Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1803944 times)

Offline TheTraveller


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Not to fight his battles for him, but he is not obligated to answer that question on something like this and you should know better than to be even asking.
I strongly disagree.   TheTraveller started this by posting in this thread that Shawyer was going to publish an article in a peer-reviewed journal, and made a number of statements based on his privileged status of having the unique opportunity of having read the article ahead of publication.  Nobody asked or forced TheTraveller to post about Shawyer's future article.  Now TheTravellerEMD publishes the abstract of the paper.
WallofWolfStreet is entirely correct to ask TheTraveller about this abstract vis-a-vis TheTraveller's previous posts on this thread concerning the article he claims to have read ahead of publication.

As stated on page 1 of this thread, this thread is not a site for public advertising or promotions.

What was the purpose of TheTraveller's posting the fact that he had read Shawyer's upcoming article ?

I'm not the only active NSF member who has the paper.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline SeeShells

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EMDIYers Word O' the Day: Apophenia

"is the experience of perceiving patterns or connections in random or meaningless data." - https://en.wikipedia.org/wiki/Apophenia

Moral of the day? Get your test results up out of the noise to show clear trends.  8)
Yep and if  my 800 watts won't do it I might react like the Myth Busters and get a high power surplus klystron from ebay and run it till it slags.

Shell, you might be surprised about the resolution of the fulcrum test methodology. For example, I am tweaking mine for much higher resolution, increasing laser path length, oil dampening, stiffening, etc. Reason I did this is that the Q of my cavity may be much less than spreadsheet land...IOW, I'm planning for 1/10 the resolution I started out with @ 8W. So at 800W, you might launch that puppy  ;)
Thank's for your vote of confidence!

In some ways I'm still trying to get my head around it.

I have a 800 w magnetron putting out microwaves all up and down the spectrum ~2.45 Ghz
http://www.interferencetechnology.com/wp-content/uploads/2011/05/braun_fig6.gif

and a little dipole antenna that that will insert them into my cavity that I have designed a variable endplate geometry with a polygon shape.

How many modes will it run simultaneously at? Most of the models I see deal with one resonate mode frequency. Am I missing a duh moment here?

Time for a morning hot tub, cup of coffee and listen to the birds in the pines.

Shell

Offline aero

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@aero

I would be a lot interested in a run with two additional equal sources of microwaves OUTSIDE the frustum. One toward the big side and one toward the small side. All the other parameters the same as your previous runs.

If I am correct and if MEEP is able to simulate Wood anomalies (plasmons), we could end with one OUTSIDE end surface of the frustum less reflective than the other to microwaves.

http://cpb.iphy.ac.cn/EN/article/downloadArticleFile.do?attachType=PDF&id=26571

What do you think of that?

PS: If it is not a silly idea, and if the DIY lab is near a TV transmitter or an airport radar we could have funny results :P

 http://juluribk.com/tag/free-software/

Probably something for much later. Meep models don't move and nothing on the inside affects the outside unless gaps are modelled or the skin is very thin. But if the skin is that thin then there is general degradation of meaningful results.
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Offline VAXHeadroom

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     Yes, getting a test syystem to that location would be hidiously expensive, but if there are results that seem to be very promising, I don't really think we'll fully understand what is going on until gravity can be effectively eliminated as a factor.

A 10cm cube science device is $65K (IIRC) to the ISS from NanoRacks, and you can possibly get it flown by the NASA Flight Opportunities Office.  So 'hideously' is a bit of an overstatement :)
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Offline VAXHeadroom

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Yep and if  my 800 watts won't do it I might react like the Myth Busters and get a high power surplus klystron from ebay and run it till it slags.

"Anything worth doing is worth overdoing."  -- Adam Savage :)
Emory Stagmer
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Offline hhexo

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The EMDrive is a different breed of dog but has the same leg action.

Non powered EMDrive can move either direction.

Powered it resists movement in one direction but not the other due to differential internal Doppler shifts of the resonant standing wave inside the cavity.

I understand that. My description related to inertial mass is just another fancy way to model this behaviour.

My doubts are related to the fact that yes, the EmDrive does not resist its movement in one direction, but it does not make the whole spaceship not resist movement in that direction unless the effect is so great that it becomes equivalent to a lot of exotic negative mass.

Do you see what I mean? It will be easier to push the EmDrive in one direction, and in a limit, it will be so easy to push the EmDrive that it will seem so lighter that you would need almost zero force to do so. But what about the rest of the spaceship attached to the frustum? That is still hard to push. So you need to make the EmDrive "so easy to push that it does not just stop resisting, it encourages pushing", i.e. in my description the device has acquired apparent negative inertial mass greater in modulus than its own rest (unpowered) mass in one direction.

This makes me doubtful and sceptical, but I'm not inherently opposed to this, maybe we're just on the verge of finding something (I mean, just having a method of generating a tiny apparent negative mass would be an awesome discovery).

I just think for now that the effect will probably be smaller than what we dream of. But hey, if there is experimental data contradicting my doubts, I'll welcome it.

Offline SeeShells

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Thank you for detailing it out I very much appreciate it.

On models... it's true Jose and if we were better at our models we would have had a operational fusion reactor long ago. ;) But, they are good enough to give us CERN aren't they? We're not dealing with a particle accelerator cavity are we (or maybe we are)? It's just a copper capped off cone shaped enclosure, just a slight deviation from a symmetrical resonating cavity and it should as easy as ringing a bell, it's not. HA!... like striking a large bell and hearing Johann Strauss's "The Blue Danube" over the ringing and that would be a good analogy.

We should not conflate the claims about "thrust" from the EM Drive to whether we can accurately model the natural frequency and mode shapes.  Is this being conflated because of deltaMass question?

I think that deltaMass was addressing the thrust claims, and not the natural frequency or mode shape calculations.  I think that deltaMass was questioning whether numerical analysis of Maxwell's equations can throw any light on the claimed "thrust". 

_______

In regards to Q or natural frequencies of a cone or a hexagon shape of a given dimension we can come close to calculating those harmonics using Maxwell's equations but like I just wrote to @Rfmwguy those are just a slice of the total action that can be expected within the Frustum. And it leads heavy math papers like this one just posted. http://arxiv.org/pdf/1505.06917v1.pdf

Tub time, the effervescent waves are calling me.

Shell

Offline aero

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This is a good guide for installation of MEEP on Windows.
http://novelresearch.weebly.com/installing-meep-in-windows-8-via-cygwin.html

Thanks,
I run Linux on Ubuntu but it would be great if someone else or more people tried meep.
As for support, I haven't found much online support for the rather mundane problem of simulating a resonant cavity. Professional meep users are busy inventing improved optical tweezers or evanescent microscopes or some such.
Retired, working interesting problems

Offline WarpTech

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When you pull it forward, it's lighter. When you push it backwards, it's heavier. An external sin(wt) oscillation will have a NET DC offset. LOL! That's hilarious!

The engineer in me still doesn't see this cruising among the stars...

If I understand correctly, this is equivalent to saying that the inertial mass of the device appears different in different directions. We can visualize it with a surface which normally is a sphere of radius m0, but which is distorted when the resonant microwaves are on, to a surface that is still radially symmetrical around the z axis but asymmetrical with respect to the xy plane. The modulus of the points on the surface determines the effective inertial mass mv (with v being the vector to the point - for each interaction you have to take the vector that's aligned with the force).

Am I correct in saying that this theory then intentionally breaks the equivalence principle? That gravitation (like any other force) would use the standard mass m0 but inertia would use an mv on the distorted surface?
I'm not inherently opposed to it, I'm just checking, is this what the theory implies?

If this theory was correct, then:
- When the device is on a scale and powered on, it would weigh more or less depending on how it's oriented, because gravitational mass would be different from inertial mass. This would explain the static results on scales, which would not be the result of thrust, but only of a perceived mass difference.
- When the device is free to move and powered on, it would resist accelerations differently in different directions. Given a vibration pattern, there would be a net movement in one direction.
- The device would not be a thruster on its own, but only an inertial dampener/booster.

The energy required for this inertial dampening would come from the power supply; I would wager that for CoE the energy that you spend for the inertia change is at least equal (but likely higher) to what you would have spent propelling the reaction mass that you didn't need to propel. So it basically saves reaction mass but doesn't save energy, it just allows you to use electric energy directly without reaction mass.

Even if we roll with it though, the engineer in me says that it still does not make space propulsion much easier. As far as I can see the device can only change the inertial mass of the device itself, not of the ship around it. Even supposing we power it with an insane amount of energy and reduce the EmDrive inertial mass to zero in one direction... it doesn't reduce the total inertial mass of the spaceship by much.

Unless it can reduce its inertial mass to negative values, but that's even more exotic and definitely in the realm of spacetime warp.

It doesn't violate the equivalence principle at all. In fact, it takes advantage of it. Think of a piston and valve in water. You pull the piston forward when the valve is open, letting water pass through it. You push the piston  backwards and the valve closes, pushing the mass of water away and pushing you the other way.

In this case, the "water" is the energy stored inside at frequency "f" and energy "Q". When the frustum is pulled forward the mode moves to a lower frequency and lower energy, making the internal mass lighter. It gives up its energy as thrust, (applied energy - internal energy shift) When it is pushed backwards, it adds its energy as resistance, meaning as extra mass. (energy applied + internal energy shift) to cause resistance.

This is very important! Because this is the how it can work as a sealed cavity AND act as a thruster. What needs to be calculated using Maxwell's equations and @Rodal's solution, is how those modes and Q are affected when in an accelerated frame of reference. Maxwell's equations can certainly tell us the energy shift due to the Doppler shift and change in position inside the frustum. This difference between energy shift forward vs energy shift backwards gives us the Delta-Mass! i.e, we solved Woodward's dilemma of how to amplify the effect. :)
Todd


Offline rfmwguy

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EMDIYers Word O' the Day: Apophenia

"is the experience of perceiving patterns or connections in random or meaningless data." - https://en.wikipedia.org/wiki/Apophenia

Moral of the day? Get your test results up out of the noise to show clear trends.  8)
Yep and if  my 800 watts won't do it I might react like the Myth Busters and get a high power surplus klystron from ebay and run it till it slags.

Shell, you might be surprised about the resolution of the fulcrum test methodology. For example, I am tweaking mine for much higher resolution, increasing laser path length, oil dampening, stiffening, etc. Reason I did this is that the Q of my cavity may be much less than spreadsheet land...IOW, I'm planning for 1/10 the resolution I started out with @ 8W. So at 800W, you might launch that puppy  ;)
Thank's for your vote of confidence!

In some ways I'm still trying to get my head around it.

I have a 800 w magnetron putting out microwaves all up and down the spectrum ~2.45 Ghz
http://www.interferencetechnology.com/wp-content/uploads/2011/05/braun_fig6.gif

and a little dipole antenna that that will insert them into my cavity that I have designed a variable endplate geometry with a polygon shape.

How many modes will it run simultaneously at? Most of the models I see deal with one resonate mode frequency. Am I missing a duh moment here?

Time for a morning hot tub, cup of coffee and listen to the birds in the pines.

Shell

I've been thinking about the spectral impurity of a magnetron and could it work in the emdrive's favor. There seems to be a theory floating about that the frustum needs to undergo a "discharge" or reset state, therefore, a 60% duty cycle might help accomplish this. Who knows what the reset state duration is at this point...not enough test data.

Riddle me this, does the magnetron's natural frequency drift, pulse rate and spurious sidebands actually enable this reset? Maybe...maybe not. Yours will be pulsed at higher power, mine a CW with 100% duty cycle and low spurious (a requirement for WIFI gear). So...we're covering some boundaries here...CW, pulse, input power, frustum dimensions all at 2.45 GHz...should be interesting.

Offline Rodal

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Thank you for detailing it out I very much appreciate it.

On models... it's true Jose and if we were better at our models we would have had a operational fusion reactor long ago. ;) But, they are good enough to give us CERN aren't they? We're not dealing with a particle accelerator cavity are we (or maybe we are)? It's just a copper capped off cone shaped enclosure, just a slight deviation from a symmetrical resonating cavity and it should as easy as ringing a bell, it's not. HA!... like striking a large bell and hearing Johann Strauss's "The Blue Danube" over the ringing and that would be a good analogy.

We should not conflate the claims about "thrust" from the EM Drive to whether we can accurately model the natural frequency and mode shapes.  Is this being conflated because of deltaMass question?

I think that deltaMass was addressing the thrust claims, and not the natural frequency or mode shape calculations.  I think that deltaMass was questioning whether numerical analysis of Maxwell's equations can throw any light on the claimed "thrust". 

_______

In regards to Q or natural frequencies of a cone or a hexagon shape of a given dimension we can come close to calculating those harmonics using Maxwell's equations but like I just wrote to @Rfmwguy those are just a slice of the total action that can be expected within the Frustum. And it leads heavy math papers like this one just posted. http://arxiv.org/pdf/1505.06917v1.pdf

Tub time, the effervescent waves are calling me.

Shell
The natural frequency and the mode shape predictions based on Maxwell's equations is all that I was referring to in previous discussions regarding numerical modeling.  The natural frequency and mode shape calculations should not be conflated with whether there is thrust or no thrust.   Marco Frasca paper (quoted above) is entirely consistent with that assertion.   
« Last Edit: 06/25/2015 04:50 PM by Rodal »

Offline Rodal

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[...What needs to be calculated using Maxwell's equations and @Rodal's solution, is how those modes and Q are affected when in an accelerated frame of reference. Maxwell's equations can certainly tell us the energy shift due to the Doppler shift and change in position inside the frustum. This difference between energy shift forward vs energy shift backwards gives us the Delta-Mass! i.e, we solved Woodward's dilemma of how to amplify the effect. :)
Todd

Isn't that what Notsosureofit calculated ?  (an accelerated frame of reference...the energy shift due to the Doppler shift and change in position inside the frustum. )

http://emdrive.wiki/@notsosureofit_Hypothesis
« Last Edit: 06/25/2015 05:21 PM by Rodal »

Offline Star One

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Not to fight his battles for him, but he is not obligated to answer that question on something like this and you should know better than to be even asking.
I strongly disagree.   TheTraveller started this by posting in this thread that Shawyer was going to publish an article in a peer-reviewed journal, and made a number of statements based on his privileged status of having the unique opportunity of having read the article ahead of publication.  Nobody asked or forced TheTraveller to post about Shawyer's future article.  Now TheTravellerEMD publishes the abstract of the paper.
WallofWolfStreet is entirely correct to ask TheTraveller about this abstract vis-a-vis TheTraveller's previous posts on this thread concerning the article he claims to have read ahead of publication.

As stated on page 1 of this thread, this thread is not a site for public advertising or promotions.

What was the purpose of TheTraveller's posting the fact that he had read Shawyer's upcoming article ?

I'm not the only active NSF member who has the paper.

Interesting and I think that answers the matter for now.

Offline Dortex

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Powered it resists movement in one direction but not the other due to differential internal Doppler shifts of the resonant standing wave inside the cavity.

That doesn't make sense to me at all. I'm probably misunderstanding something here, but if the drive itself is our reference frame, it doesn't move at all. Meanwhile, if I, a car, or some passing bird were used as such, it moves quite easily without any resistance.

Offline Rodal

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I'm not the only active NSF member who has the paper.

Interesting and I think that answers the matter for now.
It certainly doesn't answer the question raised by WallofWolfStreet.  If anything it raises further questions.  What other NSF member has access to the paper and why is that relevant to this thread?

There is only one NSF member (to my knowledge) that disclosed his/her access to Shawyer's paper.

What is the purpose of posting (unasked by anyone) that she/he had privileged access to Shawyer's upcoming paper and boasting about its contents  "it will remove all doubt"  and now posting that another unnamed NSF member also has access?

Why give that irrelevant hearsay information (that somebody else has access to an unpublished paper) instead of providing substantive technical  information on what is the subject matter of the paper?

This is not a thread to disclose who has access to unpublished papers.  This is a thread to discuss the EM Drive developments - related to space flight applications -
« Last Edit: 06/25/2015 05:23 PM by Rodal »

Offline hhexo

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It doesn't violate the equivalence principle at all. In fact, it takes advantage of it. Think of a piston and valve in water. You pull the piston forward when the valve is open, letting water pass through it. You push the piston  backwards and the valve closes, pushing the mass of water away and pushing you the other way.
...
This is very important! Because this is the how it can work as a sealed cavity AND act as a thruster.
...
This difference between energy shift forward vs energy shift backwards gives us the Delta-Mass! i.e, we solved Woodward's dilemma of how to amplify the effect. :)
Todd

Ok, I see. The apparent Delta-Mass is already negative in one direction. That would be already awesome then. :)

I'm just doubtful of the following: can the Delta-Mass be so negative that it surpasses (in absolute value) the rest mass of the drive? Or any arbitrary amount of mass, for that matter. If you have a big ship attached to the drive, you need a very large negative Delta-Mass to have a visible effect.

Continuing your analogy, your piston in water will make a ship move, but of course the inertia of the rest of the ship matters. It will move significantly if it's a fishboat, and it will not move much if it's an aircraft carrier.

The Delta-Mass must be something like DeltaEnergyShift / c2. You need a LOT of stored energy to reduce the mass of a big ship!

I guess I'm just a bit of a pessimist. Only real experimental results will break my pessimism. :)

Offline WarpTech

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It doesn't violate the equivalence principle at all. In fact, it takes advantage of it. Think of a piston and valve in water. You pull the piston forward when the valve is open, letting water pass through it. You push the piston  backwards and the valve closes, pushing the mass of water away and pushing you the other way.
...
This is very important! Because this is the how it can work as a sealed cavity AND act as a thruster.
...
This difference between energy shift forward vs energy shift backwards gives us the Delta-Mass! i.e, we solved Woodward's dilemma of how to amplify the effect. :)
Todd

Ok, I see. The apparent Delta-Mass is already negative in one direction. That would be already awesome then. :)

I'm just doubtful of the following: can the Delta-Mass be so negative that it surpasses (in absolute value) the rest mass of the drive? Or any arbitrary amount of mass, for that matter. If you have a big ship attached to the drive, you need a very large negative Delta-Mass to have a visible effect.

Continuing your analogy, your piston in water will make a ship move, but of course the inertia of the rest of the ship matters. It will move significantly if it's a fishboat, and it will not move much if it's an aircraft carrier.

The Delta-Mass must be something like DeltaEnergyShift / c2. You need a LOT of stored energy to reduce the mass of a big ship!

I guess I'm just a bit of a pessimist. Only real experimental results will break my pessimism. :)

The only differential is between frequency f1 when it's pushed forward and frequency f2 when it's pushed backwards. It can never give up more mass than that energy, Delta_E/c^2. But at high Q, that energy can be quite large.

I need to go back and look at @Notsosureofit's theory again. Now that might make more sense to me too.
Todd


Offline cej

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In this case, the "water" is the energy stored inside at frequency "f" and energy "Q". When the frustum is pulled forward the mode moves to a lower frequency and lower energy, making the internal mass lighter. It gives up its energy as thrust, (applied energy - internal energy shift) When it is pushed backwards, it adds its energy as resistance, meaning as extra mass. (energy applied + internal energy shift) to cause resistance.

This is very important! Because this is the how it can work as a sealed cavity AND act as a thruster. What needs to be calculated using Maxwell's equations and @Rodal's solution, is how those modes and Q are affected when in an accelerated frame of reference. Maxwell's equations can certainly tell us the energy shift due to the Doppler shift and change in position inside the frustum. This difference between energy shift forward vs energy shift backwards gives us the Delta-Mass! i.e, we solved Woodward's dilemma of how to amplify the effect. :)
Todd

Is the following another way to explain it?

Looking at the TE mode for a cylindrical cavity (https://en.wikipedia.org/wiki/Microwave_cavity), the frequency is (roughly) inversely proportional to the radius of the cavity. Decreasing the radius will increase the frequency, which in turn increases the momentum of light in the cavity. To satisfy conservation of momentum, the cavity has to push back against decreasing the radius. In the other direction, increasing the radius will lower the frequency and momentum of light stored in the cavity. To satisfy conservation of momentum, the lost momentum goes towards encouraging the radius to increase. If the radius is fixed, then the momentum inside the cavity will remain constant.

By having light resonate in a frustum, the change of radius is tied to acceleration along the axis of the frustum. The frustum will thus encourage pushing against its large end (increasing the cavity's radius) and resist pushing its small end (decreasing the cavity's radius). If the frustum does not accelerate along its axis, the radius will not change and no force will be observed.



Offline Rodal

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In this case, the "water" is the energy stored inside at frequency "f" and energy "Q". When the frustum is pulled forward the mode moves to a lower frequency and lower energy, making the internal mass lighter. It gives up its energy as thrust, (applied energy - internal energy shift) When it is pushed backwards, it adds its energy as resistance, meaning as extra mass. (energy applied + internal energy shift) to cause resistance.

This is very important! Because this is the how it can work as a sealed cavity AND act as a thruster. What needs to be calculated using Maxwell's equations and @Rodal's solution, is how those modes and Q are affected when in an accelerated frame of reference. Maxwell's equations can certainly tell us the energy shift due to the Doppler shift and change in position inside the frustum. This difference between energy shift forward vs energy shift backwards gives us the Delta-Mass! i.e, we solved Woodward's dilemma of how to amplify the effect. :)
Todd

Is the following another way to explain it?

Looking at the TE mode for a cylindrical cavity (https://en.wikipedia.org/wiki/Microwave_cavity), the frequency is (roughly) inversely proportional to the radius of the cavity. Decreasing the radius will increase the frequency, which in turn increases the momentum of light in the cavity. To satisfy conservation of momentum, the cavity has to push back against decreasing the radius. In the other direction, increasing the radius will lower the frequency and momentum of light stored in the cavity. To satisfy conservation of momentum, the lost momentum goes towards encouraging the radius to increase. If the radius is fixed, then the momentum inside the cavity will remain constant.

By having light resonate in a frustum, the change of radius is tied to acceleration along the axis of the frustum. The frustum will thus encourage pushing against its large end (increasing the cavity's radius) and resist pushing its small end (decreasing the cavity's radius). If the frustum does not accelerate along its axis, the radius will not change and no force will be observed.

Here is Notsosureofit's analysis:

http://emdrive.wiki/@notsosureofit_Hypothesis

Offline Rodal

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I'm not the only active NSF member who has the paper.

Interesting and I think that answers the matter for now.
It certainly doesn't answer the question raised by WallofWolfStreet.  If anything it raises further questions.  What other NSF member has access to the paper and why is that relevant to this thread?

There is only one NSF member (to my knowledge) that disclosed his/her access to Shawyer's paper.

What is the purpose of posting (unasked by anyone) that she/he had privileged access to Shawyer's upcoming paper and boasting about its contents  "it will remove all doubt"  and now posting that another unnamed NSF member also has access?

Why give that irrelevant hearsay information (that somebody else has access to an unpublished paper) instead of providing substantive technical  information on what is the subject matter of the paper?

This is not a thread to disclose who has access to unpublished papers.  This is a thread to discuss the EM Drive developments - related to space flight applications -

For some substantive discussion (instead of this nonsense about "I'm not the only active NSF member who has the paper", this is the 2013 paper on Shawyer's superconducting thruster that the abstract of the new paper [that was claimed to "remove all doubts"] discusses:

http://www.emdrive.com/IAC13paper17254.v2.pdf

IAC-13,C4,P,44.p1,x17254
THE DYNAMIC OPERATON OF A HIGH Q EMDRIVE MICROWAVE THRUSTER
Roger Shawyer C.Eng. MIET. FRAeS
SPR Ltd UK sprltd@emdrive.com

Notice the emphasis on "designed" and "modelled" and the lack of discussion on experiments and experimental details.

Quote from: Shawyer
Superconducting second generation thrusters were
then modelled, cooled first with liquid nitrogen and
then with liquid hydrogen. The thruster designs
were based on the results obtained from the
experimental YBCO thin film thruster described in
REF 3. With the thruster cooled to 77deg K using
liquid nitrogen, a Q of 6.8x106 was measured.
Fig 3 shows the model results with the modified 2G
thruster cooled with liquid nitrogen, giving a static
specific thrust of 16.5 N/kW for an unloaded Q
factor of 3.7x106
. With this modest value of Q it
requires high acceleration to cause significant
reduction of specific thrust. In this case an
acceleration of 1000m/s/s ((100g) gives a specific
thrust reduced to 4 N/kW.

Fig 4 gives the results for a lower frequency cavity,
cooled by liquid Hydrogen, thus operating at a
temperature of 20deg K, and achieving a static
specific thrust of 173 N/kW, with an unloaded Q
factor of 3.9x107
. For an uncompensated thruster,
the loss of Q, and hence reduction of specific thrust
with acceleration is more pronounced. The model
results show a specific thrust of 11 N/kW for an
acceleration of 20m/s/s (2g).
A compensated cavity was designed and modelled,
where the axial length of the cavity is modified
according to the acceleration experienced by the
thruster. The cavity extension for a positive
acceleration of 20 m/s/s is illustrated in Fig 5. The
extension results from a pulsed voltage being
applied to piezoelectric elements in the sidewall of
the cavity. The pulse length is determined by the
time constant of the resonant cavity. A description
of such a thruster design is given in REF 4.
Clearly this simple form of compensation cannot
completely compensate for the Doppler shift
throughout a full pulse cycle, but fig 4 shows that
the specific thrust at 20m/s/s can be improved to 92
N/kW.

Quote from: Shawyer
A large high power thruster was designed,
operating at 900 MHz. This thruster again used a
YBCO superconducting coating, and was cooled
with liquid Hydrogen. The compensation technique
included both cavity length extension and
frequency offset, with a lower duty cycle than the
3.85 GHz thruster. A specific thrust of 9.92 kN/kW
was predicted with an acceleration limit of
0.5m/s/s.
This L-Band thruster was part of a design study for
a radically new approach to launch vehicles. A
Hybrid Spaceplane was proposed, using 2G LBand
EmDrive thrusters as lift engines, with
conventional low thrust jet engines and rocket
engines for auxilary propulsion. These secondary
propulsion units are fuelled by the gaseous
Hydrogen, boiled off during the cooling of the
EmDrive thrusters. The fuel cells used to provide
DC power to the microwave power sources would
also be fuelled in the same way. The initial
spaceplane design was described in REF 5.
« Last Edit: 06/25/2015 05:43 PM by Rodal »

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