
Questions about Nasa's space drive answered - ColinWright
http://www.wired.co.uk/news/archive/2014-08/07/10-qs-about-nasa-impossible-drive
======
michael_nielsen
Every few weeks on Hacker News we have the following cycle:

(1) News article! Prevailing view of physics overturned! Etc! Etc! Etc!

(2) Many excited comments!

(3) Much less excited comment, pointing to skeptical remarks by well-known
professional physicists (e.g., John Baez, Sean Carroll).

(4) Much to-and-fro. People who once saw a Discovery Channel special on
physics now appear to believe that they're in a better position to evaluate
the new claims than the people from (3).

Now, points (1) and (2) do sometimes happen, without points (3) and (4).

For instance, the neutrino faster-than-light claims attracted very cautious
comment from professionals. In other words, point (3) was absent or rather
muted. That's because the people who'd done the experiments were known for
being extremely careful, and were, in fact, very cautious in their
announcement.

That kind of thing is genuinely exciting, and worth discussion.

Another nice example of an exception is the Alcubierre drive. It satisfied (1)
and (2) (or the 1996 equivalent), but (3) was absent, except that
professionals noted that the drive required the stress-energy tensor to have
some unusual properties, not satisfied by any known substance. Indeed,
Alcubierre pointed this out himself.

Again, genuinely exciting, and worth discussion.

But when the professionals are loudly deriding a result, it'd be nice for the
amateurs to make a serious attempt to understand why, and not just airily
dismiss it.

------
FiatLuxDave
I've read the abstract, but apparently Wired has access to more information.
Any idea where the primary source for that information is?

I'm interested to see what magnetic shielding was used and how well they
characterized the magnetic field in the experimental volume. There was a
mention of shielding against electromagnetic effects, but that could just mean
a Faraday cage or Helmholtz coils, neither of which will reduce the B-field to
zero.

Because the device is based upon microwaves in a conducting cavity, I would
think that the first place to look for a theory of operation would be E&M, not
quantum. The level of force involved is the kind that you can see when
interacting with the Earth's magnetic field. Normally we ignore the force
produced by the interaction of currents with the Earth's field, because they
are so small. Was a mu-metal shield used, and if so, what was the remnant
field? Was a stronger field induced to see if that increased the force? I hope
that the experimenters try this if they have not already.

~~~
danbruc
[http://www.libertariannews.org/wp-
content/uploads/2014/07/An...](http://www.libertariannews.org/wp-
content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-
BradyEtAl.pdf)

~~~
FiatLuxDave
Thank you! It's always best to read the actual paper.

I note that not only is there no shielding to reduce the Earth's magnetic
field, but there are large NeFeB magnets in the torsion balance assembly. I
strongly suspect that the "missing momentum" is going into the object
producing the magnetostatic fields which lie in the RF cavity, whether that be
the Earth or the damping magnets.

Not to say that this wouldn't be interesting (RF interaction with
magnetostatic fields), but I don't think this has met the level of proof
required of a claim of violation of momentum conservation.

~~~
XorNot
Or the more obvious conclusion, which is Wired don't know how to read a paper,
and nowhere in the actual experimental section do they say they pumped down
the apparatus when they were actually testing.

------
didgeoridoo
Deep breaths. Probably experimental error. Extraordinary claims require
extraordinary proof...

God DAMN this is exciting.

~~~
madaxe_again
Indeed.

As to the whole "we don't actually understand how it works" \- we still can't
make up our minds as to how _wings_ work, so this isn't overly novel. Sure, we
can _explain_ the outcome, but whether it's Navier-Stokes or Bernoulli or
something else, we can't make up our minds.

I suspect this will be similar for a long while - although _puts physics hat
on_ I think this is likely a relativistic temporal quantisation effect.

~~~
ColinWright

      > ... we still can't make up our
      > minds as to how wings work, ...
    

Interestingly, I recently spoke to an aerodynamicist and mentioned this, and I
was severely lectured. In the follow-up he mellowed a little, but I suspect
the "we" in your statement refers to laypersons who don't have advanced
training in aeronautics, and yet claim to understand about flow pressure,
Bernoulli, _etc._

I've been convinced that the people who genuinely work with these things and
study them properly, actually _do_ know how wings work. You may not, I may
not, the mythical "man on the street" may not, but there are people who
really, really do.

~~~
madaxe_again
No, I've a masters degree in Physics, and did several research projects on
turbulent/laminar flow. We have a detailed understanding of a variety of
theories which correctly represent the lift effect experienced on a body
moving through a flow, yet none of them do it perfectly or completely. We can
_implement_ the technology well, but not without the aid of wind-tunnels and
brute-force computer simulations in order to validate our designs - had we a
perfect mathematical understanding of lift - we would not need to.

Another example from Physics - quantum mechanics. We can describe the
properties of a QM system, its outcomes based on inputs, the probabilities of
states - yet we have not got the blindingest clue as to _how_ it works. We
have theories, but again, none are perfect - for instance see the Pilot Wave
formulation of QM, which implies a deterministic universe, and isn't wrong,
but isn't generally accepted - even though it describes QM systems well, for
what little of it has been formulated in the last century.

~~~
lmm
It doesn't imply a deterministic universe any more than vanilla many-worlds.
Sure, the pilot wave is deterministic. But when you actually measure the
position of the particle? You get one of many possible results, with
probability determined by the pilot wave. Big whoop.

We understand QM perfectly well in the only meaningful sense - we can predict
the results of any experiment. There's plenty of arguing about "what it means"
or "what's really happening", but that's not really physics in my book.

~~~
FD3SA
Exactly. I am constantly astounded by professional scientists who try to find
a deeper meaning in mathematical models whose only purpose is to predict
experimental results. Human brains work on intuition, but when dealing with
imperfect models such as Quantum Mechanicns (QM), there is no intuition to be
had. If Quantum Mechanics or General Relativity were perfect, we wouldn't
actively be looking for a unifying theory to resolve their mutual
inconsistencies.

Once we have a theory of everything, then we can begin trying to form an
accurate intuition underlying the model. Until then, there is no point trying
to intuit probabilistic models which are designed to predict experimental
results, and nothing else.

------
tobinfricke
Here are two nice posts by physicist John Baez with some reasons to be
skeptical about the "reactionless drive":

[https://plus.google.com/117663015413546257905/posts/WfFtJ8bY...](https://plus.google.com/117663015413546257905/posts/WfFtJ8bYVya)

[https://plus.google.com/117663015413546257905/posts/C7vx2G85...](https://plus.google.com/117663015413546257905/posts/C7vx2G85kr4)

~~~
mnl
I'd never understand how intelligent and educated people lose it completely
when it comes to Physics. They've been exposed to some PopSci tales not meant
to be accurate at all and then feel entitled to be right when they figure out
some nonsensical consequences by themselves -no proper maths involved ever-.
It's depressing.

Baez is right, of course. I've been checking the (Word-generated) "papers"
from this guy's group at NASA, they're extremely shoddy: There's another
report with their unstable calibration for the torsion pendulum which shows
their complete lack of undergraduate lab report skills. And a poster from them
where they say: "Q-thruster test articles are going to be tested in a vacuum
to reduce possibility of air currents polluting the thrust signal during
testing, but electrolytic capacitors in signal amplifier are not vacuum
compatible"... Awesome.

I've also checked the Chinese Physics B paper. Their device is completely
different from this one. It's an open cavity and they only use classical EM. I
don't understand very well how their thrust measurement set-up works so I hold
my judgement on their claims, but at least they're trying to be legit.

Violation of momentum is an extremely serious claim (in words of D.J.
Griffiths, "there is no principle in Physics more sacred than that"). The
Universe would look nothing like this if that were true and all the Physics
that we've discovered consistent with thousands of experiments would be gone.
The way they use the quantum vacuum has nothing to do with the formalism that
made it possible. Several detailed QED calculations backed up by experiments
to astounding precision would be completely wrong and we know that's not the
case.

BTW, the fundamental principle is conservation of momentum, Newton's 3rd law
of motion is a consequence that sometimes doesn't hold, for instance forces
between charged particles in electrodynamics don't follow the 3rd law (but
approximately at low speeds). If you take into account momentum carried by the
fields you get conservation of momentum back, quite nicely as well.

~~~
forgotketchup
> I've been checking the (Word-generated) "papers" from this guy's group at
> NASA, they're extremely shoddy.

Not defending this _particular_ paper, but I'm curious why you highlighted the
fact that it's written in Word. Just about everybody in physics these days
uses Word to compose papers (Word + Mendeley is a dream, by the way). Maybe
you think he's not a 'real man' because he doesn't sling raw LaTeX?

~~~
shoyer
"everybody in physics these days uses Word to compose papers"

What subfield of physics have you worked in?

In my experience, this is not remotely true. Almost paper I read in grad
school (e.g., on arXiv/quant-ph) was written in LaTeX. The exceptions written
in Word were indeed quite likely to be the work of crackpots...

~~~
forgotketchup
>What subfield of physics have you worked in?

Experimental condensed matter physics (free molecular beams). Never met anyone
in my research group, or any other research group that anyone in my group
collaborated with, who _recently_ (in the past five years) composed a paper in
LaTeX. I'm sure my thesis advisor did so when he was in grad school back in
the dark ages, but even he uses Word.

> (e.g., on arXiv/quant-ph)

Yes, well, that _is_ where the crackpots tend to like to hang out, isn't it?

------
mrfusion
Why does number 7 say a superconducting version of this drive does not require
energy to hold things up?

Are they just referring to how superconductors can float in an external
magnetic field? That doesn't seem to give general purpose hover boards.

~~~
nanofortnight
Not requiring energy is a mistake from Wired.

A superconducting version of the drive would be able to provide much higher Q,
and thus much higher static thrust to power ratio.

It would also have much better performance at higher waveguide velocities.

[http://www.emdrive.com/theorypaper9-4.pdf#page=9](http://www.emdrive.com/theorypaper9-4.pdf#page=9)

------
vkal
I'm reading Contact by Carl Sagan right now and my heart kept fluttering as I
read this article.

I'm unqualified to comment on anything in this article, but this is really
cool, and I didn't know Wired produced science journalism (or a highly
technical Q/A) like this.

------
JulianMorrison

      A superconducting version of the EmDrive, would, in principle, generate thousands of times more thrust. And because it does not require energy just to hold things up (just as a chair does not require power to keep you off the ground), in theory you could have a hoverboard which does not require energy to float in the air.
    

If they have just solved flying cars and hoverboards, I think we can
officially declare this to be the future already.

~~~
MiguelHudnandez
> And because it does not require energy just to hold things up (just as a
> chair does not require power to keep you off the ground), in theory you
> could have a hoverboard which does not require energy to float in the air.

An item where you could dump electricity into it once, cut power, and have it
resist gravity -- forever, and for free! -- is absolute horse shit.

~~~
chopin
Any superconductor levitating on a magnet does exactly this. Afaik there is no
law in physics we know of which forbids this.

To put it even further: every stone lying on the ground does exactly this. It
doesn't change its position relative to the gavitational field. And without
expending any energy for that (or increasing the systems entropy ot hold its
position). And this comes ultimately down to electromagnetic forces (between
valence electrons) holding it at its position. So, no horse shit here.

~~~
MiguelHudnandez
A stone resting on the ground is simply halted at the place where gravity is
overpowered by the repulsion between molecules. Both of those forces are
applied constantly, and seemingly for "free." But those forces are inherent to
all matter.

Two magnetic objects can resist each other, but that is well understood
already. And still, those reach equilibrium between gravity (from the
levitator) and the strong force (from the support structure). From the way I
understand superconductive magnetic levitation, the magnetic field collapses
the superconductivity in the places they intersect. That would mean that over
time, electrical resistance would drain the [mostly] superconductive material.

Right now, all examples of superconductive levitation involve supercooled
superconductors, which means that any examples require massive amounts of
energy to sustain.

This hoverboard idea would be like taking the magnetic base away and expecting
the levitator to remain where it is with no extra energy supplied.

We've gone from "we can turn energy into motive force through unknown methods"
to "we can prime this thing with energy once and have it exert force forever."
If that were true, you could dump 1kw into the thing, rotate it 90 degrees and
attach it to a rotor. Now you've got this thing that constantly pushes your
rotor around and you've got free energy forever. See how I might think we're
in crazy town now?

------
DanielBMarkham
_A less conservative projection has an advanced drive developing ten times as
much thrust for the same power -- this cuts the transit time to Mars to 28
days, and can generally fly around the solar system at will, a true Nasa dream
machine._

If we had this plus a reduction of cost-to-orbit by a couple orders of
magnitude, say getting prices down to $10 per kilo? Space travel would
actually become a _thing_ \-- something available to most people. And we could
lower cost-to-orbit in a lot of proven ways, like using mass drivers for non-
human orbital insertions.

This is firmly in the "too good to be true" category right now, but hell, I'm
a believer. Even if we're wrong, even if there's some experimentation error,
science still wins. People are being energized, lots of imaginative scenarios
about space travel are playing out across the net, and so on.

This is a very good thing.

------
tgb
Wired gets some flack these days but that was a thorough article. Maybe I need
to read the actual paper now instead of just dismissing it off-hand.

------
madengr
Photons (i.e EM fields) have no mass, but do carry momentum and can transfer
it to charged particles (i.e. the solar sail). So if the drives uses EM field
to transfer momentum to the quantum vacuum particles, wouldn't that upset the
net-zero energy balance of the quantum vacuum? I though the particles are
popping in and out of existence, hence net-zero energy?

------
jobu
Best part of the article is the answer to question 9:

 _" 9\. Why isn't there a simple explanation of how it's supposed to work
without violating the laws of physics?"

"If the new drive results continue to be replicated, then theory may have to
catch up."_

Reminds me of the quote: "In theory, there is no difference between theory and
practice. But in practice, there is."

------
bitL
So what's the difference between what NASA does, what Chinese did with Em
drive and what Russians have orbiting in Yubileiny satellite?

More interesting question: can I make one at home? I can do magnetic
levitation, both pushing and pulling with high-frequency electromagnets; it
would be cool if I could do this as well and having floating objects in my
home 8-)

~~~
tobinfricke
" _it would be cool if I could do this as well and having floating objects in
my home_ "

The reported thrust of the device is in the tens of micronewtons. Assuming it
weighs 1 kg, you would need approximately a million times more thrust for the
device to levitate (i.e. counteract its own weight) at the surface of the
earth.

~~~
servowire
But in space a few micronewtons per Kg is pretty usable.

------
VikingCoder
"Prototype engine weighs about 15 kilograms"

"EmDrive, produced 91 micronewtons of thrust for 17 watts of power"

[http://www.wolframalpha.com/input/?i=91+micronewtons+*+1+yea...](http://www.wolframalpha.com/input/?i=91+micronewtons+*+1+year+%2F+15+kg+in+mph)

428 miles per hour, after a year.

Am I doing the math wrong?

------
jcfrei
Here's a demonstration video of the EmDrive in action:
[https://www.youtube.com/watch?v=57q3_aRiUXs](https://www.youtube.com/watch?v=57q3_aRiUXs)

However this test rig apparently doesn't adhere to the same strict
experimental setup used by NASA.

------
mangeletti
Shortest version:

They think it works, but we don't know how. More tests will tell whether or
not we have finally discovered the technology required to drive around easily
in the solar system and propel skateboarding into the realm of Back to the
Future.

------
noselasd
Besides the frequency of the electromagnetic waves , is this the same concept
as the "Pioneer Anomaly" \- where they eventually figured out it was thermal
radiation emitted from its satellite dish which slowed down the spacecraft ?

~~~
jahnu
As far as I can tell it wouldn't matter what the cause of the apparent effect
is. Not requiring reaction mass is what makes it interesting.

~~~
Mandelbug
What? Of course the apparent affect matters. If the underlying physical
principles can be understood, there is a possibility of increasing its
efficiency for larger throughput. And if the underlying process isn't
understood, there is no way to rule out something that isn't actually
producing thrust or some other fluke.

Finally, the whole point of science is to discover things. Not make magic :|

~~~
ep103
I think what he means is even if it turned out to just be thermal energy, then
that means this device has the capability of directing thermal energy as a
viable proportion source, so its still pretty great : )

------
gus_massa
Short version:

Unless they believe the machine breaks some of the fundamental physics laws,
the device must emit something. With this definition using a red LED Laser
powered by a 1.5V battery in the back of the spacecraft is a "no reaction
mass" thruster. The problem is that the momentum / energy ratio has
theoretical limitations, and they are getting too much momentum.

Long version (based on a previous comment
[https://news.ycombinator.com/item?id=7162069](https://news.ycombinator.com/item?id=7162069)):

I’ll try to explain what I had understood trying to find an explanations that
don’t break the physics laws.

To move the spaceship you _need_ momentum. You _must_ use some particles to
carry the opposite momentum away. It’s not clear, but the main candidates are
photons (aka light). (The other possibility is gravitons, but that would be
even more amazing)

The photons have no rest mass, but they have energy. So to produce them, you
must "spend" some energy. The energy source can be carried in the ship (a
nuclear reactor) or absorbed in place (solar panel).

If you are using a nuclear reactor, a small par of the mass of the atoms is
transformed into energy and you put that energy in the photons. So the net
effect is that some of the mass of the spaceship goes away, and it's no long a
"no reaction mass" ship. (The same idea is valid to electric batteries, but
the mass difference comes from the chemical bounds and not from the nucleus.)

If you use a solar panel, then when you absorb the photons the spaceship gains
a little of mass. Unless you have a mechanism to dissipate the mass the
spaceship would get heavier. Luckily, the photons that you are using for
propulsion carry a little of mass (and the heat you are dissipating also
helps). So this is essentially a solar sail, you get some photons, and send
them in a different direction, and the change in the direction of the photons
give some momentum to your ship. Perhaps a complex setup (solar panel + led)
can be more directional that a simple setup (mirror). Perhaps you can gain a
x3 or x6 efficiency. (But someone has to do the calculations, because this
might break the second law, unless you get a laser light and also dissipate
some heat without a specific direction, and the net result as good as a
mirror.)

In the previous comment, throwaway_yy2Di noted that with photons "the ratio a
photon's momentum to energy is fixed at 1/c, which is 3.3E-6 N/kW". The
problem of photons is that to get some moment you need a proportional amount
of energy to create them. Another possibility is to create particle-
antiparticle pairs and accelerate them, but this is even more inefficient that
using photon and you get less than 3.3E-6 N/kW.

The alternative solution is to accelerate other particles (for example the
hydrogen atoms in the rocket fuel), you don't need energy to create them,
because they are already there. So you can get more than 1/c=3.3E-6 N/kW, but
it's not a "no reaction mass" ship.

They claim 40 microNewton/28W = 1.4E-3 N/kW ~= 400000/c. This is in the like
400000 times the theoretical limit, so they have a measurement problem (or
they'll get a Nobel price).

~~~
chton
While it's true that most reactionless drives break some of the most basic
physical laws, that's not the case for all of them. An Alcubierre drive is a
good example of a propulsion method that works within the current laws, yet
does not emit anything.

The idea that the designs they tested (and EmDrive) would be reactionless is
exactly why everybody is so baffled and excited by this. If they are, they
must have some way to maintain those basic laws, through a process we don't
know about yet. Aside from the practical uses, it could lead to a whole new
physics to study.

~~~
gus_massa
Alcubierre drive is not a thruster, you can't attach it to a spaceship to move
it. It's something like: "If you put a spaceship inside this, and it
stabilizes the gravity field using that, then it will travel faster than light
in an external reference frame." It travels at a constant speed, so it doesn't
need to emit particles to change the momentum. (On the other side, it uses
exotic matter that no one has ever seen, so it may be impossible to
construct.)

When you say "reactionless" you mean that the device doesn't emit anything and
it breaks the momentum conservation law? The previous experiments tried to
give some theoretical explanations, but usually they were equivalent to
emitting photons or gravitons. The conservation of momentum is a very
fundamental law. It's possible to change the physics laws, but you need to
have very good experimental evidence. (Hey! I believe in the Higgs boson!)
This is like the faster than light neutrinos. It's very exiting if it were
true, but the easier explanation is an experimental error.

~~~
jliechti1
I asked a particle physicist to compare the validity of this to the faster
than light neutrino claim that came up and his response was:

 _" Although several people are drawing that comparison, they're really not in
the same class. OPERA did an extremely thorough analysis of the faster than
light neutrino result before they published. In the end it turned out to be a
very subtle experimental error that cause the problems.

In contrast, this is just junk science from start to finish. The initial claim
was likely an outright lie to lure investors."_

~~~
smellf
But there's three independent labs working on this concept, plus NASA. _Who_
is lying, the EmDrive folks? And if they are, then how are NASA, the Chinese
and the other lab all replicating their results?

~~~
XorNot
By not testing it in a vacuum, which would eliminate most of the immediate
problems with thrust being produced by outgassing from heated wires (10kW is
more power then your stove top) or coronal discharge.

I don't know what's going on with whoever is doing this at NASA, but the joke
of testing IN A VACUUM CHAMBER while not actually pumping it down is
ridiculous. These people are scientists who have access to the device - how
did they not turn it on? For lack of a suitable capacitor? That's a nothing
part for such a massive potential breakthrough.

~~~
pavlov
The OP (Wired article) says that the vacuum chamber was indeed pumped down:

 _While the original abstract says that tests were run "within a stainless
steel vacuum chamber with the door closed but at ambient atmospheric
pressure", the full report describes tests in which turbo vacuum pumps were
used to evacuate the test chamber to a pressure of five millionths of a Torr,
or about a hundred-millionth of normal atmospheric pressure._

~~~
XorNot
Yeah just saw that part. The abstract doesn't mention it, which is super-
weird, and neither did the original Wired article.

But if they found the effect persisted when pumped down then that puts this
way further into "interesting" territory.

EDIT: Ok I've just been through the paper, but it's buried at the end -
"Vacuum compatible RF amplifiers with power ranges of up to 125 watts will
allow testing at vacuum conditions which was not possible using our current RF
amplifiers due to the presence of electrolytic capacitors"

There is a big description of the test rig, and how it can be pumped down to
vacuum during tests, but they do not explicitly say that they pumped down to
vacuum before running tests on the thruster. And the vacuum is never mentioned
again until the very end, where we get this one ambiguous sentence. They might
be referring to a new optimized thruster they couldn't test, or they might be
saying they couldn't test in vacuum at all - it's never made clear and it's
pretty damn important.

------
Gravityloss
The most important question that should have been top center: with
reactionless propulsion it is possible to create a free energy device.

Attach the thruster to a wheel.

When the thruster is firing, it consumes constant power and the wheel
accelerates, spinning ever faster.

The wheel can be attached to a generator that produces power which is thrust
times the rim velocity.

Thus, after a certain speed, the wheel produces more power than the thruster
consumes.

This was discussed on a rocketry list.

~~~
ghshephard
I"m not following why you think the wheel generator will produce more power
than is required to spin the wheel in the first place. Friction is a pretty
big issue in your scenario. It seems orthogonal to the actual results.

~~~
Gravityloss
The whole thing was a thought experiment to show how extraordinary the
supposed result is.

Power of the wheel = thrust * rim velocity. That's just basic physics you
should learn in high school.

    
    
      P_1 = F * v
    

This means if your force, that is, thrust, is constant, you generate more
power the faster you go. That's also why cars accelerate faster from 20 to 30
km/h than from 120 to 130 km/h - they have constant power which means they
have more force at lower speeds and thus higher acceleration at lower speeds.

The claimed thruster produces a constant thrust for a certain power, let's use
a factor k for that:

    
    
      P_2 = k * F
    

Now if we want perpetual motion, we can set P_1 = P_2, and solve

    
    
      F * v = k * F
          v = k
    

If we let the speed be faster, we can actually generate power from the wheel
in excess of what the thruster uses.

We can also have some friction, let's say the wheel generator is 50%
efficient. We then need to run the wheel twice as fast to get the same effect.

There actually exists a trivial "reactionless" thruster if we use a flashlight
and the light pressure. But it turns out the velocity is the speed of light
then.

~~~
gus_massa
I totally misinterpret your first comment. It looks like "This is even more
amazing! We have a perpetual mobile machine!!" but it's really is "This also
break the energy conservation law! So we have a serious problem."

In special relativity, momentum and energy are much related, so if you break
the conservation of one of them, you break also the conservation of the other.
(It's not very clear if the authors say that this device break the momentum
conservation, all the information is very confusing.)

But the example is nice. Just get two of these devices and put them in the
opposite sides of a carrousel or a spinning space station so you don't have to
worry about friction.

~~~
Gravityloss
Thanks for the comment, now I realize the post was not very well written in
that regard. It is hard to express these contradicting ideas in a small space:

1\. If this works, forget spacecraft. Free energy for everyone! 2\. I think
it's a measurement error.

There are other reasons to think so as well, a person said that the "out
there" advanced space propulsion research community traditionally gives a lot
more leeway than some other research disciplines where this might have come
up.

------
bad_user
Given the steady push of this drive, if it actually works can it be said that
a significant percent of light speed could be reached?

------
grondilu
I liked the comparison with high-temperature superconductors. We don't exactly
know how they work either. But they do work.

~~~
leni536
The analogy is not perfect though. High-temperature superconductors are not
breaking well established principles in physics. We just can't describe these
superconductors well now.

Most of the limitations describing solid state materials come from that we
can't solve the Schrodinger-equation directly (even with simulation). So we
have to make assumptions and reasonable approximations of the resulting wave
functions of electrons. For many solid state materials there are standard
approximations that are working really well but they are not working for all
materials.

We simply didn't find any working approximation for high-temperature
superconductors (but I think there are some not well tested theories out
there).

------
spingsprong
Please be true, please be true!

How big is a two megawatt nuclear power source anyway? A quick search showed
nuclear power plants are in the hundreds to low thousands of megawatt range,
and RTGs are in the tens to hundreds of watt range. I have no idea what
something that lies between those two would be.

~~~
tgb
Wikipedia gives the generator of Loss Angeles class nuclear submarines to be
26 MW [1]. I don't know whether you can make them as successful in space
without the access to ambient water.

[1][http://en.wikipedia.org/wiki/Los_Angeles_class_submarine](http://en.wikipedia.org/wiki/Los_Angeles_class_submarine)

~~~
madaxe_again
The principle problem to be overcome with this tech is going to be cooling -
both for the power source and for the drive. It's going to require radiators
the with a stonkingly huge area and Peltier shunts, unless we come up with a
cunning means of dumping excess heat - potentially turning it into more energy
to drive with, even, using the seebeck effect.

~~~
runj__
Isn't space pretty cool?

~~~
damoncali
As cool as space can be, it can also be incredibly hot. It's not uncommon to
see huge temperature variations on the same object based on whether or not the
surface in question is pointing toward or away from the sun. In any case, as
others have said, there is no conduction or convection in space - only
radiation, which needs a little help some times.

For an example, when I worked on the Hubble, a thermal short was discovered
that would severely limit the life of one of the cameras, which have to be
very cold to operate. In order to counteract that, a pretty complex cooling
system was built to counteract the effect. It consisted of a couple of large
metal boxes (a couple hundred pounds each, if I recall) attached to a couple
of huge radiator panels. (About 3'x10' each, if memory serves). The whole
thing took over a year to build and took a lot of care to launch and install.

------
readerrrr
This is very exciting; a new propulsion method that already works much better
than existing thrusters, doesn't need propellant and without requiring years
of research.

It sound too good to be true. My bet is on experimental error.

------
crusso
Doesn't this remind anyone of the not-so-long-ago overhyped E-Cat?

[http://en.wikipedia.org/wiki/Energy_Catalyzer](http://en.wikipedia.org/wiki/Energy_Catalyzer)

~~~
tensor
Not at all. Unlike the e-cat, the design here is clear and it sounds like it's
independently verified from the ground up with good experimental conditions.

The e-cat had "secrets" that they wouldn't divulge and it's tests were also
questionable with the machine being plugged into a power source the whole
time.

~~~
crusso
"verified from the ground up with good experimental conditions"

No it hasn't. That's the hype. Read the Baez commentary referenced elsewhere.
Research all the other physics breaking phenomenon that had experimental
confirmation but were still shown to be wrong.

It's not like this effect was just noticed yesterday. You'd think that for an
effect that Shaw created a company for in 2000, we'd have solid experimental
results by now that addressed every single problem.

It mostly reminds me of the E-Cat in that there are people who want it to be
true so badly that they cherry pick the results and statements that they want
to believe while disregarding contraindications.

~~~
snowwrestler
The emdrive is being tested by NASA staff, who did not invent it. That alone
is a very significant difference from the ecat, which was only ever
demonstrated by its creator.

Now NASA is still probably wrong, but if so, they are innocently wrong. They
wouldn't gain anything by faking an effect.

If anything, they are getting heaping abuse for reporting anything at all.
Which I think is a problem for science. People should not be abused for
honestly trying to test surprising things, even if they turn out to be wrong.

~~~
crusso
Read the Baez blogs. Read the Discovery mag blog that shows that this is
barely "NASA". It's really a few fringe scientists who have a reputation for
hyping pseudoscience.

When they had a chance to look critically at their own experiments in their
report, they spent effort and text hyping theoretical applications or
something like that. They deserve some "go back and do it right this time,
junior" criticism.

I'd rather they not waste our tax dollars on this kind of nonsense.

~~~
snowwrestler
I read them all, and I think you and Baez are making a mistake. Not on the
science, on the style.

When a person "invents" something that is obvious bullshit, and uses that as a
means to milk money out of investors or consumers, that is fraudulent. Over
the past 30 years a style of communication has been developed that uses
sarcasm and outright mockery to attack these people. James Randi practically
invented this style of communication, or at least greatly popularized it, and
now it has been adopted by a number of science bloggers.

Why, though? Because fraudsters are good at attracting attention, so to
counter it, critics have to generate controversy. And there's no better way to
generate controversy than to make things personal. In other words, it's done
with a purpose.

But over time that communications strategy has been warped by people who don't
understand it. They think the idea is to personally attack and mock ANYONE who
reports a surprising result. We saw it with the FTL neutrino results, we saw
it with BICEP2, we see it all the time.

It's a major problem. For one thing it trains non-scientists to auto-reject
any scientific result that seems weird to them. For another thing it gives
greater license to people who _are not_ critiqueing science in good faith
(like, say, Rush Limbaugh or Ken Cuccinelli) to attack scientists personally.
It reduces its utility as a means of countering fraud, because people come to
think that that is just how science communication is done. And it makes it
harder to obtain sufficient funding to investigate areas of science that are
not as well-known to the public.

What's happening here is not attempted fraud. A team at NASA [1] that is
specifically employed and funded to test out crazy ideas, tested out a crazy
idea, and published their results. That's it.

So, critique their methods and results? Yes. Critique the press coverage?
Absolutely. Attack and mock the researchers? NO. Doing so is a fundamental
mistake in communications strategy.

And some of the critiques are even self-contradictory. For example you suggest
that they should go back and do it right, but you also don't want them to
spend tax dollars on it. Well, the quality of an investigation is directly
affected by its level of funding. The NASA crazy ideas lab is minimally
funded, so of course not every detail can be worked out. The researchers
_explicitly state this_ in their paper.

[1] And yes, they are employees of NASA...saying "this is barely 'NASA'" is a
nonsensical statement.

------
davedx
Is this the same thing as the Q-thruster?

[http://en.wikipedia.org/wiki/Quantum_vacuum_plasma_thruster](http://en.wikipedia.org/wiki/Quantum_vacuum_plasma_thruster)

~~~
noselasd
Yes, the that wikipedia article eve references the very same device in
question built by Guido Fetta that NASA tested.

------
mrfusion
Would this be how impulse drives are supposed to work in Star Trek work? Just
curious.

~~~
tobinfricke
As you may be aware, Star Trek is a work of fiction.

~~~
mikeash
And beyond that, a work of fiction that focuses on storytelling first, and
science... well, not second, but maybe twenty-ninth or so.

Which is not a criticism. Not all science fiction has to be hard. But none of
the technology is a product of scientists sitting down and thinking about how
the technology of the future might work. It's a product of writers thinking
about what technology would make for good stories, and any explanation you
come up with (e.g. impulse drives are reaction drives with warp fields that
let them have an exhaust velocity higher than the speed of light) is a
retrofit made up to appease fans and sell more books.

------
cookiemonster11
It's probably powered by N-rays.

------
thisjepisje
Where can I find blueprints?

~~~
marcosdumay
At the paper. And it's crazy simple.

~~~
servowire
I can't find prototype diagrams with dimensions or something, did you find
any? Please link?

The paper is $25 .... mmm
[http://arc.aiaa.org/doi/abs/10.2514/6.2014-4029](http://arc.aiaa.org/doi/abs/10.2514/6.2014-4029)

This post has some more info
[https://plus.google.com/117663015413546257905/posts/WfFtJ8bY...](https://plus.google.com/117663015413546257905/posts/WfFtJ8bYVya)

~~~
colanderman
Regarding the EmDrive…

OK, so, there's microwaves producing forces on either end of the cavity, and
one end is bigger and…

 _wouldn 't the forces be proportional to the area normal to either
direction_? i.e. one end may be smaller, it may even be a point (making the
cavity a cone), but microwaves bounce off of the tapered neck of the cavity
too.

------
pistle
Ugh. That's a Buzzfeedy title if ever there was one. I'm surprised it isn't:

Space Scientists Don't Want Obama To Know These 10 Secrets About Warp Drive

~~~
nsxwolf
NASA Scientists Resonate Microwaves in a Cavity - You Won't Believe What
Happens Next!

