
The warp drive will have to wait - dmichulke
https://translate.google.com/translate?hl=en&ie=UTF8&prev=_t&sl=de&tl=en&u=http://www.golem.de/news/em-drive-der-warp-antrieb-muss-noch-warten-1606-121641.html
======
dmichulke
[https://translate.google.com/translate?hl=en&ie=UTF8&prev=_t...](https://translate.google.com/translate?hl=en&ie=UTF8&prev=_t&sl=de&tl=en&u=http://www.golem.de/news/em-
drive-der-warp-antrieb-muss-noch-warten-1606-121641.html)

The critical passages - translated by myself

Page 2:

The hint:

"Again it showed the same behavior - until the drive was directed towards the
top for testing purposes. Usually, the drive is put on a torsion balance in a
way that it can best turn the scale left or right. With the drive directed
towards the top nothing should be measurable. [...] However, the drive
directed toward the top in this experiment still showed the same force as when
directed to the left."

The test result at TU Dresden, Germany: "Tjalmar said: 'I can't say I proved
or refuted the EM drive'" (because they didn't have the means to test it with
a battery instead of an external power supply)

Reference to a follow-up from a Chinese university: "But a research group from
China did the necessary to refute it. As soon as the EM drive doesn't get its
power from a cable outside [i.e., it get's its power from a battery], there is
no measurable force anymore."

The link to the Chinese paper
[http://www.tjjs.casic.cn/ch/reader/create_pdf.aspx?file_no=2...](http://www.tjjs.casic.cn/ch/reader/create_pdf.aspx?file_no=20160220&flag=1&journal_id=tjjs&year_id=2016)

The final sentence of the abstract: "Within the measuring range of three-wire
torsion pendulum thrust measurement system，the independent microwave thruster
propulsion device did not detect significant thrust. Measurement results
fluctuate within ± 0.7mN range under the conditions 230W microwave power
output，and the relative uncertainty is greater than 80%"

~~~
aargh_aargh
So... you're saying all we need to do is pull an extension cord behind our
spacecraft?

Unlimited powahhh!

~~~
jerf
That's basically the thinking behind the laser-propulsion plan. The rocket
equation gets a lot less hostile when the engine is not mounted on the rocket,
but that has its own practical issues. Less than trying to drag a literal
cord, of course.

~~~
neutronicus
Just building a kilometer-wide lens to keep it focused and a several-Terawatt
power source.

Space travel. Shit's hard.

------
Tomte
I think the best sentence is this:

"The theoretical expectation is that you don't measure anything. Now you're
measuring something, and you can learn extremely much on this hunt for the
error."

~~~
ucaetano
Sounds a bit like Fermi's quote:

"If the result confirms the hypothesis, then you've made a measurement. If the
result is contrary to the hypothesis, then you've made a discovery."

~~~
api
I remember that quote too, and the key take aways always seemed like: in
science you _always learn something_.

Taking the EMDrive as an example -- we have measurements that contradict
current theory, so we are either going to discover new physics or we are going
to learn something about the art of making very precise measurements of force
in complex mechanical systems. In no case do we learn nothing.

~~~
aminorex
A third option, of equal merit: We may learn to apply existing theory more
correctly and more adequately in a novel configuration.

------
Libermentix
In case you are curious about some data. There is a German maker who has been
posting about his experiments as well.

[https://hackaday.io/project/10166-flying-an-
emdrive](https://hackaday.io/project/10166-flying-an-emdrive)

~~~
HCIdivision17
Holy mackeral, that is cool. I really appreciate the "well, let's just try it"
approach. I can't wait to see what happens when he launches his little
satellite. If it shows positive results, lots of people will replicate it.

This is win-win: if it works awesome happens. If it fails then you're left
with the experience of having built a little satellite!

~~~
api
> I really appreciate the "well, let's just try it" approach.

That's called "science." :)

------
leecarraher
Why not run the setup without the cavity, or replace the magnetron with a big
ass resistor, and see if you still get deflection. I suspect this is the
beginning of a refutation, but it feels like there's a carrot still dangling.

~~~
James001
Yeah, this is hardly a refutation. This is just one failed attempt at
replication using batteries

------
bleuarff
I guess a cheap and efficient propulsion that doesn't fit our understanding of
physics was too good to be true. Still, it's a bit sad, that would have been
beautiful if it were true.

~~~
bayesian_horse
As far as I understand it, it's not quite over yet. Maybe the refusal itself
can't be replicated by the other groups. Now that will keep these physicists
busy for a while...

~~~
Obi_Juan_Kenobi
It's not really over until we understand where these readings are coming from,
whether error or new physics.

------
arijun
I believed in the EM drive in the same way I occasionally buy lottery tickets:
there's no way I could win, but wouldn't it be _so cool_ if I did?

~~~
raverbashing
Well, the probability is non-zero. And people win.

Sure, it is _extremely small_. But even that is different from zero.

~~~
aminorex
Reward is finite. Risk is infinitesimal. No-brainer.

------
FreeFull
I wonder what was causing the measurement, then. Magnetic repulsion due to the
current flowing through the cable?

~~~
peterbonney
Yes, that is what is suggested by one of the experimenters at the end of the
article.

------
sctb
We updated the link to the translated version of the article. If someone can
suggest a good English article, we can update it again.

------
Odenwaelder
If something sounds too good to be true, it usually isn't true.

~~~
seanosaur
Or, it's a scientific breakthrough. That won't happen often, but it also can't
be ruled out completely.

~~~
Certhas
If it's free energy or free momentum, using only physics that has been
perfectly described in hundreds of millions of contexts and experiments, for
one and a half centuries, using mathematics that don't allow for either, you
can rule out this alternative.

The likelihood that free momentum and free energy are possible is
indistinguishable from 0. They are empirically impossible in the strongest
reasonable sense the word can have.

~~~
HCIdivision17
The critical detail here is that this is neither free energy nor free momentum
in this setup. Energy is pumped in, and some momentum is generated - that's
incredibly boring and not at all something that should raise any skepticism.
The question of what in the hell was being pushed against to convert that
energy to momentum, on the other hand, is a really interesting question, but
not one to deeply pursue until we're actually sure it's happening. Which seems
like the cavity wasn't the interesting bit in the end. A shame and a bit
boring after so much careful testing, but nothing to get worked up over.

And the experiments didn't make it obvious that the setup didn't work. I mean,
I don't think anyone took the inventor's theoretical claims seriously, but the
device did generate some small thrust in a difficult to explain way.

Besides, we know that space isn't _nothing_ , so being able to tractor against
whatever is there would be a rather intersting engineering find; physicists
would then likely take the experiment and go "oh, there's a neat edge case in
this system of equations that explains it". There are a _lot_ of interesting
edge cases left to find and engineer.

~~~
Certhas
Free momentum WAS claimed. Hence the space engine applications talked about
everywhere.

Momentum is conserved independently, it can not be created from energy without
spilling some the other way (into whatever you're pushing against).

The vacuum is a translation invariant state so you can't push against it to
get momentum either, but you can create particles out of it and then push
against those. That's what electro magnetic thrusters do. They generate
photons. The effect is just super tiny.

------
SubiculumCode
I dont see any other article on the internets discussing these results

~~~
welterde
Judging from the date in the URL of the linked paper [1] and the corresponding
section in the Wikipedia article on the EMdrive suggests that you might have
better luck looking at somewhat older news articles. Publication date (and PDF
metadata) seems to be 2015 though [2].

[1] [https://tu-
dresden.de/die_tu_dresden/fakultaeten/fakultaet_m...](https://tu-
dresden.de/die_tu_dresden/fakultaeten/fakultaet_maschinenwesen/ilr/rfs/forschung/folder.2007-08-21.5231434330/ag_raumfahrtantriebe/JPC%20-%20Direct%20Thrust%20Measurements%20of%20an%20EM%20Drive%20and%20Evaluation%20of%20Possible%20Side-
Effects.pdf)

[2]
[http://arc.aiaa.org/doi/10.2514/6.2015-4083](http://arc.aiaa.org/doi/10.2514/6.2015-4083)

------
IgorPartola
So was it a hoax or a mistake by its inventors?

~~~
HCIdivision17
That's sort of an unnecessary dichotomy. Enthusiasm doesn't mean hoax, and the
mistake was propagated by more than just the inventors.

Everything suggests that it was just science in action. There was an
experiment, and it failed to reject the null hypothesis of 'no thrust'. A few
groups have repeated the experiment, but not to the experimental power needed
to thoroughly reject it. This test seems to be a more definitive rejection of
it, but we're still not sure why there was any thrust measured in the first
place, though there are some pretty reasonable leads on that.

~~~
IgorPartola
I can see that to a point, but there was a commercial venture set up around it
too.

~~~
api
Setting up commercial ventures based on speculative hypotheses is what a large
chunk of Hacker News does for a living.

------
cousin_it
Come on folks. John Baez has dismissed it [1]. For those who don't know who
John Baez is, it's as if Terry Tao dismissed your math homework. For those who
don't know who Terry Tao is... whatever. Just stop.

[1]
[https://plus.google.com/app/basic/stream/z13gzfm4xt2tuxehl04...](https://plus.google.com/app/basic/stream/z13gzfm4xt2tuxehl04chvywcofjhhzhwbk)

~~~
danharaj
John Baez and Terence Tao are as nice as they are smart and i think you're
doing them a disservice by using them to be condescending.

~~~
cousin_it
Have you read Baez's post that I linked? It's way more harsh than my comment.
"Mumbo jumbo", "Failed a course in quantum field theory and then smoked too
much weed"...

Also I'm getting seriously creeped out by the amount of EmDrive non-skeptics
on HN. Maybe we should make a poll whether 0.999... = 1, and then say that
anyone who insists on the correct answer is "condescending".

~~~
vardump
Ad hominems and appeals to authority are such letdowns.

Almost as those who might even admit they know nothing about it, but feel
they're qualified to judge validity of some scientific claim. And provide
<insert subculture> mantra as "evidence".

~~~
cousin_it
I do know quite a bit about physics. But if I just said the EmDrive is
nonsense due to conservation of momentum (which is the 100% correct answer
with no caveats), people would shut me down because "NASA scientists know what
they're doing". That would be an appeal to authority. So I mention Baez
preemptively, but it seems like that's not a winning tactic either. What would
convince you, pray tell?

~~~
vardump
> you'd shut me down because "NASA scientists know what they're doing"

I've said nothing like that.

A working experiment that provides irrefutable data is needed to convince me
in any way. Refutation I'd need to leave for others to do, not my competence.

I really like EmDrive as an idea and hope it will work out. It's very
inspiring when someone has the guts to push it despite the dominant
(scientific) opinion. If it does work out, these people will be some of our
greatest heroes.

After all, sometimes people like these have been right in the past in adverse
scientific atmosphere. I'm just content to follow it from the sidelines.

If I had to bet on EmDrive, I'd have to bet against it.

~~~
cousin_it
I understand your position.

The real question is how much you should weigh a single experiment vs. the
abstract idea of conservation of momentum. It's tempting to trust the
experiment all the way, and imagine that science demands such open-mindedness.
But the more physics you study, the more likely you are to trust the abstract
idea instead, because you realize just how incredibly well-supported it is.
It's a kind of certainty that has almost no analogue in other sciences. Even
in a very careful experiment, measurement error is many times more likely than
overturning conservation of momentum. (Also measurement error is much more
devious than people imagine, but that's another story.)

I'm very confident ($100 to $1 at least) that the EmDrive is a story of
measurement error, compounded by ignorance and optimism.

~~~
marcosdumay
By one experiment, you mean one actual experiment, made once, by a single
group? Or one single experimental setup, replicated by different groups?

If it's the former, I don't trust it at all, but if it's well practiced and
interesting, it ought to be replicated. If it's the second, well, if its
results are against theoretical models, theory is wrong. No questions, no
exceptions. Now, theory correction does not automatically mean a fundamental
change, "hey, this approximation we used has a problem here" is as valid a
theoretical correction as "ops, all of our models are wrong, everything is
much more complex than we thought".

Specifically about the EmDrive, I'm not aware of anybody that could actually
measure an effect yet. So, there's no experiment showing theory is wrong.
There's only a lack of experiments confirming it either (or better, now there
is one).

------
aminorex
EM drive is not an argument such that it might be refuted. It is a device. As
such it has fitness for purpose, which depends entirely on the purpose at
hand.

Snarkiness << skepticism.

~~~
zackbloom
Sure, if you need a paperweight, it very well may be the device for you. But
the question is it's fitness as a propulsion device.

~~~
LoSboccacc
or discharge a battery very fast

