Author Topic: EM Drive Developments Thread 1  (Read 765977 times)

Offline Mulletron

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Re: EM Drive Developments
« Reply #380 on: 08/24/2014 12:48 PM »
Just found this gem. Wanted to share it:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140000851.pdf

Seriously cool stuff. I'm in awe.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Mulletron

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Re: EM Drive Developments
« Reply #381 on: 08/24/2014 01:02 PM »
Full paper regarding recent NASA test campaigns of emdrive and cannae:

http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf


Anyone know any ways to increase the rate of quantum fluctuations and produce a greater flux of particle/antiparticle pairs? I got an indication earlier that this happens within dielectrics to a degree. (think it was the NASA slide show) Would a really strong electric charge field work, like in a capacitor across a dielectric? Could a strong enough electric field cause these virtual particle pairs to be ripped apart before they annihilate? If so, are these energy levels realistic or very high energy stuff? I know that high energy photon interactions with atomic nuclei can cause pair production if the energy of the photons is twice the rest mass of the particle, like for electrons, it is .511 MeV I think it was. So you need high energy photons. Any way to lower the energy requirement? A lower energy requirement would allow us to use lower frequencies. That's the goal I'm shooting for here. Radio frequencies instead of Gamma. Thoughts anyone?

« Last Edit: 08/24/2014 01:07 PM by Mulletron »
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Offline Avron

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Re: EM Drive Developments
« Reply #382 on: 08/24/2014 01:11 PM »
Thoughts anyone?

Not enough power,.. if 1Kw can make it vibrate.. 1 Mw should make it move

Offline Mulletron

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Re: EM Drive Developments
« Reply #383 on: 08/24/2014 01:26 PM »
Well I can't see power being the major engineering problem here. I work with RF in my day job and power out isn't that big a deal, but higher frequencies, which equates to higher photon energies could be a problem. A waveguide for gamma rays, if you could contain them, would be very tiny. Focusing x-rays and gamma rays is a pain too.
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Offline Avron

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Re: EM Drive Developments
« Reply #384 on: 08/24/2014 01:40 PM »
Well I can't see power being the major engineering problem here. I work with RF in my day job and power out isn't that big a deal, but higher frequencies, which equates to higher photon energies could be a problem. A waveguide for gamma rays, if you could contain them, would be very tiny. Focusing x-rays and gamma rays is a pain too.

Question,, has anyone measured the counter force, if any to the Sagnac effect?

Offline Mulletron

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Re: EM Drive Developments
« Reply #385 on: 08/24/2014 01:52 PM »
Well I can't see power being the major engineering problem here. I work with RF in my day job and power out isn't that big a deal, but higher frequencies, which equates to higher photon energies could be a problem. A waveguide for gamma rays, if you could contain them, would be very tiny. Focusing x-rays and gamma rays is a pain too.

Question,, has anyone measured the counter force, if any to the Sagnac effect?

I'm familiar with this concept from gyros. Basically you split a laser beam and make each travel around a half circle to a detector. If the circle rotates, one laser beam will travel a longer path and the other a shorter path, which is picked up at the detector. How does this apply here? What are you getting at?
Challenge your preconceptions, or they will challenge you. - Velik

Online Stormbringer

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Re: EM Drive Developments
« Reply #386 on: 08/24/2014 02:47 PM »
Well I can't see power being the major engineering problem here. I work with RF in my day job and power out isn't that big a deal, but higher frequencies, which equates to higher photon energies could be a problem. A waveguide for gamma rays, if you could contain them, would be very tiny. Focusing x-rays and gamma rays is a pain too.
if i understand correctly there has recently been a development in controlling gamma rays with meta materials or something like that. i vaguely recall something about meta-materials allowing lensing or refracting gamma rays and it having implications for smaller gamma ray telescopes and possibly other applications like lasers and so forth.
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Offline Mulletron

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Online Stormbringer

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Re: EM Drive Developments
« Reply #388 on: 08/25/2014 04:48 AM »
Full paper regarding recent NASA test campaigns of emdrive and cannae:

http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf


Anyone know any ways to increase the rate of quantum fluctuations and produce a greater flux of particle/antiparticle pairs? I got an indication earlier that this happens within dielectrics to a degree. (think it was the NASA slide show) Would a really strong electric charge field work, like in a capacitor across a dielectric? Could a strong enough electric field cause these virtual particle pairs to be ripped apart before they annihilate? If so, are these energy levels realistic or very high energy stuff? I know that high energy photon interactions with atomic nuclei can cause pair production if the energy of the photons is twice the rest mass of the particle, like for electrons, it is .511 MeV I think it was. So you need high energy photons. Any way to lower the energy requirement? A lower energy requirement would allow us to use lower frequencies. That's the goal I'm shooting for here. Radio frequencies instead of Gamma. Thoughts anyone?

well i remember a positron generator that used a laser to create a dynamical casimir mirror or other effect that produced and separated positrons (i guess they threw the electrons away or left them unused) so i have seen something like that. all the hooplah was over the fact that it would sit on half a desktop for a footprint. it was at one of the national labs.
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Offline sghill

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Re: EM Drive Developments
« Reply #389 on: 09/02/2014 08:10 PM »
OK,. I know we beat the heck out of this topic, but I had a thought over the weekend I wanted to float.

What if the EMDrives that Eagleworks tested were acting like a heat engine such as you'd find in a Crookes radiometer instead? 

If the microwaves imparted energy unevenly on the internal surface of the "thruster" and the test article, then it could generate the thrust as blackbody radiation warming air molecules just like in a Crookes radiometer that the torsion balance could have picked up.    http://en.wikipedia.org/wiki/Crookes_radiometer

They didn't test the things in a vacuum where this effect would not have occurred, which is why I thought it may be a possibility.
« Last Edit: 09/02/2014 08:13 PM by sghill »
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Offline Star One

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Re: EM Drive Developments
« Reply #390 on: 09/02/2014 09:10 PM »
I thought it was tested in a vacuum chamber.

Offline QuantumG

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Re: EM Drive Developments
« Reply #391 on: 09/02/2014 09:13 PM »
Radiometers do work in a vacuum, just not particularly well.
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Offline MP99

Re: EM Drive Developments
« Reply #392 on: 09/02/2014 10:01 PM »
I thought it was tested in a vacuum chamber.
Yup, bat at 1 atmosphere.

Capacitors couldn't take vac, IIRC.

Cheers, Martin

Offline JPLeRouzic

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Re: EM Drive Developments
« Reply #393 on: 09/03/2014 07:13 AM »
NASA has its own list of capacitors that includes aluminum capacitors with solid conductive polymer as the electrolyte material that are compatible with the wide range of requirements for working in space conditions.

BTW your iPhone and most modern miniaturized electronic devices use capacitors with the same technology because no bulky wet capacitor would fit the form factor.

On a completely unrelated topic, unfortunately this kind of capacitor fuels wars in central Africa.

Offline MP99

Re: EM Drive Developments
« Reply #394 on: 09/03/2014 07:36 AM »
NASA has its own list of capacitors that includes aluminum capacitors with solid conductive polymer as the electrolyte material that are compatible with the wide range of requirements for working in space conditions.

BTW your iPhone and most modern miniaturized electronic devices use capacitors with the same technology because no bulky wet capacitor would fit the form factor.

On a completely unrelated topic, unfortunately this kind of capacitor fuels wars in central Africa.
Isn't this a far higher power level than iPhone?

Cheers, Martin

Offline JPLeRouzic

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Re: EM Drive Developments
« Reply #395 on: 09/03/2014 08:22 AM »
=>It depends about what you discuss, while I agree that EmDrive uses hundreds watts, the EagleWorks device just used 17 Watts.
It is not far from the power needed by an iPhone cellular 3G emitter (max 5 Watts but the emitter is quite inefficient).
And we don't know the circuit purpose and design where a capacitor was used, so we can't make any prediction about what power this capacitor must support. This kind of capacitor (wet or solid) is not used to filter out gigahertz.
But that's not my point, it was about technology of capacitors, not about the specific value of capacitance nor the typical power it can support. iPhones as most other consumer devices use solid polymer capacitors.

Online Stormbringer

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Re: EM Drive Developments
« Reply #396 on: 09/03/2014 12:02 PM »
I thought it was tested in a vacuum chamber.
Yup, bat at 1 atmosphere.

Capacitors couldn't take vac, IIRC.

Cheers, Martin
That is true and kind of inexplicable, really. But Dr Woodward tested his version of this thing in a vacuum. conclusion: this general class of device works in a vacuum.
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Offline sghill

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Re: EM Drive Developments
« Reply #397 on: 09/03/2014 12:49 PM »
Radiometers do work in a vacuum, just not particularly well.

That's not the point here.  The point is that the "drive" may have inadvertently worked like a Crookes radiometer heat engine.  A Crookes radiometer stops working in a full vacuum because there are no air molecules for the radiant energy absorbed on black side of the radiometer to excite, and the friction of the spinner can't be overcome by the light pressure on the silvered side.  It works best in a partial vacuum (read the wiki article) and it also works backwards compared to what you'd expect from a light pressure powered solar sail.

In the case of the EMDrive test articles, if the microwaves created uneven heating of the interior surfaces at normal air pressure, those surfaces could have warmed the air molecules and created the thrust detected by the very sensitive torsion balance. 

If this was indeed the case, then if they repeat the experiment in a full vacuum, the thrust effect will go away.  If it doesn't go away, then perhaps they are on to something.
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Offline JasonAW3

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Re: EM Drive Developments
« Reply #398 on: 09/03/2014 01:49 PM »
NASA has its own list of capacitors that includes aluminum capacitors with solid conductive polymer as the electrolyte material that are compatible with the wide range of requirements for working in space conditions.

BTW your iPhone and most modern miniaturized electronic devices use capacitors with the same technology because no bulky wet capacitor would fit the form factor.

On a completely unrelated topic, unfortunately this kind of capacitor fuels wars in central Africa.
Isn't this a far higher power level than iPhone?

Cheers, Martin

Wile I was in the NAVY, I saw solid capaciter units hooked up to the radar systems that would make you plotz!  These things were MONSTERS!

      I suddenly understood why we would sometimes find partially cooked dead birds up on the Radar antenna level on board ship.  And THIS was beck in the 1980's!
My God!  It's full of universes!

Offline Rodal

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Re: EM Drive Developments
« Reply #399 on: 09/07/2014 07:06 PM »
I have concluded that thermal transient effects are a likely explanation for the measured deflections and forces in NASA's torsion pendulum experiments of the Q drives.  Explicitly, that they are the result of a shift in material location of the center of mass due to differential thermal expansion resulting from heating of the dielectric resonator which is positioned unsymmetrically.  If this explanation is correct, Dr. White still should also be able to measure (slightly lower) forces when he places the Q drive in a torsion pendulum in a vacuum.  However, if the Q drive were free in space (instead of supported from a pendulum), this transient, unsymmetric, thermal expansion would result only in a change in attitude (orientation).

I am posting here my letter to Dr. White in order to have a wider review of this explanation. 

Dear Dr. White,

I have read with appreciable interest your paper (co-authored with D. Brady, P. March, J. Lawrence, and F. Davies) titled "Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum", presented at the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, July 28-30, 2014 in Cleveland, OH.

I have thought about what may be responsible for the measured displacement (and force) in your reported torsion pendulum experiments.  Air convection resulting from microwave heating of the air surrounding the Q-drives has been suggested by various people, as the air speed that can produce the measured force can be shown to be small.  You will be able to check whether air convection is responsible when you perform experiments in a vacuum (which I understand from your report was not possible because of the aluminum electrolytic capacitors that need to be replaced by capacitors that can work in a vacuum environment).

However, I have wondered how air convection could be responsible for the reproducible and fairly consistent levels of measured force pulse, as well as the fact that the experimental pulses are so well defined (and that it took practically no time to achieve the measured forces and to go back to zero upon ending the microwave pulse), and that turning the Q-drive around by 180 degrees resulted in practically the same force in the opposite direction.

Based on my experience conducting experiments at the Massachusetts Institute of Technology Aeronautics and Astronautics Department (for my S.B., S.M. and Ph.D. degrees at MIT) and later on at industrial R&D laboratories, I have arrived at the conclusion that transient thermal effects in your experiments should be carefully considered.

Indeed, after much thought and some calculations my conclusion is that the measured forces can quite likely be the result of transient thermal effects that very slightly shift the location of the center of mass in the material body of the Q-drive, due to unsymmetric thermal expansion, resulting from internal heating of the dielectric resonator in the Q-drive.

The center of mass changes location in the material body, with respect to body-fixed, Lagrangian coordinates, as it expands unsymmetrically.  If the body would be free (unrestrained) in space, this would result only in a change in attitude (orientation) of the body. If free in space, the spatial position of the center of mass will not change (with respect to an inertial frame of reference).  However, because the tested Q-drives were restrained, suspended from a support point in a torsion pendulum, the unsymmetric thermal expansion will generate a small measurable rotation and (torquing) force because the center of mass changes location in the material body as it expands unsymmetrically. 


Similar issues (thermal distortion resulting in changes in orientation) were experienced, for example in spacecraft, most prominently with the Messenger (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft that got closer to the Sun:  See:  http://messenger.jhuapl.edu/the_mission/publications/O'Shaughnessy_Pittelkau.2007.pdf

Interestingly, your paper points out the importance of the (Teflon) dielectric resonator concerning the experimentally measured forces:

<<The longer beam pipe is the RF drive antenna that in practice ends up being a wave resonance system in its own right and has a dielectric PTFE slug in the throat in both the slotted and null test article. It is this characteristic that became an item of further consideration after completion of the test campaign.>> (p.7)

<<There appears to be a clear dependency between thrust magnitude and the presence of some sort of dielectric RF resonator in the thrust chamber.>> (p.18)

<<We performed some very early evaluations without the dielectric resonator (TE012 mode at 2168 MHz, with power levels up to ~30 watts) and measured no significant net thrust.>>( p.18)

It is noteworthy that the test conducted without the dielectric resonator resulted in no significant measurable force. 

My analysis of the reaction force that results from the greater thermal expansion of the drive adjacent  to the dielectric resonator shows that the reaction force should be in the direction towards the end that has no  dielectric resonator.  That is, if the dielectric resonator is to the right of the center of mass of the drive, the reaction force will be to the left,  and if the drive is positioned such that the dielectric resonator is located to the left of the center of mass of the drive, the reaction force will be to the right.  This agrees with all your experimental results.

My analysis of the reaction force that results from the greater thermal expansion of the drive adjacent  to the dielectric resonator also shows that if the drive were perfectly symmetric (for example having the dielectric resonator centered at the center of mass, or having identical dielectric resonators located at the same distance from the center in both directions), there would be no net thermal distortion forces as they would balance themselves out.  In other words, if the Q-drive would have the dielectric resonator in the middle, or have two identical dielectric resonators positioned at equal distances from the center of mass, there would be no measurable forces.

Heat is generated inside the dielectric resonator due to the dielectric loss ("tan delta") material property of the resonator.  This internal heat power is produced instantly as a result of the electromagnetic field but it takes a finite amount of time for the temperature to diffuse through the material and reach steady state in accordance with Fourier's equation of heat conduction, depending on the diffusivity of the material, and satisfying  the thermal boundary conditions (convection and radiation if the experiment takes place in air, and just radiation if it takes place in a vacuum).  Since the dielectric loss factor ("tan delta") is temperature dependent, the heat generated is also temperature-dependent, which introduces a nonlinearity in the solution of the differential equations for this problem.  As the polymer ("Teflon" PTFE thermoplastic Fluoropolymer) dielectric temperature rises, it expands both in its radial and longitudinal direction.  There is also a dynamic effect due to the inertial forces reacting to the sudden pulse, in addition to the torsional resisting force of the torsional pendulum.

The thermal expansion of the polymer dielectric resonator in the radial direction results in better contact and heat transmission to the copper structure of the drive.  It can be readily shown that the effect of air convection in this experiment should be small in comparison with thermal conduction.

The reaction force produced by unsymmetric thermal expansion is proportional to the second derivative of temperature with respect to time. 

To calculate how long it takes for the temperature distribution to reach steady state (and therefore for the second derivative of temperature with respect to time to become negligibly small) we may use the Fourier Number: the thermal diffusivity times the characteristic time divided by the square of the characteristic length.  It is known that steady state is typically reached for a Fourier number exceeding unity, that is, for the characteristic time exceeding the ratio of the square of the characteristic length divided by the thermal diffusivity.  The thermal diffusivity of Teflon is 0.124 (mm^2)/sec.   I could not find the dimensions of the Teflon dielectric resonator in the report.  I calculate that the time to reach thermal steady state exceeds 22 minutes if the characteristic length of Teflon is 0.5 inch (12.7 mm).  If the characteristic length of Teflon is 0.2 inch (5 mm), the time to reach steady state will exceed approximately 4 minutes.  If the characteristic length of Teflon is 1 inch (25.4 mm), the time to reach steady state will exceed 1 hour and 27 minutes.  We know from the report that the microwave pulse was maintained for only 35 seconds during the testing (see Fig.12, p.9 in the report).  Therefore, we know that the microwave pulse was maintained for an amount of time much shorter than the amount of time necessary for the temperature distribution to reach steady state in the Teflon dielectric resonator.

When the microwave power is turned off (Fig.12, p.9 of the report shows this happening 35 sec after it was turned on), the heat generating power suddenly becomes zero, and hence the second derivative of the temperature with respect to time (responsible for the reaction force) becomes negative when the microwave power is turned off, resulting in a force in the opposite direction as to when the microwave power was on. 

Since copper's Young modulus is about 300 times stiffer than Teflon's, and assuming that the Teflon, particularly as it expands radially, is in frictional contact with the surrounding copper, it makes sense to assume that the expansion of the Teflon dielectric resonator is restrained by the much stiffer copper.  Under that assumption, we can calculate the differential thermal expansion of the copper surrounding the Teflon as the product of the coefficient of thermal expansion of copper (16.6*10^(−6) 1/degC) times the longitudinal length of the Teflon resonator, times the "delta T": the temperature difference between the copper surrounding the Teflon and the rest of the structure. 

If the longitudinal length of the Teflon resonator is 1 inch (25.4 mm), the delta T necessary to produce a differential thermal expansion of 4 micrometers is only 9.5 deg C (17 deg F).  So it is quite possible to produce the measured deflections with a delta T in temperature of a few deg C.  If the Teflon is unrestrained by the copper, the required  delta T is 8 times smaller (since the coefficient of thermal expansion of Teflon is 135* 10^(−6) 1/degC, eight times greater than the coefficient of thermal expansion of copper).

I hope that these considerations, convince you (as has been my experience in testing at MIT and in industrial R&D) that thermal transient effects are important and therefore that it merits strong consideration that the measured deflections and forces in your torsion pendulum experiments of the Q drives are the result of a shift in material location of the center of mass due to differential thermal expansion resulting from heating of the dielectric resonator which is positioned unsymmetrically, as explained above.

Best regards,

Dr. Jose' J. Rodal
jrodal@alum.mit.edu

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