On 4 August 2014 16:54, Peter Fairbrother <zenadsl6186@xxxxxxxxx
<mailto:zenadsl6186@xxxxxxxxx>> wrote:
Suppose, as has been claimed, the drive is somehow exchanging
momentum with the entire universe. The momentum of the universe may
have a (?local) velocity - which would be mathematically equivalent
to a preferred frame of reference.
If so, there need be no violation of either of the conservation laws.
Even that wouldn't be of any practical use for propulsion.
There's basically zero chance that you would moving close the preferred
frame of reference's speed. And if you're not.. .big trouble in little
china.
To see this, consider that we're already going at (say) >300km/s due to
orbital speed, the speed of the Sun within the local cluster and the
orbital speed around the Milky Way, and the speed of the Milky Way
relative to other galaxies... so it takes enormous energy to make quite
modest increases in speed because energy goes as 0.5 m V^2.
i.e.
E = 0.5 m V^2
where V is the speed in the preferred frame of reference.
differentiating wrt time:
P = m V dV/dt
dv/dt = P/mV
so acceleration for any given power is inversely proportional to initial
speed. That's the same reason cars accelerate very fast initially, and
then accelerates ever more slowly. But here you would be going at
extreme speeds to start with. Rockets and ion drives circumvent this due
to Oberth effect and get constant acceleration from constant power.
Plugging in numbers here it would cost 300kW to accelerate 1kg by 1m/s^2
which is insanely inefficient.