[AR] Re: NASA test of quantum vacuum plasma thruster
- From: John Schilling <John.Schilling@xxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 04 Aug 2014 19:10:15 -0700
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 They do not cite a reference to their thrust measurement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
john.schilling@xxxxxxxxxxxxxx
(661) 718-0955
Date: Sun, 03 Aug 2014 07:53:24 -0700
From: Henry Vanderbilt<hvanderbilt@xxxxxxxxxxxxxx>
Subject: [AR] Re: NASA test of quantum vacuum plasma thruster (was "Anyone
G. Harry Stine made a sideline of looking into alleged reactionless
drives. He knew how incredibly useful such a thing would be, he really
wanted some such thing to be practical, so (typical of the man) he was
rigorously skeptical. I went along for the ride on at least one of his
visits, to a local guy who was trying to produce thrust mechanically.
(As usual, strange things happened when you turned the rpm high enough
just before the device flew apart, and as usual, there was no actual
thrust involved.)
Harry was actually very kind and polite in letting the guy know it
wasn't real. Again, typical of the guy.
(Enough reminiscing, cut to the chase.) I recall Harry explaining that
he considered a convincing demo to be: Hang the device on the end of a
pendulum in a vacuum, and demonstrate a repeatable constant displacement
of the pendulum with power on versus power off.
And it occurs to me to add, twenty years later, since presumably power
of some sort is being routed to the device down the pendulum, set things
up so the device can be reoriented relative to the pendulum and power
feed, to distinguish between pendulum displacement due to the device
actually thrusting along some axis, and pendulum displacement due to
some power-on mechanical reaction of the power feed.
Henry
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