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Talk-Polywell.org • EM Drive
Page 1 of 48

EM Drive

Posted: Fri Mar 04, 2011 1:56 am
by ladajo

Posted: Fri Mar 04, 2011 5:35 am
by Ivy Matt

Posted: Fri Mar 04, 2011 9:56 am
by Skytreker

Posted: Fri Mar 04, 2011 11:21 am
by chrismb
Yes. It is indeed impossible. I've mentioned this chap before here. He has a piece of kit pluged into the wall. Same issue I have raised with "Mach effect" thrusters applies - the reaction force causing the motion is likely being borne by the electrons pushing back on the generator generating the electical power.

You need an electrical supply that is in the same inertial frame as the motive parts, to exclude this [simple] interpretation.

Posted: Fri Mar 04, 2011 2:18 pm
by Professor Science
Yet another potentially super disruptive technology that made a splash while i was in high school that nothing has happened with in the intervening half decade. I was rather excited about it then too, played around with a colony ship built around the idea of a poly-well and EMdrive travel combo.

Posted: Fri Mar 04, 2011 2:35 pm
by ladajo

Posted: Fri Mar 04, 2011 2:50 pm
by Diogenes

Posted: Fri Mar 04, 2011 3:06 pm
by kcdodd

Posted: Fri Mar 04, 2011 3:17 pm
by ladajo

Posted: Fri Mar 04, 2011 4:11 pm
by chrismb

Posted: Fri Mar 04, 2011 4:21 pm
by Tom Ligon
I must have been in junior high school, maybe even earlier, when I first heard about ion propulsion, and wondered what it would take to rig up a science fair demo. Even at that early age, and with a propulsion system who's dainty thrust should overwhelm most pure EM approaches (flashlight thrust), I realized the difficulty in measuring the thrust meaningfully. Any net magnetic field produced from the current flow would play havoc with the net force.

Basically, I'll believe it when I see it move itself in space. I would be very hard to convince with any terrestrial amateur setup.

That said, it looks like a fun hobby, and I've done things with 9V batteries that would make you cringe. At 2.45 GHz and 850 W, he's using microwave oven parts ... as we did at EMC2.

There have been some speculations regarding the completeness of Maxwell's equations, specifically a possibly missing term of disputed importance originated by Grassman via Lorentz, which supposedly predicts a net force generated by certain antenna configurations. If the missing term is valid, and if I follow the arguments right, Special Relativity becomes invariant rather than covariant, and no net thrust occurs. I have no strong feelings on this, but got sucked into a few minor tests by one of the proponents. Anyway, the device may have some use for testing the issue.

http://www.padrak.com/ine/NEWELBOOK.html

Posted: Fri Mar 04, 2011 4:43 pm
by kcdodd
Could you be more specific about what numbers? In regards to his theory, it just seems confused at several basic levels.

He begins by deriving a net thrust by saying the photons have different momenta at each plate and thus exert different thrust as they reflect. However, he ignores the fact that the photons in his theory change momentum without interacting with anything! This is exactly where his theory violates conservation of momentum. They just magically change momentum while traveling between the plates. Where did the momentum go? I could make a guess.

He then derives an equation giving the thrust as a function of velocity of the engine. So, he either ignores, or doesn't know, that in special relativity the thrust should not transform in this way. In the direction of travel T' = T (for T = thrust in the rest frame of the engine), no matter how fast the engine is going.

So, assuming he derived any numbers form his theory I would not expect them to predict anything physical.

Posted: Fri Mar 04, 2011 4:52 pm
by Skipjack
But the mach thruster does not break the conservation of momentum! Just like a wheel pushes against the ground, the mach thruster pushes against the rest of the universe.
I dont quite see the problem with that. It still needs energy in order to accelerate from what I understand. So it does not violate the conservation of energy either.
The EM- drive is- from what I understand- a very different matter.

Posted: Fri Mar 04, 2011 5:00 pm
by chrismb

Posted: Fri Mar 04, 2011 5:06 pm
by Skipjack