Last year, NASA’s advanced propulsion research wing made headlines by announcing the successful test of a physics-defying electromagnetic drive, or EM drive. Now, this futuristic engine, which could in theory propel objects to near-relativistic speeds, has been shown to work inside a space-like vacuum.

Illustration: “Dreamscape IV,” by jamajurabaev, via Deviantart

NASA Eagleworks made the announcement quite unassumingly via There’s also a major discussion going on about the engine and the physics that drives it at the site’s forum.

COMSOL Magnetic Field Surface Distribution (NASA Eagleworks).

The EM drive is controversial in that it appears to violate conventional physics and the law of conservation of momentum; the engine, invented by British scientist Roger Sawyer, converts electric power to thrust without the need for any propellant by bouncing microwaves within a closed container. So, with no expulsion of propellant, there’s nothing to balance the change in the spacecraft’s momentum during acceleration. Hence the skepticism. But as stated by NASA Eagleworks scientist Harold White:



[T]he EM Drive’s thrust was due to the Quantum Vacuum (the quantum state with the lowest possible energy) behaving like propellant ions behave in a MagnetoHydroDynamics drive (a method electrifying propellant and then directing it with magnetic fields to push a spacecraft in the opposite direction) for spacecraft propulsion.

The trouble with this theory, however, is that it might not work in a closed vacuum. After last year’s tests of the engine, which weren’t performed in a vacuum, skeptics argued that the measured thrust was attributable to environmental conditions external to the drive, such as natural thermal convection currents arising from microwave heating.

The recent experiment, however, addressed this concern head-on, while also demonstrating the engine’s potential to work in space. (Image: NASA Eagleworks.)


The group has given consideration to whether the experimental measurements of thrust force were the result of an artifact. Despite considerable effort within the forum to dismiss the reported thrust as an artifact, the EM Drive results have yet to be falsified.

After consistent reports of thrust measurements from EM Drive experiments in the US, UK, and China – at thrust levels several thousand times in excess of a photon rocket, and now under hard vacuum conditions – the question of where the thrust is coming from deserves serious inquiry.

Serious inquiry, indeed. It’s crucial now that these tests be analyzed, replicated, and confirmed elsewhere. A peer-review and formal paper would also seem to be in order lest we get too carried away with these results. But wow. Just wow.


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It’s still early days, but the implications are mind-boggling to say the least. A full-fledged EM drive could be used on everything from satellites working in low Earth orbit, to missions to the Moon, Mars, and the outer solar system.

(Image: Mark Rademaker)

EM drives could also be used on multi-generation spaceships for interstellar travel. A journey to Alpha Centauri, which is “just” 4.3 light-years away, suddenly wouldn’t be so daunting. An EM drive working under a constant one milli-g acceleration would propel a ship to about 9.4% the speed of light, resulting in a total travel time of 92 years. But that’s without the need for deceleration; should we wish to make a stop at Alpha Centauri, we’d have to add another 38 years to the trip. Not a big deal by any extent of the imagination.



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