Arcjet anode

There is disclosed an anode for an arcjet thruster which resists erosion during start-up on constriction during steady-state operation. The anode includes a converging upstream portion, a diverging downstream portion and a constricted portion disposed therebetween. In one embodiment of the invention, rails formed in the constricted portion accelerate the passage of an arc during start-up reducing erosion. In a second embodiment, a higher strength material resists bulging as a result of the thermal gradient within the nozzle.