NASA’s Lithium-Nuclear Thruster Ignites in Historic First Test

NASA engineers have successfully ignited a prototype electromagnetic thruster that could one day power human exploration of Mars. The test, conducted inside a vacuum chamber, achieved power levels of up to 120 kilowatts , the highest ever recorded in a U.S. electric propulsion test. That’s more than 25 times the power of the electric thrusters currently flying on NASA’s Psyche mission, which launched in 2023 to study a metal-rich asteroid.

“Designing and building these thrusters over the last couple of years has been a long lead-up to this first test,” said James Polk, senior research scientist at NASA’s Jet Propulsion Laboratory (JPL), in a statement. “It’s a huge moment for us because we not only showed the thruster works, but we also hit the power levels we were targeting. And we know we have a good testbed to begin addressing the challenges to scaling up.”

Electric propulsion systems work by using magnetic fields and electric currents to accelerate propellant to extremely high speeds. Compared to traditional chemical rockets, these systems can use up to 90% less propellant, according to NASA. Most current electric thrusters rely on solar power for acceleration, producing low continuous thrust over long periods. The newly tested thruster, however, runs on lithium metal vapor. Known as a lithium-fed magnetoplasmadynamic (MPD) thruster, it uses high currents interacting with a magnetic field to electromagnetically accelerate lithium plasma.

Lithium-fed thrusters have the potential to operate at high power levels while using propellant efficiently, offering greater thrust power than existing electric propulsion systems. Once fully developed and paired with a nuclear power source, the MPD could reduce launch mass and enable larger payloads for human Mars missions.

During the test, the thruster was placed inside a 26-foot-long water-cooled vacuum chamber at JPL’s Electric Propulsion Lab. Engineers fired it up and observed five ignitions, during which temperatures exceeded 5,000 degrees Fahrenheit (2,800 degrees Celsius). The thruster’s nozzle-shaped outer electrode emitted a vibrant red plume, while the tungsten electrode at its center glowed bright white.

NASA’s JPL has been developing the MPD thruster for the past two and a half years in collaboration with Princeton University and NASA’s Glenn Research Center. The work is funded by NASA’s Space Nuclear Propulsion project, with the goal of launching a human mission to Mars through a megawatt-class nuclear electric propulsion program.

“At NASA, we work on many things at once, and we haven’t lost sight of Mars,” NASA Administrator Jared Isaacman said in a statement. “The successful performance of our thruster in this test demonstrates real progress toward sending an American astronaut to set foot on the Red Planet.”

Data from this first demonstration will guide a series of upcoming tests, with the team aiming to reach power levels between 500 kilowatts and 1 megawatt per thruster in the coming years. Launching a crewed spacecraft to Mars could require 2 to 4 megawatts of power, meaning multiple MPD thrusters would need to operate for more than 23,000 hours. That presents a significant challenge, as the hardware operates at extreme temperatures, and the team must prove that the thruster’s components can withstand the heat over many hours of continuous operation.

“We will continue to make strategic investments that will propel that next giant leap,” Isaacman added.