"Impossible" EM space drive?

Nice try, but fallacious.

The implication of your paraphrase is that I'm begging the question by assuming the validity of "established dogma".

I'm not. I simply say that his conclusion contradicts the assumptions built into his own premises. Whether those premises are "established dogma" or science fiction is beside the point.

[Counting the fallacies is left as an exercise for the reader]

--
Richard Herring

OK Let me add to my list of suggestions that when one is referencing a parameter, it is usually appropriate to define what you are talking about.

I'm not all that sure that gravitational effects are irrelevant when/if we drag in relatavistic activities.

Bill

Look who's talking. Let me guess, your screws' threads are so lose, they are like crochet needles.

?

Come on Eric, show us that 4 dollar watch you lifted from Walmart.

No, why? Is it true?

Never said that either. You are a confused soul.

In message , Bill Miller writes

"Parameter"?

It's implicit in the newsgroup names, the thread title and the actual paper under discussion. *Electromagnetic* space drive. Not electrogravic or gravimagnetic or ...

Don't let the R-word confuse you: there are two distinct theories labelled "relativity". The relativity being invoked here is _special_ relativity, as it relates to electrodynamics. The only forces being considered are electromagnetic.

_General_ relativity is a theory of gravity; special relativity is not.

--
Richard Herring

no the momentum pushes on the pipe and the pipe pushes on the water.

if water flows south and turns east, net force on the pipe the net force on the pipe is to the southwest. Bye. Jasen

tsk tsk We have discussed the similarities between EM and gravity many, many times on this group. Far too many, I would suggest, for us to categorically dismiss gravitation as being "irrelevant" when we are discussing ideas about accelerating masses. That's kinda what gravity does, isn't it?

It sounds like you may not have read any of Jefimenko's work on gravitation. If you had, you would have noted that he has derived many (all?) aspects of GR without delving into GR or SR. Just logical arguments derived from the simple concept of Causality. So, if gravitational effects can be derived without GR or SR, then it's not TOO much of a stretch to consider that the inverse might be true. --

Bill

Hi Timo,

This is not the first I've seen this design. IIRC some fifteen years back there was an AIAA paper on this. Also, here are some related resources,

(I think this is the AIAA paper)

Bottom line, it'll work...

Aetherist wrote: [snip crap]

Outhouse basement, it won't work...

Physics Today 57(7) 40 (2004) No aether

No Lorentz violation

--
Uncle Al 
http://www.mazepath.com/uncleal/ 
 (Toxic URL! Unsafe for children and most mammals) 
http://www.mazepath.com/uncleal/lajos.htm#a2

Which has nothing to do with this thread...

Hopefully not by the same author - the lapses would be much less forgivable. If it's over a decade old, why haven't the errors been corrected? Why hasn't the force on the tapered section of the waveguide been considered? This last point is the critical one - it's the most important, and obvious, error.

If the earlier version was by different authors, and sank into obscurity without working (it wouldn't be hard to build it, would it?), it's a strong indication that it doesn't work.

Interesting [1], but hardly related. The closest that it comes to it is discussing, e.g., the force exerted by a solenoid on a charged particle. Clearly related to electromagnetically-accelerated-exhaust drives, but nothing to do with the "drive" discussed above.

That hydrodynamic/electromagnetic analogies work so well suggests that the proposed device won't work. Waves within a fluid enclosed inside a rigid container aren't going to make the container move through empty space, are they?

"Sorry, no results were found."

Uses an electric arc discharge to ablate a block of teflon, and spits it out one end. What does this have to do with the "EM drive" being discussed?

Why would you expect it to work?

(IIRC, there's another thing to watch for in the paper - the author's Q is not the usual Q (for quality factor) of a resonator.)

Now, if somebody wants to develop a real working funky EM drive, perhaps they should consider the "runaway" solutions to the motion of a charged particle subject to radiation reaction.

[1] Not read this in detail yet, but it isn't a surprise that they find a Galilei-relativistic force law. What else would you expect when coming from (Galilei-relativistic) hydrodynamics? Even less of a surprise when one considers that Maxwell-Hertz-Heaviside electrodynamics was Galilei-relativistic, not Lorentz-relativistic.

Anyway, thanks for the interesting paper. Interesting looking references, too.

--
Timo

Exactly! How much momentum can you get from an EM pulse striking an antenna????

It is impractical since, while it works, it generates so little thrust that mass needed to build it (let alone, any payload) means the acceleration is almost non-existent... Try calc...ing the momentum transfer, even assuming 100%.

There a subtle but significant difference between doesn't work and impractical.

There is no such thing as rigid to the EM field. The AIAA article I remember (I don't have any copy and it has been at least 15 years) described a basic omni-directional pulse transmitter and a conic receiving antenna as the momentum collector. Which, if I understood the layout of this one, are very similar.

There are some very novel and interesting concepts in this area. The classic propellent-less drive is a simple rod which has a spring coiled around its center. On each end is mounted a stop plug. There are two plungers fitted on either side of the spring that can travel along the rod. The plungers are compressed against the spring and then released. they then travel in opposite directions along the rod until impacting the stop plugs. One stop lug is metal, the other a cotton wad. The difference in efficency of transfering the plunger's energy to the rod, rather tan the cotton and rod, will propel the rod in one direction.

This also will work, but so far as I know, has found no practical applications... a

It won't work in free space. All that happens is that the centre of mass is shifted back and forth.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.theconsensus.org/ - A UK political party
http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff

As much as is carried by the sum of the absorbed photons.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.theconsensus.org/ - A UK political party
http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff

... and scattered photons. (Well, for the simple case of omni-directional scattering aka re-radiation.)

--
Timo

I can't resist!

The Chinese ALSO invested quite a lot of money building "compact" Cross-Field MW antennas that "worked" by taking the cross product (ExH = S = Power) of the E field AND the H field "caused" by Displacement Current.

So, the Chinese can make technical blunders just like the rest of us!

Bill

Point 1. So long as things are non-relativistic, nobody has a prayer of making this work for all the usual reasons. The claim here is that relativistic effects change the outcomes of Newton's laws. So yes, Newton was wrong but ONLY for devices with relativistic speeds in them, not for any hydrodynamic models or devices.

Point 2. The tapered part of the cone was ignored. This is really a fatal error in the analysis in my opinion.

Point 3. While radiation pressure devices would theoretically work, this one is sealed so it's not that kind of thing. It's a cavity which means waves are going BOTH ways inside.

The TT Brown drive is of interest in the following way. In air the TT Brown drive is basically an Ion wind device (you can buy one over at the Sharper Image) with enough wind it could fly a light glider. The fringe story is that the TT Brown device ALSO works in hard vacuum. Of course we always have to raise the question how "hard" is thy vacuum? If there are significant ions left behind then some thrust has to be expected. Now IF and that is a VERY big "if" it is true that the TT Brown device does work in hard vacuum, then it's clear that such a device could be enclosed in a [large enough] conducting metal box, and still produce thrust. In that case even though the TT Brown device is electrostatic and the Chinese one claims to be electrodynamic, one might see the famed unidirectional forces from a sealed electrical device. However, I personally am not convinced that the TT Brown device works in a hard vacuum. [But of course, I'm not saying it's "impossible"!]