Xenon ion sources for space applications (invited)

In this article, we describe the technology of xenon ion thrusters under development for space-propulsion and plasma-contactor applications. Emphasis is placed on the 1.4-kW Xenon Ion Propulsion Subsystem (XIPS) designed for satellite stationkeeping. The 25-cm-diam XIPS thruster produces 63.5 mN of thrust at a specific impulse of 2800 s, requiring only about one-tenth the propellant mass of conventional chemical-propulsion systems. Using a ring-cusp magnetic field to confine the discharge plasma, the XIPS thruster converts input power into thrust-beam power with an efficiency of over 82%. We also describe a XIPS ion source under development for more demanding propulsion applications such as orbit raising. A 30-cm-diam laboratory-model XIPS thruster scaled from the smaller unit produces over 340 mN of thrust with an input power in excess of 10 kW and a specific impulse of about 4900 s. Under these operating conditions, the XIPS thruster converts input power into thrust-beam power with an efficiency of 91%. With its ion-extraction electrodes and ion-beam neutralizer removed, the XIPS discharge chamber has been shown to be a highly efficient xenon plasma contactor for a variety of applications, ranging from space-science investigations to electrodynamic tethers. We will describe a 1991 flight application in which our 25-cm XIPS plasma contactor will be used to stabilize the electrical potential of the Shuttle Orbiter during firings of a 1.5-A electron beam from its payload bay.