EM Drive

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Betruger
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Re: EM Drive

Postby Betruger » Sun Oct 05, 2014 3:42 pm

birchoff wrote:I genuinely appreciate what Rodal is attempting but at some point he is going to have to come to the conclusion that he doesn't have enough information to conclusively prove that either the devices can actually work or that they cant, along with an explanation of why thrust was being measured in the first place.

I may have missed a crucial bit, but skimming thru latest pages of discussion at NSF shows Rodal wanting a piece of data from Paul March, ostensibly for theoretical proof/disproof that Eagleworks thrust is legit.
You can do anything you want with laws except make Americans obey them. | What I want to do is to look up S. . . . I call him the Schadenfreudean Man.

tokamac
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Re: EM Drive

Postby tokamac » Wed Oct 22, 2014 8:47 pm

EmDrive inventor Roger Shawyer gave a presentation at IAC 2014 conference in Toronto, 3 October 2014:
Second Generation EmDrive Propulsion applied to SSTO Launcher and Interstellar Probe

There are interesting details for a new asymmetric tapered cavity, which is no more a frustum and has several enhancements:
- Cylindrical sector
- Superconducting YBCO cavity with internal liquid hydrogen coolant
- Piezoelectric compensation against cavity deformation
- Vacuum frame made of alloys

Image

But nothing really new, notably no test results of such a cavity for now.

birchoff
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Re: EM Drive

Postby birchoff » Wed Oct 22, 2014 11:33 pm

I was looking forward to this. Got caught up with work so didnt check out shawyers website for a bit.

That said, it is exactly as I suspected. Not much in the way of anything interesting. I was hoping for some test results or something. From my skim of this it looks like a more "rigorous" (using that term VERY VERY loosely) version of the mission specs he has previously detailed.

Unfortunately according to the IAC site it looks like this was an oral presentation so this is just the deck from the oral presentation. Would be nice to know what he said and what questions were asked during the presentation.

RERT
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Re: EM Drive

Postby RERT » Thu Oct 23, 2014 7:37 am

I agree, except for the early slide which mentioned 'CANNAE Superconducting' test results this year at about 900 mN/kW, a much bigger number than I recalled.

tokamac
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Re: EM Drive

Postby tokamac » Sat Oct 25, 2014 8:15 pm

RERT wrote:I agree, except for the early slide which mentioned 'CANNAE Superconducting' test results this year at about 900 mN/kW, a much bigger number than I recalled.

900 mN/kW was the numbers. Cannae claimed to have measured 8-10 mN of thrust with 10.5 watt of power in their superconducting test article in January 2011, so this is indeed a specific thrust of about 760-950 mN/kW. See the page proof-of-concept/experimental-results archived from their web site.

They didn't provide data for any high power test though.

RERT
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Re: EM Drive

Postby RERT » Mon Oct 27, 2014 6:56 pm

Thanks for the pointer, I hadn't seen that. I had in mind numbers of 10's of mN, so don't seem to have done the arithmetic before I filed the number in my head.

stefanbanev
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Re: EM Drive

Postby stefanbanev » Fri Dec 19, 2014 1:46 am

I'm wandering what the advantage of propellant free drive over traditional Newtonian rocketry... a single proton can be accelerated asymptotically close to speed of light as soon as energy supply provides sufficient energy... besides, a single relativistic proton may have mass of rocket once it close enough to speed of light; no need to challenge momentum conservation and still to be able to transfer any amount of electric energy to kinetic energy of rocket with virtually no propellant exhaust... apparently I miss something... may some one explain what I miss here...

RERT
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Re: EM Drive

Postby RERT » Fri Dec 19, 2014 3:00 pm

Its an awful while since I did this class, but think you get to peak ratio of momentum to energy by ejecting momentum as photons at the speed of light. Unfortunately you still need a stupendous amount of energy (E=pc?) to get any sensible mass anywhere fast....

JoeP
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Re: EM Drive

Postby JoeP » Fri Dec 19, 2014 3:08 pm

stefanbanev wrote:I'm wandering what the advantage of propellant free drive over traditional Newtonian rocketry... a single proton can be accelerated asymptotically close to speed of light as soon as energy supply provides sufficient energy... besides, a single relativistic proton may have mass of rocket once it close enough to speed of light; no need to challenge momentum conservation and still to be able to transfer any amount of electric energy to kinetic energy of rocket with virtually no propellant exhaust... apparently I miss something... may some one explain what I miss here...


What kind of infrastructure, equipment/mass will it take to accelerate a small number of protons to the speeds you are indicating?
I suspect this is the kind of thing that quickly breaks down in practice. Bottom line is that ion propulsion is a good thing, but you still lose propellant and there is a balance between engine mass and effectiveness.

stefanbanev
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Re: EM Drive

Postby stefanbanev » Mon Jan 05, 2015 3:41 am

JoeP wrote:
stefanbanev wrote:I'm wandering what the advantage of propellant free drive over traditional Newtonian rocketry... a single proton can be accelerated asymptotically close to speed of light as soon as energy supply provides sufficient energy... besides, a single relativistic proton may have mass of rocket once it close enough to speed of light; no need to challenge momentum conservation and still to be able to transfer any amount of electric energy to kinetic energy of rocket with virtually no propellant exhaust... apparently I miss something... may some one explain what I miss here...


What kind of infrastructure, equipment/mass will it take to accelerate a small number of protons to the speeds you are indicating?
I suspect this is the kind of thing that quickly breaks down in practice. Bottom line is that ion propulsion is a good thing, but you still lose propellant and there is a balance between engine mass and effectiveness.


Well, at sufficient energies the amount of expelled propellant is getting to zero yet it may still provide any gain of momentum.
>"kind of infrastructure"
- it may be laser driven proton acceleration see http://www.wiley-vch.de/berlin/journals ... S56-59.pdf
At least this method does not involve any new physics yet it may provide virtually propellantless propulsion...

Jboily
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Re: EM Drive

Postby Jboily » Sun Jan 11, 2015 5:46 am

stefanbanev wrote:
JoeP wrote:
stefanbanev wrote:I'm wandering what the advantage of propellant free drive over traditional Newtonian rocketry... a single proton can be accelerated asymptotically close to speed of light as soon as energy supply provides sufficient energy... besides, a single relativistic proton may have mass of rocket once it close enough to speed of light; no need to challenge momentum conservation and still to be able to transfer any amount of electric energy to kinetic energy of rocket with virtually no propellant exhaust... apparently I miss something... may some one explain what I miss here...


What kind of infrastructure, equipment/mass will it take to accelerate a small number of protons to the speeds you are indicating?
I suspect this is the kind of thing that quickly breaks down in practice. Bottom line is that ion propulsion is a good thing, but you still lose propellant and there is a balance between engine mass and effectiveness.


Well, at sufficient energies the amount of expelled propellant is getting to zero yet it may still provide any gain of momentum.
>"kind of infrastructure"

- it may be laser driven proton acceleration see http://www.wiley-vch.de/berlin/journals ... S56-59.pdf
At least this method does not involve any new physics yet it may provide virtually propellantless propulsion...


The thing is, with the Ions Drives the faster the Ions, the more energy per N*m of momentum, leading to very low energy to thrust conversion rate, most particularly at the lower spacecraft speed. While with the EM Drive (if it is actually working as described), you would get very efficient energy to momentum conversion, most specially at very low spacecraft speed.

You are talking improvement in the 1000% or more.

Aero
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Re: EM Drive

Postby Aero » Mon Jan 12, 2015 9:49 pm

For the last 2-3 months I have been pursuing the possibility of evanescent waves being the source of the EM Drive effect. For those unfamiliar, http://en.wikipedia.org/wiki/Evanescent_wave
An evanescent wave is a near-field wave with an intensity that exhibits exponential decay without absorption as a function of the distance from the boundary at which the wave was formed. Evanescent waves are solutions of wave-equations, ...


I have some results.

Using FDTD software developed at MIT, and my 5 y/o home computer, I modeled the experiment done at NASA Eagleworks, presented here: http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf I found the following salient points. First, my computer is not powerful enough to perform FDTD calculations in high resolution, so I'm stuck with moderate resolution at best. That rules out resolving the thin copper sheets on the circuit board ends of the cavity. Second, there isn't any data that I can discover describing copper at this frequency and the power level experienced by the cavity ends. Sure, lots of data on copper for shielding, but...

Consider that operating at Q = 22,000 and drive power of 2.6 watts with the cavity end diameter giving an area of 0.058 m^2 the radiation intensity approaches 1 MW/m^2 for the Eagleworks tests, and for higher power devices, 1 kW/cm^2. That is a lot of power and it seems no one has researched the behavior of copper under those intense conditions.

With those two points understood, I did calibrate the FDTD model to a photon rocket, giving thrust of very nearly 1/c as it should. This is with the detector plane about two cavity lengths behind the source antenna.

For the reasons given above, I used a perfect metal or ideal conductor as the material for the Eagleworks cavity model. Not surprisingly, when I ran the model totally enclosing the source with perfect metal, there was zero force detected. That result has been calculated analytically and discussed widely.

I went further, considering that the end is bolted onto the cavity, what if it leaks RF? I modeled a narrow slice around the circumference of the cavity cone in the end plate, a variable sized opening but at the smallest resolution my computer will allow, 0.2% of the cavity large end radius, about 0.27 millimeters for the Eagleworks device.

The simulation detected Force/Power ranging from 2/c to more than 3/c.

That is two to three times the thrust of an ideal photon rocket. I think the cause of the force is evanescent waves escaping through the very narrow gap in the cavity base.

My data does not answer the question, "What causes the thrust of the EM drive?" It does point in a direction.

Some may object that these results are no better than the Woodward device gives. It is not my purpose to create a new or different kind of thruster but to investigate the cause of EM drive forces. I do note that making a resonate cavity with a loose end cap should be much easier than making a Woodward device for the same thrust.

I'm sure someone will ask, so, “Yes, I did look at forces generated by similar gaps in the small end of the cavity.” Forces exist but only about one forth as great as at the large end. That may be directly due to the gap area, the small end circumference being about half that of the large end, and the dielectric does interfere. I should probably remove the dielectric and run some small end test cases. However, I suggest that a better solution when constructing a test article, is that the small end of the cavity be heavily plated, sealed tight with no leaks.

I can run more cases with low to moderate resolution and perfect metal, but as I wrote at the top, I need a bigger computer and better knowledge of copper behavior under intense radiation in order to calculate definitive results.
Aero

GIThruster
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Re: EM Drive

Postby GIThruster » Mon Jan 12, 2015 11:29 pm

How does the evanescent wave explanation answer objections that this violates conservation?
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Aero
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Re: EM Drive

Postby Aero » Tue Jan 13, 2015 2:10 am

GIThruster wrote:How does the evanescent wave explanation answer objections that this violates conservation?

Oh, I failed to mention a very important fact which has recently received considerable attention in medical sensor research and measurements. That is that evanescent wave photons can, in some circumstances have superluminal momentum. That is both linear and spin momentum. Reading one of these research papers is what started me on this path in the first place. A common experiment is to use evanescent waves to move and spin gold particles. That movement is a physical result.

http://arxiv.org/pdf/1308.0547.pdf from page 5,
First, note that the evanescent wave (7) possesses longitudinal canonical momentum pzO∝kz>k, which exceeds the momentum of a plane wave with the same local intensity.

What that means to me is, since p = mv > mc, v/c > 1 from evanescent photons, then F/P >1/c, and it says nothing at all to contradict E = mc^2. So energy is conserved and momentum is conserved. The new thing is the recognition that v>c is a solution to the wave equations and that that solution is physical.

Of course I might be on safer ground if I just considered mv/mc >1 and leave it at that. The result F/P >1/c still follows.
Aero

kunkmiester
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Re: EM Drive

Postby kunkmiester » Tue Jan 13, 2015 7:50 am

That is that evanescent wave photons can, in some circumstances have superluminal momentum.
What's the difference between momentum and velocity(?) here?
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