Optimization Issues for a Micro-Pulsed Plasma Thruster

In this work we consider several issues related to design of a micro-Pulsed Plasma Thruster (mPPT). One example of such a device has been developed at the Air Force Research Laboratory for delivery of a very small impulse bit. It is concluded that the choice of the optimal energy level for a given micro-PPT geometry is very important. If discharge energy is small, the so called propellant charring would limit the operational time of the thruster. It is found that the charring phenomenon is associated with non-uniformity (in the radial direction between the electrodes) in the propellant ablation rate. On the other hand higher energy leads to discharge constriction on the positive electrode and causes azimuthal non-uniformity. Reasoning leading to such non-uniformity is considered and recommendations for optimal energy and thruster size selections are presented