Experimental investigation on the polarity switching process with different operating frequencies of the bipolar ionic liquid thruster

The bipolar ionic liquid thruster employ ionic liquid as propellant to discharge positively and negatively charged high-energy particles under an alternating current(AC) power source, effectively suppressing electrochemical reaction and ensuring charge neutrality. Determining an optimal AC supply power source frequency is critical for sustained stable thruster operation. This study focuses on the emission characteristics of the ionic liquid thruster under varied AC conditions. The AC power supply was set within the frequency range of 0.5 to 64 Hz, with eight specific frequency conditions selected experimentation. The experimental results indicate that the thruster operate steadily within a voltage range of ±1470 to ±1920 V, with corresponding positive polarity current ranging from 0.41 to 4.91 μA and negative polarity current ranging from -0.49 to -4.10 μA. During voltage polarity switching, an emission delay occurs, manifested as a prominent peak signal caused by circuit capacitance characteristics and a minor peak signal resulting from liquid droplets. Extended emission test were conducted at 16 Hz demonstrating approximately 1 hour and 50 minutes of consistent emission before intermittent discharge. These findings underscore the favorable impact of alternating current conditions within the 8 to 16 Hz range on the self-neutralization capability of the ionic liquid thruster.