[extropy-chat] Relativity drive: the end of wings and wheels?

[Keith Henson]

At 06:53 PM 9/8/2006 -0700, you wrote:
>Keith Henson wrote:
> >
> > Reactionless drives *are* perpetual motion machines.  If you can't
> > visualize why I can explain the obvious.
>
>Actually, I can't see this as obvious.  Suppose the reactionless drive
>requires a thermal differential to drive it, and equalizes the thermal
>differential in the process.  How would it necessarily violate the
>second law of thermodynamics in the course of violating conservation of
>momentum?

Thought experiment.  The power you can get out of a moving object is the 
product of speed and force.

So let a vehicle with a reactionless drive on a zero friction bearing 
accelerate to a high enough speed.  Then you lower a wheel and draw enough 
power to run the drive.  Let it go a little faster and you are making 
power.  (This assumes the drive force is invariant to the reference 
frame.)  QED, a reactionless drive is the same thing as a perpetual motion 
machine that *makes* power.

> >> If they told me that microwaves shot out the other end, I'd be far more
> >> willing to believe it.
>
> > I wouldn't.  You have any idea of what a microwave generator with 2 gms of
> > thrust would do to the countryside?
>
>The thought had occurred to me, but as a matter of fact, I didn't know
>off the top of my head.  Also, my statement was just with respect to the
>prospect of producing thrust.  Laying waste to the countryside doesn't
>violate *physical* law.

True, but it would sure make the news.

The article mentioned 2 gms.  That's the wrong unit, but assuming they were 
talking about supporting 2 gms in a 1 g field, that/s about .020 Nt.

For a photon drive, the force is equal to power (in watts)/c or P = .02 x 3 
x 10^8 = 6 x 10^6 watts or 6000 kW.  The heck with it as a reactionless 
drive, I want use it to heat my house!

Keith