Efficiency Estimation of EMI-BF 4 Ionic Liquid Electrospray Thrusters

Ionic liquid-based Electrospray Thrusters offer an attractive alternative for flexible, high specific impulse micropropulsion systems. Among the most promising attributes of these thrusters is their high efficiency as previously estimated by mass spectrometric and time-of-flight techniques. The energetic structure was indirectly revealed by these studies, suggesting that charged particles are emitted with a narrow energy spread centered close to the applied potential with just a small differential probably due to the energy invested in extracting charged species directly from the liquid surface. A direct characterization of the beam energy distribution from a single tungsten emitter externally wetted with the ionic liquid EMI-BF 4 using a retarding potential analyzer complements original estimations allowing a more reliable determination of the thruster overall efficiency.