Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2165600 times)

Offline rfmwguy

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From the thermal and A/m plots from EW, most of the resonance is happening at the big end. I would not put the magnetron in that space because the input there will probably perturb the waves. Shawyer put the input near the small end. I would put it "at" the small end, depending on wave polarization. The walls should do most of the reflecting, not the small end.

Todd D.

Please take a gander at this Demo Drive by Shawyer: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=829850

It seems to have the feed near the big diameter end.

Good call doctor. I find the stub coupler/feed at the larger diameter of the cavity interesting...thinking this was  the end with the highest return loss/standing wave at 2.4 GHz...perhaps not.

The stepper motor appears to be adjusting the length of a tuning stub centered in the cavity on the narrow end, probably something like this: http://i.stack.imgur.com/Vfdxq.png Its and old tried and true methodology.

Regardless, this tuning stub is simply a matching element which can be fixed (non-adjustable) once a center frequency is set and a tuning stub length measurement can be made. Normally, this tuning stub is adjusted for best S parameter match/bandwidth: http://www.antenna-theory.com/definitions/sparameters.php

Offline Rodal

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From the thermal and A/m plots from EW, most of the resonance is happening at the big end. I would not put the magnetron in that space because the input there will probably perturb the waves. Shawyer put the input near the small end. I would put it "at" the small end, depending on wave polarization. The walls should do most of the reflecting, not the small end.

Todd D.

Please take a gander at this Demo Drive by Shawyer: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=829850

It seems to have the feed near the big diameter end.

Good call doctor. I find the stub coupler/feed at the larger diameter of the cavity interesting...thinking this was  the end with the highest return loss/standing wave at 2.4 GHz...perhaps not.

The stepper motor appears to be adjusting the length of a tuning stub centered in the cavity on the narrow end, probably something like this: http://i.stack.imgur.com/Vfdxq.png Its and old tried and true methodology.

Regardless, this tuning stub is simply a matching element which can be fixed (non-adjustable) once a center frequency is set and a tuning stub length measurement can be made. Normally, this tuning stub is adjusted for best S parameter match/bandwidth: http://www.antenna-theory.com/definitions/sparameters.php

Thank you.  I agree with you   :)

Offline Rodal

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...
...

Todd and Notsosureofit:

I found a textbook that is in Google Books that has some formulas (including calculating the Q) for (slabs and also for coaxial) dielectric inserts in a cylindrical cavity.  See this:

The Google URL is huge, I hope this URL shortener works:

start at page 111 on this link  http://bit.ly/1FiKoz6


Propagation, Scattering and Dissipation of Electromagnetic Waves
 By A. S. Ilʹinskiĭ, A. Ya Slepyan

Series: IEEE Electromagnetic Waves Series (Book 36)
Publisher: The Institution of Engineering and Technology; First Edition edition (December 2, 1993)
ISBN-10: 0863412831
ISBN-13: 978-0863412837

Hopefully this can help you further in analyzing the thrust of a cylindrical EM Drive with a dielectric insert  :)

« Last Edit: 05/12/2015 08:09 PM by Rodal »

Offline deltaMass

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Back a ways there existed in woo land something called a "Slepian Drive". Same guy?
https://groups.yahoo.com/neo/groups/Stardrive1/conversations/topics/3910
« Last Edit: 05/12/2015 08:18 PM by deltaMass »

Offline rfmwguy

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Back a ways there existed in woo land something called a "Slepian Drive". Same guy?
https://groups.yahoo.com/neo/groups/Stardrive1/conversations/topics/3910

Nice absrtact...bottom line:

"We conclude that a new breed of propulsion scientists is required as they will need to be cross disciplined into a variety of the physical sciences to include: electromagnetism, spacetime and string-brane theory to but name only a few."

Offline Cinder

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That page requires Yahoo login.
The pork must flow.

Offline rfmwguy

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Offline WarpTech

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From the thermal and A/m plots from EW, most of the resonance is happening at the big end. I would not put the magnetron in that space because the input there will probably perturb the waves. Shawyer put the input near the small end. I would put it "at" the small end, depending on wave polarization. The walls should do most of the reflecting, not the small end.

Todd D.

Please take a gander at this Demo Drive by Shawyer: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=829850

It seems to have the feed near the big diameter end.

Good call doctor. I find the stub coupler/feed at the larger diameter of the cavity interesting...thinking this was  the end with the highest return loss/standing wave at 2.4 GHz...perhaps not.

The stepper motor appears to be adjusting the length of a tuning stub centered in the cavity on the narrow end, probably something like this: http://i.stack.imgur.com/Vfdxq.png Its and old tried and true methodology.

Regardless, this tuning stub is simply a matching element which can be fixed (non-adjustable) once a center frequency is set and a tuning stub length measurement can be made. Normally, this tuning stub is adjusted for best S parameter match/bandwidth: http://www.antenna-theory.com/definitions/sparameters.php

Thank you.  I agree with you   :)

If that stub extends inside the frustum, that would explain why he put the input at the big end. I still say, it should be at the small end to avoid perturbing the harmonics.

Todd

Offline deltaMass

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There's still the issue of drifting off tune with temperature

Offline Mulletron

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Early on in this thread, there was a lot of discussion of potential spaceflight applications which could be enabled by emdrives if the tech were to be viable. Here is an opportunity to roll some of that discussion into the design of the "challenge criteria" for an XPRIZE.

http://forum.nasaspaceflight.com/index.php?topic=37563.0

http://www.xprize.org/about/what-is-an-xprize
« Last Edit: 05/12/2015 09:21 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline deltaMass

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Early on in this thread, there was a lot of discussion of potential spaceflight applications which could be enabled by emdrives if the tech were to be viable. Here is an opportunity to roll some of that discussion into the design of the "challenge criteria" for an XPRIZE.

http://forum.nasaspaceflight.com/index.php?topic=37563.0

http://www.xprize.org/about/what-is-an-xprize
I don't think you can begin to design any sort of mission until you know the equation of motion in free space.

Offline LasJayhawk

There's still the issue of drifting off tune with temperature

I think Harold's lapsed patent on a resolver tuned vco could be adapted to keep the oscillator tuned to the cavity instead of the obverse.

https://www.google.com/patents/US4636747?dq=harold+selim&hl=en&sa=X&ei=oWxSVb6lHZGsogS5voHYAQ&ved=0CCoQ6AEwAg

Offline TheTraveller

From the thermal and A/m plots from EW, most of the resonance is happening at the big end. I would not put the magnetron in that space because the input there will probably perturb the waves. Shawyer put the input near the small end. I would put it "at" the small end, depending on wave polarization. The walls should do most of the reflecting, not the small end.

Todd D.

Please take a gander at this Demo Drive by Shawyer: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=829850

It seems to have the feed near the big diameter end.
The EM Drive Demonstrator was feed via a waveguide from a magnetron Rf source, not via coax. You can see the magnetron & waveguide in these 2 shots. Assume that connector is for feedback sense.
« Last Edit: 05/12/2015 09:30 PM by TheTraveller »
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Offline zen-in

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QUESTION 1: What is responsible for the huge time delay in Shaywer's force signal traces?  For NASA Eagleworks this delay represents about ~4*10^9 electromagnetic wave cycles.  For Shawyer this represents ~33*10^9 cycles. 

Clearly, this huge number of cycles has nothing to do with the Quantum Vacuum, or the speed of light, or the time required for a resonant cavity to reach steady state in standing waves. 
Is this time delay (20 sec) due to a time delay associated with a Q-multiplier effect ?
Is the time delay mainly due to the phase shift settling with time ? (due to Shawyer working with a Q multiplier setup having a Q=X times multiplier with feedback, having a phase shift narrow in frequency).  (hat tip to @Notsosureofit for the explanatory hint, any misinterpretation of which is mine).



QUESTION 2: What is responsible for the time delay in Shaywer's force signal traces after the power is turned off? 



Note: quotes used to call attention to this message in case they have quotes linked to e-mail message forum notifications.

Reference:  http://www.emdrive.com/IAC-08-C4-4-7.pdf
(Ques 1):
The initial delay has been blamed on the "tune-up" of the cavity.   There are claimed to be stepper motors for adjusting the interior dimensions of the cavity.   As these get adjusted and the Q increases the thrust increases.   That's what has been quoted in this forum by others; from one of Shawyer's papers.

(Ques 2):
There is no explanation based on Shawyer's theory for the thrust to continue after the RF drive has been switched off.   For that to occur the cavity has to store energy and release it as kinetic energy.   An inductor stores electrical energy and will release that electrical energy when the (DC) current flow is stopped.   But there is no equivalent electrical effect that would explain why Shawyer's cavity stores RF energy and then releases it as kinetic energy, in spite of it's high Q.   Or why there is a time delay.   A likely explanation is the slosh of coolant.   No doubt the coolant pump generates a measurable torque.    His apparatus is susceptable to spurious torque.   Any rotating machinery (motor, pump, etc)  mounted on a turntable with it's rotational axis parallel to the turntable's will start the turntable moving when it is turned on.    Even if the pump motor is mounted at right angles to the bearing axis the fluid mass flow could still cause rotation.  When the rotating machinery is switched off the fluid mass flow stops and the rotation of the turntable will stop.   That is just the conservation of angular momentum.    Maybe Shawyer has factored this error torque from the coolant pump into his graphs.
« Last Edit: 05/12/2015 09:33 PM by zen-in »

Offline TheTraveller

There's still the issue of drifting off tune with temperature
Is why the Rf frequency is adjusted via a feedback loop as used in the Flight Thruster.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline Mulletron

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Early on in this thread, there was a lot of discussion of potential spaceflight applications which could be enabled by emdrives if the tech were to be viable. Here is an opportunity to roll some of that discussion into the design of the "challenge criteria" for an XPRIZE.

http://forum.nasaspaceflight.com/index.php?topic=37563.0

http://www.xprize.org/about/what-is-an-xprize
I don't think you can begin to design any sort of mission until you know the equation of motion in free space.

Well before we start designing missions, we could design some simple performance objectives first. A good place to start? Prove these thrusters work as advertised.
« Last Edit: 05/12/2015 09:33 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline WarpTech

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There's still the issue of drifting off tune with temperature

... and acceleration. That is why I believe now that it should be pulsed, not steady state operation.

Todd

Offline Rodal

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From the thermal and A/m plots from EW, most of the resonance is happening at the big end. I would not put the magnetron in that space because the input there will probably perturb the waves. Shawyer put the input near the small end. I would put it "at" the small end, depending on wave polarization. The walls should do most of the reflecting, not the small end.

Todd D.

Please take a gander at this Demo Drive by Shawyer: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=829850

It seems to have the feed near the big diameter end.

Good call doctor. I find the stub coupler/feed at the larger diameter of the cavity interesting...thinking this was  the end with the highest return loss/standing wave at 2.4 GHz...perhaps not.

The stepper motor appears to be adjusting the length of a tuning stub centered in the cavity on the narrow end, probably something like this: http://i.stack.imgur.com/Vfdxq.png Its and old tried and true methodology.

Regardless, this tuning stub is simply a matching element which can be fixed (non-adjustable) once a center frequency is set and a tuning stub length measurement can be made. Normally, this tuning stub is adjusted for best S parameter match/bandwidth: http://www.antenna-theory.com/definitions/sparameters.php

Thank you.  I agree with you   :)

If that stub extends inside the frustum, that would explain why he put the input at the big end. I still say, it should be at the small end to avoid perturbing the harmonics.

Todd

Somebody else pointed out that Shawyer's Demonstrator was feed via a waveguide instead of via coax.  Does that make any difference to your point that feeding should preferentially occur (if possible) at the small end to avoid perturbing harmonics? In other words do you think that feeding with a waveguide avoids perturbing harmonics and therefore if one feeds with a waveguide (fed upstream from a magnetron) you could just as well feed the waveguide at the big end ?
« Last Edit: 05/12/2015 09:45 PM by Rodal »

Offline Rodal

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There's still the issue of drifting off tune with temperature

... and acceleration. That is why I believe now that it should be pulsed, not steady state operation.

Todd
That also makes sense to me. 

Separately, but interestingly the Serrano Field Effect Boeing Darpa device tested by Dr. White displayed the highest thrust/InputPower of any device, yet it only showed very short time impulses (like Dirac Delta Functions) instead of steady state operation (although to me its principle of operation is very different from the EM Drive, Dr. White classified this device also as a Q-thuster).

This is the text for Boeing/DARPA in slide 40 of Dr. White's presentation (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140000851.pdf ):

<<SFE Test Article at JSC

In 2013, Boeing/DARPA sent Eagleworks Lab an SFE test article for testing and evaluation

Evaluation of the test article in and out of a Faraday Shield performed from Feb through June 2013.

There is a consistent transient thrust at device turn-on and turn-off that is consistent with Qthruster physics
The magnitude of the thrust scaled approximately with the cube of the input voltage (20-110uN).
The magnitude of the thrust is dependent on the AC content of the turn-on and turn-off pulse
Specific force of transient thrust was in the ~1- 20 N/kW range.

~20-110 uN Thrust Pulses
Specific Force ~1-20N/kW>>

NASA Eagleworks also provided this information in a 2013 Newsletter, which is available in the Internet from this link:  https://xa.yimg.com/kq/groups/86787010/513081407/name/Eagleworks+Newsletter+2013.pdf

that reads:

<<NASA/Boeing/SFE Campaign: Boeing/DARPA sent Eagleworks Lab an SFE test article for testing and
evaluation. The guest thruster was evaluated in numerous test configurations using varying degrees of
Faraday shielding and vacuum conditions. Observations show that there is a consistent transient thrust
at device turn-on and turn-off that is consistent with Q-thruster physics. The magnitude of the thrust
scaled approximately with the cube of the input voltage (20-110uN). The magnitude of the thrust is
dependent on the AC content of the turn-on and turn-off pulse. Thrust to power of transient thrust was
in the ~1-20 N/kW range


Yes, that's twenty Newtons per kiloWatt on the upper range

Notice that the SFE Boeing Darpa Thrust/InputPower is 50 times greater than Shawyer's Flight Thruster shown on the slide to the right of it
« Last Edit: 05/12/2015 10:04 PM by Rodal »

Offline PaulF

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There's still the issue of drifting off tune with temperature

... and acceleration. That is why I believe now that it should be pulsed, not steady state operation.

Todd
That also makes sense to me. 

Separately, but interestingly the Serrano field effect device tested by Dr. White displayed the highest thrust/InputPower of any device, yet it only showed very short time impulses (like Dirac Delta Functions) instead of steady state operation (although to me its principle of operation is very different from the EM Drive, Dr. White classified this device also as a Q-thuster).
Forgive me for interrupting, but with pulsing, do you mean Pulse Width Modulation or PWM?

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