
NASA presents evidence that microwave thrusters seem to work - jchesters
http://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-drive
======
daeken
Wow. My gut tells me something is wrong here, and that this is being
mismeasured. However, this would be an _enormous_ breakthrough if it pans out,
even at the low levels NASA has seemingly confirmed.

We're very good at generating power in space; solar is basically infinite in
the inner parts of our solar system, and we have a lot of experience with RTGs
and other power generation mechanisms. If we can directly turn power into
thrust without burning fuel in the process, this truly changes everything.

But as I said, I think this will end up not panning out for one of these
reasons: 1) The microwaves bouncing around cause a small amount of material to
be lost and be sent out of the device, causing the thrust. 2) The RF in play
is throwing off detection (this, to me, seems most likely -- it could explain
the thousandfold difference in detected thrust levels between the Chinese and
US tests). 3) Some sort of effect that is linked to gravity. No idea what,
though.

I really look forward to further testing.

Edit: Given that I'm terrible with the scale of small numbers, I decided to do
some quick math. If you were to use that thrust of 50 micronewtons to drive
the Voyager spacecraft (722kg) full out for one year from a starting velocity
of 0m/s, you would end up at 0.0911259m/s at the end of the year. By
comparison, Voyager is currently traveling at 17km/s.

~~~
skriticos2
NASA is running out of fuel (Plutonium) for RTG's and no new fuel is produced.

[http://www.isciencetimes.com/articles/6087/20130919/nasa-
plu...](http://www.isciencetimes.com/articles/6087/20130919/nasa-plutonium-
problem-deep-space-exploration-battery.htm)

~~~
astrodust
It's impossible to run out of plutonium so long as uranium fuelled reactors
are running. It's a common by-product of the fission process.

It maybe be harder or impractical for them to get it or process it, but saying
"no new fuel is produced" is false

~~~
DennisP
Normal uranium reactors produce a mix of plutonium isotopes, which are hard to
separate and end up as nuclear waste. NASA needs pure Pu-238, which has to be
made in specialized reactors.

~~~
Pxtl
Iirc, all Canadian CANDU reactors produce large amounts of weapons-grade
plutonium.

~~~
sanxiyn
Which is exactly the problem. RTG needs Pu-238, and can't use weapons-grade
plutonium, which is mainly Pu-239.

------
tribaal
So, it seems from reading the paper's abstract that they did measure thrust
_both_ from the real propulsion test device and from the dummy test device.
That's not very promising:

[http://ntrs.nasa.gov/search.jsp?R=20140006052](http://ntrs.nasa.gov/search.jsp?R=20140006052)

> Thrust was observed on both test articles, even though one of the test
> articles was designed with the expectation that it would not produce thrust.
> Specifically, one test article contained internal physical modifications
> that were designed to produce thrust, while the other did not (with the
> latter being referred to as the "null" test article).

~~~
ape4
Would have been nice if the scientists didn't know which device they were
testing - blind.

~~~
PeterisP
The purpose of blind testing in medicine is to eliminate the possible effects
caused by different patient-doctor psychological interactions.

If we find out that inanimate objects behave differently if the operator
does/doesn't believe in their success (as patients do), then that'd be much
bigger news than engine development.

~~~
db48x
Blind testing is still very important in physics; go look up N-rays.

------
api
Third replication then?

This stuff has been hovering (pun intended) at the edge of detection for some
time: spinning superconductors, this thing, etc. all claiming to provide
evidence of tiny amounts of thrust in apparent violation of standard
conservation of momentum. Obviously skepticism is in order, but either
something is very wrong with all these experiments or there's something here.

What's interesting about this one is that the original inventor has something
resembling a theory. It may not be a complete theory, but it tries to explain
it via relativity in a way that makes physical sense.

I'm always really skeptical of these things, but not in the knee-jerk total
dismissal sense. I just say show me the replications. They're doing the right
thing. Now we need more people to build these and test them under different
conditions.

The ultimate test would be to launch one, since you can't really screw up
detection of a big delta-V change in space.

~~~
codeflo
I'm not a physicist and I can't debunk this theory point by point, but
actually, you don't need to know much physics to see how this must be wrong.
Special Relativity _requires_ conservation of momentum, in every observer's
frame of reference. If someone claims to explain supposed non-conservation of
momentum by invoking "Special Relativity", they are just attempting to trick
you.

(As far as crackpot theories go, I'm actually surprised they didn't throw in a
"quantum" or two for good measure.)

(Edit: I'm not saying that the experiment itself is invalid. It might be, I
don't know. What I'm saying is the supposed theory[1] is necessarily wrong,
because you can't get non-conservation of momentum out of Special Relativity
without suggesting new laws of physics, which is not at all discussed in the
"paper" I linked below.)

[1]
[http://www.emdrive.com/theorypaper9-4.pdf](http://www.emdrive.com/theorypaper9-4.pdf)

~~~
api
Like I said, the best test would be to put one in space. If you fire the thing
up an the satellite's orbit changes, that's kind of a hard measurement to
screw up. (Let it orbit with the drive off for a while as a control.)

~~~
cstross
_If you fire the thing up an the satellite 's orbit changes, that's kind of a
hard measurement to screw up._

Caution: a re-reading of the Pioneer Anomaly is in order before you start
assuming things in microgravity move because of new physics ...

------
PaulHoule
This is one of these things which is just a few percent less crazy than it
sounds.

The issue is that special relativity isn't quite compatible with quantum
gravity, see

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

What it comes down to is that quantum gravity has a length scale and a time
scale, both of which are unthinkably tiny. However, special relativity says
there is nothing special about any particular space or time interval because
if somebody was going fast enough, an interval that looks like a planck
interval to most people could get expanded or shrunk to something big like a
kilometer or an hour.

But following that line of reasoning is problematic if there is no special
reference frame, since for all I know I already am going incredibly fast
relative to some imaginary observer.

Doubly-special relativity manages to preserve the invariance of the speed of
light under ordinary conditions but also preserve the invariance of plankian
quantities under extreme conditions. Related theories also bring in the idea
of a special reference frame which means you might be able to "push" against
the vacuum.

The main trouble jiving that with these experiments is that the energy scale
at which DSS effects come into play is huge, way out in grand unification
country, so it's hard to believe it could be probed by these experiments.

------
nsxwolf
I've always thought it was unfair that this is impossible. It's not like
you're getting something for nothing - you are still required to expend
energy. So why does the universe have to be such a dick about converting
electricity directly into motion?

~~~
DickingAround
Where can I read more about how/why this is impossible? Isn't it just the
reverse of a solar sail to send out the photons yourself rather than catching
them? It seems like shining a flashlight in one direction should produce
thrust in the other. Is that not true or is it something different at work
here?

~~~
nsxwolf
I guess a related question is "why does a flashlight in space not propel
itself". And I don't know the answer to that.

Edit: Ok. That makes sense. I guess it's just not a practical source of
propulsion.

~~~
dragonwriter
A flashlight in space does propel itself, but that's not really a related
question. A more related question is why does a flashlight in a fixed mount
inside of a windowless spacecraft not propel the spacecraft (or, similarly,
why does a fan inside of a sealed, ventless housing attached to an airplane
wing not function as an engine.)

Of course, if there's some way this _does_ work despite what we think we know
about physics, its a pretty gigantic breakthrough (well, at least,
understanding and practically applying it would be -- otherwise its just an
anomaly that provides a pretty gigantic question mark...)

------
louthy
For all those saying this is impossible because of X, I think the great
Richard Feynman put it best:

"If it disagrees with experiment, it's wrong"

[https://www.youtube.com/watch?v=OL6-x0modwY](https://www.youtube.com/watch?v=OL6-x0modwY)

~~~
Steuard
Experiments this delicate are very difficult to get right.

And it is very difficult to overstate just how much established physics would
have to be scrapped if momentum conservation turned out to be violated. (Just
for starters, relativity implies that non-conservation of momentum in one
frame must always involve non-conservation of energy in another.) Why would
quantum field theory calculations match experiment to ~12 digits of accuracy
if its basic foundations were flawed? (Those calculations are affected by
literally every possible quantum vacuum effect, so why wouldn't introducing
some new set of momentum violating interactions completely throw off the
results?)

This is an astoundingly extraordinary claim, and it should thus require
tremendously compelling evidence. I'm not at all convinced that these
experiments are clean enough or consistent enough to even approach that
standard.

------
FatalLogic
Previous discussion, from six years ago:
[https://news.ycombinator.com/item?id=314297](https://news.ycombinator.com/item?id=314297)

Some interesting comments, and much skepticism

------
Symmetry
So it produced 720 mN of thrust the first try, but under more careful
conditions it produced 30 uN? This smells like a spurious result, but I
suppose more investigation is in order.

~~~
moron4hire
Two different devices, Shawyer's "EmDrive" was the 720mN device, Fetta's
"Cannae Drive" was the 30uN device.

------
zackmorris
Wanted to jump in and ask, does anyone remember a site that went through the
math of two magnetic rings being charged and discharged out of sync, utilizing
the delay in the speed of light between the rings to create a net force?
Imagine a craft shaped like a dumbbell, with the rings where the weights are:

|---|

1...2

The idea was that you'd create a strong magnetic field in ring 1, and then the
wave would travel outward both directions (one away from the ship, and one
along it) and interact with ring 2, which has the opposite polarity. Ring 2
would be attracted to the magnetism from ring 1, and pull the ship to the
left. Then ring 1 would turn off, and by the time the wave from ring 2 reached
it, there would be no interaction. So the craft would feel a net thrust to the
left. The process would repeat over and over again at high frequency,
propelling the craft faster and faster.

I believe the site said the process was 25% efficient, and didn’t violate any
laws of physics. The difficulty lies with hysteresis because it takes a
comparatively long time to charge a magnetic field, compared to the time it
takes light to span the distance. So it went off on a tangent about using
lasers to charge a superconducting ring.

But I’ve always wondered if resonance could somehow be used to take the coils
out of sync automatically, a bit like a tesla coil but with an imbalance the
puts one ring slightly behind the other in time with respect to their frames
of reference. As they move more out of phase, the net force on the coils
should get stronger and stronger. This sounds similar in some ways to the the
way a magnetron works, so if it can be put out of phase in a similar way, then
I’m not entirely surprised by NASA’s result. If it’s true that the time delay
in the speed of light can be converted to a propulsive force, then it’s going
to change, well, pretty much everything about space travel. I really wish I
had the link to that site.

~~~
Terr_
Was it something like this?
[http://arxiv.org/html/physics/9908048v2/conclusion.htm](http://arxiv.org/html/physics/9908048v2/conclusion.htm)

> Then ring 1 would turn off, and by the time the wave from ring 2 reached it,
> there would be no interaction.

That sounds like the magic part. "Magically, nothing will occur." IANA
physicist, but it sounds like Lenz's law might be relevant.

> I believe the site said the process was [...] didn’t violate any laws of
> physics.

Well, there's the rub. It sounds like it directly violates conservation of
momentum and Newton's third law.

~~~
zackmorris
That's not the one, but it's along similar lines. The site had lots of
graphics and was written in layman's terms. I think I first read it around
1999 or 2000, and then lost it.

I agree with the others that any force above light pressure would appear to
violate Newton’s laws.

However, I have never seen an analysis or simulation that incorporates the
delay in the speed of light. Ring 1 would be limited to light pressure, and be
symmetrical, but ring 2 would dissipate one half of the wave by canceling it,
so technically only 3/4 of the energy would be emitted if we thought of the
whole system as a black box. The other 1/4 would have to go somewhere,
probably mostly heating the rings but some of it could go into the box as
kinetic energy.

I think an easier way to run the experiment might be to set up a square wave
with a duty cycle of 25% and a period equal to the time it takes for light to
propagate between the rings. Then it would just be a matter of varying the
phase on one of the rings and seeing if there’s a net force on the setup. With
a spacing of 10 centimeters, there would only be 0.33 nanoseconds to build a
magnetic field, and it’s going to fall by the square of the distance between
coils, unless we could use the long wire approximation for large coils which
falls linearly by distance:

[https://en.wikipedia.org/wiki/Ampère%27s_force_law#Equation](https://en.wikipedia.org/wiki/Ampère%27s_force_law#Equation)

The forces might be small but they should be measurable, and if they are even
a fraction of a percent above light pressure, it’s a really big deal. Maybe
the duty cycle should be 33% or 50%, maybe the period should be double or half
this, maybe another waveform would be more efficient, but you get the idea.

Blah what I wouldn’t give to have the disposable income to work on this and
the hundred other half-baked ideas laying around the house. It’s a special
kind of hell to toil away one’s life making rent while watching the wondrous
breakthroughs of the world spring forth from other people’s minds.

------
hyperliner
I wish this had an ELI5. Anybody out there that can help us mere mortals?

~~~
fixermark
To boil it way down: The root claim is that there is a way to craft a special
closed box that when you apply electricity to it, the box starts moving
(linearly) without either pushing off of anything or throwing anything out. If
that were true, it'd mean an awful lot for space travel; changing direction in
space requires a ship to either crash into something or throw bits of itself
away until it runs out of bits. If this thing works the way it is claimed to,
a spaceship using it could control its motion forever, powered by merely the
light of the nearest star.

(... it probably doesn't work the way it's claimed to, because if it does,
there's a lot of interesting things we should already have seen by now in the
"closed boxes moving around as if by magic" category; the universe is a big,
big place of big, big possibilities. But lack of observation doesn't make it
impossible, just unlikely).

~~~
Natsu
Makes me wonder if it could somehow convert the energy to mass and throw that
off, as it were. Though it's probably something more exotic, assuming it's not
an error of some type.

~~~
marcosdumay
"Convert energy to mass" does not make much sense. If you throw light away,
it'll propel you.

~~~
Natsu
I was thinking electrical energy, but you raise a good point that photons have
momentum.

------
DanielBMarkham
"...therefore is potentially demonstrating an interaction with the quantum
vacuum virtual plasma..."

This could be extremely big news, like the biggest news of the last 50 years.
Depends on whether it's true -- and how much it can be optimized. Field
propulsion is a game-changer in humanity's relationship to the universe.

Lots remain to be seen, though. Wait-and-see is the appropriate response.

Still pretty neat. And it sounds like something that could easily be
reproduced in college-level labs worldwide.

------
lutorm
There's no mystery to producing thrust with microwaves. Photons have a
momentum of E/c, so if you make photons with a power P and send them in one
direction, you'll get a thrust of P/c.

I think the issue is that they claim to a) not emit anything, and b) claim
many orders of magnitude more thrust than could be achieved by just emitting
photons.

------
ixtli
Pedantic, but NASA is an acronym. Am I unaware of a British English
composition rule that permits writing it "Nasa"?

~~~
IvyMike
The Guardian/Observer style guide specifically uses Nasa as an example:
[http://www.theguardian.com/guardian-observer-style-
guide-a](http://www.theguardian.com/guardian-observer-style-guide-a)

> Use all capitals if an abbreviation is pronounced as the individual letters
> (an initialism): BBC, CEO, US, VAT, etc; if it is an acronym (pronounced as
> a word) spell out with initial capital, eg Nasa, Nato, Unicef, unless it can
> be considered to have entered the language as an everyday word, such as
> awol, laser and, more recently, asbo, pin number and sim card. Note that pdf
> and plc are lowercase.

~~~
troymc
I've never heard of that way of handling acronyms before.

The site is WIRED UK. Maybe it's a UK thing?

My first reaction was, "That's not how you write NASA; This author/editor is
an idiot. How can I trust anything they've written here?" I doubt that's the
reaction they want.

Now I just feel sorry for the author whose writing is forced to look weird to
many readers.

Over time, maybe people will just come to recognize it as "a British thing"
just like they recognize aluminium as the British spelling.

~~~
lotsofcows
I feel sorry for USAian authors whose writing is forced to look weird to many
readers...

~~~
Crito
Does _" NASA"_ actually look weird to anybody? That's how NASA themselves
write it... so do you Brits think that everything NASA publishes with their
name on it looks weird?

I say defer to however the organization in question writes it. That should
surely lead to the least confusion and weirdness. It would certainly help UK
news organizations with consistency:

* "CARE International": [http://www.theguardian.com/lend-with-care/entrepreneurs-seek...](http://www.theguardian.com/lend-with-care/entrepreneurs-seeking-a-hand-up)

* "Care" _and_ "CARE": [http://www.theguardian.com/lend-with-care/tackling-the-root-...](http://www.theguardian.com/lend-with-care/tackling-the-root-causes-of-poverty)

* "Nasa" _and_ "NASA" (But "Ladee" rather than "LADEE"): [http://www.theguardian.com/science/video/2013/sep/07/nasa-la...](http://www.theguardian.com/science/video/2013/sep/07/nasa-launch-moon-probe-ladee-video)

~~~
lotsofcows
In logos I agree but in normal writing it always looks like unwanted emphasis
too me.

I think there's a cultural difference here, USAian papers kept up the many
founts with underlining, etc thing long after it had become unfashionable in
the UK.

The norm is the norm - whatever you're used to.

...which is what my previous post was supposed to highlighting. Somebody took
it personally :-(

------
Tloewald
The top comment (on the actual article) suggests that the effect may be a
result of dark matter resonance:

[http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111...](http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.231801)

Which is way over my head, but interesting.

------
zerker2000
Is anyone reminded of
[http://www.bibliotecapleyades.net/tesla/occultether/occultet...](http://www.bibliotecapleyades.net/tesla/occultether/occultether.htm)?
Which is complete pseudoscience but...

------
toolslive
Is this the stuff Miklos Borbas was working on?
[https://www.youtube.com/watch?v=RbOc6R-95kk](https://www.youtube.com/watch?v=RbOc6R-95kk)

------
PaulAJ
Could the electromagnets involved in microwave generation be interacting with
the Earth's magnetic field?

~~~
zackmorris
Anything's possible, so they really need to do the experiment with Helmholtz
coils inside a Faraday cage:

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

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

------
cLeEOGPw
It's logical when you think about it. Since particles pop in and out of
existence all the time and the time these particles exist are > 0, then it
should be possible to move those particles before they disappear. So law of
conservation of momentum is not violated, neither any other law of physics. It
is just counter intuitive, like most stuff related to quantum world.

~~~
claudius
I’m not quite convinced. If I understand you correctly, what you’re saying is
the following:

Suppose we send out one photon ν of momentum p_ν. We hence gain momentum -p_ν.
This photon then randomly hits a particle X of a particle-antiparticle pair
and transfers its momentum/energy to the particle X, creating/altering it into
a particle X'. When X' and ¬X collide again, this momentum/energy is lost and
doesn’t hit the opposite wall of the cavity (where it would be transferred
onto us again, causing us to lose the previously-gained momentum -p_ν).

But this would require that when X' and ¬X annihilate each other, the extra
momentum of X' is also annihilated. Intuitively, I’d expect it to be sent out
as a photon – with momentum p_ν.

~~~
cLeEOGPw
How do you imagine annihilation of the extra momentum?

~~~
claudius
I don’t.

~~~
cLeEOGPw
So why you expect it to happen?

~~~
claudius
I don’t. That’s why I wrote:

> But this would require that when X' and ¬X annihilate each other, the extra
> momentum of X' is also annihilated. Intuitively, I’d expect it to be sent
> out as a photon – with momentum p_ν.

I.e. annihilation of the extra momentum would be required for this to work on
the basis of background fluctuations (in my understanding), but I don’t think
that this happens.

------
jsilence
Quantum mechanics, dreams stuff is made of.

------
cpfohl
Although unrelated, the title reminded me of a certain Improbability
Drive..."Not again..."

