Synthesis and testing of hypergolic ionic liquids for chemical propulsion

Synthesis of new highly energetic ionic liquids (ILs) is described, and their hypergolic ignition properties are tested. The synthesized ILs combine the advantages of conventional rocket propellants with the energy characteristics of acetylene derivatives. To this end, N-alkylated imidazoles (alkyl = ethyl, butyl) have been synthesized and alkylated with propargyl bromide. The desired ionic liquids have been produced by metathesis using Ag dicyanamide. Modified hypergolic drop tests with white fuming nitric acid have been performed for N-ethyl (IL-1) and N-butyl propargylimidazolium (IL-2) ionic liquids. In the modified drop tests, high-speed shadowgraph imaging is used to visualize the process, and the temperature rise due to ignition is monitored with a two-color photodetector. It is shown that the ignition delay is shorter for IL-1 as compared to IL-2. The ignition of IL-1 occurs in two stages, whereas the combustion of IL-2 proceeds smoothly without secondary flashes.