Discharge frequency improvement of Vacuum Arc Thruster with plasma interaction ignition

In recent years, the demand for CubeSAT, such as units measuring 10 cm on a side, has been increasing due to their advantages of low cost and short development time. Solid propellant electric propulsions are suitable for CubeSAT because it does not require gas cylinders or valves and can reduce the occupied volume. The one of the electric propulsions with solid propellant is Vacuum thruster. This study focuses on the development of a Vacuum Arc Thruster with plasma interaction ignition (VAT-pi2), which can be further miniaturized by adopting a passive ignition method. However, previously developed VATs have exhibited a low discharge frequency. Previous research has demonstrated that incorporating water into the thruster using sodium polyacrylate can enhance discharge frequency. In this study, we modified the shape of the VAT and explored novel methods for water retention using sodium polyacrylate, evaluating their performance. Additionally, we aimed to improve discharge frequency by combining two distinct VAT shapes, representing a fundamentally different approach from water retention. The discharge frequency was enhanced from 0.03 Hz to 0.28 Hz at a negative voltage of − 800 V. The results indicated that coating the thruster with modified epoxy spray could retain some moisture even in a vacuum, thereby maintaining a high discharge frequency. Furthermore, it was discovered that combining two types of VAT shapes significantly enhanced discharge frequency without the incorporation of water. The discharge frequency was elevated to 0.6 Hz, surpassing the target frequency of 0.33 Hz.