Author Topic: EM Drive Developments Thread 1  (Read 781292 times)

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #780 on: 09/19/2014 07:19 PM »
First post, bear w/ me, might be too far behind, or simplistic an inquiry.


1. If I imagine a coffee can (resonator w/ no velocity change?) sitting upright on a scale on my desk, and I fill it w/ a certain amount of photon energy, General Relativity would say that the can would become heavier by an amount equal to the "mass equvalent" of that energy. Presumably, the falling photons would gain energy and momentum and the rising ones would lose them. The momentum exchange w/ the upper and lower walls would give a difference force (weight) equal to the above.

(I imagine a "time dialation" explanation would work as well)

If an accelerating frame of reference (AFM) causes dispersion of the enclosed photons, is it unreasonable to expect a forced dispersion to create an AFM ???

2.  Somewhat more outlandish, if I imagine an enclosed spaceship, with it's own power supply and equipment on board to create electron/positron pairs and accelerate them in the direction of "thrust" such that they anihilate after a short distance and the doppler shifted radiation is captured, does that spaceship accelerate ???

I appologise for being so far behind, thanks.

Offline Rodal

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Re: EM Drive Developments
« Reply #781 on: 09/19/2014 07:20 PM »
Here is a paper written to describe the Casimir energy between a metallic plate and a dielectric plate within a cavity. The configuration is somewhat similar to the Tapered Cavity tested at EagleWorks.

http://math.scichina.com:8081/sciAe/EN/abstract/abstract377962.shtml#

I wonder if someone can help interpret this paper. To me, it does not seem consistent with what has been published elsewhere, in particular I see an unfamiliar term

Quote
where -pi/(24a^2) is the Casimir force between two ideal conducting plates separated by a.

But also this paper is developed in a reference system where c=1, h-bar=1. That is a common system but how does one convert the results into standard units of measure.

I forgot, if I ever knew how.

http://en.wikipedia.org/wiki/Speed_of_light

http://en.wikipedia.org/wiki/Planck_constant

Well yes I know that, but the author uses "1" in the equations derivation for each of these terms so where do I substitute the real values back into the end result to get real measurable values? Am I forced to carefully follow the derivation through to the end then know where the c's and h-bars go? (numerator, denominator, power, etc.)

<<ABSTRACT The Casimir effect between metal plate and dielectric plate is discussed with 1 + 1-dimensional potential model without using cut-off method. Calculation shows that the Casimir force between metal plate and dielectric plate is determined not only by the potential V,, , the dielectric thickness and the distance a between the metal plate and dielectric plate, but also by the dimension of the vessel. When a is far less than the dimension of the vessel, the Casimir force F~1/a ; conversely F~1/a^2.>>

This is my reading: it is a Chinese paper, using a Russian formulation to come up basically with the type of distance-dependence law involved, and they reach  the conclusion that it is an inverse law or an inverse squared law depending on the distance. 

They are not interested in deriving the actual magnitude of the force, and they do not derive the actual magnitude: all they are interested in is to state what kind of dependence it has, to contrast with the metal plates distance-dependence and the dielectric plates distance-dependence cases.
So, if my reading is correct, you cannot obtain the actual magnitude of the Casimir force for a given application from this paper.
_____________
They write <<In, the. 1 + 1-dimensional model, the vacuum fluctuations of the two modes of the electromagnetic field can be obtained by solving the massless one-dimension Klein-Gordon equation, ...,where h = c = 1>>

Take a look at http://en.wikipedia.org/wiki/Klein%E2%80%93Gordon_equation  and compare the dimensional Klein-Gordon equation with this paper's dimensionless equation

Basically, when they wrote h = c = 1 I stopped reading, since obviously, h[J s] and c [m/s] have different dimensions, so they cannot be equal, not just in magnitude but Joules*sec is a different dimension than meter/second.  If the authors wanted to conduct a non-dimensional analysis they should have specified more carefully what are the non-dimensionalized variables.

« Last Edit: 09/19/2014 07:46 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #782 on: 09/19/2014 07:58 PM »
@Rodal

Thanks for that. So what the paper shows is a very different Casimir force resulting from the containment vessel, (the cavity). But it doesn't show any reason to expect an unbalanced force giving the thrust. Ok, I'll keep looking if something else strikes me.

But it seems essential to include the RF waves in the equations somehow. I have found a way to do that (I think) but it requires some public domain software and 100 hours on a super computer. (Not very supper, only 1000 processors) still, that is 250 times more processors than I have on my machine, so the calculations would take me what, about 1000 days?

But I wouldn't know how to set up the models anyway.
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Offline Rodal

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Re: EM Drive Developments
« Reply #783 on: 09/19/2014 08:13 PM »
@Rodal

Thanks for that. So what the paper shows is a very different Casimir force resulting from the containment vessel, (the cavity). But it doesn't show any reason to expect an unbalanced force giving the thrust. Ok, I'll keep looking if something else strikes me.

But it seems essential to include the RF waves in the equations somehow. I have found a way to do that (I think) but it requires some public domain software and 100 hours on a super computer. (Not very supper, only 1000 processors) still, that is 250 times more processors than I have on my machine, so the calculations would take me what, about 1000 days?

But I wouldn't know how to set up the models anyway.

Well, I would put it this way: they claim (based on their theoretical model --no experiments) that the vacuum chamber dimensions inside which the Casimir-experiment's metal and dielectric reside, affects the Casimir force.  They claim that when the distance between the metal and the dielectric is much smaller than the dimensions of the vacuum chamber , that the Casimir force between a metal and a dielectric is given by the inverse of the distance between the metal and the dielectric: the power of this inverse law is (-1) when they are a very small distance apart, and (-2) (an inverse square law) when they are further apart. 

Having said that, I have no idea how one could get any space-propulsion out of this.  Assuming that you trust this  paper, the force is attractive, and its only significance is for very small distances (as in nanotechnology). So if one wanted to create a nanotechnology mechanism comprising a dielectric and metal, this may be useful to let you know of stiction problems caused by the Casimir force.  But I don't understand how this minute attractive force for very small distances between the dielectric and the metal are going to result in space-propulsion of the macro-structure. 
« Last Edit: 09/19/2014 08:32 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #784 on: 09/19/2014 08:36 PM »
@Rodal  Neither do I. The materials are physically attached so the forces are all reacted via the structure.

Here are the references to the super computer application I referred to above, for anyone interested.

http://arxiv.org/abs/0904.0267

and

http://arxiv.org/abs/0906.5170

It too is useful at the nano scale, but at least it in in the time domain using Maxwell's equations.
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Online Stormbringer

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Re: EM Drive Developments
« Reply #785 on: 09/19/2014 08:40 PM »
i don't know for sure but i assume that the thinking is that once you have the force manifest in space you can grab it and manipulate it. if it were negative if you push it it comes toward you. So you'd presumably push on it from the direction you want to go and then it would react by moving opposite of the force you applied. even better if it was subject to amplification.

however; the question (other than if any of that is really applicable; amplification and so forth) is can the equivalency of energy density differences actually fully operate as negative energy or mass for the purpose of a space drive.

Casimir force is just one speculative candidate for the source of negative energy and mass needed for most Warp or FTL schemes in accordance with the more esoteric GR solutions and space time metrics. There are others. E.G; Woodward wonders if you can separate the terms in  Mach's principle equation to reveal the naked negative mass of normal matter. none of them are currently probable but most are not well understood so there could be a surprise that makes them more realistic.
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Offline Rodal

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Re: EM Drive Developments
« Reply #786 on: 09/19/2014 08:59 PM »
i don't know for sure but i assume that the thinking is that once you have the force manifest in space you can grab it and manipulate it. if it were negative if you push it it comes toward you. So you'd presumably push on it from the direction you want to go and then it would react by moving opposite of the force you applied. even better if it was subject to amplification.

Much more powerful than the Casimir force: an astronaut could bring a magnet inside his spacecraft.  On the way to Enceladus, he can reach for his suitcase inside which is his powerful magnet and point the magnet towards a  (hypothetical) steel structural framework inside his spacecraft.  The astronaut would feel a powerful force attracting the magnet and him towards the structure.  Even as the magnet moves the previously freely floating astronaut towards the steel structure, none of this will result in any translation of the center of mass of the spacecraft.  No translational propulsion of the spacecraft resulting from these  internal motions of the astronaut or the magnet.

So, the only way this could work as propulsion is if there would be a force attracting a metal (or dielectric) plate towards a particular direction in space.  But such a force is not the Casimir force.  There is a gravitational force: we are trying to get out of Earth's deep gravitational well, and we use the gravitational force of the planets to our advantage as a slingshot... There is the Solar Wind, and there is the Magnetic Field around the Earth. 
« Last Edit: 09/19/2014 09:08 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #787 on: 09/19/2014 09:49 PM »
The Casimir force is not really that "Small." For two parallel plates close together, the Casimir force:

F(a) = 0.013 *area/a^4 (dyn/cm^2) = 0.0013*area/a^4 (N/m^2) where a is the separation distance in micrometers.

Sure, for a = 1 micrometer, F(a) = 0.0013 N/m^2, but for a = 0.1 micrometer, F(a) = 13 N/m^2
and for a = 10 nanometers, F(a) = 130,000 N/m^2

But that is kind of beside the point. We know that for every action there is an equal and opposite reaction. The experiments have measured the reaction leaving us with the question, "What is the action?" Discounting "error" as one explanation, that leaves "Something not attached to but pushing on the thruster." 

I postulated an internal virtual metallic plate that caused the base plate or the thruster internally to react via the Casimir effect as though the virtual plate were there. So far, we can't find a mechanism to create this virtual plate. And real plates attached internally (or externally) would not cause an external thrust from the Casimir effect.
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Offline Rodal

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Re: EM Drive Developments
« Reply #788 on: 09/19/2014 10:04 PM »
And we have the fact that the thrust measurements are related to the dielectric resonator. 

No dielectric resonator = no thrust force. 
Direction of thrust force --> direction in which dielectric is pointed towards.
Highest Electric Field (by orders of magnitude) --> in the dielectric resonator.

And we have an experimental setup where much larger, classical force fields are involved, at the macro scale.

I am not convinced that the conventional force fields and inertial forces involved have been adequately investigated to ascertain that they are not responsible for the measured thrust forces.
« Last Edit: 09/19/2014 10:41 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #789 on: 09/19/2014 11:06 PM »
Quote
I am not convinced that the conventional force fields and inertial forces involved have been adequately investigated to ascertain that they are not responsible for the measured thrust forces.

Did you mean "internal?" In any case, I concur. That thought is what led me to make my super computer post above. The approach given there may allow all fields to be evaluated in unison. (It may not, too.) But I personally am stymied by a lack of expertise and a lack of computing power, although it may be that the computing power needed is not as extensive as thought. It depends on the models after all.
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Offline Rodal

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Re: EM Drive Developments
« Reply #790 on: 09/19/2014 11:16 PM »
Quote
I am not convinced that the conventional force fields and inertial forces involved have been adequately investigated to ascertain that they are not responsible for the measured thrust forces.

Did you mean "internal?"

No, I meant inertial.   The thrust forces are measured in an inverted torsional pendulum that is known to exhibit parasitic motions due to coupling of torsional with swinging modes.  One of the coupling modes couples the inertia of swinging in one direction with the motion of swinging in the perpendicular direction, leading to a parasitic torsional force.  Another coupling mode couples the velocities of swinging motion (in perpendicular directions to each other) resulting in another parasitic torsional force.   Thus, torsional forces can be measured that are not due to a thrust from the EM drive.  They need to use magnetic damping to try to cancel these parasitic modes.  Magnetic damping may cancel the parasitic modes and/or may produce further parasitic modes.  This is why at MIT Aero & Astro the inverted pendulum is constructed such as to keep the thruster horizontal at all time, to eliminate these parasitic instabilities.
« Last Edit: 09/19/2014 11:30 PM by Rodal »

Offline ThinkerX

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Re: EM Drive Developments
« Reply #791 on: 09/19/2014 11:50 PM »
Quote
No, I meant inertial.   The thrust forces are measured in an inverted torsional pendulum that is known to exhibit parasitic motions due to coupling of torsional with swinging modes.  One of the coupling modes couples the inertia of swinging in one direction with the motion of swinging in the perpendicular direction, leading to a parasitic torsional force.  Another coupling mode couples the velocities of swinging motion (in perpendicular directions to each other) resulting in another parasitic torsional force.   Thus, torsional forces can be measured that are not due to a thrust from the EM drive.  They need to use magnetic damping to try to cancel these parasitic modes.  Magnetic damping may cancel the parasitic modes and/or may produce further parasitic modes.  This is why at MIT Aero & Astro the inverted pendulum is constructed such as to keep the thruster horizontal at all time, to eliminate these parasitic instabilities

Seems to me these issues with the inverted torsional pendulum could be suppressing genuine thrust.  IE, the problem cuts both ways.  On the one hand, a possible false positive; on the other a false negative, or at least a lower amount of thrust.

Maybe they should use actual scales for these tests?  Device weighs X amount when first placed on scales, if it generates thrust, then the weight changes.  Much more stable, less subject to forces creating false positives.   There must be some scales out in the world sufficiently sensitive for these tests.

Another thing I have been wondering about, especially given the requirement for an exact placement of the dielectric resonator:  maybe this really is some sort of 'microwave drive' that works because of its shape and placement of microwave source?  A sort of geometric loophole?  No invocation of exotic quantum mechanics or violation of conservation of momentum.  If so, would it still be useful in space?

Offline frobnicat

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Re: EM Drive Developments
« Reply #792 on: 09/20/2014 12:20 AM »
Another thing I have been wondering about, especially given the requirement for an exact placement of the dielectric resonator:  maybe this really is some sort of 'microwave drive' that works because of its shape and placement of microwave source?  A sort of geometric loophole?  No invocation of exotic quantum mechanics or violation of conservation of momentum.  If so, would it still be useful in space?
Not more useful in space than a photon rocket : well collimated microwave photons are not less efficient than visible light laser photons or xray photons, as far as thrust/power is concerned (at most 1/c, as usual). Since claimed thrusts are 3 order of magnitude higher, they can be explained either by
- radiation pressure building between device and chamber walls, effectively exchanging momentum with something else heavy nearby (so : not useful in space)
- exotic physics

It can't be both classical (not exotic) and useful in space (more than photon drive).

There is still the impractical possibility of using radiation pressure in space to have better than 1/c thrust/power and classical physics (not exotic) but that would imply bouncing photons (microwave or visible...) back and forth between two spacecrafts, or a spacecraft and a body (possibly a heavy body like a moon) to have a thrust separating them : the average number of times photons bounce (quality factor) would be a multiplicator for the thrust/power. So with very efficient mirrors so that a photon bounces 1000 times before being lost, thrust/power on the order of the Cannaes drive could be classically possible. But keeping the photons bouncing would not just be a matter of good mirrors, the main problem would be the limits of diffraction (mirrors diameters/wavelength > distance/mirrors diameters if I recall well, much superior if you want multiple bounces). As in beamed propulsion (laser driven sails) where one is already happy to have a single travel from source to target, only a 1000 times more "difficult" (read : mirrors wide as moons)

« Last Edit: 09/20/2014 12:26 AM by frobnicat »

Offline ThinkerX

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Re: EM Drive Developments
« Reply #793 on: 09/20/2014 02:17 AM »
Quote
- radiation pressure building between device and chamber walls, effectively exchanging momentum with something else heavy nearby (so : not useful in space)

Sadly, this is the direction my thoughts are leaning at the moment.

Got to thinking of an analogy, using a hamster as a substitute for a subatomic particle:

1) Put hamster in ordinary cubical cage, he can bounce around all he wants and not budge the thing. 

2) But, put hamster in a small sphere - one of those plastic ball thingies - and he can go in pretty much any direction, barring obstacles.

3) Put hamster inside a sealed cylinder of about the same volume as the plastic ball, and he can go in two directions, but the cylinders shape won't allow for other movement.

Which got me to thinking that if this EM Drive works in space at all, it might be because of a very rough equivalent to option 3 with the hamster - it works because of its shape.  Yes they bounce around randomly on the inside, but the containers shape dictates that they strike with the greatest force in the direction you wish to move.  (Solid strikes 'forward,' tangential strikes to the side and back.) 

But that doesn't appear to be an option.

My other thought is some sort of 'Dark Matter' or 'Dark Energy' interaction - microwaves are cited in efforts to detect Dark Matter at least; maybe under the right conditions they could 'excite' Dark Matter or Dark Energy.  But that's just a wild guess.

Offline aero

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Re: EM Drive Developments
« Reply #794 on: 09/20/2014 02:32 AM »
Quote
My other thought is some sort of 'Dark Matter' or 'Dark Energy' interaction - microwaves are cited in efforts to detect Dark Matter at least; maybe under the right conditions they could 'excite' Dark Matter or Dark Energy.  But that's just a wild guess.

Don't be too concerned about posting a wild guess. I wonder how often good ideas start with a wild guess that evolves. A lot of the time, would be my wild guess.
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Offline IslandPlaya

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Re: EM Drive Developments
« Reply #795 on: 09/20/2014 02:53 AM »
Quote
My other thought is some sort of 'Dark Matter' or 'Dark Energy' interaction - microwaves are cited in efforts to detect Dark Matter at least; maybe under the right conditions they could 'excite' Dark Matter or Dark Energy.  But that's just a wild guess.

Don't be too concerned about posting a wild guess. I wonder how often good ideas start with a wild guess that evolves. A lot of the time, would be my wild guess.
I agree, but we are pushing things with dark hamster.

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #796 on: 09/20/2014 01:34 PM »
I can't help thinking the "Dark Hamster" might be some sort of mechanism that acts like the "Pushme/Pullme" exploiting the difference between 2 areas (volumes) of different characteristic impedance.

On reflection, you need 3 in this case.

It's easy enough to think of the shear between the internal 2, but what couples to the outside?
You would need some mechanism that wants to "average" over the local free space ?

If radiation, then to maximize the P/E something that travels much less than c?
(the assumption is that acoustic radiation would be obvious to the experimenters ?)
« Last Edit: 09/20/2014 02:20 PM by Notsosureofit »

Offline Rodal

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Re: EM Drive Developments
« Reply #797 on: 09/20/2014 01:49 PM »
You can have a heck of a lot of hamsters walking inside a cylindrical spacecraft, and also pushing and pulling against its ends but the center of mass of the spacecraft is not going to translate at all.

The reason why the cylinder will rotate on a surface on Earth is because of gravity and friction between the cylinder and the surface.  Sorry, there ain't no friction against a fixed background when you are in space.  Just walking, pushing and pulling inside a spacecraft won't translate the center of mass of the spacecraft.  You can also play with a tennis ball against one of the spacecraft's walls and that still won't translate the center of mass of the spacecraft.  For the spacecraft's center of mass to move you have to let the tennis balls (or photons, or whatever) escape the spacecraft.
« Last Edit: 09/20/2014 01:55 PM by Rodal »

Online RonM

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Re: EM Drive Developments
« Reply #798 on: 09/20/2014 01:54 PM »
Here is a paper written to describe the Casimir energy between a metallic plate and a dielectric plate within a cavity. The configuration is somewhat similar to the Tapered Cavity tested at EagleWorks.

http://math.scichina.com:8081/sciAe/EN/abstract/abstract377962.shtml#

I wonder if someone can help interpret this paper. To me, it does not seem consistent with what has been published elsewhere, in particular I see an unfamiliar term

Quote
where -pi/(24a^2) is the Casimir force between two ideal conducting plates separated by a.

But also this paper is developed in a reference system where c=1, h-bar=1. That is a common system but how does one convert the results into standard units of measure.

I forgot, if I ever knew how.

http://en.wikipedia.org/wiki/Speed_of_light

http://en.wikipedia.org/wiki/Planck_constant

Well yes I know that, but the author uses "1" in the equations derivation for each of these terms so where do I substitute the real values back into the end result to get real measurable values? Am I forced to carefully follow the derivation through to the end then know where the c's and h-bars go? (numerator, denominator, power, etc.)

As Rodal wrote, h = c = 1 doesn't work because of the units. h = 1 and c= 1 are okay to run through simple calculations, but the variables must stay for deriving simplified equations.

You need to look at the derivation to see if the variables in question are cancelled out during the derivation. If they are, then you don't have to worry about them or their units.

If the authors immediately replaced the variables in question with 1 and then proceed to derive a simpler equation, their equation has nothing to do with the real world and is merely a mathematical exercise.

Online RonM

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Re: EM Drive Developments
« Reply #799 on: 09/20/2014 02:13 PM »
You can have a heck of a lot of hamsters walking inside a cylindrical spacecraft, and also pushing and pulling against its ends but the center of mass of the spacecraft is not going to translate at all.

The reason why the cylinder will rotate on a surface on Earth is because of gravity and friction between the cylinder and the surface.  Sorry, there ain't no friction against a fixed background when you are in space.  Just walking, pushing and pulling inside a spacecraft won't translate the center of mass of the spacecraft.  You can also play with a tennis ball against one of the spacecraft's walls and that still won't translate he center of mass of the spacecraft.  For the spacecraft's center of mass to move you have to let the tennis balls (or photons, or whatever) escape the spacecraft.

Yes, you have to either throw something out the vehicle (rocket exhaust) or interact with something external to the vehicle (rotating tires on a road).

Microwaves bouncing around a chamber will not result in a net force. Even if they were interacting with an external field, the different force vectors will cancel out, resulting in no net force.

Now if a device pushes against an external magnetic or gravitational field, or even virtual particle plasma (whatever that is supposed to be), it could produce thrust. Currently, magnetic propulsion is the only one we know how to do.

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