NASA publishes peer-reviewed paper on ‘lawbreaking’ EM drive

After months of speculation and leaked reports, the NASA Eagleworks Laboratory team has finally published a peer-reviewed paper detailing the highly-anticipated EM Drive propulsion system, and by all accounts, the so-called lawbreaking engine actually appears to work.

First proposed by British scientist Roger Shawyer in 1999, the EM Drive (the ‘EM’ stands for ‘electromagnetic’) has been called an “impossible” fuel-free propulsion system which converts electricity into microwaves, then shoots it inside of a closed, cone-shaped chamber, exerting a greater amount of force on the cone’s flat end and ultimately generating thrust.

Since the microwaves would be powered by solar energy, the EM Drive would not require the use of a propellant, meaning that spacecraft and satellites could be far smaller and lighter than in the past (since they would not need to carry large amounts of fuel into space. It would also allow manned space flights to be completed far more quickly than ever before, at least in theory.

Critics had dismissed the idea as highly implausible, claiming that Shawyer’s hypothesis would violate the laws of physics, because in order for a thruster to gain momentum in one direction, a propellant had to be expelled in the opposite direction. Because the EM Drive is a closed system that uses no fuel, they argued, its function may violate the law of the conservation of momentum by generating a forward thrust with no accompanying equal and opposite force.

Now, with the publication of the peer-reviewed study, the propulsion system “really does appear to work,” according to ScienceAlert’s Fiona MacDonald. Furthermore, the Eagleworks team has “even put forward a hypothesis for how the EM Drive could produce thrust,” she added, pointing out that the EM Drive concept somehow “continues to work” in “test after test.”

Controversial pilot-wave theory may explain how it operates

The newly-released paper, which will be published next month in the Journal of Propulsion and Power, concluded that the EM Drive was capable of generating a consistent 1.2 millinewtons per kilowatt of thrust (plus or minus 0.1 mN/kW) in a vacuum, “which was very close to the average impulsive performance measured in air,” according to the ScienceAlert report.

Comparatively, 1.2 millinewtons per kilowatt of thrust isn’t much. As MacDonald explained, the Hall thruster generates more than 50 times that amount. However, since the Hall thruster requires the use of fuel, which would add additional weight as cargo during a spaceflight, the authors said that those higher thrust levels might not be as beneficial as they might appear.

When compared to solar sails, which like the EM Drive would use solar panels to produce all of the microwaves needed for thrust without using propellant, the so-called impossible engine fairs much better. Solar sails, MacDonald said, generate a force of 6.67 micronewtons per kilowatt – or two orders of magnitude less than what the EM Drive is capable of, according to the study.

The Eagleworks team also said that they were not looking to optimize the performance of the EM Drive during their tests, only to prove that it actually worked. What that means is that the engine could actually be even more efficient than the initial tests indicate. What the new study doesn’t reveal, however, is just how the device works without breaking the laws of physics.

The authors did offer one hypothesis, though: “The supporting physics model used to derive a force based on operating conditions in the test article can be categorized as a nonlocal hidden-variable theory, or pilot-wave theory for short,” they wrote. Essentially, pilot-wave theory says that particles do not have precise positions at all times, and while it is controversial, it has been accepted by more and more physicists in recent years, MacDonald wrote.

“If a medium is capable of supporting acoustic oscillations,” the authors said, “this means that the internal constituents were capable of interacting and exchanging momentum. If the vacuum is indeed mutable and degradable as was explored, then it might be possible to do/extract work on/from the vacuum, and thereby be possible to push off of the quantum vacuum and preserve the laws of conservation of energy and conservation of momentum.”

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Image credit: NASA Eagleworks

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