“Impossible” EmDrive Engine Could Make Interstellar Travel a Reality

The EmDrive could usher in an era of interstellar voyages for human beings. Or it could be a failed experiment that unsuccessfully tried to break the laws of physics. A pair of upcoming papers may just settle that decades-long argument.

The EmDrive was first proposed in 2001 by scientist Roger Shawyer. In theory, the drive—also called a radiofrequency resonant cavity thruster—converts electricity into microwaves and forces them through a sealed cone. The microwaves would bounce around the reflective surface of the cone, and since the microwaves carry momentum, they would impart that momentum to that surface. The waves would exert more force on the larger end of the cone than the smaller one, creating enough thrust—without the need for propellant—to push a spacecraft through the vacuum of space. And, the drive could theoretically increase momentum once it starts moving.

Currently the EmDrive exists only as a laboratory prototype, and the Defense Advanced Research Projects Agency (DARPA) has provided funding for the project. Researchers, including a team from China and a team from NASA, claim to have produced thrust with the drive. If it did happen, it could revolutionize space travel.

“This is a technology which could transform space travel and see craft lifting silently off from launchpads and reaching beyond the solar system,” said Mike McCulloch, one of the leaders of DARPA’s EmDrive project. “We can also get an unmanned probe to Proxima Centauri in a human lifetime, 90 years.”

But the thrust produced has been so minimal that it’s been hard to tell if it happened at all—or if it came from another source in the testing environment.

According to Newton’s Second Law, the EmDrive is an impossibility: a closed system can’t just create thrust out of nothing—it would be action with no equal and opposite reaction. Thus, the microwaves could bounce around inside the cone but simply wouldn’t generate any thrust. It would be like trying to move a car by sitting inside and pushing the steering wheel.

A pair of upcoming papers could provide some answers. The papers will be presented by physicist Martin Tajmar, who heads the SpaceDrive project at Dresden University of Technology in Germany. The project has been developing instruments sensitive enough—and immune enough to interference—to detect whether or not the EmDrive really is producing thrust.

Tajmar’s team has been using those instruments to try to replicate the results by other researchers to create thrust with the EmDrive. They lock the drive inside a shield made out of MuMetal, an alloy made out of mostly nickel with some molybdenum and balance iron, which isolates the device from the Earth’s electromagnetic activity.

It is anticipated that the papers will answer whether the thrust created by the EmDrive came from the drive itself, or merely from the Earth’s magnetic field.

Even if this frontiers-of-physics testing turns out to prove the EmDrive a dud, it could expand our understanding of the laws of nature. We could discover that we have a prototype engine for interstellar travel—or a reaffirmation of the laws of physics as we understand them. “We need to be lucky, have a good intuition, and just try things that were never tested,” said Tajmar.

Either way, rocket science should benefit from the exploration of the strange, “impossible” EmDrive.