Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1879757 times)

Offline Rodal

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I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?
Yes, along those lines, you have any answers on it? Does anything change if the frustum is filled? If so what percentages of change in thrust? What gas is used? What air pressures? Was the vacuum chamber slowly filled to ambient air pressures monitoring thrust? Did the thrust reappear when all else remained the same except the Vacuum chamber's air pressure?

Shell

speeeelingug

Many things are changed by a gas:  Ammonia was responsible for the first practical Maser, as Ammonia emits at ~24GHz

The microwaves can convert humid air into an ionized plasma.  Just wait until you take movies of what's happening inside: I will not be surprised at seeing evidence of ionized plasma.
« Last Edit: 07/25/2015 03:42 PM by Rodal »

Offline Rodal

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[...
<<I would think if the Drude model came from Meepers, the units, being normalized to u0 and e0, would be natural and not the problem. But I speak from ignorance I'm eager to relieve.>>

No, take a look at the Drude model, its properties are very dependent on frequency.  The Drude model constants available are for the optical range and wholly inapplicable to the 2.45 GHz range. The Drude model constants are not u0 and e0



This Drude model is in Frequency Domain (FD) and Meep's cavity simulation works in Time Domain (TD), then how a complex number apears in a TD simulation?

see:  http://www.fzu.cz/~dominecf/meep/data/meep-metals.pdf

http://www.fzu.cz/~dominecf/meep/

« Last Edit: 07/25/2015 03:58 PM by Rodal »

Offline SeeShells

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I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?
Yes, along those lines, you have any answers on it? Does anything change if the frustum is filled? If so what percentages of change in thrust? What gas is used? What air pressures? Was the vacuum chamber slowly filled to ambient air pressures monitoring thrust? Did the thrust reappear when all else remained the same except the Vacuum chamber's air pressure?

Shell

speeeelingug

Many things are changed by a gas:  Ammonia was responsible for the first practical Maser, as Ammonia emits at ~24GHz

The microwaves can convert humid air into an ionized plasma.  Just wait until you take movies of what's happening inside: I will not be surprise at seeing evidence of ionized plasma.
I know I'll see plasma discharges with the perforated copper and I have an idea at which points. As one friend said it will be like a Frustum Jack-o-Lantern. Video at 6 is the catch phrase.

I wish i had a vacuum chamber. I'd put my perforated copper frustum into it, evacuate the air and power it up, see low thrust numbers and then while it's operating fill the chamber.



Offline RonM

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

Offline birchoff

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

I thought we had observations showing that space is flat.

Offline Chrochne

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The latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.

By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?


Thanks and have a nice weekend because this Monday will really be interesting.

PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.

The wired article just says there is yet another theory about how the em-drive works.

http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission

That is interesting look into it Zen-In. I am also looking forward what do you think about the Tajmars results once they are available.

Offline SeeShells

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This is what I have and it's a little lacking, they needed to pressurize the chamber slowly and monitor thrust.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140009930.pdf
(For TT)
<quote>
During test run data takes at vacuum, the turbo pumps continue to run to maintain the hard vacuum environment. The high-frequency vibrations from the turbo pump have no noticeable effect on the testing seismic environment.
<end Quote>
<summary>
F. Tapered Cavity RF Evaluation, General Findings and Lessons Learned Overall, the biggest lesson learned was that RF tuning and optimization constraints are very challenging. We
discovered early in the COMSOLŪ analysis process that just because you can achieve a great RF solution does not mean that it will be an ideal Q-thruster implementation.
There appears to be a clear dependency between thrust magnitude and the presence of some sort of dielectric RF resonator in the thrust chamber. The geometry, location, and material properties of this resonator must be evaluated using numerous COMSOLŪ iterations to arrive at a viable thruster solution. We performed some very early
evaluations without the dielectric resonator (TE012 mode at 2168 MHz, with power levels up to ~30 watts) and measured no significant net thrust.
Numerous COMSOLŪ analysis runs also indicated a strong dependency between thrust magnitude and antenna type, location, orientation, and number of antenna feeds. Slight changes in antenna design and number of feeds changed the COMSOLŪ thrust prediction by a factor of three which forced our team to implement tighter configuration control protocols during testing to ensure close representation of as built hardware to the analyzed
configuration. <end>


Offline ScottD

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Hello everyone.  I've been lurking since the middle of Thread 2.  I would like to thank everyone that is striving to find out the truth of what is happening with this type of device.  The potential of what this could lead to is hard to really appreciate.

I certainly can't hope to keep up with the physicists, electrical engineers, and other theoreticians,  but maybe I can toss out some thoughts from time to time.

Here are some thoughts that I have been having:

1. I have read a good bit in the threads with people arguing about apparent violations of COM and COE by these devices (mostly based on people working up equations to support a theory).  Some of the devices being tested may be air tight.  They may act as, or be in, a Faraday cage.  But just because a system appears to be closed, does not mean that it is.  There may be energy/force transport mechanism that we don't yet recognize. 

2. The recent observation that when tested in air produced a certain amount of thrust, but when tested in a vacuum produced a much smaller amount of thrust is, as others have pointed out, very interesting.  If it produced no thrust in vacuum, then it would appear to be little more than an ion type fan.  But with there still being thrust in a vacuum seems to indicate that it isn't as simple as that.  There are three separate places in and around the Drive where air could have some impact. Inside the frustum; Outside the frustum but inside the body being "propelled"; and outside the body being "propelled". 

I suppose it could be possible that the air inside the frustum could be contributing to the propulsive effect along with the material of the frustum itself.  So, testing with a pressurized frustum with the rest of the system in an evacuated state makes sense to do.

The air outside the frustum but inside the body being propelled would likely have little if any impact on the propulsion.  Someone mentioned that magnetic fields from DC current could pass through the copper wall.  I don't see how that, interacting with the air outside the frustum, could do anything like produce the thrust that people seem to be seeing.

Anyway, thank you for taking the time to read my post.  You guys and gals are way ahead of me on the theoretical and practical sides of seeing this turned into something real.

Scott

Offline Rodal

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Hello everyone. ...
WELCOME to the thread and thanks for your great post :)

Online WarpTech

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

I thought we had observations showing that space is flat.

We have experiments that show there is thrust greater than that of a photon rocket, even in vacuum. I believe the thrust comes from a gradient, just like Newtonian gravity except that it is only acting over a very narrow bandwidth of the EM spectrum that is effected by the waveguide. It does not affect the full bandwidth of all sub-atomic particles as gravity would.

Consider this simple example. A straight waveguide has a frequency dependent group velocity, but at any constant frequency the group velocity is a constant. This means, that the wave and the waveguide are a relative inertial reference frame. When the waveguide is tapered, the group velocity is not constant anymore at any frequency. So this introduces an "accelerated reference frame", and per Einstein's Equivalence Principle, this is equivalent to a gravitational field acting over a narrow bandwidth of the EM spectrum. There is no question about this, it is a fact.
Todd

Offline SeeShells

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Hello everyone.  I've been lurking since the middle of Thread 2.  I would like to thank everyone that is striving to find out the truth of what is happening with this type of device.  The potential of what this could lead to is hard to really appreciate.

I certainly can't hope to keep up with the physicists, electrical engineers, and other theoreticians,  but maybe I can toss out some thoughts from time to time.

Here are some thoughts that I have been having:

1. I have read a good bit in the threads with people arguing about apparent violations of COM and COE by these devices (mostly based on people working up equations to support a theory).  Some of the devices being tested may be air tight.  They may act as, or be in, a Faraday cage.  But just because a system appears to be closed, does not mean that it is.  There may be energy/force transport mechanism that we don't yet recognize. 

2. The recent observation that when tested in air produced a certain amount of thrust, but when tested in a vacuum produced a much smaller amount of thrust is, as others have pointed out, very interesting.  If it produced no thrust in vacuum, then it would appear to be little more than an ion type fan.  But with there still being thrust in a vacuum seems to indicate that it isn't as simple as that.  There are three separate places in and around the Drive where air could have some impact. Inside the frustum; Outside the frustum but inside the body being "propelled"; and outside the body being "propelled". 

I suppose it could be possible that the air inside the frustum could be contributing to the propulsive effect along with the material of the frustum itself.  So, testing with a pressurized frustum with the rest of the system in an evacuated state makes sense to do.

The air outside the frustum but inside the body being propelled would likely have little if any impact on the propulsion.  Someone mentioned that magnetic fields from DC current could pass through the copper wall.  I don't see how that, interacting with the air outside the frustum, could do anything like produce the thrust that people seem to be seeing.

Anyway, thank you for taking the time to read my post.  You guys and gals are way ahead of me on the theoretical and practical sides of seeing this turned into something real.

Scott
Welcome Scott, good summary and good observations. That's a great skill to have and you have hit upon the points that we all are trying to address.

Shell

Offline Notsosureofit

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

I thought we had observations showing that space is flat.

We have experiments that show there is thrust greater than that of a photon rocket, even in vacuum. I believe the thrust comes from a gradient, just like Newtonian gravity except that it is only acting over a very narrow bandwidth of the EM spectrum that is effected by the waveguide. It does not affect the full bandwidth of all sub-atomic particles as gravity would.

Consider this simple example. A straight waveguide has a frequency dependent group velocity, but at any constant frequency the group velocity is a constant. This means, that the wave and the waveguide are a relative inertial reference frame. When the waveguide is tapered, the group velocity is not constant anymore at any frequency. So this introduces an "accelerated reference frame", and per Einstein's Equivalence Principle, this is equivalent to a gravitational field acting over a narrow bandwidth of the EM spectrum. There is no question about this, it is a fact.
Todd

By Jove !  I think you've got it !

Offline SeeShells

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

I thought we had observations showing that space is flat.

We have experiments that show there is thrust greater than that of a photon rocket, even in vacuum. I believe the thrust comes from a gradient, just like Newtonian gravity except that it is only acting over a very narrow bandwidth of the EM spectrum that is effected by the waveguide. It does not affect the full bandwidth of all sub-atomic particles as gravity would.

Consider this simple example. A straight waveguide has a frequency dependent group velocity, but at any constant frequency the group velocity is a constant. This means, that the wave and the waveguide are a relative inertial reference frame. When the waveguide is tapered, the group velocity is not constant anymore at any frequency. So this introduces an "accelerated reference frame", and per Einstein's Equivalence Principle, this is equivalent to a gravitational field acting over a narrow bandwidth of the EM spectrum. There is no question about this, it is a fact.
Todd
Like it.
I need to go out to the shop in a bit but let's add air to that thought is the air internally being effected as well? More mass=greater effects.
Shell

Online WarpTech

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Thrust To Power Derivation

I posted the attached derivation the other day. The only response was an off the cuff remark from @deltaMass. I guess what I'm looking for is some discussion on why this is wrong, or not. The algebra is correct, the interpretation is that as the Xmn "resonant" wave propagates down the expanding waveguide, the gradient enhances the thrust. I estimated using Wolfram Alpha's waveguide simulator (using 2 different size waveguides) that if the wavelength expansion follows the taper, and the frequency is very near the cut-off. The resulting thrust to power is several orders of magnitude greater than a photon rocket, over a short distance. If the waveguide is long, then it all reduces to 1/c at the far end. If there is no taper, it reduces to 1/v_phase. Taper adds a gradient that depends on the direction of the taper. In one direction it attenuates, in the other it accelerates.

Let me know what you think.
Todd

Offline deltaMass

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it can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.

Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower  Vacuum. ???
Using an RTG like Cassini's (250W, 50 Kg) and a 50 Kg drive (10-7 N/W) would get you to Pluto (6*1012 m) in 220 years.

Offline aero

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Quote
Yang          270,000 microNewtons for 300 watts inputPower  in Air
Shawyer    174,000 microNewtons for 400 watts inputPower  in Air
NASA                  55 microNewtons for    50 watts inputPower  in Air
We should add a line to this table

Photon Rocket    50 microNewtons for 15 kW in vacuum

Did Tajmar use 15 kW of input power, or is his result still better than a Photon Rocket?

And we should add another line, Completely sealed Photon Rocket -

Thrust = 0.000 microNewtons for infinite input power.

This is being overlooked when comparing all of these numbers, but if the cavity is sealed against radiation leakage, then classic physics guarantees zero thrust. Relativistic physics, a different story.
Retired, working interesting problems

Offline SeeShells

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Thrust To Power Derivation

I posted the attached derivation the other day. The only response was an off the cuff remark from @deltaMass. I guess what I'm looking for is some discussion on why this is wrong, or not. The algebra is correct, the interpretation is that as the Xmn "resonant" wave propagates down the expanding waveguide, the gradient enhances the thrust. I estimated using Wolfram Alpha's waveguide simulator (using 2 different size waveguides) that if the wavelength expansion follows the taper, and the frequency is very near the cut-off. The resulting thrust to power is several orders of magnitude greater than a photon rocket, over a short distance. If the waveguide is long, then it all reduces to 1/c at the far end. If there is no taper, it reduces to 1/v_phase. Taper adds a gradient that depends on the direction of the taper. In one direction it attenuates, in the other it accelerates.

Let me know what you think.
Todd
I think your ringing some bells here. But ELI5 why is this different Todd
.
http://www.microwaves101.com/encyclopedias/klopfenstein-taper

Off to the shop again, needed coffee again for some reason.

Shell

Offline demofsky

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I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?
Yes, along those lines, you have any answers on it? Does anything change if the frustum is filled? If so what percentages of change in thrust? What gas is used? What air pressures? Was the vacuum chamber slowly filled to ambient air pressures monitoring thrust? Did the thrust reappear when all else remained the same except the Vacuum chamber's air pressure?

Shell

speeeelingug

Many things are changed by a gas:  Ammonia was responsible for the first practical Maser, as Ammonia emits at ~24GHz

The microwaves can convert humid air into an ionized plasma.  Just wait until you take movies of what's happening inside: I will not be surprised at seeing evidence of ionized plasma.

This just reminded me: Those experimentalists using microwave magnetrons (which are tuned for water) and are not purged with something like nitrogen or a vacuum should keep track of the humidity.  This time of year especially there will be big differences between, say, North Carolina and Colorado.

I also would like to say that I like Rodal's idea of investigating whether creating essentially a maser like the baby EM drive filled with ammonia will enhance any thrust signals.  This really should be something that should be investigated at some point.  Admittedly, this will be tricky if non oxidized inner surfaces are required...

Offline rfmwguy

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This is a good news bad news article for sure. Without knowing the mechanical and electrical configuration, its hard to judge...

However, for a lab that is known for eliminating measurement "noise", this experiment appears to rise above it in a vacuum; meaning this is not a propellant force, it is a propellantless force.

The door has been cracked open. Maybe one of us can help walk through it...
Unfortunately the "noise" criticism will persist just as strongly, if the experiments to be reported by Tajmar are in the same status as a couple of months ago:  the experiments at that time showed approximately 60% different thrust force measurements when the EM Drive was physically rotated 180 degrees from the "forward" thrust tests to the "reverse" thrust tests.  Shouldn't the thrust be the same regardless of space orientation? 

Unless one can show a specific reason for this orientation-dependence, the critics (John Baez @ University of California, Riverside, Sean Carroll @ CalTech) will point out once again that this is indicative of an experimental artifact.

There are some skeptics that have asked for 4 sigma: Ha Ha Ha, that will be the day: 4 sigma is 99.993666% within the CI.  I consider 4 sigma to be absurd at this point of knowledge (just discussion of sigma presumes a Gaussian probability distribution: a distribution assumption which is completely baseless when discussing an experiment whose physical nature is under argument, and where the population of experimental results does not even justify a statistical frequentist analysis at this point :) ).  The probabilitty distribution shown by the experimenters right now (to the arguable extent that one can discuss a probability distribution with a population of only a dozen or so results is very, very fat-tailed).

But 60% difference in results arising from orientation dependence is easily going to be attacked as poor experimental corroboration by the skeptics.

And with Tajmar reporting thrust/InputPower thousands of times less than Shawyer/Yang and even less than what NASA reported, be prepared for XYCD to re-run their comic.

http://www.explainxkcd.com/wiki/index.php/1404:_Quantum_Vacuum_Virtual_Plasma

(XYCD has it wrong: nobody pumped 20 kilowatts into an EM Drive: NASA only pumped 50 Watts, and actually only 2.6 watts for the TE012 experiment that resulted in the greatest thrust/InputPower.)
Unless I am mistaken, there is only 1 recognized force (besides experimental error) that could account for variance due to orientation in a vacuum: Electromagnetism. Gravity as we understand it is not variable in a 360 degree horizontal rotation...Am I right on this assumption, Doc?

Offline deltaMass

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Classically there's a force on each endplate given by F = 2 P/v (use the v of your choice). So if you clamped one endplate+frustum and allowed the other (movable) endplate to express this force (a puzzle I'll leave to you mechanical engineers), at P=1.5 KW you'd expect ~10 uN (1mg-f). I'd have thought that was detectable.

Then repeat with the opposite endplate being movable. Subtract the two forces and Viola!

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