Author Topic: EM Drive Developments - related to space flight applications - Thread 10  (Read 1175790 times)

Offline Star One

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Paper is now being widely reported by those still interested on social media and general consensus is that’s that case closed. Lot of people saying oh we always knew it was nonsense.

Example here.

https://mobile.twitter.com/fcain/status/997586879779430400

One interesting comment here.

https://twitter.com/WayCharMar/status/997618367761735680?s=20

Quote
Actually if you read the paper it say “We found that e.g. magnetic interaction from cables and amplifiers with Earth’s magnetic field can be a significant error source for EMDrives.” The Mach-Effect Thruster did not show this as a problem as shown by their their graph @ 90 deg.
« Last Edit: 05/20/2018 08:42 pm by Star One »

Offline Monomorphic

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Paper is now being widely reported by those still interested on social media and general consensus is that’s that case closed.

~20 twitter followers of Fraser Cain is hardly general consensus.

Looking at the pictures of Tajmar's experiment, no wonder they are seeing nothing but Lorentz. First of all their twisted pairs do not appear to be twisted enough. There should be at least two twists per inch. In the image below it appears that there is maybe one twist per two inches or so. And then look at the location of the main amplifier and the length of the main leads!   :o

At only 2W of RF power, no wonder they are only seeing Lorentz. It's almost like they designed their experiment to be susceptible to this form of error.

« Last Edit: 05/21/2018 11:56 am by Monomorphic »

Offline Monomorphic

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I also avoided bundling the twisted pairs as that can lead to problems with the fields not cancelling out properly. Otherwise you have to use twisted pairs with different twist rates.

You can see in these images that my main power leads are one quarter or less the length of Tajmar and my twisted pairs are highly twisted.

I had 6.7A going to the centrally mounted amplifier yesterday and was not seeing these same problems.
« Last Edit: 05/21/2018 12:13 pm by Monomorphic »

Offline PotomacNeuron

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If the interaction with Earth magnetic field is the cause, they should be able to rotate their test apparatus (the entire thing, not the resonance cavity) horizontally to find an angle with which the interaction is minimized (theoretically, zero).

I am happy to see that they cited our father-and-daughter paper about the NASA experiment.

I took a look of their paper. It seems their giant test apparatus is build on top of a non-movable air table so it is very difficult if not impossible to rotate the "entire thing" horizontally.

They use magnet damping. It is not clear whether the magnets are mounted on the arm or on the frame. If they are mounted on the frame, the leaked magnetic field will interact with DC on arm to move the arm. If they are mounted on the arm, their leaked magnet field will interact with DC off-arm to move the arm.

They use multiple stepper motors. It is not clear whether there are permanent magnets in the stepper motors.

They have not talked about grounding schemes of the circuits thus it is unclear whether they have DC ground loop in their circuits. If there is, its effect is larger than how tight the twisting of the power leads is.
« Last Edit: 05/21/2018 03:14 pm by PotomacNeuron »
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Offline Star One

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Paper is now being widely reported by those still interested on social media and general consensus is that’s that case closed.

~20 twitter followers of Fraser Cain is hardly general consensus.

Looking at the pictures of Tajmar's experiment, no wonder they are seeing nothing but Lorentz. First of all their twisted pairs do not appear to be twisted enough. There should be at least two twists per inch. In the image below it appears that there is maybe one twist per two inches or so. And then look at the location of the main amplifier and the length of the main leads!   :o

At only 2W of RF power, no wonder they are only seeing Lorentz. It's almost like they designed their experiment to be susceptible to this form of error.

As I said in my OP that was merely an example of a wider discussion, or would you rather I have filled the post with Twitter links?

Offline Monomorphic

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As I said in my OP that was merely an example of a wider discussion, or would you rather I have filled the post with Twitter links?

I think the general scientific consensus has always been that the Emdrive does not work and it is a measurement artifact. However,  to claim that Tajmar's recent paper is "case closed" ignores the numerous problems identified with his experiment. 


« Last Edit: 05/21/2018 06:16 pm by Monomorphic »

Offline ThereIWas3

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It looks like they were expecting to get forces on the order of what Shawyer reported, so thought they could get away with being sloppy.
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Offline venir

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Quote
And so it remains infuriatingly ambiguous.  :-\

To me, it looked like a lean towards the negative, especially with the reference to earths magnetic field.

To quote the paper:
Quote
This  clearly  indicates  that  the  “thrust”  is  not coming  from  the  EMDrive  but  from  some electromagnetic  interaction. 
People should read the paper for details, but basically, they did a good null test that showed comparable thrust. Looking at the data in the paper, it looks like out of the 2 mN/kW that they measured, if there was a hidden real signal I estimate it would be below 0.5 mN/kW. Keep in mind that 0.003 mN/kW is a laser pointer, by which point an experiment would have to account for all forms of emitted and incident radiation.

They make a good point in the conclusion, which I agree with and is one reason I continue to read this thread:
Quote
At least,  SpaceDrive  is an  excellent educational project by developing highly demanding test setups, evaluating  theoretical  models  and  possible experimental errors. It’s a great learning experience with the  possibility  to  find  something that  can  drive space exploration into its next generation.
The accurate measurement techniques they are developing and ways to control various errors can have a variety of potential applications.

Ars Technica weighs in on the paper as well: https://arstechnica.com/science/2018/05/nasas-em-drive-is-a-magnetic-wtf-thruster/

Offline SteveD

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Um, this paper seems to be reporting a directional force in whatever direction certain feed lines are pointed, even in a shielded box.  This seems to argue the question, is this an actual force or a measurement error?  If an actual force can it be harnessed in a useful manner?  If it's an interaction with the earth's magnetic field that lets you move in any direction you want in earth orbit, without needing the weight of the can at the end, that would seem like a potentially useful application.

Offline M.LeBel

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Sometimes in science we may ask the question “why?” this or that happens. But the moment we start observing or measuring, it becomes a description, a relational point of view which can only bring back an answer in the form of “how” things work.

In my last FQXI essay (attached), I suggest a way to understand a valid “why?” question that would return an answer to the question “why” i.e. as a logical built-in causality.

This is without any claim as to the usefulness for the EM-Drive effort. It is a new and different angle under which one may examine physics...

Cheers,

Marcel,

Offline zen-in

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Lorentz force was investigated a lot by EW and others a couple of years back.   The part that cannot be ignored or explained away is the thrust is still there when an attenuator is used.    Another mechanism for error is the thermal movement of the metal when power is applied.   An attenuator will dissipate the same amount of power and cause the same kind of heating.   A few years ago I mentioned the thrust signature looked like a second order step response.   Heating is second order while a linear force is first order.

Offline oyzw

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Tajmar教授的腔体模态与杨涓教授的一致,极有可能是TE011模态,推力方向易出现180°反转。要确认推力是否来自腔体本身,可以采用对比法,将腔体替换成负载,看看是否依然存在推力,这个方法很简单

Offline flux_capacitor

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Tajmar教授的腔体模态与杨涓教授的一致,极有可能是TE011模态,推力方向易出现180°反转。要确认推力是否来自腔体本身,可以采用对比法,将腔体替换成负载,看看是否依然存在推力,这个方法很简单
Translation:
Prof. Tajmar's cavity mode is consistent with Prof. Yang's, most likely TE011. The direction of thrust seems to reverse when the cavity is flipped 180°. To confirm whether the thrust comes from the cavity itself, you can use a comparative method by replacing the cavity with the load and see if the thrust still exists. This method is very simple.

Offline RotoSequence

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Tajmar教授的腔体模态与杨涓教授的一致,极有可能是TE011模态,推力方向易出现180°反转。要确认推力是否来自腔体本身,可以采用对比法,将腔体替换成负载,看看是否依然存在推力,这个方法很简单
Translation:
Prof. Tajmar's cavity mode is consistent with Prof. Yang's, most likely TE011. The direction of thrust seems to reverse when the cavity is flipped 180°. To confirm whether the thrust comes from the cavity itself, you can use a comparative method by replacing the cavity with the load and see if the thrust still exists. This method is very simple.

Some of the earliest EM Drive experiments involved differential comparisons of these devices on a balance beam, mounted upside down and right side up. These experiments had too many uncontrolled variables, which led to the gradually more sophisticated test methods over the years. As sophistication has increased, the amount of "thrust" to be measured has decreased. Comparing the thrust in two different directions at this point would be a step backwards towards unaccounted for error sources, rather than meaningful measurements.

Offline Monomorphic

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Translation:
Prof. Tajmar's cavity mode is consistent with Prof. Yang's, most likely TE011. The direction of thrust seems to reverse when the cavity is flipped 180°. To confirm whether the thrust comes from the cavity itself, you can use a comparative method by replacing the cavity with the load and see if the thrust still exists. This method is very simple.

The big problem is that when Tajmar flips his frustum, he flips the entire experiment box, including the amplifier, other electrical components, and most of the wiring along with it. This doesn't really make much sense if you want to isolate the contribution of the frustum alone.
« Last Edit: 05/23/2018 12:03 pm by Monomorphic »

Offline flux_capacitor

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If the whole experiment can be rotated including the long wires, it is indeed not at all an experiment to measure the possible thrust produced by an EmDrive cavity, what a pity.

But if the Tajmar experiment is indeed an expensive giant compass, since the whole experiment can rigidly be positioned at various azimuthal angles, he could at least characterize it wrt the Earth magnetic field.
« Last Edit: 05/23/2018 12:23 pm by flux_capacitor »

Offline flux_capacitor

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Tajmar measured ~ 1 µN of force with only 2W of input power. According to Mike McCulloch (according to his theory of quantised inertia) thrust to power ratio does not add up in this 2018 experiment. At least his previous experiment (using a tiny oxidized cavity not even at full resonance and with a giant hole in the side wall to fit a waveguide) was consistent with QI.

« Last Edit: 05/23/2018 12:50 pm by flux_capacitor »

Offline SeeShells

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Translation:
Prof. Tajmar's cavity mode is consistent with Prof. Yang's, most likely TE011. The direction of thrust seems to reverse when the cavity is flipped 180°. To confirm whether the thrust comes from the cavity itself, you can use a comparative method by replacing the cavity with the load and see if the thrust still exists. This method is very simple.

The big problem is that when Tajmar flips his frustum, he flips the entire experiment box, including the amplifier, other electrical components, and most of the wiring along with it. This doesn't really make much sense if you want to isolate the contribution of the frustum alone.
Agreed Jamie!

Also note to do the rotation they used a stepper motor (I even have an stepper armature on my desk, a left over piece) and it is comprised of magnets. It could provide errors as well. It is something that shouldn't be used in a test stand in this arrangement.

My Very Best,
Shell

Offline Monomorphic

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If the whole experiment can be rotated including the long wires, it is indeed not at all an experiment to measure the possible thrust produced by an EmDrive cavity, what a pity.

In fact, I spent part of Saturday working on making sure I could flip the frustum 180. This 3D printed 2.4Ghz TE013 frustum is much larger than I anticipated when I started building the test stand. I always intended to be able to flip 90 and 180, but the large size of this frustum would have bumped up against the bottom cross beam when turned 180. So I removed the cross beam (which was not necessary anymore because of other modifications), and raised the test stand a few inches to give me plenty of clearance below.  I also confirmed that I can flip it 90. 

You can see the difference in the two images below.
« Last Edit: 05/23/2018 02:06 pm by Monomorphic »

Online meberbs

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Translation:
Prof. Tajmar's cavity mode is consistent with Prof. Yang's, most likely TE011. The direction of thrust seems to reverse when the cavity is flipped 180°. To confirm whether the thrust comes from the cavity itself, you can use a comparative method by replacing the cavity with the load and see if the thrust still exists. This method is very simple.

The big problem is that when Tajmar flips his frustum, he flips the entire experiment box, including the amplifier, other electrical components, and most of the wiring along with it. This doesn't really make much sense if you want to isolate the contribution of the frustum alone.
As RotoSequence said above, we are past the point where "flip and subtract" is the best method. The goal is to understand and remove error sources, rather than flip 180 Degrees and subtract, which will always potentially change something else. The attenuator test is there precisely because he knows the 180 degree flip may be flipping more than just the hypothetical thrust. (Also, more emDrive experiments should really do an attenuator test.)

Tajmar measured ~ 1 µN of force with only 2W of input power. According to Mike McCulloch (according to his theory of quantised inertia) thrust to power ratio does not add up in this 2018 experiment. At least his previous experiment (using a tiny oxidized cavity not even at full resonance and with a giant hole in the side wall to fit a waveguide) was consistent with QI.

That picture looks like stronger evidence than it is, since it uses data points from tests that we know were bad (like Shawyer, who handwaved away thrust direction flips with bad physics) Most of the rest are too clustered for a linear fit to mean much. The log-log scale disguises how much the bottom left corner would normally look like a giant scatter plot on its own.

Adding this new point to this graph does show that this experiment does provide new data pushing down the range of any potential thrust, by finally combining a well built cavity with enough removal of external error sources.

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