CURRENT DISTRIBUTION IN THE CATHODE AREA OF AN ARCJET

A theoretical model of the electrode phenomena, leading to the computation of the current density distributions, arc spot temperature, spot size, sheath voltage, ablation velocity, and ablation rates, is put forward. Computations for an atmospheric arc, at load currents ranging from 800 to 3000 A, in 1) one segment, and 2) four segment electrode configurations, are conducted. Spot size seems to vary linearly with load current, ranging from 1.82 to 3.22 mm for a rotating arcfoot, as the load current is varied from 800 to 3000 A. Even with arcfoot rotation, spot temperatures are high enough to cause ablation of the electrode material. Computations for P = 50 atm and I = 6000 A reveal that arc rotation is even more essential in order to save the excessive material ablation. In order to achieve an acceptable level of material ablation at P = 50 atm and I = 6000 A. a rotational frequency of 300-400 Hz needs to be achieved.