Decomposition of Ionic Liquid Ferrofluids for Multi-Mode Spacecraft Propulsion

Ionic liquid ferrofluids based on mixtures of [Emim][EtSO4] and [Bmim][NO3] fuels and hydroxylamonium nitrate oxidizer were synthesized by adding iron oxide nanoparticles. The resulting propellants were then tested for decomposition capability. Spot plate testing indicated that the temperature required to initiate rapid decomposition dropped from 115 o C to 75 o C with a 30% by weight addition of iron oxide for the [Bmim][NO3] propellant. Adding more iron oxide resulted in an increase in onset temperature. The [Emim][EtSO4] propellant had a much lower decrease in onset temperature, bottoming out at 90 o C. Batch reactor tests under vacuum showed that 10% addition of iron oxide results in the greatest increase in decomposition rate for both propellants. Since most ionic liquid ferrofluids do not exhibit the Rosensweig instability below 50% iron oxide by weight, it is unlikely this will be of use in a multi-mode system. However, adding a small amount of iron oxide to ionic liquid monopropellants could be beneficial as it will reduce power requirements, while only reducing specific impulse by roughly 2.5%.