Taming nonlinear oscillations and turbulence for optimal design and operation of space plasma thrusters

Current in-space propulsion technologies are insufficient for the ambitious space missions of the future. Electrodeless plasma thrusters (EPTs) offer a solution to this problem, enabling the use of arbitrary propellants, simplifying device architecture, and facilitating scaling to high powers. Promising performance figures have been recently demonstrated. Nevertheless, EPTs suffer from ‘anomalous transport’ that increases plasma losses to the walls, limiting their efficiency and durability. This is due to plasma instabilities that set up oscillating and turbulent structures nonlinearly, enhanced by the strong electromagnetic fields applied to heat the plasma. However, the exact mechanisms remain unknown and unchecked, preventing the design of truly efficient devices. ROCINANTE aims to unravel and control the causes of anomalous transport in EPTs by accomplishing four objectives: (1) Obtain high-accuracy, high-resolution experimental datasets of the fluctuating spectrum inside and near an EPT source. (2) Establish an unprecedentedly fast and accurate kinetic-electromagnetic plasma model. (3) Elucidate the roots and nature of nonlinear oscillations and turbulence in EPTs, and their effect on the cross-field anomalous transport that limits thruster performance and durability. (4) Assess the observability of the oscillating structures and their open-loop controllability. This will be made possible by a unique methodology consisting of a specifically-designed experiment with novel non-intrusive sensors, a new 2D+ time-implicit particle-in-cell code that exploits the physics of the problem for unsurpassed computational performance, nonlinear data-driven analysis techniques and reduced order models, and the characterization of the system response to periodic forcing actuation. The success of ROCINANTE will unveil the true physics of anomalous transport in EPTs and unlock the development of ultra-efficient plasma thrusters based on active control.