The most powerful electric thruster currently operating on a NASA spacecraft draws about 4.5 kilowatts as it pushes Psyche toward a metal-rich asteroid. In February 2026, JPL fired a different lithium-fed prototype at 120 kilowatts—more than 25 times the input power—and engineers now want to scale a single thruster to one megawatt.

On 24 February 2026, a new electric thruster came to life five times inside an eight-metre vacuum chamber at NASA’s Jet Propulsion Laboratory. Its central tungsten electrode glowed white at more than 2,800 degrees Celsius, and a red plume spread from the mouth of the machine. At its highest setting, the prototype drew 120 kilowatts of electrical power.

The immediate comparison is a spacecraft already at work. NASA’s Psyche mission is cruising towards a metal-rich asteroid with the highest-power electric thrusters currently operating on one of the agency’s spacecraft. The active Hall-effect thruster draws about 4.5 kilowatts at the reference level behind JPL’s comparison. The laboratory machine therefore operated at more than 25 times that power.

JPL’s engineers now want to test a single thruster at between 500 kilowatts and one megawatt. That final number is roughly 222 times Psyche’s 4.5-kilowatt benchmark and 8.3 times the February test. It is also a target, not an accomplished engine specification.

That distinction is the centre of this story. The JPL announcement issued on 28 April described an initial laboratory test, not an endurance run, a flight qualification or a measured journey to Mars. The experiment matters because it opens a credible route to much higher-power electric propulsion. It does not yet show that the complete route can be travelled.

A kilowatt is not a unit of thrust

Power and thrust are related, but they are not interchangeable. A kilowatt measures how quickly electrical energy enters the propulsion system. Thrust measures force. Two engines can draw the same power while producing different combinations of thrust and exhaust velocity, depending on their efficiency, propellant and design.

This is why the 120-kilowatt figure should not be read as an engine pushing 26.7 times harder than Psyche. JPL did not publish a complete performance table with the April release. It did not state the prototype’s measured thrust, efficiency or specific impulse at 120 kilowatts. Those quantities will be essential before anyone can translate the power level into a useful spacecraft design.

The distinction also prevents a familiar mistake in spaceflight reporting. A higher-power electric thruster does not by itself produce a particular Mars travel time. Mission duration depends on vehicle mass, total thrust, propellant loading, exhaust velocity, duty cycle, departure orbit, arrival requirements and the mass of the power system feeding the engines.

The clean conclusion is narrower. JPL operated a type of electric thruster at an input power far above any electric engine currently flying on a NASA spacecraft. That is a real hardware result. The mission performance that could eventually follow remains to be demonstrated.

Psyche shows what flight-proven electric propulsion can do

Psyche carries four Hall-effect thrusters, arranged in two pairs, but operates only one at a time. Large solar arrays provide electricity. The engine uses electric and magnetic fields to ionise xenon gas and accelerate the charged atoms away from the spacecraft, producing a blue plume and a reaction force in the opposite direction.

The force is slight. NASA’s Psyche spacecraft description gives a maximum of 240 millinewtons, comparable to the weight of an AA battery resting on a hand. A chemical rocket would find that useless for leaving a launch pad. In space, where the engine can keep operating and there is no atmospheric drag, the small acceleration accumulates.

Electric propulsion buys that persistence by using propellant efficiently. Psyche expels xenon at high speed and consumes only about 0.35 to 1.3 kilograms a day, depending on the power level. It can spend much of its interplanetary cruise thrusting, although available solar power declines as the spacecraft moves farther from the Sun.

The mission also shows why engines are only one part of a trajectory. SpaceDaily previously examined how Psyche used Mars as a gravitational slingshot in May 2026. Its Hall thruster supplies sustained control and velocity change; planetary geometry supplied a separate, propellant-free boost. No single propulsion number tells the whole mission story.

The MPD prototype is a different kind of engine

JPL’s laboratory device is a lithium-fed magnetoplasmadynamic thruster, usually shortened to MPD. The technology has been studied since the 1960s but has never flown operationally. It belongs to the broad family of electric propulsion, yet it does not simply enlarge Psyche’s Hall thruster.

The engine turns lithium metal into vapour and then plasma, a gas whose atoms have been stripped into charged particles. Very high electric currents pass through that plasma. Their interaction with a magnetic field creates an electromagnetic force that accelerates the plasma out of the thruster.

This arrangement is attractive at high power because it may process far more electricity through one thruster than today’s flight systems while still using propellant efficiently. If the promised performance survives longer tests, a vehicle could obtain substantially more electric thrust without assembling an impractically large bank of small engines.

Potential is doing important work in that sentence. MPD physics is well established, but a useful spacecraft engine must do more than accelerate plasma for a short test. It must feed lithium predictably, maintain a stable discharge, limit erosion, control unwanted deposits, survive thermal cycling and work with flight-weight power electronics.

Five ignitions established a starting point

The February campaign took place in JPL’s condensable metal propellant facility, known as CoMeT. The water-cooled vacuum chamber is 26 feet, or eight metres, long and is designed to contain tests involving metal vapours at power levels that may eventually reach the megawatt class.

That facility is part of the result. High-power electric propulsion cannot be tested simply by turning on an engine in an ordinary room. The chamber must reproduce a sufficiently thin vacuum, handle the plume, protect diagnostic equipment and remove a large amount of heat without distorting the measurements.

Across five ignitions, the new thruster reached the team’s intended power level of up to 120 kilowatts. JPL senior research scientist James Polk said the firing showed both that the thruster worked and that the testbed could support the scaling work ahead. The laboratory’s Electric Propulsion Group exists partly to make that transition from experimental concept to a system mission designers can evaluate.

Five starts are not 23,000 hours of operation. The test did not show that the engine could run through years of cumulative use, survive thousands of thermal cycles or restart after a long coast in deep space. It established the first point on an engineering curve whose difficult end is endurance.

One megawatt is more than an eightfold scale-up

Moving from 120 kilowatts to one megawatt means putting 8.3 times as much input power through a single thruster. In a simple drawing, the engine only becomes larger. In hardware, every current path, magnetic field, propellant channel, seal, electrode, insulator and cooling boundary must cope with a harsher operating environment.

The scale-up may not be linear. A component that remains cool enough during a brief 120-kilowatt pulse can overheat during a longer firing. Plasma may distribute itself differently at higher current. Erosion that looks trivial across five starts can remove unacceptable amounts of material over tens of thousands of hours.

The power-processing equipment must scale too. A spacecraft cannot connect a reactor or solar array directly to a thruster and hope for the correct current. Converters, switches and control electronics have to condition the supply, start and throttle the discharge, isolate faults and continue operating around intense electromagnetic fields.

JPL’s planned 500-kilowatt and one-megawatt tests should therefore be read as development steps. Reaching the number for a moment would be useful. Holding a stable operating point, measuring thrust and efficiency, inspecting wear, and repeating the result would be much more informative.

Heat and lifetime are the unforgiving tests

The February photographs make the thermal problem visible. The central tungsten electrode exceeded 5,000 degrees Fahrenheit, or 2,800 degrees Celsius. Tungsten is used because ordinary metals would fail far sooner, but even refractory materials erode, crack or change properties under prolonged heat and plasma exposure.

Space makes heat rejection harder. A vacuum removes convective cooling, so a spacecraft cannot hand waste heat to surrounding air. Heat must move through the structure and eventually leave as infrared radiation from large surfaces. At megawatt scale, radiators, pumps and plumbing can become a substantial part of the vehicle.

The thruster itself would also need to operate for extraordinary periods. JPL says a human Mars application might require more than 23,000 hours, equivalent to about 2.6 years of continuous operation. A real mission could spread those hours across firings and coasts, but the cumulative wear does not disappear.

Endurance testing is slow by definition. Engineers can accelerate some damage mechanisms or inspect components after shorter runs, yet there is no complete substitute for sustained operation. A laboratory prototype can be repaired between tests. A Mars transfer vehicle cannot open its engine compartment midway through the journey.

A one-megawatt thruster needs a megawatt spacecraft

An engine that draws one megawatt is inseparable from the machine that produces and manages that electricity. JPL’s release places the MPD work within NASA’s Space Nuclear Propulsion project because crew-scale electric propulsion will probably require a compact, solar-independent source.

Nuclear electric propulsion is not the same as a nuclear thermal rocket. In the electric design, a fission reactor produces heat. A conversion system turns some of that heat into electricity. The electricity then powers the thruster, while radiators dispose of the heat that was not converted into useful electrical output. NASA’s Space Nuclear Propulsion programme treats the reactor, conversion machinery, heat rejection and electric propulsion as connected technology problems.

JPL estimates that a human Mars vehicle might need two to four megawatts in total, using several MPD thrusters. Even if one-megawatt engines become available, the spacecraft would still require multiple units for total power, control and redundancy. It would also carry a reactor, shielding, turbines or another conversion system, radiators, lithium stores and a structure capable of keeping the crew away from the reactor’s radiation.

SpaceDaily’s recent account of NASA’s planned Space Reactor-1 Freedom pathfinder illustrates the size of that gap. SR-1 is intended to test a 20-kilowatt-electric reactor system with a 12-kilowatt Hall thruster. A two-megawatt Mars vehicle would demand one hundred times that reactor output. The smaller mission could establish valuable operating experience without pretending that the crew-scale system already exists.

Why Mars appears before a Mars engine exists

Electric propulsion can use far less propellant than a chemical stage for the same broad mission task. The trade is low thrust, which means the vehicle accelerates over a long arc rather than through a brief burn. Raising electrical power offers a route to more thrust while retaining much of electric propulsion’s propellant advantage.

That combination is attractive for Mars because crewed vehicles and their supplies are heavy. Reducing propellant mass can free launch capacity for habitats, shielding, consumables and abort margins. Greater thrust can also make an efficient trajectory less slow than it would be with today’s kilowatt-class engines.

None of this supplies a transit duration from the February firing. JPL said the technology could support human missions, not that the prototype had completed a simulated voyage or proven a particular schedule. Travel time will emerge only when engineers can place measured thruster performance inside a complete vehicle model with realistic reactor, radiator and payload masses.

Chemical propulsion would still be needed for jobs requiring high thrust, especially launch from Earth. A future mission may combine systems, using chemical stages where immediate force is essential and nuclear electric propulsion where months of efficient acceleration are valuable. The most useful architecture may be a partnership rather than a winner replacing every other engine.

What evidence should come next

The next tests can answer questions the 120-kilowatt headline cannot. How much thrust did the engine produce? What was its efficiency? How steadily did it feed lithium? Where did material erode or condense? Did repeated starts change performance? How did the chamber measurements distinguish engine behaviour from test-facility effects?

Longer firings at the existing level would establish a baseline before power rises. Tests at 500 kilowatts and one megawatt would then show whether performance scales as hoped. Component inspections could reveal which parts set the lifetime limit, while increasingly flight-like electronics would expose integration problems early.

After that would come a full subsystem demonstration and, eventually, a flight experiment. The thruster would need to operate with its actual power processor, propellant feed and thermal hardware in a package light enough to launch. Qualification would have to address vibration, radiation, vacuum, cold starts, fault recovery and the impossibility of routine maintenance.

The February test deserves attention precisely because it made one part of this chain physical. A lithium-fed MPD thruster was built, fired and taken to 120 kilowatts in a facility prepared for higher power. The remaining chain is still long.

A large number with a carefully limited meaning

Psyche provides the useful reality check. Its roughly 4.5-kilowatt Hall thruster is not powerful by terrestrial standards, yet it is flight hardware operating far from Earth on a mission due to reach its asteroid in 2029. Reliability, power availability and years of controlled operation matter as much as the largest number reached during a ground test.

The JPL prototype points towards a different class of vehicle. At 120 kilowatts, it has already moved high-power lithium MPD propulsion from design work into a serious test campaign. At one megawatt, if efficiency and lifetime follow, a single engine could offer capabilities well beyond today’s electric spacecraft.

The words “if” and “follow” cannot be removed yet. Five ignitions showed that the thruster can start and reach its first intended power level. The next task is to turn a bright red moment in a water-cooled chamber into thousands of quiet, repeatable hours. That is the distance between a powerful experiment and an engine trusted to push people towards Mars.