Re: On reactionless drives

Adrian Hurt writes:
>I think what Bertil was trying to say is, what is wrong with turning a ship
>from having X megajoules of energy stored as potential energy, to a ship
>having .9 X megajoules of kinetic energy and .1 X megajoules of waste energy
>(e.g. heat) without having to dump a load of stuff out of the back to satisfy
>Newton?  This doesn't create energy out of nothing, and doesn't violate
>conservation of energy.   ^^^^^^^^^^^^^^^

Yes it does.  I posted a detailed example showing why recently.  Even if you
use Bertil's idea of  (Energy needed for drive = KE added to ship) it doesn't
work because you need a non-accelerating reference frame to measure KE.

Example: Suppose you have your ship between planets A and B, which
are moving with respect to one another.  We now have to choose a frame
of reference, say A.  Say the velocity of B with respect to A is 1e3 m/s.
The KE of ship relative to A is 0, and relative to B is 5e5*M joules.
The ship now accelerates to 1e3 m/s relative to A, in the direction
opposite to B's motion.  Now the KE of the ship relative to A is K1 =
5e5*M joules, where M is the mass of the ship, so we expend
(K1 + waste) joules to power the drive.  However our velocity relative
to B is now 2e3 m/s, giving a KE of K2 = 2e6*M joules, which
is an increase of 1.5e6*M joules, creating 1e6 joules of "free" energy
with respect to B.  With a rocket, that energy wouldn't appear since
is has to spend energy to accelerate the reaction mass and it masses
less afterwards.

I worked all out with a friend for fun when we were building MT
perpetual motion machines. (So I'm weird - sue me)

					W. Dow Rieder

 	When the only tool you have is a hammer, all your problems
start to look like nails...