concerning the Impossible Space Drive

Sources like IFLscience (the real one, not the parody) and Slashdot are reporting that NASA has successfully tested their impossible space drive again. That’s incredibly misleading: Yes, the test was successful, but the engine itself isn’t. They already know it doesn’t work. They’re trying to figure out HOW it doesn’t work.

The EM drive, image courtesy of SPR, Ltd.

The drive supposedly produces thrust with no fuel. Now, the device is supposed to have a truly tiny thrust – about the force of a mosquito sitting on your hand. But that’s not really an issue if you can build a thousand of these and let them run for years and years without needing space for propellant on your spacecraft. It would open up space travel in a major way that we only see in science fiction, because you escape the “Tyranny of the rocket equation” by not having to exponentially add rocket fuel to your rocket to lift the other fuel in your rocket… (Yo dawg)

So naturally, NASA, or rather Eagleworks, an unofficial group of NASA engineers* working on unconventional propulsion, is testing this thing. If it’s real, it’s possibly the greatest breakthrough in physics of all time, because it breaks at least the conservation of momentum in Newton’s laws (for every action, there is an equal and opposite reaction). This dispenses with the “action” part and proceeds straight to the “reaction”.

And what they initially found, months ago, is… it DOES produce thrust. However, so did their non-functional test article (It’s mentioned in the second segment of that article), which implies that however this thing is “working”, it’s not the way the inventor claimed (and the mechanism the inventor claimed is sciency-sounding gibberish anyway).

There have been roughly similar devices in the past that claim the same feat, the most famous of which was the Dean drive. Although Dean refused to let the drive be tested by scientists (always a good sign) it was eventually determined that it was probably the vibrations of the mechanism causing itself to scoot across the table, and a quirk of the device’s friction across the table meant it had a harder time scooting backwards – result, net forward motion.

This one, they CAN test, so they are. What’s happened is that they’ve conducted tests that rule out air currents (the earlier news-making report) and now electromagnetic radiation (this report). Yes, this thing produces such small force that it could just be air currents or the Earth’s magnetic field, or magnetic fields from the power cable they’re using to power the drive. Their new theory is that it’s minute thermal expansion of the drive itself when electricity is pumped into it.

In summary, no, they haven’t confirmed the thing works, they’re just trying to figure out what’s really causing this device to move. If this thing actually turns out to be producing some propellantless thrust, I’ll… I’ll be shocked. And so will pretty much everybody else who’s studied physics. But for now, you can relegate this to the same corner of physics apocrypha as perpetual motion machines, antigravity, and free energy devices.

* The leader, Dr. Harold White, is famous for his theoretical work on warp drives. They still require physically impossible things, but at least they’re well-defined physically impossible things.