[extropy-chat] unidirectional thrust

[Hal Finney]

Mike Lorrey writes:
> Fine, now use the same equations to show how a Bussard Ramjet is also
> over unity by your definition.

Let's not get distracted.  The issue is not a Bussard Ramjet, it is
whether a space drive which produces a certain acceleration for a certain
power level violates conservation of energy.  Please stay focused!  (I do
know why the ramjet is different, but I won't get sucked into that topic.)

> Other errors: you are applying fixed DC when you need to convert that
> to pulsed DC and correct for phase angle of the capacitor on the power
> factor.

I'm using the power figures from the top chart at
<http://jnaudin.free.fr/lifters/data/index.htm>.  That is his measured
power and should take into consideration the phase differences.  And those
figures are with straight DC.  Later on the page he claims that pulsed
DC produces 4 times greater thrust!  But I was conservative and didn't
assume that.  With a higher thrust we just go over unity even faster.
Time to over-unity is inversely proportional to acceleration squared,
as a matter of fact.  With 4 times greater thrust it would happen in
15 days rather than 60.

> Try these equations:
> F= 3.55x10^-8 V^0.722
> where F is newtons and V is kilovolts

Where the heck does that equation come from?  Do you realize that to
produce a force of 0.3 Newtons, as Naudin measured in his lab (see
the link above, raising 35 grams takes 0.3 Newtons), you'd need V =
4 billion?!  If V is kilovolts then we're talking about 4 teravolts to
power Naudin's lifter.  You're off by 8 orders of magnitude.

Notice that I didn't pull figures out of a hat for my analysis.
I showed exactly where they came from - the thrust in air from Naudin,
and the derating for vacuum from Stein, both references that you cited.
Now you come up with some numbers and some formulas from out of nowhere.
Why should I trust those figures rather than ones that at least some
experimenters claim to have observed?  Your formula doesn't even make
sense.

> figure on a thrust to power ratio of 0.00025 newton per applied watt
> (not the same as solar panel watt, as turning 12 vdc into 10kv 70 hz
> pulsed dc or higher is not quite so easy, plus you need to deal with
> the phase angle).

That's close to what I assumed.  My analysis was for a thrust of 0.039 N
with 132.9 Watts, which is .00030 newtons per watt.  I built some leeway
in with the solar panel,
<http://www.wholesalesolar.com/products.folder/module-folder/kyocera/KC167.html>
which can produce 167 Watts.  That can cover some inefficiency in the
power conversion.

But so what if you maybe need twice as big a solar panel?  We can easily
assume that technology will soon let us make a solar panel that weighs a
lot less than 50 pounds, so we're right back to the same acceleration.
You can't base your objection on little factors of 2 or 3.  That's not
going to change the fundamental problem, which is that kinetic energy
increases as the square of time.  And that's in the low-energy realm;
if you look at my relativistic analysis, KE is proportional to cosh(t)
which is asymptotically e^t as you get into the relativistic regime.
So things are even worse then; instead of KE as the square of time, it
goes as the exponential of time, with constant thrust.  Meanwhile energy
in is linear with time.  No matter how you tweak the numbers, square
wins over linear eventually, and exponential wins over both.  You'll
always go over unity eventually.

Hal