
NASA's Peer-Reviewed EM Drive Paper Has Finally Been Published - mastarubio
http://www.sciencealert.com/it-s-official-nasa-s-peer-reviewed-em-drive-paper-has-finally-been-published
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themeddler
This was published November 17, 2016. It's been officially published for
several months.

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Fjolsvith
[https://news.ycombinator.com/item?id=12995125](https://news.ycombinator.com/item?id=12995125)

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MPSimmons
November of 2016

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stevendhansen
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...](https://www.reddit.com/r/Physics/comments/5ewj86/so_nasas_em_drive_paper_is_officially_published/)

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DanielBMarkham
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)

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akvadrako
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.

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DanielBMarkham
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)

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colorint
>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.

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saagarjha
Paper listed in article,
[https://arc.aiaa.org/doi/10.2514/1.B36120](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...](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170000277.pdf)
online; I think it's the same thing.

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JohnJamesRambo
The first link loaded a PDF for me.

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saagarjha
Ahh, it looks like I didn't notice the PDF link. My mistake.

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Jedd
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.

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f4rker
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.

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throwanem
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.

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Jedd
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.

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aeleos
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.

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simonh
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.

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Sanddancer
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.

[1]
[https://en.wikipedia.org/wiki/Pioneer_anomaly](https://en.wikipedia.org/wiki/Pioneer_anomaly)

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simonh
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.

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consp
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.

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AndrewDP
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?

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SomeStupidPoint
Why would you test it in space?

I'm not sure I understand the reasoning.

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Malice
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.

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davesque
What ever happened with the German result that showed no thrust when the
device was hooked up to an on-board battery?

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dagw
here:
[http://emdrive.wiki/Experimental_Results](http://emdrive.wiki/Experimental_Results)
seems to be all the experimental results collected so far from various labs
around the world.

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goodcanadian
As always, the relevant XKCD: [https://xkcd.com/955/](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.

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Fjolsvith
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...](https://www.researchgate.net/publication/313580454_Low-
acceleration_dwarf_galaxies_as_tests_of_quantised_inertia)

~~~
fenollp
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"?

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Fjolsvith
It is unfortunate that the theory of Dark Matter doesn't have a cute parlor
trick like the EM Drive.

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buschtoens
Ugh, science alert. _sigh_

