Talk-Polywell.org

http://blog.wired.com/defense/2008/09/c ... ildin.html

It's called "EmDrive"
http://www.emdrive.com/

I read about this EMdrive when it first came out a couple of years ago. I think its a total crock. However, the Chinese are more than welcome to try it out if they think it might be real.

Intuitively it seems to be against the 3d law of Newton. But maybe not.

In spite of their double talk about frames of reference, this still violates conservation of momentum. Draw a box around the system and ignore what is inside. Nothing comes out, except a little heat. Without some outlet for the momentum, there can be no thrust.

Here is a paper which uses a different argument concerning the photons that bounce around the inside: http://www.assassinationscience.com/joh ... rfraud.pdf

Perhaps there is some error in their measurements. Maybe when it warms up, there are convection currents.

And not only breaking conservation of momentum, but also the 2nd law of thermodynamics.

pstudier wrote:In spite of their double talk about frames of reference, this still violates conservation of momentum. Draw a box around the system and ignore what is inside. Nothing comes out, except a little heat. Without some outlet for the momentum, there can be no thrust.

Here is a paper which uses a different argument concerning the photons that bounce around the inside: http://www.assassinationscience.com/joh ... rfraud.pdf

Perhaps there is some error in their measurements. Maybe when it warms up, there are convection currents.

I have been watching this thing since it was first mentioned in New Scientist, and i'm still not certain what to think about it.

Of course the proof is in a test, which they have. (video available at emdrive.com) but i've always been suspicious of the fact that the video is short, and there have been no further forthcomming videos. Also, their experimental setup is not self contained, it is attached to the rest of the world with various wires etc. There is a lot of room for false effects.


If the effect is real, I would be making a better demonstration of the working model were I them.


David

I look forward to them launching a spacecraft with this drive and watching it go nowhere.

Hopefully no one will be on board. Except maybe Shawyer.

I would like to see the Chinese try to develop the drive based on Heim Theory.

TallDave wrote:I look forward to them launching a spacecraft with this drive and watching it go nowhere.

Hopefully no one will be on board. Except maybe Shawyer.

I did read a critique of shawyer by one of his former fellow employees of that satellite company he worked for. From what I remeber, the guy described shawyer as having gone fanatical, and how he would disregard anything which disproved his belief that he could get thrust from a tuned cavity.


I'm actually hoping the crack pot wins this one, just to beard the cat, if for no other reason.


David

pstudier wrote:Draw a box around the system and ignore what is inside. Nothing comes out, except a little heat.

And gravitational interactions and whatnot. This is supposed to be a relativistic effect, right? Remember, the rationale for the Mach-Lorentz thruster is that it pushes on all the mass in the rest of the universe - maybe the Shawyer thruster is similar. I haven't done the math myself, but if someone has and thinks it's worth a shot, I'd be very careful about making blanket pronouncements about its impossibility.

For the record, I strongly suspect this thing won't work. My first instinct as an engineer is that you're correct, and that it violates Newton's 3rd. But I'm willing to wait and see.

93143 wrote:

pstudier wrote:Draw a box around the system and ignore what is inside. Nothing comes out, except a little heat.

And gravitational interactions and whatnot. This is supposed to be a relativistic effect, right? Remember, the rationale for the Mach-Lorentz thruster is that it pushes on all the mass in the rest of the universe - maybe the Shawyer thruster is similar. I haven't done the math myself, but if someone has and thinks it's worth a shot, I'd be very careful about making blanket pronouncements about its impossibility.

For the record, I strongly suspect this thing won't work. My first instinct as an engineer is that you're correct, and that it violates Newton's 3rd. But I'm willing to wait and see.

I have previously asked MSimon's what he thought of the Mach-Lorentz thruster and his response was "Not much."


What do YOU think of it ?


David

Man, isn't this stupid idea dead yet? Last time it was on nasaspaceflight.com and he was pitching it to the Brits. Once you cut all the quantum crap he throws at the problem, it's really just a matter of him ignoring the radiation pressure on the sloped sidewalls by invoking some gibberish about it acting like a waveguide. It's a blatant fraud.

What do YOU think of [the Mach-Lorentz thruster]?

I don't know much about it. I read a paper on some experiments they did, and some of the reasoning by which they ruled out certain effects sounded incompatible with the way something else was explained, but since I was more or less just skimming the paper I could well have misunderstood.

It would be great if it worked, just like it would be great if Heim drive worked. It's not in my area, though, so I don't know enough to have an opinion on either Shawyer's drive or the MLT. If I had to pick one as less unlikely than the other, my uneducated impression leans toward the MLT, possibly because they have a somewhat pedigreed excuse for dodging the obvious interpretation of Newton's Third Law.

On the other hand, if Polywell works but the propellantless drives don't, I might just have a career in high-thrust electric reaction engine design. QED/ion-wind/MHD-augmented RBCC magnetic-nozzle variable geometry... fun stuff. My current work is in CFD modelling of transcritical (preheated) fuel sprays in turbojet combustors, but I'm starting to get sick of droplets - my M.Sc. had to do with droplet deformation in electric fields...

I'll still be disappointed if the LHC detects the Higgs boson...

93143 wrote: My current work is in CFD modelling of transcritical (preheated) fuel sprays in turbojet combustors, but I'm starting to get sick of droplets - my M.Sc. had to do with droplet deformation in electric fields...

darn, it's been twenty years since I worked with computational fluid dynamics. I'm curious if it's changed much?

kcdodd wrote:And not only breaking conservation of momentum, but also the 2nd law of thermodynamics.

How does this break the 2nd law, which states that entropy increases? Electricity in, allegedly some of this energy is converted to motion, and most of the energy is converted to heat.