MHD Thrusters for Small-Scale Underwater Vehicles: Silent Propulsion Using Magnetohydrodynamics

Overview

Magnetohydrodynamic (MHD) propulsion accelerates electrically conductive fluids through the Lorentz force generated by orthogonal electric and magnetic fields, offering a silent, mechanically simple alternative to propeller-based underwater propulsion. Although MHD pumps have been extensively studied, experimental investigations of compact MHD thrusters suitable for small-scale underwater vehicles remain limited. In this study, we designed, fabricated, and tested low-voltage seawater MHD thrusters using 3D-printed housings, neodymium magnets, and copper electrodes. Both rectangular and circular thruster geometries were developed and iteratively refined to evaluate the effects of channel geometry, electrode configuration, voltage, and power on propulsion performance. Experiments were conducted in seawater-salinity solutions, and propulsion speeds were quantified using video-based motion analysis and flow visualization. Measured velocities were compared with theoretical predictions derived from an acceleration model based on Lorentz-force-driven fluid motion. Results show that propulsion speed increases with applied voltage and electrical power, following the square-root scaling predicted by theory. Among the tested designs, the optimized circular thruster demonstrated superior structural stability, more uniform force distribution, and higher propulsion efficiency than the rectangular configurations and previous attempts. These results confirm the feasibility of compact, low-voltage MHD propulsion for small underwater vehicles and identify key performance-limiting factors. The findings provide practical design insights for advancing quiet, low-maintenance underwater propulsion technologies at a higher efficiency than previous experiments through geometry optimizations.

Competition history

• CSEF 2026 Applied Mechanics (Senior Division) · Entry S-02-26

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