Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1804102 times)

Offline TheTraveller

The Chinese may have figured out how to make a cavity with a Q of 117,500 using flat end plates.

As per the attachment they build in a short section, at each end of the tapered wave guide, of constant diameter circular waveguide that allows the spherical waves in the tapered portion of the cavity to transition from/to a planar wave that will generate no phase distortion as it bounces off the flat end plate.

Very clever.

The drawings also show how they do impedance matching.

See attachment.

I now know my 100,000 Q goal is obtainable. Yea!
« Last Edit: 07/09/2015 08:24 AM by TheTraveller »
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Offline OttO

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Just a thought:

Our apparatus has the same look as a closed end horn antenna. Why not use variable fins to match the cut off? it seems to me that would be an easy way to tune it.

Offline flux_capacitor

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To stop any shifting, especially as I plan to ship finished EMDrives all over the planet, the single 1/4 wave stub antenna was replaced by 3 x 1/4 wave stub antennas that are joined at the centre and attached to the centre of 3 Rf connectors fitted into the side walls.

Trust the attached crude drawing makes it clear how I intend to excite TE013 mode and do so in a way to introduce min phase distortion into the internal resonant standing wave by the excitation antenna.

I understand you will connect your RF amp to those three 1/4 wave stub antennas.
But after that, does that also allow your design to connect 3 separated RF amps to multiply the input power x3? If so, how to couple those? In read a few pages ago (EDIT: in this post by ElizabethGreene) that some dual magnetron geometries can automatically tune themselves, via "injection locking". What about multiple solid-state WiFi amps? Do we need some external controller or would they naturally lock their frequencies and phases together?
« Last Edit: 07/13/2015 03:21 PM by flux_capacitor »

Offline TheTraveller

To stop any shifting, especially as I plan to ship finished EMDrives all over the planet, the single 1/4 wave stub antenna was replaced by 3 x 1/4 wave stub antennas that are joined at the centre and attached to the centre of 3 Rf connectors fitted into the side walls.

Trust the attached crude drawing makes it clear how I intend to excite TE013 mode and do so in a way to introduce min phase distortion into the internal resonant standing wave by the excitation antenna.

I understand you will connect your RF amp to those three 1/4 wave stub antennas.
But after that, does that also allow your design to connect 3 separated RF amps to multiply the input power x3? If so, how to couple those? In read a few pages ago that some dual magnetron geometries can automatically tune themselves. What about multiple solid-state WiFi amps? Do we need some external controller or would they naturally lock their frequencies and phases together?

Interesting idea.

Each Rf amp would be fed by the same variable freq Rf generator. Depends on how tight the phase shift specs are for each amp.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

A friend of mine does a lot of Chinese product sourcing for clients. Told him about my 2.45GHz power amp requirements. Said would get his guys to see what they could find. Look what his guy just found for me!

http://m.alibaba.com/product/60173635690/GSM-CDMA-DCS-Amplifier-100W.html

A sample is on it's way to me for just the shipping costs.

Happy days! 100 lovely Watts! Power output fully adjustable. Happy chappie!

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

Online Mulletron

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Maybe we could upvote and get Adam Savage's, co-host of MythBusters, attention. It would be a dream to have this myth busted (or confirmed!).

http://www.reddit.com/r/IAmA/comments/3cfqzf/z/csvcjt3


Outer Space or Bust!
Challenge your preconceptions, or they will challenge you. - Velik

Offline TheTraveller

Maybe we could upvote and get Adam Savage's, co-host of MythBusters, attention. It would be a dream to have this myth busted (or confirmed!).

http://www.reddit.com/r/IAmA/comments/3cfqzf/z/csvcjt3


Outer Space or Bust!

I will confirm it. I have no doubt.

Additionally I'll collect and publish the 1st EMDrive acceleration versus Rf amp power consumption data from a rotary test rig that has no cables and is completely battery powered.

With the 100W Rf amp, expect to get around 6gf to spin a 12kg rotary table. The SPR Denonstrator produced 1.6gf net and spun a 100kg mass. My test rig should accelerate 30x faster than did the SPR rotary video.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline Rodal

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The Chinese may have figured out how to make a cavity with a Q of 117,500 using flat end plates.

As per the attachment they build in a short section, at each end of the tapered wave guide, of constant diameter circular waveguide that allows the spherical waves in the tapered portion of the cavity to transition from/to a planar wave that will generate no phase distortion as it bounces off the flat end plate.

Very clever.

The drawings also show how they do impedance matching.

See attachment.

I now know my 100,000 Q goal is obtainable. Yea!

If you draw a horizontal axis through the middle of the waveguide in the picture you show, what does the waveguide opening into the cavity on the plane perpendicular to that axis look like?



In other words, what does the other view look like?

It would be nice if we could guesstimate what the waveguide opening aspect ratio is, compared to the lateral cavity dimensions.


_____________________________________________
Eventually, we could also analyze with Meep the cavity + waveguide
« Last Edit: 07/09/2015 11:57 AM by Rodal »

Offline TheTraveller

The Chinese may have figured out how to make a cavity with a Q of 117,500 using flat end plates.

As per the attachment they build in a short section, at each end of the tapered wave guide, of constant diameter circular waveguide that allows the spherical waves in the tapered portion of the cavity to transition from/to a planar wave that will generate no phase distortion as it bounces off the flat end plate.

Very clever.

The drawings also show how they do impedance matching.

See attachment.

I now know my 100,000 Q goal is obtainable. Yea!

If you draw a horizontal axis through the middle of the waveguide in the picture you show, what does the waveguide opening into the cavity on the plane perpendicular to that axis look like?



In other words, what does the other view look like?

It would be nice if we could guesstimate what the waveguide opening aspect ratio is, compared to the lateral cavity dimensions

More info is in the paper, which is in Chinese. Attached.

I don't think the drawing is dimensionally correct.
« Last Edit: 07/09/2015 12:04 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline ludkokanta

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How would you suggest building a rotational measuring system?

If we were to build it with a few 1 inch peaces of wood as a rotational system which bearing would be fitting?

It would have to take the weight of the "em drive" or whatever and weight of the wood as an axial force and still have less then say 20 micro Newtons of tangential friction resistance.

Offline Rodal

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Sooooo..... the Poynting vector has a DC offset eh? Who would've thought that! LOL!

http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=37642.0;attach=1041397

This means E and H should have a DC component as well, which means there are probably DC circulating currents around the frustum as it's charging.

At least that is how I would interpret these extrapolations and the uni-directional poynting vector.
Todd


1) The Poynting vector analyzed in the post is located at location in the free-space of the cavity next to the longitudinal axis of axisymmetry of the cone (the FD grid had an even number of grids, so it is at the first grid to one side of the longitudinal axis), at the maximum of the first wave-pattern formed downstream from the antenna , in the direction from the small base towards the big base.

2) For purely travelling waves in an open waveguide, the Poynting vector fluctuation with time looks like in this image:

____________________________________________________________________________



Electric (E) and Magnetizing (H) fields, and Poynting vector                                                                 
Open Waveguide                                                                 
RF feed ON 


The frequency is twice the frequency of the electromagnetic fields, it fluctuates between maximum and zero, with an average value half-way in between
____________________________________________________________________________

3) For a pure standing wave in a cavity (the antenna feed being OFF),  the Poynting vector fluctuation with time looks like the second image to the right:

____________________________________________________________________________



Poynting vector                                                                  Poynting vector
Open Waveguide                                                                Closed Cavity
RF feed ON                                                                        RF feed OFF

____________________________________________________________________________

Due to the electromagnetic fields in a standing wave looking like this:



Electric (E) and Magnetic (B) fields
Closed Cavity
RF feed OFF

This is due to the boundary condition: the Electric field (E) transverse component to a conducting wall is zero, but the magnetic (B) and the magnetizing (H) fields transverse components are not zero.  The conducting walls thereby change the phase of the electric and magnetic fields so that they are offset by 90 degrees at the conducting wall at the big base and the small base.

The frequency is twice the frequency of the electromagnetic fields, its average is zero and it fluctuates between equal absolute magnitudes, (+) plus and (-) minus
____________________________________________________________________________

4) In the EM Drive with the RF feed ON we have a superposition of travelling waves.  Unlike a cavity with the RF feed OFF, where travelling waves get reflected and perfectly match at resonance to make a standing wave frozen in space, in the EM Drive with the RF feed ON we have a superposition of travelling waves and standing waves.  Or, in other words, an unequal superposition of travelling waves propagating in opposite direction.
The fact that the time-average is not zero, but that the minimum amplitude is not zero either but that it fluctuates between negative and positive shows this superposition.  The fact that the time-average is very offset means that at this location and at the time steps shown in my analysis, the proportion of the travelling wave propagation is much larger than the amount of standing wave at that location.



In other words, with the RF feed ON, the situation is neither a pure travelling wave as in an open waveguide nor is it purely standing waves, but it is a superposition of both.(*)

Since standing waves themselves are constructed by superposition of travelling waves, it really has to do with the superposition of travelling waves coming from opposite directions.  The Poynting vector fluctuation depends on the location in the EM Drive. I have examined much more data than I have reported here.  There are places in the EM Drive where there is mostly standing waves, and locations where there are mostly travelling waves.  The information is very useful to understand what is going on.

Similarly with people building their own experiments, those embarking on a build learn first hand knowledge that may not be available to the public.  Ditto for numerical simulation. 

There are several people conducting their own experiments.  Ideally  there would be several people conducting their own independent analyses.  The csv files are available for everybody to analyze.


5) What is most interesting to me is the apparent growth with time of the Poynting vector fluctuations during the few time steps examined.  This may show:

Only examining many more time steps we will know what is going on.

EDIT: as pointed out by Ricvil, the amplification is probably just what is to be expected from the early  evolution of the fields until a balance is reached.

______________
(*)  In addition, due to the taper, in the truncated cone with the RF feed ON there are also evanescent waves, as shown in several papers (Zeng and Fan being one of the latest).
« Last Edit: 07/09/2015 06:20 PM by Rodal »

Offline Rodal

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...

More info is in the paper, which is in Chinese. Attached.

I don't think the drawing is dimensionally correct.
Please let us know if you guesstimate what the waveguide opening dimensions used by Prof Yang are.

QUESTION: are you planning to use a waveguide feed into the cavity in your experiment, as used by Prof.  Yang?

Offline TheTraveller

...

More info is in the paper, which is in Chinese. Attached.

I don't think the drawing is dimensionally correct.
Please let us know if you guesstimate what the waveguide opening dimensions used by Prof Yang are.

QUESTION: are you planning to use a waveguide feed into the cavity in your experiment, as used by Prof.  Yang?

Will be using a 100W narrow band Rf amp feeding the internal frustum spherical antenna array via 3 coax cables & connectors.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

How would you suggest building a rotational measuring system?

If we were to build it with a few 1 inch peaces of wood as a rotational system which bearing would be fitting?

It would have to take the weight of the "em drive" or whatever and weight of the wood as an axial force and still have less then say 20 micro Newtons of tangential friction resistance.

My rough drawing attached. Uses a DIY magnetic thrust bearing with 2 low stiction/friction bearings.
« Last Edit: 07/09/2015 01:08 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

Offline Rodal

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...

More info is in the paper, which is in Chinese. Attached.

I don't think the drawing is dimensionally correct.
Please let us know if you guesstimate what the waveguide opening dimensions used by Prof Yang are.

QUESTION: are you planning to use a waveguide feed into the cavity in your experiment, as used by Prof.  Yang?

Will be using a 100W narrow band Rf amp feeding the internal frustum spherical antenna array via 3 coax cables & connectors.
Where in the frustum will your spherical antenna be located?  (is it going to be located in the longitudinal axis of axisymmetry of the cone?,  is it going to be located near the big base? near the small base?
« Last Edit: 07/09/2015 01:08 PM by Rodal »

Offline SeeShells

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@Seeshells

Why not use an interferometer to measure the displacement? Too much noise?

http://www.instructables.com/id/Desktop-Michelson-Morely-Interferometer/

That is a great idea.

Noise? I think so, the noise level would probably be off the charts and the display would look a little like a laser light show. Sadly, I have a road with traffic about 500 foot away that I suspect would show up.

I went with the beam supported by the stainless steel wires attached to the center of my fulcrum so I could show about any level of thrust, from small to large. Even micronewtons should show up, very slowly overcoming the mass of the system to accelerate. Wiki has very nice formulas to calculate (thank goodness for wiki). This is why I wanted to control the timestamped frame grabs from the graph at 30 frames second to every hour if needed. 

Even on the cheap lasers I figure I have a battery life to consider and they will be powered by stacked C cells to assure me they will not die during a test.

Shell

PS: Do like that simple idea.

Offline TheTraveller

...

More info is in the paper, which is in Chinese. Attached.

I don't think the drawing is dimensionally correct.
Please let us know if you guesstimate what the waveguide opening dimensions used by Prof Yang are.

QUESTION: are you planning to use a waveguide feed into the cavity in your experiment, as used by Prof.  Yang?

Will be using a 100W narrow band Rf amp feeding the internal frustum spherical antenna array via 3 coax cables & connectors.
Where in the frustum will your spherical antenna be located?  (is it going to be located in the longitudinal axis of axisymmetry of the cone?,  is it going to be located near the big base? near the small base?

http://forum.nasaspaceflight.com/index.php?topic=37642.msg1402007#msg1402007
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline SeeShells

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Further info on the antenna arrangement I'll be using on my 2.45GHz version of the Flight Thruster.

As the EM waves in a cavity with spherical end plates are spherical, the antenna also needs to be spherical as per the sidewall insertion point curve of the EM wave at that point.

I could have used a single stub 1/4 wave antenna curved to match the spherical EM wave shape but I had reservations that the end point of a single 1/4 wave stub inside the cavity may shift over time.

To stop any shifting, especially as I plan to ship finished EMDrives all over the planet, the single 1/4 wave stub antenna was replaced by 3 x 1/4 wave stub antennas that are joined at the centre and attached to the centre of 3 Rf connectors fitted into the side walls.

Trust the attached crude drawing makes it clear how I intend to excite TE013 mode and do so in a way to introduce min phase distortion into the internal resonant standing wave by the excitation antenna.
I would hope you take in consideration the phases of your antennas and the distance from each other, you wouldn't want them to cause standing wave attenuations with each other canceling out a good idea.

Offline Rodal

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Further info on the antenna arrangement I'll be using on my 2.45GHz version of the Flight Thruster.

As the EM waves in a cavity with spherical end plates are spherical, the antenna also needs to be spherical as per the sidewall insertion point curve of the EM wave at that point.

I could have used a single stub 1/4 wave antenna curved to match the spherical EM wave shape but I had reservations that the end point of a single 1/4 wave stub inside the cavity may shift over time.

To stop any shifting, especially as I plan to ship finished EMDrives all over the planet, the single 1/4 wave stub antenna was replaced by 3 x 1/4 wave stub antennas that are joined at the centre and attached to the centre of 3 Rf connectors fitted into the side walls.

Trust the attached crude drawing makes it clear how I intend to excite TE013 mode and do so in a way to introduce min phase distortion into the internal resonant standing wave by the excitation antenna.
I would hope you take in consideration the phases of your antennas and the distance from each other, you wouldn't want them to cause standing wave attenuations with each other canceling out a good idea.

Shell, there is also the issue that in the drawing, the assumption is made that the wave-patterns in the longitudinal direction are sinusoidal harmonic with equidistant nodal points.  This is true for a cylindrical waveguide but it is not true for a conical waveguide (even with spherical ends) (*).  With a conical waveguide the wave-patterns in the longitudinal direction are not sinusoidal harmonic: the nodes are not equidistant.  How different from equidistant the nodes are depends on the mode(s) being excited and their participation. Hopefully by placing the antenna where it is proposed he can force that mode, but a lot depends on nearby modes and mode participation.  Since he is not using a magnetron, that may help in eliminating other modes from participating.

_______
(*) The wave patterns in the longitudinal direction for a spherical wave in a cavity are not sinusoidal harmonic, they are governed by Spherical Bessel functions, which have unequal distance between nodes.
« Last Edit: 07/09/2015 02:01 PM by Rodal »

Offline SeeShells

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Further info on the antenna arrangement I'll be using on my 2.45GHz version of the Flight Thruster.

As the EM waves in a cavity with spherical end plates are spherical, the antenna also needs to be spherical as per the sidewall insertion point curve of the EM wave at that point.

I could have used a single stub 1/4 wave antenna curved to match the spherical EM wave shape but I had reservations that the end point of a single 1/4 wave stub inside the cavity may shift over time.

To stop any shifting, especially as I plan to ship finished EMDrives all over the planet, the single 1/4 wave stub antenna was replaced by 3 x 1/4 wave stub antennas that are joined at the centre and attached to the centre of 3 Rf connectors fitted into the side walls.

Trust the attached crude drawing makes it clear how I intend to excite TE013 mode and do so in a way to introduce min phase distortion into the internal resonant standing wave by the excitation antenna.
I would hope you take in consideration the phases of your antennas and the distance from each other, you wouldn't want them to cause standing wave attenuations with each other canceling out a good idea.

Shell, there is also the issue that in the drawing, the assumption is made that the wave-patterns in the longitudinal direction are sinusoidal harmonic with equidistant nodal points.  This is true for a cylindrical waveguide but it is not true for a conical waveguide.  With a conical waveguide the wave-patterns in the longitudinal direction are not sinusoidal harmonic: the nodes are not equidistant.  How different from equidistant the nodes are depends on the mode(s) being excited and their participation
I know Jose I really know and when the modes collapse and shift which is what needs to happen the antennas and their positions will not be in any kind of phase sitting in the center like that. Maybe linking the 3 dipoles close together in a phase locked arrangement would cause less havoc? What do you think TT?

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