Subject: Re: [extropy-chat] unidirectional thrust

From: [email-masked] ("Hal Finney")
Date: Fri, 11 Mar 2005 14:28:06 -0800 (PST)

Personally I'm a big fan of conservation of momentum.  I don't see
any way these devices can work unless they are pushing on air or some
other material medium.  I can't see a role for Mach's Principle or any
other exotic relativistic physics.  Is something moving at relativistic
speeds here?  I don't see it.

I have to admit that I'm surprised that NASA has patented this.  The only
thing I can imagine is that maybe it could be used in low earth orbit,
where the vacuum is not completely hard and there is some ambient
ionized gas which could be used for thrust.  Maybe this device could
provide extremely low thrusts over a long period of time, sufficient
for station keeping and stabilization.

As far as Naudin's experiments at
http://jlnlabs.imars.com/lifters/act/html/omptv1.htm , that is
nice work but he doesn't rule out air thrust.  What I would like
to see is the experiment done with something enclosing each of
the thrusters.  That would rule out ion wind.  He has another page,
http://jlnlabs.imars.com/lifters/html/lifteriw.htm using a different
thruster design, where he uses a bag to enclose a lifter but still finds
that its weight decreases when he turns on the power.  The problem there
is that there is considerable material in the vicinity of the lifter,
the balance and such, and it's possible there are some induced electric
effects in that equipment that could distort the results.  If he put
baggies around his thrusters and kept them well off the table and
away from other structures, that would be a good test.  I'll bet they
wouldn't turn.  Do you think Naudin would publish such a result?

With regard to http://www.geocities.com/ekpworld/doc/EKP_satellite_maneuvering.doc ,
it's not clear how good Stein's experimental techniques are so I don't see
how this can be regarded as conclusively ruling out air thrust.  If you
read the paper closely you will see that he did in fact do experiments in
a hard vacuum and still got thrust, although of 0.31 mN compared to 2.38
mN in air.  He had calculated that he could only get 3e-4 mN in vacuum,
so this was supposed to show that it was not air thrust.

But this result is suspicious, because he supposedly measured it at
1e-5 torr, which is like 1 100-millionth of atmospheric pressure.
Yet in these two lifter experiments,
http://www-personal.umich.edu/~reginald/liftvac.html and
http://www.t-spark.de/t-spark/t-sparke/liftere.htm , by two different
people, they could not get lifting below about 70% of atmospheric
pressure.  They attributed the difficulty to ionization and sparking, but
for whatever the reason, the lifters didn't lift when deprived of air.
And the first study found that as they dropped from 100% down to 70%
air pressure, that the necessary voltage increased, which would also be
consistent with an ion wind theory.  These guys can't decrease pressure
by a factor of 30% and still get lift, yet Stein succeeded at a hundred
million times harder vacuum?  Something isn't right.

I can't help thinking that this is yet another case of the phenomenon
I wrote about recently, where we attempt to think independently and
get sucked into crackpot theories.  Now, you can argue that there's
a social benefit to have people out there, working on the fringes,
who might get lucky and stumble across something.  That's fine, and I
don't necessarily want to discourage that.  But for the person who is
not actually pursuing research, the most sensible course is to look at
what mainstream science says about the issue.  In this case I think it's
clear that 99% of physicists would say that applying 20 kV to a couple
of funny-shaped electrodes is not going to violate Newton's third law
and produce uncompensated thrust.  That's a well explored regime and
not where any kind of exotic physics would be expected.

Hal
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From: Keith Henson <[email-masked]>
Date: Mon, 14 Mar 2005 18:19:36 -0500

At 02:28 PM 11/03/05 -0800, Hal Finney wrote:

>Personally I'm a big fan of conservation of momentum.

snip

Me too.  Also conservation of energy.

And unidirectional thrust, if it is not velocity dependent (and reference 
frames are supposed to all be the same) can be shown to violate the 
conservation of energy by a simple thought experiment.

Just suspend the gadget at the end of a long arm in a vacuum, let it 
accelerate to some arbitrary velocity such that you can lower a wheel with 
a generator (or tap the hub of the suspension system) and make more power 
than it takes to generate the thrust.

I am not opposed to unidirectional thrust devices, would love to see one 
(bought the Dean Drive patent from the PO when I was in high school) but 
folks really should be aware that it isn't just conservation of momentum 
that gets lost if you can make one.

Keith Henson