EM Drive

[Diogenes]

A Wired article about the EM Drive has appeared:

http://www.wired.co.uk/news/archive/201 ... old-fusion

The Chinese group reports achieving about 720 mN of thrust at a power level of about two kilowatts.

The wired article does not say this. It says it could be 720 mN with a couple of kilowatts of power, which leaves it rather ambiguous as to whether or not they actually achieved this. The Translated paper does appear to say they achieved 750 mN of thrust with a power of 2500 watts.

(I assume they are using the "m" to represent "micro" rather than "milli".)


If this is true, this is very interesting. It is, by far, a simpler method of generating thrust than is the Woodward devices, and it appears they are getting much stronger thrusts.

It says there may (again, may) be a demonstration at an aerospace conference this year.

It points to the translated paper already mentioned by DeltaV:

http://www.emdrive.com/yang-juan-paper-2012.pdf

It will be interesting to see if this is replicated elsewhere. A claimed positive result ought to encourage duplication.

[Carl White]

The Chinese group reports achieving about 720 mN of thrust at a power level of about two kilowatts.

The wired article does not say this.

Directly from the article:

The latest paper describes their latest thruster and gives the test results in details, showing that with a couple of kilowatts of power they can produce 720 mN (about 72 grams) of thrust.

So the article does say this. But the article doesn't reflect precisely what the paper says (i.e. there's no point on any of the paper's graphs which shows a force of 720 mN being generated with an input of 2.0 kilowatts), that's true.

[Diogenes]

The Chinese group reports achieving about 720 mN of thrust at a power level of about two kilowatts.

The wired article does not say this.

Directly from the article:

The latest paper describes their latest thruster and gives the test results in details, showing that with a couple of kilowatts of power they can produce 720 mN (about 72 grams) of thrust.

Semantics. The way I read it "showing that with a couple of kilowatts of power they CAN produce 720 mN". Had they said "it did" I wouldn't regard it as ambiguous. It's a minor quibble and I don't fault you for reading it the other way.

So the article does say this. But the article doesn't reflect precisely what the paper says (i.e. there's no point on any of the paper's graphs which shows a force of 720 mN being generated with an input of 2.0 kilowatts), that's true.

I saw it in the text of the article.

After the increase in output power, thrust increases, and
with the maximum output power of 2500W, the maximum thrust reaches around 750mN.

At this point I am not terribly concerned what is the actual thrust vs power, i'm more interested that they claim to have an effect strong enough to be distinguishable from noise.

[paperburn1]

At this point I am not terribly concerned what is the actual thrust vs power, i'm more interested that they claim to have an effect strong enough to be distinguishable from noise.

Yes that is the working end of the horse, but I have seen reports like this from China and they ended up amounting to be only a effort to misdirect research and funding.

[Diogenes]

At this point I am not terribly concerned what is the actual thrust vs power, i'm more interested that they claim to have an effect strong enough to be distinguishable from noise.

Yes that is the working end of the horse, but I have seen reports like this from China and they ended up amounting to be only a effort to misdirect research and funding.

This is a issue with me as well. I find it odd that Chinese scientists (Working for a government not known for it's Honesty) confirm the effect, but others haven't.


I'm willing to give them the benefit of the doubt, but I'm not closing the door on the notion that they are lying until I see more proof.

[tokamac]

I don't understand all this "I'll believe it when it's above the noise" scheme.
Jim Woodward has results in the ten micronewton range with his Mach Effect Thrusters, and some scientists ask for repeatable experiments orders of magnitude higher in the millinewton range just to be sure "to be above the noise".

We don't need to wait for "above the noise" results because doing so we'll always get the same answer whatever the results, unless someone shows a propellantless flying car out of their garage. We need tiny CubeSat experiments launched from ISS to prove or disprove those technologies.

720 mN @ 2.5 kW is huge. It's a specific thrust of about 300 mN/kW.
As compared to Woodward thrust-to-power ratio of 0.01 to 0.02 mN/kW achieved so far.

Take a look at their curve (PDF version available here):


This curve is from 2010 experiments, and was published in the Chinese peer-reviewed paper in 2012, which has been translated in English since then and is available on Shawyer's site:
Yang, Juan et al. (2012): Net thrust measurement of propellantless microwave thrusters. Acta Physica Sinica, Vol. 61, Issue 11.

[GIThruster]

As compared to Woodward thrust-to-power ratio of 0.01 to 0.02 mN/kW achieved so far.

I believe Jim's record is 10mN and he never dissipates more than about a watt, so he is way, way, way past what you're talking about.

The problem with the Swayer work is that it has lots of high power RF flying around and we don't know anything about the test apparatus. We do know that the test apparatus in the UK was eventually blamed for the false thrust signal and the same at Eagleworks when they did this stuff--coupling to the stainless vacuum chamber.

Just IMHO, but it looks to me this is all another CIA counterintel gambit. I'm sure our spooks are laughing thier asses off at the Chinese for so wasting their time.

[tokamac]

Have a look at the EmDrive article on Wikipedia, it has been improved a lot

[DeltaV]

Some guy named Guido wants to sell you "the world's first reactionless drive", but I can't get the videos to play or the theory/data links to work...

http://www.cannae.com/

[GIThruster]

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.

[tokamac]

Amazing to me folks still don't get that this violates' conservation.

In terms of classical electromagnetism, yes. Even with the bits of special relativity added by Roger Shawyer. But the thrust produced by resonant EM cavities does not violate the laws of conservation of momentum and energy if the theory proposed by physicist Fernando Minotti is at work. The theory is falsifiable. For example, it predicts thrust reversal for certain specific resonant frequencies. Minotti's paper has been published in 2013 and is available on arXiv:

• Minotti, F. O. (July 2013). "Scalar-tensor theories and asymmetric resonant cavities". Gravitation and Cosmology 19 (3): 201. arXiv:1302.5690.

For the case of resonant cavities, the scalar-tensor theory of Mbelek and Lachièze-Rey (of the Brans-Dicke type), cited in Minotti's paper, behaves as standard GR with a negative energy source, thus allowing a reactionless drive possible, as in Alcubierre's warped space-time. Physicists Francisco Lobo and Matt Visser were the first to note it in their 2004 paper:

• Lobo, F.S.N.; Visser, M. (December 2004). "Fundamental limitations on "warp drive" spacetimes". Classical and Quantum Gravity 21 (24) 5871–5892. arXiv:gr-qc/0406083

The work of Lobo and Visser is the third most important work in warp drive physics after the works of Miguel Alcubierre in 1994 and José Natário in 2002.

[tokamac]

GIThruster, I think you may be interested in Brans-Dicke theory, as it involves Mach's principle and relies on the scalar potential Φ also used by Sciama, that is at the root of Woodward's Mach Effect Thruster that I know you're interested in.

The founding paper:
• Brans, C. H.; Dicke, R. H. (1 November 1961). "Mach's Principle and a Relativistic Theory of Gravitation". Physical Review 124 (3): 925–935. doi:10.1103/PhysRev.124.925.

And another interesting document by Carl Brans, historically explaining the roots of the theory:
• Brans, C. H. (10 June 2005). "The roots of scalar-tensor theory: an approximate history". arXiv:gr-qc/0506063

[GIThruster]

Yes, I've read quite a bit of Brans actually. Woodward quotes him fairly often as to several in the anthology on Mach's Principle, wich is still one of the best sources I've found on the subject:

http://www.amazon.com/Machs-Principle-N ... 0817638237

If Minotti is evoking negative mass in the Shawyer resonator, then perhaps that would avoid the conservation violation, but I am unfamiliar with how it could generate negative mass. Too I would point out that Shawyer received government support from the Brits for something like a decade despite his theory violates conservation, and after a decade of no results, he moved on. Both Sonny White down at JSC and the Chinese have since been trying to get the thing to work, and it does not work. So with broken theory and no empirical results, why would anyone evoke negative mass to say the thing works?

[tokamac]

I do not have the same analysis on the data available.

I would point out that Shawyer received government support from the Brits for something like a decade despite his theory violates conservation, and after a decade of no results, he moved on.

Over the years Shawyer reported positive results for several experiments, from 16 mN in 2003 to 174 mN in 2008, using different copper and brass resonant cavities. And now I don't think he has moved on: according to the latest news he will present a technical paper on 2nd gen (aka superconducting) EmDrives at IAC 2014 that will be held in Toronto, Canada in September. I don't know if he will give any insight about new experimental results or if he'll just present another numerical simulation. The later would be a bad sign IMHO.

Both Sonny White down at JSC and the Chinese have since been trying to get the thing to work, and it does not work. So with broken theory and no empirical results, why would anyone evoke negative mass to say the thing works?

Chinese researchers do measure net thrusts in their experiments, they do not get null results: 720 mN of thrust @ 2.5 kW in 2010. So what's the point of saying "they tried to get the thing to work and it does not work"? I can't believe you're writing this if you read the papers. After Shawyer's, it was Chinese positive results which precisely motivated Minotti to investigate into the resonant cavities, as he clearly states in his 2013 paper.

As for Eagleworks, I don't know. Results are unpublished and are still going on apparently. As far as I understand, until now they used only little RF power amplifiers of very limited power, instead of more powerful magnetrons, klystrons or TWTAs that should feed such devices. They have to upgrade their equipment.

[GIThruster]

I was not familiar with a Chinese success. It will be interesting to see what we see.

I wasn't referring to Eagle's recent work. I was referring to Sonny and Paul's work several years before there was an Eagleworks. To the best of my knowledge however, Eagle has not had any positive results that did not vanish when the coupling problem was solved, part from those generated by the switching transients with the QVT work. That is explained by Woodward's theory, not the QVF model.