Thrust enhanced by a magnetic Laval nozzle in an applied-field magneto-plasma-dynamic thruster

The thrust imparted by an applied-field magneto-plasma-dynamic thruster is enhanced by superimposing a convergent-divergent magnetic field called a magnetic Laval nozzle. The thrust increases up to 6.9 N by increasing the magnetic field strength at the Laval nozzle throat. It is observed that the plasma flow velocity increases and the ion temperature simultaneously decreases downstream of the throat. A major component of the measured Lorentz force arising from the plasma-induced current is identified to be in the radial direction, while a significant increase in the plasma density is observed upstream of the nozzle. These results imply that the plasma pressure increases upstream of the magnetic Laval nozzle due to an inhibition of the plasma loss, which contributes to the increase of the thrust.