
NASA's 'impossible' EM Drive works: German researcher confirms (2015) - cryled
http://www.physics-astronomy.com/2015/07/nasas-impossible-em-drive-works-german.html
======
Animats
This paper (non-paywall version)[1] is from last August.

It's another one of those phenomenon that's so near the noise threshold that
it's hard to measure reliably. They get forces around 70 μN. This is very
small, and although they have a balance sensitive enough to measure it, there
are lots of effects which can produce tiny forces like that.

The experimental work described in the paper is disappointing, in that the
original cavity system apparently had a Q of something like 100,000, but their
system only has a Q of 50, because it's mistuned for the microwave oven
magnetron they're using. ("Unfortunately, the absorption peak at the resonance
we were aiming at was smaller then expected (probably also due to
misalignments after soldering).") The highest thrust reported by anybody with
this is 720 mN, but that was in air. They're almost four orders of magnitude
below that, in vacuum. For reference, the ion thrusters on the Dawn spacecraft
deliver 90mN.

If they had hardware that generated 720mN in air, and tried that in hard
vacuum, that would be useful. (In air, all sorts of things, such as heating or
electrostatic repulsion, can generate air movement and thus tiny amounts of
thrust. So results in air are not too interesting.)

[1] [http://moscow.sci-
hub.bz/ded43880657f12f27fc596f46abbbfe6/10...](http://moscow.sci-
hub.bz/ded43880657f12f27fc596f46abbbfe6/10.2514@6.2015-4083.pdf)

------
cryled
Paper cited by article does not confirm it works: "Our test compaign therefore
cannnot confirm nor refute the claims of the EMDrive but intends to
independantly assess possible side-effects in the measurement methods used so
far"

[http://forum.nasaspaceflight.com/index.php?topic=38577.msg14...](http://forum.nasaspaceflight.com/index.php?topic=38577.msg1440938#msg1440938)

Wondering why didn't NASA send a EMDrive to space already and just see if it
works or not on real conditions instead of testing it on a laboratory?

~~~
ehnto
I imagine the cost coupled with the timeline of other experiments. It's
certainly not a trivial thing to do.

------
JamesGDev
Ok, so this article says:

> The EM drive is so thrilling because it yields enormous amounts of
> propulsion

Yet IFL-Science says:

> What it actually does is produce a tiny, tiny amount of thrust via a method
> that’s not entirely understood.

I know which one I trust.. Can this be down voted for not been factual.?

~~~
cryled
tiny, tiny amount of thrust during large, large amounts of time = enormous
amounts of propulsion...

I know article is awful, sorry about that; submited only just because I wanted
to read more comments about EMDrives on HN as I think they are cool; and the
way HN works old threads are never seen again by most users...

~~~
JamesGDev
haha, no need to apologise, this site is full of educated people who make up
their own mind. I think I snapped a little with my comment (mid way building
an iPhone App so stressed) Apologies.

------
cryled
[https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster](https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster)
[http://forum.nasaspaceflight.com/index.php?topic=39004.0](http://forum.nasaspaceflight.com/index.php?topic=39004.0)

------
roywiggins
A functioning massless drive is arguably as unlikely as a perpetual motion
machine.

It's not really worth paying attention to claims that someone built one other
than perhaps as entertainment value.

~~~
SAI_Peregrinus
It IS a perpetual motion machine.

Stick a few of them on a generator's rotor so that they'll spin it when
powered. Use the generated power to run them, and harvest the excess. Infinite
free energy!

------
xbmcuser

      Best way to test the engine is for Elon Musk to make one and send it up on his rocket if it works then he can bring his timeline for mars down a few years.

------
packetized
Can we get a [2015] tag?

------
snissn
Oh cool, another crack pot physics post on hacker news!

~~~
vixen99
If you have sure-fire evidence that this is indeed 'crackpot' then you should
bring it forward otherwise you're offering an opinion minus pertinent
observation or support. Perhaps I'm wrong but why should that be interesting
enough to post here? Most of the British newspapers including the Guardian and
Daily Mail provide an outlet for such comments.

------
JoeAltmaier
tl;dr: no it doesn't; no it wasn't

