Thrust and efficiency of the K-III MPD thruster

A qqasisteady multimegawatt magnetoplasmadynamic (MPD) thruster, Koniaba III, has been investigated to obtain fundamental thruster characteristics. The data presented in this paper are obtained with various propellants (Ar, NH3, He, and H2) for discharge currents ranging between 3 and 25 kA. Three different mpdes, diffuse, spot, and gross erosion, are found to exist in an MPD arc and a qualitative explanation of their nature is presented. Cathode and anode erosion are discussed and a preferred operating current for the thruster is identified at a current just below a limiting value, defined by electrode erosion. Thrust efficiencies are found to increase with specific impulse, reaching values of 32% at 4500 s for hydrogen propellant and 21% at 2500 s for ammonia.