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How does NASA's EmDrive actually work ?

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« on: April 22, 2016, 11:40:22 pm »

How does NASA's EmDrive actually work ?
Posted on Friday, 22 April, 2016




The EmDrive could revolutionize space travel. Image Credit: NASA / Mark Rademaker
Scientists have been coming up with new ideas to explain how the controversial propulsion system works.
The electromagnetic propulsion engine, which some scientists believe could herald a new era of spaceflight by replacing conventional chemical rocket engines, has been a hot topic recently.

EmDrive allegedly works by converting electrical power in to thrust without the need for propellant through a process that scientists argue is in direct violation of the laws of physics.

Now in a renewed effort to understand exactly what is going on inside the controversial engine, researchers have been mulling over possible explanations for its peculiar behavior.

One new hypothesis, which has been presented by Mike McCulloch from Plymouth University, suggests that the anomalous propulsion being generated by the drive is the result of something known as "the Unruh effect" which asserts that an accelerating observer will see black-body radiation where a stationary observer will see none.

In other words, the universe warms up when you accelerate and, according to McCulloch, the inertia is the pressure that this Unruh radiation is exerting on the accelerating body.

"At very small accelerations, the wavelengths of Unruh radiation become so large they can no longer fit in the observable universe," he said.

"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 [be] quantised at small accelerations."

Whether this turns out to be what is causing the EmDrive's thrust however remains to be seen.

http://www.sciencealert.com/this-new-hypothesis-could-explain-why-the-controversial-em-drive-works
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« Reply #1 on: April 22, 2016, 11:41:25 pm »

Here is a link to Satellite Propulsion Research, the group that actually invented the EM Drive: http://emdrive.com/
They have theory papers, photos, and other information.
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« Reply #2 on: April 22, 2016, 11:42:40 pm »

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« Reply #3 on: April 22, 2016, 11:44:09 pm »


This new hypothesis could explain how the controversial EM Drive works

You had us at fuel-free space travel.
JOLENE CREIGHTON, FUTURISM
22 APR 2016


The EM Drive is at it again, it seems. Recently, Mike McCulloch, from Plymouth University in the UK, unveiled a hypothesis that aims to explain how this physics-breaking mode of travel could actually work. And his idea has some proponents of this method of transport rather excited.

But before we go into the newly proposed theory: a quick summary of what the EM Drive actually is.
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« Reply #4 on: April 22, 2016, 11:47:21 pm »

In short, the EM Drive could allow us to explore our universe in ways that, today, we can only dream about … if it’s ever developed, that is.

It works (or should work) thanks to microwaves. The claim is, you bounce microwaves back and forth inside a truncated cone, and the result will be a thrust toward the narrow end of the cone.

That seems simple enough, yes? After all, you are just converting kinetic energy into another form of energy.

Well, here is the kicker: The total momentum increases as the device begins to move. That is like placing yourself inside a box, pushing on the side, and generating thrust. Sounds silly, doesn’t it? Well, here is another kicker: To date, a number of teams around the world have built their own versions of the EM Drive. And they generate thrust… but only a tiny amount.

And, alas, we don’t know where this increased momentum comes from. Critics assert that this is a violation of the law of conservation of momentum (which is part of the fundamental physics that governs our universe). Moreover, scientists assert that there are other effects that could, in essence, be producing a false positive and generating this increased thrust.

To that end, a host of scientists have been trying to work out whether this is an anomaly or if it actually works (and if so, how). This is where McCulloch comes in.
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« Reply #5 on: April 22, 2016, 11:48:00 pm »

A new idea

In short, the new hypothesis is based on ideas regarding inertia and the way objects move under very small accelerations. It has to do with something called 'the Unruh effect'. This asserts that an accelerating object experiences black body radiation, meaning that the universe warms up when you accelerate. And in this regard, according to McCulloch, inertia is the pressure the Unruh radiation exerts on an accelerating body.

As MIT notes, "at very small accelerations, the wavelengths of Unruh radiation 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 quantised at small accelerations."

Thus, the inertia of photons that are inside of the aforementioned truncated cone have to change as they bounce back and forth. And to conserve momentum, this must generate a thrust.
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« Reply #6 on: April 22, 2016, 11:48:21 pm »

In an email interview, RIT astrophysicist Brian Koberlein summarises:

    The Unruh effect (basically) says that an accelerated object should see a thermal background due to background quantum fluctuations. The calculation of the Unruh effect is straightforward, and isn’t controversial. Unruh radiation is (basically) the idea that in the detection of this thermal background you can trigger the emission of real particles. In other words, can you create real radiation ‘out of the vacuum.’ So they are claiming Unruh radiation is real, and causing the EM effect.

So. Is this the solution we needed? Well, maybe not.

In the end, there are a number of ways that individuals have attempted to explain the EM Drive, and to date, none of them have been shown to provide a conclusive answer. And while MuCulloch’s idea is based upon long established theoretical ideas, he applies the ideas in rather unconventional (and controversial) ways.

Koberlein notes that the work, in itself, is certainly valuable, stating, "they are trying to fit the results to a model, and looking for testable predictions, both of which are great". However, he clarifies, saying that we need to maintain a healthy dose of skepticism
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« Reply #7 on: April 22, 2016, 11:48:44 pm »

In relation to the idea that the Unruh effect is responsible for inertia, he asserts, "the quantised inertia idea at least makes some predictions that can be tested, so that’s not bad;" however, this does not mean that it is responsible for the thrust that is seen in relation to the EM Drive.

He continues, "the idea that the EM effect can account for the flyby anomaly is weak tea. To begin with, just because it can be made to fit under certain assumptions, it isn’t the same as predicting an effect. Secondly, there are lots of proposed explanations for the flyby effect, most of which are more mundane and don’t require exotic physics (such as radio chirps)".

So it seems that it may be a little early to assert that we have figured out how the EM Drive really works. As Koberlein concludes, "The biggest challenge they still have is that these results are so extraordinarily small that lots of things can explain them. They aren’t there yet, though".

This article was originally published by Futurism. Read the original article.
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« Reply #8 on: April 22, 2016, 11:48:58 pm »

http://www.sciencealert.com/this-new-hypothesis-could-explain-why-the-controversial-em-drive-works
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« Reply #9 on: April 24, 2016, 11:43:00 pm »

This is great, the laws of physics have been defined by humans, anything that pushes these boundaries will lead to new thinking and progression of science.
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« Reply #10 on: April 24, 2016, 11:56:28 pm »

Could it be as simple as when the microwaves hits the back of the chamber it provides a little punch/kick which create the motion.
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« Reply #11 on: April 24, 2016, 11:58:54 pm »

Chances are, it' s already in prototype...by the time WE know that it's in production, it will have already been in use for 40 years.

The microwaves bounce around inside the chamber, and the shape of the chamber causes the microwaves to interact with the virtual particles (providing thrust) in only one direction? Is the shape of the chamber scalable? Or does only the one very specific sized chamber work?

We must first stop calling them laws, as that title asserts that we have the answers to every aspect of physics, when we clearly do not.
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