Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2099181 times)

Online Rodal

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@RODAL

It seems (to me) that that is quite correct, but that does not mean that that is for max force since it neglects frequency.  I can see how that might be for max laser sideband generation w/o constraining the frequency. (ie very high radial modes)
Thanks.  But where does the frequency enter into the equation for L? all I see is a, b, r2bar, r1bar, lo geometrical parameters.  It seems that the electromagnetic field Power only enters through the parameter (Uo)2 which is built inside the length "lo", so as we said, we need a number for "lo" to make any  more progress.

See Marco's Eq. 19, 20 and 28 in http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=830137

It is the choice of the resonant mode that fixes l0 and this depends on frequency (indirectly). You should check Egan link for some numbers to put in.

Yes, thank you.  I actually have a better exact, and more elegant solution than Egan's that unlike Egan's can calculate arbitrary field variation in the azimuthal direction (no I have not published it).  I have calculated higher modes like the one that Eagleworks is running with the frustum (TM212) and my solution is very close to the experiments and the Finite Element calculations.  Greg Egan only shows the solution for constant quantum number m corresponding to constant field in the azimuthal direction.

I think (?) that Notsosureofit's point is that while your paper has a dependence on Uo, it is a single variable, as you said your solution is a first order solution.  But I shouldn't be speaking for him  :)
« Last Edit: 05/17/2015 08:08 PM by Rodal »

Offline txdrive

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With regards to the forces on the side of the cavity, all I can say is, write the field equations for your fields (what is the H and E at a given point in space), then I can calculate the forces on the boundaries and/or show that your fields violate Maxwell's equations. When it is a picture I don't know what exactly you're talking about.

Last line say it all:

Quote
If the absorbing surface is planar at an angle a to the radiation source, the intensity across the surface will be reduced.

The effective radiation source is the vertex of the frustum. The frustum side wall are aligned to, pointing at the vertex. Therefore the radiant pressures on the side walls are zero.
You're ignoring diffraction. If the frustum side walls were not there, the radiation would leak out.

edit: write an equation of form E(position, time) and H(position, time) . Maybe it would be clearer for a cylinder with flat end pieces? You can't just take geometric optics approximation from Wikipedia and apply it to microwaves in a reasonable sized cavity... it won't be correct then.

We were discussing radiation pressure generated from EM waves according to Maxwell's equations (attached). This pressure is apparently subject to cosine angle loss and thus when the EM wave moves along the frustum side walls and is not bouncing off the frustum spherical end plates, there is no Maxwell radiation pressure generated on the frustum side walls.

Or did I not understand what the cosine loss factor is for in the lower of the 2 equations?
It's a geometric optics approximation. Doesn't hold precisely.

For example suppose you got a beam of coherent light, 5mm across, 500nm wavelength, in space. It's not going all parallel to it's original direction, it's spreading, to about 1m across at 10 000m from the source (Makes a fuzzy "Airy disk" pattern).

edit: The Poynting vector on the sides of a perfect cylinder over this beam, is not parallel to the axis. It's this Poynting vector that matters.

Built and used many optical telescopes, including a 12 inch, Schmidt Cassegrain. Diffraction and I got to be good enemies.

There is no natural spread for the beam inside the cavity. It is controlled by the guide and cutoff wavelengths determined by the cavity diameter it travels through
Which only happens thanks to the reflection off the sides.
Quote
and by bouncing off the spherical end plates, which as I see it orient the EM waves so they travel / slide along the side walls at a 0 bounce radiant cosine angle.
What this boils down to, is that if you actually specify the E and H, not with a picture but with equations (note that you can't have a spherically symmetrical wave with EM fields, because it doesn't work like a pressure wave), it will be possible to either show that 1: Maxwell's equations don't hold for E and H, or 2: there is a force on the walls.

By the way both Shawyer and White should do that, give their solution for the field inside the cavity - E and H fields as a function of time and position. White's field has to deviate from Maxwell's equations to net force on the cavity. By an amount that should be very easy to detect electrically (without measuring forces), even if the net force is very small. It is strange to be "weighting" electromagnetic waves when they can be measured more precisely with electronics. A test for an unexpected change in the momentum of electromagnetic waves is best done with a direct measurement of said waves.

If we used radiation pressure measurements to measure radiation, we would never have known that stars other than the Sun exist. We can literally detect trillions times smaller effects by measuring radiation directly than by measuring radiation pressure.
« Last Edit: 05/17/2015 08:19 PM by txdrive »

Offline ThinkerX

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Seems to me that the geometric / electric precision required to make a workable EM Drive is comparable with the degree of precision required in automotive mechanics.  There, if the cylinder is flawed or damaged, the engine either won't work or will work poorly.  (I have known a number of backyard mechanics who wrongly thought they could re-bore the cylinders on their engines to the required degree of precision).   

Offline Iulian Berca

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Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.



I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.

Offline RotoSequence

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Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.

I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.

Interesting results, but since the apparatus has been changed and the orientation of the device altered, and there's no dielectric material in the cavity providing an extra experimental variable, wouldn't it be prudent to test for a thermal explanation of the thrust before modifying the device?

Offline davish

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Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.



I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.

Do you have the weight of the setup, so that we can calculate the newtons of thrust from this?

Offline txdrive

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Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.



I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.
Beware of buoyancy, thermal expansion of cables, magnetic forces on cables, vibration, etc etc. Also, most importantly, safety: you got high voltage and microwaves that can really damage your eyes (so don't be closer than a couple meters from it when it is on). Unless you get the same thrust upwards as downwards down to, say, 5% , with less than 5% of the thrust if you mount it sideways, without excessive fiddling and adjustments, I would just describe it as a deflection rather than thrust. Thrust is a hypothesis, and an experimenter should be impartial towards hypotheses. Essentially without tests sideways (so the weight change is zero) and upside down, it is less rigorous than soft sciences (which nowadays employ controls).
« Last Edit: 05/18/2015 12:52 AM by txdrive »

Offline TheTraveller

Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.



I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.

Do you have the weight of the setup, so that we can calculate the newtons of thrust from this?

-0.508gf is about 4.98 mN upward force.

Shawyers 1st device best result was 16mN at 850W input power.

http://emdrive.com/feasibilitystudy.html
« Last Edit: 05/18/2015 01:08 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

Online Rodal

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....

Dear Jose,

Thank you a lot for your effort to this question. Also thanks to @notsureofit for his help. You are right. I have checked this with Maple and optimized the function L(r) as a function of r1, r2 and U0 also. And yes, r1=r2 is the solution! I have other checks to do and my notebook just keeps on freezing for a computation of these but I hope to complete all in a few days.

This means that Harold White experiments could represent a great leap beyond in experimental general relativity. This was my initial hope. As a theoretical physicist please don't ask me about applications!

Give me a few days for further checks and I will update my draft, with due acknowledgements.

Regards.

Dear Marco,

As you said, "the geometry comes to the rescue".  Yes it does !

One must consider in detail what happens at r=r1 for r1 approaching zero:  r1 -> 0 the Log[c] term gets removed and geometry comes to the rescue!


When I consider what happens at r=1 in detail, it turns out that the pointy cone, with r1 -> 0 is the key.

All the interesting action takes place near r=r1, for r1 -> 0

Of course, the pointy cone is an abstraction that we cannot obtain in practice.

I look forward to you running some numbers during the coming days   :) to further throw light on this.

Please see:  http://forum.nasaspaceflight.com/index.php?topic=36313.msg1375542#msg1375542
« Last Edit: 05/18/2015 01:58 AM by Rodal »

Offline phaseshift

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It's awesome to see the above results. Kudos!

In the meantime the script that is being worked on now generates the large plate from a couple parameters - length of the untruncated cone and the diameter of the large end of the cone). 

The thickness is calculated by taking the depth of the concave surface and adding a couple millimeters.

In this run the untruncated cone is 357.2 mm in length and the diameter of the concave area is 223.8 mm with a depth of 17.9 mm.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline kdhilliard

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Test 03 Success. I have thrust.

I'm new to this thread, but doesn't Shawyer's theory paper say that it is supposed to be Big-Endian?  That is, that a larger force is applied on the inner face of the big end than on the inner face of the small end, so that if it were flying free in space it would accelerate big end first?

Is Iulian's Little-Endian negative reading consistent with other theory or experimental results?

~Kirk

Online Rodal

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Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.



I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.

Congratulations !

In the best tradition of



Traian Vuia Romanian inventor and aviation pioneer who designed, built and tested a tractor configuration monoplane. He was the first to demonstrate that a flying apparatus could rise into the air by running upon wheels upon an ordinary road.He is credited with a powered hop of 11 metres (36 feet) made on March 18, 1906 and he later claimed a powered hop of 24 metres (79 feet)

« Last Edit: 05/18/2015 01:27 AM by Rodal »

Offline TheTraveller

Test 03 Success. I have thrust.

I'm new to this thread, but doesn't Shawyer's theory paper say that it is supposed to be Big-Endian?  That is, that a larger force is applied on the inner face of the big end than on the inner face of the small end, so that if it were flying free in space it would accelerate big end first?

Is Iulian's Little-Endian negative reading consistent with other theory or experimental results?

~Kirk

Watch Shawyers dynamic test.
http://emdrive.com/dynamictests.html

Moves toward small end. So both tests generate device movement in the same direction. Toward the small end.
« Last Edit: 05/18/2015 01:28 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 demofsky

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Test 03 Success. I have thrust.

I'm new to this thread, but doesn't Shawyer's theory paper say that it is supposed to be Big-Endian?  That is, that a larger force is applied on the inner face of the big end than on the inner face of the small end, so that if it were flying free in space it would accelerate big end first?

Is Iulian's Little-Endian negative reading consistent with other theory or experimental results?

~Kirk

Watch Shawyers dynamic test.
http://emdrive.com/dynamictests.html

Moves toward small end. So both tests generate device movement in the same direction. Toward the small end.

Also interesting, and just to remind folks, it appears that Iulian has the waveguide directly inside the fulstrum ending some what near the centre of the cavity.  Sawyer, et al all seemed to use an antenna of some type that was close to one side of the cavity.

Offline TheTraveller

Test 03 Success. I have thrust.

I'm new to this thread, but doesn't Shawyer's theory paper say that it is supposed to be Big-Endian?  That is, that a larger force is applied on the inner face of the big end than on the inner face of the small end, so that if it were flying free in space it would accelerate big end first?

Is Iulian's Little-Endian negative reading consistent with other theory or experimental results?

~Kirk

Watch Shawyers dynamic test.
http://emdrive.com/dynamictests.html

Moves toward small end. So both tests generate device movement in the same direction. Toward the small end.

Also interesting, and just to remind folks, it appears that Iulian has the waveguide directly inside the fulstrum ending some what near the centre of the cavity.  Sawyer, et al all seemed to use an antenna of some type that was close to one side of the cavity.

In the 1st EM Drive device, Shawyer fed the microwaves in via a short waveguide to around the centre of the frustum. You can see the wave guide at the rear of the frustum.

In the next Demonstration EM Drive, the magnetron generated microwaves were fed into the frustum at a point near the big end as can be seen in these 2 last images.

The 3rd device, the Flight Thruster, used a coax Rf feed at near the big end.

So it would seem near the big end feeding will work.
« Last Edit: 05/18/2015 01:59 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

Online Rodal

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Test 03 Success. I have thrust.

I'm new to this thread, but doesn't Shawyer's theory paper say that it is supposed to be Big-Endian?  That is, that a larger force is applied on the inner face of the big end than on the inner face of the small end, so that if it were flying free in space it would accelerate big end first?

Is Iulian's Little-Endian negative reading consistent with other theory or experimental results?

~Kirk

1) The acceleration and displacement occurs towards the small end. That's what matters. What gets measured are displacements (and hence a force due to Force=stiffness*displacement) or acceleration (and hence Force=mass*acceleration).

2) Shawyer claims that this is a result of a recoil force (just as when you fire a gun) due to a thrust force towards the big end.  Shawyer's explanation for this "thrust" runs against what we know about Maxwell's equations because the EM Drive is a closed cavity and there are no particles escaping.  However, NASA Eagleworks does not claim this and there are other, more scientific theories to explain what may be happening (if the effect is not an artifact).
« Last Edit: 05/18/2015 02:00 AM by Rodal »

Offline demofsky

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Test 03 Success. I have thrust.

I'm new to this thread, but doesn't Shawyer's theory paper say that it is supposed to be Big-Endian?  That is, that a larger force is applied on the inner face of the big end than on the inner face of the small end, so that if it were flying free in space it would accelerate big end first?

Is Iulian's Little-Endian negative reading consistent with other theory or experimental results?

~Kirk

Watch Shawyers dynamic test.
http://emdrive.com/dynamictests.html

Moves toward small end. So both tests generate device movement in the same direction. Toward the small end.

Also interesting, and just to remind folks, it appears that Iulian has the waveguide directly inside the fulstrum ending some what near the centre of the cavity.  Sawyer, et al all seemed to use an antenna of some type that was close to one side of the cavity.

In the 1st EM Drive device, Shawyer fed the microwaves in via a short waveguide to around the centre of the frustum. You can see the wave guide at the rear of the frustum.

In the next Demonstration EM Drive, the magnetron generated microwaves were fed into the frustum at a point near the big end as can be seen in these 2 last images.

The 3rd device, the Flight Thruster, used a coax Rf feed at near the big end.

So it would seem near the big end feeding will work.

Thanks for this.  :)   I never noticed the waveguide in the first device!  Do you know if the waveguides terminated at or near the interior surface of the fulstrum?

Offline aero

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If any calculated results from Meep are relevant then note that Meep calculates the largest thrust, O(1.1/c), when the antenna is dead center in the cavity. That is a point source. A dipole source is centered and parallel to the base plates for electric stimulation, and parallel to the axis of symmetry for magnetic stimulation.

Moving the antenna away from center reduces the detected force/flux ratio.
Retired, working interesting problems

Offline zellerium

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Test 03 Success. I have thrust.
I modified the setup and now i weight the frustum. the precision is much better.

I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.

Iulin Berca:

Congratulations on the success! I think this demonstration is fantastic. The fact that the peak thrust appears ~3 seconds after the power is turned on tells me it takes a little while for energy to 'build up' in the cavity. After the peak, the thrust slowly dies probably because the cavity walls are warping and you are losing resonance.

The adjustable end plate would certainly help to achieve a higher peak thrust, it just might take some trial and error. But I believe cavity will still heat up and warp and the thrust will taper off.

Maybe this thermal effect could be mitigated using some sort of heat sink?

Offline deltaMass

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If I did the calculation right, a volume change of ~125 litres would be needed to account for this apparent weight change, due to thermal ballooning of a sealed volume. That's far too high a change in volume that could be reasonably expected, so it can't be the whole story.  Did I calculate this right?
air density = 4*10-4 Kg/m3
« Last Edit: 05/18/2015 03:31 AM by deltaMass »

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