Design and Development of a Small-Scale Permanent Magnet Reconnection Thruster

A compact magnetic reconnection thruster, scaled down from an original 60 cm to ~35 cm diameter, has been designed and characterized for experimental validation. This novel propulsion concept uses the conversion of magnetic energy into kinetic energy through magnetic reconnection within a reduced annular channel (Ebrahimi, F. (2020). An Alfvenic Reconnecting Plasmoid Thruster. Journal of Plasma Physics, 86(6)). The magnetic reconnection thruster is expected to achieve higher thrust and exhaust velocities than conventional chemical and electric systems. This iteration of the thruster replaces traditional current-driven coils with a carefully optimized array of permanent magnets, which offers improved simplicity, durability, and cost-effectiveness by eliminating the need for continuous power to sustain magnetic fields. Magnet placement and orientation were optimized using Simsopt with the Greedy Permanent Magnet Optimization (GPMO) and Relax-and-Split algorithms. GPMO iteratively selects positions that reduce magnetic field error, while Relax-and-Split efficiently handles the high-dimensional, sparse configuration by alternating between smooth and nonsmooth subproblems. Two magnet types from UW-Madison will be used, with testing and measurements conducted at WiPPL and at PPPL. We present the finalized smaller thruster design, including detailed magnetic field measurements and verification of the optimized permanent magnet array. Work supported by DOE.