The Fact and Fiction of the NASA EmDrive Paper Leak | Hacker News Reader

The Fact and Fiction of the NASA EmDrive Paper Leak

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86 pointsAliCollins80 comments

James Woodward's one of the old names in propellentless thrust --- he's been working on Mach Effect based systems for a long time now. His approach is my favourite of all the anomolous science thruster systems, because (a) he actually has a testable theoretical model to back up his experiments, and (b) he doesn't talk about it much; in the fairly rare interviews, he tends to be focused more on coming up with ways to disprove his experiments, rather than self-aggrandisement; which to my mind is the main mark of a serious scientist.

By which I mean to say, in the nicest possible way, that he's not an impartial observer when talking about this thing, so it's worth being careful about what he says.

As an electric propulsion engineer used to measure thrust in the uN range, what disturbs me much more than thrust levels close to the sensitivity threshold is the fact that thrust is only detected some 10-20s after the RF is turned on (figs 9,8,13). I am rather confident that there is no physical time scale in the RF generation process that would account for a 10-20s ramp, and this would contradict their own report of the fast RF power stabilization. It definitely looks like thermal drift; in fact, thermal drift is _always_ the first thing to suspect when you get strange measurements with a low thrust balance.

It appears as well that the authors have conveniently prepared an answer for this objection with fig.5 which attempts to mislead the reader by suggesting that the very slow evolution of the balance displacement is to be expected as an artifact of the combined effect of thermal drift and RF pulse onset. But conveniently, the time units are arbitrary so that hopefully nobody will notice that RF onset was assumed in that figure to have exactly the same characteristic time as the thermal drift... When all measurements actually show that RF power stabilizes much faster.

> which attempts to mislead the reader

Even if you're right, assuming malice seems premature and pessimistic.

NASA seems to be minimally involved.

The group has been working five years in their own time in this small laboratory with shoestring budget. White has a day job in NASA and he and others are working with this project in their free time. To best of my knowledge - and correct me if I'm wrong - NASA only gave them $50,000 and a room in Johnson Space Center 2011. They don't seem to be involved in any other way but "NASA Eagleworks Laboratories" makes it sound like official NASA organization.

Their results are consistently close to the detection threshold of their sensors. They are always flirting with the measurement error.

I think your view reflects a misunderstanding of how NASA works. The vast majority of the research done at NASA is done by small teams working on shoestring budgets.

Where do you get the idea that they did all of this research on their own time?

The team he claims to lead seems to be nonexistent in NASA organization. Biography: "Advanced Propulsion Team Lead for the NASA Engineering Directorate at JSC"

Considering that wording is from an official NASA biography, it's probably not non-existent:

    He currently serves as the Advanced Propulsion Theme
    Lead for the NASA Engineering Directorate and is the
    JSC representative to the Nuclear Systems Working
    Group. In his role, White is serving to help the
    Agency incorporate high TRL advanced power and
    propulsion technologies into near and mid-term human
    exploration architectures. He also is pursuing
    theoretical and laboratory research on developing
    lower TRL advanced propulsion and power technologies
    in the advanced propulsion physics laboratory known
    as Eagleworks that is located at the Johnson Space
    Center.

https://www.nasa.gov/ames/ocs/2014-summer-series/harold-whit...

That's not official NASA biography. It's the biographical information he himself provided for summer series video presentation.

Most of NASA's work isn't public. My group happens to have one project on NASA's GitHub. Aside from that one project, my group of a dozen full-time researchers would seem to be nonexistent to the public too.

the paper is reporting milli newtons and claims the measurement device can measure micro newtons - or am I missing something?

No you're absolutely right. This is more a holy crap paper from Nasa, this actually might work.

The paper is actually reporting measurement of millinewtons with 40/60/80 watts, and estimating that when pushed up to a 1kW it would generate micronewtons.

Wait ... a millinewton is 1000 micronewtons, not the other way around. Not taking a position on this issue, just posting a clarification.

I stand corrected. They appear to have measured forces in tens of micronewtons while the error is in single digit micronewtons. Still the confidence interval is an order of magnitude smaller than the measured force which is not bad.

>They don't seem to be involved in any other way but "NASA Eagleworks Laboratories" makes it sound like official NASA organization.

If the NASA name is being used unofficially in such a public manner, wouldn't NASA do something about it?

It really comes down to what the management at NASA JSC wants to do about it. As a non-research oriented center, they don't seem to care very much. At the research centers, I suspect it would be a different story.

Not necessarily if there is no harm from the association.

NASA encourages people to do independent research. If they NASA gave them small grant and facilities in JCS, they show their support even if they don't take them seriously. That's part of scientific openness.

There is harm from the association, if the association is not accurate.

I've linked to it before on HN, but NASA's grand road map document includes a section on testing advanced propulsion ideas, which is what this lab is doing.

NASA's involvement is minimal, in that the resources dedicated to it are minimal. But it would be wrong to take that as some sort of implicit disavowal by NASA.

Rather, it's probably just reflective of a reasonable approach to budget prioritization. "Show something good for a little before I give you a lot" is a common approach to budgeting for speculative R&D.

Edit: here's my earlier comment

https://news.ycombinator.com/item?id=10497100

Actual paper from NASA recently on EmDrive (from Eagle Works) https://news.ycombinator.com/item?id=12906254

Actual paper: https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

So far I've failed to grok the many arguments for and against this drive's "impossibility". I'd love to find an ELI5 for it.

I think at this point, I'm resigned to waiting for an emdrive cubesat to just prove it once and for all: http://www.popularmechanics.com/science/energy/a22678/em-dri...

Against is pretty simple

Argument #1: it violates Newton's Third Law of Motion.

Argument #2: every time they improve the test apparatus, the measured force declines and is "coincidentally" close to the measurement limits of the apparatus.

Argument #3: It was originally designed based on a misunderstanding certain principles of Physics. Now they are trying to find a new explanation for why it works. What are the odds that you misunderstand physics, design something based on that misunderstanding, and that it then works in a barely-detectable way due to "unknown mechanism"?

Aren't new physics drawn from violations of old laws?

Yes, which is why violating a known law isn't automatically disqualifying. But it is highly suggestive, and requires extremely good evidence to surmount. So far, such evidence has not been forthcoming, so this remains a good reason to doubt.

Every so often, something comes along that overturns an established law, like the photoelectric effect or the Michelson–Morley experiment. But the vast majority of the time, the laws remain intact and it's the claim which is somehow flawed. (See the Pioneer anomaly for a recent example where new physics was long considered as a potential explanation, but it ended up being a completely mundane effect.)

This is not the first experiment undertaken by Nasa/Pentagon/Boeing or the DoD. As well as similar measurements confirmed by other research teams (including foreign teams).

I totally agree it requires drastic evidence, but it could be explained by another physical action not necessarily the violation of Newton's laws or effects that supersede those laws like quantum effects

https://drive.google.com/file/d/0B7kgKijo-p0idV9tcmVIVzZrdTQ...

http://www.ibtimes.co.uk/emdrive-exclusive-roger-shawyer-con...

http://www.slideshare.net/KurtZeller/investigation-of-a-part...

If it's another physical action within known physical laws, then nothing interesting is happening and it's a failure of the experimental setup. Yes, many experiments have been done, and none have conclusively disprove it, but at the same time none of them have conclusively shown that something is going on either. The detected effect remains well within the realm of potential error, so until that uncertainty is resolved, "error" remains a much better bet than "new physics."

>If it's another physical action within known physical laws, then nothing interesting is happening and it's a failure of the experimental setup

I'm not sure what makes you think this. There's no failure in science when an effect is observed and it's explainable within the frame of current theory. If that was the case every experiment I've done would have been a 'failure.'

With the experiments that showed a result, that result is not explainable within the frame of current theory. The whole purpose of the experimental setup is to isolate the test article from any possible interactions that could exert force on it, other than the one being tested. If the results seen so far are due to mundane interactions, then that isolation didn't work. Is that not a failure of the experimental setup?

IIRC, the recent tests are to reduce experimental error, not 'mundane interactions.' Just because there may be a way to explain it within the frame of current theory that the original researchers did not pursue or understand, still doesn't mean the experiment failed.

So, thermal radiation slowed the Pioneer spacecrafts. 'Thermal' is a type of Electromagnetic (EM) radiation, right?

Doesn't that make it an EM Drive?

Why the cone apparatus? What is preventing the intentional design of a spacecraft that uses thermal radiation (or Thermal Recoil Force) similar to the Pioneer spacecraft?

e: The replies indicate the answer is that this could be built but the effect is to weak to be practical. Which I find to be a completely acceptable answer, thanks.

Light has effective mass. It's well known that you can shoot light in one direction for a tiny amount of thrust the other way.

The device under consideration is special because if it works it is a reactionless drive. Nothing is coming out of it.

Light actually has momentum but not mass. Calling it effective mass isn't far off, but sometimes my pedantic physicist kicks in.

The proper term I'm used to is "relativistic mass", but I didn't want to make the discussion complicated. Would you not phrase it that way?

That makes it a photon rocket, which is nothing new. It's a logical consequence of the fact that light carries momentum, which is part of Maxwell's electromagnetic theory from 150 years ago. It's not very practical unless you have an extremely dense power source (nuclear fission won't cut it, you need fusion or antimatter) so it's more of a theoretical toy at this point.

What's interesting about the EmDrive's claims is that it supposedly produces far more thrust for the power that goes into it than would be possible from a photon rocket.

(The Pioneer anomaly wasn't because nobody realized that thermal radiation would act as a photon rocket, but rather that the effect wasn't correctly calculated. The theory is pretty simple, but it gets complex when you apply it to a real spacecraft with complex shapes, non-blackbody materials, and temperature gradients.)

You have to look at it in terms of a barrier. It's not impossible to break it, but it requires a lot of "oompf". The greater the violation, the greater the "oompf" required.

So, because this thing would change basically all Physics books, there's a huge burden on them to prove it beyond any shade of doubt. Forget about flirting with detection error; it should be as clear as the sun rising in the morning.

Please note that relativity, big as is was, was only at a low-to-medium level of "oompf". It didn't change quite everything, far from it.

Though I totally understand your point.

I would argue relativity was a tectonic shift in how we understand physics. These ideas existed before Einstein in mathematics/ geometry (Grassmann & Reimann). But they were just ideas and not a full-fledged theory.

And don't forget, violating Newton's Third Law of Motion also violates the conservation of energy, linear momentum, angular momentum, and thermodynamics.

https://www.lhup.edu/~dsimanek/museum/themes/NewtonsThird.ht...

There's a claim that it's just basic physics of microwaves bouncing around. That one's nonsense; from the article, "Woodward likened explaining the results seen at NASA purely in terms of microwave pressure to arguing that you can accelerate a car by getting in the driver’s seat and pushing on the windshield."

As that suggests, the drive would violate conservation of momentum as we currently understand it. It would also violate conservation of energy. Because of relativity, there's no such thing as absolute velocity, so the thrust can't vary by velocity. Since kinetic energy is proportional to the square of the velocity, but the acceleration is constant for a constant energy input, there's some velocity at which you're gaining more energy than you're putting in.

So if it does work, it'd be radically new physics. But there are various ideas for how it might work, like Woodward's, which is derived from general relativity and involves an explanation of inertia; he's been working for decades on reactionless drive experiments based on that idea. We don't currently have a generally-accepted explanation of inertia, so who knows.

I rather like the "everything is quantized and this is a result of accumulated truncation errors" theory.

The arguments against boil down to "Any reactionless drive must by definition violate conservation of momentum." We shouldn't reject any scientific conclusion as unquestionable gospel, of course, but off the top of my head I'm not sure that I can think of any fact about the laws of nature that I consider more firmly established than "momentum is locally conserved". (I'm a physics professor, for the record.) Conservation of momentum is part of the bedrock of everything from relativity to quantum field theory, so if you throw it out, you'll need to come up with entirely different (seriously: entirely different) replacements for those theories that nevertheless manage to reproduce their hundreds of enormously successful predictions (to just as many decimal points). Again, it could be true! Keep an open mind! But if it is, then literally every discovery in (say) particle physics in your lifetime has been a fluke: just dumb luck. You can decide how to balance that likelihood against the evidence presented thus far in favor of the drive.

I'm really not sure what the argument against impossibility is, apart from a fervent longing for something of the sort to be real. (A longing that I share, for what it's worth.) They claim to have some data showing that something really is generating thrust, but as I recall some experiments have shown comparably large results in both the "actual test" and "control" conditions, so I'm not sure what to make of that evidence.

  But if it is, then literally every discovery in (say)
  particle physics in your lifetime has been a fluke: just
  dumb luck.

Why couldn't conservation of momentum, as we understand it, be incomplete, like Newton's Laws, rather than wrong or coincidental?

Note that I'm not grasping at straws wrt the EmDrive. The distinctions between incompleteness and error is far more interesting to me, especially in the context of science. And I'm curious if your statement was more than a rhetorical assertion.

> I'm really not sure what the argument against impossibility is...

It's humility. It's admitting that there are things we don't know, and that some of them could give exceptions to the things that we do know.

I think that "willing to be proven wrong, but requiring proof" is the correct stance.

If you have an em-drive cubesat, just putting that (battery-powered, closed system) on a balance beam / torsion pendulum in a vacuum chamber is a more rigorous experiment than anything that's been done so far.

I know absolutely zero about rocket physics or quantum mechanics but isn't this a fairly easy and "cheap" thruster to prototype and test in actual space?

Nothing beats real world results, and this doesn't seem that hard to test. It might even be faster and cheaper than what's already been done, no?

No one will pony-up the millions of dollars it will need to design, build, test and launch a satellite based on (possibly) unconfirmed science.

Yet they will gladly throw away ten times that amount investing in a silly app idea on the off-chance it will be the next facebook or snap chat...

In fairness, we know Facebook is physically possible. Not so reactionless drives. If a Facebook is unlikely, a reactionless drive is spectacularly so.

If they are possible, the question of where all the aliens are becomes much more acute. If it's actually cheap to accelerate mass around the universe we ought to be crawling with visitors.

If it's cheap to accelerate mass around the universe, spreading beyond one planet is easy, but provides less insulation against non-natural disasters, like species-ending war.

Couldn't you theoretically take one of these way out from Earth, turn it 180, and wait for a massively powerful kinetic energy weapon to return?

"Cheap to accelerate mass" just sounds like a crazy weapon

Perhaps we are 0.o

I don't think the claim is free energy. The claim is no propellant. So you might still need tons of energy to get a decent acceleration.

If it's working, it's just not clear by what mechanism the energy is being converted to momentum.

Or it might just be that reactionless drives can make nukes look like firecrackers, while presumably also being a lot harder to restrict access to. And thus would make a very good 'great filter' candidate.

You have left out the part about the vast distances we still need to cover. Accelerating mass could very well be cheap enough, but HOW fast we can accelerate to still matters.

Perhaps they're on the other side of the galaxy, or in a different galaxy altogether and the EmDrive will only ever reach top speeds near that of a Ford Pinto.

I believe that if the EmDrive produces real force its top speeds are, in a vacuum, only limited by relativity and the amount of energy it can carry.

That's true of any propulsion system, isn't it?

yeah

No, most other systems run out of reaction mass first. With this and a good fission reactor you are halfway to everywhere.

So I don't get any points for E = mc² ? :)

In all seriousness though, I was noting the parallel "limited by … the amount of energy it can carry" and "limited by the amount of mass it can carry" in the sense that, yeah, you're going to be limited by what you can take with you.

No, real propulsion systems also require propellent

There are still incomprehensible numbers of stars, and awe-inspiring distances between them. Even if acceleration is cheap, there are only a few thousand stars that would have been reached by any human-produced signal yet -- and the chances of one of those containing intelligent life, the chances of those containing intelligent life that happens to detect our signal, the chances of those containing intelligent life that detects our signal and also has a space program, the chances of those containing intelligent life that detects our signal, has a space program, and decides to mount a voyage to Earth, the chances of those containing intelligent life that detects our signal, has a space program, decides to mount a voyage to Earth, and would have been able to get anywhere close by now...

edit - bad math deleted. thank Tossrock for the correction.

No it wouldn't. At a constant 1g acceleration, you're in the .9c range in less than a year. So to get to Alpha Centauri would take < 6 years, accounting for acceleration and deceleration. And because you're constantly accelerating, and accelerating to relativistic velocities, you would experience dramatic time dilation as well, meaning the amount of time passed for the ship would be even less.

People are at least claiming to be sending them up: http://www.popularmechanics.com/science/energy/a22678/em-dri...

If I won the Powerball Lottery today I would do it.

At the extremely low level of thrust we're talking about here, I suspect it would be a lot harder to be certain about removing all sources of error if they did this in space. See also Pioneer Anomaly.

The article mentions that the test was ran at only 80W of power, surely that could be scaled up to a few thousand watts and a more appreciable result could be seen even with another ground based test?

I think at those power levels you start vaporizing significant amounts of metal - the walls were heating up a fair bit at current power levels. You might be able to plate to increase reflectivity at GHz (gold, maybe something else is better up there, could do multi-layer metamaterial). But if you're vaporizing metal on the walls that's going to act like a propellant, so it will be very hard to distinguish what's causing the thrust (since thrust via propellant can be much stronger per Watt than the proposed propellant-less technique).

Word on the street is that one is already in space on the USAF X-37B. And China is flying one too.

http://www.ibtimes.co.uk/space-race-revealed-us-china-test-f...

That's a low-quality source in a hype-loop with a True Believer from Reddit, so take that 'word' with a bushel of salt.

It can be easily measured in the lab. When the effect keeps diminishing with better measurement, it's strongly suggestive of no effect. This paper seems to have some areas where the next round of tests could be obviously improved.

Time for me to break out the Tech Readiness Levels: this proposal is TRL 0 (1 if you're a True Believer). Observe the TRL required by NASA for a flying prototype. https://en.wikipedia.org/wiki/Technology_readiness_level

There's been breakthroughs in a fully quantified theory of how electromagnetics can be used to create propulsion reliably and at (still incredibly small but) orders of magnitude larger than prior designs provided by the aeronautics research team from the Northwestern Polytechnical University in Xi'an.

The research team published their breakthroughs in 2008, and excitingly, they've been highly reproducible.

Unfortunately, the paper appears to be behind a paywall: http://en.cnki.com.cn/Article_en/CJFDTOTAL-YHXB200805027.htm

Does anyone on HN have the background necessary to explain the mechanics of EM propulsion to laymen?

If they feed electricity into the microwave horn, how strong is the induced magnetic field around the wires? Would that push against anything? How is that compensated for in measurements?

Sad to see this nonsense pseudoscience constantly making HN's front page. Whenever it appears I debunk it using the same post[1] (in short, conservation of momentum cannot be violated) but it keeps coming back. Looks like even highly intelligent people like HNers are easily fooled by pseudoscience.

[1] http://www.preposterousuniverse.com/blog/2015/05/26/warp-dri...

> in short, conservation of momentum cannot be violated

Why?

Speaking somewhat loosely, the relationship between the local state of spacetime and its energy, the Lagrangian density, does not seem to depend on where you are or when you are. Emmy Noether gave us a straightforward proof that each such "differentiable symmetry" (in this case, translation invariance) implies that the state of spacetime maintains a corresponding "conserved current" (in this case, momentum and energy density).

The moment we get overconfident in our understanding of the universe is the moment that understanding stops advancing.

No law restrains nature but nature's own.

Do not tell nature what it can and cannot do.

(Evidence, of course, weighs very heavily against the EmDrive. But this sort of "it can't be doing that because that's against natural law" is just as unscientific.)

Thanks. I wish more people would help filter out the bad science (anything >= 1 nanoChopra).

Part of the world has entered the post-truth age, the spirit of the times likes a good story better than the facts, and if you speak facts you'll be damned by them.

Just look at the article itself, doesn't actually say anything about the paper beyond confirming it's going to be publicated, the rest is just retelling the story up to now like there's much debate going on.

As far as I know, there are some extremely questionable measurements showing there is something there, theory to explain it that is for sure completely wrong, and now this paper that might be alright that is not totally ruling it out. And based of this people go "why must momentum be conserved???!"; It ain't pretty, but that's the world we live in.

You do realize Newton's laws had to be amended less than 100 years ago to make room for the newly discovered subtleties of nature, right?

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