
Uncertain Propulsion Breakthroughs? - blater
http://www.centauri-dreams.org/?p=36830
======
xupybd
Wow, I've not read something like that in a long time. More news needs to be
like this. Examining what we know presenting where we are. Not taking sides
and polarizing the discussion.

I do think people miss one small aspect of this story. How long has it been
since we've had a device built that we've no understanding of the principles
of it's operation? I think that's an amazing fluke and (if the effect is
genuine) something worth celebrating (just because it's so rare).

~~~
alasdair_
Quite a few medicines (especially antidepressants) state something like "we
don't really know why this stuff works, only that it does."

~~~
pmezard
From Wikipedia Paracetamol article
([https://en.wikipedia.org/wiki/Paracetamol#Mechanism_of_actio...](https://en.wikipedia.org/wiki/Paracetamol#Mechanism_of_action)):

"To date, the mechanism of action of paracetamol is not completely
understood."

and:

"It is the most commonly used medication for pain and fever in both the United
States and Europe."

"Not completely understood" is not the same as "we have no idea why it works",
but still I find it telling for such a popular product.

~~~
tunap
9 years ago I heard a NPR interview with the scientist(s) who cracked the code
on exactly _how_ chlorine bleach kills bacteria. Something _I assumed_ was
known longer than I've been around using bleach to disinfect.

edit: link

[http://www.npr.org/templates/story/story.php?storyId=9700789...](http://www.npr.org/templates/story/story.php?storyId=97007890)

------
anotheryou
I hope we'll find out in practice:
[http://www.popularmechanics.com/science/energy/a22678/em-
dri...](http://www.popularmechanics.com/science/energy/a22678/em-drive-cannae-
cubesat-reactionless/) (via lobster_johnson)

"Proud to say that we have a partnership now - so the launch is already
funded, and we hope to get a launch slot in 2017."

~~~
cperciva
Being in space doesn't solve the problem of errant forces completely. You can
push against the earth's magnetic field, for example.

~~~
JumpCrisscross
Satellite orbits degrade overtime due to drag, among other things [1].
Operators counter this decay with periodic boosts. (The International Space
Station is boosted, on average, once a month [2].) Boosting, even electric
propulsion boosting, consumes propellant.

If this works by impelling against the Earth's magnetic field, provided it is
more efficient than a simple magnet, it could still have a market with
satellite manufacturers.

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

[2] [http://space.stackexchange.com/questions/9087/how-often-
does...](http://space.stackexchange.com/questions/9087/how-often-does-iss-
require-re-boosting-to-higher-orbit#9088)

~~~
dom0
> If this works by impelling against the Earth's magnetic field

That's a completely different premise than the em-drive has, though. It's
supposed to not depend on an external field; developing a force between two
magnets wouldn't exactly qualify as (non-)rocket science today.

~~~
cjensen
The "premise" for the em-drive has been determined to be a thorough
misunderstanding of the physics involved, so you cannot rule out any
potentially contributing force in the experiment.

Yes you heard that right: guys who misunderstand physics go and design a
reactionless thruster which, when measured in their shoddy experimental setup,
produces a measurable thrust.

If there really is a measurable thrust, then the Laws of Motion are wrong and
General Relativity is wrong. I'm disinclined to believe that long-held
principles of physics will be upended by some guys who designed something
based on a misunderstanding.

~~~
freehunter
You sound very negative towards conducting more experiments on this, when the
results have been unexpected every time it's been tested. You're displaying
the kind of dogma that science has been fighting against since the dawn of
time. Either it's true or it's not, but we can't tell until we test it. And so
far, it's only been disproven in theory, not in practice. That's worth more
experiments.

~~~
cjensen
Occam's Razor says it is not true. If you read the linked article, it is
saying, in the most polite and disinterested way possible, that it is not true
although they allow, in the driest of terms, that it could be true. I expect
if the same authors analyzed the Loch Ness monster or Big Foot, they would
also disinterestedly point out the unlikelihood of either and point out the
how awful the proofs put forth are while admitting there is no categoric proof
that the monsters don't exist.

Pons and Fleischmann were straightforward in their error. This is bozo
territory.

~~~
bicubic
I don't expect the em-drive to work, but the parent post has a point. We've
had repeated experiments yielding unexpected results. It's worth an inquiry;
if nothing else, to thoroughly explain what went wrong so the same mistake is
avoided in future experiments.

Outright dismissing new ideas, no matter how far-fetched, is very much the
antithesis of the scientific principle. You mustn't forget that everything we
take as indisputable fact today, was an outrageous far-fetched theory at some
stage.

It was barely yesterday that Barry Marshall was ridiculed for proposing that
stomach ulcers are bacterial, because everyone 'knew' that bacteria can't
survive in such an environment.

~~~
mhneu
Many possibilities of what went wrong are well-explained in the parent
article, drawing on experience of other scientists that make low-force
measurements. (E.g. forces on rig due to electrical current flow, or liquid
flow.)

Unfortunately it seems likely we won't learn much by finding the possible
sources of error - the sources are already well understood by people doing low
force experiments.

~~~
freehunter
Wouldn't it be worth repeating the experiment controlling for different
factors at the very least to rule out some of the "many possibilities"? If
there are "many possibilities" for why something is happening, by definition
we don't know why it's happening. Science says repeat the experiment until we
know why it's happening, or at least until we can't rule anything else out.

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perlgeek
That was quite a thoughtful, and IMHO balanced, discussion. I wish this was
the usual level of discourse on scientific news.

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xt00
If they have two versions of the resonant cavity, one that is tapered and one
that is just a simple cylinder that to me would be a big step in the right
direction to address many of the concerns. Basically the cylinder with no
taper should show zero thrust. And the version with the taper should show a
thrust. Then if they test that setup inside the huge Apollo program vacuum
chamber far away from the side walls and change the orientation of the coolant
and power wires into different orthogonal directions that sounds promising..

~~~
mrfusion
We don't know if the taper does anything though. If we don't have a working
theory we can't really use variations of the working device to prove anything.

~~~
xt00
Oh I had thought that the asymmetric shape with the tapered cone shape was an
important feature from the original inventor. But yea, hard to guess without
more systematic theory to leverage off of yea..

------
Trombone12
The Summary: "this most recent report is a significant improvement, but has
many shortcomings. Questionable subjective techniques are used to infer the
“thrust” from the data. Other likely influences are not quantified. But also,
despite those inadequacies, the possibility of a new force-producing effect
cannot be irrefutably ruled out. This is intriguing, but still falling short
of defensible evidence."

------
empath75
tl;dr;

> First, I cannot stress enough that there is no new EmDrive “effect” yet
> about which to theorize. The physical evidence on the EmDrive is neither
> defensible nor does it include enough operating parameters to characterize a
> new effect. The data is not even reliable enough to deduce the force-per-
> power relationship, let alone any other important correlations.

~~~
Others
I don't think that's a fair summary... The author provides a more nuanced view
than just "there is no effect." You're nitpicking from one section about
theory, without considering the article as a whole. This is especially
egregious considering that the article spends so much time talking about
confirmation bias.

~~~
jdoliner
It even says explicitly:

> Do you want to know our conclusions without any regard to how we reached
> those conclusions? ... If you answered “yes” to any of those questions, then
> you, like me, have natural human cognitive dysfunctions.

~~~
StavrosK
I don't understand that. Since I can't educate myself on everything required
to make an informed decision on whether the paper is true or not, I decide to
just trust someone else's opinion. I pick people to trust based on various
criteria (how well they've cited their sources, how much other trustworthy
people trust them, etc) and then just blindly believe whatever they say.

What else can I do?

~~~
mquander
> how well they've cited their sources, how much other trustworthy people
> trust them, etc

That sounds to me like a "regard to how they reached those conclusions" (maybe
a regard to how they reached a subset of their conclusions, and extrapolating
to the rest). It's not the most regard you could possibly have, but it's lots.

------
Animats
It's so near the noise threshold. Most of the energy goes into heating the
thing; only a tiny fraction comes out as possible thrust. The heating prevents
using enough power to get more possible thrust; the thing would burn out.

Very frustrating.

~~~
halomru
If we had any idea how they work (if they work) we could work on optimised
designs that generate more thrust and are thus easier to study. But we're not
yet anywhere near the stage and instead have to study a design that if it
works, is so inefficient that we can hardly tell whether it does anything.
Very frustrating indeed

~~~
Animats
Yet it's happened before in engineering history. Edison discovered the "Edison
effect" \- he put an extra plate in an incandescent lamp, and discovered that
some current, not much, would flow to it through vacuum. This, in 1875, was
the beginning of the vacuum tube. But lacking the theory to understand it, it
couldn't be improved. Early on, it was thought that there had to be some air,
or something, in the tube for it to work. But then it was discovered that hard
vacuum worked better. This confused electrical inventors of the era - how
could electricity conduct through a vacuum? It wasn't until 1904 that tubes
started to be figured out.

Tube filaments are quite different than lamp filaments - tubes need a material
where electrons are easily emitted from the surface. Tungsten is good for
lamps but terrible for tubes. A little thorium oxide or barium oxide helps a
lot. But there was no theory to indicate in what direction to go, and it took
30 years before trial and error produced results.

------
thearn4
I know Marc Millis, let me know if anyone has any questions and I can try to
get his feedback here.

~~~
Analemma_
He did so partially in this article, but I would love to see a detailed
explanation of a _valid_ experimental setup to test the EmDrive effect. What
would an experiment look like where, if thrust were observed, then we could
really start to say there might be something here?

~~~
extrapickles
There is a list of improvements in the article under "Latest Paper".

Its mainly the need to carefully characterize and document all the test
equipment and EM Drive support equipment to make sure its not caused by the
test setup. This would involve testing with a dummy load so things like
interactions with chamber wall can be ruled out or if there are, the effect
can be mitigated or accounted for.

Basically they proved their test setup produces thrust, but haven't proven the
thrust was a direct result of the EM Drive. They need to more rigor to prove
its only the EM Drive and not a setup error (eg: something like the FTL
neutrinos turning out to be a poorly tightened connector).

------
Nomentatus
Remember that "tacking"* in sailboats (going upwind, using only the force of
that wind) was held to be impossible, a violation of the laws of nature until
people actually witnessed it, too. Severe violations of our expectations don't
always break the actual math of a physics model.

*more properly said "beating to windward" [https://en.wikipedia.org/wiki/Tacking_(sailing)](https://en.wikipedia.org/wiki/Tacking_\(sailing\))

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powera
IMO the "rational" approach is to treat the claims as a bunch of pointless
lies until there's a repeatable demonstration. Remarkable claims demand at
least some evidence before wild speculation commences. As it is, Harry Potter
is just as credible a theory of reality.

After all, they've made the same claim repeatedly for 15 years after their
first experiments were demonstrably not what they claimed.

~~~
stale2002
This is what they are doing. They are sending something into space to
demonstrate the effect.

Let the experiments decide what is right or wrong.

~~~
samplonius
So "space" is some magical place where measurement error does not exist?

Low earth orbit isn't perfect either. You still have micro gravity. And the
experiment requires a lot of power, and very sensitive instruments to measure
the phenomenon. How do you get sensitive instruments which are expected to be
operating near their error threshold into orbit without damaging them?

Orbital experiments will have to be smaller, and use less power, so the
effects will even be smaller. But the instruments will have to be tough enough
to withstand 5G. And the apparatus could still be introducing other errors,
like coolant momentum, which also isn't magically eliminated by being in
space.

~~~
stale2002
The experiment is pretty simple.

You put the engine in space, with solar panels, and you see if it stays there
or falls back to earth.

There is no experimental error, or even measurement devices.

It is a space engine. Either it flys or it doesn't.

Over the course of a year, it will be obvious if it works or not. Because if
it doesn't work it will fall to earth.

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trhway
we have several unexplained things which possibly look like some interaction
between gravity and EM - em-drive, spinning magnet/superconductor gravimetric
effects and unexpected velocity of stars in the galaxies (which are big
rotating piles of plasma)

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pizza
Anybody know anything about the quantized Unruh radiation -> inertia theory?

~~~
naasking
Perhaps this:
[https://arxiv.org/abs/1302.2775](https://arxiv.org/abs/1302.2775)

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jayajay
"Inertial frames are the reference frames upon which the laws of motion and
the conservation laws are defined, yet it is still unknown what causes
inertial frames to exist or if they have any deeper properties that might
prove useful."

"...we must begin a more in-depth experimental program using qualified and
impartial labs, plus qualified and impartial analysts."

Maybe humans don't really belong in labs in the same way that they don't
belong in factories.

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disposablezero
Busted by Thunderf00t

[https://youtu.be/jCAqDA8IfR4](https://youtu.be/jCAqDA8IfR4)

It's amazing people are still giving this bollocks the time of day.

