Characterization of electrospray beams for micro-spacecraft electric propulsion applications

•Simulations of trajectories helped optimize design of extraction electrode system.•Electrospray cone-jet emission achieved for several doped propellants.•Dual alternate emission, eliminating the need of a neutralizer, was confirmed.•Specific impulse of cone-jet mode higher than that of a cold-gas thruster.

Electric propulsion for spacecraft offers many advantages compared to other traditional counterparts such as chemical propulsion. An electrostatic colloid thruster, well suited for small spacecrafts due to its inherent small size, is investigated. The underlying phenomena governing the plume, namely collisions and focusing are parameterized. The determining properties of the electrospray-based thruster, such as specific impulse, are measured for several propellants and demonstrated to be higher than cold-gas thrusters even for singly charged droplet mode. Moreover, the interesting concept of a dual colloid system with positively and negatively charged cone-jet beams was shown to be feasible by simulations and experiments.