EM Drive

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

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Tom Ligon
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Re: EM Drive

Post by Tom Ligon »

GIThruster,

But the advantage of using a microwave oven magnetron is that they're cheap. Yes, they're fraught with problems, but you can afford to make mistakes with them.

At EMC2 we had great fun with them and were unafraid to use them. Mostly we were after ECR effects, which were not very critical. But the expensive tuneable TWT system was never even switched on while I was there, for fear of breaking it.

Problems with microwave oven magnetrons: high filament current, and not much ability to dissipate heat. Attention would be needed to lead routing to minimize magnetic fields. Runs must be short or the thing would certainly melt down. They're designed to launch power into a short waveguide. On PXL1 we could launch straight into the chamber. On WB3 the same tube on the same plate, nestled down in a port, put out nothing ... the geometry was wrong. But we found we could strip 1/4 wave of microwave grade coax and stick it in the right spot in a waveguide, and couple most of the power into coax, putting it where-ever we liked.

For an EM drive, if phase and tuning are critical, a microwave oven magnetron will jitter frequency all over the place. They're not precise.

In a microwave oven, they usually pulse at 60 Hz off a partial voltage doubler supply, but we were able to run them continuously on a HV switching supply.

All told, cheap magnetrons are good training, and confidence builders.

Richard Hull would probably find a $10k magnetron, or a $70k TWT, for $5 at a hamfest, and give me heck for paying full price for a $20 microwave oven magnetron.

Lord knows what NASA spent on their hardware.

GIThruster
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Re: EM Drive

Post by GIThruster »

I've had some recent requests to be added to Jim's general reading list. Just to remind, Jim is on vacation in CO for the summer, and one of the other physicists at Fullerton, Dr, Heidi Fern, along with one of her grad students is refitting the lab with Labview. This should be in service around September when Jim returns. During the school year, it is Jim's habit to write his general reading list with the details of each week's work, including data both raw and analyzed, with photos and charts, etc. He spends a huge amount of time to ensure the work remains open science, and if you want to be on the receiving end of all that data, write me here with your email address, and a couple sentences about your background (if you're an EE, this is the place to tell him) and interests. This is not an interview but this list is no place for kids, etc. It's where generals, intelligence officers and captains of industry keep tabs on Jim's work. Please treat the list with respect.

There are perhaps a score of Talk-Polywell people who have been added to Jim's list over the years and some have remained a continuing part of the process. You're invited to peek over his shoulder as he does this work.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Aero
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Re: EM Drive

Post by Aero »

Tom

Go for it. Maybe dirty input power will give a stronger signal - No one knows. The key will be detecting a force, then eliminating known error modes by evaluating the cause of that force. Ultimately this process will likely lead to characterizing the input power but the first milestone is to measure a force that has a chance of including the EM Drive phenomenon.

The Chinese measured 0.78 newton at 2.5 kW. Is there a way that the device could be fed by more than one magnetron? It seems pretty clear to me that destructive interference would reduce/eliminate any "real" force. What is not so clear is that magnetrons from the same manufacturer would not be phase locked by the 60 cycle wall plug power. If that was the case then a series of magnetrons fed via a power strip could get them all started simultaneously. With just a little tinkering with the length of the RF coax feed to synchronize the signal at the device interface it could be driven with several kW.

And don't be concerned with a vacuum chamber until after you have measured a force and can no longer find spurious causes it.

Thing is, I keep forgetting that you have a pretty good background as an experimentalist. Please pardon my noise, I just hope there is a signal in there.

JMO
Last edited by Aero on Tue Aug 12, 2014 7:09 pm, edited 1 time in total.
Aero

GIThruster
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Re: EM Drive

Post by GIThruster »

Tom Ligon wrote:Lord knows what NASA spent on their hardware.
I have no idea. I recall that Paul asked me to look for a "continuous wave magnetron" for them at the time, but I was unable to find a cheap one. That's no longer true. This is something like what you need, but again, confer with Paul. Write me privately if you're serious about this and want his email.

http://www.ebay.com/itm/Continuous-Wave ... m1c60ca43f
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Betruger
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Re: EM Drive

Post by Betruger »

Hopefully Tom doesn't go dark on us like EMC2 ...
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.

Aero
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Re: EM Drive

Post by Aero »

I found this very readable and informative paper on Casimir force. I recommend it highly.

http://www.phys.lsu.edu/~jdowling/PHYS7 ... onni92.pdf

Did you ever wonder why liquid helium climbs the wall of a beaker? The "How" is explained in this paper. I doubt that helium has ever been asked, "Why?"
Aero

Tom Ligon
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Re: EM Drive

Post by Tom Ligon »

Aero,

Microwave oven magnetrons are assigned a band that's largely unregulated. All they are is a diode with a couple of ceramic magnets producing about 875 gauss in a tuned cavity so that it just naturally makes 2.45 GHz electron gyrofrequency. The band is just enough that this rough natural way of making the thing ring will work well enough. Precision? Phase locking? Hah.

Although possibly one could fine tune the frequency a little by adding a field control coil.

We picked up an old HP boat anchor spec-annie from a hamfest to get some idea what the output was like. Running on 60 Hz it was a hashband. Running from a DC HV supply it was better, but we still saw considerable bandwidth of "hash".

So if tight frequency and phase control are needed, likely the microwave oven hardware would just be used during the low end of the learning curve. Without taking the first step, you might never get the chance to take the second. Or if you blew an expensive piece of equipment by trying to start out with two large a step, you might never get to try it again.

A lot will depend on the actual physics behind the anomaly. If any.

I'm wondering if it would be possible to find some waveguide configuration that let you "pipe in" microwaves from outside. Putting microwaves thru windows on a vacuum system is common enough ... WB-8 and WB mini are evidently criss-crossed with them, as was HEPS. Not having the source inside would be a big help in a lot of ways. And upgrading from microwave oven junk to quality equipment could be done without opening the system, saving not just a lot of fiddling in close quarters and dealing with stray effects and connections, but also considerable pump-down time and outgassing.

Aero
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Re: EM Drive

Post by Aero »

Tom Ligon wrote:Aero,

snip -
So much for 10's of kW from 10 or 20 oven magnetrons. Without a bunch of field control coils, band pass filters, a scope or scopes and limited frequency drift ... well the list goes on.
A lot will depend on the actual physics behind the anomaly. If any.
The physics might be due to the Topological Casimir Effect. See:
http://arxiv.org/pdf/1301.1706v2.pdf
The Topological Casimir Effect is very small, even when compared to the well known Casimir Effect. But, toward the end of the paper the author imposes a magnetic field perpendicular to the plates which acts to amplify the signal, at least in his model. There was no supporting experimental data as the paper is only a year or so old. And of course he did not consider anything other than a steady state magnetic field.
I'm wondering if it would be possible to find some waveguide configuration that let you "pipe in" microwaves from outside. Putting microwaves thru windows on a vacuum system is common enough ... WB-8 and WB mini are evidently criss-crossed with them, as was HEPS. Not having the source inside would be a big help in a lot of ways. And upgrading from microwave oven junk to quality equipment could be done without opening the system, saving not just a lot of fiddling in close quarters and dealing with stray effects and connections, but also considerable pump-down time and outgassing.
You could spend a lot of time and effort working on a vacuum chamber then have no idea what level of signal to expect as output. I'd run the experiment without a vacuum as has been reported by others. Then if you get a good signal, move on to vacuum testing. Of course I'd be cognizant of the hope to find a signal necessitating moving on to vacuum, and so design my experimental hardware with vacuum in mind. But as for using vacuum, I'd wait until it could prove something.
Aero

tokamac
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Re: EM Drive

Post by tokamac »

Tom, magnetrons are cheap, but they scream too much different frequencies, out of the resonance you need for the cavity. Because of that you only finally get a marginal amount of effective power used for resonance in the cavity, even with a 2.5 kW magnetron.

You'd rather choose klystrons.

Klystrons offer higher power and very stable frequencies in a narrower range over magnetrons. They are more precise. Here are some klystrons in the kW range for sale on eBay.

Excerpt from Fernando Minotti's paper:
Minotti wrote:The values reported in (the Chinese 2012 paper) are not easy to compare with as the power of the microwave source is distributed over a rather wide range of frequencies, so that the actual power into the resonant mode is not precisely defined. Using a spectrum analysis of the power source the authors evaluate, for instance, that when Fz = −0.3N the actual power into the resonant mode is P = 0.12kW, which would correspond to Fz = −2.5N at P = 1kW"
Please note: only 120 watts of actual power used at resonance, while injecting several kilowatts in the cavity… magnetrons are easy to get and to use, but they are not effective at all for those experiments.

hanelyp
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Re: EM Drive

Post by hanelyp »

If I were testing something line EMdrive I'd think about building a magnetron or klystron into the resonant chamber, using the chamber resonance as the time base.
The daylight is uncomfortably bright for eyes so long in the dark.

Aero
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Re: EM Drive

Post by Aero »

Quoting from the professional English translation of the Chinese paper,

http://www.emdrive.com/yang-juan-paper-2012.pdf
Using a microwave network analyzer
and spectrum analyzer for measurement, it was discovered that this experiment's frustum
microwave resonator has an extremely narrow resonant frequency bandwidth, of only 0.0016GHz;
furthermore, with the magnetron microwave source actual output power in this experiment, within
this narrow frequency range, a non-linear change with the microwave output power is found.
In other words, they made their thruster so that it resonated over only 1.6 MHz bandwidth. When frequency drifted on their 2.45GHz driving magnetron the power coupling went to h... , well it went down drastically.

Is it possible to design one of these EM Thruster devices to have a wider resonant bandwidth?
Aero

Tom Ligon
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Re: EM Drive

Post by Tom Ligon »

I kinda like what Tokamac had to say on it ... probably does need a better source. I have not used klystrons yet.

If the thruster cavity is not tunable, the source probably should be. Or must be. Particularly once you are in a vacuum, trying to tune a cavity in a vacuum would be more trouble than enough.

I suspect the HEAS guys have all this stuff in their basements. Hull is such a talented scrounge he may have it all stashed around the lab with his big Tesla coil, along with the high vacuum stuff he uses with his fusors.

Or then there is they guy here in Manassas with the three tunable dye lasers. Yeah, an HEAS member with three of those suckers, bought new, surplus, cheap. In his garage. I'm telling ya, these guys have some serious sh.... stuff.

Why lasers? If this is the effect described to me, and probably what the Chinese think they're doing, it works dramatically better at shorter wavelengths. Including with light.

2.45 GHz is training wheels. But sparsely regulated and common.

Carl White
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Re: EM Drive

Post by Carl White »

One concern about the Cannae drive tests is that, given they were performed at ambient air pressure, any apparent thrust might be the result of uneven heating of the device. A hot patch would heat the air nearby and thereby increase the pressure upon it.

Did anyone try to do any thermal imaging of the device after it had been under power for a while?

Aero
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Re: EM Drive

Post by Aero »

Speaking of lasers - How small would the thruster cavity need to be to resonate at light wavelength/frequency? Wouldn't that be just a little difficult to instrument?

@ Carl White - Remember that the thrust was measured in the axial direction from the big end to the small end. I don't see hot air hanging around the outside of the big end, which is vertical, and I don't understand how air pressure could build inside the small end of the device without pressurizing the whole thing.

But the whole thing leaks which leaves the option of a jet of air pressure through a hole in the back. My most rational counter to that is that all three test devices showed a thrust in the same direction. (That is, Shawyer's, Juan's, and White's) It doesn't seem reasonable to me that they all three would have an accidently located hole in the back to make the thrust, and I don't for a minute think there is a conspiracy to make us believe it.
Aero

tokamac
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Re: EM Drive

Post by tokamac »

I don't think you can pump several kilowatts of laser energy into a cavity… or can you? You have a quite powerful laser then. I know military firms like Lockheed or Boeing produced 10 to 30 kW lasers, but lasers available for people on the market nowadays are from milliwatts to a a few watts only.

Pay attention, you're speaking of using lasers as if you known the real underlying process of thrust generation in those frustum cavities. Yet Shawyer's explanation about thrust caused by radiation pressure imbalance due to different group velocities on both ends of the cavity is only a possibility, and it breaks the law of conservation of momentum.

In NASA's low power experiments of an RF resonant tapered cavity, they used a couple of polyethylene (PE) dielectric discs inside the cavity, near the small end. And the fact is they got no thrust at all when they removed the PE discs and ran the cavity at the resonant frequency. This implies several things:
  • No circulating ambient air current due to heat gradient on cavity's structure is the cause of thrust. Because "heating the cavity" with no PE disc inside would have produced the same air current and displacement. It didn't.
  • Shawyer and the Chinese didn't use any dielectric within their cavity, but measured net thrust (Shawyer used a dielectric to enhance the effect in his first prototype, but not afterwards).
  • Maybe there was a thrust produced by NASA's EmDrive without dielectric, but the very low power used in these experiments buried this weak thrust below the pendulum's resolution (ability to detect a force above 1-5 micronewtons). We'll know a bit more about this in NASA's upcoming high power tests in Fall 2014.
  • The dielectric enhancement is MAYBE an indication of a Mach effect (M-E) as explained by Woodward's Transient Mass Equation (TME). Then a cavity without a dielectric could produce a (weaker) thrust because its metallic walls are slightly electrostrictive:
Jim W. mentioned to me when asked that all metals are weakly electrostrictive.   So at sufficiently high RF power levels multiplied by the resonant cavity’s Q-factor, which yields the peak E-fields obtainable on the surface of the resonant cavity’s walls with a given input power, similar force rectification process could be generate especially since the M-E and the Q-Thruster models predict force output scaling proportional to the E-field strength to the fourth power (V^4).  Talk about non-linear responses!

If you salute the M-E, the RF excited dielectric generates a vast horde of ions undergoing accelerations and decelerations during each RF cycle that in turn generate an 2w electrostrictive response in the dielectric that could under the correct E&M mode and physical configurations, force rectify the dielectric vibrations induced in the dielectric by the RF over a full RF cycle into a unidirectional thrust.  The same can be said for the QVF/Q-Thruster model since each of the vibrating ions in the dielectric could act as wake-field compressors of the quantum vacuum in between the ions, and this densified QVF state could then be forced rectified by the 2w electrostrictive motion of the dielectric ions into a unidirectional force.  The only real difference between the ME and QVF answers then become how conservation of momentum is obtained, with the M-E requiring instantaneous Wheeler/Feynman radiation reaction forces between the locally accelerated ions and the far off active mass of the universe, or the generation of a local but in Woodward’s eyes imaginary quantum vacuum plasma particle wake that conveys the momentum stream out of the “closed” system box of the thruster to the rest of the environment like any other propeller would do in a fluid media.  As to which impossibility you want to sign up for is up to personal tastes, but if Jim’s and our data keep holding up to scrutiny, sign up you will have to do.

Perhaps some evaluation of electrostrictive and magneteostrictive materials is in order within the frequencies of interest to find the best materials to make a cavity from.
  • And finally, Fernando Minotti's conjecture about Scalar-Tensor theory is easy to test: S-T predicts the thrust increases with the mass of the cavity. And to make the cavity heavier, one does not even have to change the cavity, but simply wrap it with a layer of some heavy material. Both tests (with and without the wrapping) would be done at the same amount of power and EM modes inside of the cavity. If the heavier cavity produces more thrust than the unwrapped cavity, we would be onto something regarding S-T.
Last edited by tokamac on Fri Aug 15, 2014 10:26 am, edited 3 times in total.

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