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EmDrive: Jesus What a Day

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Over the past month, two* DIYers have produced positive test results showing thrust from an EmDrive.

* There is a story.

The EmDrive is an electromagnetic device which NASA, along with researcher in Germany, Russia and China have detect anomalous thrust.  Nobody is clear why this is happening, though the German test did attempt to eliminate all the obvious sources of error.  Theories range from some kind of interaction with the earths magnetic field to creation of a zone of negative energy (unlikely).  

Measurements to date have been for very small amounts of thrust.  Some theories predict that the effect might scale up to something observable at around 700 watts - 1 kilowatt.  Among others, this caused several retired electrical engineers on reddit/the NASA spaceflight forums -- among others -- to conclude that we might not know what is going on but if it can be specced they can engineer it to within an inch of its life.

The first positive test came from a high school student who won South Africa's national science fair by testing a version of the device showing thrust.  I tend to think this is the most important of the two experiments.  The competition means that neutral observers where looking over the experiment and confirming that their actually was data.  The data might be the result of an experimental error but it is not being flatly falsified.  Results are here Reddit

Today one of the engineers from the NASA forum tested his prototype.  A video walk through of the test rig can be found here.  Basically the drive is hanging off one end of a long wooden beam with a laser pointer on the other end.  The pointer hits bounces off a mirror and hits a target on the other side of the test area.  This allows for the detection of very small forces without the need to use of scale with metal part (which the device might somehow throw off).  Unlike other devices, it uses a large amount of mesh.  This is meant to let heated air escape and make the test device safer to work around.

Rmfguy, the redditor testing the device did not expect it to work.  In the last couple of days modeling on NASA space flight, with the input of one of the verified Ph.D's in physics on the forum, indicated that microwaves would have to be fed in from near the large base to produce any effect.  This might indicate an effect that could possibly be explained by standard physics, and probably would not result in a space drive.  A result from an rf feed near the small base would indicate new physics.  

Rmfguy's feed was near the small base (done before the recent computer modeling).  He figured the thing was probably going to brick.  If it did work he expected the thrust to be in a down direction, pushing his laser pointer up.  Rmfguy tested the device and dutifully reported a null result, posting video of the test here: Youtube.

Here's the thing.  Each device consistently generates thrust in one direction.  Different versions of the device have shown thrust toward the small or large end.  No we don't know why.  We suspect it has something to do with the way the devices are built (and yes, it does cause many researcher to suspect that entire thing is some kind of very hard to detect error in the measuring equipment).

Rmfguy sat in a darkened room expecting either nothing to happen or the laser to rise on the target.  A couple hours after the video was posted, reader on reddit started commenting that the laser seemed to be dropping, moving in the opposite direction from what he expected, so slowly that you had to jump around in the video to see it happen.

Here's some pictures.  The first in the series is before anything is done.  The second is when a 20 mg weight is put on the drive to calibrate the experiment (laser moves up but not by much).  The third is the rig returning to its original position once the weight is taken off.  The fourth is at the end of 100% power test.

What's happening?  I don't have the slightest.  Since the thing had a wire mesh on top, I'm fairly certain it isn't lift from hot air.  What happens next?  I suspect it involves a lot of moving around rf feed locations and attempting to find ways to account for various sources of error.  

Tonight I feel like we are all the person sitting in the dark room trying to figure out what is going on.

Might I make a suggestion.  If Russia and China are working on this maybe its worth the price of a cruise missile to make sure we understand what is actually going on here.


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