Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1873274 times)

Offline WarpTech

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I should know better than to post a 1st draft of anything, but here goes nothing...

What I've done is put together all of the pieces we have been working on, between Egan, Yang, De Aquino and Shawyer. What I ended up with didn't surprise me. What did is how much this "mimics" gravity  in the PV Model is not even funny!

Let the show begin!

Todd

Offline TheTraveller

EM Drive design spreadsheet attached:

Input big & small diameters, end plate spacing and desired frequency.
Select BesselJ cutoff mode. If not using TE01 or TM01 get value from BesselJ tab
Observe calculated end plate spacing in B35 thru B37
If using Txxx1 use B37 as end plate spacing
If using Txxx2 use B36 as end plate spacing
If using Txxx3 use B35 as end plate spacing.
Input cavity Q (K33) and power (K34), Thrust displayed in L33.

For the case of the Flight Thruster dimensions as per the spreadsheet (Light Green), Df is the same and resonance if VERY close to SRP supplied data.

Additional BesselJ cutoff tables are supplied for almost every cutoff mode possible on the BesselJ tab.

This is only part of the data needed to build a EM Drive. You also need:

1) Feed point location (sidewall or end plate) for desired Tx mode.

2) Antenna design and location inside the frustum.

3) Frustum impedance matching to the Rf generator impedance.

4) Ability to track resonant frequency change as the frustum heats up and expands.

Spreadsheet end plate spacing is calculated as 0.6mm wider than SPR data. Here I assume they have some additional factor, maybe due to wall skin effect or another such affect that may slightly alter effective guide wavelength. Anyway the spreadsheet data is more than close enough to build hardware from.
« Last Edit: 05/31/2015 06:38 AM by TheTraveller »
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Offline deltaMass

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Don't understand this end plate spacing protocol. First you say it's a user input. Then the user chooses a mode (say TE01) and then is supposed to "use" a specific value of end plate spacing. So which is it? manual input or autocalculated?
« Last Edit: 05/31/2015 06:44 AM by deltaMass »

Offline TheTraveller

Don't understand this end plate spacing protocol. First you say it's a user input. Then the user chooses a mode (say TE01) and then is supposed to "use" a specific value of end plate spacing. So which is it? manual input or autocalculated?

End plate spacing is calculated depending on number of 1/2 waves as per instructions. Manual input value is just for reference if you are inputting what you think are cavity dimensions.

If you wish, you can use Goal Seek to find an input frequency that will match a desired end plate spacing.

Or you can set the frequency and the calculator will determine the end plate spacing.
« Last Edit: 05/31/2015 07:01 AM by TheTraveller »
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Offline deltaMass

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I think you could automate that, but no matter. If I give Solver the two diameters and a rough endplate spacing, and a frequency, then given fixed P,Q, I need max Df in order to get max thrust. Have you tried that?

In other words, find Df|max = f(Dbig, Dsmall, f, L)

All we care about is maximising the thrust.
« Last Edit: 05/31/2015 07:04 AM by deltaMass »

Offline TheTraveller

I think you could automate that, but no matter. If I give Solver the two diameters and a rough endplate spacing, and a frequency, then given fixed P,Q, I need max Df in order to get max thrust. Have you tried that?

In other words, find Df|max = f(Dbig, Dsmall, f, L)

All we care about is maximising the thrust.

My goal is to Replicate the Flight Thruster, with as minimal changes as possible. I'm pleased my calcs match SPRs.

Once I learn how to impedance match and track resonate frequency changes in a frustum, with a Q of 50,000 to 60,000, as the frustum heats up, then I'll go for alerted dimensions to get higher thrust. But until then there are way too many operational issues that have yet to be overcome to start altering dimensions that I know work.

My 100W should give me around 20mN or 2gf of thrust. Initially I'll be very happy with that as it will be 100x more thrust than EW got with their dielectrics.
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Offline deltaMass

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Yup, makes sense. Was simply trying to understand how the 'sheet works.

Offline georgeh

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Thanks @TheTraveller for sharing your spreadsheet. I've uploaded it to Google Drive so that people without Microsoft Excel can tweak it and offer improvements.

https://docs.google.com/spreadsheets/d/1MyR1I2TzlOBXV7xnsxw32UGm7-JxbDIkNViC5F09rGU/edit#gid=1647834149

Offline Notsosureofit

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@RODAL

Yes, that's entirely correct.

I should add at eq 2 a note that p drops out for delta(f) as p=0 modes are dispersion-less in this approximation.
« Last Edit: 05/31/2015 01:53 PM by Notsosureofit »

Offline Rodal

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Oh Baby, here is a test stand floating on air, ready for baby EM drive   :)
...

Is this "baby" EM Drive supposed to have lower thrust according to any of the theories? Or is thrust completely based on resonance?

Some theories have thrust inversely proportional to frequency (hence this one at 24 GHz should have ~10 times less thrust than the ones at 2.4 GHz so far tested, based on inverse of linear proportionality alone)

McCulloch's formula  F = PQl/c * (1/w_small - 1/w_big) where l is the cavity length is independent of frequency.  But it is still proportional to power input.

Most theories have thrust proportional to PowerInput  This just has a little battery, so also have to factor out less thrust due to the lower Power Input

So, yes, substantially less thrust, according to those theories.

Higher frequency also means more geometrical attenuation, perhaps that's good, if it also has higher Q to go with it

And you can put a lot of these ones together, and it looks much neater and Hi-Tech  :)

If it works, it can go right away into a CubeSat

Notsosureofit's expression is also independent of frequency when the diameter and the length of the cavity are both scaled to decrease inversely proportional to increasing frequency, in order to maintain the same mode shape.

When the frequency increases by a factor of 10 (24 GHz = 10 * 2.4 GHz), then the diameter needs to be decreased by a factor of 10 and the length needs to be decreased by a factor of 10, in order to keep the same mode shape and thrust, as per Notsosureofit's formula.

When the diameter and the length of the cavity are both scaled  to decrease inversely proportional to increasing frequency, McCulloch's thrust expression also stays invariant.

So, Baby EM Drive by the guy in Aachen, Germany, at 24 GHz will be an extremely interesting test to find out whether McCulloch's and Notsosureofit equations are correct.

IMHO this Baby EM Drive test is the most interesting EM Drive test !!!

The ammonia molecule readily undergoes nitrogen inversion at room temperature. The resonance frequency is 23.79 GHz, corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed.  Ammonia has been used for Masers at 24 GHz for these reasons.

When using ammonia, safety precautions should be followed:
https://www.health.ny.gov/environmental/emergency/chemical_terrorism/ammonia_tech.htm

« Last Edit: 05/31/2015 03:30 PM by Rodal »

Offline TheTraveller

Early on EW did test their frustum without a dielectric and made the following comments:

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

Quote
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

Using their published cavity dimensions, TE012 mode at 2.168GHz as input to the EM Drive design calculator, it is clear why they didn't see any thrust. The small end was deeply in cutoff as per the attached EWTest2.

If they had used 2,315,240,095Hz (calculated using Goal Seek), they would have achieved cavity resonance in TE012 mode and assuming a frustum Q of 20,000 measured around 3.2mN of thrust for their 30W of input power. As attached EWTest3.

Maybe all that EW need to do to see significant thrust is to revisit their 1st test (no dielectric) and excite it at 2,315,240,095Hz using an appropriate antenna and antenna placement?
« Last Edit: 05/31/2015 03:39 PM by TheTraveller »
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Offline TheTraveller

It looks instead that you have made an error somewhere, as the natural frequency for mode TE012 without a dielectric insert is substantially lower:

The guide wavelength was way below small end cutoff. Not my equations. Standard microwave stuff. This is based on the standard Shawyer Df equation. Run the numbers, using the Shawyer Df equation yourself.

Here you can see the guide wavelength hits cutoff well before reaching the small end
« Last Edit: 05/31/2015 04:04 PM by TheTraveller »
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Offline Mulletron

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Early on EW did test their frustum without a dielectric and made the following comments:

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

Quote
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

Using their published cavity dimensions, TE012 mode at 2.168GHz as input to the EM Drive design calculator, it is clear why they didn't see any thrust. The small end was deeply in cutoff as per the attached EWTest2.

If they had used 2,315,240,095Hz (calculated using Goal Seek), they would have achieved cavity resonance in TE012 mode and assuming a frustum Q of 20,000 measured around 3.2mN of thrust for their 30W of input power. As attached EWTest3.

Maybe all that EW need to do to see significant thrust is to revisit their 1st test (no dielectric) and excite it at 2,315,240,095Hz using an appropriate antenna and antenna placement?

That doesn't seem to add up. I think the lack of thrust was due to the antioxidation coating. They were also using comparatively low power vs Shawyer.

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1361900#msg1361900
« Last Edit: 05/31/2015 04:06 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline TheTraveller

Early on EW did test their frustum without a dielectric and made the following comments:

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

Quote
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

Using their published cavity dimensions, TE012 mode at 2.168GHz as input to the EM Drive design calculator, it is clear why they didn't see any thrust. The small end was deeply in cutoff as per the attached EWTest2.

If they had used 2,315,240,095Hz (calculated using Goal Seek), they would have achieved cavity resonance in TE012 mode and assuming a frustum Q of 20,000 measured around 3.2mN of thrust for their 30W of input power. As attached EWTest3.

Maybe all that EW need to do to see significant thrust is to revisit their 1st test (no dielectric) and excite it at 2,315,240,095Hz using an appropriate antenna and antenna placement?

That doesn't seem to add up. I think the lack of thrust was due to the antioxidation coating.

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1361900#msg1361900

I'm using microwave industry cutoff equations that are used in the Df equation. The example Df & frequency SPR quoted to me match what the EM Drive Calculator generated.

I have rechecked the cutoff and guide wavelength equation. They are as per microwave industry usage.
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Herman Melville, Moby Dick

Offline TheTraveller

It looks instead that you have made an error somewhere, as the natural frequency for mode TE012 without a dielectric insert is substantially lower:

The guide wavelength was way below small end cutoff. Not my equations. Standard microwave stuff. This is based on the standard Shawyer Df equation. Run the numbers, using the Shawyer Df equation yourself.
Exactly, you are using approximations that are not as good as COMSOL Finite Element Analysis or an exact solution in terms of Legendre Associated functions and spherical Bessel functions.  Those handbook formula approximations used in the spreadsheet cannot be relied to make statements to such a degree of precision.

The Finite Element solution and the exact solution do not use that formula you are using for cut-off wavelength.  The FEA and the exact solution automatically cut-off modes based on the eigenvalue problem solution.  No side conditions with approximate formulas.

Cutoff wavelength and guide wavelength in a circular waveguide of diameter X at external frequency Y at excitation mode TE01 are fairly simple stuff.

Inside of using your fancy programs, try it the way engineers do. Use a calculator.

Would really like to know where and how those microwave industry standard cutoff & guide wavelength equations are generating results that your programs say are incorrect.
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Herman Melville, Moby Dick

Offline TheTraveller

Okay, seriously can we get past this back and forth arguing between the traveler and rodal.  Its giving me a headache and its deluding the conversation for us all.

I think it is important to know why my EM Drive Calculator, which is based on microwave industry & SPR equations for Df, shows the EW frustum was in cutoff and not capable of generating thrust, while COMSOL says it was not in cutoff and should. Note here the actual result was no thrust as predicted by the Calculator.

I'm an engineer, I need the numbers to stack up and it they don't, I need to know why. If my Calculator is in error, then I need to fix it. But so far it is predicting what SPR is measuring.

Please understand the small end being in cutoff to the guide wavelength only involves TE01 mode. It does not involve TE012 as that is about 2 x 1/2 waves fitting in between the end plate spacing. So the length mode is not involved in small end cutoff. Only diameter, BesselJ cutoff function at the TE01 excitation mode and external Rf frequency are involved.

Here is the test:

Show where a 0.1588m diameter circular waveguide can propagate a 2.168GHz signal at TE01 mode. All the microwave industry equations say it can't, so why does COMSOL say it can??

If I have this wrong, then the basis of the Df equation is wrong.

Cutoff and guide wavelengths from here:
http://www.tuks.nl/pdf/Reference_Material/Circular_Waveguides.pdf
« Last Edit: 05/31/2015 04:45 PM by TheTraveller »
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Offline aero

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I think it is important for all to remember that the EM drive is a physical system, not a mathematical one. In the physical system, cutoff is not a line in the sand that you shall not cross, rather it is (probably) the center of a range where propagation drops below some relative value of db. The EM drive will do as it does over a range of frequencies, plus or minus, just some will do better than others.

Add: Its also important that the magnatron drive is a noisy source so the cavity will select its own operating frequency. It would be nice to have the maximum power transfer from source to cavity but very often "Perfect" is the enemy of "Good enough."
« Last Edit: 05/31/2015 04:57 PM by aero »
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Offline Mulletron

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Yes and as much of early thread 2 will attest, using methods for calculating cylinders will get you close to frustums but no cigar. Also the accuracy of Eagleworks Comsol simulations has been proven accurate using physical measurement (thermal camera for example).
Challenge your preconceptions, or they will challenge you. - Velik

Offline TheTraveller

I think it is important for all to remember that the EM drive is a physical system, not a mathematical one. In the physical system, cutoff is not a line in the sand that you shall not cross, rather it is (probably) the center of a range where propagation drops below some relative value of db. The EM drive will do as it does over a range of frequencies, plus or minus, just some will do better than others.

Good call as yes there are rarely black and white lines in engineering.

Still would be interesting to see EW run their cavity, without a dielectric at the 2,315,240,095Hz the Calculator and indirectly SPR says should generate max thrust of around 3.2mN for 30W input with a Q of 20,000?
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

Yes and as much of early thread 2 will attest, using methods for calculating cylinders will get you close to frustums but no cigar. Also the accuracy of Eagleworks Comsol simulations has been proven accurate using physical measurement (thermal camera for example).

Back then a proper Df equation did not exist nor an understanding how the SPR method of Df > length resonance > thrust (at selected mode) method hangs together.

With respect to COMSOL, so far all it has been able to do is to predict thrust with dielectrics. From my reading of the past comments, COMSOL never predicted any thrust without a dielectric. So if it can't predict thrust without a dielectric, as SPR can, why is it being used to try to model what is happening inside a cavity that has no dielectric?
"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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