Author Topic: Woodward's effect  (Read 284567 times)

Offline ThinkerX

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Re: Woodward's effect
« Reply #980 on: 08/09/2017 07:08 AM »
Quote
With the foregoing in mind, we can now view the MEGA-drive as a power transistor like device with a given potential G/I energy to kinetic energy GAIN set by its design and operating point of the MEGA-drive engine in question.  That is why the equivalent Isp for these G/I field drives can be so astoundingly large.  (My STAIF-2006, Mach-Lorentz Thruster (MLT)-2004 had an equivalent Isp of ~1x10^12 seconds when producing ~3.0 milli-Newton with only 18 watts of local 2.2 MHz RF input power.)

Was that a vacuum chamber test?

Also, isn't that roughly 'EM Drive' levels of 'thrust?'  Perhaps 'movement' is a better term than 'thrust.'

Offline birchoff

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Re: Woodward's effect
« Reply #981 on: 08/09/2017 04:18 PM »
I found this slide but it's not that clear a picture. Even so, the part under energy and momentum is very interesting. It's the clearest and boldest statement I've seen yet on the energy conservation debate.

Bob:

It was a long time coming, but with the help of Dr. Rodal's NIAC analysis work and Carver Mead's previous observation that any non-rocket thruster with greater than 100% efficient photon rocket performance has to be harvesting energy from an outside source,  Dr. Woodward has finally accepted the fact that his Mach-Effect Gravity Assist (MEGA) drives have to develop ALL of their kinetic energy from the cosmological gravity/inertial (G/I) field that gives rise to inertia, but NOT from the local MEGA drive power supply.  So the vehicle's local power generators just supply the engine's internal losses required to set up and maintain the MEGA-drive's G/I energy conduit needed to propel the vehicle while in use. 

With the foregoing in mind, we can now view the MEGA-drive as a power transistor like device with a given potential G/I energy to kinetic energy GAIN set by its design and operating point of the MEGA-drive engine in question.  That is why the equivalent Isp for these G/I field drives can be so astoundingly large.  (My STAIF-2006, Mach-Lorentz Thruster (MLT)-2004 had an equivalent Isp of ~1x10^12 seconds when producing ~3.0 milli-Newton with only 18 watts of local 2.2 MHz RF input power.)

Best, Paul M.

Couple of questions.

Is there still a plan to update the book?

Also, while I believe successful completion of the NIAC work should be the highest priority. Is anyone working on characterizing what the possible limitations of this technology are? For example, would there be any real limitations on converting the imparted kinetic energy to electrical energy

Online dustinthewind

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Re: Woodward's effect
« Reply #982 on: 08/10/2017 03:09 AM »
I'm interested in better understanding Woodward's mass change formula, specifically the derivative of power with respect to time that constitutes the required energy change in the accelerating mass. Woodward currently uses a PZT stack and electrical power input. What other phenomenon might constitute the required energy change? Thanks.

My thinking are such things as fluctuations of kinetic energy and potential energy such as a system with a damped spring. Or sinusoidal fluctuations of the angular acceleration of a rotating mass concurrently undergoing translational accelerations? Things easy to experiment with that might yield big effects. I'm hoping there are much better systems than PZT stacks.

I was considering light as changing in effective mass inside a waveguide that changes diameter.  (I'm not convince of the mechanism that would change the lights effective mass in a narrowing waveguide yet, but the impulse of light does seem to change when light enters a high index material as measured by scientists). 

If the effective mass of light could change then I suspect it may be possible to use it for a Woodward effect.  Light could transition back and forth between regions that seem to effectively change mass which parallels to changing the effective mass of the PZT stack.  After changing its effective mass next is acceleration.  For light the acceleration happens upon reflection. 

If light gives more energy upon reflecting on one wall as opposed to another wall (by changing in mass) the light will lose energy or maybe it could be considered a change in frame (accelerating/decelerating light) and the back reaction would be to accelerate a cavity in the other direction.  Is this really possible?  No guarantees. 

I suspect this loss of energy from light is very similar to what happens in a photonic thruster where the energy lost from the photons is not through the Doppler effect but a 2nd order effect which also causes a change in frequency.
 

Much energy is lost when using photons as thrust.  Its very inefficient because of the photons ridiculously low effective mass.  The photonic laser thruster would be more efficient because of its ability to not lose so much energy to the photons.  Basically a photonic laser thruster more effectively sucks the energy from the photons by lowering their frequency via multiple reflections. 

The same would be true if you could change the mass of light inside a cavity and induce what I think might be similar to a Woodward effect.  https://en.wikipedia.org/wiki/Woodward_effect

I would suspect the change in effective mass would have some parallel to a coupling with the vacuum.  Possibly by relativity and the effective change in mass of a high velocity object. 

I could probably say more but not sure I want to.  I think there are other ways of possibly accomplishing the same thing. 
« Last Edit: 08/10/2017 03:14 AM by dustinthewind »

Offline Bob012345

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Re: Woodward's effect
« Reply #983 on: 08/10/2017 06:17 PM »
I'm interested in better understanding Woodward's mass change formula, specifically the derivative of power with respect to time that constitutes the required energy change in the accelerating mass. Woodward currently uses a PZT stack and electrical power input. What other phenomenon might constitute the required energy change? Thanks.

My thinking are such things as fluctuations of kinetic energy and potential energy such as a system with a damped spring. Or sinusoidal fluctuations of the angular acceleration of a rotating mass concurrently undergoing translational accelerations? Things easy to experiment with that might yield big effects. I'm hoping there are much better systems than PZT stacks.

I was considering light as changing in effective mass inside a waveguide that changes diameter.  (I'm not convince of the mechanism that would change the lights effective mass in a narrowing waveguide yet, but the impulse of light does seem to change when light enters a high index material as measured by scientists). 

If the effective mass of light could change then I suspect it may be possible to use it for a Woodward effect.  Light could transition back and forth between regions that seem to effectively change mass which parallels to changing the effective mass of the PZT stack.  After changing its effective mass next is acceleration.  For light the acceleration happens upon reflection. 

If light gives more energy upon reflecting on one wall as opposed to another wall (by changing in mass) the light will lose energy or maybe it could be considered a change in frame (accelerating/decelerating light) and the back reaction would be to accelerate a cavity in the other direction.  Is this really possible?  No guarantees. 

I suspect this loss of energy from light is very similar to what happens in a photonic thruster where the energy lost from the photons is not through the Doppler effect but a 2nd order effect which also causes a change in frequency.

Much energy is lost when using photons as thrust.  Its very inefficient because of the photons ridiculously low effective mass.  The photonic laser thruster would be more efficient because of its ability to not lose so much energy to the photons.  Basically a photonic laser thruster more effectively sucks the energy from the photons by lowering their frequency via multiple reflections. 

The same would be true if you could change the mass of light inside a cavity and induce what I think might be similar to a Woodward effect.  https://en.wikipedia.org/wiki/Woodward_effect

I would suspect the change in effective mass would have some parallel to a coupling with the vacuum.  Possibly by relativity and the effective change in mass of a high velocity object. 

I could probably say more but not sure I want to.  I think there are other ways of possibly accomplishing the same thing.

I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).
« Last Edit: 08/10/2017 06:20 PM by Bob012345 »

Offline ThinkerX

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Re: Woodward's effect
« Reply #984 on: 08/11/2017 01:17 AM »
Quote
I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

My recollection is hazy, but mention was made of a paper being presented at the Estes Conference describing something similar to this. 

Online dustinthewind

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Re: Woodward's effect
« Reply #985 on: 08/11/2017 06:58 AM »

I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

Well, there is, in a resonating cavity, a variance between inductance and capacitance.  There is a big difference however between transverse electric modes (TE) and transverse magnetic modes (TM). 

The TE mode avoids charge separation altogether which is interesting.  As a result the energy alternates from inductance in the cavity and existing as light. 

The TM modes induce charge separation and so the energy alternates between inductance (current in the cavity) and charge separation (capacitance in the cavity) and that of light.  I'm not sure how big the difference between them is yet but it might be significant. 

I'm not an expert on the Woodward effect but from what I gather I think it has to do with storing energy in something to make it more massive.  My guess is in the case of a pezio-electric accelerator the idea is to shift energy from being stored in a material that is accelerated (say an inductor) to a device that is not repeatedly accelerated (maybe a capacitor) and back again. 

The stored energy makes it heavier or more coupled to the vacuum (maybe enhanced via some odd effect).  When it is pulled, it being heavier, drags on the vacuum in one direction and the device the other direction.  Shunting the energy out of the inductor decouples it from the vacuum (or virtual particles) and it's pushed back to start the process over again. 

If a cavity could mimic this effect I suspect the energy would have to alternate between something that is being accelerated to something that is not accelerated and back again.  Some how I suspect this would also effect the light inside the cavity.  The increase in mass of a charge may effect its field, and light is the field. 

https://en.wikipedia.org/wiki/Effective_mass_(solid-state_physics)

Virtual particles
...
While an electron–positron virtual pair is in existence, the coulomb force from the ambient electric field surrounding an electron causes a created positron to be attracted to the original electron, while a created electron experiences a repulsion. This causes what is called vacuum polarization. In effect, the vacuum behaves like a medium having a dielectric permittivity more than unity. Thus the effective charge of an electron is actually smaller than its true value, and the charge decreases with increasing distance from the electron.[87][88] This polarization was confirmed experimentally in 1997 using the Japanese TRISTAN particle accelerator.[89] Virtual particles cause a comparable shielding effect for the mass of the electron.[90]

It may be interesting to see that paper spoken about above. 
« Last Edit: 08/11/2017 07:28 AM by dustinthewind »

Offline Bob012345

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Re: Woodward's effect
« Reply #986 on: 08/11/2017 05:43 PM »

I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

Well, there is, in a resonating cavity, a variance between inductance and capacitance.  There is a big difference however between transverse electric modes (TE) and transverse magnetic modes (TM). 

The TE mode avoids charge separation altogether which is interesting.  As a result the energy alternates from inductance in the cavity and existing as light. 

The TM modes induce charge separation and so the energy alternates between inductance (current in the cavity) and charge separation (capacitance in the cavity) and that of light.  I'm not sure how big the difference between them is yet but it might be significant. 

I'm not an expert on the Woodward effect but from what I gather I think it has to do with storing energy in something to make it more massive.  My guess is in the case of a pezio-electric accelerator the idea is to shift energy from being stored in a material that is accelerated (say an inductor) to a device that is not repeatedly accelerated (maybe a capacitor) and back again. 

The stored energy makes it heavier or more coupled to the vacuum (maybe enhanced via some odd effect).  When it is pulled, it being heavier, drags on the vacuum in one direction and the device the other direction.  Shunting the energy out of the inductor decouples it from the vacuum (or virtual particles) and it's pushed back to start the process over again. 

If a cavity could mimic this effect I suspect the energy would have to alternate between something that is being accelerated to something that is not accelerated and back again.  Some how I suspect this would also effect the light inside the cavity.  The increase in mass of a charge may effect its field, and light is the field. 

https://en.wikipedia.org/wiki/Effective_mass_(solid-state_physics)

Virtual particles
...
While an electron–positron virtual pair is in existence, the coulomb force from the ambient electric field surrounding an electron causes a created positron to be attracted to the original electron, while a created electron experiences a repulsion. This causes what is called vacuum polarization. In effect, the vacuum behaves like a medium having a dielectric permittivity more than unity. Thus the effective charge of an electron is actually smaller than its true value, and the charge decreases with increasing distance from the electron.[87][88] This polarization was confirmed experimentally in 1997 using the Japanese TRISTAN particle accelerator.[89] Virtual particles cause a comparable shielding effect for the mass of the electron.[90]

It may be interesting to see that paper spoken about above.

I'm not an expert on the Woodward effect (but I'd like to be!) but I think the increased mass is not just E/c^2 of the added energy. That would require massive energy densities. It's a fundamentally different interaction with the rest of the mass in the universe.

Offline Bob012345

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Re: Woodward's effect
« Reply #987 on: 08/11/2017 05:48 PM »
Quote
I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

My recollection is hazy, but mention was made of a paper being presented at the Estes Conference describing something similar to this.

Thanks, I have the proceedings. If you remember which paper it is please let me know. I'm beginning to suspect that there may be many ways of pumping massive amounts energy into an accelerating system that might work to get big effects.

Offline WarpTech

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Re: Woodward's effect
« Reply #988 on: 08/11/2017 08:39 PM »
Quote
I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

My recollection is hazy, but mention was made of a paper being presented at the Estes Conference describing something similar to this.

Thanks, I have the proceedings. If you remember which paper it is please let me know. I'm beginning to suspect that there may be many ways of pumping massive amounts energy into an accelerating system that might work to get big effects.

Jean-Philippe Montillet's paper is about the similarity between the Em Drive cavity and the Mach effect.


Offline flux_capacitor

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Re: Woodward's effect
« Reply #989 on: 08/13/2017 04:00 PM »
Quote
I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

My recollection is hazy, but mention was made of a paper being presented at the Estes Conference describing something similar to this.

Thanks, I have the proceedings. If you remember which paper it is please let me know. I'm beginning to suspect that there may be many ways of pumping massive amounts energy into an accelerating system that might work to get big effects.

Jean-Philippe Montillet's paper is about the similarity between the Em Drive cavity and the Mach effect.

Yes, as quoted on the Wikipedia page about the EmDrive, section Mach effect:

"The RF resonant cavity thruster would act as a capacitor where surface currents propagate inside the cavity on the conic wall, between the two end plates; electromagnetic resonant modes create electric charges on each end plate; a Mach effect is triggered by Lorentz forces from surface currents on the conic wall; and a thrust force arise in the RF cavity, due to the variation of the electromagnetic density from evanescent waves inside the skin layer. When a polymer insert is placed asymmetrically in the cavity, its dielectric properties result in greater asymmetry, while decreasing the cavity Q factor. The cavity's acceleration is a function of all the above factors, and the model can explain the acceleration of the cavity with and without a dielectric."

And the link to Montillet's paper:

Montillet, J.P. (September 2016). "Theory of the EM Drive in TM mode based on Mach-Lorentz theory". Proceedings of the Advanced Propulsion Workshop. Estes Park, CO: Space Studies Institute. pp. 111–125.

The PDF file of the Estes Park Proceedings is very interesting but quite large to download and handle, so here is Montillet's paper extracted and attached below.

Offline Bob012345

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Re: Woodward's effect
« Reply #990 on: 08/16/2017 09:06 PM »
Quote
I like it! It could be just the rapid change in energy in the cavity as it builds up and is released that might trigger the Woodward effect as the cavity and it's medium is appropriately accelerated and each has the appropriate frequency (as I understand the mass fluctuation term).

My recollection is hazy, but mention was made of a paper being presented at the Estes Conference describing something similar to this.

Thanks, I have the proceedings. If you remember which paper it is please let me know. I'm beginning to suspect that there may be many ways of pumping massive amounts energy into an accelerating system that might work to get big effects.

Jean-Philippe Montillet's paper is about the similarity between the Em Drive cavity and the Mach effect.

Yes, as quoted on the Wikipedia page about the EmDrive, section Mach effect:

"The RF resonant cavity thruster would act as a capacitor where surface currents propagate inside the cavity on the conic wall, between the two end plates; electromagnetic resonant modes create electric charges on each end plate; a Mach effect is triggered by Lorentz forces from surface currents on the conic wall; and a thrust force arise in the RF cavity, due to the variation of the electromagnetic density from evanescent waves inside the skin layer. When a polymer insert is placed asymmetrically in the cavity, its dielectric properties result in greater asymmetry, while decreasing the cavity Q factor. The cavity's acceleration is a function of all the above factors, and the model can explain the acceleration of the cavity with and without a dielectric."

And the link to Montillet's paper:

Montillet, J.P. (September 2016). "Theory of the EM Drive in TM mode based on Mach-Lorentz theory". Proceedings of the Advanced Propulsion Workshop. Estes Park, CO: Space Studies Institute. pp. 111–125.

The PDF file of the Estes Park Proceedings is very interesting but quite large to download and handle, so here is Montillet's paper extracted and attached below.

This paper is discussing one particular model to explain current EM drive results in light of Mach theory and suggests ways to falsify the theory. Also it relies on skin effects in the copper frustum and not bulk radiation properties as we were discussing. I'm not clear on the requirements of the relationship between the energy fluctuations and any material structure it is assumed to be fluctuating inside of.

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #991 on: 09/07/2017 08:13 PM »
I agree. The fact these devices exist and some show fairly good theoretical and experimental tracks (the MEGA is low thrust but very consistent) is exciting indeed.

You said MEGA produces consistent thrust among experiments. I am curious to take a look. Which experiment is the most detailed with photos and descriptions? Would you suggest one? Thank you!

Somebody sent me a link but his post was deleted so I do not know who did that. The link leads to a pdf file describing a proposal to expand the MEGA thrust. I googled online and found the paper referred in the pdf file. It is here:

http://www.tsijournals.com/articles/experimental-tests-of-the-mach-effect-thruster.pdf

I took a look of the pictures without looking into the theory part. This experiment troubles me a lot. Because I think the appearance of a thrust can be explained with regular mechanism without having to fetch Mach effect, Woodward effect, or alike. Think of the fact that you can moving a car/cart forward by rocking in it. A friction with ground in this car/cart experiment is needed. As to the experiment in the paper, if the experiment was not carried out in vacuum, then air friction must be considered. The beam in the experiment will jerk quickly back and forth. look into how a jellyfish swim in water,

 The air turbulence interacting with some non-symmetric parts of the experiment apparatus will make this effect.  Even if the apparatus is symmetrical, if the beam jerk quickly toward one direction and move back slowly from another direction (think of the "chirp" part of the experiment), a thrust like effect may still be able to show up.

If the experiment was carried out in vacuum, close look of the bearing is needed. A hanging piano wire will be very helpful to serve as low friction bearing. If they have not taken measurement of this effect, then the conclusion is very skeptical. I think, if I mounting some non-symmetric parts on the beam to interact with air turbulence, I probably can reverse the thrust direction of that experiment. Dare to let me try, somebody?

Update: I know a device invented in the 50's by somebody (the name may bear a "wood" in it), documented on Wiki, showing that a closed system with moving parts can move itself on desk. It stirred much interest at its time as and propellant-less driver. We need to learn lessons from history. I worry that we do not include enough failed theory/invention in text books. For every successful theory, there may be more than 100 failed one. If we forget them, we may think the new theory we invent having much much higher chance to be successful than it really has.

Edited many times to correct grammar problems.
« Last Edit: 09/07/2017 08:25 PM by PotomacNeuron »
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Offline PotomacNeuron

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Re: Woodward's effect
« Reply #992 on: 09/07/2017 08:35 PM »

moved from the EmDrive thread:
Quote
Quote from: Rodal on Today at 08:25 PM
1) You are in the wrong thread to be arguing this.  There is a thread exclusively devoted to the Woodward effect where you should move your discussion.
2) Contrary to what you imply, the experiments (and the paper you quote) were all conducted in a vacuum.
3) There is a null experiment: for a symmetric system, for example, having equal end masses, the experimental force is zero.
I am glad to learn that they are carried out in vacuum. For 3), in vacuum, it is expected to produce no force if it has equal end masses. This can be explained by regular mechanism that the jerking is canceled that it can not interact with friction. If somebody has a demonstration of the experiment near DC, I'd be very interested to take a personal look.
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Offline flux_capacitor

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Re: Woodward's effect
« Reply #993 on: 09/07/2017 08:55 PM »
Quote from: Rodal
{…}
3) There is a null experiment: for a symmetric system, for example, having equal end masses, the experimental force is zero.
For 3), in vacuum, it is expected to produce no force if it has equal end masses. This can be explained by regular mechanism that the jerking is canceled that it can not interact with friction. If somebody has a demonstration of the experiment near DC, I'd be very interested to take a personal look.

Are you implying the device would produce an apparent force (but no real thrust) with asymmetric masses at both ends and in a vacuum? BTW the friction engines from the 1950s you are talking about are "Dean drives". So are you thinking Woodward's MEGA drive may be a Dean drive?

And precisely, the last paragraph of the Wikipedia page about Dean drives tells the following:
Quote from: Wikipedia
In 2012 a researcher attempting to characterize the Woodward effect, another proposed reactionless drive effect, has stated that she carefully designed her experiments to specifically exclude any "Dean drive" effects: the unintended interaction with the environment in, around or touching the apparatus. She considered these effects "spurious noise".[18]

[18] Fearn, Heidi; Woodward, James F. (2013). "Experimental Null test of a Mach Effect Thruster". arXiv:1301.6178.
This paper has been published in the Journal of Space Exploration July 29, 2013.

Summarised in the two following slides in Fearn's lecture presented October 5, 2012 at the Advanced Space Propulsion Workshop (ASPW 2012) held at NASA's Marshall Space Flight Center, Huntsville, AL:
« Last Edit: 09/07/2017 09:07 PM by flux_capacitor »

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #994 on: 09/07/2017 08:56 PM »
I have not yet thought out a way to prove that this device work or not on Earth, because I can not find a friction-less bearing and/or hysteresis-free magnetic environment. Maybe it's worth it to test this device on a satellite because it is much easier to make and maintain than an EmDrive.
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Offline Rodal

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Re: Woodward's effect
« Reply #995 on: 09/07/2017 09:01 PM »

moved from the EmDrive thread:
Quote
Quote from: Rodal on Today at 08:25 PM
1) You are in the wrong thread to be arguing this.  There is a thread exclusively devoted to the Woodward effect where you should move your discussion.
2) Contrary to what you imply, the experiments (and the paper you quote) were all conducted in a vacuum.
3) There is a null experiment: for a symmetric system, for example, having equal end masses, the experimental force is zero.
I am glad to learn that they are carried out in vacuum. For 3), in vacuum, it is expected to produce no force if it has equal end masses. This can be explained by regular mechanism that the jerking is canceled that it can not interact with friction. If somebody has a demonstration of the experiment near DC, I'd be very interested to take a personal look.
For a personal look you can arrange for a visit with Prof. Woodward at CalState Fullerton.

Concerning friction, p. 153 of his book states:

Quote
In order to get a quantitative measure of the vibration communicated to the flexural
bearings supporting the balance beam – the only place where a Dean drive effect could act
to produce a spurious thrust-like effect – accelerometers were attached to the central part
of the beam in proximity to the lower flexural bearing. The accelerometers were fabricated
from 2-mm square pieces of thin PZT material, a brass electrode and a 2-mm square brass
“anvil” mass (1 mm thick). See Fig. 5.16.
The electrode is placed between the pieces of PZT (oriented with appropriate
polarizations), and the anvil mass is part of the ground circuit, locally grounded. In
order to suppress pickup that might appear on the accelerometer leads, the signals from
the accelerometer were detected with a differential amplifier so that pickup would be
rejected as common mode noise. The usual precautions were taken with the electronics.
These accelerometers made it possible to show that reversal of the direction of the device
on the end of the beam had no effect on the vibration reaching the flexural bearings in the
central column of the balance – but the observed thrust signal changed direction with the
device. See Fig. 5.17.

« Last Edit: 09/07/2017 09:04 PM by Rodal »

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #996 on: 09/07/2017 09:02 PM »
Quote from: Rodal
{…}
3) There is a null experiment: for a symmetric system, for example, having equal end masses, the experimental force is zero.
For 3), in vacuum, it is expected to produce no force if it has equal end masses. This can be explained by regular mechanism that the jerking is canceled that it can not interact with friction. If somebody has a demonstration of the experiment near DC, I'd be very interested to take a personal look.

Are you implying the device would produce an apparent force (but no real thrust) with asymmetric masses at both ends and in a vacuum? BTW the friction engines from the 1950s you are talking about are "Dean drives". So are you thinking Woodward's MEGA drive may be a Dean drive?

And precisely, the last paragraph of the Wikipedia page about Dean drives tells the following:
Quote from: Wikipedia
In 2012 a researcher attempting to characterize the Woodward effect, another proposed reactionless drive effect, has stated that she carefully designed her experiments to specifically exclude any "Dean drive" effects: the unintended interaction with the environment in, around or touching the apparatus. She considered these effects "spurious noise".[18]

[18] Fearn, Heidi; Woodward, James F. (2013). "Experimental Null test of a Mach Effect Thruster". arXiv:1301.6178.


Yes, that is what I think, that a bearing with friction or hysteresis effect may produce an appearance of thrust. Or it can be the magnetic interaction with environment magnetic field with hysteresis effect. Thank you for the name "Dean drive". I was referring to it but forgot its name.
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Offline PotomacNeuron

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Re: Woodward's effect
« Reply #997 on: 09/07/2017 09:12 PM »

moved from the EmDrive thread:
Quote
Quote from: Rodal on Today at 08:25 PM
1) You are in the wrong thread to be arguing this.  There is a thread exclusively devoted to the Woodward effect where you should move your discussion.
2) Contrary to what you imply, the experiments (and the paper you quote) were all conducted in a vacuum.
3) There is a null experiment: for a symmetric system, for example, having equal end masses, the experimental force is zero.
I am glad to learn that they are carried out in vacuum. For 3), in vacuum, it is expected to produce no force if it has equal end masses. This can be explained by regular mechanism that the jerking is canceled that it can not interact with friction. If somebody has a demonstration of the experiment near DC, I'd be very interested to take a personal look.
For a personal look you can arrange for a visit with Prof. Woodward at CalState Fullerton.

Concerning friction, p. 153 of his book states:

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In order to get a quantitative measure of the vibration communicated to the flexural
bearings supporting the balance beam – the only place where a Dean drive effect could act
to produce a spurious thrust-like effect – accelerometers were attached to the central part
of the beam in proximity to the lower flexural bearing. The accelerometers were fabricated
from 2-mm square pieces of thin PZT material, a brass electrode and a 2-mm square brass
“anvil” mass (1 mm thick). See Fig. 5.16.
The electrode is placed between the pieces of PZT (oriented with appropriate
polarizations), and the anvil mass is part of the ground circuit, locally grounded. In
order to suppress pickup that might appear on the accelerometer leads, the signals from
the accelerometer were detected with a differential amplifier so that pickup would be
rejected as common mode noise. The usual precautions were taken with the electronics.
These accelerometers made it possible to show that reversal of the direction of the device
on the end of the beam had no effect on the vibration reaching the flexural bearings in the
central column of the balance – but the observed thrust signal changed direction with the
device. See Fig. 5.17.

Thank you for the contact information. It is too far away for me to visit Cal State, though.

Besides the bearing, the hysteresis of the beam elastic bending may play a role too. I need to think hard to find a way to remove all those effects.
I am working on the ultimate mission human beings are made for.

Offline Rodal

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Re: Woodward's effect
« Reply #998 on: 09/07/2017 09:19 PM »
...
Thank you for the contact information. It is too far away for me to visit Cal State, though.

Besides the bearing, the hysteresis of the beam elastic bending may play a role too. I need to think hard to find a way to remove all those effects.
If you are discussing stress-strain hysteresis with plastic deformation (as it occurs with friction) in the torsional pendulum aluminum beam the word hysteresis contradicts your word "elastic bending" as there is no hysteresis in a perfectly elastic material. The torsional pendulum aluminum beam is made of aerospace aluminum grade, if you consider the fact that a metal like aluminum eventually does exhibit plasticity hysteresis due to pile-up of dislocations, (which is a non-elastic phenomenon) it is trivial to calculate that the strains in the beam are infinitesimal (since the device has a mass of less than 200 grams) and therefore plastic hysteresis of the beam is non-existent, since the strains in the beam are orders of magnitude below the yield strain.  Aerospace engineers reading this that are familiar with fatigue calculations and elastic-plastic deformations in metals will realize this at once.  Stress-strain hysteresis due to plastic strain in the aluminum beam is much more unrealistic than discussing friction in the bearing.

For infinitesimal strains, at ~30 kHz, there is dissipation in Aluminum which can be characterized by tan delta, this is structural damping (stress-strain hysteresis such that there is no permanent strain upon unloading, the strain being zero upon unloading: no plastic strains, which is an effect unlike friction).  Tan delta for aluminum is very small ~10^(-3): see graph

« Last Edit: 09/07/2017 09:52 PM by Rodal »

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #999 on: 09/07/2017 09:25 PM »
...
Thank you for the contact information. It is too far away for me to visit Cal State, though.

Besides the bearing, the hysteresis of the beam elastic bending may play a role too. I need to think hard to find a way to remove all those effects.
If you are discussing stress-strain hysteresis in the aluminum beam, the beam is made of aerospace aluminum grade, it is trivial to calculate that the strains in the beam are infinitesimal and therefore hysteresis of the beam is non-existent, since the strains in the beam are orders of magnitude below the yield strain.  Aerospace engineers reading this that are familiar with fatigue calculations and elastic-plastic deformations in metals will realize this at once.

Thanks. The fact that the masses vibrate quickly and intensely worries me. There are just too many places this can cause problems. I need to think and read when I get some more time.
I am working on the ultimate mission human beings are made for.