Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1803701 times)

Offline ThinkerX

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I am getting the impression that some of the in progress DIY efforts here may actually be better designed than the Tajmar device.  Given this, I am wondering if a full, proper redesign would show greater results in a vacuum.

Offline TheTraveller

Anybody know anything about SuperFish?

http://www.lanl.gov/projects/feynman-center/technologies/software/poisson-superfish.php

I know that the official download site is down at the moment. I was able to find a mirror site, so if anyone wants to play around with it, you can use the link:
http://hallaweb.jlab.org/12GeV/SoLID/download/field/PoissonSuperfish_7.18.exe

Thanks for the link. Most appreciated.

Have you any experience with SuperFish? Read it is designed to sim axisymmetric cavities?
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Online aero

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I am wondering if there is specific detailed information regarding the lateral force detected by Tajmar. We know that it was not in the cavity longitudinal direction. Was it for sure in the wave guide axial direction or was it in the third direction, perpendicular to both the cavity axis of rotation and the wave guide axial direction? If so, then we have nothing to explain it with, per my understanding, (the off center rf input not considered) but if it was in the wave guide axial direction, then ---

The magnetron is pumping about 700 watts into the wave guide which is passing about 660 (??) watts into the frustum. Using the photon rocket equation, 660 watts at 1/c per watt gives about 2.2 micro-Newtons. If there is any resonance within the wave guide, or between the frustum and wave guide --- well, it wouldn't take much Q give a force consistant with the force Tajmar detected.

An afterthought -- If there is anything to my idea, then it wouldn't take a lot of design work to fix things so that you could rotate your space ship using the main engines! Of course if that lateral force is simply the natural order of things, your space ship will fly in circles unless you compensate for the lateral force.
« Last Edit: 07/27/2015 04:10 AM by aero »
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Offline cee

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The Tagmar setup is a bit different than this setup in that it looked like the Magnetron was mounted on the broadside of the waveguide, probably a E-probe 1/4 Lambda from the endwall, that coupled to the resonant iris which then reflected a matched source to the frustrum sidewall which should then excite a TM mode in the frustrum tranverse axis which is at approx a right angle to  rectangular waveguide. The diagram which shows a similar setup with the E-probe in the rectangular wave guide end wall will launch a TM mode which will be matched by the iris and reflect a matched impedance to the frustrum wall but should excite a TE mode in the frustrum. It will interesting to see his mode data.

Offline cee

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This short length, constant diameter, cylindrical step out ("retraction" size of the cover depth) design also seems to eliminate the need for spherical end plates, which would be a really big win.

Yes but the Chinese used a noisy 1000W magnetron, which has AM and FM modulation over a wider bandwidth than your cleaner solid-state 100W RF amp. I remember Shawyer told you to use a magnetron with flat end plates, but a narrow-band emitter with spherical ends.

Correct.

But the new build Prof Yang has shared allows using flat end plates to obtain a Q of 117,500 by using short constant diameter set backs as attached. I assume the set backs convert a spherical wavefront into a planar wavefront in both directions.

When using a tapered waveguide to connect different diameter cylindrical waveguides this is what happens. Planar going in, spherical inside the tapered section and planar when emerging into the opposite side constant diameter cylindrical section.

I see this as a major advancement in EMDrive frustum design.

My 1st build has now altered to be able to experiment with this new structure as attached. Double ended tuning with sliding end plates inside constant diameter sections. Shawyer did do this for the small end in his Demonstrator EMDrive and repeated it with the Tajmar EMDrive. Both magnetron driven.

If this setup can eliminate the need for spherical end plates and still deliver an unloaded Q of 117,500, bring it on.

BTW to those "group velocity is different at each end of the frustum" doubters, wonder what the group velocity will be in those constant diameter sections? Would suggest it will be the group velocity as per the constant diameter circular waveguide equations. Which means Cullen, Shawyer & Prof Yang are correct.

This is very interesting.  However, something twigged prompting me to realize that we now have a fustrum and two cylinders!!  This must introduce some very interesting dynamics to an already complex situation.  Evanescent waves must be going crazy in there.

Seeing a meep simulation of one of our standard models with these extensions would be very, very illuminating.
The Tagmar setup is a bit different than this setup in that it looked like the Magnetron was mounted on the broadside of the waveguide, probably a E-probe 1/4 Lambda from the endwall,which will launch a TE mode that is coupled to the resonant iris which then reflected a matched source to the frustum sidewall which should then excite a TM mode in the frustum transverse axis which is at approx a right angle to  rectangular waveguide. The diagram which shows a similar setup with the E-probe in the rectangular wave guide end wall will launch a TM mode which will be matched by the iris and reflect a matched source to the frustum wall but should excite a TE mode in the frustum. It will interesting to see his mode data.

Offline lmbfan

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A post over on reddit attributes the thrust to a phenomenon called sputtering.  I was wondering how valid this interpretation is.  It appears to depend on oxidation, which seems unlikely in a vacuum.  Link:

http://www.reddit.com/r/Futurology/comments/3emk49/direct_thrust_measured_from_propellantless_em/cthg9uo

Offline CraigPichach

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We need to test an EMDrive at 100kW to ensure that it is not sputtering... but someone needs to calculate dimensions for TM010 at 915MHz. There is some data that is not sputtering with respect to NASA needing an HDPE dielectric at low power levels while the copper/air acted as a dielectric at higher power; if is sputtering than why the difference?

Also apart from the availability of small microwave magnetrons I don't know why we are looking at 2.45GHz since that is restricting you to small ~10kW power levels. There are no 2.45GHz 100kW magnetrons unfortunately. Highest available frequencies are like 940MHz and 930MHz is easily available. Also need to worry about how the isolator waterload would impact the unit; I would assume that since we are looking for resonance the lost RF wouldn't be a concern.

Offline TheTraveller

A post over on reddit attributes the thrust to a phenomenon called sputtering.  I was wondering how valid this interpretation is.  It appears to depend on oxidation, which seems unlikely in a vacuum.  Link:

http://www.reddit.com/r/Futurology/comments/3emk49/direct_thrust_measured_from_propellantless_em/cthg9uo

The Tajmar cavity was sealed. The oxidation INSIDE the cavity was what happens to copper as you heat it in a oxygen atmo. Is why my cavity will be sealed and N2 filled at 1/2 atmo pressure.

As for his other statements, he needs to reread the paper.
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Online demofsky

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....

Also apart from the availability of small microwave magnetrons I don't know why we are looking at 2.45GHz since that is restricting you to small ~10kW power levels. There are no 2.45GHz 100kW magnetrons unfortunately. Highest available frequencies are like 940MHz and 930MHz is easily available. Also need to worry about how the isolator waterload would impact the unit; I would assume that since we are looking for resonance the lost RF wouldn't be a concern.

This has been discussed in the past.  The actual magnetrons are fairly inexpensive. However, any fustrum would have to be water cooled along with the magnetron  Look at all the handwringing over the impact of the wiring in Tajmar's experiment.  Imagine what would be required for water cooling plumbing at the 100kW levels!

On the whole it was felt that the engineering was significant and that good work could be done with an oven magnetron before moving on to higher levels after there is consensus on how to design and tune a fustrum.
« Last Edit: 07/27/2015 06:06 AM by demofsky »

Online demofsky

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This short length, constant diameter, cylindrical step out ("retraction" size of the cover depth) design also seems to eliminate the need for spherical end plates, which would be a really big win.

Yes but the Chinese used a noisy 1000W magnetron, which has AM and FM modulation over a wider bandwidth than your cleaner solid-state 100W RF amp. I remember Shawyer told you to use a magnetron with flat end plates, but a narrow-band emitter with spherical ends.

Correct.

But the new build Prof Yang has shared allows using flat end plates to obtain a Q of 117,500 by using short constant diameter set backs as attached. I assume the set backs convert a spherical wavefront into a planar wavefront in both directions.

When using a tapered waveguide to connect different diameter cylindrical waveguides this is what happens. Planar going in, spherical inside the tapered section and planar when emerging into the opposite side constant diameter cylindrical section.

I see this as a major advancement in EMDrive frustum design.

My 1st build has now altered to be able to experiment with this new structure as attached. Double ended tuning with sliding end plates inside constant diameter sections. Shawyer did do this for the small end in his Demonstrator EMDrive and repeated it with the Tajmar EMDrive. Both magnetron driven.

If this setup can eliminate the need for spherical end plates and still deliver an unloaded Q of 117,500, bring it on.

BTW to those "group velocity is different at each end of the frustum" doubters, wonder what the group velocity will be in those constant diameter sections? Would suggest it will be the group velocity as per the constant diameter circular waveguide equations. Which means Cullen, Shawyer & Prof Yang are correct.

This is very interesting.  However, something twigged prompting me to realize that we now have a fustrum and two cylinders!!  This must introduce some very interesting dynamics to an already complex situation.  Evanescent waves must be going crazy in there.

Seeing a meep simulation of one of our standard models with these extensions would be very, very illuminating.
The Tagmar setup is a bit different than this setup in that it looked like the Magnetron was mounted on the broadside of the waveguide, probably a E-probe 1/4 Lambda from the endwall,which will launch a TE mode that is coupled to the resonant iris which then reflected a matched source to the frustum sidewall which should then excite a TM mode in the frustum transverse axis which is at approx a right angle to  rectangular waveguide. The diagram which shows a similar setup with the E-probe in the rectangular wave guide end wall will launch a TM mode which will be matched by the iris and reflect a matched source to the frustum wall but should excite a TE mode in the frustum. It will interesting to see his mode data.

The device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al.  It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...

Offline TheTraveller

....

Also apart from the availability of small microwave magnetrons I don't know why we are looking at 2.45GHz since that is restricting you to small ~10kW power levels. There are no 2.45GHz 100kW magnetrons unfortunately. Highest available frequencies are like 940MHz and 930MHz is easily available. Also need to worry about how the isolator waterload would impact the unit; I would assume that since we are looking for resonance the lost RF wouldn't be a concern.

This has been discussed in the past.  The actual magnetrons are fairly inexpensive. However, any fustrum would have to be water cooled along with the magnetron  Look at all the handwringing over the impact of the wiring in Tajmar's experiment.  Imagine what would be required for water cooling plumbing at the 100kW levels!

On the whole it was felt that the engineering was significant and that good work could be done with an oven magnetron before moving on to higher levels after there is consensus on how to design and tune a fustrum.

I'm sure the team at SPR and Prof Yangs team could design and build a 400N/100kW EMDrive. Give me 1 year and I could do it.

With 20 of those the IXS Clarke could be built.
« Last Edit: 07/27/2015 06:36 AM by TheTraveller »
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Online demofsky

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Another question for Tajmar is whether they used flat or spherical end plates.  The following picture seems to show a spherical end plate.

From "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


Offline dumbo

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I'm sure the team at SPR and Prof Yangs team could design and build a 100kW EMDrive. Give me 1 year and I could do it.

With 20 of those the IXS Clarke could be built.

It is fun to speculate, but I think it is still premature to consider scaling this thing up considering there is no consensus regarding how the EMDrive works, or indeed if it even works at all. Let's see some proof that we have true propellantless thrust before getting too carried away, please.

Having said that, 100kW has been done before. Doesn't the latest VASIMR run at 200kW? Portable nuclear technology also exists: https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor

The engineering challenges, while real, are definitely not a showstopper provided the EMDrive can do its part...
« Last Edit: 07/27/2015 06:51 AM by dumbo »

Offline TheTraveller

The device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al.  It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...

Yes I agree it is very the Experimental EMDrive except Shawyer got 16mNs out of his.

It took him several years to get it right. Q was 5,900 but that was because it had a dielectric inside. He used 5 magnetrons, burnt out 3 and burned a hole in a waveguide. But he got there.

His experimental data was verified by a expert Uk aerospace industry group set up by the UK gov Dept of Defense. After the experts gave him the thumbs up, the UK gov gave him the 1st grant to build the Demonstrator EMDrive and the rotary test rig.

After the UK gov again verified the data from the Demonstrator trials he got the final payment from the UK gov.
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Offline TheTraveller

Another question for Tajmar is whether they used flat or spherical end plates.  The following picture seems to show a spherical end plate.

I saw that but in other photos it appears to be more flattish than convex.

Can't really use spherical end plates with a wide band Rf source. Cavity input bandwidth would be way too narrow to accept a +-30MHz magnetron output.
« Last Edit: 07/27/2015 07:03 AM by TheTraveller »
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Offline SeeShells

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A post over on reddit attributes the thrust to a phenomenon called sputtering.  I was wondering how valid this interpretation is.  It appears to depend on oxidation, which seems unlikely in a vacuum.  Link:

http://www.reddit.com/r/Futurology/comments/3emk49/direct_thrust_measured_from_propellantless_em/cthg9uo
You can answer that question by filling the enclosed Frustum with Sulfur hexafluoride,

Sulfur hexafluoride is an inorganic, colorless, odorless, non-flammable, extremely potent greenhouse gas which is an excellent electrical insulator. SF 6 has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom.

But it is hard to keep in a perforated cavity. It is used in high power systems to prevent arcing.

Shell

 

Offline SeeShells

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A post over on reddit attributes the thrust to a phenomenon called sputtering.  I was wondering how valid this interpretation is.  It appears to depend on oxidation, which seems unlikely in a vacuum.  Link:

http://www.reddit.com/r/Futurology/comments/3emk49/direct_thrust_measured_from_propellantless_em/cthg9uo

The Tajmar cavity was sealed. The oxidation INSIDE the cavity was what happens to copper as you heat it in a oxygen atmo. Is why my cavity will be sealed and N2 filled at 1/2 atmo pressure.

As for his other statements, he needs to reread the paper.
I wonder why they just didn't silver coat it? Even if you get a little tarnish it will still be conductive. (a useful comment from a dear friend who worked on the SCSC with me)

Shell

Offline SeeShells

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....

Also apart from the availability of small microwave magnetrons I don't know why we are looking at 2.45GHz since that is restricting you to small ~10kW power levels. There are no 2.45GHz 100kW magnetrons unfortunately. Highest available frequencies are like 940MHz and 930MHz is easily available. Also need to worry about how the isolator waterload would impact the unit; I would assume that since we are looking for resonance the lost RF wouldn't be a concern.

This has been discussed in the past.  The actual magnetrons are fairly inexpensive. However, any fustrum would have to be water cooled along with the magnetron  Look at all the handwringing over the impact of the wiring in Tajmar's experiment.  Imagine what would be required for water cooling plumbing at the 100kW levels!

On the whole it was felt that the engineering was significant and that good work could be done with an oven magnetron before moving on to higher levels after there is consensus on how to design and tune a fustrum.

Very true. One simple misstep at even the thickness of a piece of paper and you could fry that costly 100kw magnetron or blow holes in the sidewalls of your Frustum or worse yet harm someone. Small steps here are the catchphrase.

Shell

Shell

Offline TheTraveller

Got it figured.

Tajmar's cavity has a measured 50MHz input bandwidth from 2.40GHz to 2.45GHz or the lower portion of the WiFi band.

Most magnetrons output in the upper half of the WiFi band, 2.45GHz to 2.50GHz range as attached.

If his magnetron output bandwidth was like that Paul March measured (as attached) then only about ~25% of the magnetron energy (2.40GHz - 2.45GHz) would be getting inside the cavity and the other ~75% (above 2.45GHz would be rejected.

Which means the 663Ws forward power (at VSWR 1.622:1) drops to 167 real watts inside the frustum with 533W reflected back to heat the magnetron.

With 167W in the cavity and a Q of 48.8 the predicted Force generation is 31uNs and at a Q of 20.2 is 13uNs. A SnowFlake is ~30uN, to give an idea of the magnitude of the Forces being generated here.

This same effect of mismatched input and output bandwidths caused the serious dip in Prof Yang's Force versus power curve. The lower left rectangles, in the group of 6 charts, are the cavity input bandwidth and the other curve is the magnetron output bandwidth. Clear to see the massive mismatch that occurred and that totally messed up her data until they went back and found the reason for the massive dip.

So history has maybe repeated itself and this cavity input / magnetron output bandwidth mismatch may have struck again.
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Online demofsky

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A post over on reddit attributes the thrust to a phenomenon called sputtering.  I was wondering how valid this interpretation is.  It appears to depend on oxidation, which seems unlikely in a vacuum.  Link:

http://www.reddit.com/r/Futurology/comments/3emk49/direct_thrust_measured_from_propellantless_em/cthg9uo
You can answer that question by filling the enclosed Frustum with Sulfur hexafluoride,

Sulfur hexafluoride is an inorganic, colorless, odorless, non-flammable, extremely potent greenhouse gas which is an excellent electrical insulator. SF 6 has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom.

But it is hard to keep in a perforated cavity. It is used in high power systems to prevent arcing.

Shell

Another thing I like about SF6 is that is a dense gas so if the thrust is dependent on gas being present then there is a lot to work with.  That said, I have no idea what frequency you would need to use it as a resonant gas.

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