Propellant Surface Evolution of a Coaxial Pulsed Plasma Thruster

Coaxial pulsed plasma thrusters are suitable for small satellites. In such thrusters, the discharge is radially nonuniform, which leads to an ablation nonuniformity that causes variations in the propellant surface. This paper describes a study of the propellant profile and ablated mass bit (i.e., mass ablated from the propellant in each discharge) of a coaxial pulsed plasma thruster over 100,000 discharges. The results show that the ablated mass bit of the thruster increases initially before becoming confine within a certain range. The ablated mass bit is less than 2.5 μg over the first 2000 discharges, and then stabilizes at 4–7 μg when the number of discharges exceeds 5000. In addition, the propellant profile changes over the 100,000 discharges, and the maximal concave depth remains less than 3 mm. Visual observations show that the area of carbon deposition is relatively large at a low discharge number. The propellant ablation area is an important factor in the ablated mass bit, because its variation is similar to that of the ablated mass bit during the continuous discharge process.