Numerical investigations of protector effect on a thruster

The plume flow of space thrusters can cause series of harmful effects to spacecraft by impinging on some sensitive surfaces. To prevent the plume impingement effects that a 60N thruster can do to the backflow region, a plume protect cover is intended to be assembled to the thruster. The flow field from the combustion chamber of the thruster to the vacuum environment contains both continuum and rarefied flow regimes, which makes it difficult to model this flow phenomenon by using one single method. The coupled NS/DSMC method is one of the best choices for modeling the continuum-rarefied transitional flows. In present study, a coupled NS/DSMC solver is developed by the authors and is used to estimate the effect of the plume protector assembled to the 60N thruster. The present coupled NS/DSMC solver is constructed with the NS solver NozzleFlow and DSMC solver PWS. Interface location is determined by combining two continuum breakdown parameters. One is the KnGL parameter and the other is the thermal non-equilibrium parameter Ptne. State-based coupling method is adopted to transfer information between the continuum and particles methods. The continuum-rarefied interfaces and gas parameters of the vacuum plume flow field of the thruster are obtained by conducting coupled calculation, which shows that the plume protector can decrease the mass flux density in the back flow region by two orders. The present coupled NS/DSMC method can be a useful tool for the vacuum plume effects analysis.