Spectroscopic plasma emission from a pulsed plasma thruster with asymmetric electrodes

In recent years, there has been significant interest in small lightweight satellites. The miniaturization of technology has resulted in the development of small satellites that can weigh less than 50 kg. Of these, those following the CubeSat architecture can weigh as little as several kg. Unfortunately, while the miniaturization of electronic systems has resulted in the miniaturization of such satellites, they are still limited by the lack of suitable micropropulsion systems. More mature systems such as ion thrusters and Hall thrusters exhibit considerable losses when scaled down in size, and also experience a hard limit in their miniaturization due to certain essential components. The pulsed plasma thruster (PPT) is a possible solution to the lack of a suitable micropropulsion system. These are structurally simple forms of electric propulsion that can scale down extremely well. However, while they may be structurally simple, the underlying plasma physics can be extremely complex due to the ablation process coupled with electromagnetic plasma acceleration due to the self-induced Lorentz force. Geometric parameters have previously been found to affect the performance of a PPT, but no detailed fundamental explanation as yet links empirical studies with fundamental physics. It is important to further study the resulting plasma parameters in addition to performance measurements in order to build a more general fundamental model of the PPT. Such understanding would be able to better direct research and development in the future. More recently, an asymmetric electrode configuration has been found to increase the performance of the PPT. Such asymmetry can affect both the current density of the discharge arc and the plasma acceleration processes. Here, we studied the spectral emission from a prototype PPT with varying asymmetric electrode configurations in order to identify how the emission of light from plasma components changes as asymmetry is introduced in the electrode configuration. From these measurements, it is also possible to estimate plasma parameters such as the electron density and electron temperature, in order to better understand how the plasma profile is affected by the electrode configuration.