Helicity-Aware Design of Hall-Type MHD Thrusters

We analyze thrust production in a single-fluid magnetohydrodynamic (MHD) thruster with aligned flow and magnetic field. Starting from the momentum equation with an anisotropic conductivity tensor, we show that axial thrust is governed by the competition between the imposed axial electric field and the motional electric field generated by the flow across a radial magnetic field. In a coaxial Hall-type geometry, this yields a simple design rule: thrust increases when the motional field exceeds the axial bias. We clarify the role of cross-helicity (a measure of flow–field alignment) versus the motional term in Ohm’s law. A validation plan is outlined, combining finite-volume MHD simulations with laboratory measurements (PIV, Hall probes, thrust stand). The framework identifies practical levers—velocity–field alignment, magnetic topology that enhances the radial field, and control of the off-diagonal conductivity—for efficient MHD propulsion.