Modelling and design of Earth and Mars atmosphere-breathing electric propulsion systems (ABEP) using a cathode-less RF thruster

Atmosphere-breathing electric propulsion (ABEP) is a concept of electric propulsion system that has the potential to revolutionise space mission scenarios by using the air from the atmosphere as a propellant source instead of relying on a stored reservoir. This promising technology could enable very low Earth orbit (VLEO) mission scenarios, providing a clean, efficient, and sustainable propulsion system for spacecraft. Due to the significant change of atmospheric composition with altitude, which decisively affects the performance of the ABEP system, accurately simulating ABEP plasma chemistry plays a crucial role in the mission design. However, achieving a proper estimation of the propulsive performance surely represents a challenging task, as a result of the highly complex plasma dynamics as well as the large number of species involved. In this study, a numerical routine was developed with the aim of portraying the performance of a radiofrequency ambipolar thruster as a whole. First, a DSMC simulation of the engine intake is carried out at a particular pressure level and atmospheric composition; the resulting flow properties are then used as input to a 0D Global Source Model (GSM) that evaluates the generation of plasma inside the ionisation chamber. Lastly, the plasma expansion in the magnetic nozzle is simulated by means of a fully-kinetic 2D3V Particle-in-Cell model. The modelling of the background neutral density of the atmosphere and its interaction with the plasma plume has been included as well.