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Management of Lithium Propellant for Magnetoplasmadynamic Thrusters

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Abstract

Procedures and guidelines are presented for the safe preparation, delivery, mass flow calibration, and neutralization of lithium propellant during electric thruster ground testing. Lithium is a promising propellant for electromagnetic plasma thrusters, particularly mag- netoplasmadynamic (MPD) thrusters. Preparation is conducted in an argon-filled glovebox under positive pressure, where solid lithium is melted into a reservoir. A liquid lithium feeding procedure is described that minimizes gas entrapment and enables flow tracking via localized temperature measurements. Mass-flow calibration is performed by displacing gas-free lithium with a motorized piston into a beaker on a balance. Calibration results were within 2% of theoretical predictions. The vacuum chamber is lined with disposable aluminum foil to facilitate post-test cleanup, and neutralization is achieved by injecting water into the chamber. A survey of relevant chemical reactions and their rates allowed prediction of the maximum condensed lithium film that can be neutralized after a specified wait period. Finally, disassembled feed-system components are cleaned by soaking in water under a ventilation hood.