A week ago, in a far-off corner of the Internet, a little website called NASAspaceflight.com published a story about a futuristic propulsion drive that produces thrust without propellant. Amazing! said the rest of the Internet. A drive that can run without heavy propellant opens up travel to the farthest reaches of space. Not only that, but the NASA-based group testing the drive had detected a slight spatial distortion around it—a warp, in other words. As in “warp speed” and “warp drive.” Not only could humans get to deep space unencumbered by fuel, but they could even travel faster than the speed of light!
Does that sound too good to be true? Excellent. This isn’t the first time that this theoretical drive—tested by a small lab called Eagleworks, based at NASA’s Johnson Space Center—has surfaced. Every time it comes up, it gets the space nerds frothing about the possibility of interstellar travel. And every time, physicists have to settle everyone down.
This time is like those times.
Last year, the Eagleworks lab—headed up by Harold “Sonny” White—said at a conference on propulsion technologies that they had measured thrust from an electromagnetic propulsion drive. The basic idea behind an EM drive, which is based on a design from a British engineer named Roger Shawyer, is that it can produce thrust by bouncing microwaves around in a cone-shaped metal cavity.
That would be awesome, of course, except it violates one of the fundamental tenets of physics: conservation of momentum. Saying that a drive can produce thrust without propellant going out the backside is kind of like saying that you can drive your car just by sitting in the driver’s seat and pushing on the dashboard.
Now, the last time this idea popped up it made a bunch of noise, which eventually settled down because of some pretty (ahem) obvious flaws in Eagleworks’ experiments. The physicists hadn’t run the tests in a vacuum—essential for measuring a subtle thrust signal. And while they had tested the drive under multiple conditions, one of them was intentionally set up wrong. That setup produced the same thrust signatures as the other conditions, suggesting that the signals the physicists were seeing were all artifacts.
This time around, Eagleworks researchers said they had addressed one of those problems. “We have now confirmed that there is a thrust signature in a hard vacuum,” wrote Eagleworks member Paul March in a forum. It was that post—all the way back in February—that led to most of last week’s hullabaloo.
Let’s be clear, though: Just because this time the group conducted its experiments in a hard vacuum doesn’t mean that an interstellar warp drive is soon to come. Marc Millis, who headed up the now-defunct Breakthrough Propulsion Physics lab at NASA’s Glenn Research Center—which, like Eagleworks, was dedicated to finding science-fiction-sounding ways to move a spaceship—says there are plenty of other interactions between the drive and the test chamber that could account for the results. “Even if it was done in a hard vacuum,” Millis says, “you have to take into account the distance between the drive and the chamber wall, whether those walls were conductive, and the geometry of the system.”