Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1872054 times)

Offline tchernik

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Hey everyone,

Here is a summary of our current experimental design.
Any feedback is welcome and appreciated.  :)

Kurt

Best of luck in your experiments!

Offline phaseshift

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Short snippet of Ruby code that computes the Shawyer Design Factor the way TheTraveller has in his spreadsheet.

def compute_design_factor( small_diameter_meters, large_diameter_meters, frequency_hz, jC)
   
    cM = 299705000.0
    cf = cM / frequency_hz
    jCFPI = jC * cf / Math::PI
 
    b = Math.sqrt( 1 - ( jCFPI / large_diameter_meters ) ** 2 )   
    s = Math.sqrt( 1 - ( jCFPI / small_diameter_meters ) ** 2 )
   
    df = (b - s) / ( 1 - b * s )
   
    return df
   
end

jC = BesselJ Cutoff
« Last Edit: 06/01/2015 06:38 PM by phaseshift »
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline X_RaY

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@Hackaday "babyEMdrive"

I have got a look at a similar radarmodul like the guy with the "babyEM-Drive" is be using. I think its the same productfamily. The P_out  is only +10dBm (10mW) with a transmit frequency somewhere in the ISM band of 24ghz. Like i post yesterday there is no isolator in the circuit.  Based on own RF experience i dont think its generating measureable acceleration. Hope i am wrong. Nevertheless it could be interesting to see the results if he is done.

Most important: people still developing and learning! :)
« Last Edit: 06/01/2015 07:46 PM by X_RaY »

Offline WarpTech

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Hey everyone,

Here is a summary of our current experimental design.
Any feedback is welcome and appreciated.  :)

Kurt

Nice job. Can't wait to see the results!

Offline rfmwguy

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Spurious thoughts and ideas for those considering home (not lab) experimentation...The frustum effect theoretically can be tested a low power levels (see the 25 GHz experiment at just a few milliwatts). My suggestion, and likely my route, will not use 2.45 GHz magnetrons for safety reasons and cabling issues.

I'll likely turn to the other large marketplace for 2.4 GHz products...wifi/wlan (802.11b/g).  wifi home routers are about 40 mWatts or so with outboard amps that can take that to about 5 watts. Signal sources for a few dozen mWatts (don't have to be wifi only) are all over the place: http://www.mr-lee-catcam.de/pe_cc_i10.htm with 3W amps here: http://amzn.com/B00BX9YZI0 (bidirectional operation is not required for non-wifi use) There are many more out there, so don't stop here.

Other than safety, weight measurements will be easier. Lower power test units can be battery operated, avoiding the need for cable routing, potentially skewing weight measurements. IOW, a frustum and signal source can be built and self contained, no strings, er ah, cables attached.

Just a thought for home workshop folks. Be safe out there.


Offline Rodal

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Spurious thoughts and ideas for those considering home (not lab) experimentation...The frustum effect theoretically can be tested a low power levels (see the 25 GHz experiment at just a few milliwatts). My suggestion, and likely my route, will not use 2.45 GHz magnetrons for safety reasons and cabling issues.

I'll likely turn to the other large marketplace for 2.4 GHz products...wifi/wlan (802.11b/g).  wifi home routers are about 40 mWatts or so with outboard amps that can take that to about 5 watts. Signal sources for a few dozen mWatts (don't have to be wifi only) are all over the place: http://www.mr-lee-catcam.de/pe_cc_i10.htm with 3W amps here: http://amzn.com/B00BX9YZI0 (bidirectional operation is not required for non-wifi use) There are many more out there, so don't stop here.

Other than safety, weight measurements will be easier. Lower power test units can be battery operated, avoiding the need for cable routing, potentially skewing weight measurements. IOW, a frustum and signal source can be built and self contained, no strings, er ah, cables attached.

Just a thought for home workshop folks. Be safe out there.
I think it is great that people like you, Notsosureofit and Paul Kocyla/Jo Hinchliffe are looking/working on miniaturizing the EM Drive.  There is higher risk that it won't work of course (as compared to a replication), but if it does you will have opened a very exciting future to this technology, and the next step (up in a CubeSat) will be all the much easier to accomplish!   :)
« Last Edit: 06/01/2015 08:18 PM by Rodal »

Offline WarpTech

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Spurious thoughts and ideas for those considering home (not lab) experimentation...The frustum effect theoretically can be tested a low power levels (see the 25 GHz experiment at just a few milliwatts). My suggestion, and likely my route, will not use 2.45 GHz magnetrons for safety reasons and cabling issues.

I'll likely turn to the other large marketplace for 2.4 GHz products...wifi/wlan (802.11b/g).  wifi home routers are about 40 mWatts or so with outboard amps that can take that to about 5 watts. Signal sources for a few dozen mWatts (don't have to be wifi only) are all over the place: http://www.mr-lee-catcam.de/pe_cc_i10.htm with 3W amps here: http://amzn.com/B00BX9YZI0 (bidirectional operation is not required for non-wifi use) There are many more out there, so don't stop here.

Other than safety, weight measurements will be easier. Lower power test units can be battery operated, avoiding the need for cable routing, potentially skewing weight measurements. IOW, a frustum and signal source can be built and self contained, no strings, er ah, cables attached.

Just a thought for home workshop folks. Be safe out there.

A word of caution to those trying to use these low, low power sources. If the losses of the cavity outweigh the supply, then the Q = 0, since no energy can be stored. So you really need a feel for what the cavity losses will be before you can propose using such a small input source. If all the input power is dissipated in 1 cycle, there is nothing left over to amplify.

Todd



Offline TheTraveller

Short snippet of Ruby code that computes the Shawyer Design Factor the way TheTraveller has in his spreadsheet.

def compute_design_factor( small_diameter_meters, large_diameter_meters, frequency_hz, jC)
   
    cM = 299705000.0
    cf = cM / frequency_hz
    jCFPI = jC * cf / Math::PI
 
    b = Math.sqrt( 1 - ( jCFPI / large_diameter_meters ) ** 2 )   
    s = Math.sqrt( 1 - ( jCFPI / small_diameter_meters ) ** 2 )
   
    df = (b - s) / ( 1 - b * s )
   
    return df
   
end

jC = BesselJ Cutoff

Before doing Df or resonance calc you need to know excitation mode TMm,n,p or TEm,n,p and the appropriate BesselJ value as per that mode. BesselJ value is driven by mode TE or TM and the associated m & n values.  p refers to the number of 1/2 waves between the end plates.

There are 2 tables provided. One for TE mode and one for TM mode. Each is indexed by the selected m & n values.

As example to use TE013 mode, use the TE table and the value at the intersection of the m=0 & n=1. = 3.8318  Then adjust end plate spacing or frequency or Df, via altering either/both end plate diameters to fit the desired number of p 1/2 waves between the end plates.

Tables attached.
« Last Edit: 06/01/2015 09:32 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 rfmwguy

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(...)

A word of caution to those trying to use these low, low power sources. If the losses of the cavity outweigh the supply, then the Q = 0, since no energy can be stored. So you really need a feel for what the cavity losses will be before you can propose using such a small input source. If all the input power is dissipated in 1 cycle, there is nothing left over to amplify.

Todd

Agreed, this is the primary reason I decided against dielectric materials. "Electric losses in such cavities are almost exclusively due to currents flowing in cavity walls. " http://en.wikipedia.org/wiki/Microwave_cavity (and many other sources), so unless I'm missing something, copper is the way to go since oxidation (resistance) over time is not a concern. I'm also going to avoid tuning plates so as not to introduce any potential mechanically caused resistances...my head on straight?

Offline TheTraveller

(...)

A word of caution to those trying to use these low, low power sources. If the losses of the cavity outweigh the supply, then the Q = 0, since no energy can be stored. So you really need a feel for what the cavity losses will be before you can propose using such a small input source. If all the input power is dissipated in 1 cycle, there is nothing left over to amplify.

Todd

Agreed, this is the primary reason I decided against dielectric materials. "Electric losses in such cavities are almost exclusively due to currents flowing in cavity walls. " http://en.wikipedia.org/wiki/Microwave_cavity (and many other sources), so unless I'm missing something, copper is the way to go since oxidation (resistance) over time is not a concern. I'm also going to avoid tuning plates so as not to introduce any potential mechanically caused resistances...my head on straight?

The elimination of the dielectric was what boosted the Q and thrust of the non dielectric Demonstrator device to 45,000 as against the dielectric fitted 1st Experimental device at 5,900. As Shawyer has shared from his experience, the use of a dielectric increases losses, reduces Q and reduces thrust.
« Last Edit: 06/01/2015 09:44 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 phaseshift

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Short snippet of Ruby code that computes the Shawyer Design Factor the way TheTraveller has in his spreadsheet.

def compute_design_factor( small_diameter_meters, large_diameter_meters, frequency_hz, jC)
   
    cM = 299705000.0
    cf = cM / frequency_hz
    jCFPI = jC * cf / Math::PI
 
    b = Math.sqrt( 1 - ( jCFPI / large_diameter_meters ) ** 2 )   
    s = Math.sqrt( 1 - ( jCFPI / small_diameter_meters ) ** 2 )
   
    df = (b - s) / ( 1 - b * s )
   
    return df
   
end

jC = BesselJ Cutoff

Before doing Df or resonance calc you need to know excitation mode TMm,n,p or TEm,n,p and the appropriate BesselJ value as per that mode. BesselJ value is driven by mode TE or TM and the associated m & n values.  p refers to the number of 1/2 waves between the end plates.

There are 2 tables provided. One for TE mode and one for TM mode. Each is indexed by the selected m & n values.

As example to use TE013 mode, use the TE table and the value at the intersection of the m=0 & n=1. = 3.8318  Then adjust end plate spacing or frequency or Df, via altering either/both end plate diameters to fit the desired number of p 1/2 waves between the end plates.

Tables attached.

And what? The above method comes directly out of your spreadsheet and produces the same values - I had to bounce all over to pull all the cells together and then simplify all the duplicate references :) - not sure what you're trying to point out - other than for people to use the above tables to pick a value for jC? 

« Last Edit: 06/01/2015 10:51 PM by phaseshift »
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline TheTraveller

Short snippet of Ruby code that computes the Shawyer Design Factor the way TheTraveller has in his spreadsheet.

def compute_design_factor( small_diameter_meters, large_diameter_meters, frequency_hz, jC)
   
    cM = 299705000.0
    cf = cM / frequency_hz
    jCFPI = jC * cf / Math::PI
 
    b = Math.sqrt( 1 - ( jCFPI / large_diameter_meters ) ** 2 )   
    s = Math.sqrt( 1 - ( jCFPI / small_diameter_meters ) ** 2 )
   
    df = (b - s) / ( 1 - b * s )
   
    return df
   
end

jC = BesselJ Cutoff

Before doing Df or resonance calc you need to know excitation mode TMm,n,p or TEm,n,p and the appropriate BesselJ value as per that mode. BesselJ value is driven by mode TE or TM and the associated m & n values.  p refers to the number of 1/2 waves between the end plates.

There are 2 tables provided. One for TE mode and one for TM mode. Each is indexed by the selected m & n values.

As example to use TE013 mode, use the TE table and the value at the intersection of the m=0 & n=1. = 3.8318  Then adjust end plate spacing or frequency or Df, via altering either/both end plate diameters to fit the desired number of p 1/2 waves between the end plates.

Tables attached.

And what? The above method coming directly out of your spreadsheet and produces the same values - I had to bounce all over to pull all the cells together and then simplify all the duplicate references :) - not sure what you're trying to point out - other than for people to use the above tables to pick a value for jC?

Yes use the tables, for now, to select the appropriate BesselJ value for the excitation mode.

Next version will directly calc the BesselJ value for the selected mode.

Ay the heart of the Df equation is the cutoff wavelength, which is driven by the BesselJ value for the selected excitation mode.

TE11 has a different Df than TE01 and different again for TM01. There is no one value for BesselJ.

Once the mode is selected and resonance is obtained, the physical antenna placement, length & design must be correct to excite the frustum in the mode that the frustum has been designed for.

Further to obtain the highest Q possible, the frustum impedance must match that of the Rf generator. To do that will require the physical ability to adjust the antennas local enviroment by some physically adjustable means.

I'm working to bring those placement & length calculations and impedance tuning methods to the calculator.

As it exists now, there are several more stages to be added.
« Last Edit: 06/01/2015 10:30 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 Dortex

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I'm having some trouble keeping up with all of this discussion, sadly. Has anyone thought of combining a magnetron with a high Q cavity? I know the latter needs to be tuned constantly during, but my untrained gut tells me the "dirty" RF signal gets around all that by emmiting a wider range of frequencies all at once.
« Last Edit: 06/01/2015 11:16 PM by Dortex »

Offline rq3

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Hey everyone,

Here is a summary of our current experimental design.
Any feedback is welcome and appreciated.  :)

Kurt

First post here, but have been following Shawyers claims for years. As an ex microwave engineer, just a few thoughts on your design. Short of getting into superconductive cavities, the ideal would be a silver plated, machined and highly polished copper cavity, with the large end plate in contact with the frustum walls using standard RF fingers (also silver plated). Orbel is one typical manufacturer. The end plate could then be actively tuned, in almost real time, using a small stepper motor or servo driven by a network analyser reading S21 and S12 to achieve an active match (highest Q), even in conditions of magnetron or thermal drift.

Also note that the vacuum conditions you mention are smack in the middle of Crookes radiometer operating pressures (best thrust from thermal effects), probably not what you want to see.

To truly alleviate thermal (gas buoyancy or molecular rebound) effects, you may want to aim for 1 uTorr or better.

Offline smartcat

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.. the thrust happens due to the interference between the standing wave k and the evanescent wave Beta, phase factors.  Where they interfere is where the phase shift is happening due to attenuation, as it propagates into the small end. Optimal thrust will occur when the amplitude of the standing waves is nearly the same as the amplitude of the evanescent waves and the two are out of phase. ...

I'm still trying to crunch all this into design equations that are hopefully, more accurate and informative. It may take me a while.

Todd

My feeling is that you are on the right track. For some reason I keep thinking that there is a rotational factor (about the cavity axis) and a related symmetry issue; as in perhaps needing to break the symmetry to reach a stable state.

Offline zellerium

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First post here, but have been following Shawyers claims for years. As an ex microwave engineer, just a few thoughts on your design. Short of getting into superconductive cavities, the ideal would be a silver plated, machined and highly polished copper cavity, with the large end plate in contact with the frustum walls using standard RF fingers (also silver plated). Orbel is one typical manufacturer. The end plate could then be actively tuned, in almost real time, using a small stepper motor or servo driven by a network analyser reading S21 and S12 to achieve an active match (highest Q), even in conditions of magnetron or thermal drift.

Also note that the vacuum conditions you mention are smack in the middle of Crookes radiometer operating pressures (best thrust from thermal effects), probably not what you want to see.

To truly alleviate thermal (gas buoyancy or molecular rebound) effects, you may want to aim for 1 uTorr or better.

I hadn't heard of Crookes radiometer before, but that is a good point. We will still test in the 1mTorr chamber just to see what happens, maybe the thrust increases and we just have more/different data to analyze.

We may be able to use the other chamber in our lab which can reach 50 uTorr I believe, perhaps better, but we will have to be much more careful about what we put in that chamber because it is the best one on campus.

What do you make of the intermediate cavity idea?  Do you know of any better ways to send a magnetron signal through a coax?

Thanks for the feedback and welcome to the forum :)

Kurt

Offline birchoff

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Hey everyone,

Here is a summary of our current experimental design.
Any feedback is welcome and appreciated.  :)

Kurt

Best of luck with the experiments, but will we be able to see the results and data from the experiments before the 2017AiAA conference? or was that a typo?

Offline rq3

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Kurt, thanks for the welcome.

Like a lot of "home brew" science, there is a lot of back and forth on this forum between folks with hugely disparate expertise. It's all fascinating and valuable input.

The basis of this experiment, in all cases, seems to be:

1) Can I couple the maximum amount of electromagnetic radiation into a sealed RESONANT cavity while;
2) Measuring thrust NOT caused by known effects


Item one is easy. There are decades of research and engineering to fall back upon, no matter what the cavity configuration may be. Keep the skin effect of the cavity at a minimum (maximum conductivity). Avoid dielectric materials in the cavity, UNLESS the dielectric can also be matched for resonance (see DRO oscillator). Measure forward power (S21) and reverse power (S12) dynamically to tune the cavity for resonance.

Good luck with Item 2. That's why we're all here!

Rip

Offline Rodal

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Jo Hinchliffe drilled the hole for the microwave injection antenna of 24 GHz Baby EM Drive and will shave down some weight so the levitator will be able to lift the cavity.

https://hackaday.io/project/5596-em-drive#



« Last Edit: 06/02/2015 12:48 AM by Rodal »

Offline Rodal

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I should know better than to post a 1st draft of anything, but here goes nothing...

What I've done is put together all of the pieces we have been working on, between Egan, Yang, De Aquino and Shawyer. What I ended up with didn't surprise me. What did is how much this "mimics" gravity  in the PV Model is not even funny!

Let the show begin!

Todd

The show is not ready for prime-time yet, but working on it...

Continuing from here:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1381966#msg1381966

An outstanding important question in developing this theory of EM Drive motion due to internal evanescent waves produced by geometrical attenuation (due to tapering of the walls of the truncated cone towards the small end) is whether the evanescent waves can couple to the enhanced energy density due to Q resonance standing waves.  It is is very important to show this, because otherwise the EM Drive would not be able to be superior to a perfectly collimated photon rocket.  The stored energy density from resonance is the key.

It is important to show whether there is coupling of the evanescent waves with the standing waves.  That there is coupling between travelling waves and evanescent waves is shown in the paper of Zeng and Fan where one mode after another gets attenuated as it propagates towards the small end.  However that's for an open waveguide, where travelling waves and evanescent waves can be easily shown to be in phase (particularly for phase constant equal to zero).  Doubts were expressed in this thread as to whether this is possible for standing waves and evanescent waves.

The answer appears to be yes, at least in some qualified situations.  There are a number of papers showing coupling between whispering -gallery modes and evanescent waves.  It is far from clear whether whispering-gallery modes could be present in the EM Drive operation, (whispering-gallery modes would involve much higher frequencies -what is the highest frequency that a Magnetron puts out ?-).

This recent reference (2013) shows whispering-gallery modes in the microwave frequency at 10 GHz: http://arxiv.org/pdf/hep-ph/0506074

The fact that whispering-gallery modes can couple with evanescent waves is interesting enough.

Coupling between high Q cavities (of the ring type) and evanescent waves have also been shown.

Constructive interference.

It looks like the analysis may require numerical analysis, as all the papers I have seen so far have used the Finite Difference method to solve the problem numerically. 

The problem is difficult, mathematically, but entirely within Standard Physics.

It is intriguing whether some of the gradient theories (Shawyer's gradient in group velocity, McCulloch's gradient of Unruh wavelengths,  Notsosureofit gradient of dispersion, and this one geometrical attenuation gradient with coupling of standing and evanescent waves, are related somehow, rather than just superficially).





« Last Edit: 06/02/2015 02:06 AM by Rodal »

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