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The 'impossible' EmDrive could reach Pluto in 18 months?

wired.co.uk

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Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#11

Post by saalweachter »

Niten wrote: post #7

It's good to see that someone finally got around to testing this in a vacuum. Here's the paper mentioned in this story: http://arc.aiaa.org/doi/abs/10.2514/6.2015-4083 High levels of skepticism are still warranted, as much as I would love for this to pan out. Every time this gets tested—presumably more and more carefully—the measured force gets smaller. The original test at Chinese Northwestern Polytechnical Universi…

Smaller effect size as studies improve is the classic sign of a non-event. ESP and the like went through similar cycles - impressive early studies followed by a series of more rigorous studies with diminishing effects until people got bored and moved on to the next big thing.

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#12

Post by gilgoomesh »

idlewords wrote: post #4

Has any independent laboratory confirmed this effect and published on it in a peer-reviewed journal?

Not exactly a journal but NASA reproduced the Cannae and EmDrive style devices and documented it:

http://ntrs.nasa.gov/search.jsp?R=20140006052

Turning 17 watts of microwave power into 40-91 micronewtons of thrust isn't exactly stunning, though.

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#13

Post by idlewords »

gilgoomesh wrote: post #12
idlewords wrote: post #4

Has any independent laboratory confirmed this effect and published on it in a peer-reviewed journal?

Not exactly a journal but NASA reproduced the Cannae and EmDrive style devices and documented it: http://ntrs.nasa.gov/search.jsp?R=20140006052 Turning 17 watts of microwave power into 40-91 micronewtons of thrust isn't exactly stunning, though.

Another data point: my kitchen microwave has been getting 32 millimeters to the hot pocket.

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#15

Post by Natsu »

Niten wrote: post #7

It's good to see that someone finally got around to testing this in a vacuum. Here's the paper mentioned in this story: http://arc.aiaa.org/doi/abs/10.2514/6.2015-4083 High levels of skepticism are still warranted, as much as I would love for this to pan out. Every time this gets tested—presumably more and more carefully—the measured force gets smaller. The original test at Chinese Northwestern Polytechnical Universi…

What would it take to get one of these into space?

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#17

Post by jdmichal »

n0us wrote: post #14

The worlds biggest unsolved mystery about microwaves has still not yet been answered; how exactly does one microwave on HIGH?

While your comment doesn't add much to this discussion, I won't turn down a chance to educate.

Conventional microwave ovens only have two states: on and off. (I won't rule out the possibility of some exotic build having multiple powers, but the ones you interact with on a normal basis don't.) So, power levels cannot change the output level of the magnetron. Instead, the power levels control what percentage of time the magnetron is on. A power level of 50% means the magnetron is on for roughly 50% of the indicated time. These off periods will typically result in more even heating at the cost of time. The off periods give the heat a chance to conduct through the food and balance, reducing the lava-and-ice problems seen when heating frozen things in microwaves.

HIGH just means 100% power level.

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#18

Post by yincrash »

DenisM wrote: post #8

Let's cut to the chase: 5. Q. Why does the EmDrive not contravene the conservation of momentum when it operates in free space? A. The EmDrive cannot violate the conservation of momentum. The electromagnetic wave momentum is built up in the resonating cavity, and is transferred to the end walls upon reflection. The momentum gained by the EmDrive plus the momentum lost by the electromagnetic wave equals zero. The direc…

Can anyone explain electromagnetic momentum? I thought that em waves (photons) are massless. How can they have momentum (mass * velocity)?

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#19

Post by MattPearce »

Niten wrote: post #7

It's good to see that someone finally got around to testing this in a vacuum. Here's the paper mentioned in this story: http://arc.aiaa.org/doi/abs/10.2514/6.2015-4083 High levels of skepticism are still warranted, as much as I would love for this to pan out. Every time this gets tested—presumably more and more carefully—the measured force gets smaller. The original test at Chinese Northwestern Polytechnical Universi…

The Chinese test used kilowatts rather than watts of power:

http://www.you-tech.it/index.php/content/download/12369/1124...

Re: The 'impossible' EmDrive could reach Pluto in 18 months?

#20

Post by nerd_stuff »

DenisM wrote: post #8

Let's cut to the chase: 5. Q. Why does the EmDrive not contravene the conservation of momentum when it operates in free space? A. The EmDrive cannot violate the conservation of momentum. The electromagnetic wave momentum is built up in the resonating cavity, and is transferred to the end walls upon reflection. The momentum gained by the EmDrive plus the momentum lost by the electromagnetic wave equals zero. The direc…

So they "build up" momentum out of nowhere? I think that just moves the breaking of conservation of momentum to a different place.

I'm glad they're testing this until it's proven one way or the other but if it somehow works I doubt that'll be the explanation.

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