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[10ebbor10]

Even, then, reputable research teams don't guarantee correct results.

https://xkcd.com/955/

[TempAcc]

Here's the abstract of the paper published by the Johnson Space Center team at Houston, on the Nasa Technical Reports Server, regarding the first test's results.

PDF version

EDIT: also, the paper regarding the emdrive invented by Guido Fetta, published on the Aerospace Research Central site

You need to log into the site to view the PDF version

[Zrk2]

That looks more promising. The abstract makes them sound thorough, but then so do most abstracts.

[Il Palazzo]

Here's what you should read instead:
http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-validate-imposible-space-drive-word/#.VUeVhfCuy1t

[misko27]

PTW. I don't claim to have the depth of knowledge necessary to accurately parse the truth from all the falsehood on this issue, but it is pleasant to see that this is still kicking. I was worried it had sunk beneath the waterline of news.

[Il Palazzo]

@Ispil:
Oh shoot, I've not seen it was already linked.

The point of the passage about the 'disabled' one is that they have a hypothesis of how it works, but it doesn't matter if the experimental setup matches the hypothesis or not - the result is the same.
That they say they observed some effect in the two setups where they plugged the microwave in is then not an indication of a validation of the hypothesis, which they suggest that it is! Quite to a contrary, it shows that whatever is causing the observed effect is not what the hypothesis states.

And I don't understand how you can defend a paper that is throwing around made-up technobabble words to 'explain' the observation.

[i2amroy]

Even, then, reputable research teams don't guarantee correct results.

https://xkcd.com/955/

I eriously doubt this can work. It's feels like too much pseudoscience to hope for it to work.

Another relevant xkcd:

Ha-Ha! Beat 'cha!

Whats weird is how nobody has actualy presented their own tests results that would refute its viability, considering the actual device is basically just a modified magnetron, something that can be found in ordinary microwave ovens. The measuring apparatus needed to detect the variations in the involved forces and phenomena is probably far more expensive then the actual emdrive device used in the tests. I mean, its not exactly something someone could do on their garage (at least not without a fair bit of money and knowledge), but any respectable physics and electronic research lab could do their own tests, maybe.

It's the second part that is the main limit on this. We're talking magnitudes of thrust so small that you basically need to test them in a near-total vacuum, as well as with very sensitive equipment, to be sure that they are working. (Ideally you'd test them in a gravity-less environment as well). These are magnitudes of thrust small enough that even an air leak in the test chamber could be causing them, and as such require equipment that is very expensive to test. Combine this with the fact that it still has a definite "pseudo-science" vibe to it that makes many large organizations not want to touch it in the event it really is junk, and you can see why there hasn't been much testing; the organizations that want to test it don't have access to the equipment, and the ones that have the equipment don't want to be the ones to test it and find out it doesn't work.

[wierd]

720mN is not that small actually.

From wikipedia:

1 Newton is the force needed to accelerate 1 kilogram of mass at the rate of 1 metre per second squared.

The 2500W version tested produced 720mN of thrust. This is much more than just a slight air leak could produce, this is enough to move .72kg 1 meter in 1 second.

The researcher does not know how much of this thrust could be attributable to a reaction-mass like interaction with the air that got into the chamber. That's why he does not consider it a true vacuum test.  it would have to be a rather large leak to get that kind of thrust measurement just from the air pressure outside shoving its way inside the test chamber, and pushing against the engine!

As for the "Oh noes! This is the next cold fusion! We dont want to test that and risk our careers!!" effect, I already addressed that when I TLDR'd the PM article. The author of the PM article points out that there is little to no rigorous testing, and so it should be treated as snakeoil.  I countered, saying it is not being tested because it is being treated as snake oil,. which when you combine the two, IS NOT SCIENCE, it's Hubris with a self-referrential axiom.

Again, if you want to refute the claims at this point, since there ARE experiments on the table that have been reproduced in different labs, not matter what the quality level is-- the CORRECT action is to recreate the experiment, making corrections to the process to eliminated outside variables.  NOT to navelgaze, pontificate, and try to bury it in rhetoric.

Experiment is the only real thing with weight that matters with this kind of claim. Either it is doing something, or it isnt.  If it is doing something, and we can't explain it, it means we cant explain it- not that it is not doing something.  The "But I might never get funding again! Mommy help me!" argument is just a consequence of bean counters getting their tendrils into science, and making it dance in very unscientific ways.

[Il Palazzo]

Experiment is the only real thing with weight that matters with this kind of claim.

I agree. However, and much like with cold fusion, despite the lack of experiments showing that there even is an effect that is not just poor preparation, the hype is being spun.
I'm sure nobody would advise to prohibit experiments. This still doesn't change the fact that until such experiments show conclusively a non-accountable for result, all of this is just a balloon of hot hype.

[Sergarr]

I'd wager a guess and say that "mN" in this case means micro-newtons, 10^-6 N, rather than 10^-3.

Otherwise they would have no problem measuring it.

[wierd]

That would be uN not mN.   (I dont unicode, "u" is supposed to be the greek letter mu.)

[i2amroy]

I'm sure nobody would advise to prohibit experiments. This still doesn't change the fact that until such experiments show conclusively a non-accountable for result, all of this is just a balloon of hot hype.

Indeed. Just because it's a self referential thing doesn't mean that it can't have real effects, because things like a reputation don't depend on logical consistency. It's totally possible for someplace to get a "if you go there you will die" aura about it even if nobody has ever gone there and died, regardless of the place's actual deadliness. While science might be always logical, scientists as people most definitely are not guaranteed to be, and thus things like funding, etc. don't always depend on logical consistency to be determined.

@Newtons:
The original Chinese test was indeed milliNewtons, however it's fault instead lies in its distinct lack of published or publicized material. On the other hand the tests that have been more widely publicized were scaled down drastically, the NASA test measured a net thrust of 116 µN, which is a very small amount, and thus could potentially be affected by other things.

[LordBucket]

So yes, they did a vacuum test, and yes the results were positive. But because of the leak the quality of the test wasn't sufficient for him to go out and say that yes they did a vacuum test.

The articles citing him neglected to mention that detail.

I'll see if I can track down the original statements.

Just stepping in to report that I have as of yet been unable to find the specific citation referred to above. But again, just based on my recollection of having read it, the NASA Eagleworks researcher (I think it was Paul March, his username on nasaspaceflight.com is Star-Drive) involved appeared to be stating that a vacuum test was performed, but that there was a leak in the chamber that invalidated the result.


What I'm not sure of is the date. There are plenty of articles stating that a successful vacuum test has been performed...but it's very common for journalists to not get all of the details right when reporting this kind of thing.

So at this time, I'm uncertain whether the test with equipment failure test is being misleadingly reported as a successful vacuum test, or whether the equipment failure test was one of the earlier tests that has since been re-performed correctly.

http://en.wikipedia.org/wiki/EmDrive#RF_resonant_tapered_cavity_thruster_.28EmDrive.29

"NASA's tests of this tapered RF resonant cavity were conducted at very low power (2% of Shawyer's 2002 experiment and 0.7% of the Chinese 2010 experiment), but a net mean thrust over five runs was measured at 91.2 µN at 17 W of input power. A net peak thrust was recorded at 116 µN at the same power level.[14]

The experiment was criticized for not having been conducted under vacuum, which would have eliminated thermal air currents. The researchers plan to replace vacuum-incompatible components.

Six months later, early 2015, Paul March from Eagleworks made new results public, claiming positive experimental force measurements with a torsional pendulum in a hard vacuum: about 50 µN with 50 W of input power at 5.0×10−6 torr, and new null-thrust tests.[37] The new RF power amplifiers were said to be made for hard vacuum, but still fail rapidly due to internal corona discharges, with not enough funding to replace or upgrade them, so measurements are still scarce and need improvement before a new report can be published.[38]

Glenn Research Center offered to replicate the experiment in a hard vacuum when Eagleworks manage to reach 100 µN of thrust, because the GRC thrust stand can only measure down to 50 µN.

In an article published on NASASpaceFlight.com in April 2015, José Rodal, Ph.D, Jeremiah Mullikin and Noel Munson report a successful vacuum test in which the drive created thrust."


I remember Paul March being the researcher who'd said the vacuum chamber failed. So if that "early 2015" test referred to on wikipedia is the failed test and the test being referred to in the April article is a different followup test with the error corrected, then we're golden. But it's plausible that it's simply a followup article based on the same test with the equipment failure detail having been missed by the guy writing the article. But it's also plausible that the first experiment that wikipedia explicitly states was "criticized for not being conducted in a vacuum" was the one with the equipment failure, and the 2015 test results were performed after the equipment had been replaced.


It would be helpful to have this uncertainty resolved. Anyone else want to help track this down?

[Mech#4]

Could I suggest contacting the journalists? They might have extra notes on the matter and may have omitted the detail for a more succinct article.

Or you could contact the scientist himself, if he has an email listed that is. He might be happy to help clarify details that have been misconstrued through reporting.

[forsaken1111]

"Excuse me sir, I represent a forum called Bay12 and we really want to know if this shit works so we can get excited."