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#2300 by frobnicat on 27 Jan, 2016 21:33
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In other words, as shown by Frobnicat, if the EM Drive works as proposed by Shawyer and others, and you can really get force proportional to power, then eventually one does NOT need any solar power, as free-energy can be produced by a couple of rotating EM Drives.
I suspect that the EMDrive, and various EM free energy devices that surprisingly seem to work, turn on some yet unknown method for pulling heat out of the environment. The electrical input might be constant but, perhaps, electricity + heat drawn from the environment is not.
You mean, like some environmental cooling would be observed somewhere around an operating EM drive ? Then you are trading 1st principle issues for 2nd principle issues. By 2nd principle, the energy content of a single heat bath (at a single given equilibrium temperature) can't be transformed into useful (mechanical) energy.
To explain where apparent excess energy comes from (apparent excess as would be seen when operated above a certain velocity, if it could) your idea of "pulling heat from environment" would require at least two heat bath at different temperatures, or an environment far from thermal equilibrium; making the device a thermal engine (and the spent electric power just an auxiliary "catalyzer"). As for space application, do you see two different temperatures heat bath in deep space, ready to interact with "catalyzing" enclosed resonating microwaves to make up a thermal engine ?
To be added to the many strange things requested to be investigated in the vicinity of the device (radiations, space-time warps...) : cooling of the hot dark matter flow.
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#2301 by rfmwguy on 27 Jan, 2016 21:49
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http://www.scientificamerican.com/article/hawking-s-latest-black-hole-paper-splits-physicists/
Thanks for the link...nice article. "Soft" particles in a vacuum...now there's a new twist. Worth following for several reasons, not just to enjoy a high-level physics argument
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#2302 by kitsuac on 27 Jan, 2016 22:06
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I wonder if part of the divide over this is that engineers are accustomed to equipment occasionally operating in an undocumented manner while physicists rarely have an unexpected result other than a null.
There's probably some truth to that. Meanwhile, as a programmer I'm stunned when something does work as it's "supposed" to. It makes mathematicians seem positively insane to me. You mean you're going to write down pages of formulas and feel perfectly content that it's universally correct? Try doing that with code and 95% of the time there will be at least a few significant problems. IMO, anyone who believes their knowledge of the universe is complete (or even remotely close to complete) has their hubris out of control. -
#2303 by frobnicat on 27 Jan, 2016 22:39
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If the formula ΔE = ˝ m (V22 - V12) still applies then all the stuff about free-energy turns out to have been a red herring.
The rotation test will show this. Given an input of constant energy per second the acceleration per second reduces; after friction and air resistance have been allowed for.
Acceleration per second ?
I guess you mean just acceleration, as in "Given an input of constant energy per second the acceleration reduces". Thing is, I don't know how many time I'll have to repeat (probably as long as I care), the energy conservation issue does not depend on acceleration. Also making irrelevant considerations on kinetic energy.
If it was to be tested in the constant velocity regime, the issue could be investigated in this manner : For a given power, test how much force the device can hold against a wall of the lab. This is basically what's done at Eagleworks, just there is a spring between the device and the wall, but when the "thrust" is stable, the spring doesn't change length, hence there is no acceleration in principle. Then for the same given power, test how much force the device can hold against a forward facing wall of a train traveling at constant speed v. Test for various v, which is not to say that this is the drive that is accelerating the train, to be sure use different trains (I'm kidding).
Do we record same thrust regardless of v ?
-> Yes : there is a conservation of energy issue, as holding a 1N force on a forward facing wall (obviously, without having to push 1N the opposite direction on the floor or opposite wall, that would cancel the deal) of a train traveling at constant speed 10km/s amounts to giving the train a mechanical power of 10kW, and some devices are said to require only 1kW (and nothing else, no material inflow) to give such 1N of holding force. And are claimed to not require to push 1N on an opposite wall, contrary to a compression spring, or the BAE photon laser thruster with two spacecraft involved.
The issue is a non issue if someone can explain what kind of invisible source of energy is involved. But calling such a device a drive is misleading, this is a sail, or a generator, but not a drive.
-> Yes : and there is no conservation of energy issue because when it is pushing 1N forward, the device has to push 1N the opposite direction on the floor or opposite wall, that is the effect is just spurious coupling with local environment, making it as irrelevant for space thrust as an astronaut pushing on a wall of a spacecraft while its feet push on the opposite wall.
-> No : it is possible to save conservation of energy but then we have an "absolute-o-meter" that goes in contradiction with relativity (as there is in principle no way for a closed system to know whether it travels at constant 0km/s or at constant 10km/s : relative to what ?) and in contradiction with the most interesting space applications that require both a high thrust/power and a big velocity "range", while we would then have the product of two bounded by 1 : 1N/kW bounded within 1km/s (too small a velocity range for significant space missions) or 0.1N/kW bounded within 10km/s or or 0.01N/kW (too small an efficiency to make difference with ion thrusters) bounded within 100km/s.
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#2304 by SteveD on 27 Jan, 2016 23:09
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In other words, as shown by Frobnicat, if the EM Drive works as proposed by Shawyer and others, and you can really get force proportional to power, then eventually one does NOT need any solar power, as free-energy can be produced by a couple of rotating EM Drives.
I suspect that the EMDrive, and various EM free energy devices that surprisingly seem to work, turn on some yet unknown method for pulling heat out of the environment. The electrical input might be constant but, perhaps, electricity + heat drawn from the environment is not.
You mean, like some environmental cooling would be observed somewhere around an operating EM drive ? Then you are trading 1st principle issues for 2nd principle issues. By 2nd principle, the energy content of a single heat bath (at a single given equilibrium temperature) can't be transformed into useful (mechanical) energy.
To explain where apparent excess energy comes from (apparent excess as would be seen when operated above a certain velocity, if it could) your idea of "pulling heat from environment" would require at least two heat bath at different temperatures, or an environment far from thermal equilibrium; making the device a thermal engine (and the spent electric power just an auxiliary "catalyzer"). As for space application, do you see two different temperatures heat bath in deep space, ready to interact with "catalyzing" enclosed resonating microwaves to make up a thermal engine ?
To be added to the many strange things requested to be investigated in the vicinity of the device (radiations, space-time warps...) : cooling of the hot dark matter flow.
Given that the device loses efficiency when both inside and outside are in vacuum I think you might have an interesting point here. -
#2305 by frobnicat on 28 Jan, 2016 00:00
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.../...
In a photonic laser thruster, each time the laser is reflected its frequency (Energy) drops. Call it red shift, or Doppler effect. So the photon can't keep its energy forever; finally all its energy are transferred to the two spaceship and that's the end of it.
Not sure this is accurate. The PLT concept efficiency is hard to analyse since the lasing medium is in the path of the recycled photons. From Wikipedia article on PLT (largely a copy past of one of BAE's paper, fully available here)QuoteOne of the factors that limit the maximum obtainable velocity of the accelerating mirror and its accommodating spacecraft is limited by the Doppler shift of the bouncing photons. Doppler shift effect on the active resonant cavity behavior is an extremely complicated issue.
But in the case of a passive cavity (Herriott cell : no interferences) we can understand that one injected photon when it hits a mirror can either be absorbed (energy converted to heat in the mirror lattice) or reflected, and in the later case there is no reason it is redshifted or blueshifted when the 2 mirrors are perfectly stationary wrt. each other (constant distance). There might be some slight shift due to thermal agitation of the lattice, but no more toward red than toward blue.
The thing in the formula above F=2NW/c with N "photon bounce number" and W injected power is that it is only valid for 2 mirrors perfectly stationary wrt. each other (constant distance). It is obvious, from conservation of energy, that there is an upper bound F<W/v where v is the relative velocity of the 2 mirrors, and that the above formula certainly can't hold for v>c/(2N), and more generally that F is a decreasing function of v (v counted positive for increasing distances between the 2 mirrors). I don't feel like deriving that, any taker ?
Intuitively :
v=0 => no shift
v>0 => redshift (photons lose energy on each bounce as the force applies in same direction as relative velocity)
v<0 => blueshift (photons gain energy on each bounce as the force applies in opposite direction to relative velocity)
In principle (with N high enough) it could be possible to recover the energy of two approaching spacecraft slowing down (due to the photon mediated force) by collecting photons of higher frequency than those injected : regenerative photonic breaking !
In the ideal case of perfect reflectivity (infinite N) and assuming no losses (which is obviously impossible because of the inherent diffraction leaks) a given amount of photons bouncing forever between the mirrors should behave as a compression spring : 0 net power consumption to exchange a force, but a potential energy that decreases when length increases.
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#2306 by spupeng7 on 28 Jan, 2016 00:04
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The proportional relationship between energy of motion and the square of its velocity is a relative one. It cannot be otherwise or it would impede our freedom of movement. When an emdrive is tested in space that relationship will have no relevance beyond getting folk over the hump of credulity which it invokes.
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#2307 by frobnicat on 28 Jan, 2016 00:33
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Quote
I suspect that the EMDrive, and various EM free energy devices that surprisingly seem to work, turn on some yet unknown method for pulling heat out of the environment. The electrical input might be constant but, perhaps, electricity + heat drawn from the environment is not.
QuoteThen you are not going to get a constant force (constant acceleration) from a given power input, and with this goes all those rosy calculations of going to the Stars... (or even to Pluto in a relatively short time frame). All based on crude extrapolations of experiments that have been run for only a few seconds at a time...
Something I have wondered about as well.
But if so, perhaps multiple EM Drive units in some sort of timed sequence would grant constant acceleration? Or would that require an unrealistically high number of units?
If one unit can thrust at .01N/kW for only 10s and needs "resting" for 29990s before it can get used again, then all it takes is 3000 units to have a compound system that at a given moment consumes 1kW and thrusts at .01N (as at a given moment only one unit is powered and the 2999 others are resting). So in the end this is a device 3000 times heavier, but that still thrusts at .01N/kW : that doesn't change the energy conservation issue that doesn't depend on mass of the system (nor acceleration)...
It was suggested (to circumvent the energetic issue) that maybe a given unit still needs power even while its no longer thrusting. So if we have 3000 units, only one thrusting .01N/kW at a time for 10s, but the other 2999 still needing 1kW while "reseting", then the compound system consumes 3000kW for .01N thrust overall, and then this is perfectly all right with CoE for a "drive". Which is just to say that, ahem, to make such ideas reconcile with energetic issue implies just scaling down the efficiency to that of a photon rocket ( in case anyone still has doubts
)
End of spamming session.
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#2308 by A_M_Swallow on 28 Jan, 2016 00:35
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If the formula ΔE = ˝ m (V22 - V12) still applies then all the stuff about free-energy turns out to have been a red herring.
The rotation test will show this. Given an input of constant energy per second the acceleration per second reduces; after friction and air resistance have been allowed for.
Acceleration per second ?
I guess you mean just acceleration, as in "Given an input of constant energy per second the acceleration reduces". Thing is, I don't know how many time I'll have to repeat (probably as long as I care), the energy conservation issue does not depend on acceleration. Also making irrelevant considerations on kinetic energy.
{snip}
Thinking about it I should have said acceleration each second.
For constant energy going in the acceleration produced reduces as the velocity increases.
Just the latest variant on why railway trains pulled by steam engines have a top speed. -
#2309 by Rodal on 28 Jan, 2016 00:53
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EM Drives and Warp Bubbles
These guys would have benefited from reading the EM Drive threads at NSF because they do not seem to be aware of the "EM Drive Achilles heel": the free-energy issue associated with the EM Drive. They even discuss the EM Drive constantly accelerating to speeds near the speed of light , but they never even once discuss the free-energy issues.
Although this is basically a re-telling of a lot of things we have been discussing about Shawyer and NASA Eagleworks, still quite entertainingQuotePublished on Jan 20, 2016
We discuss the controversial EmDrive and reports of a warp bubble being detected inside it.
Part 2 of Off-World/Off-Topic Episode 6: How Might We Travel the Galaxy
Credit to oval999 @ Reddit for finding this recent (Jan 20, 2016) video -
#2310 by frobnicat on 28 Jan, 2016 01:45
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If the formula ΔE = ˝ m (V22 - V12) still applies then all the stuff about free-energy turns out to have been a red herring.
The rotation test will show this. Given an input of constant energy per second the acceleration per second reduces; after friction and air resistance have been allowed for.
Acceleration per second ?
I guess you mean just acceleration, as in "Given an input of constant energy per second the acceleration reduces". Thing is, I don't know how many time I'll have to repeat (probably as long as I care), the energy conservation issue does not depend on acceleration. Also making irrelevant considerations on kinetic energy.
{snip}
Thinking about it I should have said acceleration each second.
For constant energy going in the acceleration produced reduces as the velocity increases.
Just the latest variant on why railway trains pulled by steam engines have a top speed.
I still don't see the point of mentioning the unit of second when relating to acceleration since classically this is an instantaneous vector at a given time. On the other hand "constant energy going in" would make more sense with "per second", i.e. simply power (instantaneous). And since acceleration depends on all forces (on a rigid body) we can have forces without acceleration (my personal battle today). Not wanting to sound too much professorial (but hey, I'm a professor) just trying to express that in an academic manner :
"For constant power in the force exerted by the effect reduces as the velocity increases"
Which I would agree applies well for the force of a steam powered locomotive on rails. Notice that at top speed the acceleration is 0 even while the force (loco on rails) is not 0, since it is struggling against another force : aerodynamic drag.
The rails do define a frame of reference. What is the frame of reference for an hypothetically non-frame-invariant EM drive effect ?
If it's not the lab's wall, it is not the Earth either. What are the typical velocities of naturally occurring frames (CMB radiation, dark matter flow, solar neutrinos...) relative to lab's wall ? Typically hundreds of km/s. That makes any non-frame-invariant EM drive effect much more dependent on orientation relative to the stars than velocity relative to lab walls (by 3 orders of magnitude at least).
If it's the lab's walls then it means that the device is actually pushing on the lab's walls, i.e. there is no EM drive effect to speak of, at least nothing usable as space propulsion as there is no nearby walls in space to push on. And obviously we don't wan't to push on the walls of the spacecraft in one direction to pretend that the device is thrusting in the other. Unless the EM drive is pushing itself out of the spacecraft... mmh, interesting advanced concept of the day : don't eject propellant from a thruster, directly let propellantless thrusters eject themselves !
So I would say that if a rotation test shows that "for constant power in the force exerted by the effect reduces as the tangential velocity increases" then it would clearly show the effect is due to spurious coupling with the immediate surrounding, as there is no other credible natural frame with velocity wrt Earth < tangential velocity of rotation.
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#2311 by Bob Woods on 28 Jan, 2016 02:25
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EM Drives and Warp Bubbles
These guys would have benefited from reading the EM Drive threads at NSF because they do not seem to be aware of the "EM Drive Achilles heel": the free-energy issue associated with the EM Drive. They even discuss the EM Drive constantly accelerating to speeds near the speed of light , but they never even once discuss the free-energy issues.
Although this is basically a re-telling of a lot of things we have been discussing about Shawyer and NASA Eagleworks, still quite entertainingQuotePublished on Jan 20, 2016
We discuss the controversial EmDrive and reports of a warp bubble being detected inside it.
Part 2 of Off-World/Off-Topic Episode 6: How Might We Travel the Galaxy
Credit to oval999 @ Reddit for finding this recent (Jan 20, 2016) video
It's like sophomore year in college kicking ideas around the dorm room
Those were the days....
Dave, these guys could have at least mentioned your name. -
#2312 by Rodal on 28 Jan, 2016 02:48
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...
I still don't see the point of mentioning the unit of second when relating to acceleration since classically this is an instantaneous vector at a given time. On the other hand "constant energy going in" would make more sense with "per second", i.e. simply power (instantaneous). And since acceleration depends on all forces (on a rigid body) we can have forces without acceleration (my personal battle today). Not wanting to sound too much professorial (but hey, I'm a professor) just trying to express that in an academic manner :
"For constant power in the force exerted by the effect reduces as the velocity increases"
Which I would agree applies well for the force of a steam powered locomotive on rails. Notice that at top speed the acceleration is 0 even while the force (loco on rails) is not 0, since it is struggling against another force : aerodynamic drag.
The rails do define a frame of reference. What is the frame of reference for an hypothetically non-frame-invariant EM drive effect ?
If it's not the lab's wall, it is not the Earth either. What are the typical velocities of naturally occurring frames (CMB radiation, dark matter flow, solar neutrinos...) relative to lab's wall ? Typically hundreds of km/s. That makes any non-frame-invariant EM drive effect much more dependent on orientation relative to the stars than velocity relative to lab walls (by 3 orders of magnitude at least).
If it's the lab's walls then it means that the device is actually pushing on the lab's walls, i.e. there is no EM drive effect to speak of, at least nothing usable as space propulsion as there is no nearby walls in space to push on. And obviously we don't wan't to push on the walls of the spacecraft in one direction to pretend that the device is thrusting in the other. Unless the EM drive is pushing itself out of the spacecraft... mmh, interesting advanced concept of the day : don't eject propellant from a thruster, directly let propellantless thrusters eject themselves !
So I would say that if a rotation test shows that "for constant power in the force exerted by the effect reduces as the tangential velocity increases" then it would clearly show the effect is due to spurious coupling with the immediate surrounding, as there is no other credible natural frame with velocity wrt Earth < tangential velocity of rotation.
Prof. Frobnicat, Paul March says that the EM Drive tests at NASA can be explained by Woodward's Mach Effect theory (as he calls it "the other side of the coin having Dr. White's Quantum Vacuum theory on the other side).
Prof. Woodward explains NASA's results as being due entirely to the asymmetric placement of the dielectric insert, constituting a Woodward Mach Effect, and that NASA's test without a dielectric giving no force confirms Prof. Woodward's expectations.
Now, this is how Prof. Woodward explains the Conservation of Energy (Overunity argument) for his theory (he wrote this last November 2015, barely a couple of months ago):
http://ssi.org/epi/Over-Unity_Argument_&_Mach_Effect_Thrusters.pdf
Your comments on Prof. Woodward's paper on Conservation of Energy, would be appreciated, and most relevant, because, again, Paul March at NASA has stated that Prof, Woodward's theory might explain the test results for the EM Drive at NASA.Quote from: Prof. WoodwardWe routinely hear a criticism of METs based upon an argument that claims: if a
MET is operated at constant power input for a sufficiently long time, it will acquire
enough kinetic energy to exceed the total input energy of operation. Assuming this
argument to be correct, critcs assert that METs violate energy conservation as the ratio of
the acquired kinetic energy to total input energy exceeds “unity.”
Contrary to this “over-unity” assumption, this argument is based on flawed
physics and, consequently, wrong. The fact that the argument applies to all simple
mechanical systems (in addition to METs) should have alerted critics to their mistake.
But it didn’t. So, a dumb idea that should have been quickly buried is still with us. The
purpose of this essay is to carry out a long overdue burial.
In brief, the “over-unity” argument asserts that a constant input power into a MET
will produce a constant thrust (force). This, in turn, produces a constant acceleration of
any object to which the MET is attached. The constant acceleration produces a linearly
increasing velocity of the object. The kinetic energy of the object, however, increases as
the square of the velocity. This means that at some point, the kinetic energy of the object
will exceed the total input energy used to produce the thrust as that only increases
linearly with time. Critics then claimed that this purported behavior constituted violation
of energy conservation and proposed it as a fatal critique of Mach Effect thrusters. Note,
however, that the argument applies to all systems where a constant thrust produced by a
constant input power produces motion -
#2313 by Tetrakis on 28 Jan, 2016 03:59
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The evidence is clear that the EMDrive as described by all major investigators is a free energy device. This has been shown again and again in these threads. Typically new posters (or some grumpy old ones who can't take the hint) come in and try to show that it isn't a free energy device using bad physics or handwaving, and then knowledgeable posters painstakingly prove that it is over the course of several pages.
The reason this thread is in the "New Physics for Space Propulsion" section is that there is a broad consensus among those with expert knowledge in mathematics and physics that the EMDrive, as described by its proponents, is a free energy device and therefore, if it does work, "new physics" would have to be developed which would describe how it works. Can a statement to that effect just be included in the thread's original post, and these ad-nauseum debates over solved math be relegated to other venues? -
#2314 by ThinkerX on 28 Jan, 2016 05:57
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Ok, step by step, with the little that is known.
The EM units that have produced 'thrust' have all (?) used magnetrons. Magnetrons are messy - they spew out energy over multiple frequencies. If, say a regular radio transmission were a rifle, then a magnetron would be a wide angle shotgun. (Is this a fair comparison?)
Next, as I understand it, microwave radiation in symmetrical cavities, closed or not, behaves in a well predicted manner. Multiple texts, papers, and the likes of microwave ovens attest to this. No indicators of physics defying 'thrust' in any of these cavities. But, the EM Drive is a sealed frustum - an irregular shape. If I remember right, most of a year ago, Doctor Rodal concluded the ideal angle for the sides would be on the order of 30-33 degrees. Shawyer's hands on engineering efforts support this.
So, if the magnetron is in the 'big end,' or feeding microwave energy into the big end, we have a large amount of microwave energy entering a space that grows progressively narrower towards the 'small end.' With the 'shotgun comparison,' might this not be the equivalent of putting a funnel over the end of the barrel, forcing the pellets closer together, instead of scattering outward? Might this not also lead to microwave collisions? And would these collisions, if occurring, result in a net energy gain?
Another thing. 'Photon bouncing.' Except, as I understand it, its not really a 'bounce.' Instead, the photon strikes, is absorbed, and then re-emitted. In some instances, though, the photons are not re-emitted, but instead converted to thermal energy (heat). And EM Drive experiments are all plagued with thermal effects.
So, a very screwy thought:
photon hits plate on small end and is absorbed.
But, instead of being re-emitted, photon is reformed, INSIDE the plate, as 'photon-with-actual-mass.' Except it is no longer traveling at C, and instead is decelerating very swiftly, gaining real mass while transforming into thermal energy. For a very tiny instant, the former photon is a particle with mass transferring momentum even as it decelerates and collapses into thermal energy. Said real mass vanishes upon thermal transformation.
In faint support for this, I vaguely recollect mention from analysis of the MEEP models that the 'interesting stuff' was all happening at the small end.
Perhaps this 'photon becoming particle with mass' thing is dependent upon both the mad array of microwave radiation and the temperature of the end plate. Temperature gets too hot, or something (unknown) with the microwave mix, and this effect doesn't happen.
Ok, I better quit before somebody throws a physics text at me.
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#2315 by RFPlumber on 28 Jan, 2016 06:22
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...
Now, this is how Prof. Woodward explains the Conservation of Energy (Overunity argument) for his theory (he wrote this last November 2015, barely a couple of months ago):
http://ssi.org/epi/Over-Unity_Argument_&_Mach_Effect_Thrusters.pdf
...
Ok, I read it twice It all makes sense up until his equation #15 (t = t^2). But can someone, please, explain his "solution" where he concludes that:Quote from: Prof. Woodwardis it possible to do a correct calculation of the sort that
critics did that does not lead to wrong predictions of the violation of energy conservation?
By paying attention to the physics of the situation, yes, such a calculation is possible. We
take Equations (9) and (13) as the integrations for the constant force work equation and
the figure of merit equation respectively. We know that, starting from t = 0, if we let the
integration interval t get very large, the work equation integral will first equal and then
exceed the energy calculated by the figure of merit equation. So we require that t be
sufficiently small that this obvious violation of energy conservation does not happen.
Should all of the input power be transformed into kinetic energy, we would choose the
positive root of the solution of Equation (15). ... We then choose the value of t for
the time differential that for all intervals to be summed to get the energies for the two
methods. That is, we note what should be obvious physics for this situation: the energies
added to the two sums in every differential time interval are always in the same ratio as
they are in the very first interval because the only invariant velocity that exists in this
case is the one of instantaneous rest at the outset of each interval...
Does he suggest that to the outside observer the MET thruster velocity will no longer be growing linearly? Or does he imply something else? The point appears to be that the CoE is not violated during the very first interval, so it will not be violated during the subsequent intervals either (because ...?)
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#2316 by mwvp on 28 Jan, 2016 07:57
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I think most of us are trying to look at the emdrive from the perspective of fundamental physics. Everything in this realm is pretty well buttoned up
...
a couple of key fundamentals have eluded us. Having no theory yet, I can only believe these are the the areas where the emdrive effect might reside. I cannot see fundamental physics working to explain it.
I used known physics when I posit that the lower-sideband EM momentum is exhausted as heat, resulting in a momentum imbalance and thrust. It seems appropriate to first investigate what tested and established physics may be in play before resorting to the extraordinary.
Why no comments or cites of my NEPSOP/Nibiruian Conjecture? I find it discouraging and troubling. I refrain from idle chatter here, preferring research instead. Why am I the only one interested in dispersion and dynamics of acceleration and Doppler effects? It pertains to CoE/CoM and thrust, tuning at/near cutoff and the dynamics of the frustrum itself.
See here!
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1472941#msg1472941
Why isn't there more reverse-engineering of more of Shawyer's work, rather than discussing Cones, Q, and return loss ad-nausem? I think it is remiss of us not to consider most if not all of what he's written, and then understand the salient properties and phenomena. We find him discussing and employing a high-Q cone tuned at cutoff. So some of us set off to do likewise, while pretty much ignoring what he's said about motor/generator effects and CoE through a Doppler mechanism. His central point, even if bogus, is the difference in forward and reverse group velocity which is a property of the frustrum anisotropic dispersion. Anisotropic dispersion, anisotropic Doppler spreading, and asymmetrical spectral dissipation seem connected....Herein lies the basis for much of the emotion about the emdrive. Does one believe new physics is even possible? IMO you would almost have to considering what we observe and cannot yet explain...gravity and the expanding universe.
Moreover I believe its about attitude, and having a certain sort of existential faith. Does one believe, have faith, that the existence is knowable, understandable, reasonable, and that one's efforts to create our meaning through purpose are worthwhile? Does one have enough faith to invest time and treasure, suffering "the pidgeons from h*ll" (as some refer), messing all over their efforts? Ah, to 'start again at your beginnings, and never breath a word about your loss'.
At Reddit an indictment of delusion and counsel of despair was posted about perhaps one of the most faithful (consequently ironically, least credible) who was among us. Perhaps correctly, perhaps not. Yet if there wasn't the faith of those willing to pay the price, would there be any great achievements or progress, save for dumb luck? Whose to know till after the hand's played?
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#2317 by mwvp on 28 Jan, 2016 08:15
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As for the effect of Q, I ask : has anyone ever noticed a gravity or acceleration induced significant (measurable) change of Q, or of resonant frequency, or even the slightest phase shift, with radio frequency excited cavities, ever ? I'm not talking here of change in geometry of cavity deforming under such acceleration, but of direct acceleration effects on the resonant wave at the scales (λ and sizes) typically involved with RF cavities. I know there are optical gyroscope, but this is not same λ. Sagnac effect on microwaves, really ? I'd like to see some rough simple order of magnitude estimation to believe it's measurable at all (before it's supposed to act as mechanical actuator !)
At last, a great question! I have seen and I can dig up references to using lasers and dispersive fibers to measure gravitation. I'm presently studying the matter, dispersion and optomechanics.
http://arxiv.org/abs/1005.5467v1 - Doppler equation (Snell's Law) accounting for group velocity/index, see eq. 5.2.6
Now, A challenge for the adept photonicist!
How is an optomechanical photo-fridge like, and not like, an EM-Drive?
from http://arxiv.org/abs/1303.0733 pg 20
Coincidence? I think Not!
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#2318 by mwvp on 28 Jan, 2016 08:54
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Hope for the electromagnetically challenged
Disperse the darkness and dissipate the dismal at:
http://emlab.utep.edu/academics.htm
Video lectures and notes from the courses on electromagnetics, photonics and simulation.
Especially relevant:
http://emlab.utep.edu/ee5390em21/Lecture%2022%20--%20Slow%20waves.pdfQuote[Pg. 17](a) Shows perhaps the first slow light device. Slow light occurs most strongly near the cutoff of the waveguide where its dispersion is highest. (d) Group index is greatly enhanced using a photonic crystal waveguide.
The whole document is must-know stuff. More generally, the phase constant beta, of the complex propagation constant gamma, is greatest (EM propagates slowest; group index is greatest) is near cutoff where dispersion is highest. And group index is greatly enhanced in a microwave waveguide at cutoff too.
See. Told ya so
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#2319 by Chrochne on 28 Jan, 2016 09:15
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There was an EDIT from Monomorphic on the Optical / Laser EmDrive
"EDIT: Here is a close-up of the frustum shaped optical cavity."
http://i.imgur.com/axnxkRH.jpg
He also suggest some insight on why the EmDrive may work and he seems to be very open to answer on all questions.
" Q: I'm not sure if using light waves of 450nm will get you any results
The main hypothesis I am testing is if higher energy photons are more efficient at producing force in the emdrive.
Q: If I understood that relation between wavelength and internal cavity dimensions correctly, your frustum should be around 1 micrometer big.
Basically the emdrive is a microwave fabry-perot interferometer. It can be any length, so long as the end-plates are aligned to produce resonance. In fact, the larger the cavity, the higher the Q. The same is true in optics. I think the current sizes of frustums (and they are all over the place) are a consequence of the difficulty in fabrication of a larger metal frustum and the problems achieving resonance with microwave antennas. Using laser light that is coherent makes this simpler compared to trying to achieve optical resonance by placing a diffuse light source in a mirrored frustum.
That aside, and this has been discussed here before, some speculate that stacked arrays of micrometer sized optical emdrives will ultimately be the most efficient design. But at this point, fabrication of shaped microresonating cavities that small is beyond our capabilities. There are a few papers floating around though."
Source link is here: https://www.reddit.com/r/EmDrive/comments/42uzo7/opticallaser_emdrive_revealed/
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