The impossible engine that promised to defy the laws of physics

Science · Published 19 October 2026 · Updated 20 October 2026 Swipe more like this →

In short: In 2001, a device emerged claiming to generate thrust without any propellant. It promised a revolution in space travel by bypassing Newton's third law, but as scientists investigated the mysterious EmDrive, they found something far more grounded: the subtle influence of heat and magnetism.

The EmDrive, or resonant cavity thruster, first appeared in 2001 through the work of Roger Shawyer. Unlike traditional rocket engines that produce thrust by expelling propellant as reaction mass, the EmDrive was purported to be a reactionless drive. This concept is highly controversial because it appears to violate the fundamental law of conservation of momentum and Newton's third law of motion, which dictates that every action must have an equal and opposite reaction.

The history of the device is marked by waves of excitement and subsequent refutation. In 2016, a NASA group led by Harold White reported observing a small amount of apparent thrust. However, later studies by Martin Tajmar's group at the Dresden University of Technology suggested these results were false positives. By 2021, Tajmar's team concluded that the observed thrust could be explained by external factors, such as thermal gradients causing scale components to warp, or the interaction between Earth's magnetic field and power cables in the testing chamber.

While some researchers, such as Yue Chen at the China Academy of Space Technology, have pursued testing prototypes in orbit, the scientific consensus remains skeptical. Physicists like Sean Carroll and Eric W. Davis have argued that the reported thrusts are indicative of measurement errors. Most published experiments have failed to show any thrust greater than the margin of error, with Tajmar's 2021 analysis refuting all EmDrive claims by at least three orders of magnitude. For now, the device remains categorized by the scientific community as pseudoscience.

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