Author Topic: EM Drive Developments - related to space flight applications - Thread 11  (Read 223703 times)

Online Chris Bergin

This is a thread - Thread 11 in the series - focused on objective analysis of whether the EM Drive (a cavity resonating at microwave frequencies) reported "thrust force" is an experimental artifact or whether it is a real propulsion effect  that can be used for space applications, and if so, in discussing those possible space propulsion applications.

Objective skeptical inquiry is strongly welcome.   Disagreements should be expressed politely, concentrating on the technical, engineering and scientific aspects, instead of focusing on people.   As such, the use of experimental data, mathematics, physics, engineering, drawings, spreadsheets and computer simulations are strongly encouraged, while subjective wordy statements are discouraged. Peer-reviewed information from reputable journals is strongly encouraged.  Please acknowledge the authors and respect copyrights.

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Links to previous threads:

Thread 1:
http://forum.nasaspaceflight.com/index.php?topic=29276.0

Thread 2:
http://forum.nasaspaceflight.com/index.php?topic=36313.0

Thread 3:
http://forum.nasaspaceflight.com/index.php?topic=37642.0

Thread 4:
http://forum.nasaspaceflight.com/index.php?topic=38203.0

Thread 5:
http://forum.nasaspaceflight.com/index.php?topic=38577.0

Thread 6:
http://forum.nasaspaceflight.com/index.php?topic=39004.0

Thread 7:
http://forum.nasaspaceflight.com/index.php?topic=39772.0

Thread 8:
http://forum.nasaspaceflight.com/index.php?topic=40959.0

Thread 9:
https://forum.nasaspaceflight.com/index.php?topic=41732.0

Thread 10:
https://forum.nasaspaceflight.com/index.php?topic=42978.0

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Entry level thread:
http://forum.nasaspaceflight.com/index.php?topic=37438.0

Baseline NSF Article:
http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/


Chris note: Please note all posts need to be useful and worthwhile or they will be removed via moderation. This subject has large interest, with over 6 million thread reads and 1 million article reads. Most people are reading and not posting, so when you post it is in front of a very large audience.

Also, and it should go without saying, amateur experiments are discouraged unless you have gained educated and/or professional advice for safety reasons.

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Additional requirements:

No boring back and forth "you're wrong" "no you're wrong". No spamming silly messages in every post like "time to come out of the shadows". Mods will trim posts that are not of wrthwhile quality.
« Last Edit: 06/11/2018 07:03 pm by Chris Bergin »

Offline X_RaY

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 @all:

There is a great old info thread initiated by Dr. Rodal to look up some of the relevant basics of cavity resonator physics in addition to the actual EM-Drive thread series.

For those interested in EMDrive, it may be worth reading the few pages, as they contain some relevant information and calculations on the subject that should be known for general understanding.
Resonant Cavity Space-Propulsion: institutional experiments and theory
« Last Edit: 06/15/2018 03:22 pm by X_RaY »

Offline TheTraveller

No boring back and forth "you're wrong" "no you're wrong". No spamming silly messages in every post like "time to come out of the shadows". Mods will trim posts that are not of wrthwhile quality.

Chris,

IT IS TIME for the EmDrive to come out of the shadows. Not a silly nor spamming message at all.

For far too long replicators have either failed to measure thrust or measured thrust equivalent to several snow flakes falling on a scale. None that I know of followed Roger's advise, well not all of it. As a result their replications were not very good.

I have engaged a process to stop DIYers building EmDrive that will not work, to provide a very clear build methodology and to explain why doing it that way is important.

After the videos of the KISS thruster going round and round are released, further more detailed theory as to why the EmDrive works inside existing physics will be engaged. Plus I'll be doing a series of public demos around the planet.

While an EmDrive with enough specific force to build a 1g spacecraft is some time in the future, current tech EmDrives can deliver 10x the specific force as can the best Ion Drives and do it with electricity (well actually photon momentum and energy) as the fuel.

I do appreciate your patience, especially during theory debates, as the future of space propulsion is revealed.
« Last Edit: 06/12/2018 02:32 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

The miniVNA tiny+ has arrived.

Now includes Open, Shorted and 50 ohm calibration SMAs.

The miniVNA tiny+ is a very important tool what will be used to confirm TE013 resonance via S11 rtn loss sweep, confirm TE013 excitation via E field probe inserted inside the excited cavity and to tune the 1/4 excitation wave stub coupler to coupling factor 1.0, to 50 ohm impedance and to lowest VSWR.

Waiting on arrival of the Silver Epoxy to start frustum fabrication.

« Last Edit: 06/12/2018 04:21 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline SteveD

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Quote
Thank you for summarizing. I have some comments here. I am biased the opposite way as you so it is useful to counter balance with yours.

First, TT suspected there might not be resonance in Tajmar's cavity, probably because there was no thrust. I think the same kind of suspicion  should be cast on the Polish cavity too, because there was also no definite evidence that there was resonance.

Second, Monomorphic's experiment I think was a power on test; there was no microwave involved. 

Third, you said "1. The EMDrive surrounded by a plastic insulator might not be working." This is a strange conclusion, as strange as Shawyer's belief that there must be acceleration for the EmDrive to enter "motor" mode. It is not far from saying that  the EMDrive made by people younger than 50 might not be working. After all, this statement has some support because Shawyer, TT, Paul claimed thrust but Tajmar, the California PhD students and monomorphic didn't.
« Last Edit: 06/10/2018 01:50 PM by PotomacNeuron »



I base my conclusion on these data points:
1.  Jamie's drive is likely to be in resonance given the quality of his work.
2.  The Polish researcher reported about 9 uN with the drive in Null configuration.
3.  The Polish researcher reported about 27 uN with the drive in a non-Null configuration.
4.  Jamie reported about 9 uN with the drive in a non-Null configuration.
5.  Shell seemed to believe an effect was taking place outside the can (but presented no data).
6.  Noether's theorem would suggest that an EMDrive cannot accelerate without some interaction with the universe outside of the can.
7.  WarpTech was working on a theory requiring exchange of heat with the outside universe.
8.  It would seem that insulating the can has stopped the effect, whatever it is, from interacting with the outside universe, turning this into an isolated system and killing the effect as Noether would predict.
9.  If true this is an important datapoint in figure out what is actually going on here.

So my question to you, how do we falsify the hypothesis that the 9uN being detected is the result of Lorentz forces in the wiring?


Offline PotomacNeuron

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I base my conclusion on these data points:
1.  Jamie's drive is likely to be in resonance given the quality of his work.
2.  The Polish researcher reported about 9 uN with the drive in Null configuration.
3.  The Polish researcher reported about 27 uN with the drive in a non-Null configuration.
4.  Jamie reported about 9 uN with the drive in a non-Null configuration.
5.  Shell seemed to believe an effect was taking place outside the can (but presented no data).
6.  Noether's theorem would suggest that an EMDrive cannot accelerate without some interaction with the universe outside of the can.
7.  WarpTech was working on a theory requiring exchange of heat with the outside universe.
8.  It would seem that insulating the can has stopped the effect, whatever it is, from interacting with the outside universe, turning this into an isolated system and killing the effect as Noether would predict.
9.  If true this is an important datapoint in figure out what is actually going on here.

You have also an implicit one:
0. That EmDrive likely works,
while mine is that it does not work. This difference could explain the different observations we made

As to whether Monomorphic's recent experiment involved microwave, we just need him to tell us. [update: 25W involved. see Monomorphic's answer]

Quote
So my question to you, how do we falsify the hypothesis that the 9uN being detected is the result of Lorentz forces in the wiring?

A good built without ground loop and untwisted power supply leads should be able to avoid the Lorentz problem. So the hypothesis is only a hypothesis for some of the experiments, such as EW's.

Monomorphic's test bed has built-in ability to assess Lorentz force by being built on top of wheels and by not using magnetic damping or step motors. He only needs to rotate his test bed to different angles and plot force against angle to see whether force changes with angle.
« Last Edit: 06/12/2018 11:56 am by PotomacNeuron »
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Offline TheTraveller

A good built without ground loop and untwisted power supply leads should be able to avoid the Lorentz problem. So the hypothesis is only a hypothesis for some of the experiments, such as EW's.

Monomorphic's test bed has built-in ability to assess Lorentz force by being built on top of wheels and by not using magnetic damping or step motors. He only needs to rotate his test bed to different angles and plot force against angle to see whether force changes with angle.

Every EmDrive builder needs to verify the mode they have excited is the desired mode and not a system resonance.

The only real way to do that is to insert an E field probe into the cavity and map out the E field lobes. As far as I know only Roger and I have done that.

As example is this VNA scan done by Paul. Don't know if the excited mode was never found as it was not shown on the COMSOL resonance mode analysis.

Very unwise to spend all the time and money building an EmDrive and test rig and then assume the VNA scan freq, because it is close to a simulation freq, is the mode you expect to excite. Wish it were so easy.
« Last Edit: 06/12/2018 08:18 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline X_RaY

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A good built without ground loop and untwisted power supply leads should be able to avoid the Lorentz problem. So the hypothesis is only a hypothesis for some of the experiments, such as EW's.

Monomorphic's test bed has built-in ability to assess Lorentz force by being built on top of wheels and by not using magnetic damping or step motors. He only needs to rotate his test bed to different angles and plot force against angle to see whether force changes with angle.

Every EmDrive builder needs to verify the mode they have excited is the desired mode and not a system resonance.

The only real way to do that is to insert an E field probe into the cavity and map out the E field lobes. As far as I know only Roger and I have done that.

As example is this VNA scan done by Paul. Don't know if the excited mode was never found as it was not shown on the COMSOL resonance mode analysis.

Very unwise to spend all the time and money building an EmDrive and test rig and then assume the VNA scan freq, because it is close to a simulation freq, is the mode you expect to excite. Wish it were so easy.


The idea sounds good at first glance, but in TE0np mode the E-field is theoretically only zero on the central infinitesimal-thin axis of symmetry. However, such a probe has a spatial extension greater than zero (length and diameter) and is conductive.
I guess a probe in the cavity will distort the pattern and shift the resonant frequency, as the EM field must satisfy the boundary conditions on the coaxial outer conductor.
« Last Edit: 06/12/2018 09:03 am by X_RaY »

Offline TheTraveller

A good built without ground loop and untwisted power supply leads should be able to avoid the Lorentz problem. So the hypothesis is only a hypothesis for some of the experiments, such as EW's.

Monomorphic's test bed has built-in ability to assess Lorentz force by being built on top of wheels and by not using magnetic damping or step motors. He only needs to rotate his test bed to different angles and plot force against angle to see whether force changes with angle.

Every EmDrive builder needs to verify the mode they have excited is the desired mode and not a system resonance.

The only real way to do that is to insert an E field probe into the cavity and map out the E field lobes. As far as I know only Roger and I have done that.

As example is this VNA scan done by Paul. Don't know if the excited mode was never found as it was not shown on the COMSOL resonance mode analysis.

Very unwise to spend all the time and money building an EmDrive and test rig and then assume the VNA scan freq, because it is close to a simulation freq, is the mode you expect to excite. Wish it were so easy.


The idea sounds good at first glance, but in TE0np mode the E-field is theoretically only zero on the central infinitesimal-thin axis of symmetry. However, such a probe has a spatial extension greater than zero (length and diameter) and is conductive.
I guess a probe in the cavity will distort the pattern and shift the resonant frequency, as the EM field must satisfy the boundary conditions on the coaxial outer conductor.

Need a VNA to gen the Rf to drive the coupler plus another freq scanner that is isolated from the cavity and the other Rf gen. That way the coax shield of the E field probe coax from the freq scanner is not connected to the cavity shell.

What you do is to use the E field probe to find the location of the highest E field lobes inside the cavity.

Will demo how to do this.
« Last Edit: 06/12/2018 09:14 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline X_RaY

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A good built without ground loop and untwisted power supply leads should be able to avoid the Lorentz problem. So the hypothesis is only a hypothesis for some of the experiments, such as EW's.

Monomorphic's test bed has built-in ability to assess Lorentz force by being built on top of wheels and by not using magnetic damping or step motors. He only needs to rotate his test bed to different angles and plot force against angle to see whether force changes with angle.

Every EmDrive builder needs to verify the mode they have excited is the desired mode and not a system resonance.

The only real way to do that is to insert an E field probe into the cavity and map out the E field lobes. As far as I know only Roger and I have done that.

As example is this VNA scan done by Paul. Don't know if the excited mode was never found as it was not shown on the COMSOL resonance mode analysis.

Very unwise to spend all the time and money building an EmDrive and test rig and then assume the VNA scan freq, because it is close to a simulation freq, is the mode you expect to excite. Wish it were so easy.


The idea sounds good at first glance, but in TE0np mode the E-field is theoretically only zero on the central infinitesimal-thin axis of symmetry. However, such a probe has a spatial extension greater than zero (length and diameter) and is conductive.
I guess a probe in the cavity will distort the pattern and shift the resonant frequency, as the EM field must satisfy the boundary conditions on the coaxial outer conductor.

Need a VNA to gen the Rf to drive the coupler plus another freq scanner that is isolated from the cavity and the other Rf gen. That way the coax shield of the E field probe coax from the freq scanner is not connected to the cavity shell.

What you do is to use the E field probe to find the location of the highest E field lobes inside the cavity.

Will demo how to do this.
Isolated or not, my argument is that any additional structure within the cavity, especially a conductive one, changes the natural frequencies of the resonator. The second point I do not understand from your contributions is why an additional spectrum analyzer is needed to map the amplitudes of the E field. This could be done with a 2-port SNA* or VNA** in S21 mode.

By the way, you can only isolate the DC component, which is irrelevant in this case, but not the AC RF.  ;)



*   scalar network analyzer (SNA)—measures amplitude properties only
** vector network analyzer (VNA)—measures both amplitude and phase properties
« Last Edit: 06/12/2018 10:29 am by X_RaY »

Offline TheTraveller

Isolated or not, my argument is that any additional structure within the cavity, especially a conductive one, changes the natural frequencies of the resonator. The second point I do not understand from your contributions is why an additional spectrum analyzer is needed to map the amplitudes of the E field. This could be done with a 2-port VNA in S21 mode.

By the way, you can only isolate the DC component, which is irrelevant in this case, but not the AC RF.  ;)

XRay,

This is something that you need to try. It does work.

I use 300mm of the thinnest and stiffest GHz coax as the probe, plus a longer more flexible coax to the 10dB or 20 dB or 40dB attenuator to the freq scanner.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline R.W. Keyes

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Quote from: PotomacNeuron
...it is not far from saying that  the EMDrive made by people younger than 50 might not be working....

Wow, I am glad I am 51. Some advantage to it after all  :)

Offline PotomacNeuron

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Need a VNA to gen the Rf to drive the coupler plus another freq scanner that is isolated from the cavity and the other Rf gen. That way the coax shield of the E field probe coax from the freq scanner is not connected to the cavity shell.

What you do is to use the E field probe to find the location of the highest E field lobes inside the cavity.

Will demo how to do this.

I highlighted the part I have a concern with. I think a probe with its shield not contacting to the cavity shell will leak out microwave. Just let them contact, and the probe can still probe E field near the wall from inside of the cavity. If the stud is very short and impedance does not match, the disturbance to the resonance mode should be minimal.
« Last Edit: 06/12/2018 11:55 am by PotomacNeuron »
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Online Monomorphic

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As to whether Monomorphic's recent experiment involved microwave, we just need him to tell us.

Monomorphic's test bed has built-in ability to assess Lorentz force by being built on top of wheels and by not using magnetic damping or step motors. He only needs to rotate his test bed to different angles and plot force against angle to see whether force changes with angle.

The recent experiment did involve ~25W of RF.  You can see that by the dark pink line in the chart below. The label says Ambient RF, as that is how I detect if RF is present - by using an antenna, a band pass filter (2.35Ghz - 2.5ghz), and a RF power detector to detect the leaked RF from the cavity at very close range.

Since I have taken care to reduce Lorentz force by using short and highly twisted pairs, I am seeing very little of that. It is present, but it is at the edge of my detection abilities, about ~0.2uN. I will have some tests with the test bed at different angles to the geomagnetic field.
« Last Edit: 06/12/2018 11:47 am by Monomorphic »

Online Monomorphic

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The idea sounds good at first glance, but in TE0np mode the E-field is theoretically only zero on the central infinitesimal-thin axis of symmetry. However, such a probe has a spatial extension greater than zero (length and diameter) and is conductive.
I guess a probe in the cavity will distort the pattern and shift the resonant frequency, as the EM field must satisfy the boundary conditions on the coaxial outer conductor.

This is exactly what I was thinking. Inserting a coax cable into the cavity will cause the resonant frequency to rise the further in the coax is inserted. Then RF will couple with the coax shielding at varying degrees as the coax is inserted, leaking RF to the outside, which will probably be very non-linear. I would be very surprised if we could make sense of spectrum analyser readings in these conditions.

I suppose we could drill small holes all over the frustum and insert a small antenna a known distance into the cavity in each hole to map it that way. This would also allow us to seal the cavity using nuts between each test. Sounds like a huge hassle though!

The US Navy team uses thermocouples along the outside of the cavity to detect temperature changes which correspond to mode shape. This is the same principle as the infrared camera and the best option IMHO. I do not think that is possible with the 3D printed cavity as the walls are fairly thick and mostly hollow, but I do hope it will work with Oyzw's solid copper cavity and my older cavity with acetate and copper foil walls.
« Last Edit: 06/12/2018 12:42 pm by Monomorphic »

Offline TheTraveller

This is exactly what I was thinking. Inserting a coax cable into the cavity will cause the resonant frequency to rise the further in the coax is inserted. Then RF will couple with the coax shielding at varying degrees as the coax is inserted, leaking RF to the outside, which will probably be very non-linear. I would be very surprised if we could make sense of spectrum analyser readings in these conditions.

Holes in the walls and end plates do work to a limited extent. Really good are holes in the small and big end plate where the max E field intensity is projected to be.

Suggest you sim an electrically isolated 1mm dia coax inserted into the cavity from a hole in the middle of the big end, centered and at various penetration depths and see what happens to resonance.

Sorry but way too much theory and no experimental data to back it up. Heavy on theory and light on experimental data is why DIYers struggle to generate significant P-P force.
« Last Edit: 06/12/2018 02:07 pm by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

Anybody wish to answer a simple question?

How many Joules of Work will be done by a P-P drive that can generate 60,000 Newtons of Force, while accelerating a 60,000kg spaceship's mass for 100 seconds that is mid way between the orbits of Earth and Mars?
It Is Time For The EmDrive To Come Out Of The Shadows

Online Jim Davis

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How many Joules of Work will be done by a P-P drive that can generate 60,000 Newtons of Force, while accelerating a 60,000kg spaceship's mass for 100 seconds that is mid way between the orbits of Earth and Mars?

It depends on the reference frame since energy is not conserved if P-P drives work.

Offline wicoe

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How many Joules of Work will be done by a P-P drive that can generate 60,000 Newtons of Force, while accelerating a 60,000kg spaceship's mass for 100 seconds that is mid way between the orbits of Earth and Mars?

It depends on the reference frame since energy is not conserved if P-P drives work.

It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).  The kinetic energy difference (after - before) depends on the ref. frame, which is quite obvious.  As a consequence, the amount of work done by the drive must depend on the ref. frame to counteract this (i.e. so that the total energy is conserved).  This is only possible if this involves propellant or some other interaction that introduces frame dependence (simply spending chemical or electric energy is not enough since it is not frame-dependent).

Online Jim Davis

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It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).

I don't believe this is correct. Different reference frames will disagree on how much work was done on the ship and how much on the exhaust but all should agree with the total amount of work done.

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