[extropy-chat] unidirectional thrust

[Mike Lorrey]

--- Hal Finney <hal at finney.org> wrote:
> I thought Dirk was wrong at first, in fact I had a message all typed
> up, but then I thought.what if I'm wrong?  And then I decided that I
> *was* wrong! I think Dirk's analysis is correct. Let me make it more
> concrete.
> 
> Let's suppose a lifter will work in outer space.  We'll use a
> photovoltaic
> panel and some kind of DC-to-DC pulsed transformer to get the 30 kV
> we need.
> 
> Looking at the first chart on the lifter page at
> <http://jnaudin.free.fr/lifters/data/index.htm>, he can lift about
> 35 grams with Lifter v4.0, for 132.9 Watts.  That's a force of
> .035 kg times 9.8 m/s/s or about .3 Newtons.  A random solar panel,
>
<http://www.wholesalesolar.com/products.folder/module-folder/kyocera/KC167.html>,
> can generate 167 Watts and weighs 16 kg.  We'll add 4 kg for the
> transformer (this is all hand-wavey) and get a 20 kg device that we
> can shoot into space and it will start accelerating all by itself.
> .3 Newtons over 20 kg is about .015 m/s/s acceleration that our
> device will deliver. It's small, but it builds up. After 1 day, it's
> going over a kilometer per second! And velocity increases by a km/s
> every day. Meanwhile we are putting in 132.9 Watts the whole time,
> which is 132.9 J/s times 86400 s/day or 11.5 MJ per day. Well, after
> two days we are at 2 km/s so our kinetic energy is m*v*v/2 or 40
> MJ. But we've only used 2 * 11.5 MJ or 23 MJ. So Dirk is right, we
> are over unity already, even with a primitive lifter like Naudin
> has designed.  And it gets worse every day.

The error you start off with is that you are using the thrust it
demonstrates at atmospheric pressure, using atmosphere as the
dielectric medium. Try first adjusting the thrust to that predicted by
the dielectric value for vacuum. Fix that error and you wind up well
within the realm of mundane sub-unity efficiency.... lets try again.

Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
"Necessity is the plea for every infringement of human freedom.
It is the argument of tyrants; it is the creed of slaves."
                                      -William Pitt (1759-1806) 
Blog: http://intlib.blogspot.com


		
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