NASA has successfully ignited a prototype magnetoplasmadynamic thruster powered by lithium metal vapor, reaching 120 kilowatts in a ground test at the Jet Propulsion Laboratory — the highest power level ever achieved in a U.S. electric propulsion test and the first time an electromagnetic thruster of this type has been fired at this scale domestically.

The test, conducted at JPL’s Electric Propulsion Lab, marks a pivotal milestone for NASA’s Space Nuclear Propulsion project, which is developing a megawatt-class nuclear electric propulsion system intended to support crewed missions to Mars.

What was tested and how

Engineers placed the prototype inside a 26-foot-long (8-meter) water-cooled vacuum chamber designed to replicate the near-vacuum conditions of deep space. Over five ignitions, the thruster was brought up to power, reaching temperatures exceeding 5,000 degrees Fahrenheit (2,800 degrees Celsius).

The thruster’s nozzle-shaped outer electrode emitted a vibrant red plume visible during the test, while the tungsten electrode at the center glowed bright white under the extreme thermal load — visual confirmation the system was operating at the target power levels.

James Polk, senior research scientist at JPL and a lead on the project, described the moment as a critical payoff for two and a half years of development work conducted in collaboration with Princeton University and NASA’s Glenn Research Center.

The team not only demonstrated the thruster works, Polk said, but hit the power levels it was targeting — and now has a validated testbed to begin addressing the challenges of scaling further.

Why lithium and why MPD

The magnetoplasmadynamic — or MPD — thruster is a fundamentally different class of electric propulsion than the ion engines and Hall-effect thrusters currently flying on missions like the Psyche asteroid probe. Those systems use solar power and ionized inert gas, and are effective but limited in the power they can process.

The MPD thruster uses high electrical currents interacting with a magnetic field to electromagnetically accelerate lithium plasma — a process that allows it to operate at substantially higher power densities while using propellant far more efficiently than chemical rockets.

NASA says electric propulsion systems of this class use up to 90% less propellant than traditional chemical rockets. When paired with a nuclear power source — which can supply the sustained high currents an MPD thruster requires without dependence on solar energy, which weakens dramatically beyond the inner solar system — the combination becomes compelling for deep-space human missions where trip time and launch mass both carry enormous cost and safety implications.

The 120 kW achieved in this first test is already more than 25 times the power output of the Hall-effect thrusters aboard the Psyche spacecraft. But it is only the beginning of what the program needs.

The road to megawatt-class

NASA’s target for a Mars mission architecture requires between 2 and 4 megawatts of total propulsion power, necessitating multiple MPD thrusters operating in parallel for more than 23,000 continuous hours. The next phase of testing will push individual thrusters toward 500 kilowatts to 1 megawatt — a range that introduces serious thermal management challenges. At those power levels and durations, the hardware faces sustained extreme temperatures that the team must now prove the thruster’s components can endure.

The program fits squarely within NASA Administrator Jared Isaacman’s stated priority of keeping Mars firmly in view. The successful test, Isaacman said, demonstrates real progress toward sending an American astronaut to set foot on the Red Planet.