Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1801360 times)

Offline Paul Novy

  • Member
  • Posts: 12
  • Poland
  • Liked: 11
  • Likes Given: 3
I'm just gonna leave this here...

"Macroscopic and Direct Light Propulsion of Bulk Graphene Material"
http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf


Quote
The force generated from such a process/mechanism is much
larger than the force generated directly from the conventional light pressure, which is
much smaller than the force required to propel the samples.

Quote
The mechanism behind this novel phenomenon is believed to be an
efficient light-induced ejected electron emission process, following an Auger-like path
due to both the unique band structure of graphene and its macroscopic morphology of
this unique material.

Offline Star One

  • Senior Member
  • *****
  • Posts: 8013
  • UK
  • Liked: 1280
  • Likes Given: 168


so, no scat, there i was... I learned you can do stuff that violates the laws of physics so long as you label the process as happening in imaginary time even if it has real physical consequences.

http://phys.org/news/2015-05-physicists-quantum-tunneling-mystery.html

Synopsis: Massive things that quantum tunnel can violate the physical speed limit of light so long as there isn't anybody watching and there cannot be anyone watching because it happens in imaginary time.

I don't know about you; but i kind of had a different idea of what "imaginary" means but evidently imaginary does NOT mean unreal.

Isn't that the same thing as I just posted above but with a different spin, if you pardon the pun?

I saw someone suggesting & no idea if it's correct that this allows theoretical for greater than speed of light & teleportation?

It may just be the articles treatment of the underlying paper but but i do not take it as being the same thing as your post. But really a half a year  to  a year ago there were a couple of articles on entanglement and wormholes and gravity all being related in the manner you suggest. In my case the thing was quantum tunneling of a massive object being instantaneous and thus implying FTL travel albeit in "imaginary" time. :)

No wonder Einstein hated all this stuff, the concepts often seem so off the wall & hard to get your head around, even one of the greatest scientific minds seemed to be driven to distraction by them let alone poor old laypeople.

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
i just looked at a critique based on the bayes outlook of emdrive and i can only say...bayes theorem is the dumbest thing i have ever heard of in my life.  i understand the math just fine.  its just so hand wavy abd full of hot air that i cant take the critism seriously at all.
Let's consider that the person doing the critique admits up front that he has not investigated the EM Drive experimental data.  He mentions Bayes theorem in a superficial hand-wavy way in one of hundreds of blog pieces he wrote (he did not calculate the Bayes probability). Don't think that Bayes theorem is a dumb thing.  Bayes theorem can and has been used successfully for countless applications.  Its renaissance and re-adoption after WWII is due to its success in solving practical problems. 

« Last Edit: 05/28/2015 10:29 AM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
From which we conclude, because 0 <= Df <= 1, that
0 <= F <= 2 Q P/c , where F is the thrust.

So with Df = 1 and even if Q =1, F is twice that which would be delivered by a photon rocket at power P. Sound right to you?
This is a case of having to mind your Q's so to speak.  :)

There is no critical signifcance for the value of Q=1 that you chose, to question  that there is something inherently wrong.  Q=1 is an arbitrary, underdamped value of Q.

A casual reader may think that a photon rocket has Q=1, and therefore you have proven something significant.

That's not the case.

A photon rocket is an open chamber. Not a resonating cavity. 

Still if you want to force a comparison with a photon rocket, somehow, then you are off by a factor of 2.

(Instead of the value of Q=1 arbitrarily chosen in your example), the value of Q= has important signficance: it is a critically damped quality factor. Like an overdamped system, the output does not oscillate, and does not overshoot its steady-state output (i.e., it approaches a steady-state asymptote). Like an underdamped response, the output of such a system responds quickly to a unit step input. Critical damping results in the fastest response (approach to the final value) possible without overshoot.

For Q= , and Df=1, Shawyer's expression gives the thrust of a photon rocket.



« Last Edit: 05/28/2015 01:41 PM by Rodal »

Offline vulture4

  • Full Member
  • ****
  • Posts: 987
  • Liked: 305
  • Likes Given: 89
In the Chinese devices, the test device movement is horizontal, so external rising hot air and internal buoyancy effects of heated air should have little effect on horizontal thrust.
More than half a century ago I played with a child's toy called a Crooks radiometer, in which a small pinwheel with vanes that are black on one side and white on the other is mounted in a glass bulb under a near (but not total) vacuum. https://en.wikipedia.org/wiki/Radiometer
In sunlight the dark side of each vane becomes warmer than the light side, and imparts a higher thermal recoil to air molecules that contact it, producing a dramatically unbalanced horizontal force that spins the pinwheel. A related device called the Nichols radiometer compensates for molecular effects and measures the actual radiation pressure of incident photons on a silvered vane. https://en.wikipedia.org/wiki/Nichols_radiometer Similarly, the anomalous acceleration of the Pioneer probes as they departed from the solar system, at one time felt to indicate a "new physics" effect, was eventually concluded to be thermal recoil produced by the emission of infrared photons from the warmer parts of the spacecraft due to the asymmetric heating produced by the nuclear power source. https://en.wikipedia.org/wiki/Pioneer_anomaly  Finally, as you suggest, thermal convection can also produce forces on a heated object.

So I think it can be fairly said that horizontal or vertical forces as great or greater than those reported can easily occur due to thermal effects. Moreover, the presence of such confounding factors is the rule rather than the exception in physics. That is why theory must come first in physics. For example, the static Casimir effect was recently measured in a laboratory, but the theory underlying the effect had already been so well established that the experiment was considered simply a demonstration of what was already known, and was precisely consistent with the predictions of theory.

In the case of the frustum resonator, the principle that is proposed is that the group velocity of photons reflected from the small end of the resonator is lower than those reflected from the large end. It is conceivable to me that the group velocity of the photons in the resonator could increase as they progress along its axis towards the large end. http://www.microwaves101.com/encyclopedias/waveguide-mathematics  I think the relevant question that has not been answered is how these photons could be accelerated without exchanging momentum with some element of the surrounding medium, which would of course counterbalance the excess force imparted by their reflection from the end of the chamber. The "reactionless drive" that must be explained theoretically by the investigators is the proposed reactionless acceleration and deceleration of these photons.
« Last Edit: 05/28/2015 10:38 AM by vulture4 »

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
The problem is that if you talk about "accelerating" or "decelerating" photons when there is no change in refractive index in play, you will be dismissed peremptorily by physicists.

Offline vulture4

  • Full Member
  • ****
  • Posts: 987
  • Liked: 305
  • Likes Given: 89
The problem is that if you talk about "accelerating" or "decelerating" photons when there is no change in refractive index in play, you will be dismissed peremptorily by physicists.
A waveguide is very similar to a lens in this regard, indeed one could consider the equivalent case of light resonating between two mirrors at the ends of a tube floating in space. Place a planar piece of glass in contact with one of the mirrors and the group velocity, and hence momentum, of the photons reflecting off that mirror will be reduced. Will this create an unbalanced force and subject the optical waveguide to reactionless acceleration? Probably not as there will likely be an opposite exchange of momentum between the light and the dielectric glass.

Offline Chris Bergin


Please check with NSF site administrators, as I am not familiar with the latest rules on creating new threads.  The only thread I introduced at NSF was this 3rd thread as Chris warned that he had to close the 2nd thread because it was too long. :)


Yeah, I think we have a pretty decent set up for this here and we're good as-is.

Remember, this is really on the edge (and falling off the edge) of what we cover here as a site and it was nearly aborted after thread one turned a bit wacky.

It became interesting when NASA folks and clearly very clever folk started posting updates and progress in Thread 2 - which went mini-viral and turned into that very heavily read thread. Given this site covers what people find interesting, we made the jump to run an article on it (noting other sites had already). Given we're a pretty big site per space flighty things, that was picked up by the mass media and it went properly viral.

Now there's a cost to that. 1) You lose context as mass media go for an angle and the angle was warp drive. 2) You get so many new people running into the site and waving their arms in the air saying "this is nonsense" or "OMG! Amazing" (both being the wrong end of the stick for a valuable discussion). 3) It can cause too much attention and scare some good folk away, 4) The subject becomes very busy it's a battle to keep the noise down (but we are attempting that, per the foundation of the site rules. It'll annoy some people, but it's something we've always done. It's never personal, it's housekeeping).

Thankfully the surge didn't create too many issues. We didn't get too many armwavers and we gained a few good members who are the ones who always stick around after the storm clears. So that's where we're at right now.

As such, Thread 3 should improve as a general discussion thread (it's been calming down nicely over recent days). We would like a new thread for updates, per how Thread 2 mainly was, but that'll depend on when there are new updates. I envision by the end of the year we'll be back into the Thread 2 type scenario.

We also have the Entry Level thread as a relief valve and Traveller has his poll thread for "what do you think?" posts.

So I think we're good right now.

Offline Flyby

  • Full Member
  • ***
  • Posts: 382
  • Belgium
  • Liked: 447
  • Likes Given: 47
The 3 EMdrive threads together (not counting the side topics) have a whopping 1416992 views.... :o

Offline StrongGR

This was a thought occurring me a moment ago. I have just shown that inside these cavities there is a tiny gravitational effect. Per se this effect is too small account for the observed thrust, if confirmed. But, is there any change in the light propagation inside such cavities causing an asymmetry due to these small gravitational effects?

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
Two comments: a) nothing here is worth more than 2 or 3 digits of precision, and b) Df does serve at least the purpose of bounding the thrust from above at the limiting value given by Df = 1.

Calculating Shawyer Demonstrator Df.

Shawyer's thrust equation T = (2 * Df * Po * Q) / c gives us the ability to calc Df, knowing Q, T & Po as Df = (c * T) / (2 * Po * Q)

Demonstrator EM Drive, published data:

Q: 45,000
Po: 334W
T: 0.096N

Therefore Df = 0.95714. This suggests Shawyer's reported Df of 0.844 is correct as effective Q at measured power may not be 45,000 due to thermal detuning or the magnetron frequency not being at cavity resonance.

When calculating the small end diameter, we must know the TEm,n or TMm,n excitation mode as the cutoff wavelength can vary quite a lot, which effects guide wavelengths Lambda g1 and Lambda g2 and thus Df. As we don't the mode, we must assume the Df of 0.844 is the correct value. A bit of playing with modes and trying different small end values may reveal the mode and true small end size.

Have fun.

The value of Df = 0.95714 is so close to 1 and so much higher than the Design Factor for the Experimental (Df=0.48), that is suspect.  Let's take a closer look at the data for the Demonstrator.

Shawyer's papers show that instead of a single value of power, he run multiple cases for the Demonstrator, from 421 W to 1200 W, so what makes sense to use to figure out a Design Factor based on experiments is the full range of what he measured.  When one does that, the Design Factor ranges from a minimum of 0.284 to a maximum of 0.809.  Therefore the mean value of the Design Factor is around 0.5 which is close to what phaseshift calculates based on the photograph of the Demo.

Here is a Table of Design Factors based on experimental values (from data in  http://emdrive.echothis.com/Experimental_Results based on his papers):

using Df = (c * Force ) / (2 * Power * Q)  and c= 299705000 m/s (speed of light in air)


Description                     Power (W)     Q      Force (mN)   Df (from Exp.)   
Shawyer Experimental   850            5900      16              0.478
Shawyer Demo          421-1200   45000   102.30         0.809-0.284      
Brady a TM Mode          16.9             7320      0.0912      0.110
Brady b TM Mode         16.7             18100   0.0501        0.025
Brady c TE Mode           2.6             22000   0.05541       0.145

Notice that the Design Factor calculated from experimental values for the Experimental (0.478) is within 1% of the Design Factor (0.484)  based on the geometry of the Experimental, using for cut-off frequency the lowest possible natural frequency (much lower than what the Experimental was tested at). Therefore it would be illogical to use a different method to calculate cut-off frequency for the Design Factor in the Experimental than for the Demo.

Notice the extremely small values of the Design Factor for the NASA Eagleworks experiments.  They cannot be explained in terms of geometry or in terms of cut-off frequency.
« Last Edit: 05/28/2015 01:48 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
For the Eagleworks team: do you report the net RF power entering the resonator (forward - reflected at feedpoint)?  Or total PA output?

For example in this picture ~50w is listed:



I think that Paul March answered this question at previous NSF threads already: the RF power numbers they give are forward minus reflected equal net power flow into the test article. 
« Last Edit: 05/28/2015 12:59 PM by Rodal »

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2409
  • Claremore, Ok.
  • Liked: 374
  • Likes Given: 10
@Rodal

Apologies, but I thought that there'd already been some tests done in a vacume chamber with this device while still producing apparent thrust.  Was I mistaken on this?

If not, I would think that heated air convection would no longer be considered a potential factor in this device.
My God!  It's full of universes!

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
@Rodal

Apologies, but I thought that there'd already been some tests done in a vacume chamber with this device while still producing apparent thrust.  Was I mistaken on this?

If not, I would think that heated air convection would no longer be considered a potential factor in this device.
The only organization, to my knowledge, that has reported tests in vacuum is NASA Eagleworks.

Although Shawyer has been reporting tests for about 15 years and NPWU in China for several years, they have not reported tests in vacuum, to my knowledge.

Since the tests results by NASA in vacuum were lower than the test results in air, it very much looks like the hypothesis that there is a significant thermal "gas effect" component involved in the tests is very much still alive, particularly when considering the much higher power used by Shawyer and NPWU in China.

There is noting I have seen from the researchers that quantifies the size of this "gas effect" in the experiments conducted in air in the UK and China.  Moreover, none of these tests have been conducted with a mesh for the ends, which is the only way that Cullen (who Shawyer uses as his main reference) found to eliminate the gas effect when performing tests in air in his 1951 Ph.D. thesis (the first time that anyone was able to quantitatively measure radiation pressure due to microwaves).

That a significant gas effect component is present would not be surprising as it has been known since Maxwell in the 1870's that scientists trying to measure radiation pressure (at microwave and higher frequencies) have had to deal with such problems for over 100 years (these problems are collectively known as "the gas effect").
« Last Edit: 05/28/2015 01:39 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
I...
Point well taken.

It would be very useful to get strong skeptical reviews of Prof.Yang's paper ((translated) page 4 ( http://www.emdrive.com/NWPU2010translation.pdf  ) concerning her equations stating that having a gas/fluid with charged particles inside the EM Drive results in transfer of its momentum to the EM Drive metallic body. 
...

I was under the impression that Yang had built an EM drive and had done a series of experiments that showed it could produce a mN thrust.   There is no mention of any experiments or measurements in the above translated paper.   I'll have to tip my hat to whoever translated it.   A well done job.

So this is the problem I have with believing the EM-drive is not a hoax; or stated more politely a case of mistaken measurements.    In thread 2 I stated the EW thrust signatures were not consistent with the known step response of their torque pendulum.   The calibration pulse, generated by a capacitive device, always produced an underdamped response (thrust graph).   This is the response that anything that pushes on the cavity should produce.   If a moth flew at the cavity, this same step response would be seen.   This is an immutable physical observation of mechanical systems.  They all have a natural frequency and a damping coefficient.   Any perturbation will exhibit the same step response.    However the EW thrust signatures when the RF power was turned on were completely different.   From this observation it can be concluded the RF power is not producing thrust.   

Others have offered alternative explanations for the apparent movement when RF power is applied.   Since we are talking about only 4-5 microns of apparent movement there can be many alternative, conventional explanations.

All the essays describing these experiments (EW, Shawyer, and now Yang) make a lot of claims but show very little data.    Shawyer has been doing this since 2003 and yet his raw data has never been released.   EW has released a few graphs but one can assume that given the amount of time they have been experimenting there is a lot more data.   So have they cherry-picked the data and just shown us the graphs that appear to show thrust?   If so that would indicate a very low percentage of possibly "good" tests.

In Monday's new York Times (pages A1, A11  "Maligned study..") there is a piece on a paper that the journal Science is considering retracting.   One of the authors has his hopes set on a "dream job" as a professor at Princeton.  However his faculty  advisor has asked Science to retract the paper because the author "... had misrepresented his study methods and lacked the evidence to back up his findings."  (quoted from NYT article)  The author was asked several times to make his raw data available in case his work needed to be checked, but never did.

It is one thing to say you have a propellantless microwave thruster and that in a few years cars will be flying but if there is no data to support these claims any sane individual would have to say it has all been a hoax.

So to all you DIY'ers out there: Don't electrocute yourself or give yourself cataracts, etc., chasing a dream that will never materialize.
Can you please link to the message where you  "In thread 2 stated the EW thrust signatures were not consistent with the known step response of their torque pendulum. " or otherwise describe what thrust signatures are not consistent with the step response of the torque pendulum?

Are you stating that none of the Brady et al thrust signatures are consistent with the torque pendulum response?

I recall that the Autocorrelation and Power Spectral Density analysis I did of a few Brady et.al graphs were consistent with the torque pendulum (I only did a few ones, for which frobnicat gave numerical data), I also modeled the torque pendulum differential equation with Mathematica.

The main difference I remember was not one of not being underdamped, but as frobnicat pointed out, the period of the response was behaving as if the system had a different stiffness than expected.

There is an issue with the inclination of the setup, as pointed out by frobnicat. Also, there is definitely a big  issue with turning the EM Drive around by 180 degrees and getting a significant different measurement.
« Last Edit: 05/28/2015 02:09 PM by Rodal »

Offline TheTraveller

Have asked Roger Shawyer to confirm the quoted Df for the Demonstrator EMDrive is 0.844:

http://emdrive.com/demonstratorengine.html
« Last Edit: 05/28/2015 02:24 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5259
Have asked Roger Shawyer to confirm the quoted Df for the Demonstrator EMDrive is 0.844:

http://emdrive.com/demonstratorengine.html
Can you please ask for him to check his original data documents (rather than his published papers) , and re-calculate the Design Factor based on known geometry, to make sure that there was not an unintended typo somewhere?
« Last Edit: 05/28/2015 02:36 PM by Rodal »

Offline TheTraveller

Have asked Roger Shawyer to confirm the quoted Df for the Demonstrator EMDrive is 0.844:

http://emdrive.com/demonstratorengine.html
Can you please ask for him to check his original data documents (rather than his published papers) , and re-calculate the Design Factor based on known geometry, to make sure that there was not an unintended typo somewhere?

From work on my spreadsheet, that can easily adopt to various TMm,n and TEm,n modes, I believe it is possible to get an excitation mode that will deliver a high Df, small end operating just above cutoff (as Shawyer recommends), without using stupid geometry.

Did ask for the excitation mode. If he shares that, will be able to plug it into my spreadsheet and see what it says about small diameter.

The more I work with my spreadsheet, the more I get a good gut feeling about how the 3 dimensions, excitation mode and external Rf frequency interplay with each other to get an optimal mix of all 5 variables for max thrust per applied power.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

Slide 4, attached, of the attached larger presentation, dealing with why side wall thrust versus small end plate thrust is not a linear function is interesting.

Helps to explain why the small end plate should operate just above cutoff for highest Df and thrust. Different excitation modes will give different cutoff for a fixed size end plate. So selecting excitation mode is as much a part of EM Drive design to get optimal thrust as are the other 4 variables of external Rf frequency, big & small end plate diameters and end plate separation, which also indirectly involves slant angle and side wall force as a component of overall small end dynamics.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline OttO

  • Member
  • Posts: 81
  • France
  • Liked: 91
  • Likes Given: 11
is there any change in the light propagation inside such cavities causing an asymmetry due to these small gravitational effects?

And we know there is an asymetry of internal infra red light.

Tags: