Ionic Liquid Fuels for Chemical Propulsion

Abstract : Task I: Unfortunately, neither the cyanoborohydride approach nor the pure tetrakis-tetrahydroborate aluminate ILs discovered possess the desirable physical properties for a suitable propellant. In general, their major shortcomings still are poor liquid range and high viscosity as well as the high hydrocarbon content of the cations required to lower their melting points which severely limits propellant performance. In light of our discoveries we turned to systems simpler and higher performing than the complexed Al(BH4)4- anions. Solutions of Li-Al hydrides and LiBH4 in ethers have shown some desirable propellant properties and a variety of lithium metal hydrides are commercially available. This suggested an entry point into the coordination chemistry of lithium salts with some new high energy heterocyclic ring systems. Task II: In this work we have used a variety of complementary experimental techniques and theoretical approaches to elucidate the reaction mechanisms involved in the decomposition of energetic RTILs as a result of thermolysis, catalysis and oxidation. As our knowledge improves in these areas, it should be possible to build predictive numerical models for the accurate assessment of the performance and the state-of-health in RTIL monopropellant and bipropellant thrusters.