Last night I ran a new lifetime test on the AIS-gPPT3-1C Micro Pulsed Plasma Thruster. The test was livestreamed on the AIS YouTube page, which you can view below.
The goal of the test was to repair the gPPT3 and incorporate some slight design changes from prior tests aimed to improve ignition reliability of the thruster. In this test, the modified cathode/igniter spacing was kept, and a 1/8″ thick Teflon fuel plate was used. In addition, it was decided to operate the thruster at max nominal input of 5V, which would give a charging voltage of 2kV, and a discharge energy of 0.28J. Prior testing has indicated that at lower voltages, while lifetime is better, reliability is significantly worse. At around 4V in, lifetime is around 1300 shots with a ~75% ignition reliability.
The test was set up the same as prior tests with the gPPT3. Testing was started at 8×10^-7 Torr. While the beginning of the test had a bit of a hard start, ignition became smoother after a few minutes, and the thruster operated at near 100% ignition reliability at the nominal rep rate of ~0.25Hz. However, the thruster only lasted about 500 shots before the primary capacitor bank failed which equates to roughly 30 minutes of continuous firing time, confirming increased reliability at reduced lifetime.
At this point, the key bottleneck to longer operating life is solely the capacitor bank. While PocketQube compatible systems my be limited to the current iteration, Cubesats aiming to use the gPPT3 could use the option of a larger more robust capacitor to significantly improve thruster lifetime.