At 02:42 PM 11/5/2009, Horace Heffner wrote:
Abd,
It appears you may be crossing over into the realm of pathological
skepticism, pathological debunking, ...
Pathological? Moi?
http://www.youtube.com/watch?v=57q3_aRiUXs&fmt=18
This is the big demonstration. And what does it show? *Rotation*.
Roughly, it looks like the entire assembly, what's bolted together,
is rotating about its center of mass. So they are *calculating*
"thrust" by assuming the rotation is produced by thrust from the
cavity. But the cavity is not a closed system, it's being fed energy
from the magnetron. We have to consider the whole system for
conservation of momentum, not just half of it.
If the rotary motion were produced by a constant thrust during the
one minute of this video, we would see acceleration over the whole
minute. Instead, the device appears stationary, then slowly starts to
move, reaches a (low) speed, and then seems to move with constant
angular velocity. Was this caused by the pump starting up? That's
pretty much what it would look like. In fact;
"When the power is turned off, at 210
secs, there is a coast period as the slosh effects
of 5kg of coolant maintain a reduced
acceleration."
http://www.emdrive.com/IAC-08-C4-4-7.pdf
This is from page 8 of the article. The acceleration (increase in
angular velocity) continues after the power is shut off! It's
attributed to "slosh effects." Which means that this weight of
coolant moving around is significant. When was the coolant pump
turned on? The cavity comes into resonance at t = 130 sec. They say
that the acceleration begins then. However, the drop into lock is
rapid, practically instantaneous. The assembly starts to rotate
*before* that time, at t = 125 sec.
The power is shut off at 210 seconds, but the acceleration continues
at a steady rate (increasing angular velocity) for another 45
seconds, with then sudden deacceleration, increasing in rate until
the device stops. I'd think that friction would be proportional to
velocity, but this looks like something else is happening. There is
no slowing of deacceleration as the thing approaches zero velocity,
instead, the rate of change of velocity increases. It makes no sense.
This is supposed to be a convincing demonstration?
I'm starting to make a kind of sense out of Shawyer's explanations,
though. A weird sense.
He's treating group velocity as if the pressure on the plate would be
dependent on group velocity, and I don't think that's correct at all.
Group velocity is an appearance, and it can exceed the speed of
light. It's a pattern, not a force as such (and there is no way to
send information with that group velocity).
He also seems to be thinking of a rest frame that the electromagnetic
waves are travelling in, which is why he claims that thrust is
reduced as the object increases in velocity. Suppose we imagine a big
curtain around this thing, the people in this "spacecraft" can't see
the external world. But, of course, if the emdrive is accelerating
them, they will experience the acceleration, same as gravity. If the
emdrive is being powered on-board, if its operating conditions remain
constant but the thrust changes with velocity (in some external
frame), then they would be able to measure the difference in the
"gravity," and from that deduce their velocity outside, with no
external observations. Shawyer is assuming an absolute frame of
reference, the one that defines the "velocity" of the spacecraft. He
talks about relativity and uses relativistic equations in his
explanations, but he's basically denying it. Along with conservation
of momentum and a whole lot of common sense.
