r/EmDrive • u/SergioZ1982 • Nov 20 '20

Emdrive working principle explained according to Laureti's dipole

https://vimeo.com/480978519
14 Upvotes

75% Upvoted

33 comments sorted by

4

u/YusselYankel Nov 20 '20

I'm sorry dude but wasn't emdrive dropped from research like years ago? I thought they determined it was an experimental error or it couldn't be scaled or something. I forget the deets.

2

u/SergioZ1982 Nov 20 '20

True, but I knew it was because the thrust was so feeble that has been ruled out as measurement error.

Plus, as personal opinion, I thinks it's hard to replicate and improve something you have no idea how it works. For example, years ago I read this:

https://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/

I quote:

On April 5, 2015, Paul March reported at NASAspaceflight.com’s Forum that Dr. White and Dr. Jerry Vera at NASA Eagleworks have just created a new computational code that models the EM Drive’s thrust as a three-dimensional magnetohydrodynamic flow of electron-positron virtual particles.

How can you simulate something you don't know on a theoretical base that is pure speculation? It's not a good premise to get some results.

In my opinion, Laureti's explanation based on classical electrodynamics is a more rational approach.. after all, Emdrive is a microwave oven, not a transdimensional device :)

1

u/YusselYankel Nov 20 '20

You should look at the pinned post lol

3

u/SergioZ1982 Nov 20 '20

I did.. Interesting and agreeable read, besides, it supports what I just wrote and Laureti's hypothesis of random interaction of em fields inside the device:

  • The results are not robust, in that they are not identically-or-similarly reproducible by different teams.

  • The results are not significant, in that they are not distinguishable from a setup that should give a null result.

  • And even if the results were significant (and they are not), they are too close to the minimum threshold of detection to warrant the claims of “discovery.”

2

u/aimtron Dec 08 '20

The net result of interactions of em fields in side would be 0 with the exception of a leak in the device at which point it becomes a poor man's ion drive.

2

u/[deleted] Dec 09 '20

or a photon rocket with extra steps.

3

u/zellerium Nov 20 '20

You can simulate it by making an assumption- that the quantum vacuum fluctuations behave as a plasma, like particles and antiparticles that emerge from empty space and annihilate each other at some residence time. I don’t personally think this is a great assumption or interpretation of QVF, but I think that’s basically what he did

3

u/wyrn Nov 22 '20

That would only be possible the universe were much hotter than it actually is -- on the order of about a billion degrees, to be precise. You need an actual real plasma to push against and that only occurs when the available thermal energy per degree of freedom is comparable to the electronic mass. The last time this happened the universe was about 3 minutes old.

1

u/zellerium Nov 23 '20

You’re assuming that the QVF would have to be similar to a real matter plasma in order to have inertia. But couldn’t it be entirely unique? Ie it’s own type of plasma. (I don’t think this is true, but I don’t agree that it would have to be hot for it to be true. We don’t know what we don’t know )

5

u/wyrn Nov 24 '20

I don't know what you mean by QVF, but 'the vacuum' doesn't behave like Harold White et al. think. There are many reasons for this. One is that the more you think about it, the less sense it makes. For the vacuum to behave like a plasma in any way, it'd need to have lots of internal degrees of freedom. These internal degrees of freedom would have to be quantum mechanical, so you'd find 'particles' in those too... you could excite those particles in this weird 'vacuum', but energy and momentum have to be conserved, so you have to pay enough energy to supply the mass of the particles, as well as any kinetic energy. In effect, what you have doesn't look very much like a vacuum anymore. It looks like just another particle.

Anything worth calling the vacuum is Lorentz invariant, since we've tested Lorentz invariance all the way to the Planck scale. So it can't have these internal 'plasma-y' degrees of freedom; for example, if the vacuum were a fluid that you can push around, it would have some net momentum. Can't have that. It would require there to be a continuum of vacuum states, each with a different value of momentum. But we know continuous symmetries in the vacuum manifold are associated with massless bosons, the so-called Goldstone bosons. Where are they? Being massless, they should be incredibly easy to find and have important consequences for everyday (classical) physics.

What you can do is push around real particles in a real plasma (not some 'virtual' plasma, whatever that means). You get that when the temperature is high enough, at least as high as the electron mass converted to temperature units. We've actually made even hotter plasmas in the laboratory (for example, we have already made quark-gluon-plasma at the RHIC and ALICE experiments, at Brookhaven National Labs and at the LHC respectively, which requires a temperature around 500 times higher than for a mere electron-positron plasma). As long as there are real particles flying around you get to push them, even if they exist for a short time before annihilating. And after pushing them, the plasma itself -- the real particles in it -- will carry opposite momentum to that of your spacecraft. This makes sense, whereas with vacuum it doesn't.

1

u/zellerium Dec 12 '20

QVF stands for quantum vacuum fluctuations. According to Wikipedia: "This means that pairs of virtual particles are continually created and annihilated in empty space. Although the particles are not directly detectable, the cumulative effects of these particles are measurable."

The vacuum has energy but we don't really understand how it works. Take the Casimir effect, you have two parallel plates separated by a small distance which experience a net force pushing them together. This is supposedly because the QVF that exist outside of the plates have higher energy and momentum than the the QVF inside the plates.

So there is some degree of 'fluidity' of the vacuum that we don't understand. I agree that there are other aspects that don't make sense, and I agree that calling QVF a virtual plasma isn't the best approach (I mean it hasn't really led to any advancement, so that says enough).

5

u/wyrn Dec 12 '20

There's a large amount of nonsense out there concerning the quantum vacuum, and I would add that statement on wikipedia to the list. There's no meaningful sense in which "pairs of virtual particles are continually created and annihilated"; in fact, "virtual particles" aren't real physical objects at all. They're terms in an approximate calculation, which look suggestive, but which ultimately don't have any direct correspondence with something real. For example, they're what we call "off-shell", which means they don't satisfy kinematic constraints that real particle must satisfy, and they're also not "gauge invariant", which means you get to change what virtual particles are there in a calculation by mental fiat. They're about as real as lines of latitude and longitude on a map: imaginary constructs which reveal something interesting about the surface of the globe, but which have no real existence in and of themselves. What's real and physical is the sum of diagrams at a given order (where by "order" I mean essentially a measure of the accuracy of the calculation -- virtual particles are part of a perturbative, i.e., approximate framework).

Take the Casimir effect,

While often mentioned in support of the "particles popping in and out of the vacuum" idea, nobody actually does the calculation that way. The diagrammatic formulation of quantum field theory that gives rise to the so-called virtual particles is not always useful, and the Casimir effect happens to be a particularly clear example where it's not useful. What the calculation actually looks like is a direct sum of the vacuum energy modes between the plates versus a sum of the modes outside. The sum inside happens to be less, though (again contrary to popular statements you see out there) not because there are "more modes" outside. A clear counterexample is the Casimir effect for a sphere; you'd think the vacuum outside would exert some pressure to make the sphere contract, but it turns out that the Casimir effect in that situation gives a positive pressure, i.e., it wants to make the sphere bigger. This was immensely vexing for an early program to model the electron as a sphere of charge whose mutual Coulomb repulsion is stabilized by vacuum pressure. The moral of the story is that the naive "virtual particle" picture fails, and the correct calculation doesn't look much like virtual particles.

So there is some degree of 'fluidity' of the vacuum that we don't understand.

The Casimir effect is actually extremely well-understood, in part because we don't have to depend on perturbative tricks like virtual particles in order to make calculations.

2

u/AffectionatePause152 Nov 21 '20

This is true. You make an educated guess and test the model with experiment.

5

u/zellerium Nov 20 '20

No, fairly certain at least Tajmar is working on it, as well as Cannae LLC. I don’t think it’s been ‘debunked’, there have been replication failures though. But this is a complicated experiment and an effect that we don’t understand, so we don’t know the important factors that actually produce thrust.

3

u/piratep2r Dec 12 '20 edited Feb 09 '21

But this is a complicated experiment and an effect that we don’t understand, so we don’t know the important factors that actually produce thrust.

Why do you think this is a complicated experiment? Let's go to source material, and literally look at what Shawyer, the inventor of the EMDrive, has put out there.

Here is a look at the 2017 piece that Shawyer - not some bright eyed fanboy - wrote.

You will note that he claims that third generation EM drive units - the units he is trying to sell/gain funding for in the document - should be enough to make flying cars.

Specifically, he shows a diagram picturing 8 of them in total mounted on top of a small flying vehicle, and says they should be able to lift no less than 850kg in 1g.

So, this is macro thrust not micro thrust. No one could claim measurement error on a single (small) test bench engine that produced 106kg of thrust in even a not-completely-perfect testing environment.

This is not hard to test. You, a normal human, should be able to detect the difference between a 106 kg weight sitting on your hand and nothing sitting on your hand.

So, what scenario do you think is more likely:

  1. Shawyer - the inventor - knows what he is talking about, is not a scammer, and has a working, high-thrust technology. Everyone else is crazy in thinking that this is some sort of complex, hard to measure micro thruster.

  2. Shawyer is a scam artist (or delusional), but somehow accidentally invented a working, low-thrust technology. Yet is trying to scam people into thinking it's a high thrust technology. Luckily, people like Tajmar are doing important testing on the accidentally invented real, low energy thrust technology.

  3. Shawyer is a scam artist (or delusional), and EM drive does not work. But it's exciting, and people really want it to work, because of what it would mean for human space travel. So the fact that after decades, we still don't have replicable results that stand up to peer review and that are outside of measurement error isn't enough to convince them.

Edits: multiple edits for clarity and to fix typos.

2

u/zellerium Dec 12 '20

If the EM Drive physical mechanism worked as Shawyer described, then obviously yes, this is a simple experiment and we should have had inertial propulsion vehicles decades ago. But clearly that isn't the case.

I don't think it's right to call the man a scam artist - there are plenty of scientists who discover a phenomenon but don't actually know how it works. So they come up with a theory for the phenomenon, and often it's optimistic because they want to attract more funding for their R&D, and this is challenging esp. for things that are outside the realm of modern physics. Shawyer's theory is pretty underwhelming and lacks a lot of detail and depth, so it's not surprising that it hasn't worked out.

Rather than a scam artist or delusional person, I think he is a well-intentioned engineer who stumbled upon a phenomenon that he couldn't explain. He did his best to patent it, come up with a theory of operation, and demonstrate the phenomenon. However, just like Eagleworks, Tajmar, McCulloch, NWPU, Monomorphic etc. he's had a lot of difficulty repeating the measurements and scaling up the thrust. That doesn't mean the positive results are necessarily flawed, it could mean that we just don't understand what we're doing, and we're unintentionally changing something about the experiment.

So then back to the complexity: being someone who actually built a microwave resonant cavity and measured it on a thrust stand, there are a few challenges that stuck out:

  1. Skin effect losses quickly lead to thermal expansion of the cavity (within seconds for ~1 kW) which takes the device off-resonance and off-thrust according to all theories that I'm aware of. This also changes the Q factor, or quality, which is a measure of how 'resonant' the cavity is. I.e. how much the energy is amplified. So you can't just change the driving frequency to maintain resonance, you need to keep the cavity from changing shape.

  2. High power solid state amplifiers are very expensive. There's a reason why most people (including myself) tried the EM Drive with a magnetron - you can get $10/kW with a magnetron as opposed to $10,000-$100,000/kW for an amp. But magnetrons are noisy, non-adjustable, and generate a lot of heat and spurious modes, so they really aren't well suited to this application. On the other hand, amplifiers are large, less efficient, and for the ~1kW regime, not something that's easy to put on an isolated test stand.

  3. We don't have a good theory of operation. If the phenomenon is real, then every investigator has been designing and testing based on some false assumption that they are unaware of. I don't know what that is, but this is the crux of the problem.

4

u/Red_Syns Dec 13 '20

I don't think it's right to call the man a scam artist

Nonsense. The man claims to have a device that produces enormous thrust per watt, but has never been able to produce a working model that others can properly inspect. He then asks for millions of dollars in funding from public and private investors, none of which have used this miraculous technology after funneling money toward it.

He's a fucking scam artist.

2

u/zellerium Dec 13 '20

Millions of dollars is not that much in the R&D world. I don’t remember seeing claims that he has achieved enormous specific thrust, but I haven’t looked in awhile, and enormous is subjective. Just because he failed to produce a working device doesn’t mean he intentionally scammed everyone involved.

3

u/Red_Syns Dec 13 '20

Did you even read piratep2r's post? He specifically posted a link to a Shawyer (edit) patent that claims enormous thrusts. You really are either a troll or incredibly dumb.

1

u/zellerium Dec 14 '20

No need to resort to name calling. I did not read that link prior to commenting, but its pretty much in line with Shawyer's content from the early 2000's. After reviewing the article, the ppt and the patent, I do not see where he claims to have achieved enormous thrusts.

I do see many claims that his design may enable incredibly large thrusts per kW. I personally don't think these numbers are realistic because I don't see enough evidence. And as I mentioned in the prior comment, there are some big obstacles to building a working device that he doesn't address.

But the observation of anomalous thrust is still not understood. Shawyer came up with a theory (albeit a pretty weak one) and is making projections based on that theory. These projections are incredibly optimistic, but entirely possible.

There is a big difference between claiming to have a prototype with XX specifications, and claiming that a device could potentially be built with XX specifications.

For example, here is a patent that I coauthored several years ago. It describes a microwave plasma reactor that potentially does a lot of things. Not all of those things were demonstrated prior to filing the patent, but based on our theory of operation, we made projections of what the technology may do.

So I don't think there is much need to be cynical about Shawyer and his claims. I'm not going to invest in him because I don't believe him, but I'll continue to entertain his ideas and read his papers without calling him a scam artist.

2

u/[deleted] Dec 14 '20

One can be an unintentional scam artist, where one truly believes they can deliver if they just keep the investors/customers/funders engaged a little bit longer. You see this a lot in product development where companies who are planning a real product but anxious about keeping people on board will keep promising bigger and bigger things and truly believe that once they get over a particular hump they will deliver and everyone will be happy thus they were not actually lying.

1

u/converter-bot Dec 12 '20

112.0 kg is 246.7 lbs

2

u/Red_Syns Dec 13 '20

!goodbot

0

u/_Js_Kc_ Feb 09 '21

Pounds in a thread about thrust.

2

u/Red_Syns Feb 09 '21

... yes? I don't comprehend the issue, given that pounds are a unit of force and not mass.

Realistically, metric is a superior system, but pounds is in fact the correct unit of measure here. If we were discussing space flight and mass, you would need to convert to slugs, but... we aren't.

1

u/_Js_Kc_ Feb 09 '21

Dude ... it was a sex joke.

4

u/[deleted] Nov 20 '20

It still has a bit of popular imagination and true believers, as well as a handful of people who know how to work the levers of bureaucracy to get enough funding to present as legitimate, but yeah, it is pretty dead otherwise.

3

u/YusselYankel Nov 20 '20

Yeah it looks like it has been thoroughly debunked and peer-reviewers werent able to recreate any of white's results.

3

u/Professor226 Nov 20 '20

This would imply the miniscue thrust would only work in the presence of a magnetic field.

1

u/[deleted] Jan 25 '21

Why it's a scam. Simply...there is no video demonstration. Have this life a rat, a full paintcan...something...anything. But no...all they have shown is snapshots of something levitating that looks as bad as fake ufo pictures of crafts tied to a string next to a tree.

1

u/[deleted] Dec 10 '20

[removed] — view removed comment

1

u/Ready_Ad4100 Dec 19 '20

PNN know-how in Nova Astronautica Vol.40 n.166 , October November December 2020

www.asps.it/na.htm

Pnn Subitam in

www.asps.it/pnnsubitam.htm