Ionic Liquid Fuels for Chemical Propulsion

The ionic liquid (IL) program at the Air Force Research Laboratory is investigating tailored energy-dense liquids to provide a scientific foundation for the advancement of the performance and operability envelopes of current propulsion systems. General efforts focus on the discovery of energetic ILs based on heterocyclic and open-chain cations in combination with reactive anions. A major goal has been the development of IL fuels which undergo hypergolic ignition upon contact with common propulsion oxidizers. This account discusses the combination of some azolium, ammonium, hydrazinium, guanidinium and hydrazidinium cations with dicyanamide, nitrocyanamide, cyanoureate, nitrate, azide and tricyanomethanide anions. Their synthesis and characterization are described along with results of simple hypergolicity drop tests. The utility and reproducibility of these tests and possible mechanistic scenarios for these reactions are also discussed.