To view the test, Polk peered through a small portal into the 26-foot-long (8-meter-long) water-cooled vacuum chamber. Inside, the thruster flared to life, its nozzle-shaped outer electrode glowing incandescent as it emitted a vibrant red plume. Polk has researched lithium-fed MPD thrusters for decades, having worked on NASA’s Dawn mission and the agency’s Deep Space 1, the first demonstration of electric propulsion beyond Earth orbit.
The team aims to reach power levels between 500 kilowatts and 1 megawatt per thruster in coming years. Because the hardware operates at such high temperatures, proving the components can withstand the heat over many hours of testing will be a key challenge. A human mission to Mars might need 2 to 4 megawatts of power, requiring multiple MPD thrusters, which would have to operate for more than 23,000 hours.
Lithium-fed MPD thrusters have the potential to operate at high power levels, use propellant efficiently, and provide significantly greater thrust than currently flying electric thrusters. Fully developed and paired with a nuclear power source, they could reduce launch mass and support payloads required for human Mars missions.
The MPD thruster work, in development for the past 2½ years, is led by JPL in collaboration with Princeton University in New Jersey and NASA’s Glenn Research Center in Cleveland. It is funded by NASA’s Space Nuclear Propulsion project, which in 2020 began supporting a megawatt-class nuclear electric propulsion program for human Mars missions by focusing on five critical technology elements, of which the electric propulsion subsystem is one. The project, based at the agency’s Marshall Space Flight Center in Huntsville, Alabama, is part of the NASA’s Space Technology Mission Directorate.
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