N-dimethylhydrazinium nitrate. Both compounds were synthesized, characterized and their crystal structures were determined.The thermal, shock and friction sensitivity of these compounds was investigated. For both compounds the products formed in their thermal decompositions were determined.