Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2101797 times)

Offline phaseshift

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Ha, that table was from you - "Here is a comparison of reported measurements for EM Drives and for the latest report by Fearn, Zachar, Woodward & Wanser."
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline phaseshift

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I will rewrite the script so that it uses the design factor and frequency.  Currently it takes sD, bD, and length. It will be more useful to use frequency, bD, and length - calculating sD appropriately. 

I'm concerned that if the original dimensions of the Shawyer Demo device were done by eye - how is that the small plate was 3 centimeters off - that seems a huge discrepancy.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline aero

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I was one of a few people trying to guestimate the small diameter of Shawyer's Demo. Yes, it was done by eye, or using tools attempting to match the profile of the cavity, which was by eye. For the error in small diameter you should fine a corresponding error in height as the taper is easy to match and the big diameter is given. These estimates were made before we had looked into the design factor so that approach wasn't considered. Neither did we have a good handle on cut-off or guide frequency. Time marches on, and you have somewhat better information now.

I suggest you go with the design factor calculation and adjust the height accordingly using the taper and the large and small diameters to calculate height. That is, of course if the numbers you derive will fit within the cavity as illustrated by the photographs. That is a simple sanity check. Others may have different and better justified opinions.
« Last Edit: 05/20/2015 03:47 AM by aero »
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Offline phaseshift

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I was one of a few people trying to guestimate the small diameter of Shawyer's Demo. Yes, it was done by eye, or using tools attempting to match the profile of the cavity, which was by eye. For the error in small diameter you should fine a corresponding error in height as the taper is easy to match and the big diameter is given. These estimates were made before we had looked into the design factor so that approach wasn't considered. Neither did we have a good handle on cut-off or guide frequency. Time marches on, and you have somewhat better information now.

I suggest you go with the design factor calculation and adjust the height accordingly using the taper and the large and small diameters to calculate height. That is, of course if the numbers you derive will fit within the cavity as illustrated by the photographs. That is a simple sanity check. Others may have different and better justified opinions.

Agreed. That makes the most sense to me.  As this is a work in progress it can always change. :)
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline deltaMass

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Asymmetry 101.
Throw a ball in the +x direction, perfect reflection from the front wall to hit the rear wall and be absorbed.
Throw: -p to floor through feet
Bounce: +2p to front wall
Absorb: -p to rear wall
Sum of momenta = 0

Conclusion: asymmetry doesn't make floobie dust.

Offline RotoSequence

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Asymmetry 101.
Throw a ball in the +x direction, perfect reflection from the front wall to hit the rear wall and be absorbed.
Throw: -p to floor through feet
Bounce: +2p to front wall
Absorb: -p to rear wall
Sum of momenta = 0

Conclusion: asymmetry doesn't make floobie dust.

That's why much of the conversation in these threads has been dedicated to nonreciprocal behaviors. The outcomes get a little more complicated when you introduce (apparent) non-time-reversible mechanics.
« Last Edit: 05/20/2015 05:56 AM by RotoSequence »

Offline TheTraveller

This is a 3D model of the "Shawyer Demo".  I built it as close as I can figure that it has to be and examining the several photographs that have been shared here.  The dimensions are from published values.

rfFrequency=2.45*10^9;
cavityLength=0.345;
bigDiameter=0.28;
smallDiameter= 0.128853

power =  421 to 1200
Q = 45000

(measured force = 102.30 milliNewtons only reported for  421 watts, 243 milliNewtons/kW )

measured ForcePerPowerInput = 80 to 243
Force/PowerInput of a Photon Rocket =0.003337
measured ForcePerPowerInput to the one of a photon rocket =23,980 to 72,830

While this is a crude SketchUp model if anyone wants the model I'm happy to share it.

Nice job but the drawing looks like the Flight Thruster which ran at 3.85GHz.
http://www.emdrive.com/flightprogramme.html

Attached are photos of the Demonstrator. It is unknown if it had curved end caps.
http://emdrive.com/demonstratorengine.html
http://emdrive.com/dynamictests.html
« Last Edit: 05/20/2015 08:53 AM by TheTraveller »
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Offline TheTraveller

I'm working on a method to calculate end plate to end plate resonance from the external Rf wavelength, based on a continually variable internal guide wavelength between the 2 end plates. Have had advise this is the correct way to do it.

Once that is worked out, it becomes possible to determine end plate spacing, knowing applied Rf frequency & Df.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline snow

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can someone explain in normal people terms were is the recoil going from turning on the microwave?
shouldn't the metal box push on the microwave just as much as the microwave pushes on the metal box?

also, it gets really hot... could the recoil just be delayed?

Offline RotoSequence

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can someone explain in normal people terms were is the recoil going from turning on the microwave?
shouldn't the metal box push on the microwave just as much as the microwave pushes on the metal box?

also, it gets really hot... could the recoil just be delayed?

Classical mechanics and known physics both say that the energy should take the form of waste heat and extraneous electromagnetic energy (in other words, the EM drive shouldn't be doing anything of interest). At this point, assuming the recoil force is real, there is no definitively known mechanism of action.

Offline pogsquog

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can someone explain in normal people terms were is the recoil going from turning on the microwave?
shouldn't the metal box push on the microwave just as much as the microwave pushes on the metal box?

also, it gets really hot... could the recoil just be delayed?

Shawyer's explanation is that the waves bounce back and forth across the device.
The speed of the waves depends upon the shape of the container (the container is acting as a wave-guide, which reduces the propagation speed to be less than C). Shawyer asserts that the momentum change is thereby asymmetric, due to the differing effective impact speeds. Note that the wider physics community do not agree with this analysis, although I do not understand the details.
However, there are other theories, in particular Dr.White at NASA thinks that the EM fields from the standing waves are interacting with quantum 'virtual particles', effectively pushing off these. There are problems to do with special relativity and conservation of energy that would seem to make this unlikely unless you go and revive some very old theories of the aether and absolute reference frames, which are very marginal (special relativity has been well tested and aether theories abandoned as unproductive).
Another theory that allows breaking of local conservation of momentum and which _is consistent with observations  is Woodward 'Mach' effects. These relate to accelerating bodies which are changing in internal energy levels. The momentum is effectively transferred to all other bodies in the universe, at the speed of light. Attempts to produce or measure Mach effects have thus far failed, but there are reasonable theoretic reasons to believe they might be possible (they help to explain inertia and provide a preferred reference frame which special relativity lacks). I don't think anyone is explaining the EM drive in terms of this, however.

Offline OttO

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« Last Edit: 05/20/2015 11:12 AM by OttO »

Online Rodal

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I have recalculated the small diameter, for Shawyer's EXPERIMENTAL THRUSTER using Shawyer's paper http://www.emdrive.com/IAC-08-C4-4-7.pdf, see page 6, where Shawyer states

Quote from: Shawyer
A 160 mm diameter experimental thruster, operating at 2.45 GHz was designed and built. (see fig 6) The design factor, calculated from as-built measurements of the thruster geometry
was 0.497. An unloaded Q of 5,900 was measured. [/b].
(Unfortunately, Shawyer does not provide the small diameter or the cavity length in his paper)

I have used this information

bigDiameter = 0.16 m;
f = 2.45*10^9 Hz;
cst = 1.7062895542683174;
cM = 299705000 m/s (speed of light in air);
Design Factor = 0.497,

and inverted the equation for the Design Factor (see: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ) to obtain the following correct dimension:

small diameter = 0.1025 m SHAWYER's EXPERIMENTAL THRUSTER

(obtained from the Design Factor, bigDiameter and frequency provided by Shawyer)

I have updated the table in http://forum.nasaspaceflight.com/index.php?topic=36313.msg1302455#msg1302455 , originally dated 5 months ago, with his information.
« Last Edit: 05/20/2015 12:41 PM by Rodal »

Offline Star One

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can someone explain in normal people terms were is the recoil going from turning on the microwave?
shouldn't the metal box push on the microwave just as much as the microwave pushes on the metal box?

also, it gets really hot... could the recoil just be delayed?

Shawyer's explanation is that the waves bounce back and forth across the device.
The speed of the waves depends upon the shape of the container (the container is acting as a wave-guide, which reduces the propagation speed to be less than C). Shawyer asserts that the momentum change is thereby asymmetric, due to the differing effective impact speeds. Note that the wider physics community do not agree with this analysis, although I do not understand the details.
However, there are other theories, in particular Dr.White at NASA thinks that the EM fields from the standing waves are interacting with quantum 'virtual particles', effectively pushing off these. There are problems to do with special relativity and conservation of energy that would seem to make this unlikely unless you go and revive some very old theories of the aether and absolute reference frames, which are very marginal (special relativity has been well tested and aether theories abandoned as unproductive).
Another theory that allows breaking of local conservation of momentum and which _is consistent with observations  is Woodward 'Mach' effects. These relate to accelerating bodies which are changing in internal energy levels. The momentum is effectively transferred to all other bodies in the universe, at the speed of light. Attempts to produce or measure Mach effects have thus far failed, but there are reasonable theoretic reasons to believe they might be possible (they help to explain inertia and provide a preferred reference frame which special relativity lacks). I don't think anyone is explaining the EM drive in terms of this, however.

To your last point I though they were, I first came across this whole business on Talkpolywell & last I looked that was the explanation being moved forward there by some posters.

Offline TheTraveller


I have recalculated the small diameter, for Shawyer's EXPERIMENTAL THRUSTER using Shawyer's paper http://www.emdrive.com/IAC-08-C4-4-7.pdf, see page 6, where Shawyer states

Quote from: Shawyer
A 160 mm diameter experimental thruster, operating at 2.45 GHz was designed and built. (see fig 6) The design factor, calculated from as-built measurements of the thruster geometry
was 0.497. An unloaded Q of 5,900 was measured. [/b].
(Unfortunately, Shawyer does not provide the small diameter or the cavity length in his paper)

I have used this information

bigDiameter = 0.16 m;
f = 2.45*10^9 Hz;
cst = 1.7062895542683174;
cM = 299705000 m/s (speed of light in air);
Design Factor = 0.497,

and inverted the equation for the Design Factor (see: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ) to obtain the following correct dimension:

small diameter = 0.1025 m SHAWYER's EXPERIMENTAL THRUSTER

(obtained from the Design Factor, bigDiameter and frequency provided by Shawyer)

Nice idea. I got the same small end diameter using Excel goal seek, setting Df as goal and allowing small diameter to be varied until it hit the Df goal.
« Last Edit: 05/20/2015 11:54 AM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline StrongGR

As promised I am posting the latest draft about general relativity and electromagnetic field. The relevant conclusion is that there is thrust. Thanks to the comments by Jose Rodal, it can be shown that this can be meaningful and the best geometry is that of the frustum tending to a cone. There is no violation of conservation law due to the presence of the gravity that can escape the device producing a reaction.

I post it here for your comments that are very welcome as usual. You can find the final equation at page 12 for your evaluations. Later on, I will post a version with a somewhat different presentation to arxiv.

Online Rodal

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Ha, that table was from you - "Here is a comparison of reported measurements for EM Drives and for the latest report by Fearn, Zachar, Woodward & Wanser."

That table (http://forum.nasaspaceflight.com/index.php?topic=36313.msg1302455#msg1302455 ) was dated 12/14/2014, more than 5 months ago.

The table was the result of the best efforts of a team of people that have been in this thread from the beginning, working with this "EM Drive tar baby" where researchers report experimental measurements without giving the dimensions of the cavities used in the experiments .

Kudos to the people that did their best to guesstimate the dimensions of these cavities, which the researchers neglected to do in their reports.

Subsequent to that table, we owe thanks to Paul March of NASA Eagleworks for being the only researcher, worldwide, to have provided the dimensions of the cavity used in their reported experimental measurements.  I have updated the table with this information.

Shawyer has never provided all the dimensions for the cavities he used in his reported experiments (although he is in communication with people in this forum, and we have asked for these dimensions).

Shawyer only provided the large diameter for his Experimental and Demonstration thrusters.

As discussed in the last dozen pages of this thread, at the time (12/14/2014) that the table was reported we had interpreted Shawyer's Design Factor as including the cavity length.  We had interpreted Shawyer's Design Factor as modeling the truncated cone cavity as being a single continuous cavity (as it must be in our real world).  Thanks to the efforts of TheTraveller we learned that Shawyer has followed a very unorthodox procedure to derive his "DesignFactor" where he models the (real, continuous, single) truncated cone as being two (2) discontinuous, disjoint, cylindrical cavities, one having the big diameter and the other separate cavity having the small diameter. We have since then recomputed the Design Factor and have posted this interpretation of Shawyer's Design Factor (see: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ).  We have also updated the dimension of the small diameter calculated on the basis of this Design Factor.

Notice that while our original interpretation of Shawyer's Design Factor took into account all vital dimensions: the small diameter, the big diameter and the cavity length (from which the truncated cone angle can be obtained), the latest interpretation of Shawyer's Design Factor, completely ignores the cavity length.  This interpretation of the Design Factor, worked out with TheTraveller shows that Shawyer calculates the thrust force on an EM Drive to be completely independent of the cavity length: it doesn't make a difference whether the cavity has zero length or whether the cavity has a length of 50,000 light years from here to the nearest magnetar.  It doesn't make a difference whether the truncated cone has a cone angle approaching zero (like a cylinder) or the truncated cone has a cone angle of 45 degrees.  While such a Design Factor, and hence such a formula for thrust force, that completely ignores the cavity length does not make physical sense to me (*), we have reproduced it, because if that is the formula that Shawyer used (however questionable it may be), that is the formula we need to unlock the geometrical dimension of the small diameter that Shawyer has not directly, explicitly provided.  Please note that Shawyer has not provided the length of the cavity either, which is consistent with his formula that ignores the cavity length. Therefore, notice that Shawyer's cavity lengths are being estimated and so anyone using them is forewarned to use them at their own peril.

_____________
(*) Obviously, since Shawyer's thrust force formula ignores the cavity length (and hence ignores the cone angle) it must be an approximation for an undisclosed range of cavity lengths (or alternatively, an approximation for an undisclosed range of cone angles). Since the initial cone angles of the experiments by Shawyer (the Experimental. Demonstration and Flight Thruster) involved small cone angles, according to the published photographs, it is apparent that Shawyer's thrust formula, and hence his Design Factor must be based on a small cone angle approximation.
« Last Edit: 05/20/2015 12:51 PM by Rodal »

Offline TheTraveller

Notice that while our original interpretation of Shawyer's Design Factor took into account all vital dimensions: the small diameter, the big diameter and the cavity length (from which the truncated cone angle can be obtained), the latest interpretation of Shawyer's Design Factor, completely ignores the cavity length.  This interpretation of the Design Factor, worked out with TheTraveller shows that Shawyer calculates the thrust force on an EM Drive to be completely independent of the cavity length: it doesn't make a difference whether the cavity has zero length or whether the cavity has a length of 50,000 light years from here to the nearest magnetar.  It doesn't make a difference whether the truncated cone has a cone angle approaching zero (like a cylinder) or the truncated cone has a cone angle of 45 degrees.  While such a Design Factor, and hence such a formula for thrust force, that completely ignores the cavity length does not make physical sense to me, we have reproduced it, because if that is the formula that Shawyer used (however questionable it may be), that is the formula we need to unlock the geometrical dimension of the small diameter that Shawyer has not directly, explicitly provided.  Please note that Shawyer has not provided the length of the cavity either, which is consistent with his formula that ignores the cavity length. Therefore, notice that Shawyer's cavity lengths are being estimated and so anyone using them is forewarned to use them at their own peril.

It is not correct to state Shawyer ignores the length. He has stated many times that the applied Rf must cause frustum length resonance. Without this resonance there will be little thrust. Note he uses electrical length and not physical length. Spoilers? More bread crumbs for the trail?

I understand you focus on the equations but maybe spend some time reading his words as per the attached.

Has he described how to calc the physical end plate separation versus external Rf to obtain resonance? No he has not.

Is that a crime? No it is not.

SPR is in business to make money and giving away all their "Secret Squirrel Secret Sauce" may not be in their best interest.

If Shawyer does not fully disclose, that is his right and you have NO right to call him out for doing so.

« Last Edit: 05/20/2015 12:54 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Online Rodal

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...
It is not correct to state Shawyer ignores the length. He has stated many times that the applied Rf must cause frustum length resonance. Without this resonance there will be little thrust.

I understand you focus on the equations but maybe spend some time reading his words as per the attached.

Has he described how to calc the end plate separation versus external Rf to obtain resonance? No he has not.

Is that a crime? No it is not.

SPR is in business to make money and giving away all their "Secret Squirrel Secret Sauce" may not be in their best interest.

If Shawyer does not fully disclose, that is his right and you have NO right to call him out for doing so.
Sir @TheTraveller, I was answering @phaseshift: I referred exclusively to Shawyer's mathematical equations, and the fact that the geometrical dimensions of the experiments where not reported in his papers.  It is expected that the geometrical dimensions should be disclosed in experimental papers, and it is pro forma in peer-review to argue mathematical equations in papers.

Sir, this thread is not a thread to deal with personalities, and much less is a thread to sponsor the commercial interests of private, for profit businesses.

Please try to adopt an objective, and skeptical attitude in analyzing the EM Drive technical subject and try not to personalize it.
« Last Edit: 05/20/2015 01:00 PM by Rodal »

Offline TheTraveller

...
It is not correct to state Shawyer ignores the length. He has stated many times that the applied Rf must cause frustum length resonance. Without this resonance there will be little thrust.

I understand you focus on the equations but maybe spend some time reading his words as per the attached.

Has he described how to calc the end plate separation versus external Rf to obtain resonance? No he has not.

Is that a crime? No it is not.

SPR is in business to make money and giving away all their "Secret Squirrel Secret Sauce" may not be in their best interest.

If Shawyer does not fully disclose, that is his right and you have NO right to call him out for doing so.
Sir, I referred exclusively to Shawyer's mathematical equations, and the fact that the geometrical dimensions of the experiments where not reported in his papers.  It is expected that the geometrical dimensions should be disclosed in experimental papers, and it is pro forma in peer-review to argue mathematical equations in papers.

Sir, this thread is not a thread to deal with personalities, and much less is a thread to defend the business interests of personalities.

Please try to adopt an objective, and skeptical attitude in analyzing the EM Drive technical subject and try not to personalize it.

You made statements Shawyer ignores the length. That statement is not correct.

You made statements Shawyer has not fully disclosed data. That is his right.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

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