Experimental investigation of optimal positional relation between RF antenna and magnetic cusp for thrust performance of RF plasma thruster

Abstract

The electrodeless radio-frequency (RF) plasma thruster, which avoids the risk of electrode failure, is likely to be a highly appealing electric propulsion system. Although this type of thruster has achieved notable thrust performance in high-power conditions of several hundred kilowatts, it falls short in low-power conditions of several kilowatts. To improve the thrust performance at low power, an RF plasma thruster has been proposed that involves a magnetic cusp. This study aimed to reveal the optimal positional relation between the RF antenna and the magnetic cusp. The performance of an RF plasma thruster with a magnetic cusp was characterised experimentally using a torsion-pendulum thrust stand for six positional relations between the RF antenna and the magnetic cusp. The maximum thrust performance (4.4 mN, 443 s at 1,000 W and 1.2 mg/s of Ar) was obtained with the RF antenna located downstream of the magnetic cusp. The proposed optimised positional relationship of the thruster components is with the RF antenna located downstream of the magnetic cusp and close to the thruster exit.