PASADENA — A lithium-fed plasma engine at NASA’s Jet Propulsion Laboratory has hit 120 kilowatts in testing. That number matters. It is roughly ten times the power of the electric thrusters currently flying on NASA’s Psyche asteroid mission. The engine, a magnetoplasmadynamic or MPD thruster, turns solid lithium into a plasma and then flings it out using magnetic fields. The goal is a propulsion system that behaves like a chemical rocket when you need push — high thrust — but sips fuel like an electric engine over the long haul. That combination has been a holy grail for deep-space travel for decades.
The 120-kilowatt mark is a milestone, but it is also a reality check. A crewed Mars mission, the kind NASA has been sketching for years, would need engines running at megawatt scale — a thousand kilowatts or more. And those engines would have to fire continuously for years, not just in short test bursts. The prototype tested at JPL is an early step. It proves the concept can scale beyond the low-power electric thrusters used on probes and satellites. But the gap between 120 kilowatts and a megawatt-plus is not a straight line. It is a chasm.
Still, the test signals a shift in how engineers think about getting to Mars. Chemical rockets get you off the ground fast but burn through propellant at a furious rate. Electric thrusters, like the ion engines on NASA’s Dawn mission or the Hall-effect thrusters on Psyche, are incredibly fuel-efficient but produce only a gentle push — think of a leaf being nudged by a breeze. An MPD thruster running on lithium sits between those two extremes. It can generate more thrust than an ion engine while still using propellant far more efficiently than a chemical rocket. The result: shorter transit times to Mars, which means less radiation exposure for astronauts and fewer supplies needed en route.
Lithium was chosen as propellant for a reason. It ionizes easily — that is, it turns into plasma with less energy input than other candidate fuels. And it stores as a solid, which is simpler and safer than handling high-pressure gases. The thruster works by feeding lithium vapor into a chamber, zapping it with an electric current to strip electrons off the atoms, and then accelerating the resulting plasma with a magnetic nozzle. No moving parts. No combustion. Just fields and current.
The broader push for next-generation electric and plasma engines is not new. NASA has been funding research into advanced propulsion for years, from VASIMR to electrodynamic tethers. The MPD thruster is one of several contenders. What sets this test apart is the power level. 120 kilowatts is not a lab curiosity. It is a machine that could, with further development, actually push a spacecraft. The next steps will be about durability and continuous operation. Can the thruster run for months without the electrodes eroding? Can the thermal management system handle the heat of megawatt-class operation? Those are engineering problems, not physics problems. Hard problems, but solvable ones.
If the MPD thruster does scale to megawatt power, the implications go beyond Mars. Faster propulsion opens up the outer solar system. Jupiter’s moon Europa, Saturn’s moon Enceladus — places where scientists suspect oceans of liquid water exist beneath icy crusts — become more accessible. Robotic missions could reach them in years rather than decades. Crewed missions become conceivable, not just aspirational.
For now, the JPL test is a data point. A good one. But the road from a laboratory prototype to a spacecraft engine bolted onto a Mars-bound ship is long. The lithium-fed MPD thruster has cleared one hurdle. Many more remain.
