Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2168893 times)

Offline rfmwguy

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...

The use of HDPE rather than PTFE at MW freqs has been bothering me. Nowhere over 1 GHz have I heard of HDPE, which could indicate high moisture absorption or reflectability. Also, the melting point of HDPE is rather low compared to the 250 deg C of PTFE.

The comparison tables are here: http://www.vanderveerplastics.com/compare-materials.html?sel1=hdpe&sel2=teflon-ptfe-fep

If someone knows why HDPE (typically plastic milk jugs( were initially used, it would be interesting.

"High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a polyethylene thermoplastic made from petroleum. It is sometimes called "alkathene" or "polythene" when used for pipes.[1] With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes, and plastic lumber. HDPE is commonly recycled, and has the number "2" as its resin identification code (formerly known as recycling symbol)." per http://en.wikipedia.org/wiki/High-density_polyethylene

HDPE has very interesting properties, it has been used for biomedical applications, for garbage bags and countless commercial applications. It is very tough, it has excellent sliding abrasion resistance and is self lubricating.

As to why it was used as a dielectric for NASA's EM Drive, my recollection is that it was based on prior experience by Paul March, originally working with Prof. Woodward on his Mach Effect theory and experiments, and that it was based, as I noted above, on the imaginary properties acting as absorption coefficients in electromagnetic waves.

By the way, NASA also used PTFE and Nitrile Rubber as dielectrics.  They obtained the highest thrust force with HDPE

This is significant..the difference in dielectric properties of HDPE and PTFE are curious. While HDPE has a lower temp and freq rating, HDPE has an unusual Dielectric Constant (K or E) variance of 1 to 5 while PTFE has confined K of 2-2.1. This is probably why HDPE is not normally used in MW circuits...unpredictability or randomness, if you will. In essence, a puck/layer of HDPE would present a wide K variance across its surface to EM, unlike PTFE. Few materials have this: http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm

Thinking out loud, is this perhaps why more thrust was achieved with HDPE as opposed to PTFE? Permittivity in EM fields comes to mind: http://maxwells-equations.com/materials/permittivity.php

Perhaps some folks can wrap their heads around this K variance versus thrust...I have a brain cramp :o

Offline deltaMass

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IULIAN:

Hi,
.......snip
Iulian

Another thing to consider; From your video you have the unit on the end of a looped spring hanging from a shelf....  For the Downwards test you are trying to force the unit downwards AGAINST the natural TENSION of the spring...  you need to measure just how much energy it takes to pull the spring down as much as the unit did when you powered it up.!

The original "thrust was with the aid of the spring pulling the unit upwards. 

Placing the complete unit onto a balance board "like a child's see-saw,  American teeter-totter"  with an equal weight on the other end will enable you to perform these types of measurements
That's all true, and hanging one's hat on the value of the thrust and the air mass change is not to be recommended yet. I shouldn't have quoted them to three significant figures because the experimental precision is in no way that good. I also noticed how much the readings were changing during this very latest test.

But we do know that the net force changes direction when the frustum is flipped upside down. That fact alone makes it all worthwhile continuing.

Offline Rodal

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...HDPE has an unusual Dielectric Constant (K or E) variance of 1 to 5 while PTFE has confined K of 2-2.1. This is probably why HDPE is not normally used in MW circuits...unpredictability or randomness, if you will. In essence, a puck/layer of HDPE would present a wide K variance across its surface to EM, unlike PTFE. Few materials have this: http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm
...

HDPE is not random.  It is fairly straightforward to characterize as having well determined properties, based on its molecular weight for example, and method of manufacture.  If the properties of HDPE would be random or difficult to characterize, believe me that HDPE would not be used for biomedical applications, which have higher standards for material properties than many commercial applications do.

What happened here is that you are looking at this row:

High Density Polyethylene (HDPE), Molded   1.0 - 5.0

instead of looking at this one, which is the appropriate row to look at:

Polyethylene LDPE/HDPE     2.26 @ 1 MHz
                                                2.26 @ 3 GHz

Those are the appropriate properties for the NASA Eagleworks dielectric.
Now: that's a narrow range, and it even gives you data at the GHz range for direct application to microwaves.

NASA Eagleworks did not use a molded product (see my previous posts, given the identity of the product used by NASA). 

Having said that, the fact that this website gives properties for HDPE in two completely different rows, with different ranges, and does not explain the differences does not give me a good impression about the quality of the data in this website (which is also the same website I initially found when I was quickly looking for the HDPE properties)

Authoritative handbooks like this one give much more reliable data than these websites: http://bit.ly/1Lr0pSt

Of course, the best thing is to have analytical instruments to properly characterize the material properties of a polymer, which is what we did.



Note that in this same website they also have this funny note, acknowledging that they had the tan delta for PTFE off by a factor of 10 until Craig  ;) found the error !!!!!

Quote
Thanks to Craig B. for correcting the loss tangent for Teflon (0.00028 rather than 0.0028).
« Last Edit: 05/22/2015 01:43 AM by Rodal »

Online WarpTech

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I've seen reference to the Demonstrator Thrusters DF as .844 in 3 different Shawyer documents now.  Hmmmm something seems amiss
Can you please provide the links (or attach pdf) to all 3 references havign DF = 0.844 ?

These are basically all the "same" paper. Copy and Paste.

Offline LasJayhawk


Take a gander at the section on energy conservation here:

http://emdrive.echothis.com/Generic_EM_Drive_Information


Just thinking that maybe there should be a third option:  Since a constant acceleration transforms as a 4-space rotational velocity (?), there may be an invariant for the tensor which allows Energy to Momentum conversion. ?  This would be what, a "false force" driven by the dispersion cycle in the cavity ??  I'm visualizing that cycle as distorted compared to symmetrical cavity which would want to make it (the world line) curve in x,t.

I understand what you're trying to say and I like it on several levels. This is one reason I asked if you had thought of introducing another EM wave into the cavity not in phase, but having the ability to control the phase and frequency. Sorry, it's the old dog with a bone syndrome here.



The short answer is yes.  As RODAL mentioned above, putting a pair of frequencies at the half-power points of the resonance.  I did my thesis on cylindrical cavity resonance that way, many long years ago.
Thank you, from one old dog to another. Like I've told others I remember when engineering/science was a rock hitting a rock, then it all turned to dirt. That short answer is long on my understanding.

Old??? I was looking at ion drives and wondering why we don't use beam focusing plates like a 6L6. :)

But I am wondering something. If this thing works on standing waves, and standing waves require a node on both ends of the cavity, wouldn't this thing have a cylinder of standing waves surrounded by traveling waves?


Offline phaseshift

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I've seen reference to the Demonstrator Thrusters DF as .844 in 3 different Shawyer documents now.  Hmmmm something seems amiss
Can you please provide the links (or attach pdf) to all 3 references havign DF = 0.844 ?

These are basically all the "same" paper. Copy and Paste.

Maybe this was an intentionally moldy breadcrumb.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

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"Mimics G".. I like that phrase, a lot.

... nice!!.

I would be cautious of closing the door on em-density. Instinct still has me thinking possibly more of an E relationship than B:H, but a rig to test it implies considerable values of E.  Somewhere lurking in here I think polarisation is also a factor.

Thanks! You may be right about the energy density playing a significant roll, but I'm still formulating the equations and exploring various options. With a 3 day weekend, I may have time to write some of this stuff down in MathType.

My understanding of gravity is unique in that I prefer the PV Model of gravity over GR for engineering purposes, and I have a quantum gravity model for engineers that works well enough. Relative to EM waves, it works like a variable refractive index, K. In the case of "real" gravity, it affects all wavelengths equally. In the case of a waveguide, K only affects a narrow bandwidth near the cut-off. It doesn't affect "test particles". However, IMO the cause is the same, attenuation of the wave function due to a change in the refractive index, i.e., a change in the group velocity.

My hypothesis for how the EM Drive works is more like Frame Dragging than a rocket. The photons drag the frustum in the direction they are moving. They do not propel it in the opposite direction like a photon rocket, or how it is being described by Shawyer and others. The "drag" force is asymmetrical because the attenuation cut-offs are asymmetrical.

I think that if there were a charged particle oscillating from end to end inside, it would be more obvious than when it's photons. The charge feels the force of it's oppositely charged reflection in the copper ground plane, and wants to drag it along with it. It would be an interesting problem to calculate the electric field of a point charge, inside a frustum and see what the forces on that test particle would be.  ::)

Todd

Offline SeeShells

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...HDPE has an unusual Dielectric Constant (K or E) variance of 1 to 5 while PTFE has confined K of 2-2.1. This is probably why HDPE is not normally used in MW circuits...unpredictability or randomness, if you will. In essence, a puck/layer of HDPE would present a wide K variance across its surface to EM, unlike PTFE. Few materials have this: http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm
...

HDPE is not random.  It is fairly straightforward to characterize as having well determined properties, based on its molecular weight for example, and method of manufacture.  If the properties of HDPE would be random or difficult to characterize, believe me that HDPE would not be used for biomedical applications, which have higher standards for material properties than many commercial applications do.

What happened here is that you are looking at this row:

High Density Polyethylene (HDPE), Molded   1.0 - 5.0

instead of looking at this one, which is the appropriate row to look at:

Polyethylene LDPE/HDPE     2.26 @ 1 MHz
                                                2.26 @ 3 GHz

Those are the appropriate properties for the NASA Eagleworks dielectric.
Now: that's a narrow range, and it even gives you data at the GHz range for direct application to microwaves.

NASA Eagleworks did not use a molded product (see my previous posts, given the identity of the product used by NASA). 

Having said that, the fact that this website gives properties for HDPE in two completely different rows, with different ranges, and does not explain the differences does not give me a good impression about the quality of the data in this website (which is also the same website I initially found when I was quickly looking for the HDPE properties)

Authoritative handbooks like this one give much more reliable data than these websites: http://bit.ly/1Lr0pSt

Of course, the best thing is to have analytical instruments to properly characterize the material properties of a polymer, which is what we did.



Note that in this same website they also have this funny note, acknowledging that they had the tan delta for PTFE off by a factor of 10 until Craig  ;) found the error !!!!!

Quote
Thanks to Craig B. for correcting the loss tangent for Teflon (0.00028 rather than 0.0028).
Well dang, here I thought we had nailed down the mystery acceleration. Alas, we still have this systemic anomaly ( I love that phrase). All along I thought we could point our fingers at the chirality of twisted polymer crystals.  http://www.esrf.eu/UsersAndScience/Publications/Highlights/2011/scm/scm4


Offline phaseshift

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Do we have the Flight Thruster Dimensions?

I have found

bD: .265m
height: .164m

freq: 3.85GHz

DF: ?
sD: ?



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Offline SeeShells

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Old??? I was looking at ion drives and wondering why we don't use beam focusing plates like a 6L6. :)

But I am wondering something. If this thing works on standing waves, and standing waves require a node on both ends of the cavity, wouldn't this thing have a cylinder of standing waves surrounded by traveling waves?
I have a couple of 6L6s in the old radio I just rebuilt, because it's just like the one I rebuilt when I was 14. Hats off to you.

I still have an old T-shirt from the 60's that had the year 2000 on the top and a group of flying cars displayed below. We're a few years behind in having flying cars that levitate and spacecraft that zoom around, but I'd sure love to see it happen before...you know. I think we're close, very close to that childhood dream. (sorry if I got off track but we're all dreamers here)

As far as your question of a cavity of standing waves surrounded by standing waves you might have a look at these different modes. 


Online WarpTech

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This is also interesting for TM010 mode. Note where the H (magnetic) field is located. At the big end, right where Shawyer feeds in the Rf in the Demonstrator & Flight Thruster EM Drives.

Backs up the Patent mention of TM01 mode.

Fairly clear to me, TM010 is probably Shawyers EM Drive mode.
What is clear is that TM010 is definitely not the mode shape at the reported frequency and dimensions of Shawyer's Flight Thruster

Even at the lower frequency (almost 1/2 of the Flight Thruster) used by NASA Eagleworks (below 2 GHz with a dielectric) they are into a much higher mode shape: TM212

and look at the natural frequency shown on the image you posted above for NASA Eagleworks: TM010 is below 1 GHz without a dielectric

The TM01 mode is the mode shown to have the highest reflection, per Zeng and Fan's paper.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-17-1-34&id=175583

It also has fairly high attenuation. To raise Q, Shawyer needed more reflection, so he made the cone angle greater, which may or may not be counter productive at the lower attenuation value depending on how high a Q he can get. You can see why in the attachments.
« Last Edit: 05/22/2015 03:16 AM by WarpTech »

Offline phaseshift

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Do we have the Flight Thruster Dimensions?  I have found  bD: .265 m   height: .164m
Based on the photograph, and knowing that bD: .265m; height: .164m; what is your estimate of the small diameter ?

I'll work on it tonight :)
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"Mimics G".. I like that phrase, a lot.

... nice!!...

...

I think that if there were a charged particle oscillating from end to end inside, it would be more obvious than when it's photons. The charge feels the force of it's oppositely charged reflection in the copper ground plane, and wants to drag it along with it. It would be an interesting problem to calculate the electric field of a point charge, inside a frustum and see what the forces on that test particle would be.  ::)

Todd

To elaborate on this, even without having to solve the electric field problem. In a gravitational field around a planet, where the refractive index is approximated as;

K ~ exp[2*G*M/R*c^2]

Voltage varies as 1/sqrt(K), where R is the distance to the center of the Earth, of mass M for example.

The voltage potential at the radius r from the charge is,

V(r) = Q/4pi*eps0*r

Therefore;

V(r, R) = V(r)*exp[-G*M/R*c^2]

Obviously, a particle closer to the Earth will have a lower voltage potential than one high in orbit. Now, consider a charged particle in a copper cone. It has a voltage potential relative to it's reflection in the copper ground plane. That potential is lowest at the apex of the cone. Once again, a frustum mimic's gravity, very well I might add!

Todd





Offline LasJayhawk


Old??? I was looking at ion drives and wondering why we don't use beam focusing plates like a 6L6. :)

But I am wondering something. If this thing works on standing waves, and standing waves require a node on both ends of the cavity, wouldn't this thing have a cylinder of standing waves surrounded by traveling waves?
I have a couple of 6L6s in the old radio I just rebuilt, because it's just like the one I rebuilt when I was 14. Hats off to you.

I still have an old T-shirt from the 60's that had the year 2000 on the top and a group of flying cars displayed below. We're a few years behind in having flying cars that levitate and spacecraft that zoom around, but I'd sure love to see it happen before...you know. I think we're close, very close to that childhood dream. (sorry if I got off track but we're all dreamers here)

As far as your question of a cavity of standing waves surrounded by standing waves you might have a look at these different modes.

I downloaded it when you posted it earlier, but to be honest, when I look at the figures I see a cylinder, not a frustrum. Don't ask for the math, I can't give it to you. :(

But there is something here about power that is worth a mention. I had a pre WWII Stromberg-Carlson with a pair of 6L6's in push pull ( and an tuned labyrinth speaker to boot) and my current baby a 37 Philco 37-116 with a pair of 6B4G's. I doubt either could push much more than 20 watts, but both can move more air than a modern radio rated at 200+ watts, and sound better as well. Note to smart people: AM radio doesn't sound bad, the receivers built in the last 60 years do.

There is something old school about this, and I'm still trying to put my finger on it. But I am leaning toward switching to a bow tie shape, and feeding both ends 90 degrees from what we are doing now ( bounce off the sides, not the ends )

Online WarpTech

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I don't think Shawyer's math is correct, but based on some conversations here, I worked out a simple equation to optimize Df to determine the size of the small end;

y = lambda,

y_0/y_g1 = (1 + y_g2*Df/y_0) / (Df + y_g2/y_0)

If Df = 1, then y_0/y_g1 = 1, independent of what y_g2 is.

If Df = 0, then y_0/y_g1 = y_0/y_g2, and we have a cylinder with no taper.


Todd

Offline deltaMass

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I recall working out a similar result a few pages back

Offline Chrochne

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Lately. I see a lot of new criticism. I think its fine, but I also think that there were a lot of tests that have proven that there is a thrust.

I am writting this to share this idea. Is it possible to convince some of the main critics of this device to manufacture their own EmDrive and test it? I think that their criticism can not be taken seriously and scientificaly correct, if they do not make their own tests. I say yes to criticism, but I can not take it seriously until they make their own tests.

We also really need FAQ a lot :-P. Too much folks are asking about the questions that were already answered and properly tested before.

I also hope this thread will return to more scientific thread and maybe we can hear from Mr. Paul and White again here in the future.

With kind regards,

Chrochne

Offline zen-in

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Lately. I see a lot of new criticism. I think its fine, but I also think that there were a lot of tests that have proven that there is a thrust.

I am writting this to share this idea. Is it possible to convince some of the main critics of this device to manufacture their own EmDrive and test it? I think that their criticism can not be taken seriously and scientificaly correct, if they do not make their own tests. I say yes to criticism, but I can not take it seriously until they make their own tests.
...
Chrochne

I am a critic because I have not seen consistent evidence it works.  I also have not seen any experiments done that would rule out alternative explanations.   I am also very handy with metalwork, RF, etc and could build one in a few days.    However I choose not to do this because I have other more interesting experiments I want to do.

Offline TheTraveller

Do we have the Flight Thruster Dimensions?  I have found  bD: .265 m   height: .164m
Based on the photograph, and knowing that bD: .265m; height: .164m; what is your estimate of the small diameter ?

Those are OUTSIDE dimensions. We need INSIDE dimensions.
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Offline TheTraveller

This is also interesting for TM010 mode. Note where the H (magnetic) field is located. At the big end, right where Shawyer feeds in the Rf in the Demonstrator & Flight Thruster EM Drives.

Backs up the Patent mention of TM01 mode.

Fairly clear to me, TM010 is probably Shawyers EM Drive mode.
What is clear is that TM010 is definitely not the mode shape at the reported frequency and dimensions of Shawyer's Flight Thruster

Even at the lower frequency (almost 1/2 of the Flight Thruster) used by NASA Eagleworks (below 2 GHz with a dielectric) they are into a much higher mode shape: TM212

and look at the natural frequency shown on the image you posted above for NASA Eagleworks: TM010 is below 1 GHz without a dielectric

The TM01 mode is the mode shown to have the highest reflection, per Zeng and Fan's paper.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-17-1-34&id=175583

It also has fairly high attenuation. To raise Q, Shawyer needed more reflection, so he made the cone angle greater, which may or may not be counter productive at the lower attenuation value depending on how high a Q he can get. You can see why in the attachments.

TM01 also puts the biggest H field at the big end, which is where he couples in his external Rf. I feel the visible fact of where Shawyer feeds in his Rf, in the Demonstrator, Flight Thruster1 and Flight Thruster2 is an important bread crumb.

Engineering is always about compromise.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

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