Numerical simulation of a rarefied gas jet emanating from an ion-optical system of the microthruster

Abstract

A jet of ionized rarefied gas escaping from an ion-optical system of a prototype resonator RF-ion thruster into the surrounding space with low background pressure is considered. After a number of assumptions, the escaping jet is replaced in the first approximation by a neutral rarefied gas, which allows us to characterize the flow satisfying the hypothesis of flow continuity. The equations describing the motion of a continuous medium are solved numerically using the Bubnov–Galerkin method, which is used in rarefied gas dynamics. Non-stationary heat transfer is taken into account due to the interaction of the gas flow with a local heat release region in the gap between the grid elements of the ion-optical system. The heat release mechanism is described by the heat conduction equation, which is solved together with the gas dynamics equations. The obtained calculation results are compared with the experimental data. The conducted modeling made it possible to obtain the spatial structure of the neutral rarefied gas flow in the cylindrical channels and microchannels of the microthruster. By comparing the obtained spatial structure with the real thermal imaging picture of the jet, it is possible to estimate the contribution of the resonator acceleration to the total energy of the jet.