Ionic Propulsion Based on Heated Taylor Cones of Ionic Liquids

Electrical propulsion characteristics of emissions from heated Taylor cones in vacuo are investigated for the ionic liquid 1-ethyl-3-methylimidazoliumbis(perfluoroethylsulfonyl)imide. Low specific impulses are encounteredat room temperature. However, the drop size decreases and the ion currents become very large at increasing temperatures, leading above 119°C to the appearance of a purely ionic regime with currents in excess of 4 μA. This mode of operation leads to thrusts approaching 1 μN per Taylor cone, at a specific impulse above 2000 s. The ion beam is dominated by the dimer ion (∼80%), with a mass-over-charge ratio larger than 600 amu, substantially larger than possible with traditional ion sources. The purely ionic regime had been previously observed in roomtemperature 1-ethyl-3-methylimidazolium + -BF 4 , but this is the first report where this regime exists over a wide range of currents. The levels of both thrust and specific impulse reported are considerably higher than those previously attained from single Taylor cones of organic electrolytes.