EmDrive

[Northstar1989]

while in their experiment non-functional metal box produced exactly the same results as the "drive" they were testing.

The device "without modifications designed to produce thrust" was NOT a non-functional metal box. What it was: a resonant cavity WITHOUT slots cut into one of the ends to produce asymmetric refractive indexes for the microwaves. They still passed appropriately-tuned (resonant frequency) microwaves through the specially-designed metal cavity in both versions of the device.

The necessity of these slots was the basis of some controversy- the original British inventor of the drive thought they weren't necessary, whereas the American (Fetta) who produced his own, slightly re-designed and re-named ("Cannae") version of the originally British EmDrive drive design included these slots- as he thought they would be necessary for the drive to work with some of the other modifications he made to it.

The differences between the British version of the drive tested in China and the American version tested in China could easily explain the thousand-fold difference in observed thrust between the two experiments. The success of the slot-less drive confirmed that Fetta was dead-wrong in adding slots to the design- nothing more. The underlying drive appears to work perfectly well in either circumstance- which is what so many people who didn't do their research properly before writing criticisms of the drive wrongfully interpreted as "both the null and functional versions of the drive producing thrust".

I'm more concerned (and you should be more concerned) about the fact that they didn't perform the test in a vacuum. The possibility of interaction with air inside the chamber to produce thrust is a perfectly valid possible explanation- although in that case, the RF-load control should have probably produced thrust as well, and it didn't.

Regards,

Northstar

[Scotius]

Well, it wouldn't be first time when someone stumbled upon practical effect of a natural process that was explained by science much later. Alexander Volta built his first working battery long before discovery of electron.

[crazyewok]

Ah, stereotypical skeptic rage, with the most predictable of terminology.

As if other aspects of particle physics as any less 'crazy' in how they work.

Not rage Id love it to be true.

But because of the test conditions Im sceptical.

[M Drive]

Northstar> Thanks for that info, been hard finding a good explanation of that. Oh, and if the EmDrive was so much more powerful, why did NASA test the Cannae version first?

And I'd also like to remind people that there's a guy who's developing a 'reactionless' drive right here on the forum, that also happens to have some promising results, namely me. ;-) The latest pendulum test I performed did indeed have some unexpected results, and while the jury is still out I'm still very confident my invention produces thrust where it shouldn't. I've even performed 'null' tests with nothing out of the ordinary happening.

Currently upgrading the M Drive so that the force it produces will be easier to point in one direction, meaning it'll be easier to see if it produces thrust. The next test will also be more rigorously performed. Stay tuned!

[YNM]

Pendulum and torsion thrust-measuring devices are commonly used to measure ion engine thrust. There's nothing unconventional or unproven about the measuring equipment- there's a reason NASA had the equipment in the first place (it works).

Aide from criticizing the motivation of the scientists themselves on rather fuzzy logic, the only REAL criticism is that the "null" and "experimental" devices both produced thrust- a criticism that popped up once on the internet, and seems to have been mirrored many times since.

Unfortunately, what the people making that criticism did NOT understand, is that the "modification" (slots/roughening on the end of the device) was controversial in the first place. While Fetta (the American scientist to build HIS OWN version of the EmDrive and re-name it the "Cannae Drive") included these slots, and thought they were necessary, other previous versions of the drive included no such slots, and appeared to work perfectly fine. Thus, the "null" version of the drive (the use of the term null comes mainly from the critics, not the article itself) was not actually a null-version. It was an alternative, simpler version of the drive that was proven to work just as well.

The ACTUAL null version of the drive was the "RF load" the abstract of the data talks about. THIS TEST was an actual null version of the drive designed to replicate the same electricity consumption, RF frequency emissions, etc., and produced no thrust- thus validating the test of thrust production.

Being an actual scientist in real-life, with experience in an equally controversial area of research (Stem Cell Research- you could actually find my name in the scientific literature if you knew my real last name...), I can tell you from stories I've heard from a number of professors that critics have an extreme tendency to twist the words in your abstract to mean things they were never meant to mean. One little ambiguity, and it will be taken as proof that nothing you say is valid, if the reader doesn't want to believe your data/results. This is a VERY good reason to take the criticism with a grain of salt, just as the critics are taking the abstract with a whole boat-load of it...

Thanks for the input (didn't knew there're some other version of the engine) - I did also amazed by some other papers regarding high-energy lasers and a form of inverse-square law that doesn't really fit what I know. Well, still a high school student... But safe to say they didn't ensure that it will works in vacuum. Although the test is conducted in a vacuum chamber, the fact is that even they had closed the door, they kept the inside of it at ambient pressure and temperature. Surprise. Microwave can make some heat - so why not heat the air around it ?

I wish we'll have a better test and a better explanation later (so it's not really called as "quantum vacuum plasma thruster", which indeed sounds like four words thrown at random).

Edited August 7, 2014 by YNM

[ZetaX]

Can someone please post an actual (qualitative) description of what is supposed to happen, as I do not have the time or motivation to dig through the original articles¿ And I am not talking about pseudoscientific pop-culture nonsense like "it pushes virtual particles", as this by its own makes no sense without a lot of elaboration (e.g.: why should you even be able to confer impulse without making them real¿); an explaination why it does violate such well-understood principles like conservation of momentum and energy would be a bonus.

But note: if you (the reader) are not an actual theoretical physicist or close, you are probably not able to answer this in a good way.

I repeat: I do not want to hear some pseudoscientific nonsense, but actual quantum mechanics (not necessarily calculations, just the qualitative mechanics are enough; I will believe any numbers that do not sound too absurd); I am confident I can take the blow.

[Mazon Del]

Can someone please post an actual (qualitative) description of what is supposed to happen, as I do not have the time or motivation to dig through the original articles¿ And I am not talking about pseudoscientific pop-culture nonsense like "it pushes virtual particles", as this by its own makes no sense without a lot of elaboration (e.g.: why should you even be able to confer impulse without making them real¿); an explaination why it does violate such well-understood principles like conservation of momentum and energy would be a bonus.

But note: if you (the reader) are not an actual theoretical physicist or close, you are probably not able to answer this in a good way.

I repeat: I do not want to hear some pseudoscientific nonsense, but actual quantum mechanics (not necessarily calculations, just the qualitative mechanics are enough; I will believe any numbers that do not sound too absurd); I am confident I can take the blow.

Sorry to say Zetax but "it pushes virtual particles" IS what it does. It isn't pseudo-science. Virtual particles have been proven to exist in numerous scientific experiments.

However, here is a useful metaphor for you. Virtual particles are the ether. The engine pushes off the ether like a propellor pushes off of water.

As far as why this doesn't violate the various principles, there are many theories on this. The prime one that I have found is that if you take the system in isolation, it is a problem, but if you allow for a delayed onset of 'gravitational drag' from the rest of the unvierse it ballances out. Simply put, the gravity of the rest of the universe cancels out the inequality, but it takes a long period of time for all the forces in question to transit through space.

If you want a decent explanation from NASA itself, watch Day 3 of the Starship Congress 2013. It starts off with an update on Warp Drive research funded by NASA and then flows into the Q-Thruster, how it works, why it works, etc.

[ZetaX]

No that is not what it does. Such a thing is essentially forbidden by the uncertainty principle, to the best of my knowledge. You can't just push virtual particles around as you wish.

I also don't need nor want metaphors.

And how can aynthing "balance out"¿ Conservation of momentum is (also) a local thing, thus this sounds very fishy. There are probably ways to put momentum into spacetime, but that would need some mechanism why this should happen here.

In total, your response was exactly the kind I don't want to get: just metaphors for stuff instead of actual quantum mechanics. Can some else (and again: this is a request to actual working physicists; if you are not one, then I am quite sure you have no idea what is going on) please give one¿

[N_las]

No that is not what it does. Such a thing is essentially forbidden by the uncertainty principle, to the best of my knowledge. You can't just push virtual particles around as you wish.

I also don't need nor want metaphors.

And how can aynthing "balance out"¿ Conservation of momentum is (also) a local thing, thus this sounds very fishy. There are probably ways to put momentum into spacetime, but that would need some mechanism why this should happen here.

In total, your response was exactly the kind I don't want to get: just metaphors for stuff instead of actual quantum mechanics. Can some else (and again: this is a request to actual working physicists; if you are not one, then I am quite sure you have no idea what is going on) please give one¿

I suspect there isn't such explanation anywhere. In the words of Prof. John Baez: "This is (...) graduate-level baloney. "Quantum vacuum virtual plasma" is something you'd say if you failed a course in quantum field theory and then smoked too much weed. There's no such thing as "virtual plasma". If you want to report experimental results that seem to violate the known laws of physics, fine. But it doesn't help your credibility to make up goofy pseudo-explanations."

[Mazon Del]

The uncertainty principle has nothing to do with this engine. The uncertainty principle only concerns knowing the precise position and velocity vector of a particle. But this system doesn't care about that any more than a propellor cares about the position and velocity of any given water molecule.

In short you want someone to explain how a device works, but they are forbidden from mentioning the very thing that makes it work.

Another metaphor for you, you want someone to explain how airplanes fly, but have forbidden them from discussing air.

What you are really wanting is for someone to declare perfect knowledge about something that was only just discovered. Right now the people who invented the engine barely have an idea of how it works. The situation where NASA's version that was supposed to produce no thrust at all helps showcase this. If using a technology we know works, we cannot design an instance of that technology that fails to work, then we do not understand why it works. It is perfectly permissible for us to have a poor understanding of why a given system doesn't work this early into its inception.

[ZetaX]

The uncertainty principle has nothing to do with this engine. The uncertainty principle only concerns knowing the precise position and velocity vector of a particle.

Sorry, but you seemingly have no idea about quantum mechanics and virtual particles. The uncertainty principle is deeply involved in their existence.

Can I now talk to an actual physicist please¿

I suspect there isn't such explanation anywhere. In the words of Prof. John Baez: "This is (...) graduate-level baloney. "Quantum vacuum virtual plasma" is something you'd say if you failed a course in quantum field theory and then smoked too much weed. There's no such thing as "virtual plasma". If you want to report experimental results that seem to violate the known laws of physics, fine. But it doesn't help your credibility to make up goofy pseudo-explanations."

Yeah, that might be (and is what I think is happening), but some here in the forum claim there is a good theoretical basis. And either those are just talking bullsh*t and should stop it, or they can give me such an explaination...

Edited August 7, 2014 by ZetaX

[N_las]

The uncertainty principle has nothing to do with this engine. The uncertainty principle only concerns knowing the precise position and velocity vector of a particle. But this system doesn't care about that any more than a propellor cares about the position and velocity of any given water molecule.

In short you want someone to explain how a device works, but they are forbidden from mentioning the very thing that makes it work.

Another metaphor for you, you want someone to explain how airplanes fly, but have forbidden them from discussing air.

What you are really wanting is for someone to declare perfect knowledge about something that was only just discovered. Right now the people who invented the engine barely have an idea of how it works. The situation where NASA's version that was supposed to produce no thrust at all helps showcase this. If using a technology we know works, we cannot design an instance of that technology that fails to work, then we do not understand why it works. It is perfectly permissible for us to have a poor understanding of why a given system doesn't work this early into its inception.

No one is questioning the exsistens of virtual particles. The uncertanty principle has everything to do with virtual particles.

Edited August 7, 2014 by N_las

[N_las]

Yeah, that might be (and is what I think is happening), but some here in the forum claim there is a good theoretical basis. And either those are just talking bullsh*t and should stop it, or they can give me such an explaination...

People here seem to think that virtual particles are just some kind of particles that exsist in vacuum. And thus the statement "it pushes against this particles" sounds like an explanation.

From my understanding: If you force some virtual particles to become real (like at the event horizont of a black hole), and then you use those particles to transfer momentum, that could possibly work. But you have to take the energy (to make the particles real) from somewere. So overall this can't be more efficent than a simple photon-drive.

And the original explanation on how the drive works is TOTALLY different. They want to bounce microwaves inside an closed container, and by having different reflektivities at opposing walls, this should create a net force. I suspect this nonsense about pushing against virtual particles was only introduced because someone in there team understood how much ........ the orignial explanation was, and so they tried to find a new one.

Edited August 7, 2014 by N_las

[Mazon Del]

Apologies on the statement about uncertainty and virtual particles not interacting, just discussed it with someone. Yup, I'm in error there.

But there is nothing productive about conversing with ZetaX at the moment considering the mutually exclusive conditions of his information request. I shall watch in amusement.

[Rakaydos]

And the original explanation on how the drive works is TOTALLY different. They want to bounce microwaves inside an closed container, and by having different reflektivities at opposing walls, this should create a net force. I suspect this nonsense about pushing against virtual particles was only introduced because someone in there team understood how much ........ the orignial explanation was, and so they tried to find a new one.

The problem is, there's an actual Q-drive that should work, (even if it has photon drive efficency) who's explanation has been stolen to explain a second device the EM Drive/Cannae Drive, which is the BS microwave resonator thing.

[ZetaX]

What exactly is mutually exclusive¿

[N_las]

What exactly is mutually exclusive¿

- You want an explanation.

- You don't want an explanation. (that doesn't include an actual explanation)

[Rakaydos]

This is an explanation for the "old style" Q thruster, with diagrams:

Note that this was taken from an article 2 ears old, so it has nothing to do with the current EM-drive controversy.

[newanzer]

I've been skimming through the posts on this topic for a couple of days now. Very entertaining. I would like to ask just to make sure I'm getting it all correctly, Q-Drives use a magnetic field where the EmDrive uses Microwaves? Two different methods to possibly produce the same results - thrust? I don't know much about the EmDrive, but I'm assuming they are not just seeing thrust from photon pressure? Sorry, but my background in electro engineering with a minor in bio. Physics was never my subject.

[Heimdall5008]

From the description of the device it sounds to me like a complicated version of a photon drive. But (according to the values given in Wikipedia) this device has a thrust two to three orders of magnitude higher than you would expect from a photon drive.

From a quick look at the paper I have to say that this is not the worst paper I have seen but my prof would kill me nonetheless if I wrote such a paper. Experimental data shown on a photograph of the display and not in a plot? No way.

Also I find it a bit strange that only the data of one test run is shown. I would have expected at least two plots. One for each device with data from both directions in it overlaid. Also it seems a bit strange for me that nowhere in the paper are any indications of the tolerances. It always states approx but this can mean really everything. That the reverse tests where only done once is not nice but I understand the problems of timing schedules.

As far as I understood the paper, the experiment was conducted under vacuum (5E-6 Torr, what ever this is in SI units, to lazy to look it up).

A further test to eleminate systemetic errors would be to mount the device tilted by 90°. In this way the device should produce thrust but perpendicular to the measuring axis at that would therefore not be measureable (or at least far weaker).

Edited August 7, 2014 by Heimdall5008

[Rakaydos]

I've been skimming through the posts on this topic for a couple of days now. Very entertaining. I would like to ask just to make sure I'm getting it all correctly, Q-Drives use a magnetic field where the EmDrive uses Microwaves? Two different methods to possibly produce the same results - thrust? I don't know much about the EmDrive, but I'm assuming they are not just seeing thrust from photon pressure? Sorry, but my background in electro engineering with a minor in bio. Physics was never my subject.

From Harold White's description of the Q thruster above, it seems like the capaciter is just as important as the magnetic field, in that it's being used to maipulate the virtual particle potential into a predictable form, so the magnetic field can, in physics terms, do "work" on it.

[Z-Man]

From my understanding: If you force some virtual particles to become real (like at the event horizont of a black hole), and then you use those particles to transfer momentum, that could possibly work. But you have to take the energy (to make the particles real) from somewere. So overall this can't be more efficent than a simple photon-drive.

That is as precise as one can get with words and the virtual particle picture.

ZetaX: Sorry, I have to agree with Mazon Del that what you want is impossible. It would be impossible for any regular subject. You do not have enough time to read the original papers, but want the full math. That's a non-starter.

In this special case, it's worse. The original material is severely lacking. The EM-Drive theory paper is known to be faulty for neglecting the force on the slanted walls. It uses pure electrodynamics, no quantum theory involved. There exist no paper on the Cannae-Drive AFAIK, all one can gather from their presentation video is that they did numerics. The recent NASA paper claims not to give any explanation in the abstact, but also mentions NUMERICS several times in the main body. You will not find a proper physicist capable of taking all that as input and producing an output that makes sense.

That does not mean, of course, that any experimental evidence for these devices actually working should be outright ignored. Just taken with a good helping of salt until the kinks have been worked out and they have been independently verified (the Chinese don't count due to the hugely different value they measured). I do not mean to ridicule the researchers, only perhaps those who claim this is the final, irrefutable evidence of mainstream science being wrong and stuff.

And yes, the original Q-Thruster as explained by Rakaydos is a totally different beast. I'll try to digest the material for that.

[Mazon Del]

So, with the understanding that certain aspects of my understanding of these systems was apparantly flawed, my conceptual understanding of the workings of the different systems seems to be as follows

All of these engines rely in some form or another on 'pushing on virtual particles'. Exactly how they do that tends to be different though. The description I remembered from Harold White's version was that they were going to have a capacitor that was oscilatting back and forth (physically). It moves to the front of the ship, gets charged, moves to the back, discharging as it does, then moves back to the front. While the capacitor is charged it is able to 'exert force on the virtual particles' but because it is not charged when the capacitor moves forward, there is a force imbalance that you can consider 'forward thrust'. Normally if you move a mass back and forth in space all you do is move your ship back and forth slightly. For all intents and purposes (this is a pseudo metaphor, not an actual explanation) while charged, because of the interactions with virtual, the capacitor can be thought of as being "heavier" than it is when discharged. So you are pushing back with more force than you are pulling forwards.

Super simple metaphore: Harold White's version is a bird flapping its wings. It works, but provides pulsed bursts of 'thrust' rather than a constant stream.

The types that NASA, China and EMDrive have been testing seem less of a pulsed system and more a constant stream.

[Dragon029]

That does not mean, of course, that any experimental evidence for these devices actually working should be outright ignored. Just taken with a good helping of salt until the kinks have been worked out and they have been independently verified (the Chinese don't count due to the hugely different value they measured).

I'm not disagreeing that the Chinese test should not be trusted yet, but keep in mind that they utilised approximately 1000x the input power and received roughly 1000x the thrust of the smaller scale, NASA verification tests.

[Z-Man]

I'm not disagreeing that the Chinese test should not be trusted yet, but keep in mind that they utilised approximately 1000x the input power and received roughly 1000x the thrust of the smaller scale, NASA verification tests.

You are using advanced Fermi rounding here, rounding intermediate values to the nearest power of 1000.

Text quotes in part from Wikipedia:

720 mN was measured at 2500 W

That's a thrust to power ratio of 288 mN/kW.

91.2 µN at 17 W of input power. A net peak thrust was recorded at 116 µN at the same power level

(Note the different units) That's 7 mN/kW at peak. A factor of 40 lower.

Peak thrust of 48.5 µN at 28 W of input power

That's 1.7 mN/kW. Even lower.

The EMDrive like device tested at NASA really is quite similar to the original, the only difference is the added dielectric. And I agree with them that IF the device works, that's something that would help. So essentially, the NASA test says that at least 97.5% of the Chinese results are wrong. Chances are very high that the remaining 2.5% are also a fluke, despite all the effort put into the measurements.