[extropy-chat] unidirectional thrust

[Mike Lorrey]

--- Hal Finney <hal at finney.org> wrote:
> 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.

These numbers are from research done under USAF contract and mentioned
in Cravens study. This equation is for vacuum. Naudins numbers are all
at 1 atm. The study he cites a thrust that is for a low pressure, but
not a vacumm. I am not sure what thruster configuration this pertains
to though.

> 
> 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. 

You have a good point there, but it isn't a point that doesn't cause
problems also for a Bussard Ramjet, worse yet because the ramjet
performs better at higher velocity. As Cravens noted, you can't talk
about 'conservation of momentum' with a field thruster like this if it
is thrusting against the entire universes inertial frame, because you
have no external point of reference to base such a judgement on. The
best you can do is divvy the KE in half, because the universe is being
pushed equally in the opposite direction, a division that generally
isn't used with rocket engines because it is only accelerating a small
amount of mass and where the observer isn't part of the equation. When
you do that, your actual KE drops below the power put in, and
conservation does in fact exist.

WRT this device, the problem we run into is that we've never tested it
at ANY sort of velocity but a lab test bench, so there is not any sort
of sufficient experimental database upon which to even extrapolate what
sort of attenuation law might apply in higher velocity ranges. Until
that happens, making arguments like yours to justify dismissing this
technology are tantamount to excuses why heavier-than-air flight was
impossible prior to the wright brothers.


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


		
__________________________________ 
Do you Yahoo!? 
Yahoo! Small Business - Try our new resources site!
http://smallbusiness.yahoo.com/resources/