Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2102885 times)

Offline Stormbringer

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From what I remember, originally there was the Alcubierre "Warp Drive" concept proposed by Mexican physicist Miguel Alcubierre, which required a jupiter-sized mass of dark matter. Then Dr White came up with a refinement of the geometry, so that the amount of dark matter was much less (someone compared it to the mass of the Voyager space probe.) Then Dr White announced his intention to test whether a "space warp" was possible, by using a Michelson interferometer to try to detect a path-length difference when a voltage was applied to a capacitor ring.

So that stuff was all purely related to Alcubierre "Warp Drive". And of course news media were widely reporting that NASA was researching how to develop a Warp Drive, and the news stories were of course showing pictures of the starship Enterprise from Star Trek. But Shawyer's EMdrive was nowhere in that picture, and was an altogether separate and much less reported story on its own.

Then when the Eagleworks lab got involved in experimental testing to verify the Shawyer EMdrive concept (or Cannae drive, whatever) that's when suddenly the 2 stories began to merge, and speculation was put forth that the EMdrive was somehow a "Q-thruster" and then further that it was a "Warp Drive". Since the actual mechanism - if any - is unknown, what it is seems to depend on who's doing the speculating.
Maybe there is some of that going on out there. But what i am recalling is from this thread. and I think it may have been Mr March or someone directly in a conversation with Mr March in this thread. Again my memory may be faulty on who but not where. It happened here. :) ...or maybe i am insane. :)

And besides that, Paul March was initially involved with research on Prof Woodward's "Mach Effect"  theory, which is again something altogether different from Alcubierre warp drive and EMdrive. Mach Effect as of yet cannot be claimed to violate the established laws of physics, and is supposedly a prerequisite or necessary consequence of Einstein's Relativity.

But so the Woodward Mach Effect experiments were about oscillating masses, weren't they? They were not the same type of apparatus as the EMdrive.

So when I see people mentioning warp drive, Woodward's theory, and EMdrive all in the same thread, it kind of looks like the lines are being blurred here. These things originally started out as completely distinct from each other - they were 3 separate things - and now it looks like they're all being mashed together in the thread discussions. Perhaps it's because the same researchers at Eagleworks have been involved in investigating all 3 things.
Having had time to think about it. the person said one is just an "introverted warp" drive. compared to the WI article which is an extroverted warp drive. so maybe it's searchable...

EDIT:  No; no luck. But maybe that jarred someone else's memory?
« Last Edit: 05/05/2015 09:06 PM by Stormbringer »
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Offline TheTraveller

Eagleworks mounted their PA on the balance beam.   The frequency source could also be custom made and mounted on the balance beam.   That would eliminate the coax problem.
Interesting photograph; I have not seen it before.   The experiment is nicely setup with very good shielding for air currents.   But I don't see how it can be called cryogenic.   It looks like the Nitrogen dewar is just supplying dry Nitrogen.   The apparatus inside the clear boxes and sitting on a postage scale is not a dewar.   Unless he has found a supplier of room temperature superconductors it is not a superconductor test.  Superconducting cavities have to be cooled with liquid Helium and to keep the lHe from boiling off in a flash the lHe dewar has to be surrounded by a liquid Nitrogen dewar.   A high vacuum has to separate the dewars from everything and high IR reflective surfaces and other exotic contrivances are needed.   Otherwise the cryogens boil off and the whole thing turns into a missile.   High temperature superconductors are easier to work with because they only require liquid Nitrogen.  The second picture shows my crufty rotating magnetic field setup.   The white thing is a styrofoam container filled with liquid Nitrogen and the dut (device under test).
Here is what is inside the shiny metal cylinder. An EM Drive with a superconducting inner surface.

According to Shawyer it is designed to be cooled by liquid Nitrogen and it's super-conducting surfaces are formed from YBCO thin films on sapphire substrates.

OK I see how that works now; just a liquid Nitrogen dewar with the dut suspended in it.   Very similar to my setup.   Nitrogen boil-off will affect the lower scale but not the one that supports the dut so much.   I would imagine there is a lot of boil-off during a test.     YBCO thin films have high AC losses; typically above 60 Hz.   No doubt these are specially designed to minimize those lossses.
Shawyer reports on that unit:

Quote
Small signal testing at 77 deg K confirmed the design, with a Q of 6.8x106 being measured

An EM Drive with a Q of 6,800,000! Massive!
« Last Edit: 05/05/2015 09:09 PM by TheTraveller »
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Online Rodal

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Eagleworks mounted their PA on the balance beam.   The frequency source could also be custom made and mounted on the balance beam.   That would eliminate the coax problem.
Interesting photograph; I have not seen it before.   The experiment is nicely setup with very good shielding for air currents.   But I don't see how it can be called cryogenic.   It looks like the Nitrogen dewar is just supplying dry Nitrogen.   The apparatus inside the clear boxes and sitting on a postage scale is not a dewar.   Unless he has found a supplier of room temperature superconductors it is not a superconductor test.  Superconducting cavities have to be cooled with liquid Helium and to keep the lHe from boiling off in a flash the lHe dewar has to be surrounded by a liquid Nitrogen dewar.   A high vacuum has to separate the dewars from everything and high IR reflective surfaces and other exotic contrivances are needed.   Otherwise the cryogens boil off and the whole thing turns into a missile.   High temperature superconductors are easier to work with because they only require liquid Nitrogen.  The second picture shows my crufty rotating magnetic field setup.   The white thing is a styrofoam container filled with liquid Nitrogen and the dut (device under test).
Here is what is inside the shiny metal cylinder. An EM Drive with a superconducting inner surface.

According to Shawyer it is designed to be cooled by liquid Nitrogen and it's super-conducting surfaces are formed from YBCO thin films on sapphire substrates.

OK I see how that works now; just a liquid Nitrogen dewar with the dut suspended in it.   Very similar to my setup.   Nitrogen boil-off will affect the lower scale but not the one that supports the dut so much.   I would imagine there is a lot of boil-off during a test.     YBCO thin films have high AC losses; typically above 60 Hz.   No doubt these are specially designed to minimize those lossses.
Shawyer reports on that unit:

Quote
Small signal testing at 77 deg K confirmed the design, with a Q of 6.8x106 being measured

An EM Drive with a Q of 6,800,000! Massive!


what is "small signal testing" ?  I imagine that it means just testing the cavity for resonance, to measure the Q but it is not referring to a small force measurement, is that right ?

Online Flyby

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Shawyer reports on that unit:

Quote
Small signal testing at 77 deg K confirmed the design, with a Q of 6.8x106 being measured

An EM Drive with a Q of 6,800,000! Massive!

and no trace on how much force it generated?   :'(
because that is what we all really want to know: does a higher Q effectively increase the thrust factor dramatically ?
So far we've only seen claims and projections on how great it will be.

A clear result would be so much nicer...
It would give better idea whether it effectively works and if it does, how well the EMdrive is scalable...

Iow,(IF it works) is it only good enough for orbital corrections or do we have prospect on interplanetary travel in the coming 10 or 20 years?

Offline R.W. Keyes

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How much power are you planning on putting through that coax?  The thicker it gets, the stiffer it gets, which would mess up any delicate movements of the balance beam.  My experience is with amateur radio, and there 50 watts is the most you would try to put through something like RG-59 (looks like cable-TV cable).   RG-8, which can handle a kilowatt, is about 1 cm in diameter and not very flexible at all.

Power losses in the cable of course turn into heat...
Thanks for the feedback.

Did a few years as a ham. You are right. Cable heat losses need to be considered. Will be very small. Max power will be 100W.

Me as well. I am still licensed but not very active.
CQ CQ de N1YRK   

I agree coax does get stiff, but some moreso than others. at these frequencies, they'd probably be using LMR400, which is still pretty stuff, but I recall it being less so than RG8.  I was one of the principles of a small company which made 2.4 ghz antennas in the early 2000s.

Offline JonnyDamnnox

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Hi guys, on the theoretical side, has someone looked into this:


http://arxiv.org/abs/hep-th/0508246
Using strong external fields to modify locally a space-time

Online ThereIWas3

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The cool thing about all this that, while the theories may need the PhDs and the GR stuff, the experiments can be done by hundreds of basement hacker types.  (Maybe not the superconductive part).  There may be a Zephram Cochrane out there somewhere yet who will crack this.
« Last Edit: 05/05/2015 11:34 PM by ThereIWas3 »
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Offline TheTraveller

Traveller

I strongly suggest you do not place your "mass displacement measurement device" underneath the drive unit.  If you invert your thinking and make the opposite end of the fulcrum lever "heavier" such that it places a small but measurable  force on the scale, you can data log the hopefully rising-value differences on activation. The reasoning behind this is that your scales "might" be impacted by a grav-wave event originating from the em-drive, creating a chaotic temporal event stream.

You may also need to consider the geometric shape of the end caps.

I suggest you have a browse though data on  Schmidt-Cassegrain telescopes for the optical path folding models employed and their direct relevance to the end cap shapes. Consider the possibility for the existence of a focal-point inside the actual tube assembly "that has not been mentioned in the literature", and where this point may occur relative to the end caps. Also consider the ability to extend the tubes physical length with simple mechanical sliding action end cap(s). These factors could impact the deliberate creation of a specific point-of-intersection and as such an area of modified intensity relative to the internal space of the unit. The energy imbalances.. could be interesting.
Or
Consider end cap shapes as a geometric means of creating a parallel-path guide for simple reflection/refraction in a laser-like mode
Interesting suggestions for your 1st post. Most appreciated. Welcome to the forum.

I once designed and built Schmidt-Cassegrain telescopes so I understand fully your, light bulb illuminating, suggestions.

Ever spent any time in the UK?
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Offline JonnyDamnnox

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I have another question, is there any official statement that NASA is working on warp field experiments? Just for the Wikipedia article on the topic.

Online Rodal

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REVIEW OF A.L. Cullen's "Absolute Power Measurement at Microwave Frequencies" IN REFERENCE TO EM DRIVE

First of all I would like to thank Roger Shawyer, C.Eng MIEE. SPR Ltd., for having made available to us Cullen's paper published in Feb., 1952, which is very difficult to obtain otherwise.  This paper has been referenced by Mr. Shawyer in a number of his papers and presentations on the theory and practice of the EM Drive operation, and thus we were always curious as to its content.

As Cullen himself writes, the purpose of Cullen's paper was to describe the techniques adopted for his Ph.D. thesis experiments (at the University of London) and to explain their theoretical basis.

It is apparent, upon reading Cullen's paper, that:

1) No truncated cone (fustrum of a cone, as in Shawyer's EM Drive) of any kind was used in Cullen's experiments or ever discussed in Cullen's paper from a theoretical viewpoint. Cullen used constant (through their length) cross-section waveguides.  One waveguide had a rectangular cross-section and another waveguide had a circular cross-section.

2) No summation of forces for microwaves inside a closed cavity truncated cone (fustrum of a cone, as in Shawyer's EM Drive) are ever discussed in Cullen's paper.

3) No Einstein’s law of addition of velocities or relativistic frames for the beam and the waveguide are used or discussed in Cullen's paper.

4) The cylindrical waveguide used in Cullen's experiment for radiation pressure measurement was not a closed-cavity with all internal surfaces reflective (as in the EM Drive) but was instead a cylindrical waveguide with transparent glass as one of its ends (transparent glass which deliberately allowed the microwave beam to enter the cylindrical waveguide and also allowed the reflected waves to escape the cylindrical waveguide so that only travelling waves would hit the other end of the waveguide for pressure measurements).

5) The expressions that Cullen uses to calculate the pressure were first derived by Maxwell (the diagonal component of Maxwell's stress tensor).  Cullen uses the more intuitive, physical derivation of J.J. Thompson.  In any case, Cullen's radiation pressure expression is fully compatible with the expressions used by Greg Egan http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html, where Greg Egan restates the known conclusion (from Maxwell's equations) that any closed resonating cavity has zero net force due to radiation.  (Cullen correctly shows the non-zero pressure on a cylindrical waveguide that has only one reflecting end - the other is "open" because it is made of transparent glass). 

6) Cullen points out (in section 2.1 of his paper) that the power supplied to the load can be obtained by integrating the time-average Poynting vector, and that the force on the reflecting end of the circumferential waveguide is proportional to the supplied power.  This is completely correct.  It follows therefore that, since the time-average Poynting vector for a closed cavity is known to be zero, then the total radiation force in a closed cavity is zero, as per Cullen, which is in agreement with the known result restated by Greg Egan.

SUMMARY: I could not find anything in Cullen's paper supporting that a closed cavity resonating at microwave frequencies, like the EM Drive, can produce a net thrust force (or be used for any kind of propulsion).   

Cullen's Ph.D. thesis is based on the classical theory of electromagnetism, by Maxwell, and hence wholly consistent with the known result that Maxwell's equations show no net thrust for any closed cavity, with all internal surfaces reflective, and having any arbitrary shape.




Cullen's article has a number of useful observations:

A) It was impossible to obtain a stable baseline, even on a relatively short-term basis of a minute's duration.  This continual drifting of the baseline was found to be due to air convection currents set up by small and changing temperature gradients within the microwave waveguides.  The remedy was to reduce the air resistance of the reflecting end plate so that the convection currents would have no appreciable effect.  The reflecting end plate was replaced by a system of concentric wire rings (shown on Fig. 12 of Cullen's paper).  The rings acted as an almost perfect reflector of the electromagnetic waves but at the same time had a small effective cross-section to air currents.  NASA, Shawyer, Yang, and other EM Drive researchers would be well advised to experiment with replacing the end plates of the EM Drive with this system of concentric rings, in order to address the problem of air convection currents that has plagued radiation pressure experiments in ambient conditions ever since Maxwell 140 years ago.

B) It is very interesting that the deflection vs. time curves for the microwave radiation pressure experiments look  similar to the deflection vs. time curves for the tests performed at NASA Eagleworks, except for the drifting baseline present in the NASA tests.

C) Cullen used a rectangular waveguide to direct the radiation. To prevent subsequent radiation from the reflector the waveguide was terminated with a matched load, such that there was no reflection of the incident wave.  A T-junction was used for transmission to a piston (a cylindrical waveguide with one end made of transparent glass and the other end capped by a reflector), without reflection into the main guide.

D) Standing wave measurements were separately performed with a closed cavity and movable (micrometer) end plate to assess the purity of mode TM01 in the waveguides, to make sure that resonance at other modes (mainly TM21) was not significant.


_______________________

Attachment: ABSOLUTE POWER MEASUREMENT AT MICROWAVE FREQUENCIES
By A. L. CULLEN, Ph.D., B.Sc.(Eng.), Associate Member.
(published February, 1952.)
« Last Edit: 05/06/2015 04:32 PM by Rodal »

Offline ThinkerX

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Quote
I have another question, is there any official statement that NASA is working on warp field experiments? Just for the Wikipedia article on the topic.

Eagleworks, NOT NASA proper.  And:

Quote
Mr March told us recently back in the thread that they had a small positive signal on the warp interferometry front.

Emphasis on the small, and possibly a false positive (refraction from atmosphere was mentioned).  Lots more tests under differing conditions badly needed.

Offline Carl G

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I have another question, is there any official statement that NASA is working on warp field experiments? Just for the Wikipedia article on the topic.
Mr March told us recently back in the thread that they had a small positive signal on the warp interferometry front.

Which isn't an official NASA statement, as anyone will obviously know, which is why Stormbringer didn't emphasis that. To be clear for those who need it, the answer is no.

Offline PushHigher

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Here is my KISS EMDrive test system rough draught.

TheTraveller - best wishes with your endeavor.  While pondering the shape of the device from here:

http://1.bp.blogspot.com/-IUOMkncS1sM/VFLSUw2HeoI/AAAAAAAA3yE/Zl3iaKJyrX0/s1600/emdrivedata2.png

I feel the drive is optimized to align the EM vertically down the chamber.  Any force measuring apparatus that requires the device to turn might reduce efficiency.  I would suggest using a pulley.

Wesley Crusher wishes this  ;)

Offline deltaMass

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Although most of what's being discussed here concerns the static force produced by an EmDrive, I would like to look ahead to the dynamics in free space. In this regard, and needing no recourse to relativity for low velocities, all types of propellantless propulsion device are created equal; i.e. we model them with constant input power which results in a constant thrust, which in turn produces a constant acceleration. A little high school physics and a dash of algebra (see below) should suffice to convince you that, for any and all such devices, there exists a break-even velocity, above which more energy has been produced than has been consumed. As the device continues to further accelerate, a continuous source of free power is available. Thus we have not only perpetual motion, but free energy to boot.

It is worthwhile to quantify the value of this break-even velocity, which turns out to be a very simple expression. The relevant equations we use (symbols having their usual meaning) are:
k := F/P in Newton/Watt
v = a t = (F/m) t
Ein = P t
Eout = 0.5 m v2

From the first 2 equations we get
t = (m v) / (k P)

At breakeven, Ein= Eout and v := v0
or
2 P m v0 / (k P) = mv02
so
v0 = 2/k

Armed with this expression, the performance of any propellantless propulsion device may be examined, if its 'k' value is known.
This is an adjunct to my overunity analysis for all propellantless propulsion craft when allowed to move subrelativistically in free space. This time we'll use the mundane expressions for cars on roads, rockets and all the familiar things that do not employ floobie dust in their operation. Let's look at an ideal car on a flat road using ideal tyres. The constants of the motion this time are only P (engine power) and m (all up mass). Now we have a velocity-dependent thrust F and variable velocity and acceleration. Now our Newtons/Watt coefficient 'k' also varies with velocity. We only need two equations to sort this all out and to demonstrate its mundanity.

1. F = k P = m a, so a = (P/m) k
2. P = F v = P k v, so k = 1/v
so again 1. a = dv/dt = (P/m) (1/v)

Solving this by integration (with the limit v=0 @t=0) we get
P t = 0.5 m v2

which is the same as saying
Ein = Eout

No overunity here. Utterly mundane.
It is the crucial expression P = F v which makes everything come out OK.

This is what Shawyer uses.
But EmDrive is not a tyre and spacetime is not a road.
It's in fact eventually (v > 2/k) overunity,  because F remains constant at all v.
And that's in turn because if F knew about v then a preferred frame of reference exists, and SR is violated.

Online sanman

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Or perhaps they are connected as there are countless examples I can give in physics where what was supposed to be earlier theories (thought to be very different at the time) they turned out to be incomplete parts of a bigger theory encompassing them.  Many examples: Schrodinger wave equation and Heissenberg's matrix formulation, etc etc

But Rodal,

Prof Alcubierre's theory doesn't really involve any displacement in the conventional sense, and only says that spacetime can be warped using the exotic Dark Matter (whose existence has not been proven or disproven yet). The Alcubierre-based spaceship only sits still, while space itself does all the moving/warping. So Alcubierre's concept is able to go FTL, since there are supposedly no limits on warping space as there is with conventional displacement of matter. It doesn't relate to conservation of momentum at all, since it doesn't even refer to impulse or acceleration - so I don't see how it connects to the other 2 things.

Warp Drive is a purely FTL thing and doesn't claim to have anything to do with conventional displacement or momentum as we know it. And neither Mach Effect nor EMdrive claim to be able to go FTL, even though they are claiming a novel mechanism for displacement.

Prof Woodward's Mach Effect theory of transient mass fluctuations says that if you change the internal energy of an accelerating mass, then you are effectively altering its mass property in a way that creates an asymmetric imbalance in the action-reaction force, and can thus achieve net movement without ejecting any propellant in the conventional way. Do this over and over again, using a mechanically oscillating system where the charge oscillates in phase, and you get continuous movement. He is also saying that no system is a truly closed system, since it will always be interacting with every other mass in the universe. That seems to also imply that you cannot truly apply Conservation of Momentum unless you're talking about the universe as a whole.

Shawyer's EMdrive seems to claim that asymmetric radiation pressure is possible in an asymmetrically-shaped cavity where one end acts as a waveguide for the trapped radiation. The EMdrive is supposed to be similar to a photon-rocket, but it's a photon-rocket fitted with an expander nozzle at the end, in the form of a waveguide.


Online sanman

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I wanted to keep this in its own separate post.
For a clear and detailed explanation of EMdrive's propulsion mechanism, I will quote to you from Goatguy who hangs out on NextBigFuture:

http://nextbigfuture.com/2015/05/emdrive-possible-warp-or-hyperspace.html#more

Quote from: GoatGuy
Quote from: sanman
So if it's the standing wave inside the resonant cavity which is losing energy, then how is that energy being converted into momentum? If the standing wave is pushing on the cavity in a net direction, then how is that standing wave creating an asymmetric radiation pressure inside the cavity? How does the asymmetric shape of the cavity result in asymmetric radiation pressure? Shouldn't radiation pressure inside a cavity always be symmetric?


GoatGuy in reply to sanman:

…then how is the energy being converted to momentum… is one of the fundamental questions which physicists are arguing over. The notion is that the asymmetry of the cone as a waveguide for RF energy realizes a net force away from the small end as the RF wave stream propagates outward and out the end.

This is my gross simplification, but it has a large analogy to help visualize the principle(s) involved: the classic chemical rocket engine.

If one thinks of a chemical rocket engine combustion chamber as NOT a combustion chamber, but merely a round sphere full of high pressure gas, if the sphere is unperforated, obviously there is no gas escape, and no net thrust. No matter how much pressure is in the theoretical sphere. Now, poke a hole in it. The entrained gas will escape. The speed with which it escapes depends on its viscosity, the size of the hole, its density and the speed of sound in the gas, and the interior pressure. The thrust can be either measured or calculated with relative ease. Yet, this is not the highest thrust that the pierced sphere can produce.

Higher thrust can be produced by having an expansion nozzle on the other side of the hole. How's this? Simple enough: the exhaust stream is still pressurized, and will expand in 3 dimensions, so its cross sectional area is also increasing. This too is an outward radial pressure. If not captured (from a simple hole), then it is lost thrust/force. If the expanding gas though impinges on the exhaust cone as it expands outward, the outward expansion is vectored “downward”. Change of momentum vector results in more thrust.

Same gas, more thrust.

(This is one of the chief reasons there are shock diamonds in jet and transparent rocket thrust.)

_______

Now, take the analogy back to the EM-thruster regime. And a very brief review of electromagnetic principles. The first is, that when one reflects an electromagnetic wave, there will be momentum transfer orthogonal to the net moment vector change. Fancy wording, but what it means is this. IF you reflect an electromagnetic wave 180°, or exactly backwards at 100% efficiency (no loss), the reflection will produce a force F which equal to 2E/c. (E = energy, c is speed of light). 1 joule of reflected energy will produce a force of 6.67×10⁻⁹ newton-seconds.

(Note that this applies to light itself. Hence why giant reflectors of sunlight in space might make useful force generators someday. The light is “free”)

Now, imagine instead that we are reflecting the EMR (electromagnetic radiation) only 90°, at a right angle. The moment change will be the same, but the vector isn't ½(180°) but ½(90°) = 45°. The force will depend on the grazing angle, but just suffice to say that we'd realize something closer to E/c instead of 2E/c.

(Again in the solar-sail idea, if one were to fold the solar sail at right angles, and present the corner to the Sun, obviously one side would reflect sunlight away at right angle, and the other side would reflect the other way. The outward force would cancel. But there'd still be a net push. Only ½ that of the reflected backward geometry.)

OK, enough EMF theory. The point is clear: reflected EMR generates a force which depends on the angle of reflectance and the power of the EMR being reflected.
You might want to re-read that!

The principle of the EM-Thruster is that it is a cone of (at this point) constant angle. Looks like about 30° to me or so. Like the rocket-engine, the "high pressure gas" or intense EMR is injected at the small end. Being standing waves in a resonant structure, it bounces around a lot, making its way outward after many reflections. Every time it reflects, it imparts a bit of force against the angled surface of the cone.

This results (as the theory goes) in an amplification of imparted momentum-vector change force. The purveyors of the idea go on to theorize that the amplification should depend on the number of times the EMR wave reflects before exit (or diminishment from lossy-ohmic resistance by the copper metal each reflection). This is actually a rather reasonable idea. The trick though is to keep the RF energy entrained in that cone for as many reflections as is possible while also maximizing the cone's 'exhaust angle'. (i.e. make it a loooooong pencil of a cone, and the angle is so small that there would be very little net propulsive force. But you'd get zillions of reflections. Make it quite wide, and you get good force from each reflected wavelet, but they won't hang out in the cone very long. So, not much net force.)

ANYTHING that I've heard so far seems to rest upon the above idea. Which is fine, because its solid physics. It even explains why someone got the thought of putting a dielectric back there at the concentrated end, to try to keep the EMR in-tube longer. More reflections. Keeping the energy in-tube.

But where the principle goes “crazy” is in supposing that the Q of a EMR reflective cone -and-dielectric-system- can be engineered up to the giga Q level or higher (through superconduction). Obviously, not for an open-ended system. So far (and the images are surprisingly hard to find), I believe that the cone is not open ended, but is capped with a flat reflector. Again, to entrain the EMR in the cone for as many reflections as possible. (and the only way to get Q above about 100 or so for 30° angle cones).

So, we must wait and see. Tho' my electromagnetic theory is pretty solid, I really haven't spent significant time analyzing the train-of-physics that is concocted to support the idea that thrust is dependent on power² (which it should not be!), or of EMR frequency² (which it should not be!).

Lastly, there is a kind of “esthetic solution” to the problem of the high-output devices violating conservation of energy above W/F (watts of power per newtons of force) m/s (meters per second velocity)… sort of. The first is, when the device accelerates, the reflecting EMR inside the cone is bouncing off surfaces which are also accelerating; though infinitesimal, each reflected wave will lose energy, lowering (widening) its wavelength. Since by its nature, resonant systems have a sharper-and-sharper frequency of resonance as Q increases, the wave-system will no longer be in resonance, and won't optimally reflect endlessly. This is helpful in solving the free-energy-device problem, though not complete.

The actual conservation of energy solution comes from noting that in any reflected momentum system, one cannot derive more momentum energy from the energy reflected, than the reflected energy itself.

Sounds circular? It is. But it also works. Bounce a fast-moving glass ball bearing back and forth between large glass reflective surfaces, and it will bound perhaps thousands of times (losing near-all of its kinetic energy to sound (tick-tick-tick…) and to heat). Put the reflectors though on perfect bearings (so that they might accelerate). The ball bearing will only now bounce a few dozen times. If one calcultes how much kinetic energy is imparted to the moving reflector wall, its easy to show that no more kinetic energy than what was within the bearing's frame of reference is imparted to the accelerating reflector. In a perfectly coupled system, the energy transfer would be 100%. The ball would come to rest, and the moving reflector would have all its original kinetic energy added to whatever Ek it had to begin with.

This then looks (to me) like the same system. The EM-Drive concept is bouncing the EMR around, transforming its electromagnetic energy into kinetic thrust energy, with some limit, which is very probably asymptotic to the input energy.

Which would be just fine. Exactly what electric motors do all the time. Transforming electromagnetic energy to kinetic energy. The trick is to find a way to "do this" and also limit the transfer of kinetic energy to that imposed by the basic rocket equation. (Which limits imparted kinetic energy in the vehicle to 1/2 the kinetic energy of the exhaust, integrated over the flight of the vessel.)

GoatGuy
« Last Edit: 05/06/2015 02:56 AM by sanman »

Offline deltaMass

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Quote from: GoatGuy
Now, take the analogy back to the EM-thruster regime. And a very brief review of electromagnetic principles. The first is, that when one reflects an electromagnetic wave, there will be momentum transfer orthogonal to the net moment vector change. Fancy wording, but what it means is this. IF you reflect an electromagnetic wave 180°, or exactly backwards at 100% efficiency (no loss), the reflection will produce a force F which equal to 2E/c. (E = energy, c is speed of light). 1 joule of reflected energy will produce a force of 6.67×10⁻⁹ newton-seconds.
If you want to quote people who explain physics to you, I'd caution you to first check that they understand some physics. Because what is written there is nonsense. It's not even dimensionally correct.

Please begin all over again, this time using  F = P/c

Online sanman

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I hear you, but the main salient thing for me is that the EMdrive is supposed to be a photon rocket - the resonant cavity is not a closed chamber but is actually a chamber with a hole in it (the waveguide end), just as the combustion chamber of a conventional rocket has a hole in it.

So photons are shooting out one end of the EMdrive, just as photons would shoot out one end of a photon rocket, just as propellant shoots out the end of a conventional chemical rocket. What differentiates EMdrive from a traditional photon rocket, is that the photons have been drained of a lot more momentum due to bouncing around in the waveguide first before exiting. This is analogous to the way an expansion nozzle and bell allow the propellant exhaust particles to bounce around more and transfer more of their momentum to the rocket before exiting.

So maybe it's best to start with the picture of a photon rocket in your head, since a photon rocket doesn't violate Conservation of Momentum.

Offline deltaMass

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If I pretend that the EmDrive is a photon rocket, for which the thrust F = P/c, then the value of k in N/W = 1/c = 3.3 10-9 N/W. That is at least 3 orders smaller than the experimentally determined values of k that we've seen. And yet you wish to model the EmDrive as a diluted form (in some sense I do not understand) of a photon rocket? That would seem to imply a k value lower than 1/c, but in fact we see a higher one.

I can't bring myself to agree.

And about this "exhaust hole" of yours: this implies that the placement of the hole (or the waveguide power feed, you assert) must align with the resultant thrust vector. But experiment shows that this is not the case.

Again, I cannot agree with you.
« Last Edit: 05/06/2015 03:31 AM by deltaMass »

Online sanman

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Alright, but I want to ask about theory first: in principle, is it possible to have a classical photon rocket fitted with an optical equivalent of the expander nozzle and bell? Can a waveguide be used as an optical equivalent of expander nozzle and bell, allowing photons to be drained of more momentum than they otherwise would when exiting a photon rocket? Because that part doesn't seem like it's violating Conservation of Momentum or any established physical laws.

So if a chemical rocket with nozzle and bell is more efficient than a chemical rocket without nozzle and bell, then imagine a device which is analogously trying to be more efficient than a classical photon rocket in a similar way. Is that idea by itself a violation of any established mainstream physics?

If it is not, then how to build such a device?
« Last Edit: 05/06/2015 03:47 AM by sanman »

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