A magnetically-nozzled, quasi-steady, multimegawatt, coaxial plasma thruster

The Los Alamos National Laboratory Coaxial Thruster Experiment (CTX) has been upgraded to enable 10 ms quasi-steady-state (QSS) operation of magnetohydrodynamic type thrusters at power levels from 1 to 40 MW. Here we report on experimental observations and associated analysis for QSS discharges using deuterium, helium, and argon propellants. Measurements of thruster current and voltage, magnetic field fluctuations, electron density and temperature, and plasma potential indicate true quasi-steady operation over 10 ms with propellant exhaust velocities of 1-2×10⁵ m/s in helium and deuterium. The application of unique applied magnetic nozzle configurations result in a substantial reduction of the measured anode fall potential. Data analysis and analytical MHD modeling imply an impulsive start in the propellant flow that is limited to the Alfven critical ionization velocity and the presence of an effective constriction or “nozzling” in the how channel. This research indicates that efficiency optimization of MHD class thrusters will most likely occur at megawatt power levels. This implies repetitively pulsed, high-power operation for near term, low-mean-power solar electric propulsion missions