Abstract: To improve the thrust of colloid thrusters by increasing the number of emitters, a novel electric propulsion method named ultrasonically electric propulsion (UEP) was proposed.The dense capillary standing waves produced by ultrasonic vibration are the emitters,so the number and density of emitters are improved fundamentally and relatively high thrust density appears.The emission mechanism of UEP was analyzed and the corresponding emission model was developed. Through theoretical analysis on the formation of capillary standing waves and the emission of the charged droplets, the relationship among the surface tension, inertial force and electrostatic force at the crests of standing waves was introduced. Furthermore, the radius of the standing wave crests and the diameter of the charged droplets were theoretically solved. The estimation equations of spray current, specific impulse and thrust were proposed. Based on the theoretical analysis, the influences of the electric filed strength, ultrasonic vibration frequency, ultrasonic vibration power and propellant on the performance of UEP were analyzed and experimentally verified.

Key words: ultrasonically electric propulsion (UEP), emission model, capillary standing waves, charged droplets, emission mechanism