14. Are the vacuum pumping requirements for testing a VASIMR® engine the same as for other electric propulsion devices?
No. The vacuum requirements for testing a VASIMR® engines on the ground at high power are much easier to satisfy than for most other electric propulsion (EP) devices because VASIMR® engines use radio frequency (RF) rather than direct current (DC) power to interact with the plasma. The vacuum surrounding a VASIMR® engine's RF circuitry can be isolated from the relatively high-pressure plasma region because power enters the plasma through vacuum-tight dielectric windows. No such isolation is possible for DC EP devices like Hall thrusters and ion engines because they use DC acceleration with high voltage electrodes in direct contact with the plasma. Vacuum processes for VASIMR® engines are also simplified because they typically use readily available argon or krypton propellants rather than exceedingly rare xenon. For high power testing, the cost of the xenon propellant itself requires the addition of vacuum recovery equipment to trap and purify the xenon for reuse. That equipment is not typically necessary for cost effective testing of a VASIMR® engine.