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Ash Small

Mon Mar 11 2013, 07:23AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

All that escapes (as far as I'm aware) is heat. In air, this would exite (add energy to) the air molecules in contact with the surfaces. I'd imagine that these excited air molecules would exert the same pressure on all sides, unless some property of the waveguide causes the base of the truncated cone to heat more. (I don't know enough about waveguides to ascertain whether a 'tuned' waveguide could achieve this). Even if this did produce some measurable overall 'force' in air, it would be pretty useless in space.

Cytokine

Mon Mar 11 2013, 05:41PM

Registered Member #10255 Joined: Mon Feb 25 2013, 02:47PM
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I first came upon the report by Shawer in 2006 while researching in the UCL (London) D.M.S Watson library â€“the claims were on the face of it, extraordinary although the mathematical analysis did seem lightweight to say the least. Over the ensuing months more and more voices of dissent were raised â€“especially after Shawerâ€™s claims were repeated verbatim as a serious and credible factual piece in the â€˜New Scientistâ€™ magazine.

Many of us working in science have lamented the inexorable decline of the New Scientist; when I first subscribed in the early 1970s it was an invaluable digest of current scientific progress but over the ensuing years it has become something of a joke in the scientific community; worth picking up to look at the science jobs in the back pages (and of course the wonderful Daedalus). But now Daedalus is no more; just another fading memoryâ€¦.or so I thought until I read the â€˜EM Drive â€˜pieceâ€¦

It was the excellent Author Greg Egan who put forward the most cogent and intellectually reasoned rebuttal of Shawerâ€™s claims.

I quote from an early rebuff by Greg Egan:

"Relativistic conservation of momentum has been understood for a century, and dictates that if nothing emerges from Shawyer's device then its centre of mass will not accelerate. This statement holds true in all reference frames. It is likely that Shawyer has used an approximation somewhere in his calculations that would have been reasonable if he hadn't then multiplied the result by 50,000. The reason physicists value principles such as conservation of momentum is that they act as a reality check against errors of this kind."

Egan later published a rigorous mathematical examination of Shawer's claims that demonstrate they are in error and the device cannot generate thrust in the terms of the report.

Claims of exotic spacedrives fuelled by violations of fundamental physics are, sadly but understandably, about twopence a dozen. The aspect of the affair which Egan found truly disturbing â€” indeed, reprehensible â€” was the way New Scientist glibly provided a â€œnewsâ€ piece full of pseudoscientific gibberish purely to justify how the EmDrive might work. (Their argument really pushed the limits of the absurd, too: Einsteinâ€™s relativity has momentum conservation built into its mathematical structure, so you canâ€™t use relativity jargon like â€œreference framesâ€ to sidestep the conservation law.)â€™

There is a Chinese paper which claims to have reproduced Shawer's findings (published in'Acta Physica Sinica, 2012, Vol. 61 Issue (11): 110301)

The authors go on to claim to have observed a force reading of up to750mN with a â€˜Shawerâ€™ resonant cavity being driven with a 2.5KW magnetron. The relationship between thrust and input power is however, not linear which the authors attempt to explain by examining the energy spectrum from the magnetron versus input power. They show that the microwave resonator has a rather sharp resonance maxima at 2.45 GHz and that their magnetron spectral output varies at different power inputs which they claim explains the non-linear thrust readings.

The report is however, frustratingly lightweight (almost anecdotal) and the fact that the authors take as their starting point the assumption that Shawerâ€™s mathematical analysis is valid does cast a serious and probably fatal shadow over the veracity of the work.
That said, it is undeniable that the claims made by the authors (Yang, Ma et al) are seductive (perhaps dangerously so) to those who want to believeâ€¦.

]yang-juan-paper-2012-2.pdf[/file]

Mattski

Wed Mar 13 2013, 03:27AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

2Spoons wrote ...

I would be interested to see the Cullen paper - do you have a ref? I'd also like to know where the error in application was.

2Spoons see my first post in this thread, basically Shawyer only considered the two ends of the resonator while ignoring the tapered connection between them in his analysis. Shawyer's derivation of the force is based on CULLEN A.L. â€˜Absolute Power Measurements at Microwave
Frequenciesâ€™ IEE Proceedings Vol 99 Part IV 1952 P.100 (subscription probably required), as cited in by Shawyer in

Conundrum

Sat Feb 28 2015, 10:50AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Intriguingly a superconducting cavity has many times higher Q and NASA actually tested this determining the increase in thrust in pulsed mode to be many times the value for an identical cavity at room temperature.

It would be a worthwhile experiment to combine three different ideas: infrared "room temperature" effects in YBCO, a cavity cooled only down to 250K and a fully solid state microwave generator.
If thrust only occurs when all three factors are present (ie microwaves on, IR pulsed AND the system is cooled and in resonance it is pretty obviously working.

BigBad

Sat Feb 28 2015, 09:02PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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If they could get this to work, then it's a perpetual motion machine, whether it's microwaves or superconducting or whatever.

and that's not the way to bet.

Conundrum

Sun Mar 01 2015, 04:46AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

I had a look at this and the lift remains constant as long as you don't accelerate or increase in height so this is closer to a maglev platform.

NASA were right to test it as it provides a very valuable insight into GR/SR and it is possible that pulsing it (to prevent heating of the cavity) would be a way to keep satellites in position with less fuel usage.
The waste LN2 would be vented into space so technically it wouldn't be reactionless.
Also energy is still being expended to form the microwave standing wave in the cavity which is not efficient.

BigBad

Sun Mar 01 2015, 06:04PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Conundrum wrote ...

I had a look at this and the lift remains constant as long as you don't accelerate or increase in height so this is closer to a maglev platform.

In fact it's better than that, the lift remains constant even if you do accelerate.

Because the constant is: 0

Conundrum

Fri Mar 06 2015, 06:28AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Using an accelerometer for feedback would also keep it in resonance.

BigBad

Fri Mar 06 2015, 08:16PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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There's been no reliable reproduction of Shawyer's claims at all, and his theoretical analysis has major flaws.

The NASA team showed only a miniscule effect near the limit they could measure, the Chinese team showed a much bigger effect, but that wasn't reproduced by NASA.

Shawyer reported that there was no thrust for a little while when the equipment was turned on; this is inexplicable if the photons in the cavity causes the thrust- in would be instant.

Everything points to this being pathological science.

Conundrum

Sat Mar 07 2015, 09:17AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

I'm trying to build a 2nd gen device with assistance from McCulloch et al, we will see what it does.

-A

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