The Griffiths Rotating Electromagnetic Nozzle (GREMN) is a propulsion‑agnostic electromagnetic augmentation system designed to work with any engine that produces a plasma or partially ionised exhaust. It is not a thruster by itself; it is a downstream collar that adds thrust, stability, and plume control using a rotating magnetic field. The architecture is derived directly from resistive magnetohydrodynamics and Maxwell’s equations, with all performance predictions obtained analytically rather than through heuristic scaling.

The core mechanism is a rotating magnetic field generated by a permanent‑magnet assembly. This field induces azimuthal currents in the exhaust plasma. Those currents create two simultaneous effects: they generate stabilising shear flow that suppresses Kelvin–Helmholtz and breathing‑mode instabilities, and they produce additional axial thrust through the J×B Lorentz force. The rotating field has the form B(r,θ,t) = B0(r)[cos(mθ−ωt)er + sin(mθ−ωt)eθ], where m is the pole‑pair number and ω is the rotation frequency. The induced azimuthal current density follows directly from Faraday’s law and Ohm’s law, and the electromagnetic thrust is obtained by integrating JθBr over the plasma cross‑section.

A linear stability analysis shows that GREMN suppresses Kelvin–Helmholtz instability when the shear‑to‑growth‑rate ratio Ωs/γKH exceeds unity. The design achieves Ωs/γKH between 3.5 and 15, providing complete suppression across the relevant mode spectrum. Rayleigh–Taylor and drift‑wave instabilities are also suppressed because their growth rates are far below the imposed shear rate. Experimental data from rotating‑plasma devices and the MRX experiment support the predicted suppression thresholds.

Thrust comes from two sources. The thermal nozzle contribution arises from magnetic‑mirror acceleration, with a mirror ratio of 20–60 producing realistic mirror efficiencies of 0.75–0.85. This yields 45–60 N of thrust at 1 MW electrical input for argon propellant. The electromagnetic contribution adds 15–25 N, scaling with σB0²ωa²L. Combined thrust is 60–85 N, with specific impulse of 2,500–4,000 s and thrust‑to‑power ratio of 60–85 mN/kW. These values occupy a performance region between Hall thrusters and MPD thrusters, without the erosion or instability penalties of either.

A two‑scale field architecture is defined for future upgrades. Compact REBCO high‑temperature superconducting inserts can generate 30–40 T in millimetre‑scale bores, producing localised spikes in B² and dramatically increasing local shear‑stability margins. These inserts do not change the baseline performance envelope but provide a Phase‑2 pathway for higher thrust density and more precise plume shaping.

In augmentation mode, GREMN improves the performance of Hall thrusters, ion engines, MPD thrusters, chemical rockets, and nuclear‑thermal systems. Hall thrusters gain 18–28 percent thrust, 10–18 percent specific impulse, and 40–70 percent breathing‑mode suppression. Ion engines gain 8–15 percent thrust through space‑charge relief. MPD thrusters gain 12–22 percent thrust and significantly reduced electrode erosion. Chemical and nuclear‑thermal systems require only modest RF pre‑ionisation to reach the conductivity needed for coupling.

GREMN is designed for long operational life because all hardware sits outside the plasma. A three‑phase validation pathway is defined, progressing from laboratory breadboard to integrated ground test and finally to a Low Earth Orbit flight demonstration.