Humanity has come a long way in understanding the universe. We have a physical frame that mainly matches our observations, and new technologies have allowed us to analyze the Big Bang and take pictures of black holes. But the hypothetical EmDrive rocket engine threatened to change what we knew about physics … if it worked. After the last round of testing, we can say with a high degree of certainty that this is not the case.
If you have memories of the 90s, you probably remember the interest in cold fusion, a supposed chemical process that could produce energy from fusion at room temperature instead of millions of degrees (choose your favorite scale, the numbers are huge) . The EmDrive is basically cold fusion for the 21st century. First proposed in 2001, the EmDrive uses an asymmetric resonator cavity within which electromagnetic energy can bounce. There is no escape, but advocates claim that EmDrive generates oomph.
The idea behind the EmDrive is that the conical shape of the cavity would reflect radiation in such a way that a greater net force would be exerted on the resonator at one end. Therefore, an object could use this “engine” for hyper-efficient propulsion. That would be a direct violation of the conservation of momentum. Interest in the EmDrive dispersed until 2016 when NASA’s Eagelworks laboratory built a prototype and tested it. According to the team, they detected a small but measurable net force, and that it got people interested.
There was a lot of skepticism about the results from Eagelworks and other teams have not been able to duplicate the results. A team from the Dresden University of Technology has completed a complete new test, attempting to replicate the Eagelworks results. And they found nothing: the Dresden EmDrive generated zero thrust as electromagnetic radiation bounced inside the resonator.
The team also tried to explain the Eagelworks results, which they did by varying the experimental design. The Dresden researchers used better measurement techniques to show that the EmDrive produces no thrust, but by adjusting the measurement scale and changing the resonator suspension points, they obtained the same small apparent thrust as NASA. That confirms that the Eagelworks push was actually just a thermal effect. The researchers also speculate that Eagelworks selected the data by reporting random fluctuations in a way that did not represent the full data set.
This really feels like the end of the road for EmDrive. Unless someone can identify a large element of physics that we have missed, there is no way this engine will work as described. Proponents of EmDrive will have to pack it up unless they want to end up like cold fusion cranks from the ’90s. That’s just science in action, but it’s also a bit of a bummer because the EmDrive would have changed the world if it weren’t a fantasy.