
NASA confirms that the ‘impossible’ EmDrive thruster really works - fahimulhaq
http://www.digitaltrends.com/cool-tech/researchers-conduct-successful-new-tests-of-emdrive/
======
hannob
Remember the faster-than-light neutrinos? Where they repeated the experiment
multiple times with the same result? And nobody could find a plausible
explanation for an error? And then, some months later, they found it was just
a bad cable.

The sane rule of thumb on these kinds of experiments that seem to contradict
basic physics is to assume it's just an error in the experiment or the data
calculations. Even if they did it multiple times. If this gets replicated by
multiple independent teams worldwide with different experiments - then we can
talk about new physics. But it's important to understand how extremely
unlikely that is.

The best you can learn from these kind of stories is how hard it is to get
science right and how subtle errors can be.

Don't get me wrong: I'd love to see some star-trek-like science becoming real.
But it certainly doesn't help to replace critical thinking with wishful
thinking.

~~~
Symmetry
I'll agree that experimental error is the most likely explanation by far but I
think there's still a noticeable chance that the explanation is some novel
effect that doesn't actually violate conservation of momentum. If I were to
give a break down on my expectations they'd probably be something like

    
    
      90% Experimental error
      9%  Unexpected and novel consequence of current physics
      1%  New physics that doesn't actually violate momentum conservation
      ~0% Violation of conservation of momentum.
    

But this has gone the point where even if it's experimental error I expect the
mechanism will be at least somewhat interesting, as with the Italian speed of
light experiment.

~~~
yk
I think violation of conservation of momentum is more likely than new physics.
Basically, if this thing produces a general relativity effect, then it is
possible that momentum is not conserved because the underlying metric does not
have translation symmetry. (GR Energy Momentum conservation would still be in
effect in that case, but classical momentum conservation would not.)

Apart from that, I am unhappy about your percentages, I think the non
experimental error explanations are an order of magnitude less likely.

~~~
AnimalMuppet
> Basically, if this thing produces a general relativity effect, then it is
> possible that momentum is not conserved because the underlying metric does
> not have translation symmetry.

Given the setup, it seems _highly_ unlikely that this thing produces something
that requires a GR explanation. The energies aren't high enough; there's no
high gravitational field or high acceleration.

> I think violation of conservation of momentum is more likely than new
> physics.

But if GR is out, then violation of conservation of momentum _is_ new physics.

~~~
yk
I agree, or actually I assume that the disagreement is only about words. I
would not call it new physics, if, for example, we have to couple quantum
fields to GR in a not straightforward way, so in the case were we already know
all the parts but not the specific combination of the parts. I would only call
it new physics if we have to rewrite basic textbooks.

~~~
AnimalMuppet
If this showed us how to couple quantum fields to GR, that would be pretty
good. Personally, I would consider that "new physics", given how unclear it is
how to do so at the moment. If doing so doesn't significantly change either GR
or quantum, however (and so the basic texts are still valid), I could go with
your view.

------
dzdt
Headline is wrong. Correct topic sentence from article :

    
    
        "In essence, by utilizing an improved experimental procedure,
         the team managed to mitigate some of the errors from
         prior tests — yet still found signals of unexplained
         thrust."
    

No, the EmDrive does not work, they just haven't yet figured out yet why they
see the spurious acceleration in their measurements.

How do we know it doesn't work? Because it violates conservation of momentum,
without involving any of the extreme conditions where our current
understanding of physics might break down. Basic physics is REALLY REALLY well
tested. The chances that some new experimental configuration will expose new
physics, without involving extreme energy concentrations or extremely large or
tiny spatial dimensions, is so near to zero as to be negligible.

~~~
madaxe_again
Look, we KNOW that the sun revolves the earth and is affixed to a crystal
sphere, like the planets. It's clear from all observations that this is the
case. I mean, we understand epicycles perfectly, and they're due to the motion
of the spheres. The chance that some crackpot would expose new physics and
prove that the Earth orbits the Sun is so near to zero as to be negligible.

Your argument is the same as those made around relativity, as it disagreed
with Newton, and what could some fucking patent clerk possibly know that the
Greatest Scientist Ever didn't?

~~~
jschwartzi
The people discounting Kepler and Einstein had actually read their work. They
discounted it based on the lack of physical evidence(experimental results).
People in Einstein's time were still confused and trying to understand the
outcome of the Michaelson-Morley experiment. As for Kepler, he didn't provide
any new evidence either. The only advantage to changing the center of the
system was to eliminate the need to calculate epicycles when creating an
ephemeris.

I could certainly see how both theories would have attracted some disbelief in
their time. In Einstein's case, people started to accept SR when new
experimental results came that only made sense if the speed of light were
constant and the laws of physics were invariant in all inertial reference
frames.

Why do we have to accept that something novel is happening in this case? Can
you find any way to explain this effect with existing theory? More
importantly, what would have to be changed to accommodate this phenomenon? Is
it possible that the engineers are just measuring noise?

These are important questions that have to be answered.

------
threeseed
They didn't confirm anything. It was merely a rerun of tests with more of the
potential background causes mitigated. It is going to require a lot more tests
before someone like NASA unequivocally states that this works. Especially
given that this device relies on physics we don't yet know about.

Worth reading here:
[http://forum.nasaspaceflight.com/index.php?topic=38577.940](http://forum.nasaspaceflight.com/index.php?topic=38577.940)

~~~
Natanael_L
Not much unlike the recent string of Bell tests. Closing one loophole after
another until you can feel confident there's no other reasonable explanation
left except a single one, the proof or invalidation of the theory you're
trying to prove.

~~~
gus_massa
This is very different from the Bell inequalities.

The Bell inequalities is an easy to calculate result of quantum mechanic, the
whole calculation is less than 1 page long. (It's not easy to discover, but
once Bell discovered it, anyone can check the calculation.)

It follows the same rules of all the other QM experiments that have been
thoughtfully tested, so it's totally expected to be true. The problem is that
it's unintuitive, or to be more clear it's even more unintuitive that the
usual QM results.

The loopholes were very weird, like:

"The PRNG of my computer is conspiring with the PRNG generator of your
computer to get the results of the Bell inequality. They can conspire using
signals that travel at less than the light speed, so perhaps we have
conspiring hidden variables and not QM."

So to close the loophole someone has to use a real RNG instead of a PRNG, and
be sure that it random. And do the measurements in a short time so the crystal
in one site can't conspire with the crystal in the other site, and do the
experiments far away so the light doesn't have enough time to travel from one
sensor to the other sensor. The loopholes were totally paranoiac loopholes,
but to disprove the hidden variables theories you have to close all the
loopholes. (I think it's possible to imagine even more weird loopholes, so
expect a few linkbait announcement in the next year with the discovery of an
insane loophole in the last Bell experiment.)

The EM drive breaks the current accepted physics theories if the thrust/energy
ratio if greater than 1/c = 3.33 nano-Newtons per Watt.

Some of the loopholes are:

The electromagnetic force between the wires in the device (it's like an
electromagnet, without the iron core, so it's not as strong as a true
electromagnet)

The force due to thermal effects, like expansion or convection, because the
device get really hot when in use. Some of the experiments measure a delay
that is expected when you need some time to heat the device and some time to
cool the device after use.

The problem is that they still are closing the obvious loopholes, not the
weird ones.

The usual trick is to have a very strong force that is much more than the
expected effects of heating and electromagnetic interactions of the wires, but
they have measured only a very tiny force.

~~~
flubert
The "Chaotic Ball" model,local realism and the Bell test loopholes

[http://arxiv.org/abs/quant-ph/0210150](http://arxiv.org/abs/quant-ph/0210150)

------
zellyn
Why don't they just put one of these things in space, with solar panels, turn
it on, and see what happens? I guess the expense? It does seem the most
expedient way to verify whether it works or not.

~~~
swolchok
even SpaceX launches cost over 50 million dollars
([https://www.google.com/search?q=spacex+launch+cost](https://www.google.com/search?q=spacex+launch+cost)
has a big pullquote to that effect, for example)

------
ohitsdom
A lot of skepticism and negativity here, and I get that. But it's exciting to
watch science play out. This could be a huge discovery, or it could be crap. I
love seeing the methodology in making each test more and more definitive by
reducing variables and outside influences.

------
stargazer-3
I love that the question of this technology's validity is so grand it can be
approached with Fermi's Paradox. If such physics indeed exists, allowing
interstellar expansion of life, then it increases our chances of detecting a
signature of extraterrestrial life out there. Since we haven't detected
anything yet, it seems that EmDrive-tech is less likely to be real than if we
would have.

~~~
adrianN
This technology doesn't make interstellar travel much easier, even if it
works. You only save reaction mass, but you still need huge amounts of energy.
Our best bet currently are nuclear pulse engines [1]. Super advanced
civilizations might use Hawking radiation instead [2].

[1]
[https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...](https://en.wikipedia.org/wiki/Project_Orion_\(nuclear_propulsion\))

[2]
[https://en.wikipedia.org/wiki/Black_hole_starship](https://en.wikipedia.org/wiki/Black_hole_starship)

------
saintgimp
Seems like they need to do the hardware equivalent of a "git bisect" here.
Instead of fiddling around with the current version of the device, trying to
figure out if the observed effect is actually propulsion or just an artifact,
someone should start tearing the thing apart, testing as they go, and find out
at what point the observed effect goes away. That would probably be
instructive.

------
Pyxl101
Very interesting. I've been following this in the news for some time, hoping
to learn the results of the latest research.

In previous tests it seemed like the significance of the effect was
diminishing on each iteration, suggesting it might be experimental error.
Anyone have a handle on how the latest results have changed? I don't get a
good sense from the article.

~~~
threeseed
The purpose was to reduce the Lorentz force interactions:

1) Built and installed a 2nd generation, closed face magnetic damper that
reduced the stray magnetic fields in the vacuum chamber by at least an order
of magnitude and any Lorentz force interactions it could produce.

2) Changed up the torque pendulum's grounding wire scheme and single point
ground location to minimize ground loop current interactions with the
remaining stray magnetic fields and unbalanced dc currents from the RF
amplifier when its turned on. This reduced the Lorentz force interaction to
less than 2 micro-Newton (uN) for the dummy load test.

3) Rebuilt the copper frustum test article so that it is now fully integrated
with the RF VCO, PLL, 100W RF amp, dual directional coupler, 3-stub tuner and
connecting coax cables, then mounted this integrated test article at the
opposite end of the torque pendulum, as far away as possible from the 2nd
generation magnetic damper where only the required counterbalance weights now
reside.

Now since they were still seeing 100uN of force that means they have 98uN of
force unaccounted for. And the next iteration of the test is trying to
mitigate the effect of any thermal forces.

~~~
gambiting
At which point it would be actually cheaper to put this whole thing in space,
turn it on and see if it produces any trust? If it does, then it definitely
works. As long as it's on Earth, they will spend forever trying to account for
extra variables.

~~~
JohnBooty
Yeah. The general rule of thumb is that it costs $10,000/pound to put
something into orbit. The cost would increase by orders of magnitude once you
include all of the other resources needed to track the experiment, but this
does seem like a relatively cheap experiment to run in space.

[http://www.nasa.gov/centers/marshall/news/background/facts/a...](http://www.nasa.gov/centers/marshall/news/background/facts/astp.html_prt.htm)

I think what's preventing this is:

1.) NASA can only run a certain amount of experiments at once and I'm sure
there's a long waiting list. If they run this one, something else doesn't run.

2.) Space may not be the extra variable-free environment we're hoping for
here: tons of intense electromagnetic activity and so forth.

------
dandare
Can someone please explain to me how does one creates new technology without
having alt least one of the following? a) working prototype, b) consistent
theory why the new technology will work.

In other words, what made Roger Shawyer believe his engine will work if he
does not know how should it work nor have a prototype?

------
tdyen
So if an EmDrive worked, what would it give us? A star trek impulse drive type
thing? Or is it so low level an effect it would be useless?

~~~
colinramsay
The impulse engine in Star Trek was just a fancy fusion-powered plasma rocket.

[http://memory-alpha.wikia.com/wiki/Impulse_drive](http://memory-
alpha.wikia.com/wiki/Impulse_drive)

~~~
kuschku
Actually, there are several in-universe articles saying otherwise:

The interaction between the shields and a conventional propulsive system would
be horrible (you’d get fried in your own plasma).

Therefore the Interacting Magnetic Pulse system (sorry, I’m translating back
here, so I dunno if that’s the correct term in the correct in-universe article
in english) actually uses some weird interaction of microwaves to create
"gravitational waves on which the ship then rides", as one engineer said
poetically.

------
SFjulie1
Economical crisis are recognizable by the fact people tends to announce
"infinite energy source", "cheap energy", or "perpetual movement" finally made
true.

It is very interesting that while NASA that has been a clear "cache nez"
during cold war to mask the use of nazis scientists and technologies for the
USA they are now having a problem: space programs are considered to costly for
their return other investment. Especially when you know the budget of ESA for
rosetta/philae mission compared to NASA's budget.

Being on the grill, NASA is lobbying for even more costly mission to mars and
support their own propaganda (intestallar, alone on mars...).

And now, miracle, they have an opportunistic new technology that could help
achieve "cheap easy journey" to far away distance.

I can't help to be a little suspicious. The timing is so perfect.

And as numerous comments are spotting there is no new technology until we can
explain the causation. Because that is how science work: experiments should be
consistent with theory, and vice-versa. Else this is religion or philosophy.

Maybe emDriver could be the proof God exists, but it is not likely. Well, if
it existed, and since we would have a physical place where to search I would
kill it anyway. I hate Gods, I prefer to drive my own destiny without a
"père/mère fouettard(e)" looking upon my shoulder like a stalker.

------
jrjarrett
Woo hoo! The reactionless thruster! Next: Outsider hyperdrive!

[http://news.larryniven.net/concordance/main.asp?alpha=T#thru...](http://news.larryniven.net/concordance/main.asp?alpha=T#thruster)

------
alexandercrohde
I almost want to flag this link for playing loud sound advertisements on page
load, but I'm not sure that's proper in this community. Is there not a better
link to this content?

------
jcfrei
Previous discussion:
[https://news.ycombinator.com/item?id=10496638](https://news.ycombinator.com/item?id=10496638)

------
dredmorbius
I'd really like to see @dang et all at HN add digitaltrends.com to the
penalised-by-default domains on HN. This is simply irresponsible hackery.

Rick Stella as well.

------
snarfy
Momentum has velocity, but the velocity of light is the same in all reference
frames. It seems like there is a conflict between conservation of momentum and
special relativity. From the point of view of the light beam, nothing is
moving.

~~~
mercutio2
The speed of light in a vacuum is constant in all reference frames, but a
photon's frequency is _not_ constant in all reference frames, so it's momentum
(hf/c) is not constant.

This is bog-standard special relativity.

~~~
snarfy
Ah, this makes sense.

------
peter303
Cold fusion is the power source too.

------
transfire
Caution is called for. After all, blowing past warp 5 can damage the space-
time continuum.

------
selimthegrim
I can't name sources, but I have it in good confidence that this man ("Sonny"
White) was forced to rewrite his dissertation by his PhD committee (mind you
not his advisor, who was old and about to retire and had to be cajoled into
line by the rest of them) because his first try was apparently all about this
EMDrive stuff. This is a pathology.

~~~
selimthegrim
So, I'm being down voted for stating a relevant fact? I was asked not to
reveal this by my source.

~~~
mikeash
For stating irrelevant hearsay, perhaps.

~~~
selimthegrim
What, and if I break confidence and name names from the Rice faculty that
would somehow be better?

Being forced to rewrite entirely at a defense by the rest of one's committee
is a BFD, it absolutely impacts his credibility.

~~~
mikeash
Without knowing the details of what happened, we have no idea how it affects
this person's credibility.

 _You_ have no credibility, so your unverifiable story conveys zero
information. All it does is stir things up. Substantiating the story would be
good, and failing that, saying nothing would be better than essentially
spreading a rumor.

~~~
selimthegrim
I'm a physics grad student at a university not too far from Rice. How am I
supposed to substantiate this short of producing the first draft of his PhD
thesis? Do you think academia keeps these things around?

~~~
mikeash
It doesn't sound like you can substantiate it. But that has no influence on
your credibility, or on the believability or relevance of what you're saying.
From the outside, a true story that inherently can't be substantiated is
indistinguishable from a made-up story that can't be substantiated. And it
doesn't even have to be you who made it up, it could be the person you got it
from, or wherever _they_ got it, or all the way up the chain. Or maybe it's
true! I have no idea, which is why I called it "hearsay" instead of "lies."

