Simulations of the effect of neutral dinamics in magnetic nozzle expansions.

Electrodeless plasma thrusters (EPTs) promise several advantages over traditional electric propulsion devices. However, this kind of thrusters is still underperforming in terms of efficiency in comparison with more mature technologies and, despite the multiple efforts in understanding the underlying physics of plasma acceleration in magnetic nozzles, many questions about their operation are still open.

Most numerical fluid simulation codes have employed two fluid models to study the behaviour of magnetic nozzle expansion. However, experiments by Makrinich and Fruchtman have shown that ion-neutral collisions might increase total thrust in E x B devices and, on the other hand, results by Wachs and Jorns suggest that electron-neutral collisions decrease the amount of power available for ion acceleration and therefore decrease nozzle performance.

The present study employs a two-dimensional axisymmetric three fluid model of the plasma expansion. The model consists of a quasineutral, partially ionized plasma consisting of massless, warm, polytropic electrons; singly-charged, partially magnetized, cold ions and polytropic, neutrals, lastly, ionization and charge-exchange collisions are considered as source terms in the continuity and momentum equations of both ions and neutrals.

With these assumptions we obtain relevant maps for the different plasma properties. The effect of neutral dynamics in thrust generation is also studied considering different initial ionization degrees in the source.