Recap of the Second Sublimation and Glow Discharge Ionization Test of Adamantane in Vacuum

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Last night I ran the second ever sublimation and glow discharge ionization test of Adamantane in vacuum for the AIS-ADAMANT Series development, exploring the use of this highly experimental fuel for low-power micro-ion and plasm thrusters. Details of the first test and test setup can be found in my previous post HERE.

For this test, the setup was the same as the first. However, the damaged 2W 1.5kV supply was swapped out for a 2W 3kV supply to power the discharge. Fuel was loaded up into the test cell the same as the first test, and connections were the same. The major goal of this test was to see if I could achieve ionization of the Adamantane on the purely passively sublimated vapors from the test cell without any heater power applied.

Pumpdown was the same as the first test, with the system bottoming out at the mid-10^-4 Torr level. The HV supply was turned up to 1.5kV, and a faint glow discharge was observed. Power at this point was only 0.75W, and the temperature of the chamber was only 11-12C.

Power was increased to 0.97W at over 2kV on the test cell. Power was eventually raised to 2W at 2.3kV on the test cell. Power was cycled on and off, with smooth and reliable re-ignition. Video of the discharge during the test can be seen below.

This second test ended up successfully validating the observations of my first test, with very low temperature sublimation of Adamantane and stable discharge at low power levels of 2W and less. During this test I achieved stable discharge purely from natural sublimation without the heater. Adamantane not only sublimates far easier than I was ever expecting, but it is very easy to ionize. This has massive implications. The chamber was between 11-15C during the test. Even at this low temp, the Adamantane sublimated enough to achieve stable discharge without heater power. This means that required heater power for sublimation is far less than I was expecting. However, because it sublimates so well, too well in fact that I have no choice but to implement some valving in my design, which adds a whole new layer of complexity. I was hoping to avoid this aspect of the system design, but unfortunately I have no choice.

Despite this, I finally have a solution for a unpressurized fuel for conventional EP which I spent a year searching for and reviewing on the side. This kicks the ADAMANT Series development into full-throttle, and I will be able to push forward even further on the newest thruster designs utilizing this unconventional fuel source.