D
-
Categories
-
Platforms
-
Content
Boris Mohar said:This thing is RF sealed.
Check the site in more detail, looks legit. But I don't get the underlying principle.
It this thing really working? The force is microscopic, though, but that might not
matter much for the intended purpose.
MooseFET said:You need dilithium crystals to get much power out of it.
JeffM said:That's what I was thinking:
http://www.google.com/search?q=cach...ew.Worsley+concerns+Peter.Twist+Worsley-Twist
![]()
JeffM said:That's what I was thinking:
http://www.google.com/search?q=cach...ew.Worsley+concerns+Peter.Twist+Worsley-Twist
![]()
TheM said:Check the site in more detail, looks legit. But I don't get the underlying principle.
It this thing really working? The force is microscopic, though, but that might not
matter much for the intended purpose.
There has been no definitive independent test of any force produced.
And if this thing does produce constant thrust for a fixed input of
electricity you have an over-unity engine.
Tim said:No, electromagnetic energy carries momentum. Just extremely little of
it.
2450MHz photons carry an energy of E = h*f = 1240 nm.eV * 2.45 GHz / 3
x 10^8 m/s = 1 x 10^-5 eV = 10 ueV and momentum of p = E/c = 3.38 x
10^-14 eV/c. 60 kJ (the equivalent of running your microwave, door
jimmied open, for one minute) thus carries 3.75 x 10^23 eV total
energy or n = 3.75 x 10^28 photons (a good 5 x 10^4 moles or so), or
1.26 x 10^15 eV/c = 6.75 x 10^-13 kg.m/s if I got the units right
(should've started with h in MKS, oh well). To accelerate a dust
particle of 65 ng to a rate of 1 m/s would require about 2.9 GJ of
microwave energy, assuming a massless reflector.
The proposed device evidently reflects microwaves multiple times,
leading to multiple momentum transfers. That's a good approach. But
there can't be any net momentum transfer between the device and its
surroundings, only between its surfaces, which are bolted together and
therefore don't move. Because of this, a little-known relativistic
principle is invoked. I don't know enough about relativity to make
any analysis of that. The fact remains, energy goes in, EM radiation
goes out, and thus only a limited amount of momentum leaves.
Conservation of momentum is one of the things Einstein specifically
preserved in his theory (note that conservation of mass or energy are
both specifically eliminated -- conservation of mass-energy is the new
rule), I think he would be annoyed to see his own work basically
perverted against its own principles.
Now, if the device does, in fact, make as much thrust as is claimed,
it should be pretty easy to find -- it's little more than a
differently-shaped microwave oven with the door open(?), and the
magnitude of the predicted force is easily measured using a torsion
pendulum. I'm mystified why such a garage-scale experiment might take
millions of dollars, even for a rather detailed analysis, construction
and optimization of the apparatus. That in itself might be a good
enough reason to suspect it!
Note that it is possible to use resonant reflection to transfer extra
momentum, but only between a remote reflector and the vehicle. Both
targets recieve equal and opposite momentum, and if the beams are
tightly focused and the reflectors have high Q (heck, if we're in
space I suppose superconducting dishes aren't out of the question),
the efficiency can be quite high, although maybe the power density not
so much (with superconductors, the limiting factor is critical field
strength; for ordinary conductors, power dissipation and overall
efficiency). The vehicle also doesn't have to be itself powered,
although it will be once it's simply too far to keep the beam
together. Obviously this isn't a very practical autonomous approach.
No.
The fact remains that EM only carries a certain amount of momentum and
this device claims to "amplify" it. And as I said above, any device that
can provide a constant thrust for a fixed electrical input *must* be an
over-unity device in free space irrespective of any relativistic effects.
Adrian said:Dirk Bruere at NeoPax wrote:
... snip ...
Actually no, a device can produce constant thrust without using energy,
as long as the thrust does not move the object over any distance, ie do
work.
All objects produce thrust against the ground ( gravity ) all the time,
but no work is done, as long as they dont rise or fall.
The catch is that you still cant use the thrust to
provide motion without using energy. So you can ( in principle ) hover,
but you cant climb, unles you provide extra energy. And it would seem
from the analysis presented that you can produce low thrust in free
space, and get some motion, as long as you keep either the thrust or the
velocity small. The energy you need comes from the input energy, so
there is no 'over unity' gain.
No.
The fact remains that EM only carries a certain amount of momentum
and
this device claims to "amplify" it. And as I said above, any device that
can provide a constant thrust for a fixed electrical input *must* be an
over-unity device in free space irrespective of any relativistic effects.
Dirk Bruere at NeoPax said:Not in the case of an engine that does not emit anything.
Why should the velocity be kept small?
How does the engine know when to stop, since there is no absolute
reference frame? That's why I said "free space". In which case a
constant thrust will generate a constant acceleration for a constant
power. So for a constant power input the velocity increases linearly,
kinetic energy increases as velocity squared. Where does that extra
energy come from?
MooseFET said:One solution:
From the point of view of someone outside, the thrust decreases and
the clocks on the spacecraft slow down. From the point of view of
those on the spacecraft the clocks are normal and the thrust is
constant. As a result, no extra energy would be needed but it still
won't work.
What seems to happen is that the acceleration is limited, so even thoughDirk said:Why should the velocity be kept small?
How does the engine know when to stop, since there is no absolute
reference frame? That's why I said "free space". In which case a
constant thrust will generate a constant acceleration for a constant
power. So for a constant power input the velocity increases linearly,
kinetic energy increases as velocity squared. Where does that extra
energy come from?
Adrian said:What seems to happen is that the acceleration is limited, so even though
you can have significant thrust, you accelerate the device away from the
EM field trapped inside. The energy loss is the work done, and you gain
kinetic energy, but at the expense of reducing the Q of the device, so
you reduce the thrust accordingly. At the very high Q needed to get
significant thrust ( Kg, rather than mg ), the velocity change needed to
reduce the Q gets very small. Think about the detuning effects of
Doppler shift caused by the relative motion of the cavity and the field.
You can also look at it as though the device has some huge effective
mass, dependent on the Q, so the acceleration is very small, even though
the thrust can be reasonably high.
It still looks to me like a neat gadget, with limited applications in
moving small spacecraft around at low accelerations, and with a long
lifetime, not limited by carrying propellants. Moving anything else at
'reasonable' acceleration, or using it to create a hovercraft in the
Earths field, seems to be not possible.
It doesnt, its not the velocity which is the problem, its theDirk said:That doesn't work unless there is some absolute reference frame.
Otherwise how does the engine know how fast it's going?
Adrian said:It doesnt, its not the velocity which is the problem, its the
acceleration, and that is not subject to a local frame of reference.
However in thinking about this a bit further, I can see that you
probably cant get any more acceleration than you would by simply
pointing the microwave emitter out the 'back' of the rocket, and spewing
EM radiation (photons) out in a directed beam. At least that way you
dont have the problem of containing a very high energy density inside
your device, and the exhaust velocity is at least as high as you can
possibly get. Where you get the energy from for converting into photons
is another matter.