Plasma separator thruster.

Abstract

The plasma separator thruster is an advanced concept in ion thruster design which is based on independent operation and optimization of the plasma source and plasma extraction system. The plasma source consists of a propellant feed tube which functions as a hollow cathode. Cesium vapor is fed from the cathode through a simple converging-diverging nozzle, and is ionized by a coaxial discharge between the hollow cathode and a downstream ring anode. The dense plasma is then expanded aerodynamically to a pressure suitable for ion extraction and acceleration. Surface recombination is nearly eliminated by proper nozzle and anode design, and volume recombination is avoided by keeping the electron temperature high in the continuum region. A modified theory of plasma extraction is presented to explain the experimentally observed total extraction of plasma ions. Considerable improvement in efficiency and lifetime is predicted for a fully developed thruster of this type, based on the measured performance of the thruster components. Several complete but unoptimized thruster systems have been operated to demonstrate compatibility of components.