Hypergolic Reaction of Dicyanamide-Based Fuels with Nitric Acid

Understanding the ignition reactions for hypergolic propellants is an important step in developing a complete reaction model that can be used in engine design and optimizing the composition of the fuel-oxidizer pair. To that end, an experimental study of the hypergolic reaction of sodium dicyanamide with nitric acid was conducted to investigate a recently proposed reaction mechanism for ignition of this family of ionic liquids. Sodium dicyanamide was used to simplify contributions to products from the cation of the fuel. Gas-phase reaction products were studied using microprobe sampling and mass spectrometric analysis. In addition, a chemical assay was used to test for the presence of dinitrobiuret, the key intermediate in the proposed mechanism. Most of the results from the study support the proposed mechanism, with the only exception being the lack of direct evidence for dinitrobiuret. Additional reactions for the ignition reaction scheme are proposed.