Minimum emission current of indium-field emission electric propulsion thruster

摘要

Purpose - Field emission electric propulsion (FEEP) thruster is a type of electric propulsion based on space-proven indium liquid metal ion sources. The lifetime of FEEP thruster limits its application in space. A better method to improve its lifetime is the reduction of emission current. This paper aims to discuss the minimum emission current of operating FEEP thrusters. Design/methodology/approach - In this work, theoretical models, including fluid-flow model and ion formation model, are analyzed. Current densities of these models are discussed and the minimum emission current is calculated. Findings - There are few equilibrium states under low emission current conditions. However, the minimum emission current is the only stable state at which the FEEP thruster can operate. Research limitations/implications - This analysis is mainly based on the needle indium FEEP, which is compared indirectly with experiments of gallium. Practical implications - This paper attempts to help designers choose appropriate electric parameters to improve the lifetime of FEEP. Originality/value - By introducing and analyzing theoretical models, this paper calculates the minimum emission current for stable operation of FEEP.