I saw this article in Wired referenced on a couple of science pages on FaceBook.
NASA validates 'impossible' space drive
Let me give you the short version of how this engine is supposed to work. Microwaves are beamed into a cone-shaped cavity. They bounce around the cavity and produce a force on the cavity in a direction perpendicular to the direction they were beamed in. Imagine turning on the microwave oven and watching it push itself off the kitchen counter.
Why is it impossible? This violates one of the basic laws of physics.
The Conservation of Momentum
The conservation of momentum isn’t your ordinary law of physics. It is one of the most fundamental principles in science. It is intimately related to spatial symmetry. Roughly speaking, the laws of physics here are the same there. You may know this as Newton’s third law of motion or for every action, there’s an equal but opposite reaction.
To obey the conservation of momentum, propellent is pushed out by the rocket and the rocket is pushed by the propellent. This engine is said to produce thrust without any propellent.
So I was immediately skeptical. So I dug around a little bit. I found a short description of the experiment. One thing I found interesting is that the authors did not lecture on “”physics of the quantum vacuum plasma thruster.” All right, that’s fine; if the results were groundbreaking, the explanation might come later. Something similar happened in 1986. Researchers at IBM discovered ceramic materials that lost all electrical resistance (superconductivity) at surprisingly high temperatures. There is still no complete explanation for why this happens. What is different about these two cases is that the superconductivity ceramics didn’t violate any basic principles of physics.
What made me laugh however is the authors claim that their device may be “demonstrating an interaction with the quantum vacuum virtual plasma.” I have no idea what they mean by a quantum vacuum virtual plasma.
I also found their paper. This made me giggle, too. They built two devices: one was designed to work, the other was designed not to work. Both versions produced the same amounts of thrust.
Phil Plait in his Bad Astronomy blog at Slate says this episode is reminiscent of the faster than light neutrinos and the mysterious force slowing down the Pioneer spacecrafts.
It reminded me of an article that caught my attention while I was in grad school. I remember getting all excited about this revolutionary paper published in one of the premier physics journals. The authors had data that showed that a gyroscope rotating in one direction weighed less than if it were rotating in the opposite direction. Finally, an anti-gravity device!
My research advisor wasn’t nearly as excited. His comment was something along the lines of “systematic error.” But still I held out hope.
Then four months later, my anti-gravity hope were dashed. Others trying to replicate the results found there is no anti-gravity.