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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?

#41

Post by buster »

gizmo686 wrote: post #23
yincrash wrote: post #18

Earlier quoted context omitted.

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

Because photons travel at the speed of light, we need to consider relativistic effects. Under special relativity, classical momentum (mass * velocity) is not actually conserved. To achieve conservation of mass, we consider the "inertial mass" of an object instead of the classical mass, where the intertial mass is given by: m'=ym y=1/sqrt(1-(v/c)^2) As you can see, y>1 and y approaches infinity as you speed approaches…

What a nice and clear description! You should teach that stuff :)

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

#42

Post by homborg »

javert wrote: post #39
searine wrote: post #35

I've been following this story pretty closing for several months now. So here's the opinion of an actual research scientist. Q. Does the Em drive produce thrust? A. Undetermined. Several tests from multiple independent labs have reported thrust, including in a vacuum. However several of the labs that reported positive thrust come from a sketchy background. Q. Does it violate conservation of momentum? A. Undetermined.…

Thanks, nice summary. > I think the last thing anyone wants to see here is "new physics". I really want to see new physics, because I want to see us get off this rock and far away. I think most people want to see new physics. I think that's why this topic is so popular. That said, I can understand physicists not wanting to see new physics. Wait. In a way, that sentence is crazy . In a way, physicists should want to s…

I read it as: we want a better explanation, than just: "new physics!"

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

#43

Post by davesque »

javert wrote: post #39
searine wrote: post #35

I've been following this story pretty closing for several months now. So here's the opinion of an actual research scientist. Q. Does the Em drive produce thrust? A. Undetermined. Several tests from multiple independent labs have reported thrust, including in a vacuum. However several of the labs that reported positive thrust come from a sketchy background. Q. Does it violate conservation of momentum? A. Undetermined.…

Thanks, nice summary. > I think the last thing anyone wants to see here is "new physics". I really want to see new physics, because I want to see us get off this rock and far away. I think most people want to see new physics. I think that's why this topic is so popular. That said, I can understand physicists not wanting to see new physics. Wait. In a way, that sentence is crazy . In a way, physicists should want to s…

Maybe not wanting to see new physics before seeing rigorous, reproducible experimental results? Kind of a cart before the horse thing? Just guessing.

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

#44

Post by Animats »

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…

"Every time this gets tested—presumably more and more carefully—the measured force gets smaller."

Uh oh. That's a classic sign of a bogus effect. It's like physicists at Stanford trying to replicate the Pons-Fleischmann cold fusion experiment. At first, they were enthusiastic, and expected big results. They started out with the apparatus surrounded with radiation alarms in case it generated dangerous amounts of neutrons. After a while, they discovered that the effect was at most twice background radiation. Since humans have water in them and water is a neutron reflector, just moving around the equipment could produce effects at that level. Then they moved the equipment to the inside of a cube of lead bricks, to eliminate external neutrons. No more neutrons, background or otherwise.

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

#45

Post by buster »

eropple wrote: post #22
jdmichal wrote: post #17

Earlier quoted context omitted.

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 th…

> 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. Mine does, and it cost $120. http://www.amazon.com/Panasonic-Countertop-Microwave-Technol... (I don't find that it actually makes a difference when using it, though.)

I don't understand either. I think every microwave oven i've seen has settings like "high, low" or "600W, 750W"..

Like: http://www.amazon.de/gp/product/B0076ZQQ14?keywords=mikrowel...

Or: http://www.amazon.de/gp/product/B00T8138J2?keywords=mikrowel...

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

#46

Post by p1mrx »

searine wrote: post #35

I've been following this story pretty closing for several months now. So here's the opinion of an actual research scientist. Q. Does the Em drive produce thrust? A. Undetermined. Several tests from multiple independent labs have reported thrust, including in a vacuum. However several of the labs that reported positive thrust come from a sketchy background. Q. Does it violate conservation of momentum? A. Undetermined.…

EmDrive and Cold Fusion are the perfect complementary technologies. Next someone should claim to invent a cooling system that doesn't reject heat, and we can start building Stargate Puddle Jumpers.

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

#47

Post by PhantomGremlin »

eropple wrote: post #22
jdmichal wrote: post #17

Earlier quoted context omitted.

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 th…

> 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. Mine does, and it cost $120. http://www.amazon.com/Panasonic-Countertop-Microwave-Technol... (I don't find that it actually makes a difference when using it, though.)

I have a Panasonic and it makes a difference. (or maybe it's just confirmation bias?)

Where the Panasonic shines is at lower power settings. E.g. if you defrost at 30% power for 3 minutes you get much more pleasant results than using the typical microwave. In a typical microwave the thinner areas actually start cooking rather than simply defrosting when operating at 30% power.

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

#48

Post by PhantomGremlin »

buster wrote: post #45
eropple wrote: post #22

Earlier quoted context omitted.

> 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. Mine does, and it cost $120. http://www.amazon.com/Panasonic-Countertop-Microwave-Technol... (I don't find that it actually makes a difference when using it, though.)

I don't understand either. I think every microwave oven i've seen has settings like "high, low" or "600W, 750W".. Like: http://www.amazon.de/gp/product/B0076ZQQ14?keywords=mikrowel... Or: http://www.amazon.de/gp/product/B00T8138J2?keywords=mikrowel...

If you pay careful attention to a typical microwave, you can easily tell when the magnetron is on and when it's off. E.g. when on the light will dim slightly, and if you're heating some food it might visibly bubble.

Set a typical microwave oven to 90% and you will see the magnetron 100% on for perhaps 15 seconds and 0% on for 2 seconds.

The Panasonic claims to operate differently. It actually adjusts the power to the magnetron. So the magnetron itself is continuously operating at 90% power.

A quick google turned up this article, which pretty much says the same thing. http://www.techlicious.com/review/microwave-ovens-with-inver...

If you want to investigate further, the key is to include the keyword "inverter", which is how Panasonic advertises it.

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

#49

Post by evincarofautumn »

eevilspock wrote: post #40
searine wrote: post #35

I've been following this story pretty closing for several months now. So here's the opinion of an actual research scientist. Q. Does the Em drive produce thrust? A. Undetermined. Several tests from multiple independent labs have reported thrust, including in a vacuum. However several of the labs that reported positive thrust come from a sketchy background. Q. Does it violate conservation of momentum? A. Undetermined.…

> I think the last thing anyone wants to see here is "new physics". The article's responds with the nonsensical "Some damage to our theories of physics is an acceptable payoff if we get a working space drive." EDIT: Let me clarify why it's a nonsensical statement: First, I think it meant to say "cost", not "payoff". Second, there would be no cost. None of the things we were able to do with our existing theories would…

Well, it’s improbable, not nonsensical. If someone goes and implements a technology that trounces our working theories, we certainly need to update those theories. It’s just that that’s exceedingly unlikely to happen.

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

#50

Post by tlarkworthy »

idlewords wrote: post #10
tlarkworthy wrote: post #6

Earlier quoted context omitted.

"Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results. Shawyer has often been dismissed because of his own lack of peer-reviewed scientific publications. That looks to be changing very soon; a paper Shawyer presented at the International Astronautical Conference in Toronto in 2014 is in the final stages for peer-review for publicatio…

You're referring to an unpublished paper by the author, which appears to be a design for a space vehicle. I asked about independent tests of the claimed effect.

If the answer was yes, that paragraph would not be there.
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