Performance of the Xenon Feed System on Deep Space One

Abstract

Propulsion for the Deep Space One (DS1) spacecraft is provided by a xenon ion engine. Xenon is stored in a supercritical state and is delivered as a low-pressure gas to the thruster and two cathodes (called the main cathode and neutralizer) by a xenon feed system (XFS). This mission requires tight constraints on thruster performance, which in turn requires separate and very accurate throttling of the thruster and cathode  ows; the DS1 spacecraft is the Ž rst of its type to utilize a xenon ion engine that can be throttled. Flow is regulated separately to the thruster and cathodes to an accuracy of § 3% using three calibrated  ow control devices that are each fed by a dedicated plenum tank. Bang–bang regulators are used to control the set pressures in the plena. The resulting XFS control algorithms are quite complex. The XFS is controlled by a digital control interface unit and the control algorithm for achieving steady-state xenon  ow is presented. The worst-case error in  ow is shown to be less than § 3%, accounting for random and systematic errors. At the time of writing, the individual components are in excellent health and the performance of the XFS is as expected.