Ab initio chemical kinetics of key processes in the hypergolic ignition of hydrazine and nitrogen tetroxide

Kinetics and mechanisms of key processes leading to the hypergolic ignition of N₂H₄ and N₂O₄ have been studied by high-level ab initio molecular orbital theory in conjunction with statistical theory calculations. The results of this work suggest that the explosion following the contact of N₂H₄ and N₂O₄ in liquid or gaseous state at low temperatures can be initiated by the rapid reaction of N₂H₄ with ONONO₂ isomers of N₂O₄ producing H₂NN(H)NO+HNO₃ without thermal activation accompanying with 21kcalmol^-1 exothermicity. The HNO₃ thus formed can instantaneously produce N2H5+NO3- salt releasing twice as much acid-base neutralization energy to enhance NO₂ and N₂H₃ radical production. The thermochemistry and rate constants for reactions of species involved (NO₂, NO₃, N₂O₄, and its isomers, OH and N₂H_x (x=2, 3, and 4)) in the chain initiation and propagation have been predicted and compared with available data in the literature.