EM Drive

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

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rcain
Posts: 992
Joined: Mon Apr 14, 2008 2:43 pm
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Re: EM Drive

Post by rcain »

Guys,

i just caught the story on EM/VE drives on:

http://nasawatch.com/archives/2014/08/j ... A+Watch%29

http://sploid.gizmodo.com/nasa-reveals- ... socialflow

via twitter.

what's the reckoning here? how seriously should we treat the claim?

djolds1
Posts: 1296
Joined: Fri Jul 13, 2007 8:03 am

Re: EM Drive

Post by djolds1 »

rcain wrote:Guys,

i just caught the story on EM/VE drives on:

http://nasawatch.com/archives/2014/08/j ... A+Watch%29

http://sploid.gizmodo.com/nasa-reveals- ... socialflow

via twitter.

what's the reckoning here? how seriously should we treat the claim?
With extreme but for now reserved skepticism.

Tho Tom Ligon idicates we might want to keep our eyes open:

viewtopic.php?f=10&t=5469#p113699
Vae Victis

birchoff
Posts: 200
Joined: Sun Jul 27, 2014 7:11 pm

Re: EM Drive

Post by birchoff »

GIThruster wrote:Links aren't working for me either but it does look like an improved version of Shawyer's EM Drive. Amazing to me folks still don't get that this violates' conservation.
Someone commenting on the Arstechnica article covering the wired.uk and pbs articles. Thought to use the way back machine to uncover what the actual content was on the cannae links covering the theory.

Numerical Method Results:
http://web.archive.org/web/201302132304 ... od-results

Experimental Results:
http://web.archive.org/web/201211020827 ... al-results

Principles of Operation:
http://web.archive.org/web/201211020832 ... -operation

should save someone the $25 bucks of buying access to the paper on AIAA since the content of these pages look like what is in their AIAA paper at a glance.

Betruger
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Joined: Tue May 06, 2008 11:54 am

Re: EM Drive

Post by Betruger »

Birchoff your links are shortened by forum autocorrect. You have to put them in tags. edit- [url=http://web.archive. ... od results - 13 feb 2013
Experimental results - 2 nov 2012
Principles of operation - 2 nov 2012
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.

birchoff
Posts: 200
Joined: Sun Jul 27, 2014 7:11 pm

Re: EM Drive

Post by birchoff »

Betruger wrote:Birchoff your links are shortened by forum autocorrect. You have to put them in [url] tags.
Thanks, I will do that next time.

RERT
Posts: 121
Joined: Mon Jun 02, 2014 9:10 pm

Re: EM Drive

Post by RERT »

Although there is massive cause for scepticism on these results, it's amusing to do some arithmetic on what it might mean if true.

5mN per kW combined with 2kW/kg, gives an acceleration of 10^-2 ms^-2. That's about 10^-3 light years per year per year.

On a simple newtonian calculation, accelerating for 63 years gets you 0.5*a*t^2, or 2 light years. You arrive at Alpha Centauri,
at rest, after 126 years. Too long for humans, but interesting for a 'survey' probe. If the thrust efficiency rose to 50mN/kW, it
gets there in 40 years.A barely feasible human mission of 13 years requires 500mN/kW or a higher specific power.

Can the fuel last that long? It is't immediately infeasible, unless the conversion efficiency from mass-energy deficit to electricity
is down in the 1% range. Interested to hear what the forum members think about this.

Interestingly, the LM skunkworks '100MW on the back of a truck' must be in the ball park of 1MW/T or 1kW/Kg, so roughly what's required.

Interested to hear if anybody else here has done similar sums.

birchoff
Posts: 200
Joined: Sun Jul 27, 2014 7:11 pm

Re: EM Drive

Post by birchoff »

RERT wrote:Although there is massive cause for scepticism on these results, it's amusing to do some arithmetic on what it might mean if true.

5mN per kW combined with 2kW/kg, gives an acceleration of 10^-2 ms^-2. That's about 10^-3 light years per year per year.
If we assume this might actually be true, you should start with 0.4N per KWe

DeltaV
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Re: EM Drive

Post by DeltaV »


GIThruster
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Re: EM Drive

Post by GIThruster »

RERT wrote:5mN per kW combined with 2kW/kg, gives an acceleration of 10^-2 ms^-2.
Pretty sure the 2kW/kg is unrealistic in the extreme, and you need the thrust/mass measurement to do this calc correctly, not the power/mass. Power/mass is for the power generation system, and IIRC, not even the most cutting edge space fission reactors have FOM's like this.

Remember, for the kind of calc you want to do, you need to combine the mass of the propulsion and the power generation, and then add on some suitable mass fraction for a craft's utility, then you can do this calc above. The EM type resonators do have a very low mass/power input, because they're mostly empty volume, but their thrust/power and thrust/mass are still below what is necessary for an enabling technology. It is the proof of science issue that it should work at all that is interesting. The proof of technology figures are just not there and cannot be until this is scaled massively.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Carl White
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Joined: Mon Aug 24, 2009 10:44 pm

Re: EM Drive

Post by Carl White »

RERT wrote:Although there is massive cause for scepticism on these results, it's amusing to do some arithmetic on what it might mean if true.

5mN per kW combined with 2kW/kg, gives an acceleration of 10^-2 ms^-2. That's about 10^-3 light years per year per year.
I don't think this is how it (supposedly) works. Although it might generate a certain level of thrust while at rest (e.g. while hovering above the ground and counteracting gravity), the thrust quickly drops off as acceleration increases.

Also, does acceleration at a right angle to the vector of the device's thrust have any effect on it? Not clear (to me at least). If it doesn't, maybe we're back to GoatGuy's wheel of infinite power generation with this device.

birchoff
Posts: 200
Joined: Sun Jul 27, 2014 7:11 pm

Re: EM Drive

Post by birchoff »

Carl White wrote:
RERT wrote:Although there is massive cause for scepticism on these results, it's amusing to do some arithmetic on what it might mean if true.

5mN per kW combined with 2kW/kg, gives an acceleration of 10^-2 ms^-2. That's about 10^-3 light years per year per year.
I don't think this is how it (supposedly) works. Although it might generate a certain level of thrust while at rest (e.g. while hovering above the ground and counteracting gravity), the thrust quickly drops off as acceleration increases.

Also, does acceleration at a right angle to the vector of the device's thrust have any effect on it? Not clear (to me at least). If it doesn't, maybe we're back to GoatGuy's wheel of infinite power generation with this device.
I believe it depends on what theory ends up being right in the end if the experiments pan out. The thrust quickly dropping while accelerating is shawyers theory for how the device works. According to his revised theory as the device accelerates the EM waves inside the cavity experience a Doppler effect and this changes the frequency of the waves in the cavity; which results in a decrease of the energy built up in the cavity. Now apparently this is less of an issue for the 1st gen cavities that are not cooled to superconducting temperatures as they cannot attain the Q values necessary that would lead to a big enough Doppler effect as a result of the acceleration. Shawyer claims to have designed a 2nd Gen device that would be super cooled and deliver thrust on the order of tens of newtons per kilowatt. He goes into details about the performance characteristics and the cap on acceleration in his IAC 2013 paper.

D Tibbets
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Re: EM Drive

Post by D Tibbets »

A perhaps more detailed experimental description. One red flag is that the test article and a supposed null control both apparently produce thrust... which suggests either the test setup is flawed or the physics is confounding...

http://ntrs.nasa.gov/search.jsp?R=20140006052

Dan Tibbets
To error is human... and I'm very human.

tokamac
Posts: 55
Joined: Wed Nov 04, 2009 2:50 pm

Re: EM Drive

Post by tokamac »

D Tibbets wrote:A perhaps more detailed experimental description. One red flag is that the test article and a supposed null control both apparently produce thrust... which suggests either the test setup is flawed or the physics is confounding...

http://ntrs.nasa.gov/search.jsp?R=20140006052

Dan Tibbets
No, the NASA folks shot themselves in the foot with this unclear NTRS abstract, which is very misleading once you have read the complete paper, as birchoff and I did. Birchoff is right, the paper is only $25 (EDIT: complete paper now available freely here), and now it's very clear that even ArsTechnica only read the NTRS abstract and didn't download the complete paper before writing and publishing their biased article. Very poor journalism.

The fact is (and the NTRS abstract does not explain this): Eagleworks tested one tapered (frustum) cavity, aka Shawyer's EmDrive; and two Cannae drives which are also asymmetric but different resonant cavities. The Cannae drive is said to work on a purported different principle than the EmDrive, according to its inventor Guido Fetta (a net Lorentz force imbalance of electrons upon top vs bottom wall of the cavity). According to this purported working principle, one Cannae drive had radial slots on its rim as required by Fetta in order to produce net thrust, and the second Cannae drive didn't have those slits and was intended to be a "null test device". But the Cannae null test article… also produced net thrust (20 to 40 µN of net thrust depending of the forward or backward direction).

We're talking of net thrust because of course the setup was also tested with a null 50 ohm load connected, in order to cancel the effect from the drives and detect any detect any spurious force due to EM coupling with the whole apparatus (which exists, at 9.6 µN) and this "null" spurious force was evidently subtracted from any thrust signal due to the drives then tested on the pendulum.

So the fact that the Cannae null test article produced a net thrust doesn't imply the experiment was screwed up. It rather showed that the radial slits required by Guido Fetta for propulsion are not the reason for the thrust, and another theoretical explanation is needed. Absolutely no news on the websites, including wikipedia, actually reports correctly this information.

We can go further by pointing another underestimated yet important fact of those NASA experiments: all tests articles (the EmDrive version, the Cannae drive version, and even the Cannae "null test" version) had a dielectric embedded within. This is a hint for a different theoretical explanation involving EM fields, proper acceleration, mass fluctuation and dielectrics. Maybe Mach effects (due to Mach's principle), as supposed by Woodward and Fearn within the GR theory, or within a scalar-tensor theory of gravity according to Minotti. As for Sonny White, he talks about compressible quantum vacuum fluctuations, but there are flaws about this conjecture regarding the thrust magnitude observed.
Last edited by tokamac on Fri Aug 15, 2014 7:36 pm, edited 1 time in total.

RERT
Posts: 121
Joined: Mon Jun 02, 2014 9:10 pm

Re: EM Drive

Post by RERT »

Apropos various remarks:

2 kW/kg was rather arbirary and used to calculate N/kg, aka acceleration. So higher thrust per watt reduces the specific power requirement. Higher thrust/Watt may be entirely sensible, per others comments. Also, do you agree the proposed skunkworks generator is about 1kw/kg? I cross-checked my memory just now, and the plan is definitely 100MW on the back of a truck. They are not being entirely serious if that is planned to be more than 100T. So 1MWe/T or 1kWe/kg looks reasonably sane for a fusion power plant. If it weighed 100T, the payload and fuel would be immaterial. I don't know the specific power of space based fission plants, so have no reason to contradict what you said about their limitations.

DeltaV, with the 'Saucer' photo: I must confess that part of my reaction to my calculation was 'So where are the aliens?' If they are not here, something must be wrong...

Lastly, on the theory part: if the proper acceleration (in the device's rest frame) is not constant, then there goes another law of physics, because the setup would not be relativistically invariant. Still, you lose conservation of momentum, and who knows what comes next.

birchoff
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Re: EM Drive

Post by birchoff »

RERT wrote:Lastly, on the theory part: if the proper acceleration (in the device's rest frame) is not constant, then there goes another law of physics, because the setup would not be relativistically invariant. Still, you lose conservation of momentum, and who knows what comes next.
I think worrying about what laws of phsyics could potentially be broken at this point is premature. Assuming no great conspiracy to waste peoples time and energy what we know so far is

1. Shawyer created a device that seems to be able to create thrust without propellant while using electricity as its energy source.

2. Yang Juan a chinese researcher has published 3 papers postulating a model for how the device works and positive test results.

3. Fetta of Cannae LLC, a private company, built a similar looking device and got positive results

4. NASA EagleWorks tested both the Cannae devices and what appears to be replica of the Shawyers EmDrive, and published a paper detailing positive results for all tested devices.Including the device that Cannae thought would be a null device given their theory of how things work.

All this adds up to is a whole bunch of experiments showing either of the following....

1. Nature doesnt work exactly the way we believe it to work.

2. Shawyer, Yang, Fetta, EagleWorks all made the exact same unknown fundamental mistake in how they tested the devices.

Now I do not know about you but I am personally willing to bet money that (2) above is not the case. Which leaves me with (1) and the only way to proceed from this point on is MORE EXPERIMENTATION whose results and protocols are clearly documented and published. Put the issue of Physics laws being violated on the back burner, and fund more experimentation. Once we get enough experimental data then unleash the Theortical Physicists to do what they do best.


Till then I will say again MORE EXPERIMENTS PLEASE....

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