PASADENA — The number is 120 kilowatts. That is what matters here.
Engineers at NASA’s Jet Propulsion Laboratory ran an experimental magnetoplasmadynamic thruster at that power level. The engine runs on lithium. It turns the metal into plasma. Then magnetic fields accelerate it. This is not a tweak on existing tech. It is a fundamentally different approach to moving a spacecraft.
For context, electric thrusters on current missions — like the one pushing NASA’s Psyche asteroid probe — operate at far lower power. Psyche’s Hall-effect thrusters run in the kilowatt range. The MPD thruster hit 120 kilowatts in testing. That is a jump. A real jump.
The goal is old and simple: combine the raw push of chemical rockets with the fuel-sipping efficiency of electric propulsion. Chemical rockets burn through propellant fast. They get you off the ground. But for deep space, they are wasteful. Electric thrusters sip fuel. They can run for years. But they produce barely any thrust. The MPD design aims to bridge that gap.
Lithium is the key. The metal ionizes easily. It produces dense plasma. The magnetic field shapes and accelerates that plasma. The result is a thruster that can, in theory, deliver high specific impulse — the measure of fuel efficiency — while also generating meaningful thrust. That combination has been a long-standing target for engineers working on deep-space travel.
But 120 kilowatts is not enough. A crewed Mars mission would need megawatt-scale power. That is orders of magnitude more. The thruster would also have to run continuously for years. No prototype has done that. The technology remains early-stage. The test is a step, not a finish line.
The work is part of a broader push across NASA and other agencies to develop next-generation electric and plasma engines. Missions beyond low Earth orbit demand propulsion that does not force a choice between speed and efficiency. The MPD thruster is one candidate. There are others. But the lithium-fueled design has a particular advantage: the propellant is dense. You can store more of it in less space. That matters when every kilogram on a spacecraft is budgeted.
What comes next is critical. The engineers at JPL will need to scale the thruster up. They will need to run it longer. They will need to solve the thermal management problems that come with megawatt-level plasma. The materials inside the thruster take a beating. Lithium plasma is hot. It is corrosive. The magnetic field must be strong and stable.
None of this is easy. That is why no one is claiming a breakthrough. The test is a milestone. It proves the concept works at a meaningful power level. It does not prove the concept works for a Mars mission. That remains years off.
But the trajectory is clear. Faster transit times to Mars would reduce astronaut exposure to radiation. They would cut the supplies needed. They would open the door to more ambitious exploration. The propulsion system is the bottleneck. The MPD thruster, if it can be scaled and sustained, could break that bottleneck.
For now, the engineers have a working prototype at 120 kilowatts. They have a design that runs on lithium. They have a path forward. The rest is engineering. Hard engineering. But engineering that now has a concrete data point to build on.
