Author Topic: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive  (Read 192397 times)

Offline Robotbeat

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #400 on: 05/05/2015 07:20 PM »
No. Vastly different orders of magnitude.
Honestly, I think you're underestimating what EM Drive would represent if true. EM Drive if real is an enormous departure from the current accepted laws of physics. Anyone who says otherwise is lying to you.

If EM drive is real (which it isn't), then something like a warp effect could certainly be part of the new physics behind it.

Which is all the more reason to take EM drive with an enormous grain of salt. There's a powerful temptation to let wishes be horses.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #401 on: 05/05/2015 07:35 PM »
I'm saying it's as certainly not real as just about anything I can imagine. Nothing can be 100%.

But while I'm certain the effect is an artifact, if it WERE to be true, the implications would be absurd. Unlimited energy (and yes, I know people try to tack on energy conservation whenever someone points it out, but it seems super contrived and kind of gutless), human interstellar travel in our lifetimes, even the possibility of engineering a reverse in the heat death of the Universe.

The laws of physics do not yield easily. I am confident this is a fluke as much as I'm confident of anything in physics. But I just want people to be aware of what the real implications of this would likely be, partly because it informs the likelihood of whether or not it should be taken seriously and how high the standard of proof really needs to be.


Remember, because it'd be so incredible, there's an enormous temptation to trick yourself into thinking it's real even when it's not.
« Last Edit: 05/05/2015 09:09 PM by Chris Bergin »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Space Ghost 1962

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #402 on: 05/05/2015 08:22 PM »
No. Vastly different orders of magnitude.
Honestly, I think you're underestimating what EM Drive would represent if true. EM Drive if real is an enormous departure from the current accepted laws of physics. Anyone who says otherwise is lying to you.

If EM drive is real (which it isn't), then something like a warp effect could certainly be part of the new physics behind it.

Which is all the more reason to take EM drive with an enormous grain of salt. There's a powerful temptation to let wishes be horses.

Your god like omnipotence is impressive here and obviously there's no need to continue testing it. This sort of attitude has bedevilled this thread and I expected better of a regular poster on this forum. Especially when you're making claims about it that have been explained on multiple occasions are not applicable to it, even with my limited understanding I can understand it is not a free unlimited energy device. It only puts out kinetic energy wise what's put into it electromagnetically, it isn't a magical device from Harry Potter.

He's politely expressing skepticism without being rude or defamatory. Why be hostile back?

There's considerable to prove if real. If one is an advocate, one wants skepticism and to eventually marshal enough proof.

Whole lot better than outright conclusory declarations.

Maybe I'm just fed up with seeing this attitude replicated a hundred times in the media coverage of this story. Did those at NASA who kindly posted here deserve the harsh treatment that they were subjected to by some on this thread?

Nope. Understand the sensitivity. You have no idea how well I understand it.

I'm afraid that's the times we live in. My preference is for a neutral environment. But others seem to have different tastes.

Unlike Robobeat, more willing to give the benefit of the doubt to allow time to sort things out. However this has dangers too, so it's not all for free.

Among others, I spent time going through Pons and Flieschmann, as well as the cavitation bubble stuff too at UCLA. As well as some pharmaceutical things too - 2 out of 10 actually worked out to be real. Amazing what a physics and mathematics background brings.

Oh, and the Lorenz effects with SSC magnets that bent abruptly. And the broken wire in the superluminal radiation stuff. Been polite and thoughtful through it all. You see, I'd like *any* part of it to even *slightly* be true.

Luis Alvarez was an inspiration. Miss him and Owen Chamberlain - was at their memorials, as well as the shindig for  Charles Hard Townes at SSL (he had me record a personal message for Apollo Saturn team members at his 99th - any out there let me know and I'll play it for you in person).

Online RonM

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #403 on: 05/05/2015 08:32 PM »
But while I'm certain the effect is an artifact, if it WERE to be true, the implications would be absurd. Unlimited energy (and yes, I know people try to tack on energy conservation whenever someone points it out,....

@Robotbeat.  Serious question for you.  You've mentioned several times that a working EMDrive would be an unlimited energy device.  I don't follow your logic though.  The EM drive converts electromagnetic input energy into output kinetic energy at some efficiency yet to be discovered, minus friction and other parasitic factors.  How does that make a free energy device?  Are you suggesting that it converts at greater than 100%?  How so?

I think what Robotbeat is referring to has to do with differences in kinetic energy. To double the velocity of an object takes four times the energy. However, many EM drive theories state that to double the velocity of an object only takes double the energy. So, you use the EM drive to increase the velocity, then use a normal system to convert the KE into heat for your heat engine, and you get extra energy from nowhere, free energy.

If your theory gets you free energy it is wrong.

Maybe something interesting and useful is going on in these devices, but it isn't going to throw away the past hundred years of physics.

Online Chris Bergin

Right then!

So, these two EM Drive threads are wall to wall clever people, but clearly that does not automatically mean such people know how to present themselves on the interweb. I've stepped in and cleaned up this thread for the following reasons.

1) The forum rules: http://forum.nasaspaceflight.com/index.php?topic=36479.0 - apply for all the threads on this forum (I know, crazy! Who'd have thought that!)

2) When you post on here, especially when you are responding to another poster, the forum software doesn't transport you both to a dark private room for you to go at each other. You're responding to both that person and the THOUSANDS of people reading the thread. Don't let yourself down by posting in the style of someone who's waving one's backside in the air whilst sobbing about people kicking it. ;)

3) This thread is for the discussion of the article on this thread. There's been 101 articles generated on other sites as a result, so why the main crap one has to be linked on this thread and discussed is not only a disservice to the effort that went into this site's article, it's also falling for the mass media trick of click bait. Don't fall for that, or at least respond on THAT site's comment section.

4) There were a few posts that appear to have been typed using one's nose bashing into one's keyboard, resulting in a very messy post. Remember, lots of people reading, they don't need to have to put posts through a translator to work out what is being said.

5) I'm sure this will get the traditional "OMG. Moderation like China or somefink! They appreciate my LOLZ jokes on Reddit and Facebook!". That's great, but I started this site and this forum out of the ashes of the mess that was SDC and I promised the 12 members who joined here that we'd never allow that to happen here. 30,000 members - or whatever - members later, I'm sticking to that plan.

Carry on................ :)

Offline PushHigher

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #405 on: 05/05/2015 09:49 PM »
I think what Robotbeat is referring to has to do with differences in kinetic energy. To double the velocity of an object takes four times the energy. However, many EM drive theories state that to double the velocity of an object only takes double the energy. So, you use the EM drive to increase the velocity, then use a normal system to convert the KE into heat for your heat engine, and you get extra energy from nowhere, free energy.

Thanks RonM,

ppnl's concerns are starting to make more sense to me.  The only way I can explain this away is the EM Drive's gravity gradient.  If you envision spacetime as a bed and a bowling ball as a spaceship, to get the bowling ball to roll forward - you have to push it laterally and also overcome the friction of the bed because it's making a large indentation into the bed.  Except in space there is no friction that hampers speed, there is friction that hampers acceleration (it becomes harder to accelerate as you approach the speed of light).   

Now imagining the bowling ball as the EM Drive.  The drive pushes down on the bed deeply and more acutely towards the back and gently and more broadly towards the front.  Push the bowling ball a bit from behind and it starts falling forward.  So in essence we are taking an enormous piece of the puzzle out of the equation. 

Thinking three dimensionally - if the EM Drive can create a more pronounced gravity well in the back and a less pronounced and broad gravity well in the front.  Same energy on both sides but the front wins because the back gravity well is mostly inside the frustum chamber pulling at the walls while the less pronounced and broad gravity well expands (more prominently) outside the frustum chamber.

Please take this with a grain of salt because I'm not a scientist and this is all based on my wild thoughts.

---
Edit - I personally don't feel that antigravity exists.  You can't pull the bed up and make the bowling ball roll. 
« Last Edit: 05/05/2015 10:34 PM by PushHigher »

Offline frobnicat

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #406 on: 05/05/2015 11:22 PM »
But while I'm certain the effect is an artifact, if it WERE to be true, the implications would be absurd. Unlimited energy (and yes, I know people try to tack on energy conservation whenever someone points it out,....

@Robotbeat.  Serious question for you.  You've mentioned several times that a working EMDrive would be an unlimited energy device.  I don't follow your logic though.  The EM drive converts electromagnetic input energy into output kinetic energy at some efficiency yet to be discovered, minus friction and other parasitic factors.  How does that make a free energy device?  Are you suggesting that it converts at greater than 100%?  How so?

I think what Robotbeat is referring to has to do with differences in kinetic energy. To double the velocity of an object takes four times the energy. However, many EM drive theories state that to double the velocity of an object only takes double the energy. So, you use the EM drive to increase the velocity, then use a normal system to convert the KE into heat for your heat engine, and you get extra energy from nowhere, free energy.

If your theory gets you free energy it is wrong.

Maybe something interesting and useful is going on in these devices, but it isn't going to throw away the past hundred years of physics.

Here is a concrete contraption to get unlimited energy, and unlimited deltaV, given the hypothesis of constant "propellantless thrust" at constant power :

bigger

Em drives mounted on a rotor turning at 2000m/s tangential velocity (not easy but this is the kind of tangential velocity attained in some energy storage flywheels...). Em drives consuming 1kW microwave, radiating some (all ?) of this power as heat and thrusting at 1N : 1N/kW is in the ballpark of what has been experimentally claimed already. This gives 2000m/s * 1N = 2kW mechanical power to the shaft of the rotor. 2kW mechanical power at the shaft are converted to 1800W DC current by a generator (and 200W radiated as heat). Of this 1800W DC electrical power, 250W are diverted for any use we like. To keep it in line with the topic I put it to good use to power another Em drive but really we are free to use those 250W for whatever (creating mass for instance). The power splitter is not 100% efficient, it radiates 50W of power. 1800-250-50 = 1500W to feed the RF amplifier. The RF amplifier wastes (radiates) 500W as heat and pumps 1000W of clean microwave back into the Em drives on the rotor.

The process needs an initial investment in energy (to make rotor move at 2000m/s tangential velocity) but then this is a free energy generator for all practical purpose. If small variations in efficiency make the rotor lose a bit of velocity, just divert a little more power to the RF amplifier : this is just a regulation problem, there is ample margins to adjust and stabilize around the optimal operating point.

If this consequence is a feature of the Em drive, great. If this is a problem then the problem rests in the initial hypothesis of  "propellantless thrust magnitude at constant power". But we often see by proponents the contradictory position that "of course EM drive respects COE, and somehow at constant power input at some (ill defined) point thrust has to surrender" and that "with that technology we could reach Proxima in less than a century", that later hope being made possible only by breaking COE, that is considering "constant thrust at constant power".

So either "constant thrust at constant power" is true and this is (apparently) breaking COE.
Then let's state it : "This journey to the stars is made courtesy of free energy", and be consistent : stop advocating nuclear power generators as Em drive tech could then be self powering.

Or either "constant thrust at constant power" is not true, COE might be preserved, then we would like to see a not so ill defined formula of thrust=function(power, other objective parameters ?), and short of that at least not be sold deep space mission profile that do presuppose constant thrust at constant power, undercover.

BTW "acquired kinetic energy" could by no way be an objective parameter in the mysterious thrust function that would leave COE unscathed, as has been clearly stated above by PPNL about frames, either we have a physical favored rest frame of "something" we are pulling onto, or we don't and "acquired kinetic energy" is going mystical as it depends on arbitrary choice of frame and we know frames are a fiction (even if some are more convenient and look more "natural").

Short journeys to the stars depend on (apparent) COE breaking. No (apparent) COE breaking (ie free or dirt cheap energy), no short journey to the stars. Even if we had an asphalt road to drive on between Sun and Proxima this would be of little help unless there were also cheap gas stations along the way : this is not a problem of shortage of momentum but of shortage of energy.
« Last Edit: 05/05/2015 11:38 PM by frobnicat »

Offline RotoSequence

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #407 on: 05/06/2015 02:42 AM »
Please forgive the dumb question, but I recall a comment along a similar line of thought before, so I figured I'd ask it here.

Would an imaginary solar-electric vehicle, with imaginary, 100% efficient solar cells and a 100% efficient electrical system, with an arbitrarily high specific impulse (say, Oh My God Particle equivalence) and arbitrarily high propellant reserves attain a final velocity and kinetic energy equivalent to the energy absorbed by the solar cells?
« Last Edit: 05/06/2015 03:18 AM by RotoSequence »

Offline KelvinZero

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #408 on: 05/06/2015 03:22 AM »
Please forgive the dumb question, but I recall a comment along a similar line of thought before, so I figured I'd ask it here.

Is it theoretically possible for an imaginary solar-electric vehicle, with imaginary, 100% efficient solar cells and a 100% efficient electrical system, with sufficiently high specific impulse and reaction mass to impart more kinetic energy into the rocket than the equivalent solar flux it used to accelerate?
This probably isn't the question you really meant to ask, or I am reading it wrong, but low ISP is what would allow this, and very easily. If two masses bounce off each other, most of the energy goes into the smaller faster object. A huge amount of light bouncing off you would hardly move you at all, but the same energy could move you quite fast if you were an electric train and could push against the entire earth.

(this is because momentum is conserved (mass*velocity), but kinetic energy is proportional to velocity squared)



« Last Edit: 05/06/2015 03:24 AM by KelvinZero »

Offline vulture4

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #409 on: 05/06/2015 03:31 AM »
If the spacecraft is accelerating (under thrust) it appears the photons approaching the "forward" end of the resonator where they would add momentum in the direction of travel will be redshifted by the acceleration of the resonator to a somewhat lower energy,
http://www.microwaves101.com/encyclopedias/waveguide-mathematics#velocity

Good article on the dynamic Casimir effect. http://arxiv.org/abs/1105.4714
Unfortunately the thrust from this mechanism is less than using the same energy to produce a stream of photons as an exhaust stream.


Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #410 on: 05/06/2015 05:00 AM »
If the spacecraft is accelerating (under thrust) it appears the photons approaching the "forward" end of the resonator where they would add momentum in the direction of travel will be redshifted by the acceleration of the resonator to a somewhat lower energy,
http://www.microwaves101.com/encyclopedias/waveguide-mathematics#velocity

Good article on the dynamic Casimir effect. http://arxiv.org/abs/1105.4714
Unfortunately the thrust from this mechanism is less than using the same energy to produce a stream of photons as an exhaust stream.

The Casimir article is confusing in that it talks about a moving mirror. The dynamic Caismir effect depends on an accelerating mirror not just a moving mirror. So if you are thinking of this as propulsion I just don't think so.

Offline rrb6699

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #411 on: 05/06/2015 10:47 AM »
perhaps I have an idea.  terrestrially, it could be that a method of accumulation of energy build-up could be harnessed.  at some point a power curve would be reached that would allow a controlled release of sufficient thrust to propel.  just a thought ahead.

Offline Nilof

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #412 on: 05/06/2015 11:22 AM »
I'm starting to believe COM, linear and angular, is no longer the brick wall I once thought, especially in the quantum realm:

http://arxiv.org/abs/0803.2811

...from Cornell, and other sources regarding "Transmutation of Momentum"

Way over my humble head: "Transmutation methods are developed for equations of the form x2 φ“ + x2(k2” - q̃(x)) φ = (v2 - (1/4)) φ, with v as spectral variable, which correspond to problems in quantum scattering theory at fixed energy k2 (here v ˜ l + (1/2) with l complex angular momentum). Spectral formulas for transmutation kernels are constructed and the machinery of transmutation theory developed by the author for spectral variable k is shown to have a version here. General Kontrorovič-Lebedev theorems are also proved."

Transmutation via the momentum plane

R. Carroll andD. S. Jones Communicater
Article first published online: 6 JUN 2011
DOI: 10.1002/mma.1670060129
Copyright © 1984 John Wiley & Sons, Ltd

Quantum mechanics can violate conservation of momentum locally but not globally. To see how this works consider the experiments that demonstrated the violation of Bell's inequality. The local measurement of a particle on one end is ruled by probability and can be anything. But when you connect that measurement to the measurement of its entangled twin they must match. That matching is driven exactly by the need to conserve angular momentum. It will do so even if it has to apparently cheat by violating Bell's inequality.

In the matrix mechanics formulation of quantum mechanics that conservation of momentum is built in at the ground level. In fact all the classical conservation laws are built in. In fact all of Newtonian and classical physics is built in on the classical limit. In the wave mechanics formulation it was less clear that conservation of momentum was preserved. It turned out that the two formulations were equivalent.

So if you want quantum mechanics to violate momentum conservation you are out of luck. It is like squaring the circle or trisecting the angle. The math just will not allow it.

Indeed. In fact conservation laws are even more apparent in QM because Noether's theorem becomes a lot more straightforward to use. If the hamiltonian is invariant under say translation symmetries exp(i*p*x), we have exp(-i*p*x) H exp(i*p*x) = H for any x. Taylor expanding the exponentials to first order in x, this must imply pH - Hp = 0. Therefore, the Hamiltonian commutes with  the total momentum operator which means that the latter must be a conserved quantity.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online Rodal

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #413 on: 05/06/2015 12:31 PM »
But while I'm certain the effect is an artifact, if it WERE to be true, the implications would be absurd. Unlimited energy (and yes, I know people try to tack on energy conservation whenever someone points it out,....

@Robotbeat.  Serious question for you.  You've mentioned several times that a working EMDrive would be an unlimited energy device.  I don't follow your logic though.  The EM drive converts electromagnetic input energy into output kinetic energy at some efficiency yet to be discovered, minus friction and other parasitic factors.  How does that make a free energy device?  Are you suggesting that it converts at greater than 100%?  How so?

I think what Robotbeat is referring to has to do with differences in kinetic energy. To double the velocity of an object takes four times the energy. However, many EM drive theories state that to double the velocity of an object only takes double the energy. So, you use the EM drive to increase the velocity, then use a normal system to convert the KE into heat for your heat engine, and you get extra energy from nowhere, free energy.

If your theory gets you free energy it is wrong.

Maybe something interesting and useful is going on in these devices, but it isn't going to throw away the past hundred years of physics.

Here is a concrete contraption to get unlimited energy, and unlimited deltaV, given the hypothesis of constant "propellantless thrust" at constant power :

bigger

Em drives mounted on a rotor turning at 2000m/s tangential velocity (not easy but this is the kind of tangential velocity attained in some energy storage flywheels...). Em drives consuming 1kW microwave, radiating some (all ?) of this power as heat and thrusting at 1N : 1N/kW is in the ballpark of what has been experimentally claimed already. This gives 2000m/s * 1N = 2kW mechanical power to the shaft of the rotor. 2kW mechanical power at the shaft are converted to 1800W DC current by a generator (and 200W radiated as heat). Of this 1800W DC electrical power, 250W are diverted for any use we like. To keep it in line with the topic I put it to good use to power another Em drive but really we are free to use those 250W for whatever (creating mass for instance). The power splitter is not 100% efficient, it radiates 50W of power. 1800-250-50 = 1500W to feed the RF amplifier. The RF amplifier wastes (radiates) 500W as heat and pumps 1000W of clean microwave back into the Em drives on the rotor.

The process needs an initial investment in energy (to make rotor move at 2000m/s tangential velocity) but then this is a free energy generator for all practical purpose. If small variations in efficiency make the rotor lose a bit of velocity, just divert a little more power to the RF amplifier : this is just a regulation problem, there is ample margins to adjust and stabilize around the optimal operating point.

If this consequence is a feature of the Em drive, great. If this is a problem then the problem rests in the initial hypothesis of  "propellantless thrust magnitude at constant power". But we often see by proponents the contradictory position that "of course EM drive respects COE, and somehow at constant power input at some (ill defined) point thrust has to surrender" and that "with that technology we could reach Proxima in less than a century", that later hope being made possible only by breaking COE, that is considering "constant thrust at constant power".

So either "constant thrust at constant power" is true and this is (apparently) breaking COE.
Then let's state it : "This journey to the stars is made courtesy of free energy", and be consistent : stop advocating nuclear power generators as Em drive tech could then be self powering.

Or either "constant thrust at constant power" is not true, COE might be preserved, then we would like to see a not so ill defined formula of thrust=function(power, other objective parameters ?), and short of that at least not be sold deep space mission profile that do presuppose constant thrust at constant power, undercover.

BTW "acquired kinetic energy" could by no way be an objective parameter in the mysterious thrust function that would leave COE unscathed, as has been clearly stated above by PPNL about frames, either we have a physical favored rest frame of "something" we are pulling onto, or we don't and "acquired kinetic energy" is going mystical as it depends on arbitrary choice of frame and we know frames are a fiction (even if some are more convenient and look more "natural").

Short journeys to the stars depend on (apparent) COE breaking. No (apparent) COE breaking (ie free or dirt cheap energy), no short journey to the stars. Even if we had an asphalt road to drive on between Sun and Proxima this would be of little help unless there were also cheap gas stations along the way : this is not a problem of shortage of momentum but of shortage of energy.

@frobnicat: how general are the statements above, concerning the hypothesis of constant "propellantless thrust" at constant power ?

Do they apply for example, to:

1) An idealized military search light used as a photon rocket (assuming, for argument's sake, in a Gedankenmodell that components have an infinite life without degradation, and you operate it an indefinite amount of time with energy supply)



2) Woodward's propellant-less Mach Effect (assuming, for argument's sake, that Woodward's conjecture is valid, and you can operate it an indefinite amount of time with energy supply)

If there are differences that constrain the energy paradox between the above two and the EM Drive, please point out the differences, as it may be instructive for this discussion to unveil these differences regarding what is possible and what is not possible (under conservation of energy and conservation of momentum).

Thanks
« Last Edit: 05/06/2015 01:14 PM by Rodal »

Online Rodal

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #414 on: 05/06/2015 01:37 PM »
...

Though, I suppose this discussion isn't about the article, and should go over to the main EMDrive thread...

From one co-author to another co-author of the article   ;)

I argue to keep the energy paradox discussion here, because what appears to bother scientists and engineers the most about the article is whether the article should have had more, stronger skeptical warnings, particularly inserted in the Applications section (that paraphrased Dr. White's previous AIAA papers on constant acceleration at constant power trips to the planets and to Alpha Centauri), concerning the energy paradox  issues.  Conservation of Momentum and Conservation of Energy (both are tied together in the stress-energy tensor in relativity  https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor , and are fundamental pillars of physics, from General Relativity to Quantum Mechanics - Ehrenfest theorem - ) is the crux of why the scientific and engineering community is so skeptical of the EM Drive, so, in a sense, the engineering and scientific community has decided that's what the article is about.

So it is healthy to discuss it here  :)
« Last Edit: 05/06/2015 02:18 PM by Rodal »

Offline zero123

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #415 on: 05/06/2015 02:33 PM »

Do they apply for example, to:

1) An idealized military search light used as a photon rocket (assuming, for argument's sake, in a Gedankenmodell that components have an infinite life without degradation, and you operate it an indefinite amount of time with energy supply)

A photon rocket does not have this problem because even at its theoretical maximum thrust per power ratio (which is about 3.336 * 10^-9 N/W), the speed it would have to reach in order to start the violation is the speed of light in vacuum. So, even though it has a constant thrust per power input it will simply never reach the required speed no matter what you do.

But any increase in the thrust/power ratio will decrease the speed to something that can be reached and at 1N/kW that speed is only 1 km/s.

Offline sghill

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #416 on: 05/06/2015 02:35 PM »
Fair enough Rodal! :)

<soapbox>Though, I think many people who don't follow the threads are missing the background that we wrote the article to summarize the activity and discussions going on in the forum for all of the great readers patient enough to follow along, but for whom the science is sometimes unapproachable. 

Our article went viral. Sobeit. A friend at Boeing emailed me just yesterday to tell me our article came across the internal Boeing news feed to employees, so I'd like to think we struck the right balance between explaining the "what is going on" and "why I should care."  Your complete rewrite of my closing paragraphs were particularly strong while remaining professionally restrained IMHO. :)  The article wasn't meant to be a white paper, but in an information vacuum I guess it filled that roll- if imperfectly.  I also noticed the click-bait articles began appearing the day after Chris announced we were working on an article (about 2 weeks before we released it), so to the people who wrote them who lurk on the forum, I ask you to exercise more care next time.  It does a disservice to the technology and the people exploring it to state: "Did NASA just discover warp technology by mistake?" as your headline.</soapbox>

Having said all that, I think it's super terrific that some new qualified people are now participating in the forum because of the article, and I encourage everyone else who is new to take the time to read all the thread discussions before raising a hand (the Search function works too!), and exercise patience when things get too deep to understand.  It's a rare gift that we all get to see this kind of sausage being made firsthand- especially when the pay-off could be so big.  Let's not ruin it.  And Mr. March, if you're reading this.  Please come back!

I'll just leave it at that...
« Last Edit: 05/06/2015 02:39 PM by sghill »
Bring the thunder Elon!

Online Rodal

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #417 on: 05/06/2015 02:47 PM »

Do they apply for example, to:

1) An idealized military search light used as a photon rocket (assuming, for argument's sake, in a Gedankenmodell that components have an infinite life without degradation, and you operate it an indefinite amount of time with energy supply)

A photon rocket does not have this problem because even at its theoretical maximum thrust per power ratio (which is about 3.336 * 10^-9 N/W), the speed it would have to reach in order to start the violation is the speed of light in vacuum. So, even though it has a constant thrust per power input it will simply never reach the required speed no matter what you do.

But any increase in the thrust/power ratio will decrease the speed to something that can be reached and at 1N/kW that speed is only 1 km/s.

Correct, that is one limit that should be pointed out.  Now, how about the Woodward Mach Effect ?

Offline hhexo

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #418 on: 05/06/2015 03:43 PM »
Hello everybody.
First of all, thanks to all who have made this discussion possible. I think that some good scientific discussion is being done here and in the other EmDrive thread. I have started lurking in this forum two weeks ago when the buzz about the new tests started, but only now I've decided to register and post some comments.

First of all, disclaimer: I am an engineer, not a physicist, but for my degree I had to do several exams to do with electromagnetism and even some quantum-related effects (the ones related to how a semiconductor works). So I have a healthy interest in physics, and I've read more on the matter than just what I studied for the exams, but I am not an expert.

I am perplexed by this paragraph in the article:

In Dr. White’s model, the propellant ions of the MagnetoHydroDynamics drive are replaced as the fuel source by the virtual particles of the Quantum Vacuum, eliminating the need to carry propellant. This model was also met with criticism in the scientific community because the Quantum Vacuum cannot be ionized and is understood to be “frame-less” – meaning you cannot “push” against it, as required for momentum.

I'd like to know more about Dr. White's model than just this description, and I don't know enough about the QV in terms of the complicated quantum mechanics maths, but I can wrap my head around virtual particles. I trust in their existence because they are related to black hole Hawking radiation, and we have observed that radiation. We have a model, and it works.
From what I understand of the model, though, I think I have a further observation about the model of "pushing against the virtual particles" that could lead to an experiment to disprove it.

Suppose you have a fluctuation where a particle-antiparticle couple spawns into existence and then annihilates pretty much immediately, just as in the model for virtual particles; in very simplistic terms (and I'm sure the reality is more complicated) they "borrow" some energy and momentum and "return" it when they annihilate (gah, I know, I'm butchering it, but bear with me). Now suppose that it was possible to "push" that particle-antiparticle pair as reaction mass with some (magic?) apparatus in the time while the pair is briefly in existence. The pair would gain a total momentum p equal and opposite to the apparatus pushing it.
Then the pair annihilates - but wait! Now the two particles have more momentum (and energy) than what they "borrowed" to come into existence. Because of CoM, that extra momentum must go somewhere. It can't just disappear. The system would have to transform in such a way that it's conserved.

The only way I can see this happening is if it is released as radiation (or other by-product particles). We know that radiation has momentum, so this is possible. In other words, a device using the virtual particles as reaction mass would "shine" with some extra radiation that can't be explained in any other way.
This radiation is either massive (i.e. it's made of particles) or massless (i.e. it's light).

In the latter case, energy and momentum for radiation are related by the E = pc relation. If we have measured a momentum variation p in our apparatus, and therefore we have an equivalent momentum variation to be radiated, then the energy released as radiation would be pc, which for any meaningful value of momentum would be utterly huge and it would likely destroy the apparatus. Plus, where is the energy coming from?!?

In the former case, then this extra stream of particles is radiated from the apparatus in such a way that it must be detectable by some experiment. Granted, it might be difficult (it they're neutrinos, we're basically stuffed) but it must be conceptually possible.
We might even be able to estimate a range of bounds for the average total mass generated by this interaction, because for each particle E = mc^2 + pv which can be summed over all the particles, and we know the upper bound of the total E (because of CoE that is at most what energy we pumped into the apparatus as input), the total p (which is equal to the momentum change of the apparatus) and we know that for every massive particle it must be true that 0 <= v < c.

So, I would argue that another objection to the "pushing against virtual particles" model is that since we haven't observed a huge amount of gamma rays melting the lab, then some mass must be created somehow from the expended energy. However it has not been explored in the experiments whether this extra mass was produced (and personally I suspect we won't find it, but that's just my opinion).

Does this make sense?

Offline john smith 19

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #419 on: 05/06/2015 04:10 PM »
As someone commented about another dispute over the momentum of particles (RV Jones "Instruments & Experiences) "We are in such a state of confusion that we must learn something."  :)

Perhaps it will only be how to build longer lasting magnetrons  :( , perhaps it will open up the solar system.

Time, and more data, will tell.   
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

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