Field Emission Electric Propulsion: Spectroscopic Investigations on Slit Emitters

摘要

A slit emitter with a closed propellant supply system firing in any direction, requiring no gravitational forces was developed. Quantitative data relating the constituents of the residual gas atmosphere to the wetting behavior of the liquid metal propellant and the emission site distribution were obtained. A homogeneous distribution of equally spaced emission sites is observed; the measured spacing is in good agreement with a simple hydrostatic model of wavelike instabilities on electrically stressed surfaces of fluids. Mass and optical spectroscopy of the ion beam constituents confirm the predominant nonthermal origin of neutral atoms, supporting the microdroplet hypothesis of the origin of the neutral mass flow. The capability of the slit emitter to operate without current saturation effects at considerably higher values of the specific emission current than measured hitherto is demonstrated.