Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1800168 times)

Online Rodal

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Neither of the photos (the table top nor the vacuum chamber) seem to indicate an offset, although it is a bit difficult to tell.

Hi all, been lurking for several months now, just dipping a toe in...

If you look at the thermal imaging pictures on page four of the Tajmar paper, the right-most image shows a top-down view. Looks pretty clear that the waveguide is centered on the axis of the frustum...

Party on...

Thank you for the observation.  Concerning the geometrical placement of the waveguide you are correct:   Todd "WarpTech" was correct that the waveguide longitudinal central axis seems to be somewhat radially located from the center of the EM Drive.

But this image actually makes the case for effective asymmetry much stronger: as what matters is the electromagnetic effect and the image shows that the temperature is not rotationally symmetric !

The high temperature (shown by yellow-orange) extends to less than 40 degrees to the left, but it extends to over 90 degrees to the right.

There is a very strong rotational asymmetry shown by the thermal image:  whether the forces are due to thermal effects or due to electromagnetic fields that result in this asymmetry, that this asymmetry would produce a side force would not at all be surprising

_________________

I enclose strictly for discussion, research and illustration purposes Fig. 3 b page 4 of Tajmar et.al. analysis for comparison purposes to address the above question


 “…for purposes such as criticism, comment, news reporting, scholarship, or research…” under US Fair Use

http://fairuse.stanford.edu/overview/fair-use/what-is-fair-use/

This is the  American Institute of Aeronautics and Astronautics link to Martin Tajmar's et.al. paper, that should be obtained from the American Institute of Aeronautics and Astronautics:

Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects  M. Tajmar and G. Fiedler
51st AIAA/SAE/ASEE Joint Propulsion Conference

http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

« Last Edit: 07/28/2015 11:44 PM by Rodal »

Offline demofsky

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Neither of the photos (the table top nor the vacuum chamber) seem to indicate an offset, although it is a bit difficult to tell.

Hi all, been lurking for several months now, just dipping a toe in...

If you look at the thermal imaging pictures on page four of the Tajmar paper, the right-most image shows a top-down view. Looks pretty clear that the waveguide is centered on the axis of the frustum...

Party on...

Thank you for the observation.  Concerning the geometrical placement of the waveguide you are correct:   Todd "WarpTech" was correct that the waveguide longitudinal central axis seems to be somewhat radially located from the center of the EM Drive.

But this image actually makes the case for effective asymmetry much stronger: as what matters is the electromagnetic effect and the image shows that the temperature is not rotationally symmetric !

The high temperature (shown by yellow-orange) extends to less than 40 degrees to the left, but it extends to over 90 degrees to the right.

There is a very strong rotational asymmetry shown by the thermal image:  whether the forces are due to thermal effects or due to electromagnetic fields that result in this asymmetry, that this asymmetry would produce a side force would not at all be surprising
.....

Another thing to note is that there are high temperatures around the seam between the fustrum and the end plate.  Most likely hot gasses leaking from the fustrum.  Leaks may play an important role in experimental artifacts given the low thrust levels expected from these experiments to date - especially those in a vacuum.

Edits: Typo
« Last Edit: 07/29/2015 02:08 AM by demofsky »

Offline WarpTech

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Neither of the photos (the table top nor the vacuum chamber) seem to indicate an offset, although it is a bit difficult to tell.

Hi all, been lurking for several months now, just dipping a toe in...

If you look at the thermal imaging pictures on page four of the Tajmar paper, the right-most image shows a top-down view. Looks pretty clear that the waveguide is centered on the axis of the frustum...

Party on...

Thank you for the observation.  Concerning the geometrical placement of the waveguide you are correct:   Todd "WarpTech" was correct that the waveguide longitudinal central axis seems to be somewhat radially located from the center of the EM Drive.

But this image actually makes the case for effective asymmetry much stronger: as what matters is the electromagnetic effect and the image shows that the temperature is not rotationally symmetric !

The high temperature (shown by yellow-orange) extends to less than 40 degrees to the left, but it extends to over 90 degrees to the right.

There is a very strong rotational asymmetry shown by the thermal image:  whether the forces are due to thermal effects or due to electromagnetic fields that result in this asymmetry, that this asymmetry would produce a side force would not at all be surprising
.....

Another thing to note is that there are high temperatures around the seam between the fustrum and the end plate.  Most likely hot gasses leaking from the fustrum.  Leaks may play an important role in experimental artifacts give the low thrust levels expected from these experiments to date - especially those in a vacuum.

35C - 40C is not that hot for copper conductor. Granted, heat will allow magnetic flux to escape because it implies there is a voltage drop there. Wherever a voltage drop appears on the metal, the Volt-seconds product (integral) is the flux escaping.
Todd
 

Online Rodal

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The 35 to 40 deg C scaling is predicated on the accuracy of the emissivity assumed (was it correctly set for the area being thermally imaged ?), the accuracy of the thermal imaging camera (was it at the correct distance from the object being scanned, etc. ?) and it is only good as an average for the time interval during which the thermal image was taken.
« Last Edit: 07/29/2015 01:48 AM by Rodal »

Online SeeShells

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Between running out side to the shop, trying to follow the conference, phone work, email, doing some research, the one thing I loved stopping for was DrBagelBites running commentary, simply beautiful. You're my rock star sir.

Shell

Added: The next best was RFMWGUY's demo.
« Last Edit: 07/29/2015 02:17 AM by SeeShells »

Online SeeShells

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Wow, what an exciting day! Live blog from Dr BB, classical theorists slinging "crap" in their not-so-well thought out responses, noobs, posting and departing, and me finishing my assembly so I can celebrate the day with a video of my first thermal test of NSF-1701 under power!

Time to savor an adult beverage...been in the shop all day and I have some reading to catch up on ;)

THAT WAS AWESOME!

Very nice work. I noticed there was some arcing on the magnetron but not much. Very good work for the first run.

Did you get a USB VNA or SA? What are you going to use to determine if you hit frequency? Inquiring minds want to know.

Shell

Online Rodal

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Wow, what an exciting day! Live blog from Dr BB, classical theorists slinging "crap" in their not-so-well thought out responses, noobs, posting and departing, and me finishing my assembly so I can celebrate the day with a video of my first thermal test of NSF-1701 under power!

Here it is guys and gals:

Time to savor an adult beverage...been in the shop all day and I have some reading to catch up on ;)

Rfmwguy:  the geometry of NSF-1701 is much more sensitive to RF feed placement (whether at the big end or the small end) than Yang/Shell.  Thus NSF-1701 presents itself as an excellent testbed to learn what's gong on.

It is very, very important that you plan to run several experiments with NSF-1701 with the RF feed near the big end and with the RF feed near the small end. 

According to the computer runs NSF-1701 will be very interesting in this regard, since the behavior is quite different.

I hope to have the time to post the details tomorrow.

I think this sensitivity is related to the distance from the small base to the vertex of the cone, see

http://emdrive.wiki/Experimental_Results

                               r1

Yang                        0.6953 m               
NASA Eagleworks     0.3111 m
Shawyer Demo        0.2260 m
Shawyer Flight Thr   0.1764 m



I think that the smaller r1 the better: the closer to the apex of the cone, as shown by Zeng and Fan, and Todd WarpTech

Yang's geometry is more than twice as far.
« Last Edit: 07/29/2015 02:49 AM by Rodal »

Offline deltaMass

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I got a kick out of two of the snippets Dr. BB posted as Tajmar was speaking. Funny to hear a scientist say stuff like this.
"So I went to the hardware store and bought a microwave."
and later...
"I had to go to the supermarket and pick up some vegetable oil."

Was it a presentation, or was it a cooking show?  ;D

Offline jknuble

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(Reposting for posterity with the direct links to the paper removed:)

I see three pieces of evidence from Tajmar's paper that high power RF effects such as corona breakdown, multipaction (or simple out-gassing) could be incinerating the materials in the cavity and generating particles thus creating the observed thrust:

1) For the latest results, the fact that the thrust continues to exist after the removal of RF power and correlates well to temperature indicates to me that particle generation is due to thermal effects (such as burning an adhesive).

From the paper:
"The implementation of all isolation methods (thermal, magnetic, air circulation block) resulted in the cleanest measurement with an expected behavior such that the thrust appeared after turn-on, then steadily increased until power turn off. It then remained there and slowly decreased as the EMDrive cooled down. "

2) The second piece of evidence comes from my suggestion here: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1367663#msg1367663 that the cavity be disassembled and inspected for the damaging effects of the above phenomenon to verify if they are occurring or not.

It seems this was done and the damage was found:
" Indeed we measured that our Q factor was reduced to only 20.3 – probably due to the fact that our inner surfaces were now much more oxidized compared to the start of our test campaign after a visual inspection. "
The visual evidence confirms that the effects I've mentioned are occurring.

3) Further, taking a look at the thermal imager pictures in Figure 3 it appears the seam of the cylindrical cavity is the hottest point which is where you would expect these effects to occur as was also suggested here http://forum.nasaspaceflight.com/index.php?topic=36313.msg1367663#msg1367663

-JK

Offline WarpTech

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I just figured out that apparently, Dr. McCulloch's formula, Dr. @Notsosurofit's formula and my own formula using the cylindrical approximation, all amount to the same basic force. This force is proportional to, the change in energy from the small end to the big end, divided by the length, i.e, delta_E/delta_z.

Where the 3 formula differ, is in how this force is multiplied by the group velocity v/c or (v/c)2, and what formula is used for the group velocity.

Dr. McCulloch skips this concept entirely and simply inputs the energy as Power x time, using the speed of light and the length. No consideration of group velocity at all. He simply uses m*c^2 where m is derived by his theory.

Dr. @Notsosureofit's formula, after completing the square and factoring the difference between two frequencies squared. The basic force above is multiplied by the average cut-off (I know @Rodal) over the input frequency:

(ws + wb)/2*w

This was surprising and interesting. Note, that when the frequency is less than the average cut-off, (i.e, becoming evanescent) this factor is > 1.

My formula, without Zeng and Fan results in a factor that also depends on the frequency, but has a much larger value near the cut-off:

(w + wb)/(w - wb),

ws and wb, are the resonant or cut-off frequencies at each end respectively.

These factors are each multiplied by delta_E/delta_z, where delta_z is the length, and delta_E is the frequency shift from small end to big end. There is one more factor, and that is the impedance plots in Zeng and Fan for a cone. It is somewhere between the "infinite" value of my formula and the subtle value of @Notsosureofit's formula.

It's late, I hope I didn't make any errors, I'll be back. 8)
Todd

Todd you also need to consider Shawyers equation, that Tajam says correctly predicted his Force, which is based on Shawyer's Df that factors in the cutoff at each end of the tapered cavity to produce the guide wavelengths at each end. The delta of the end plate guide wavelengths represents the delta of the end plates forces.

TT, the reason I did not include Shawyer's formula here, is that unlike the three I mentioned above that all have a common basic force, which is the difference between two energy states, divided by the length. Shawyer uses the difference between two forces. I have yet to resolve his equation to be "similar" to the other 3.
Thanks.


EDIT: Actually, strike that. If I take the equations one level higher. Then all four equations, including Shawyer's, are the "Rocket Equation". Where each equation differs is in how the "thrust-to-power" ratio is calculated. I think I have the answer, and it is back where I started from when I joined this conversation and I mentioned how momentum behaves in the PV Model. The question is: How to get around the fact that the group velocity must be faster than light in order to have thrust-to-power greater than a photon rocket?

The answer I have is that, if the speed of light has been slowed down, then so has the group velocity and the phase velocity. What we need is not for the group velocity to be faster than light. What we need is for the phase velocity to be slower than light, which is true when the refractive index K >> 1.

vg*vp = c2   =>

(vg/K)*(vp/K) = (c/K)2

As long as (vp/K) < c in free space, then we have a thrust to power ratio better than a photon rocket. :) Nothing needs to exceed c!
Todd
« Last Edit: 07/29/2015 03:44 AM by WarpTech »

Offline Stormbringer

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Re Post #5473 by  Prunesquallor

Laser pulses that are shot at the reflectors that the Apollo astronauts left on the moon start out at a diameter of 3.5 m.  Atmospheric effects cause divergence to about 2 km at the moon.

Edit: tei-po

There are recent developments that greatly diminish atmospheric antenuation. Of course probably everyone knows about atmospheric turbulence sensing beams or optical guide stars. But fairly recently it was found that if you precede a main laser pulse by a very short time with laser beams bracketing the space the main beam will travel it holds the beam focus together far longer also retaining much more of it's initial power and longer range than formerly possible. Also preceding the main beam by a precursor beam creates a vacuum channel through which the main beam can travel without encountering stuff that can weaken or cause the beam to diverge. of course the latter  probably only applies to short duration beam shots instead of persistent beams.

edit: darn nested quotes.
« Last Edit: 07/29/2015 04:09 AM by Stormbringer »
When antigravity is outlawed only outlaws will have antigravity.

Offline WarpTech

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(Reposting for posterity with the direct links to the paper removed:)

I see three pieces of evidence from Tajmar's paper that high power RF effects such as corona breakdown, multipaction (or simple out-gassing) could be incinerating the materials in the cavity and generating particles thus creating the observed thrust:

1) For the latest results, the fact that the thrust continues to exist after the removal of RF power and correlates well to temperature indicates to me that particle generation is due to thermal effects (such as burning an adhesive).

From the paper:
"The implementation of all isolation methods (thermal, magnetic, air circulation block) resulted in the cleanest measurement with an expected behavior such that the thrust appeared after turn-on, then steadily increased until power turn off. It then remained there and slowly decreased as the EMDrive cooled down. "

2) The second piece of evidence comes from my suggestion here: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1367663#msg1367663 that the cavity be disassembled and inspected for the damaging effects of the above phenomenon to verify if they are occurring or not.

It seems this was done and the damage was found:
" Indeed we measured that our Q factor was reduced to only 20.3 – probably due to the fact that our inner surfaces were now much more oxidized compared to the start of our test campaign after a visual inspection. "
The visual evidence confirms that the effects I've mentioned are occurring.

3) Further, taking a look at the thermal imager pictures in Figure 3 it appears the seam of the cylindrical cavity is the hottest point which is where you would expect these effects to occur as was also suggested here http://forum.nasaspaceflight.com/index.php?topic=36313.msg1367663#msg1367663

-JK

Just some suggestions...

TO THE MEEPERS; This is WHY we need an accurate simulation that shows what happens when the power is turned off. If the losses are small, the resonant wave will persist for some period of time until all the energy decays. We need to know what that decay time really is. In fact, I would predict that the thrust goes up the faster it decays. Thrust persisting after it is turned off is to be expected. The question is, how long does it take for the internal stored energy to dissipate? The higher the Q, the longer it will take to discharge.

DIY's; It would be a good idea to monitor what is going on inside the frustum at all times. Such that you can determine the difference between a hot frustum, and one that is still charged with resonant energy. If there is persistent force after the power is turned off but there is nothing going on inside it, then you know you have an artifact. Just because it's hot doesn't mean it's an artifact. The temperature will follow the power dissipation. As it declines so will the temperature. The two are well correlated, so the fact that the thrust persists and decays with the temperature is to be expected. This alone is not an indication of an artifact. The artifact would be only IF there is no energy inside the frustum doing the work. Still, I would be hard pressed to believe that thermal radiation can exert forces at least an order of magnitude larger than a photon rocket.

Regarding arcing, breakdown, etc. Today's video from @rfmwguy did not appear to me to show arching. Shell said she saw it, but I think that what looks like arcing is actually his laser on the thermal probe reflecting off the magnetron. I did not see arcing. Perhaps @rfmwguy will update us in the morning regarding this.
Todd

Offline Nascent Ascent

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I got a kick out of two of the snippets Dr. BB posted as Tajmar was speaking. Funny to hear a scientist say stuff like this.
"So I went to the hardware store and bought a microwave."
and later...
"I had to go to the supermarket and pick up some vegetable oil."

Was it a presentation, or was it a cooking show?  ;D

Deja Vu...

So after stopping at a hardware store for a C-clamp on the way to the hearing...Feynman said...

".....I took this stuff that I got out of your seal and I put it in ice water, and I discovered that when you put some pressure on it for a while and then undo it, it does not stretch back...."

Heh heh
“Why should we send people into space when we have kids in the U.S. that can’t read”. - Barack Obama

Offline aero

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You know that I am about as pro real thrust as it can get, but if its an artefact I want to find it. So I had a thought re. Tajmar's measured lingering thrust dissipating in seemingly correlation to the hot magnetron cooling.

Have the folks using magnetrons all used New magnetrons? That is, tubes that have not yet been burned in? If so then the inside of those things is likely be "dirty." Covered with a sheen of cleanser if not light oil. Not very dirty but what ever amount is burning off could travel down the waveguide to the cavity and leak out, or deposit on the inside of the relatively cool and polished copper.  EW didn't use a magnetron, and still got a force signal. Is there a sneak path for hot stuff to come out of the waveguide into the cavity in that case?

Retired, working interesting problems

Online SeeShells

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(Reposting for posterity with the direct links to the paper removed:)

Just some suggestions...

TO THE MEEPERS; This is WHY we need an accurate simulation that shows what happens when the power is turned off. If the losses are small, the resonant wave will persist for some period of time until all the energy decays. We need to know what that decay time really is. In fact, I would predict that the thrust goes up the faster it decays. Thrust persisting after it is turned off is to be expected. The question is, how long does it take for the internal stored energy to dissipate? The higher the Q, the longer it will take to discharge.

DIY's; It would be a good idea to monitor what is going on inside the frustum at all times. Such that you can determine the difference between a hot frustum, and one that is still charged with resonant energy. If there is persistent force after the power is turned off but there is nothing going on inside it, then you know you have an artifact. Just because it's hot doesn't mean it's an artifact. The temperature will follow the power dissipation. As it declines so will the temperature. The two are well correlated, so the fact that the thrust persists and decays with the temperature is to be expected. This alone is not an indication of an artifact. The artifact would be only IF there is no energy inside the frustum doing the work. Still, I would be hard pressed to believe that thermal radiation can exert forces at least an order of magnitude larger than a photon rocket.

Regarding arcing, breakdown, etc. Today's video from @rfmwguy did not appear to me to show arching. Shell said she saw it, but I think that what looks like arcing is actually his laser on the thermal probe reflecting off the magnetron. I did not see arcing. Perhaps @rfmwguy will update us in the morning regarding this.
Todd
I watched it again frame by frame when I thought I saw arcing and your quite right it was the laser flashing off the magnetron or wires. I would suspect if he had a high Q he might see arcing as the energy increases. We still need to see if he can calculate the Q with a VNA or whatever he uses. Exciting day all around.
Shell

Offline tchernik

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You know that I am about as pro real thrust as it can get, but if its an artefact I want to find it. So I had a thought re. Tajmar's measured lingering thrust dissipating in seemingly correlation to the hot magnetron cooling.

Have the folks using magnetrons all used New magnetrons? That is, tubes that have not yet been burned in? If so then the inside of those things is likely be "dirty." Covered with a sheen of cleanser if not light oil. Not very dirty but what ever amount is burning off could travel down the waveguide to the cavity and leak out, or deposit on the inside of the relatively cool and polished copper.  EW didn't use a magnetron, and still got a force signal. Is there a sneak path for hot stuff to come out of the waveguide into the cavity in that case?

Good thinking, we better find the mundane source of the thrust soon and then move on. To be honest, I'm really bummed right now with all this affair. Because it is showing the very same trend other similar approaches (e.g. Woodward's ME thrusters) have shown in the past: starting with wild claims of scalable propellentless Newtons, the thrust tends to become smaller and smaller when the testing conditions improve, until it is virtually the same as background noise or a photon rocket. This was a 700 watts Emdrive for goodness sake, and it shows an even tinier amount of thrust.

Right now only a vacuum-tested replication by NASA's EW producing well above 100 micro Newtons will cheer me up about this.

Tajmar's experiment was not a negative result per se, but it was another step in a déjà-vu narrative, recurrent with these kind of thrusters.

Offline R.W. Keyes

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I am also concerned that this emdrive seems to have been thrown together. I'd have proved the magnetron first.

I don't understand why there's not more effort given towards the production of a device with higher Q. I am not asking for a superconductor cavity, but can it at least be polished? not hand-soldered? Made of decently pure copper?

Offline TheTraveller

It looks like the only person in this world other than Shawyer that likes Shawyer's theory is TheTraveller

We have McCulloch and now Tajmar strongly against Shawyer's theory

Interesting that Shawyer's theory and equations did accurate predicted the Force Tajmar measured.

My spreadsheet, based on Shawyer's theory of variable guide wavelength / group velocity at the 2 end plates did predict the Tajmar cavity resonance at 2.45GHz in TE111 mode.

So far have not seen another theory & set of equations that can correctly predict Force generation, resonant mode and resonate frequency.
« Last Edit: 07/29/2015 05:49 AM by TheTraveller »
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Offline deltaMass

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You know that I am about as pro real thrust as it can get, but if its an artefact I want to find it. So I had a thought re. Tajmar's measured lingering thrust dissipating in seemingly correlation to the hot magnetron cooling.

Have the folks using magnetrons all used New magnetrons? That is, tubes that have not yet been burned in? If so then the inside of those things is likely be "dirty." Covered with a sheen of cleanser if not light oil. Not very dirty but what ever amount is burning off could travel down the waveguide to the cavity and leak out, or deposit on the inside of the relatively cool and polished copper.  EW didn't use a magnetron, and still got a force signal. Is there a sneak path for hot stuff to come out of the waveguide into the cavity in that case?
Just to be sure I understand your thesis here; the presence of this light oil, having trickled into the cavity, will cause the cavity temperature to maintain longer than if it were absent, due to the oil's heat capacity?

Maybe. But what is more salient for me than the cause of the thermal "run-on" is its magnitude and duration. It had magnitude comparable to the putative thrust, and a duration which roughly corresponded to the cooling time of the magnetron itself. The disturbing thing for me here is that, as a result of the magnitude of the thermal effects, the SNR was in the toilet. Which means the fidelity of the force measurement is in doubt. I say this knowing full well that the force signal had a prompt onset.
 

Offline martinc

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I did promise not to pollute this thread but i had an idea i can't resist putting out (my post frequency will be very low though)..
how significant is frustum shape really? consider the cannae drive.. (and why use a material that degrades reflectivity over time but that's another question!)
my idea is to consider physical thrust generation one kind of experiment, but only one..
another would be to not monitor thrust at all but to try to observe what's going on inside the frustum
now here's a simple, simple idea..
a frustum with a window = a stock microwave oven
it would be possible to fix reflective items inside the oven body to create dynamic frustum shapes and try to 'tune' it this way. meanwhile inject either particulate or visible vapour through small holes and try to see if anything can be observed this way. it may not work, even if the Em Drive does generate true thrust it depends on the mechanism by which it does it but it could be worth a try
there is a suggestion in Tajmar there is a 'field' there due to thrust continuing on a while, so it would be this field that would be the object of these experiments. any discovery at all, could then be replicated properly in a lab
it just seems to me that these current experiments are all being done with the object of trying to generate thrust which is jumping ahead somewhat, and conditions inside the frustum could be a better place to start...
i'm thinking of trying this myself, a lot safer as well!
if the existence of the 'field' could be proven that would be evidence for the origin of the thrust
if there's any merit in this idea it could be taken off this thread so as not to pollute it as the wonderful discussion here is one of the best i've seen online (i made a small blog site here if anyone wants to contribute http://emdrivemicrowavelab.blogspot.com)

martin

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