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Is EmDrive actually just gibberish?

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Ash Small

Thu Nov 19 2015, 11:17PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I doubt solar panels or conventional ion drives would last anywhere near the times required to travel any 'significant' distance in space.

Something like the proposed waveguide device might stand a better chance of surviving the trip?

Dr. Slack

Fri Nov 20 2015, 10:46AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Ash Small wrote ...

I doubt solar panels or conventional ion drives would last anywhere near the times required to travel any 'significant' distance in space.

Something like the proposed waveguide device might stand a better chance of surviving the trip?

I could make the argument that a concrete block stands a better chance of the surviving the trip than a momentum-ejecting rocket for which we understand the mechanism of operation, and can build. I've yet to see any evidence that an EM drive works better than a warm concrete block, or even theories that are consistent with known science for how it might.

Ash Small

Fri Nov 20 2015, 01:24PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I agree that the results are so far inconclusive

BigBad

Sat Nov 21 2015, 03:28AM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Posts: 600

Dr. Slack wrote ...

I could make the argument that a concrete block stands a better chance of the surviving the trip than a momentum-ejecting rocket for which we understand the mechanism of operation, and can build. I've yet to see any evidence that an EM drive works better than a warm concrete block, or even theories that are consistent with known science for how it might.

lol, and it's only funny because it's true.

DekuTree64

Mon Nov 21 2016, 10:05AM

Registered Member #54596 Joined: Fri Mar 06 2015, 11:31AM
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Peer reviewed study has been published: http://arc.aiaa.org/doi/10.2514/1.B36120
Apparently it produces 1.2 mN per kW. Two orders of magnitude greater than a photon rocket, and only one order of magnitude less than a propellant-consuming ion thruster. Pretty exciting!

nzoomed

Fri Nov 25 2016, 05:11AM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Well we may have to rewrite the laws of physics.
It appears NASA have tested it and have concluded it actually it works, but now they are trying to explain how it works!

Something that was once considered pseudo-science is no more, watch this space!

Patrick

Fri Nov 25 2016, 07:29AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Dr. Slack wrote ...

Mechanism creep is a sure sign of dodgy methodology.

This is well said, and should be in a college textbook.

Uspring

Fri Nov 25 2016, 02:32PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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If this device does not violate momentum conservation, it must push on something. This might be another object in the lab, which makes it unsuitable for a drive operating in space. Or it must emit some sort of particles, e.g. photons, which would just constitute some sort of standard EM drive or some other particles. If there are some other particles, these particles must be quite heavy, otherwise the thrust would be very weak, as is the case for photons. What kind of particles that might be, is unknown and there are no candidates.

But lets assume that these particles exist. Then there would be a mass loss on the drive similar to that of an ion drive or a typical rocket engine. For long term propulsion, that is a problem.

Now lets assume that the device violates momentum conservation. Momentum conservation is deeply linked to energy conservation. It is possible to build a not energy conserving machine from a not momentum conserving device. That puts us in the domain of perpetuum mobiles.

Not likely.

Dr. Slack

Fri Nov 25 2016, 04:24PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

At least this latest experiment is looking serious. They have made some good attempts to address spurious influences. No flexing cables to disturb the balance, as contacts were made through liquid metal, and an account has been taken of thermal effects. A calibration measurement before and after the thrust measurement.

These are their results, measured torque versus power.

There is certainly something going on.

I am concerned however about the variation in measured torque, especially at the 60W mark. There is not only a 3:1 variation, it's also an order of magnitude larger than their error bars. This means that something is very poorly controlled in the experimental setup, something is not reproducible.

Their calibration measurements on their torque beam are worth discussion. They are very consistent. This is good in the sense that it shows the setup is measuring the calibration torque well. This further highlights the fact that while the torque measurement system is working well to the calibration torque, it is still producing very variable device under test torques.

If the message of this paper is that we should accept the EMdrive proposal because no other explanation is available for the observed torque, then this falls far short of establishing that. While the paper does discuss other effects, I do not think that electrical effects between torque beam and chamber have been investigated sufficiently well. Extraordinary claims require extraordinary evidence, and I don't think this meets my threshhold yet.

My stance up to now has been that there is no point to performing the experiments because the theory was nonsense and experiments so far had been laughable. However, with these results, I would like to see more and better experiments, to answer the questions raised by this one. The main one in my mind is 'what is causing the wide spread of measurement results?'

I have some suggestions for the next experiments. Perhaps using the electrostatic torquer closed loop to eliminate the response time of the torsion beam, and certainly as the paper suggests better control of the thermal effects. The chamber wall proximity effects have been discussed, and they would like to move to a larger chamber. Further runs may be possible with this small chamber, using moveable baffles driven by stepper motors, which would allow 'walls' to be moved nearer to the device under test, to see if effects varied with distance.

If they're getting supposedly measurable results with only 80 watts, I wonder what the budget and enthusiasm would be for flying a test satellite equipped with this, a photon engine and an ion thruster, with ranging corner cube reflectors to allow precise orbit determination, to compare deltaVs for all three engines?

New Scientist's impeccable journalism strikes again. They had an article of about 8 column-inches in this week's issue, mentioned NASA, but said absolutely nothing of any meaning, neither referring to nor linking to their report.

Carbon_Rod

Sat Nov 26 2016, 06:54AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Also tried to find a detailed photo of the apparatus with little success.

1.
I was curious if the trials were repeated after rotating the entire rig 90' within the earth's magnetic field.
i.e. their calculations should remain constant if not a confounding variable.

2.
If one can measure the near-field RF radiation pattern (< 1 lambda) to see if it had opportunity to couple to metal objects in the test chamber, and not the emitter probe wave guide.

3.
Overlooked something trivial like:

Although, the phenomena may still upset those emotionally invested in contradicting legacy aether theories.
I'll safely wager it will not work outside a test chamber in space...

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