April 21, 2016

REACTIONLESS THRUSTERS UPDATE: The Curious Link Between the Fly-By Anomaly and the “Impossible” EmDrive Thruster.

About 10 years ago, a little-known aerospace engineer called Roger Shawyer made an extraordinary claim. Take a truncated cone, he said, bounce microwaves back and forth inside it and the result will be a thrust toward the narrow end of the cone. Voila … a revolutionary thruster capable of sending spacecraft to the planets and beyond. Shawyer called it the EmDrive.

Shawyer’s announcement was hugely controversial. The system converts one type of energy into kinetic energy, and there are plenty of other systems that do something similar. In that respect it is unremarkable.

The conceptual problems arise with momentum. The system’s total momentum increases as it begins to move. But where does this momentum come from? Shawyer had no convincing explanation, and critics said this was an obvious violation of the law of conservation of momentum.

Shawyer countered with experimental results showing the device worked as he claimed. But his critics were unimpressed. The EmDrive, they said, was equivalent to generating a thrust by standing inside a box and pushing on the sides. In other words, it was snake oil.

Since then, something interesting has happened. Various teams around the world have begun to build their own versions of the EmDrive and put them through their paces. And to everyone’s surprise, they’ve begun to reproduce Shawyer’s results. The EmDrive, it seems, really does produce thrust. . . .

According to McCulloch, inertia is simply the pressure the Unruh radiation exerts on an accelerating body.

That’s hard to test at the accelerations we normally observe on Earth. But things get interesting when the accelerations involved are smaller and the wavelength of Unruh radiation gets larger.

At very small accelerations, the wavelengths become so large they can no longer fit in the observable universe. When this happens, inertia can take only certain whole-wavelength values and so jumps from one value to the next. In other words, inertia must quantized at small accelerations.

McCulloch says there is observational evidence for this in the form of the famous fly by anomalies. These are the strange jumps in momentum observed in some spacecraft as they fly past Earth toward other planets. That’s exactly what his theory predicts.

Testing this effect more carefully on Earth is hard because the accelerations involved are so small. But one way to make it easier would be to reduce the size of allowed wavelengths of Unruh radiation. “This is what the EmDrive may be doing,” says McCulloch.

Next, I want antigravity.

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