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Ash Small

Sat Mar 07 2015, 01:17PM

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

BigBad wrote ...

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.

Unless the effect is caused by it warming up. See my previous posts

Edit: It's a wave guide. Where are the waves 'guided'?

BigBad

Sat Mar 07 2015, 08:11PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

They're guided into becoming heat.

Yes, the effect is almost as if it's caused by non uniform heating/airflow around the object causing an aerodynamic lift effect.

But that could never be- right?

it has to be something magical!

Daedronus

Mon Mar 09 2015, 09:07AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

BigBad wrote ...

They're guided into becoming heat.

Yes, the effect is almost as if it's caused by non uniform heating/airflow around the object causing an aerodynamic lift effect.

But that could never be- right?

it has to be something magical!

Not in vacuum, not at pressures where radiometer like effect can no longer happen.

Ash Small

Mon Mar 09 2015, 09:46AM

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

Thermodynamics of a black body photon gas

BigBad

Mon Mar 09 2015, 11:15PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

Somebody who was at the NASA conference that announced the NASA result posted this:

"I was actually at that conference; didn't want to comment until I
had a chance to read the paper, but now I have so here goes:

The team appears to have used a standard NASA-Lewis torsion balance
thrust stand. That thrust stand, which I have used extensively, is
good to about +/- 10 microNewtons when used in the steady-state
mode by an expert team. There is a resonant mode (look for a paper
by Lake and Dulligan) that can get down to +/- 1 uN or better, but
that isn't what was used here.

Nor does the team that did this work appear to be thrust-stand
experts. There is relatively little discussion of that aspect of
their work, and what there is suggests that they did some things
right (e.g. comparison to a ballast load to rule out interference
from the power supply) and some things wrong (e.g. only a single-point
calibration). They do not cite a reference to their thrust measurement
technique, they do not give acknowledgement to any of the technicians,
and a quick literature search of their prior work does not suggest
great experience with the NASA-Lewis torsion balance thrust stand.
Absent such expertise, or even the recognition that such expertise
is necessary, errors of several tens of microNewtons are likely and
hundreds of microNewtons are not implausible.

One thing they unambiguously did right, was to test the null-hypothesis
model of their "Cannae" thruster. Theory says that that with the
asymmetric groves you get ~10,000 microNewtons of thrust from 28 Watts
of electric power and without the groves you get zero thrust. They
tested both, on a thrust stand with error bars of a few tens of
microNewtons, and got ~50 microNewtons of indicated thrust.

And made essentially no mention of this ever again, except to say
"We got Thrust! Yay Us!".

Their subsequent testing of the truncated-cone thruster conspicuously
failed to make use of a null-hypothesis model. After repeatedly
showing about the same (lack of) performance as the "Cannae" thruster
in its first two operating modes, they conducted one single test of
the truncated-cone thruster in a third operating mode, demonstrated a
fivefold increase in thrust:power, and found that time and facility
limitations meant they had to terminate the experiments.

Finally, they put forth a batch of conclusions that are entirely
unsupported by their own experimental data. It would have been bad
enough to have reported the single anomalously high truncated-cone
data point as the baseline and buried the null-hypothesis results.
Worse, is reporting only the Chinese experimental results (nearly
two orders of magnitude better than their own) and the theoretical
calculations which they did not perform and did explicitly disclaim
as beyond the scope of their paper, note that theory and experiment
(other people's) indicate a thrust:power ratio of 0.4 N/kW, and
proclaiming, "...and we also measured (mumble) thrust, so it's all
true and we can have manned missions to the outer solar system any
time now!"

They measured experimental error, and nothing more. And they set the
bar so low, with such implied authority, that we can now look forward
to years of dueling claims of "I built an EMdrive out of spare parts
and put it on a thrust stand I had lying around, and got microNewtons
of thrust just like NASA!", "So did I, and I got nothing at all!"
Did so, did not, ad infinitum.

If theory and Chinese experiment really do validate claims of 0.4 N/kW,
then you really can build an enclosed metal box (batteries in the box,
to deal with the power-supply interactions Henry correctly notes) that
will visibly tilt a straight hanging pendulum. Do that, and get back
to us.

Oh, and if you can build a reactionless thruster with a thrust:power
ratio of 0.4 N/kW and can't think of anything better to do with it
than fly to Uranus, you are an insanely myopic space cadet. I will
leave it as an exercise to the student how one would incorporate such
devices into a perpetual motion machine capable of providing clean,
free energy on a massive scale. It isn't trivially easy, but it is
almost certainly worth doing long before you build spaceships - and
this was presented at a "Propulsion and Energy" conference, so it
probably would have been worth mentioning.

Well, except for the fact that the Energy attendees would have been
more merciless in their heckling; there's a long tradition of tolerance
in the "future flight" sessions of the AIAA Propulsion conferences.

John Schilling
**link**
(661) 718-0955"

AndrewM

Tue Mar 10 2015, 10:07PM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

Since two posts have mentioned it obliquely, but I still don't have anything jumping to mind:

Can someone propose a thought experiment whereby a reactionless thurster enables a free energy device?

I didn't think conservation of momentum was an obligate pair of conservation of energy...

BigBad

Wed Mar 11 2015, 05:42AM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

You turn it on multiple times, injecting a fixed amount of energy into it; which presumably makes it accelerate by a fixed amount each time.

If it does; conservation is immediately blown; kinetic is a square law on speed, but here the energy use is linear. BOOM goes the physics.

If it's not adding linearly, then you have big trouble in a different sense. Normal physics obeys Galilean relativity at low speeds, but it turns out this doesn't. If you're moving relative to it at the start, then you when you add up the energy, the books don't balance. It turns out that the books normally do balance, in, for example a rocket, because of conservation of momentum with the exhaust; but that's blown wide open.

It just doesn't work.

Antonio

Wed Mar 11 2015, 01:44PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

The paper ends with "The results are consistent with theoretical calculations". But the paper does not show any calculation.
Just nonsense, or some parasitic effect as heating more air at the large end.

Daedronus

Wed Mar 11 2015, 02:21PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

Antonio wrote ...

The paper ends with "The results are consistent with theor
etical calculations". But the paper does not show any calculation.
Just nonsense, or some parasitic effect as heating more air at the large end.

What air? it was tested in vacuum.
Find some other reason why it won't work.

Antonio

Thu Mar 12 2015, 01:02AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Daedronus wrote ...

What air? it was tested in vacuum.
Find some other reason why it won't work.

All that is known about Physics.

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