The impossible’ EmDrive Thruster has cleared its first credibility hurdle – Astronomy Magazine
Litany of Problems
Critics liken the EmDrive to trying to move a car by getting inside and pushing on the windshield. This violation of fundamental principles has drawn criticism from the scientific community ever since the device was first proposed in the early 2000’s by British researcher Roger Shawyer. Tests of the device have been subject to some glaring flaws, and one Chinese team was forced to retract the results of a 2012 experiment after concluding that they were due to thermal expansion in the test device. And EmDrive tests have never before passed peer review, meaning that the results weren’t looked over by other scientists. With this paper, published in the Journal of Propulsion and Power, the researchers have cleared an initial hurdle on the path to legitimacy.
That doesn’t mean that the EmDrive actually works though. Passing peer review simply means that other scientists have examined their data and methodology and declared them sound. There could still be experimental flaws that no one has been able to catch yet. In addition, no one has yet replicated their experiment and produced similar results, another key step in the process.
To test whether the EmDrive produced thrust, the researchers mounted it on a pendulum that would swing to indicate movement. They tested the device at different levels of current and received positive results every time. Their results indicate that the device puts out 1.2 millinewtons of thrust — or enough to lift about a thousandth of a gram a meter into the air — for every kilowatt of power put through it. In an important move, they tested the EmDrive in vacuum conditions as well, and report that it performs nearly the same. A prominent criticism of earlier tests was that the heat generated by the device could have been responsible for the apparent movement. Moving the experiment to a vacuum provides a more perfect environment to run tests in.
Besides opening up new realms of physics, a propellant-less device like the EmDrive would be extremely useful for extended missions in space. The device runs only on electricity, meaning that a spacecraft wouldn’t need to bring any fuel along with it and could power itself using only solar panels. The thruster is far less powerful than conventional rockets, and even the ion engines currently in use on some NASA spacecraft, but both of those thruster designs require fuel to be carried on board. Other fuel-free methods of propulsion do exist, such as light sails and laser propulsion, but they are orders of magnitude weaker than the EmDrive claims to be.
“NASA is looking forward to the scientific discussions with the broader technical community that will occur based on the publication of the Eagleworks team’s experimental findings, said Jay Bolden, an Engineering PUblic Affairs Officer with NASA’s Johnson Space Center. “This is part of what NASA does in exploring the unknown, and the agency is committed to and focused on the priorities and investments identified by the NASA Strategic Space Technology Investment Plan. Through these investments, NASA will develop the capabilities necessary to send humans farther into space than ever before.”
Room for Error
The list of possible confounding variables is long, however. In their paper, the researchers address nine of them, including everything from vibrations to magnetic interactions with external hardware. One of the largest possible sources of error comes from the thermal expansion of the heat sink attached to the device. In their experimental configuration, the heat sink is offset from the device’s center of gravity, meaning that as it expands, it could cause the EmDrive to move.
How could an EmDrive work? Harold “Sonny” White, the principal investigator on the project and a long-time proponent of propulsion devices on the fringes of science, favors a theory that assumes that empty space is not in fact so empty. If so, it should be possible to exchange momentum with this “quantum vacuum.”