### Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1797722 times)

#### deltaMass

• Full Member
• Posts: 955
• A Brit in California
• Liked: 671
• Likes Given: 275
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #180 on: 05/25/2015 05:08 AM »
Two words: Ning Li

Be afraid. Be very afraid

#### WarpTech

• Full Member
• Posts: 1223
• Do it!
• Vista, CA
• Liked: 1290
• Likes Given: 1740
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #181 on: 05/25/2015 05:16 AM »
(...)
Table 3, page 28 of the original Chinese paper shows:

Vertical Axis: ( (Frequency[Hz] * Diameter[cm] )/(Hz*cm) )2 * 10- 20

Horizontal Axis:  (Diameter / Height)2

I didn't have the time yet to chase what Diameter is she referring to.

To me it is a table for mode shapes in terms of natural frequency and geometry.

Let me know what you think

She's saying to;

1. Choose the mode you want to operate in.
2. Choose the small diameter based on the cut-off of that mode.
3. Choose the large diameter and height based on Figure 3, (D/L)^2 as the aspect ratio.

On the horizontal axis, 0 is the cut-off diameter. On the vertical axis, D is the average diameter and f is the frequency of the mode. So it represents the average wave velocity of that mode, in the waveguide, squared, but I don't understand the 10^-20 yet unless it's just unit fixing.

I also think I found a (minor?) error in the 2013 paper. In my estimation, equations 4 and 6 are correct. Where I disagree is that her premise is that there are charged particles in the volume, and then on equations 7 and 8, she removes the particle momentum density and the energy density of the field, for no apparent reason and then IMO, she abruptly ends the section.

What I think it "should" be is the following;

Equation 4 is straightforwardly interpreted as the input power of the field, is absorbed by the particles of the frustum. The Div(S) through the frustum is zero, (by definition) leaving only the time derivative of the energy density of the field and the energy density of the particles. The particles may be interpreted as the charged particles of the frustum, negative electrons and positive lattice ions, accessible through the skin effect. There are current and charge densities just as she described, stored in the metal as inductive and capacitive energy density, so Wp is not zero. The reactive power Pe, and Ph, and losses Pr, are not zero. So Power in x time = energy  stored + energy lost.

Equation 6 is also interpreted similarly. The divergence of the tensor on the RHS is zero, by definition there is nothing coming out of the frustum. This leaves only the LHS which says that the force on the particles is opposite the force on the field, action = reaction. The particle momentum density, Gp term must be split into positive and negative contributions, and relative masses. Then the momentum lost by the field, is gained by some distribution of these charged particles, the NET result is propulsion.

Her force analysis is missing a duty cycle, but other than that I think it's still correct. Because, even though the divergence of the tensor is zero, it is zero because there is an opposing pressure from the walls of the frustum caused by the skin effect, that prevents the field from escaping. The action = reaction forces on the LHS of equation 6 that I spoke of above, are equal to the pressures she's integrating on the surface. Integrating the pressures is easier than integrating the scattering of every photon with lattice ions and electrons.

Todd

#### ThinkerX

• Full Member
• Posts: 303
• Liked: 112
• Likes Given: 59
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #182 on: 05/25/2015 05:38 AM »
Ning Li

http://en.wikipedia.org/wiki/Ning_Li_(physicist)

Looks a bit 'out there,' but maybe something can be salvaged from the papers?

#### deltaMass

• Full Member
• Posts: 955
• A Brit in California
• Liked: 671
• Likes Given: 275
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #183 on: 05/25/2015 05:47 AM »
It's a bit late for salvage.

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #184 on: 05/25/2015 07:14 AM »
This discussion is clearly interminable, in the literal sense of that word. Whatever experimental results accrue, in past, present or future, there will always be doubt. This is why I am so strongly in favour of a space-based test. I've already laid out my reasons. Without that, I'd lay odds that one could return to this forum in years to come and people would still be arguing the toss.

Let's cut the Gordian Knot!

The test program I  plan to run will remove ALL doubt that the EMDrive generates real propellantless thrust without needing a space test.

One of my goals is to be able to hold the EMDrive & while switching it on and off, to be able to FEEL the thrust.

You may have posted it somewhere before Traveller, but I haven't had the chance to read the entirety of threads 1 and 2.  Do you have a general idea of what kind of timeline you are going to be working off of with your test program?  Do you expect to have a build ready in the next two months, with another month or two for testing, or do you expect it take longer?

Just trying to get a sense of experimental development on this device given we can't expect EW results until at least late July.

Have purchased most of the electronics and started work writing the USB based control & data logging software.

Balance beam & Faraday Cage designs are finished.

Working on the test protocols, which will be published here to get feedback on how to improve to reduce / eliminate doubt.

Working on the interactive design spreadsheet so I can feed back test data to improve the model.

Expect to build the frustum in 3-4 weeks & start test right away as in working out the best way to excite it in TM mode, getting resonance & impedance matching at low power of 1 watt. So fair amount of work to do before using the balance beam. BTW plan to copy Mullerton with the clips to attach the end plates so I can easily get inside access.

« Last Edit: 05/25/2015 07:15 AM 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

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #185 on: 05/25/2015 11:37 AM »
2 question to the group:

Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?

2) 5mm in from each frustum end and around the middle there will be 8 laser cut, equally, spaced 2mm diameter holes through the frustum side wall (24 in total) to allow hot air to escape the frustum, so as to very significantly reduce / eliminate buoyancy.

Is this an effective way to deal with buoyancy issues?
« Last Edit: 05/25/2015 11:41 AM 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

#### Paul Novy

• Member
• Posts: 12
• Poland
• Liked: 11
• Likes Given: 3
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #186 on: 05/25/2015 11:52 AM »

Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?

I would go for an old fashioned soldering.  Why introduce another unknown variables caused by the glue?

BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #187 on: 05/25/2015 12:04 PM »

Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?

I would go for an old fashioned soldering.  Why introduce another unknown variables caused by the glue?

BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.

Thanks for the comment.

I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.

As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

#### Flyby

• Full Member
• Posts: 382
• Belgium
• Liked: 447
• Likes Given: 46
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #188 on: 05/25/2015 12:39 PM »
You'll need to verify how the epoxy glue reacts to temperature, because your frustum will get hot...
Migth also need to roughen the exterior to give the epoxy a better adherence.

0.5mm thickness will most likely warp when soldering, so I'd go for the glue+strip on the outside.

Then the challenge will be to get the 2 edges align according the curve of the cone, as they will tend to angle. The strip you place on top of it, will need to be slightly curved also...

#### deltaMass

• Full Member
• Posts: 955
• A Brit in California
• Liked: 671
• Likes Given: 275
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #189 on: 05/25/2015 12:48 PM »
@TheTraveller
Re. the join - you may find that you don't get all the way down to the original resistivity with that approach, and the EM will see a resistive discontinuity, which will distort mode shapes in some way. But I can't say if this is a major or minor effect. Indium might be better, but I'm unsure how you'd apply it. It's usually used in a pressure fit. My gut tells me that what you propose is good enough.

Re. the RF feed - you'll want to do all drilling (air vents too) before soldering the final end cap on, else you might leave copper scurf rattling around in there. This will tend to lower the Q. The placement of the RF feed hole is rather chicken-and-egg because you won't know the impedance to be matched until you use it. That's unless you or someone else can calculate it. This problem is exacerbated if you don't have variable frequency ability. Perhaps instead you're going for the variable end plate approach. In any case, you're going to need something to do the impedance matching. Paul March started out using a "trombone" style matcher for this, and now has something considerably more sophisticated.

Re. venting heated air - this will cause the weight to change as dm = d(rho)*V*g Newton, where d(rho) is the change in air density between the two temperatures and V is the cavity volume. If you are weighing the cavity then this will obviously be a significant factor. Fortunately it can be cancelled away by flipping  the cavity upside down, since then
F + dm = apparent (measured) upthrust = weight loss
F - dm = apparent  (measured) downthrust = weight gain
where F is the true thrust.
Solve for F, dm as usual:
F   = (up + down) / 2
dm = (up - down) / 2
« Last Edit: 05/25/2015 01:46 PM by deltaMass »

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #190 on: 05/25/2015 01:45 PM »
You'll need to verify how the epoxy glue reacts to temperature, because your frustum will get hot...
Migth also need to roughen the exterior to give the epoxy a better adherence.

0.5mm thickness will most likely warp when soldering, so I'd go for the glue+strip on the outside.

Then the challenge will be to get the 2 edges align according the curve of the cone, as they will tend to angle. The strip you place on top of it, will need to be slightly curved also...

Plan to use a machine shop that can do a roll to ensure the final rolled frustum is aligned at each corner as well as along the butt seam.

Will then place the laser cut flange on a glass table (so I can observe what is happening from the under side).

Next will insert the appropriate end of the frustum inside the flange that has a laser cut ID to match the frustum OD.

Then place a thin glass plate on the top of the frustum other end to ensure slight but equal pressure on all sides of the frustum.

Next, once I can see there is contact along the full circumference of the frustum end with the glass table, will then epoxy, from outside, the entire seam, following the recommended procedure to get a strong and long lasting seam as per the UL certification for the epoxy.

Once cured, will flip it over and repeat for the other ends flange.

Lastly will epoxy the side wall butt seam.

The air holes will be laser cut, so no need to worry about swaft inside the frustum.

The curved end plates will be sandwiched between the epoxied on flange and a flat covering plate, with the three layers held together by Mulletron's clips. This will enable internal access, the ability to alter the antenna arrangement and position, the ability to quickly change end plates and by using thin spacer rings, to alter the frustum's physical length.
« Last Edit: 05/25/2015 01:47 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

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #191 on: 05/25/2015 01:59 PM »
@TheTraveller
Re. the join - you may find that you don't get all the way down to the original resistivity with that approach, and the EM will see a resistive discontinuity, which will distort mode shapes in some way. But I can't say if this is a major or minor effect. Indium might be better, but I'm unsure how you'd apply it. It's usually used in a pressure fit. My gut tells me that what you propose is good enough.

Re. the RF feed - you'll want to do all drilling (air vents too) before soldering the final end cap on, else you might leave copper scurf rattling around in there. This will tend to lower the Q. The placement of the RF feed hole is rather chicken-and-egg because you won't know the impedance to be matched until you use it. That's unless you or someone else can calculate it. This problem is exacerbated if you don't have variable frequency ability. Perhaps instead you're going for the variable end plate approach. In any case, you're going to need something to do the impedance matching. Paul March started out using a "trombone" style matcher for this, and now has something considerably more sophisticated.

Re. venting heated air - this will cause the weight to change as dm = d(rho)*V*g Newton, where d(rho) is the change in air density between the two temperatures and V is the cavity volume. If you are weighing the cavity then this will obviously be a significant factor. Fortunately it can be cancelled away by flipping  the cavity upside down, since then
F + dm = apparent (measured) upthrust = weight loss
F - dm = apparent  (measured) downthrust = weight gain
where F is the true thrust.
Solve for F, dm as usual:
F   = (up + down) / 2
dm = (up - down) / 2

Will be using a variable Rf generator that can alter freq in 1kHz steps, even at 3.85GHz.

No swarf as the holes are laser cut when the frustum is cut.

I have some thin copper mesh strips and silver epoxy that I intend to use along the side wall seam. Then after several layers, will overlayer with the Copper Epoxy, which also bonds other metals. It would appear Shawyer did something similar in his 1st Experimental unit as per the attached image.

As my 1st step is to excite the frustum in TM mode, the plan is to use a stud antenna in the centre of the small end. Once I get resonance at close to what my spreadsheet model predicts, will then apply 1W at that frequency and start playing with antenna position and impedance matching before ramping up the power to my max 100W.

I do believe what we see in the 2nd image to the left of the Red RF feed may not be an impedance matching system but instead an arm that extends inside the Flight Thruster such that Shawyer can fine tune the antenna position. It appears to have a small arm / crank on the left end and the ability to slide in and out.
« Last Edit: 05/25/2015 02:08 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

#### Rodal

• Senior Member
• Posts: 5834
• USA
• Liked: 5901
• Likes Given: 5249
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #192 on: 05/25/2015 02:01 PM »
(...)Vertical Axis: ( (Frequency[Hz] * Diameter[cm] )/(Hz*cm) )2 * 10- 20...
... I don't understand the 10^-20 yet unless it's just unit fixing...
Fig. 3, p.7 of translated paper http://www.emdrive.com/NWPU2010translation.pdf

The factor of 10-20 is necessary to avoid writing a huge number on the plotted vertical axis, mainly because the frequency units used by the authors are in Hz instead of GHz.

For example, take a value of "18" in the vertical axis, this really means 18*1020, which when multiplied by 10-20, gives 18.

If she would have used GHz (1 GHz = 109 Hz) instead of Hz as the unit for frequency, the factor would have to be instead (109)2 * 10-20 = 10-2
Also, if in addition to using GHz instead of Hz units,  she would have used decimeters (1 decimeter = 10 centimeters) as the unit of length, there would be no need for multiplying factor at all.
So, you can read the units in the Figure 3 as being given in GHz for frequency and decimeter for length, and that avoids the factor of  10-20
« Last Edit: 05/25/2015 02:08 PM by Rodal »

#### Rodal

• Senior Member
• Posts: 5834
• USA
• Liked: 5901
• Likes Given: 5249
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #193 on: 05/25/2015 02:20 PM »
...I also think I found a (minor?) error in the 2013 paper. In my estimation, equations 4 and 6 are correct. Where I disagree is that her premise is that there are charged particles in the volume, and then on equations 7 and 8, she removes the particle momentum density and the energy density of the field, for no apparent reason and then IMO, she abruptly ends the section....
Can you please elaborate why youthink this is, maybe, just a (minor) error by Prof. Yang and her co-authors?

(And by the way, I am looking at the 2010 paper, not the 2013 paper, in my comments below)

They write (2010 paper, translation page 4,  original page 28)

http://www.emdrive.com/NWPU2010translation.pdf
Quote
If the microwave electromagnetic field consists of charge particles, due to the
electromagnetic force, the charge particles can travel within the electromagnetic
field, so the charge particles can acquire energy and momentum from the
electromagnetic field. This indicates that electromagnetic field have energy and
momentum.

The microwave electromagnetic field inside the cavity is composed of photons (at microwave frequencies), which as we all know, have no charge whatsoever.  So the microwave electromagnetic field does not consist of charge particles (unless one considers the virtual particles of the QV or one considers ionized air).  This is the difference between Greg Egan's equations http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html, who finds no net thrust force, since he doesn't consider this term at all.

If there are any charges and currents, they are only present in the copper metal (translation says "brass"), and not inside the empty microwave cavity.  This seems to me a major issue, and not a minor point.

The original 2010 paper in Chinese (http://www.emdrive.com/NWPU2010paper.pdf) says (my translation)

Quote
The microwave electromagnetic field of charged particles , if present , due to the electromagnetic force

The "if present" seems to have been translated to "if it consists of".  Either way, "If present" or "if it consists of" is a big if.   We have to understand whether this condition is met, and if so, what are these charged particles.

Are the authors considering charged particles to be present in the empty cavity?

In essence are the authors effectively considering virtual charged particles like the QV of Dr. White ?

Or are the authors considering having ionized air inside the cavity ?
(one example:  http://www.jpier.org/PIERM/pierm26/20.12101201.pdf  )

« Last Edit: 05/25/2015 03:10 PM by Rodal »

#### WarpTech

• Full Member
• Posts: 1223
• Do it!
• Vista, CA
• Liked: 1290
• Likes Given: 1740
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #194 on: 05/25/2015 02:29 PM »

Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?

I would go for an old fashioned soldering.  Why introduce another unknown variables caused by the glue?

BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.

Thanks for the comment.

I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.

As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.

That epoxy is not electrically conductive, is it? It's for pipes, not circuits so the electrical connection for currents to flow from end plates to side walls may be compromised. Try this;

« Last Edit: 05/25/2015 02:32 PM by WarpTech »

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #195 on: 05/25/2015 02:40 PM »

Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?

I would go for an old fashioned soldering.  Why introduce another unknown variables caused by the glue?

BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.

Thanks for the comment.

I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.

As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.

That epoxy is not electrically conductive, is it? It's for pipes, not circuits so the electrical connection for currents to flow from end plates to side walls may be compromised. Try this;

As mentioned I have silver epoxy and will be using it as the 1st 2 layers, then using the Copper/Metal epoxy for an overcoat. My experience with silver epoxy is that it doesn't have a lot of strength and can't be replied on to generate a physically strong joint.

Note Shawyer used epoxy to attach the side Rf fitting in the 1st Experimental unit as well it seems on the side wall joint and part of the flange joint.
« Last Edit: 05/25/2015 02:41 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

#### zaphod_vi

• Member
• Posts: 9
• UK
• Liked: 9
• Likes Given: 0
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #196 on: 05/25/2015 02:56 PM »

Quote
What the EmDrive thruster does is to produce a force, which we call the thrust, in one direction. This is a force that you can measure. If you put your hand against the end plate that's producing the thrust you'll feel it pushing against you. And, as with all machines that follow Newton's principles, it will therefore accelerate in the opposite direction. So this is not a reactionless thruster, because those things just don't exist outside of science fiction, but it is a propellantless thruster.

This behaviour with a force being felt from the "thrusting" end plate is also, assuming it is large enough, consistent with pressing on a bend in space time.

If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.

Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.

On a separate note, is it correct to say that the drive, as described by Shawyer has a duty cycle. That is it behaves like a pulse jet with bursts of thrust (v1 doodlebug). If so, is there experimental data to confirm this, or is the duty cycle so fast that it gets averaged out in measurement.

#### WarpTech

• Full Member
• Posts: 1223
• Do it!
• Vista, CA
• Liked: 1290
• Likes Given: 1740
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #197 on: 05/25/2015 03:16 PM »
...I also think I found a (minor?) error in the 2013 paper. In my estimation, equations 4 and 6 are correct. Where I disagree is that her premise is that there are charged particles in the volume, and then on equations 7 and 8, she removes the particle momentum density and the energy density of the field, for no apparent reason and then IMO, she abruptly ends the section....
Can you please elaborate why you think this is just a minor error by Prof. Yang and her co-authors?

(And by the way, I am looking at the 2010 paper, not the 2013 paper, in my comments below)

They write (2010 paper, translation page 4,  original page 28)

http://www.emdrive.com/NWPU2010translation.pdf
Quote
If the microwave electromagnetic field consists of charge particles, due to the
electromagnetic force, the charge particles can travel within the electromagnetic
field, so the charge particles can acquire energy and momentum from the
electromagnetic field. This indicates that electromagnetic field have energy and
momentum.

The microwave electromagnetic field inside the cavity is composed of photons (at microwave frequencies), which as we all know, have no charge whatsoever.  So the microwave electromagnetic field does not consist of charge particles.  This is the difference between Greg Egan's equations http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html, who finds no net thrust force, since he doesn't consider this term at all.

If there are any charges and currents, they are only present in the copper metal (translation says "brass"), and not inside the empty microwave cavity.  This seems to me a major issue, and not a minor point.

EDIT: The original in Chinese says (my translation)

Quote
The microwave electromagnetic field of charged particles , if present , due to the electromagnetic force

The "if present" seems to have been changed in the translation to "if it consists of".  Either way, "If present" or "if it consists of" is a big if.   We have to understand whether this condition is met, and if so, what are these charged particles.

Are the authors considering charged particles to be present in the empty cavity?

In essence are the authors effectively considering virtual charged particles like the QV of Dr. White ?

Or are the authors considering having ionized air inside the cavity ?

All good points. I believe she is trying to facilitate using Maxwell's equations by imagining there are particles inside the volume. Maxwell's equations are difficult, this is a crutch. Where she is making her mistake is that there actually are charged particles inside the volume, (besides air) they are not imaginary, they are confined to within the skin effect depth of the metal. The skin effect is inside the volume of integration for the Divergences, and it contains both positive and negative charges. Typically, we ignore the force acting on the lattice ions, since their mass is so much greater than the electrons, but they are there and they do scatter, vibrate and transfer momentum from the field to the frustum.

Unfortunately, she does not elaborate on the actual expressions of E and H, that would depend on the geometry, attenuation, phase, etc... she leaves that to the results table of her FEA. But the force equation she ends up with is still the correct equation. Its correctness, as always, depends on the accuracy of what you plug-in for E and H at the boundary, and the duty cycle of the power consumption. Therefore, if you know what to plug in, it's only a "minor" issue in her example and explanation, not in the actual FEA which is supposedly a realistic simulation of a brass cavity.

#### Rodal

• Senior Member
• Posts: 5834
• USA
• Liked: 5901
• Likes Given: 5249
##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #198 on: 05/25/2015 03:25 PM »
...As mentioned I have silver epoxy and will be using it as the 1st 2 layers, then using the Copper/Metal epoxy for an overcoat. My experience with silver epoxy is that it doesn't have a lot of strength and can't be replied on to generate a physically strong joint...
The silver epoxy has a film thickness dependent conduction behavior (due to the percolation behavior of the conductive particles and the viscosity of the epoxy).  The resistivity levels are reduced as the adhesive film thickness increases. Conversely, when the thickness is reduced significantly, a significant increase in resistivity is observed coupled with a significant increase in the slope of the resistivity-thickness curve.  On the other hand, as the thickness increases, the strength decreases, mainly because the residual stresses are larger with larger layer thickness (the epoxy is stress free near the cure temperature, which is much higher than room temperature).  So, getting it right is an art
« Last Edit: 05/25/2015 03:42 PM by Rodal »

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #199 on: 05/25/2015 03:26 PM »

Quote
What the EmDrive thruster does is to produce a force, which we call the thrust, in one direction. This is a force that you can measure. If you put your hand against the end plate that's producing the thrust you'll feel it pushing against you. And, as with all machines that follow Newton's principles, it will therefore accelerate in the opposite direction. So this is not a reactionless thruster, because those things just don't exist outside of science fiction, but it is a propellantless thruster.

This behaviour with a force being felt from the "thrusting" end plate is also, assuming it is large enough, consistent with pressing on a bend in space time.

If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.

Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.

On a separate note, is it correct to say that the drive, as described by Shawyer has a duty cycle. That is it behaves like a pulse jet with bursts of thrust (v1 doodlebug). If so, is there experimental data to confirm this, or is the duty cycle so fast that it gets averaged out in measurement.

Shawyer did show in the superconducting engine that each of the 8 cavities would only be excited, in series, for a fraction of one TC. So a duty cycle of 1:8 with excitation only lasting for less than 1 TC. As it takes 5 TC to fully change, with such a high Q, the time to charge may be way too long.

Shawyer made comment on charge time and duty cycle. Page 5 of attached.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Tags: