At 12:51 AM 11/4/2009, Horace Heffner wrote:
I didn't make the claims. See:
http://www.emdrive.com/theorypaper9-4.pdf
for the theory,
http://www.emdrive.com/
for the company.
They show a curve of acceleration vs velocity. It has nothing to do
with anything external. Therefore I think it is bogus. I've done
enough work in this area to believe it is possible to couple to
vacuum inertia though, and that means the possibility of reactionless
EM drives.
I think it's more than bogus, I think it's a deliberate hoax, a
spoof, a jape. Very cool, actually. And the movement of that
experimental device in the video could be explained by just about
anything, looks like they suspended it somehow, so that it would
become very sensitive to any forces, which might come from
interaction with the earth's magnetic field, or some other effect,
and if someone wants to claim interaction with "vacuum inertia,"
that's fine with me. But inertia implies a velocity being maintained,
so what's the velocity of the vacuum? What's the vector?
The explanation in the theory paper looks completely fallacious to
me. They have two forces resulting from radiation pressure. By a
slight of hand, they make it look like the force in one direction is
more than the force in the other direction. I.e., they assume what
appears to be a constant radiation pressure per unit area on the two
sides of the cavity, with the larger force being exerted on the
larger end plate. Of course. But they have neglected the connecting
walls. Suppose this were a gas instead of microwaves being reflected
back and forth. The force exerted by the gas on the larger plate
would exceed the force exerted on the smaller plate. But what about
the sides? They are not straight, and the pressure against them would
have a net value of a force in the downward direction, such that the
net force in both directions, acting on the entire assembly, is zero.
Essentially, if we look at a total area as seen from above and a
total area as seen from below, those areas are the same, so the
pressure up is the same as the pressure below, and that's true for a
view of any closed cell from any direction. If you open up one side,
the radiation pressure for the opening will go to zero, so thrust
would be experienced in the other direction. I wonder if we have two
flashlights in a vacuum both in free fall, no relative velocity to
start, and then we turn on one flashlight, how long would it take
before you could see the relative movement?
To the extent that anyone is taking this seriously, there are some
students laughing so hard they are in danger of something falling off.
