(712b) Reaction Kinetics for TMEDA As An Alternative Hypergolic Rocket Fuel

Kinetics of the hypergolic rocket fuel TMEDA (tetramethylethanediamine) has been studied because it is less toxic and non-mutagenic, in contrast to hydrazine and monomethyl hydrazine [1]. Hypergolic fuels (fuels that ignite spontaneously upon contact with an oxidizer) have been used in many propulsion and rocket applications. Historically, hydrazine rocket fuels such as monomethyl hydrazine and hydrazine have been used effectively as hypergolic rocket fuels. However, their negative feature is the carcinogenic, highly toxic nature of hydrazines

To explore the combustion chemistry of TMEDA, a reaction set has been developed based onusing an oxidizer of red fuming nitric acid (RFNA), a mixture of approximately 84% HNO₃, 13% N₂O₄, and 3% H₂O. As with the skeletal combustion mechanisms for traditional hydrocarbon fuels, it is proposed that TMEDA combustion is first dominated by hydrogen abstraction chemistry.  The resulting TMEDA radicals then undergo a series of beta-scissions and chemically activated reactions until the parent TMEDA molecule is broken down into various small C/H/N/O species. Due to the nature of the oxidizer, OH and NO_x chemistry had been expected to play a significant role.

Thermochemistry parameters for all the species in the proposed TMEDA skeletal mechanism were calculated using Gaussian 09 [2] at a CBS-QB3 [3] level of theory. Rate constants were estimated by analogy to appropriate hydrocarbon reaction rates or by transition-state optimizations combined with using master equation theory. The assembled reaction set and thermochemistry database were used in adiabatic flame simulations using a modified CHEMKIN Premix [4-7] code.  Flame conditions include pressures greater than or equal to atmospheric pressure and feed conditions ranging from slightly lean to slightly rich.

We gratefully acknowledge support of this research through the US Department of Defense under MURI contract W911NF-08-1-0171 and a National Defense Science and Engineering Fellowship (N. Labbe).

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