Research on the ignition characteristics and discharge performance of LaB6/W composite cathode arcjet thruster

Abstract

A 200 W class low-power arcjet thruster with a LaB₆/W composite cathode has been developed, and a hot-start ignition method has been proposed. This method reduces the ignition voltage to 350 V with a heating power of 90 W, approximately 80 %–90 % lower than the high-frequency or high-voltage ignition methods (several kilovolts). After ignition, the discharge current rises to approximately 25 A within 50 μs, decreases to the operating current after 1–2 ms, oscillating with a fluctuation of ±0.5 A before stabilizing. Meanwhile, the discharge voltage rapidly drops from 350 V to the operating voltage within 100 μs and stabilizes with an oscillation amplitude of ±0.2 V. No transition occurs from low-voltage to high-voltage modes during the hot-start ignition process. Experimental tests using krypton and argon propellants were conducted, showing optimal performance for krypton at 100 W, producing 35.4 ± 0.2 mN of thrust, a specific impulse of 71 ± 2 s, and a thrust efficiency of 8.0 ± 0.3 %. For argon, the optimal parameters were 115 W, producing 26.4 ± 0.2 mN of thrust, a specific impulse of 81 ± 2 s, and a thrust efficiency of 7.0 ± 0.3 %. After 100 ignition cycles and 20 h of operational testing, no erosion was observed on the cathode or anode surfaces. This study demonstrated the advantages of the hot-start ignition method in reducing ignition voltage, alleviating cathode erosion, and enhancing discharge stability.