It is now official, the propellantless engine known as EmDrive seems to actually work. A few months ago, it was announced that a peer-reviewed paper on the EmDrive was accepted for publication in the Journal of Propulsion and Power, and it is now available for anyone to read on the Internet. 

The paper is authored by Harold White and six other engineers and scientists from NASA's Eagleworks Laboratory. It shows that the EmDrive produces 1.2 millinewtons per kilowatt of power supplied. 

"Thrust data from forward, reverse, and null suggests that the system is consistently performing with a thrust to power ratio of 1.2 ± 0.1 millinewtons per kilowatt," the team wrote in the paper's abstract.

In the paper, the team detailed how they carefully tried to account for many potential sources of error, and they have shown that the EmDrive does indeed work.

"The test campaign included a null thrust test effort to identify any mundane sources of impulsive thrust; however, none were identified," they added. 

The thrust value might seem small at first, even compared to low-thrust spacecraft like NASA's Dawn, which has a thrust-to-power ratio of about 60 millinewtons per kilowatt. However, the EmDrive has an advantage: It doesn’t require a propellant.

And that’s the controversial property of the EmDrive. It appears to be producing a reaction without the need for an action, violating Newton’s third law of dynamics. The engine is a conical copper container that generates thrust when filled with microwaves.

It is still not clear where the propulsion comes from, though the researchers believe that the force is the measurable reaction to the oscillating microwave photons in a quantum vacuum field.

Their explanation requires an uncommon and hardly accepted interpretation of quantum mechanics, known as the realist interpretation. This view states that the probabilistic measurements we obtain from quantum mechanics is due to the combination of a real particle that has a perfectly determined path and velocity and a “pilot wave” that generates the probabilities we observe.

These ideas have been discussed since the inception of quantum mechanics, and even Einstein claimed that there must be some "hidden variables" inside quantum mechanics. The hidden variable theory was shown to be less likely than one chance in 170 million.

Another paper, published in June, suggests that the cause for the thrust has to do with the shape of the cavity and the energy of the photons. The researchers, who are unaffiliated with the EmDrive team, suggest that photons interact with themselves in a destructive way and that the conical structure creates an imbalance of photons on one side, thus producing thrust.

More experiments will be necessary to confirm the findings, but this could revolutionize interplanetary space travel.