Droplet velocity and beam divergence modulation in ultrasonic nebulization electric thrusters via dual-electrode optimization

Abstract This study proposes a novel Ultrasonic Nebulization Electric Thruster (UNET), which employs an ultrasonic nebulizer as the atomization source to reduce volume, mass, and cost of space electric thruster. A custom experimental system is developed to evaluate parameters such as current, thrust, and specific impulse, while numerical simulations are performed to analyze the electric field and beam characteristics. Experimental results show that the addition of an accelerator improves performance by at least 70% and reduces the risk of electrode short circuits. The UNET with an accelerator achieves a thrust of 750.2 μN and a specific impulse of 38.4 s. Simulations reveal that increasing the diameter of the emission surface leads to larger beam divergence and higher droplet velocity. Without an accelerator, raising the emitter potential increases only the droplet velocity. After integration of the accelerator, both droplet velocity and the operating voltage range improve, and beam divergence becomes adjustable. The beam divergence angle of UNET with an accelerator changes twice, once near the extractor and once near the accelerator. A higher extractor-accelerator potential difference results in a smaller divergence angle, while a higher emitter-extractor potential difference increases droplet velocity, with acceleration primarily occurring between these two electrodes. Additionally, lowering the extractor potential further enhances droplet velocity and reduces the risk of short circuits. This study provides key theoretical support for optimizing the design of UNETs.