Characterization of the performance of a RIT-10 and rf-neutralizer for an ABEP system

We investigated a RIT-10 ion thruster and a radio-frequency neutralizer using molecular oxygen, molecular nitrogen and mixtures of both gases as propellants to assess their suitability as components for an air-breathing electric propulsion (ABEP) system. A combination of diagnostics - including Langmuir probes, optical emission spectroscopy (OES), Faraday cups, retarding potential analyzers (RPA), mass spectrometry and Raman spectroscopy - was used to characterize the plasma parameters, plume properties and material contamination. A comparison was made between the experimental results for the single gases and a corresponding global model. Our results show that the dissociation of the molecules and chemical reactions taking place in the plasma have a significant impact on the performance of both tested devices and thus need to be assessed for all operating points. Chemical reactions between oxygen and different material surfaces are identified and safe operating points established. A general optimization strategy to improve the performance of both devices is suggested - an essential requirement for successful missions using ABEP systems. The findings provide critical insight into material suitability and operational regimes for ABEP systems. An optimization based on an in-depth understanding of all parameters involved is only possible by combining multiple diagnostic tools and global modeling.