Convergent neutral gas injection using supersonic gas puffing (SSGP) method for propellant feeding system in RF electric propulsion

A convergent gas feeding method is proposed to alleviate neutral gas depletion near the central plasma region in typical electrodeless radio-frequency (RF)/helicon plasma thrusters. To achieve further performance improvement, the SuperSonic Gas Puffing (SSGP) system is one of the methods that is expected to overcome the above-mentioned depletion and the density limit. This study discovered that the spatiotemporal profiles of the neutral pressure and the estimated gas diffusion angle vary depending on the SSGP gas feeding condition, i.e., the nozzle size, filling pressure, and the valve opening time. Convergent gas feeding is successfully conducted using the SSGP method in a vacuum. As a preliminary study, high-density plasma is also obtained in the vicinity of the gas injection region using the developed SSGP system. The effects of the gas feeding position and an external divergent magnetic field on the plasma density are investigated. A suitable gas feeding position/region exists for plasma generation using the RF/helicon plasma thruster. Published under an exclusive license by AIP Publishing.