The plasma properties in the discharge chamber of a quasi-steady MPD thruster have been investigated to understand acceleration mechanism and to design an optimum electrode configuration. The results measured by a magnetic probe show that the current pattern depends strongly on the propellant species (Ar, H
2 and NH
3) and the parameter JJ
2/m (current squared over mass flow rate). It is found that the plasma produced in the discharge chamber is compressed radially and 50% on the input power is consumed in the cathode region for H
2 at higher currents. From floating potential and number density measurements, the positive voltage slope and propellant starvation near the anode surface are found to occur beyond the predicted critical value of JJ
2/m. With improved straight-diverging anode, satisfactory arc operation without anode erosion has been demonstrated somewhat beyond the predicted Critical Current.
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