Demonstration of Vacuum Arc Ion Thruster Operation Using Asteroid-Derived Propellant*

Alternative propellants, such as those that could be easily extracted from asteroids, could significantly accelerate space exploration by reducing launch mass. Furthermore, due to the high price of many traditional electric propulsion fuels, alternative propellants are invaluable in their own right as cost-effective replacements. In this work a vacuum arc ion thruster - a gridded ion thruster that utilises a vacuum arc to generate plasma from solid metal for acceleration - was built and tested. This compact and low power vacuum arc ion thruster consisted of a vacuum arc thruster (VAT) plasma source, a glass plasma containment vessel and a two-grid ion acceleration system. Two different VAT plasma source configurations were tested and compared. First, a coaxial pure copper cathode VAT was tested as the plasma source in the ion thruster. Successful operation was recorded and pulsed ion beams of up to 11 mA, 3.1 keV copper ions lasting 320 microseconds were produced and detected downstream. Next, a metallic meteorite cathode was used in a planar VAT configuration as the plasma source for the ion thruster. Successful operation of this 'asteroid-fueled' ion thruster was demonstrated and pulsed ion beams of up to 11 mA, 1.7 keV meteorite (primarily iron and nickel) ions were produced. It was concluded that the vacuum arc ion thruster is a promising propulsion system due to its ability to use inexpensive solid metal propellant and be refueled from asteroidal material with little or no processing.