NASA's Peer-Reviewed EM Drive Paper Has Finally Been Published
sciencealert.comThis was published November 17, 2016. It's been officially published for several months.
Huh! And a submission by a new account. Did some spammer manage to get points here?
November of 2016
There has been some good discussion on Reddit about how the thrust results shown in the paper are still most likely measurement errors due to thermal effects. It is a shame that they haven't released their actual data for independent analysis.
Link: https://www.reddit.com/r/Physics/comments/5ewj86/so_nasas_em...
I've been following along on reddit on several subs, including the EMDrive sub.
This is a fascinating study about the politics and social aspect of science -- i.e., how it's actually done.
I'm just a layman, but so far it looks like this is experimental error. I never knew there were so many ways to screw something like this up!
Having said that, this is a win either way. It teaches all of us about rigorous science, it allows far-fetched ideas to be taken somewhat seriously as long as there is some sort of experimental evidence, and it provides a forum for practicing scientists and interested laymen to cross-pollinate. It's a really good thing. (Only probably no warp drive involved)
I agree this incident has educational value, because it's like a toy research project. The science behind the EM drive and the means to understand why it could never work are accessible to laymen who only have to trust our most well-tested physical laws.
If you're curious, you can find an easy to understand theory about why breaking the conservation of momentum lets you build a perpetual-motion machine, creating infinite energy.
Then, you can find a paper from the inventor of the EM drive explaining why it won't allow that to happen. His explanation spectacularly violates special relatively in a way we could easily detect.
Yeah, but it's more than just getting the natural laws out and beating people over the head with them -- there's emotional involvement from the public, and that's terrific.
For instance, there are quite a few hobbyests that are building their own rigs. There's discussion about noise control, radiation leakage, resonance, and so forth.
For the more theory-minded, there's a great discussion about empirical data versus theory, which you allude to. At the end of the day, of course, if you've got data, you've got data. Once the errors are taken out of the system, observation beats theory hands-down.
I know scientists would probably much rather have a conversation around "This is science, dang it, go read a book!" but for us layman schmucks, the really cool part is a conversation around "This is why science is what it is"
(Note: I'm not addressing you directly. I've just noticed a lot of mockery and impatience from some of the scientific community, and that's a shame. Better to use this as a teaching moment in my opinion)
>Once the errors are taken out of the system, observation beats theory hands-down.
But how do you go about distinguishing signal from noise? That's ultimately the reason data say far less, on their own, than they seem to: because interpretation of data is at least as important as how you collect them, but interpretation brings in all the gooey things people really want to wish away. Or put more bluntly, observation can't "beat" theory, because theory is the way you decide which observations to make, how to carry out those observations, and how to understand the products of the observation. Theory and observation are inseparable; in a sense, all observation is at once theoretical, and all theory is at once observational.
> Once the errors are taken out of the system, observation beats theory hands-down.
But it seems that not all errors have not been taken out of the system
Paper listed in article, https://arc.aiaa.org/doi/10.2514/1.B36120, appears to cost well over a thousand dollars to access. I found https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201700... online; I think it's the same thing.
The first link loaded a PDF for me.
Ahh, it looks like I didn't notice the PDF link. My mistake.
NASA has published this paper. These guys presumably know what they're talking about. Moon landing, space shuttle, Voyager, etc. They ran actual experiments on this drive.
Why are half the comments here saying 'They must be wrong' - seemingly based on nothing more than a strong belief that NASA must be wrong.
This is the worst part of the internet. Amateurs and 2nd year college students dismissing months/years of hard work by actual professionals. They take all this work and "hand wave" it away in less time than it takes to make coffee.
The internet is full of amateurs and they are very very confident about their abilities.
Professionals don't always get things right, either, and reactionless thrust doesn't really fit into our best current physical model. That doesn't mean it can't exist - but, given the general usefulness of our current model in predicting how things will behave, there's reasonable cause for extraordinary skepticism in response to claims that one of its "can't happen" conditions is inaccurate.
Maybe the paper's conclusion is accurate! Maybe this physical "can't happen" actually can, and the model needs extending to account for that. It wouldn't be the first time. But it also wouldn't be the first time that a "can't happen" really can't happen, and the result suggesting otherwise is an artifact of the way an experiment was run, rather than an accurate description of a previously unsuspected physical phenomenon. Going by past examples, the latter is much more likely than the former. So there's nothing unreasonable, even for people like myself who aren't knowledgeable enough to evaluate the paper on its own merits, in reserving credulity until the result is shown by other experimenters to be reproducible.
I totally understand some scepticism, but there appears to be the archetypal response of 'Oh, I bet NASA hasn't thought of this ...' when it's inconceivable that NASA hasn't, in fact, thought of that.
Some of the most sensible comments I've seen here have basically said 'It seems to violate what we know of physics, so hopefully it's right and we have some interesting times ahead'.
It's the dismissal, out of hand, after a relatively extensive amount of research and study -- especially compared to what the armchair critics can supply -- that I find frustrating.
Yeah, sure, I get that it seems implausible, but it transcends hubris to know that it's simply experimental error.
This is the best part of the internet. Amateurs and 2nd year college students challenge professionals to make their months/years of hard work comprehensible. They take all this work and question it unless presented with hard, verifiable facts and data, sometimes over a coffee.
The internet is full of amateurs and they are very very eager to point out when they are not fully grasping something, in one way or another.
Lets be clear here, the people who ran published this test are also skeptical about this. However they did everything possible to reduce and remove errors from their calculations. This means one of two things, either our present understanding of physics is incorrect, or our present understanding of experimental physics and the ways errors creep into our experiments is incomplete. The scientists who did this test suspect the latter, however they've done everything they know to remove mistakes. Much like when we are troubleshooting why our computer won't start we don't jump to the CPU is dead, they also don't just jump to the big conclusion. It's still neat though because we'll still learn something meaningful, and you never know it really could open new understanding of reality.
I looked through the comments, but I don't think many commentators here are actually saying "I am 100% sure this is wrong". I am mostly hearing "there are a lot of reasons to remain skeptical". NASA certainly is an authority and I don't think most people here dispute their bona fides, but keep in mind the working models a working quantum vacuum thrust engine would disprove have even greater providence.
I'm skeptically optimistic about the em drive (I think it probably doesn't work but the upside is so great it's worth tinkering with)... NASA has been spectacularly wrong in the past. Arsenic life, for example. In many ways the em drive stuff has the same hallmark "press release-driven" science feel to it.
Except the Moon landing parts of NASA had nothing to do with it.
AFAIK it is research from their fringe science labs.
> Why are half the comments here saying 'They must be wrong' - seemingly based on nothing more than a strong belief that NASA must be wrong.
Nothing more than a strong believe?
Extraordinary claims need extraordinary proof and the paper doesn't have too much quality regarding the data.
Because extraordinary claims require extraordinary evidence, not extraordinary credentials.
I'm sure even NASA has there fair share of cranks.
This is true, but don't you also think that once extraordinary claims have this much publicity they warrant extraordinary investigation? If for no other purpose than to prove it wrong?
Chances are that this is just experimental error. But part of me really wants this to be true. That it's possible some crack pot shoved some microwaves in a tin can and created a device that may reveal a new phenomenon.
> This is true, but don't you also think that once extraordinary claims have this much publicity they warrant extraordinary investigation? If for no other purpose than to prove it wrong?
Absolutely, I'd be surprised if it wasn't happening already, within nasa and around the world. I'm guessing they're being a lot more thorough though, controlling for more variables and trying more permutations (different engine sizes, different materials, etc) to try to either isolate the cause or to rule some out. I'd suspect anything less would risk the experimenters being labeled as cranks, that's why we're not seeing direct replication efforts.
Seems like the previously leaked 1.2 ± 0.1 mN/kW is true. I look forward to seeing it tested in space to finally see if its real or not.
That's such a tiny thrust it might be quite difficult to measure in space. Orbits are complicated, what with complex gravitational variability of the Earth (mountain ranges, continental shelves, the fact it's not a sphere), the influence of the moon and sun, interaction with the magnetic field, solar winds, and down in low earth orbit even the last vestiges of the atmosphere.
Those forces are actually pretty well behaved and can be readily measured and accounted for. Also, light sails have a order of magnitude less power, and the Pioneer Anomaly [1] was smaller yet. Space is probably the best place to test something like this.
The Pioneer Anomaly was only detectable over several decades and a journey to the furthest reaches of the solar system. I'd expect a useful propulsion system to produce effects quite a bit more detectable than that.
This effect is about 1/25 the power efficiency of the lowest power ion thrusters. Output at this level over a very long period might be useful at the interplanetary level and maybe at geostationary altitudes, but the low earth orbit environment is actualy highly variable and unpredictable at this scale of effect.
Wouldn't variations in atmospheric drag negate any possibility of detecting the actual thrust component in leo? The trusts are small, as is the device, but any variation would be extremely hard to detect and measure. Please correct me if my line of thinking is wrong though, I'm not an aerospace engineer.
Couldn't many of those effects be accounted for by having a non-operating unit in the same orbit as the test unit, and looking for differences in the motion of the two?
Yes, all I'm saying is the orbital experiment would have to be well designed. It's not necessarily trivial.
China claims their testing a mock up as one of the experiments being conducted on the Tiangong-2
The quote of interest (being able to be tested in months) references another article where nothing has been committed but could be done in 6 months.
On one hand it's great that this is being reviewed and tested. The other hand, that it's not getting properly tested in space where it really can make a difference is somewhat saddening. Can anyone point to a committed space trial?
It's in the article. Some skepticism is worthwhile though.
http://www.sciencealert.com/the-impossible-em-drive-is-about...
The 'commitment' from that article is: "No launch date has been set just yet, but it could happen in as soon as six months' time."
Why would you test it in space?
I'm not sure I understand the reasoning.
The effects are small enough that there's some possibility that it's just measurement error. If you produce a drive that actually moves something in space, you have a real effect.
Space is a vacuum and has negligible gravity effects; put it in space, turn on the engine, see what happens. In theory it could propel something to nearly infinite speeds if it checks out.
So you know if it works in space.
What ever happened with the German result that showed no thrust when the device was hooked up to an on-board battery?
here: http://emdrive.wiki/Experimental_Results seems to be all the experimental results collected so far from various labs around the world.
Please link.
As always, the relevant XKCD: https://xkcd.com/955/
While I don't really believe it, I am intrigued by the possibility. It has been a long time since we learned anything truly new in physics. The recent breakthroughs (Higgs boson, gravitational waves, for example) were satisfying, but not surprising. I would desperately like to be surprised.
1. studies consistently are showing that this seems to produce thrust without expelling any matter
2. we know that can't be possible
I think most people are excited about this not because they think we just proved 2 to be wrong, but instead because we know 2 must be true, so what the hell is going on with 1???
Most likely we will find out that we are NOT violating the known laws of the universe, but we're "not violating" them in a very interesting way.
By far the most likely scenario is that something subtle but utterly mundane is happening and no useful thrust is actually being produced. You say that:
1. studies consistently are showing that this seems to produce thrust without expelling any matter
but this is in fact the first peer reviewed study, so we really only have a sample size of one (not to say other experiments are invalid, just that we have no reason to trust them). Even assuming it is down to subtle experimental error, we may still learn something interesting, of course.
Far less likely is that this is actually producing useful thrust, and regardless of how it is doing it, that would be extremely interesting, and in all probability, new physics. Even if true, I don't expect it to completely overturn our understanding of physics, but it would be very exciting.
Others have tried to replicate the results but got thrust in the null position[0]. This indicates that the amount of thrust being generated is so small that it's likely the result of instrumentation error.
[0]: https://tu-dresden.de/ing/maschinenwesen/ilr/rfs/ressourcen/...
Here's another article that proposes to explain why it works:
>studies consistently are showing that this seems to produce thrust without expelling any matter
Nope, others have been unable to reproduce their results. As for Eagle Works ... their data is crap. The paper consists of 18 data points and large amounts of variance. The largest thrust measurement comes from the middle power setting.
Furthermore, they are measuring (at most!) 120 micro-newtons of thrust. Someone correct me if I am wrong, but that's ~1/100 the weight of a penny[0]. Even if they can produce these tiny amounts of of thrust reliably, they still need to eliminate other sources of error.
Other false-positive results of similar devices have either generated thrust in the null condition or were later retracted after correcting for measurement error.
>I think most people are excited about this not because they think we just proved 2 to be wrong, but instead because we know 2 must be true, so what the hell is going on with 1???
The EM drive literally entails perpetual motion. We know that's impossible, yet someone always manages to sell a new version of it every few years.
>Most likely we will find out that we are NOT violating the known laws of the universe, but we're "not violating" them in a very interesting way.
There is a reason this is in a journal dedicated to publishing experimental results from aerospace engineers and not a physics journal. Peer review isn't magic, it just means two out of three people signed off on a paper being published.
[0]: Seems crazy small, math may be wacky off due to lack of sleep.
> The EM drive literally entails perpetual motion. We know that's impossible, yet someone always manages to sell a new version of it every few years.
Well the universe was created, so that seems to imply the energy can be created. We don't know that energy can't be created, just that the current laws of the universe don't allow for it, as far as we know.
Not that I believe this will violate that law in anyway. Even if the drive turns out to be real I suspect it will be something like photon entanglement, where it appears data is travelling faster than light but it's in no way helpful.
I'm not a scientist but it begs the question, how is 1.2milinewtons for 1KW input perpetual motion ?
The only way it could be Perpetual motion I can see is if I could somehow generate 1KW with that 1.2milinewtons which would be science fiction.
Basically, it's because as the drive keeps accelerating without losing mass, the velocity is proportional to the energy expended. However, it's kinetic energy increases with the velocity squared. Eventually, there is a cross-over point.
You can create infinite energy by placing a bunch of drives on the spokes of a huge flywheel.
See this paper for a more detailed answer:
My argument still stands you cannot ever reach such a cross-over point at the milli-newton/KW scale. If they call a much bigger fraction then we can call BS
Why not read the paper I linked instead of just making stuff up? Alternatively, show your math.
> When relativistic effects are taken into account, it is shown that the photon rocket can only reach energy breakeven as the accelerated mass asymptotically approaches the speed of light. Thus, any device with a thrust-to-power ratio greater than the photon rocket would be able to operate as a perpetual motion machine.
A photon rocket is 3.3 μN/kW, thus the EM drive is too efficient.
> Most likely we will find out that we are NOT violating the known laws of the universe, but we're "not violating" them in a very interesting way.
Most likely is still some sort of experimental error. I'd like it to be real but there is still tonnes of room for skepticism.
In case you missed it, the theory behind the EM Drive is also being used to explain galaxy rotation:
https://www.researchgate.net/publication/313580454_Low-accel...
I see no connection to the EM drive. The paper you mentioned suggests an alternative inertia formula, however it doesn't break conservation of inertia as far as I can see.
The "theory behind the EM drive" [1] is completely based on classical electrodynamics and therefore it's flawed. Classical electrodynamics conserves momentum and energy. It doesn't mean that the EM drive can't work though, it just means that this theory can't work.
[1] I only found this: http://www.emdrive.com/theorypaper9-4.pdf
Is this what you refer as the "theory behind the EM Drive"?
>Hubble-scale Casimir effect Isn't casimir effect very short range phenomenona? Seems like distances involved would reduce it to negligible levels compared with huge EM fields. Its like claiming weak nuclear force is relevant at galactic distances because "all the atoms add up". http://math.ucr.edu/home/baez/physics/Quantum/casimir.html
Why is it that EM advocates always seem to be dark matter-deniers? There's observational evidence for DM, a lot more than for the EM drive.
> There's observational evidence for DM
Um. Isn't that a contradiction in terms? By definition, DM is stuff whose existence is inferred by observations that contradict what we previously presumed to know. Hence postulate the existence of DM to close the gap between what we observe and what we "know".
There's observational evidence of something. Dark Matter is just the place holder for the something.
I don't know anything about this field but the language seems sound to me.
Is there a consensus on this interpretation v. "just adding more dark matter"?
It is unfortunate that the theory of Dark Matter doesn't have a cute parlor trick like the EM Drive.
> Is there a consensus on this interpretation v. "just adding more dark matter"?
This reminded me of https://xkcd.com/1758/
$200 bucks it doesn't pan out, what you say?
Ugh, science alert. sigh