Effects of Applied Magnetic Fields on Performance of a Quasisteady Magnetoplasmadynamic Arc

A quasisteady magnetoplasmadynamic arcjet with applied magnetic fields was studied to clarify the influence of axial magnetic fields on the thruster performance and the discharge feature. Pulsed axial magnetic fields were applied by a few-turn coil, which was connected with a pulse-forming network independent of the main discharge circuit. An increase in axial-field intensity raised the discharge voltages at constant discharge currents below the limiting current with H2, the mixture of N 2 + 2H 2 simulating fully decomposed hydrazine, and Ar. The thrust characteristics for H2 and the mixture of N 2 + 2H 2 showed that there was the optimum axial-field intensity with which the maximum thrust was achieved for each gas, although at low discharge current levels for H, and Ar the thrusts increased with axial-field intensity. The discharges for all gases were inclined to occur more upstream with an increase in axial-field intensity. It was inferred that these effects of axial magnetic fields on the thruster performance and the arc feature were due to the rotating motion of — Jr x Bz, i.e., swirl acceleration and enhanced thermalization.