[IDMclean]

Could someone explain in plain english how this thing works? I have an okay idea as to how it works, but I want to hear some other angles on it.

Relativity Drive, From NewScientist.com. Shawyer Theory

[Qfwfq]

How this thing works is very simple: by neglecting momentum conservation.

[Aireal]

Qfwfq
Question, How does it violate momentum Conservation? I have read about this engine over the last couple of days, and discussed it on other forums. My first reaction was that it was pure bull, till I researched it more. The concept seems vaild, though I am still in doubt as to its practical application. However the effect is sufficent to warrent farther research, perhapes in the future it may be more practical.

KickAssClown
The method they use is not too complex. The engine is nothing more than a wave guide tube that has been carefully shaped for the waveform used, and the ends capped. When the waves rebound from the capped ends, some of their energy is converted into thrust in opposing directions. The differance in thrust is achieved in this manner. The wave guide is shaped so that the waves tend to cancel each other out at one end. In other words the troughs and crests line up at one end, canceling out the waves much like sound reduction technology works. The result is that less waves rebound with less force at this end of the wave guide, as energy has been used in the canceling out of other waves. Where as at the other end, the waves match up crest to crest, and impart greater energy when they rebound from this end. Thus a slight differance in thrust is achived. No laws of physics are voilated that I can see, the concept is fairly simple, I am surprised someone has not come up with it before now.

[TheFaithfulStone]

Yeah, sounds like bull to me. But I'm not sure where the momentum conservation is being neglected.

It seems sort of along the same lines as a nuclear photonic - that is, that it's propellent is radiation generated on board, and taking advantage of the fact that the speed of light is always faster than you're going to continue to add thrust. It's a still a radiation pressure drive, and it's not "energy free" it's just "propellant free."

The question that I see is where do those extra photons go? The photons themselves, which impart their energy to the wave guide tube, have to go somewhere.

He said his experiment worked, so what else could cause thrust to be developed in that situation?

TFS

[Aireal]

TheFaithfulStone

Your question of "where do those extra photons go?" is a tough one to answer. It hits at the very heart of the wave/particle duality of quantum theory. I did not touch on this in my post, but even if it does not make a good engine, it may make a good research tool.

If photons are purely particles, you must account for where they went, if purely waves then you don't. Quantum theory says they are both, so what is going on? This device may help us resolve this issue. I am trying to think of some experiments that could be devised along this lines. There are many theories out there, and answers in this field could eliminate many of them.

In my paper on this site http://hypography.co...m-expanded.html I made a model of the atom that is both wave and particle based. If you read it, let me know what you think of it, it's a work in progress. This device good be used to check that model and others.

Now how do I get my hands on one of these for testing?

[IDMclean]

As I understand it then, from the schematics, theory, and from your angle, it takes advantage of the constructive, destructive interferance aspect of the photon and essentially "stacks" the momentum to one side of the ship, resulting in forward momentum on the order of the difference of momentum.

As for where the photons go? They remain, in majority, in the box, and some escape by way of superpositioning. the photons that contribute towards the engines thrust are absorbed into the molecular structure of the engine. Am I correct in my understanding? Force, momentum, and energy are strictly conserved here, near as I can tell.

[Qfwfq]

Can anyone give me a hint as to why the conical shape ought to make the wave guide dispersive?

Aireal said:

If photons are purely particles, you must account for where they went, if purely waves then you don't. Quantum theory says they are both, so what is going on?

Quantum theory says that the wave must determine a positive-definite, conserved probablity density because this is how it realistically represents the particle's behaviour. Which are the crests and which are the troughs?

Aireal said:

Now how do I get my hands on one of these for testing?

Build one (easy, if you have a bit of dough to blow) and suspend it, with an optical system to amplify any horizontal change in equilibrium. If, observing none, you suspect this balance of not being sensitive enough, put two equal ones on a torsion balance and make the arms as long as you please...

[Aireal]

Hello Again KickAssClown and Qfwfq

As to why the conical shape makes the wave guide dispersive. I shall have to make some conjecter here, so bear with me. My guess is they the EM waves are not focused and aimed at the other end directly when emitted like a laser beam. The graphs on their site show a zig-zag path for the waves, and I suspect this is the reason for it. This zig-zag path allows some waves to become out of step with the others over the course of their trip. The math for calculating the correct shape of the wave guide, angles ect. would be a factor limiting my abilty to make on of these at home. Well, that and money.

On the matter of conserved probability density, crests and troughs, and other deep subjects. This is why I thought this device may make a good research tool for various theories. Can the "real" and "virtual" particles of quantum theory be treated differantly? Wave theories could be tested with it, and so on. Please look at my paper on this site, a link to it is in my last post. This should answer your questions as to crests and troughs, and show why I would want one of these devices for research.

[TheFaithfulStone]

aireal said:

If photons are purely particles, you must account for where they went, if purely waves then you don't

No, I'm pretty sure you still have to account for where they went.

As for the conical shape, It's supposed to work by increasing the thrust applied at one end of the "engine." But it won't.

I found the momentum conservation problem, I think.

Imagine a trapezoidal pool table, set on a frictionless surface. If you were to launch a cue ball at the side of the table, it would bounce off at the same angle it impacted at. Imagine your cue ball is a photon and so it bounces around in there pretty much forever. It imparts some momentum to the table each time it hit's.

Now, the paper is right in saying that there will be more bounces at one end of the table / cone than at the other - however, they will not be in any useful direction. In order to develop forward thrust, the cue ball (or photon) needs to be moving opposite of the direction in which you want to go.

In that image, I didn't follow the path of the cue ball for very long, but all of those "hits" impart momentum in the wrong direction.

As long as that cue ball is trapped on the trapezoidal table, the momentum from it will eventually cancel itself out. The table may wiggle a bit, but it's not going anywhere.

Now if you were to leave the narrow end open, you might be able to get a hair bit more of efficiency than simply launching the cue ball out the back - but I'm pretty sure there are more efficient rocket designs.

But, the guy did say his experiment worked. I would be interested to know what actually caused the thrust he saw, if he didn't just make a measurement error.

TFS

[Qfwfq]

It is trivially that momentum will be conserved regardless of the shape and it's sufficient to reason on x and y components. The only way to have propulsion is by having radiation leave the craft, and as well focussed as possible, an idea as old as the knowledge that the radiation carries energy-momentum. However, as EM is massless, you use a lot of energy for a given thrust.

[TheFaithfulStone]

Just because it's trivial to you Q, doesn't mean it's trivial to us hoi-ploi. Even if it is obvious after a little thought.



TFS

[Erasmus00]

If momentum is conserved, then an object is incapable of moving its own center of mass. This follows trivially from the deffinition of the center of mass (the place where the total momentum sums to 0. If momentum is conserved, this place always has 0 momentum). From this, we can easily see that this device simply can't work.
-Will

[IDMclean]

Your assuming that the EM radiation is part of the mass, and that it moves with the frame. As I understand special relativity though, the photon's frame is invariant, where as the mass's is variant.

Also, for a partial possible answer to the absorbing aspect of the em bouncing inside the construct, if you use the right material you could end up with sides that minimally absorb the microwave radiation and ends that absorb it greatly. Energy is only absorbed in discrete packets.

Furthermore, it should be noted that he uses Microwave radiation, which can be used to induce electric current in some materials.

Erasmus, how then do I move my center of mass? I am an object, I have mass, and I have a center of mass. I walk and that changes my momentum, correct? As I understand it, how I do that is by difference of potentials. Is it so improbable that you can power a thruster without ejecting things out the tail end?

[Erasmus00]

KickAssClown said:

Your assuming that the EM radiation is part of the mass, and that it moves with the frame. As I understand special relativity though, the photon's frame is invariant, where as the mass's is variant.

For light



So the momentum is related to the frequency, which doppler shifts.

Quote

Erasmus, how then do I move my center of mass? I am an object, I have mass, and I have a center of mass. I walk and that changes my momentum, correct? As I understand it, how I do that is by difference of potentials. Is it so improbable that you can power a thruster without ejecting things out the tail end?

You don't move your own center of mass. You push off the Earth, and you move relative to the Earth. The center of mass of the you-Earth system does not move.

It is impossible to power a thruster without ejecting something IF momentum is conserved.
-Will

[Qfwfq]

Certainly Will but some here have been challenging the premise that momentum is conserved, speculating that wave-particle duality might provide some legal loop-hole...

As usual, I'm tight on time to bend down to the, uhm, "hoi-ploi", so perhaps you could excercise your ever unlimited patience here, and educt them on how there's no getting away with it.

In the pool-ball argument of course it is simple, no matter what the angle of the surface and ball motion one can always take the x and y components. This may help to understand exactly how, in any case, the change in the vehicle's momentum will always be opposite to the change in that of the ball. Therefore, if the ball is to never escape, a prolonged increase in the vehicle's (time-averaged) momentum would imply the same for the ball, in the same way instead of the opposite way. Although it's less simple to eviscerate the details for photons in quantum formalism, there is no escaping momentum conservation.