----- Original Message -----
From: John Berry
To: vortex-l@eskimo.com
Sent: Friday, September 15, 2006 6:27 AM
Subject: Re: [Vo]: stationary emdrive- inertial anchor
What you should note is that this device if it works at all MUST violate
the conservation of energy, there is no way round it, if you use it to
accelerate or row for >10 seconds and it accelerated it to 1 meter a second
using .5KWh say, then if you run it for 20 seconds you'd have used 1KWh,
have 2 meters a second velocity >but the energy contained in forward
movement of your ship is 4 times that of running the engines for the 10
seconds.
No.
Assume a 1000kg spacecraft at initially velocity 0m/s. (we will ignore the
"relatives" here for now, more on this later)
Assume that this spacecraft uses its reactionless propulsion system
(whatever it may be) to accelerate to approximately v=0.1c, or 29,979,246
m/s. We will ignore relativistic effects at this time. The energy require to
get to this velocity will be K = 1/2 m v^2, or in this case, 4.494x10^17J.
Not a small amount. But what is the energy required then to accelerate the
craft to only v=0.05c? 1.123x10^17J, or 25% of that required to reach 0.1c.
Now of course this makes sense, the square of velocity and all that. What it
also indicates is that to go from v=0c to v=0.1c you must use increasing
energy as time goes by. If you use a constant energy per unit time (I am
using only basic units here to avoid confusion) you will find your
acceleration tapers off rapidly as velocity is increased.
So, if you use say (changing from kWh to something that is easier to follow,
kW) 0.5kW for 10 seconds, on a 10,000kg object, the kinetic energy gained by
the object is 5kJ, and our object is moving at a gentle 1m/s. This of course
assumes that your method of converting electrical energy input to kinetic
energy is 100% efficient.
But...if we apply 0.5kW for 20 seconds, we have added 10kJ to our 10,000kg
object, and its velocity is now...only 1.414m/sec. Can you get to 0.1c with
a constant-power drive? Absolutely, but it will take much longer to get
there, and efficiency will drop as speed increases, and fall rapidly the
faster you try to go. If on the other hand, you use a constant-acceleration
approach, you get there (to your desired speed) much faster, but you use an
ever increasing amount of power. The total energy to reach 0.1c for
constant-power or constant-acceleration is the same.
Now here's something interesting. If drive efficiency in attaining some
velocity from some given energy input decreases like this over time, as
velocity builds up, it would seem to imply that an absolute velocity is
important. A very big no-no when it comes to relativity as we know it. (or
as we like to know it)
You can have a reactionless drive which conserves energy globally, but to do
this it will demonstrate some rather odd effects (at first glance) which
later once you have juggled it in your mind for a while, really don't end up
so confusing in the end. But it does seem to lead to one reference frame
being preferred, and acting as the "road" for your hypothesized "space car".
If a reactionless drive is constructed successfully, one wonders about its
uses to test relativity in a new and unique way. I'll let you think on that
for a bit.
--Kyle
