back to article Leaked paper suggests EM Drive tested by NASA actually works

An unpublished scientific paper by NASA engineers has been leaked. It appears to show that the EM Drive – a form of space drive that appears to produce thrust by electricity alone, in violation of Newton's Third Law of physics – may actually work. The EM Drive is the brainchild of British inventor Roger Shawyer but is highly …

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1) Assuming it actually does work* - if "no one knows how it works", it is obviously just an assumption that it is "in violation of Newton's Third Law of physics", by which you probably mean Newton's Third Law of Motion.

2) There is nothing wrong with using a speel chekker.

* Let's wait until the publish & peer review phase is over, mmmkay?

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Speel chequer

Perhaps my dear mother was right after all, and I have a tick heed as my speel chequer just doesn't react at all when i fink "Third Law of Motion" butt write "Third Law of physics" but then gets up seat with perfectly nice world's like chequer and speel.

Anybody out there with a similar mother.

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Easiest way to check this...

Is to send a one-way gizmo out in space with said thruster attached to it and see what happens.

I said *easiest*, not *cheapest*.

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Re: Easiest way to check this...

I imagine that's the plan eventually, but they'll want to do all the cheap earth-bound testing they can before they get to the point of building a small satellite and seeing if it is able to station-keep using an EM drive.

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Re: Easiest way to check this...

One is being sent up on a cube-sat in the near future. It'll be told to try and maintain orbit for as long as possible, if it stays up for longer than the fuel will allow, the EM drive aboard must be working.

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Alien

Re: Easiest way to check this...

Allegedly the US are already testing it on their X-37B unmanned space-plane, and the Chinese have a version on Tiangong-2. I first saw the story here, but I'd take it with a pretty damn big spoonful of salt meself.

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Alien

Re: Easiest way to check this...

Allegedly the US are already testing it on their X-37B unmanned space-plane, and the Chinese have a version on Tiangong-2.

Why would they lift a pressurized water reactor into orbit to push clippy around??

a cube-sat

thing is bigger than a cubesat, especially with the power source and the radiator...

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Anonymous Coward

It's always worth waiting for peer review to take place before jumping to conclusions. However I would be surprised if there are any issues raised during review.

Have already been a lot of teams other than NASA working on these trying to work out what's going on. Would assume if the explanation was down to a flaw in the experiment it would have been discovered earlier. Independant work has been going on for at least 8 years already on RF resonant cavity thrusters in countries around the globe and no one has stepped forward with a simple explanation and work continues.

Heres hoping once we understand what is in action it leads to greater discovery.

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Headmaster

So these papers "leak"??

A tall order explaining how "energy" is transformed into *"momentum" while this particular way of Nature's working is not readily apparent all around us, or rips big holes of inconsistency into the fabric of logic itself.

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Headmaster

Re: So these papers "leak"??

the 60 millinewtons per kilowatt that is produced by the best ion drives. It sounds tiny, because it is, however it's still twice as powerful as the thrust produced by solar sails.

This depends completely on the size of the solar sail and its distance to the light source and the type of light. Same as for those panels, really.

Additionally, the solar panels will ALSO work as solar sail. This will be interesting, which one will win, the drive or the panels?

Plus, once you have subtracted the momentum from the energy (well .... you know .... ) you are still left with a shitload of surplus energy that you have to dump into space. You will need large radiator fins. Now you have a photon-drive of infrared light, too!

Plus, I don't see why there is an assumption that there is a linear relationship between "momentum generated (into a preferred direction)" and "energy needed". Might as well be logarithmic for example. We are in unicorn land, all bets are off. The law of increasing entropy has gone overboard, next someone will use this to pull NP into P.

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Re: So these papers "leak"??

"while this particular way of Nature's working is not readily apparent all around us"

It may actually be additional proof that the universe really does have more than the 3 dimensions we perceive (as does the way a neutrino keeps rolling through various flavours when observed)

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Re: So these papers "leak"??

I don't know, but the dimensional thing is not really magic sauce to explain stuff (much as quantum mechanics is not magic sauce for consciousness)

I remember vaguely that 4 dimensions (not 3) is a magic number as some very special properties become apparent in topology or quantum field theory or both, can't remember... but unless there is strong evidence, 4 it shall remain.

This doesn't preclude one from declaring other degrees of freedom (e.g. energy) as a dimension, but you cannot actually travel along those.

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Re: So these papers "leak"??

"It may actually be additional proof that the universe really does have more than the 3 dimensions we perceive (as does the way a neutrino keeps rolling through various flavours when observed"

The neutrino oscillations show the neutrino has mass because otherwise it would be incapable of changing but why does it imply multiple dimensions? Neutrino oscillations does show, along with many other things, that our understanding of physics is incomplete. The unknown physics could include more dimensions but equally may not. I think it should be assumed we have the usual unless a convincing experiment shows otherwise. Equally if the EM drive really is an effetc that cannot be explained using conventional physics, and we should be sceptical, why does it imply more dimensions?

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"One theory is that protons fired around the nozzle are providing thrust, ..."

Where do the protons come from? This represents a loss of mass so how long will the motor last?

(If you're throwing protons out, you'd need to throw electrons out to balance the net charge. This is quite easy in a vacuum so not a big problem.)

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DJO
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Photons are massless and can be thrown off when an electron changes orbit so there is no change in mass also photons have no charge so there is no need to balance any charge.

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WTF?

@frank ly

"One theory is that protons fired around the nozzle are providing thrust, ..."

AFAIK it does not have a nozzle, only two metal plates of different sizes.

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@DJO

Proton != Photon

...Although given the preponderance of typos in this article, the author may have meant photon, just like they probably meant xenon gas, rather than old Intel processors.

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Boffin

Photons do have momentum

momentum= (Planck constant) / (wavelength)

If so if this is the mechanism then laser diodes would be better.

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Headmaster

"Photons are massless and can be thrown off..."

<pedant>

Photons have no rest mass but the do have inertial mass (E=mc^2 and all that) otherwise solar sails won't work...

</pedant>

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They have MOMENTUM!

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It just might be low energy photons providing the thrust

I don't see why this is so puzzling. If it works it is probably due to photons being ejected out of the 'nozzle', after all photons are the force carrier of the electromagnetic force. the photons don't have to be in the visible spectrum either, they could easily be microwave radiation.

If the sun's mass is kept from collapsing inwards by the light pressure of photons why can't a simple motor operate by using photons: energy produced by solar radiation converted into electricity and then further transformed down into microwave photons. it doesn't even violate Newton's third law!

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Re: It just might be low energy photons providing the thrust

Photons having momentum is first level undergrad stuff - I'd hope the NASA people would have discounted that when considering possible causes of observations.

Plus, at very best photons emitted back in the direction of incident light would replicate the behaviour of a reflective solar sail - as the engine allegedly gives twice as much thrust as that, presumably something else has to be a factor.

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Anonymous Coward

Re: It just might be low energy photons providing the thrust

I suggest you read their paper - they have thought of this issue and accounted for it and a number of other possibilities. It's an impressively thorough document.

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Re: It just might be low energy photons providing the thrust

As AC has pointed out - "I suggest you read their paper - they have thought of this issue and accounted for it and a number of other possibilities. It's an impressively thorough document."

I shall indeed read their paper, then.

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Re: It just might be low energy photons providing the thrust

"Photons having momentum is first level undergrad stuff"

The point is that the microwave photons in question are being emitted into a _sealed_ container, so the momentum imparted in one direction should be cancelled when they hit the other end of it.

The fact that it isn't 100% cancelled out is where the controversy is coming from.

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Unhappy

Re: It just might be low energy photons providing the thrust

Here's the problem with that idea.

They are saying this thing generates 2x the thrust of a solar sail yet if it is photons they are only being output at a single frequency (that of the magnetron), whereas the sail reflects the whole of the solar spectrum.

Something does not seem to be adding (or multiplying) up.

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Sceptical, but...

Lasers can work as propulsion, I can't see how this can be working, note the propulsion is so small that you can be looking at some sort of systematic error, like you can't shield from the effects of orbit or moving masses. They need three of them at right angles.

"One theory is that protons fired around the nozzle are providing thrust, but it's going to take a lot more testing to see if that's true."

Do you mean photons? Protons would use up the material of the engine.

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Re: Sceptical, but...

Ablation sounds like a more sensible explanation than new physics. At least that's what Occam told me.

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FAIL

It's a scam.

If this is the actual paper that is supposed to come out in December I can see why it wasn't published in a physics journal. There are a plethora of things wrong with it. So let's start.

In part B they claim a TM212 mode but I'm not exactly sure how they know how to deduce that and how they know how to tune to that mode. Even in their section about tuning they describe how they think the are in resonance but this doesn't mean they know if they are in some particular mode. I'm not an expert in cavities but it seems to be they should have consulted someone who is. They then claim that there are no analytical solutions for a truncated cone, which is not true at all, see here. So right off the bat their understanding of cavities is called into question. They also don't say if their frustum inside is a vacuum, which I think is important if you're going to set up an electric field inside.

They say they put the RF amp on the torsion arm itself. This doesn't seem like a wise choice if they want to reduce all possible systematics.

In their vacuum campaign section they discuss simulated thermal effects but don't say what they used for this simulation. What model did they use, what assumptions were there, etc. If there is a standard piece of software they don't say this either.

In their force measurement procedure section they have a very convoluted and confusing way of measuring force which I don't think matches with their earlier model. One simple way they could have done it is take data with their optical setup then fit it with their earlier thermal model. If they got something significantly above their background model then they might be able to say more. But what they seem to do is record some time series data, what look like pulses, and fit parts of it to linear models to find different parts of some pulse they are looking for. That is a very undergraduate way to do this. They are - from my reading of this confusing method - simply fitting different parts of a pulse to determine what part of the pulse describes a calibration versus other pulses from something else, like a purported thrust. There exists technology that was developed in the 1980s that allows you do do these measurements much easier than they are doing, with much cleaner and clearer results, called NIM, but for some reason they are using this dubious method which likely won't give clear discrimination between signals.

Then they describe different configurations and their effects. The only thing I have to say about this is that it's not clear to me they couldn't have moved electronics outside of the testing area. I've worked with high voltage electronics in a very precise and sensitive test setup before an all of our data acquisition and power supply electronics were easily placed outside the test area, using the technology I mentioned before.

After that they describe force measurement uncertainty, which is great because they didn't have that before. They describe the uncertainties on their measurement and calibration devices. That is fine but these constitute random errors, not systematic errors. The only systematics they talk about are the seismic contributions, for which they quote a number without saying how they arrived at it. They say this is controlled by not doing tests on windy days but that doesn't account for everything since seismic activity, especially from the ocean, can occur without the wind. So it's unclear where they get this number from and if it's at all accurate. This is very dubious. They also cannot control for all low frequency vibration with one method either. Different frequency ranges are usually damped out with different methods. They then say their thermal baseline model contributes some uncertainty, which is true, but then they go and give a "conservative value", which strongly implies they pulled this out of a hat and didn't actually analyze anything to arrive at that number. So I call into question that value. Table 1 tabulates measurement (random) errors then adds them. It looks they quadratically add them, which is correct, but if you worked it out then they did some necessary rounding and didn't keep with the rules for significant figures. They classify seismic and thermal errors as measurement errors, but they are not. If seismic and thermal errors give a continuous shift in your measurements then they should be counted as systematic errors. The authors seem to not understand this.

Their force measurements in table 2 don't seem consistent with what you'd expect to see with increasing power. This says to me there are systematics which they did not account for. In this table they assign an uncertainty to the measured valued which is the one previously discussed. If they has taken data properly and did a proper analysis, the result from that analysis (which should including fitting to their earlier described model) would give different uncertainties for each result. This is standard practice and this is why error analyses are usually done at the end of studies, not in the beginning or middle.

After, they attempt to make some null thrust tests in which they attempt to show that if the z-axis (think in cylindrical coordinates) if parallel to the torsion beam it should show no "thrust". The beam clearly is displaced but since they claim it is not "impulsive" that it is not a true "thrust" signal. This is incredibly disingenuous since it is clear from their plot that something happens with the RF is turned on. The whole idea of impulsive signals doesn't seem correct either since it says to me that they turned they RF on, saw what they wanted to see them turned it off right away. For example in figure 13, would that upward going slow continue to infinity? Probably not. But it's not clear from these plots what the real behavior is.

They then to go on to describe sources of error. At first glance this is great, but upon further reading it looks like an error analysis I would have received from one of my undergraduate students. They are all good sources of error but not a single one was quantified or studied in any detail. At best they simply state in a few sentences why this or that is not important but don't actually back it up with any numbers, which would be proper procedure. This is a huge mark against them and this alone should call into doubt all of their results. But...

They did absolutely no controls. A null test and calibration pulses are not controls. A control lacks the factor being tested (NdT's Cosmos explains this very nicely, episode 5 I think). For that to have been done they would have needed to test several different cavity types: no cavity, rectangular cavity, and most importantly they should have tested a regular cylindrical cavity since this is closest to a frustum. Only then should they have done their frustum measurements. Based on this, their poor treatment of systematics, and their lack of a good method to analyze data (there are no statistical tests mentioned throughout), none of their results should be trusted or given much weight.

They finally go into and start talking about quantum mechanics and how different interpretations could apply (QM doesn't apply here). They also talk about debunked crackpot ideas like Stochastic Electrodynamics (SED), and the Quantum Vacuum Plasma which is complete and utter crankery to anyone who has sat in a half semester of quantum field theory.

tl;dr: It's no wonder why they couldn't get this published in a physics journal. Their experimental and data analysis method are at best at the level of an advanced undergraduate, and they have absolutely zero knowledge of any advanced concepts in physics, which they demonstrate in their discussion section at the end.

This paper should absolutely not be taken as evidence of a working emdrive. And so it remains pathological science.

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Thumb Up

Re: It's a scam.

The upvote train is now arriving at the station.

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Thumb Up

Re: It's a scam.

Instant peer review, at TheRegister fora :-) I'm always amazed what kind of beasts lurk here.

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Re: It's a scam.

I would not call it a scam. Rather a poorly conducted and wrongly analyzed experiment. It s what happens when the researchers believe too much in the effect they are looking for. The Cold Fusion [1] is one example, The "Weber bar" [2] detecting gravitational waves is another. Both sets of experiments still have their believers but both are unreproducible and therefore cannot be treated as good science.

[1] http://www.nature.com/nature/journal/v489/n7414/full/489034a.html

[2] http://www.sciencemag.org/news/2016/02/remembering-joseph-weber-controversial-pioneer-gravitational-waves

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Anonymous Coward

Re: It's a scam.

I am so, so tempted to downvote just to be that guy. Really interesting read, thanks.

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Physical possibilities

Outgassing or ablation of the materials, e.g. glue solvent evaporating, plasticisers in electrical conductors evaporating and so on.

Interaction between electrical currents and earth's magnetic field.

Solar wind

Microwaves or other EM radiation leaking out of the end. They have momentum, after all.

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Re: Physical possibilities

An should all be easily detectable and I'm sure NASA or the many other teams working on this have looked for them all.

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This post has been deleted by its author

FAIL

"Newton's Third Law of physics" (sic)

aka "Newton's Third Law of Motion" in the rest of the universe ;-)

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Hopeful, but...

I'm going to wait until the cubesat has gone up and done it's thing - I really hope that this does work, but until an actual physical test in space gives similar results, i'll remain sceptical.

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Battery plus Faraday cage?

It's puzzling that the experiment only uses only a couple of hundred watts. Why then didn't they mount the device on the torsion balance together with a battery powered RF generator and a programmed test controller inside a non-gas-tight box in order to provide electrical, magnetic and thermal shielding?

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Re: Battery plus Faraday cage?

> Why then didn't they mount the device on the torsion balance together with a battery powered RF generator and a programmed test controller inside a non-gas-tight box in order to provide electrical, magnetic and thermal shielding?

Because all of those things add extra interactions, heat, etc. This is a test of whether the drive itself creates thrust... not whether the battery does, or the generator, or the test controller..

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Re: Battery plus Faraday cage?

"This is a test of whether the drive itself creates thrust... not whether the battery does, or the generator, or the test controller.."

Heyyyy, awesome! A little while back we had no EMDrive at all, and now we have even batteries and generators and controllers creating thrust! Astounding progress...!

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Coat

" the drive could be used to keep satellites aloft indefinitely or even to journey to other planets – if you stacked a lot of them together."

Wouldn't you need to get to the planets first, and then need some very powerful equipment indeed in order to move them around and stack a lot of them together?

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Boffin

If the EM drive works it's not just physics that's broken but mathematics

Conservation laws, like the conservation of momentum that the EM drive would break if it works, can be derived mathematically, see Noether's theorem. The only way the EM drive could work within that framework is if the entire universe is a dissipative system, an assumption which is more likely to produce a planet sized amount of pseudo-scientific bullshit about quantum decoherence than useful science.

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Re: If the EM drive works it's not just physics that's broken but mathematics

Conservation laws, like the conservation of momentum that the EM drive would break if it works, can be derived mathematically, see Noether's theorem.

Yes but you have to assume Langragian mechanics or at least some action principle to do this and if you are going to make such a massive leap as conservation of momentum is broken then the whole basis of mechanics is undermined and you can forget an action principle/langragian etc. This is incredibly unlikely and the obvious explanation is just errors in the experiment. Arguing that you can derive conservation of momentum using Noether's theorem and symmetry is fine but to do it requires assuming a framework which is exactly what the observation if real would disprove.

An extraordinary claim like this requires extraordinary evidence and a single dodgy experiment with no peer review is not it. I think conservation of momentum will prevail.

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If the EM drive works it's neither physics or maths that is broken

Just our understanding of them.

If it works, the fact we don't understand why just tells us that our current theories need to change - it will be an interesting time for certain researchers.

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Re: If the EM drive works it's neither physics or maths that is broken

Some egos might be damaged beyond repair through.

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More bad physics (or bad writing)

I don't buy the part about it being "twice as powerful as the thrust produced by solar sails". I believe they mean twice the thrust for the same energy input. However, solar sails do not need electric power. Therefore they may have much more than twice the area of solar collectors with the same weight. And I'm not sure they've taken into account the effectiveness of changing solar radiation into electric power.

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Re: More bad physics (or bad writing)

Solar sails wouldn't work very well outside the solar system, not without building a huge arse laser to continue to push it, this if it does work would would independently of solar radiation and thus can continue to accelerate all the way to the star or if you want to stop at the star, to midpoint before you start slow down. .

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Years ago I had to investigate an issue on klystrons. They would visibly detoriate (on the inside) from metal ions being ejected due to being bombarded with stray electrons (the design was missing a little circular "barrier" that the competing vendor had. Hence, my guess: it's actually metal ions being ejected. The ones that escape through the "exhaust" (because the rest hits the "motor") provide the micro) trust. No violation at all of classical mechanics. Should be easy to verify. Measure the displacement of a metal foil placed behind the exhaust.

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This been the most suggested theory to date, I presume people already checked it out.

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