The engine uses lithium metal vapor…

The engine uses lithium metal vapor and belongs to a class of technology known as magnetoplasmadynamic (MPD) thrusters. These systems create thrust by using electric currents and magnetic fields to accelerate plasma at extremely high speeds. During five separate ignitions, the thruster’s tungsten electrode glowed brilliant white as temperatures climbed above 5,000 degrees Fahrenheit (2,800 degrees Celsius). The tests were conducted in JPL’s Electric Propulsion Lab, which houses a unique facility capable of safely evaluating electric thrusters that rely on metal vapor propellants at megawatt-class power levels.