Performance improvement of 150-mN xenon ion thrusters

Abstract Research was conducted to establish basic xenon ion thruster technology for future applications. In an iterative design and test process to improve thruster performance, four thrusters of three designs were fabricated: the first laboratory model mark 1 (LM-1-MK-1), the first laboratory model mark 2 (LM-1-MK-2), the second laboratory model (LM-2), and the first breadboard model (BBM-1). Performance targets were a thrust of 150 mN , a specific impulse of 3500 s , and an ion production cost less than 150 W / A at 90% propellant utilization. Magnet temperature was limited to 200°C. The LM-1-MK-1 thruster used a 30 cm diameter two-grid system, with azimuthal springs in the grid supports to absorb thermal expansion, a discharge chamber with double sidewalls, an inner effective chamber and an outer magnet yoke. Test results showed an ion production cost of 178 W / A . The LM-1-MK-2 thruster was designed to give more stable operation and lower magnet temperatures, with a resulting maximum magnet temperature of 254°C. The LM-2 thruster used axial springs in the grid supports and a discharge chamber with a single soft-iron wall. It gave an ion production cost of 168 W / A and a magnet temperature of 240°C. The BBM-1 thruster used a 35 cm diameter three-grid system for longer life. The grid fabrication method was improved to achieve greater grid aperture dimensional accuracy. This thruster achieved the performance targets with an ion production cost of 134 W / A and a magnet temperature of 172°C.