EM Drive still chugging on...

[Roboramma]

I don't see how anything the violates conservation of momentum could work with any interpretation of quantum mechanics.

If conservation of momentum is violated it means very new physics. That would be great, but, let's put it this way: if the pilot wave interpretation allowed for violations of conservation of momentum then it would have been given even less credence than it was/is.

[TubbaBlubba]

Originally Posted by Roboramma

I don't see how anything the violates conservation of momentum could work with any interpretation of quantum mechanics.

If conservation of momentum is violated it means very new physics. That would be great, but, let's put it this way: if the pilot wave interpretation allowed for violations of conservation of momentum then it would have been given even less credence than it was/is.

The pilot wave could carry momentum, perhaps inte the vacuum. Seems to mesh well with the QFT treatment of the vacuum as coupled harmonic oscillators of the EM field.

[RussDill]

Originally Posted by TubbaBlubba

The pilot wave could carry momentum, perhaps inte the vacuum. Seems to mesh well with the QFT treatment of the vacuum as coupled harmonic oscillators of the EM field.

By the same logic, any other element of another QM interpretation could carry momentum. Maybe the wave collapse in copenhagen can carry away momentum. If pilot waves generated by just bouncing some photons around generated momentum, I'd think that type of thing would already turn up in accelerators.

[Squeegee Beckenheim]

Originally Posted by RussDill

If that's true, You'd need to be giving them enough energy so that when they recombine, they would emit a pair of photons. These photons would then be the carriers of momentum and you'd likely be at worse efficiency than just a straight photon drive.

I have previously seen one comment suggesting that they'd get better thrust by strapping a lightbulb to the back of the spaceship than they would through the proposed mechanism, although the actual supposed thrust is much greater than a photon drive. I suspect it's really just another variation on "because quantum". Certainly, the only people who actually have expertise in quantum mechanics I've seen talking about it have said that it's nonsense.

Quote:

At least to me, any explanation needs to first explain in what way this is not a free energy device.

To me the first stage is establishing that there's anything more going on than experimental error. Demonstrate that it does work before trying to work out the wheres and whys of how it works and how that can be reconciled with the known laws of physics.

[jimbob]

Originally Posted by Squeegee Beckenheim

Originally Posted by RussDill

If that's true, You'd need to be giving them enough energy so that when they recombine, they would emit a pair of photons. These photons would then be the carriers of momentum and you'd likely be at worse efficiency than just a straight photon drive.

I have previously seen one comment suggesting that they'd get better thrust by strapping a lightbulb to the back of the spaceship than they would through the proposed mechanism, although the actual supposed thrust is much greater than a photon drive. I suspect it's really just another variation on "because quantum". Certainly, the only people who actually have expertise in quantum mechanics I've seen talking about it have said that it's nonsense.

Quote:

At least to me, any explanation needs to first explain in what way this is not a free energy device.

To me the first stage is establishing that there's anything more going on than experimental error. Demonstrate that it does work before trying to work out the wheres and whys of how it works and how that can be reconciled with the known laws of physics.

I think the two are parallel. The fact that if it works, it seems to violate conservation of momentum, means that it is an extraordinary claim that is far more likel to be some overlooked experimental error - for example, this would seem less probable than cold fusion, at a similar stage in the experimental work.

[Jrrarglblarg]

Originally Posted by Squeegee Beckenheim

The published paper has been annotated with criticisms

Here's one without someone else's leading questions from incredulity, so we can add our own.
http://arc.aiaa.org/doi/10.2514/1.B36120


Snopes' conclusion

Quote:

The results of the Eagleworks team’s experiment will no doubt be debated for years to come, as its implementation would open up new frontiers in physics and spaceflight. The fact that they were able to publish their results in a peer-reviewed journal is a great leap forward for the team, but the peer review process does not mean the results are necessarily valid.

http://www.snopes.com/2016/11/25/res...iewed-journal/

[Squeegee Beckenheim]

Originally Posted by jimbob

I think the two are parallel. The fact that if it works, it seems to violate conservation of momentum, means that it is an extraordinary claim that is far more likel to be some overlooked experimental error - for example, this would seem less probable than cold fusion, at a similar stage in the experimental work.

If the results were clear and the experiment was carefully controlled and the published paper was detailed in explaining those controls and if it had been replicated in several labs by several teams with the same level of care then it would be harder to say that it couldn't be true because of conservation of momentum and instead be looking to determine how it doesn't violate it, or how it's possible for it to be an exception to it. The mechanism is much less important than whether or not it actually does what is claimed of it. If it doesn't, then there's nothing to explain.

[Squeegee Beckenheim]

Originally Posted by Jrrarglblarg

Here's one without someone else's leading questions from incredulity, so we can add our own.

I don't really understand what you mean by "questions from incredulity", or how it applies to that critique.

And the original paper has already been posted in this thread more than once.

[Jrrarglblarg]

I was decrying the quality of the "annotations" in the annotated version. It seems to me not many people responding to the thread have even read the paper. I'm just an overeducated carpenter, it isn't difficult to understand.

From my reading and with other science I know this thing seems like it could be our locomotive to develop the solar system, or it could be the animal magnetism and phlogiston of our time. I don't know yet, obviously, and I'm not willing to plug my ears with fingers and yell "sounds like woo" about the device.

The testing methodology seems sound. My criticism of the criticism annotations stems from my looking at the comments and screening out the utterly insignificant lab-science noobism first, and finding not much else. Questions can be useful, but answers more so.

[Jrrarglblarg]

Originally Posted by Squeegee Beckenheim

If the results were clear and the experiment was carefully controlled and the published paper was detailed in explaining those controls and if it had been replicated in several labs by several teams with the same level of care then it would be harder to say that it couldn't be true because of conservation of momentum and instead be looking to determine how it doesn't violate it, or how it's possible for it to be an exception to it. The mechanism is much less important than whether or not it actually does what is claimed of it. If it doesn't, then there's nothing to explain.

Exactly. We may be at the point with this gizmo like engineers trying to understand a steam engine without knowing that air contains particles.

The first thing to do is for third parties to replicate the build and try to reproduce the results.

[jimbob]

Originally Posted by Squeegee Beckenheim

If the results were clear and the experiment was carefully controlled and the published paper was detailed in explaining those controls and if it had been replicated in several labs by several teams with the same level of care then it would be harder to say that it couldn't be true because of conservation of momentum and instead be looking to determine how it doesn't violate it, or how it's possible for it to be an exception to it. The mechanism is much less important than whether or not it actually does what is claimed of it. If it doesn't, then there's nothing to explain.

I don't disagree with your view, but I'd consider the entire history of experimental science as further evidence. Any claimed effect uses a mechanism that violates this, just as when it was announced that neutrinos seemed to be travelling slightly faster than light, that was sufficiently extraordinary that more attention was paid to the experimental method - and a source of error was detected.

If something doesn't overturn the whole of physics, then it needs less verification.

[Squeegee Beckenheim]

Originally Posted by Jrrarglblarg

The testing methodology seems sound.

This is the issue - it doesn't. Every criticism of the paper says exactly the same thing (and I've read three, and had one in person from my father, who is a physicist who has been called upon to be a peer-reviewer himself) - there's not enough information. There's not enough data points, and there's not enough said about the set-up or the potential sources of error and how they've been mitigated for the results to actually mean anything.

[Squeegee Beckenheim]

Originally Posted by jimbob

I don't disagree with your view, but I'd consider the entire history of experimental science as further evidence.

It is evidence. But it doesn't matter. The reason the "violating the speed of light" thing you mention got the publicity it did is precisely because the experiment was done with the care and attention to detail is was. And it's worth noting that in that case the researchers were saying "we're sure we've made an experimental error, but we can't find it so we're publishing what we've got to see what everybody else thinks".

Were these experiments being carried out with that much care and attention to detail you'd have physicists champing at the bit trying to recreate the experiment for themselves, rather than most of them ignoring it and those who aren't saying "it's possible there's something there, I suppose, but this experiment isn't good enough to demonstrate that so it's most likely experimental error".

[jimbob]

Originally Posted by Squeegee Beckenheim

It is evidence. But it doesn't matter. The reason the "violating the speed of light" thing you mention got the publicity it did is precisely because the experiment was done with the care and attention to detail is was. And it's worth noting that in that case the researchers were saying "we're sure we've made an experimental error, but we can't find it so we're publishing what we've got to see what everybody else thinks".

Were these experiments being carried out with that much care and attention to detail you'd have physicists champing at the bit trying to recreate the experiment for themselves, rather than most of them ignoring it and those who aren't saying "it's possible there's something there, I suppose, but this experiment isn't good enough to demonstrate that so it's most likely experimental error".

I think we're in mild agreement. If the neutrino researchers had come up with an unsurprising result, they wouldn't be saying "we're sure there's a mistake in our experimental setup, but we can't find it".

[WhatRoughBeast]

In addition to any other objections, I find it odd that no one seems to have picked up on the fact that a working Em drive violates energy conservation, and in a big way.

The heart of the matter is that, if constant power gives constant acceleration, input energy is linear with time, as is velocity, but kinetic energy goes as time squared.

An example: Let's say we have a slightly improved Em drive with an efficiency of 1N/kW. This is installed on a 400 kg vehicle, with a power source which is a 200 kg Cassini-class RTG (5 W/kg) so thrust is 1 N. Acceleration is 1/400, or 2.5 x 10^-3 m/sec^2. After 800,000 seconds (9.26 days) velocity is 2,000 m/sec, so kinetic energy is 800 GJ. By coincidence, total energy input is 1 kW times 800,000, or 800 GJ. But here's where things get hinky. After 1.6 Gsec the velocity is 4,000 m/sec and KE is 3200 GJ. However, the RTG has only produced 1600 GJ, so the vehicle has acquired twice the energy put into the drive. Worse, the effect continues to grow with time, and if it weren't for relativistic effects would continue unchecked.

It's true that this doesn't apply to conventional rockets, reflected in part by the decreasing acceleration produced by a fixed exhaust velocity as velocity increases, with the characteristic limiting factor being the exhaust velocity. However, the equivalent to exhaust velocity for the Em drive has to be c, yet the energy imbalance shows up at much lower velocities. This does not seem at all reasonable. Nor does the prospect of a working perpetual motion machine.

[RussDill]

Been mentioned several times on this thread. If you put some of two counter-rotating wheels, you can actually easily extract energy as soon as the rotational velocity passes the break even point.

[Steve001]

The latest, also this article links to a just released NASA paper. http://m.phys.org/news/2016-12-mars-...sses-nasa.html

[Dancing David]

Originally Posted by Steve001

The latest, also this article links to a just released NASA paper. http://m.phys.org/news/2016-12-mars-...sses-nasa.html

he he

"So, based on my experience, the probability of this holding up under further analysis and testing appears slim. But it's not zero."

[3point14]

A very sensible article - or, at least, it appears to be to my untrained brain.

http://www.sciencealert.com/there-s-...pulsion-expert

[LTC8K6]

Well, Thunderf00t has busted it...

[Squeegee Beckenheim]

Originally Posted by LTC8K6

Well, Thunderf00t has busted it...

I just watched the whole video and the only interesting or new part was where he said that with the efficiency reported in the paper that even with a nuclear reactor it'd be at the break-even point with rocket fuel, meaning that rocket fuel is still the better way to go. But since he didn't provide any numbers to back that up, it's not really a useful thing to say.

[Solitaire]

Quote:

China claims to have carried out successful test of 'impossible technology'

The hypothetical EmDrive technology operates by emitting microwaves in a cone-shaped
engine. It makes the engine move forward and enact like a propulsion system. What makes
EmDrive more outstanding is its rare propulsion which terminates any rocket fuel requirement.
This technology could aid the astronomers by making space travel extremely swift.
Astronomers take three or more months to reach Mars, and with the help of this technology,
they can reach the Red Planet in just a month's time! Pluto can be reached in 12 years, but
with the help of EmDrive, the distance can be covered within 18 months.

LOL.

Would someone fetch me some dilithium crystals from Folger's planet.

[Puppycow]

Originally Posted by Solitaire

LOL.

China claims to have carried out successful test of 'impossible technology'

Quote:

The hypothetical EmDrive technology operates by emitting microwaves in a cone-shaped
engine. It makes the engine move forward and enact like a propulsion system. What makes
EmDrive more outstanding is its rare propulsion which terminates any rocket fuel requirement.
This technology could aid the astronomers by making space travel extremely swift.
Astronomers take three or more months to reach Mars, and with the help of this technology,
they can reach the Red Planet in just a month's time! Pluto can be reached in 12 years, but
with the help of EmDrive, the distance can be covered within 18 months.

Would someone fetch me some dilithium crystals from Folger's planet.

I don't get the part about how it could make space travel extremely swift. My understanding is that if it isn't just some sort of measurement error, the amount of thrust generated is minuscule. You could generate more thrust by exhaling (not that you could do that in space, but just to illustrate how much thrust we are taking about here).

[3point14]

Ignore.

[Mark6]

Originally Posted by Puppycow

I don't get the part about how it could make space travel extremely swift. My understanding is that if it isn't just some sort of measurement error, the amount of thrust generated is minuscule. You could generate more thrust by exhaling (not that you could do that in space, but just to illustrate how much thrust we are taking about here).

The article you quoted is messed up. Even if EM drive works as described, it will make a difference only for trips to Jupiter and farther, where years of acceleration really add up. To Mars EM drive would take significantly LONGER (although perhaps cheaper) than chemical rockets.

Ion drives suffer from the same tortoise-hare issue: anywhere closer than asteroid belt, bare wins.

[Steve001]

Originally Posted by Puppycow

I don't get the part about how it could make space travel extremely swift. My understanding is that if it isn't just some sort of measurement error, the amount of thrust generated is minuscule. You could generate more thrust by exhaling (not that you could do that in space, but just to illustrate how much thrust we are taking about here).

Consider the amount of thrust generated using ion propulsion. Deep Space 1 probe used it. The thrust generated was equal to about one sheet of paper. The Dawn probe took 4 days to go from 0 to 60 miles an hour. Even if the thrust is lower for the E M Drive, over time speed can amount greatly.

[Genesius]

Originally Posted by Puppycow

I don't get the part about how it could make space travel extremely swift. My understanding is that if it isn't just some sort of measurement error, the amount of thrust generated is minuscule. You could generate more thrust by exhaling (not that you could do that in space, but just to illustrate how much thrust we are taking about here).

Originally Posted by Steve001

Consider the amount of thrust generated using ion propulsion. Deep Space 1 probe used it. The thrust generated was equal to about one sheet of paper. The Dawn probe took 4 days to go from 0 to 60 miles an hour. Even if the thrust is lower for the E M Drive, over time speed can amount greatly.

Also (assuming for the sake of argument the thing actually works) there's no reason to think the version currently being tested is the most efficient version of the drive. Changing the materials used, the shape of the cavity, or the microwave frequency generated could all result in higher efficiency.

[Steve001]

Originally Posted by Genesius

Also (assuming for the sake of argument the thing actually works) there's no reason to think the version currently being tested is the most efficient version of the drive. Changing the materials used, the shape of the cavity, or the microwave frequency generated could all result in higher efficiency.

Perhaps we'll know for sure one day whether this drive is fact or fake.

[RussDill]

Originally Posted by Genesius

Also (assuming for the sake of argument the thing actually works) there's no reason to think the version currently being tested is the most efficient version of the drive. Changing the materials used, the shape of the cavity, or the microwave frequency generated could all result in higher efficiency.

Thrust per weight might matter in a spacecraft, but it doesn't really matter if you are just using the em drive as a free energy device.

[Red Baron Farms]

Originally Posted by Steve001

Perhaps we'll know for sure one day whether this drive is fact or fake.

This is a skeptic forum. So it is acceptable to call it fake/experimental error until there is more evidence to the contrary.

Without new physics, it certainly is impossible. One day maybe we will have new physics like when Einstein surpassed Newton. But it will take something big like that to explain how the drive could even possibly work.

[PhantomWolf]

Originally Posted by RussDill

Thrust per weight might matter in a spacecraft, but it doesn't really matter if you are just using the em drive as a free energy device.

You have to supply electrical power to the drive to get your thrust (assuming there is thrust.) The the amount of gained kinetic energy is less than the supplied electrical energy, there you are not getting free energy.

Originally Posted by Red Baron Farms

Without new physics, it certainly is impossible. One day maybe we will have new physics like when Einstein surpassed Newton. But it will take something big like that to explain how the drive could even possibly work.

And this might be the observation that makes us go looking. If these three teams are right and there is thrust once they have finally eliminated every possible error, then it has to do it and maintain the laws we already know, that means it's time to start looking for whatever else it is emitting that is taking the energy away and would balance the equations, just as they did with the Neutrino.

[RussDill]

Originally Posted by PhantomWolf

You have to supply electrical power to the drive to get your thrust (assuming there is thrust.) The the amount of gained kinetic energy is less than the supplied electrical energy, there you are not getting free energy.

The amount of energy you need to add to the em drive to get a specific delta v is constant. 10 m/s to 15 m/s takes just as much time and energy as 15 m/s to 20 m/s. Kinetic energy increases as the square of the velocity. This means that there must be some break even point where the liner graph of expended energy intersects the polynomial graph of stored kinetic energy. Once past that point the energy of the system increases faster than the input energy. Not to mention to mention all the energy bring lost to heat.

[BowlOfRed]

Originally Posted by PhantomWolf

You have to supply electrical power to the drive to get your thrust (assuming there is thrust.)

Yes.

Quote:

The the amount of gained kinetic energy is less than the supplied electrical energy, there you are not getting free energy.

What enforces such a limit? I should be able to pick a frame in which the engine is providing arbitrarily large amounts of KE.

[steenkh]

Originally Posted by BowlOfRed

What enforces such a limit? I should be able to pick a frame in which the engine is providing arbitrarily large amounts of KE.

Physics as we know it enforces such a limit. But it would be nice if free energy existed ...

[RussDill]

<tin hat on>The reason the EM drive results have been so small and inconsistent is due to our high rate of speed (and changing rate of speed) in relation to the ether.</>

[rwguinn]

Originally Posted by Puppycow

I don't get the part about how it could make space travel extremely swift. My understanding is that if it isn't just some sort of measurement error, the amount of thrust generated is minuscule. You could generate more thrust by exhaling (not that you could do that in space, but just to illustrate how much thrust we are taking about here).

Originally Posted by Steve001

Consider the amount of thrust generated using ion propulsion. Deep Space 1 probe used it. The thrust generated was equal to about one sheet of paper. The Dawn probe took 4 days to go from 0 to 60 miles an hour. Even if the thrust is lower for the E M Drive, over time speed can amount greatly.

It may make getting there quicker, but staying there becomes problematic. You are going to have to slow down to enter local orbit, in all likelihood, so you only get the benefit for about 1/2-3/4 of the trip

[3point14]

Originally Posted by rwguinn

It may make getting there quicker, but staying there becomes problematic. You are going to have to slow down to enter local orbit, in all likelihood, so you only get the benefit for about 1/2-3/4 of the trip

I suspect you'd trust towards the target till you were half way there then away from the target after that.

[Steve001]

Originally Posted by rwguinn

It may make getting there quicker, but staying there becomes problematic. You are going to have to slow down to enter local orbit, in all likelihood, so you only get the benefit for about 1/2-3/4 of the trip

Ok Debbie Downer. I'm never invitin' you to any parties.

[Beelzebuddy]

High-mass small-thrust setups aren't suited for hohmann transfers. You won't have one take you to Mars by itself.

What they are suited for is shaving down the rocket equation by shlepping stuff around when it's convenient. You can get by with a much smaller rocket if you can offload most of the dv into an unmanned EM-drive tug (or what have you) that spends years towing your spaceship out to just under Earth escape velocity before you board and go.

[3point14]

Originally Posted by Beelzebuddy

High-mass small-thrust setups aren't suited for hohmann transfers. You won't have one take you to Mars by itself.

What they are suited for is shaving down the rocket equation by shlepping stuff around when it's convenient. You can get by with a much smaller rocket if you can offload most of the dv into an unmanned EM-drive tug (or what have you) that spends years towing your spaceship out to just under Earth escape velocity before you board and go.

So an elliptic orbit? Or a circular one a long way out?