As far as I can tell, I am not the only one to have thought to a general relativity effect here. This paper uses a modified version of Einstein equations to explain what is going on in a conical resonant cavity without violating momentum conservation. The point is that the author uses a weak perturbation approximation and I do not know if this is fully justified.
The blasted thing goes faster and that is an increase in momentum. Unless you show where the opposite momentum is then it violates conservation of momentum. It can't get any simpler than that.
Satellite Propulsion Research Ltd (SPR Ltd) a small UK based company, has demonstrated a remarkable new space propulsion technology. The company has successfully tested both an experimental thruster and a demonstrator engine which use patented microwave technology to convert electrical energy directly into thrust. No propellant is used in the conversion process. Thrust is produced by the amplification of the radiation pressure of an electromagnetic wave propagated through a resonant waveguide assembly.
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.
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.
Quote from: sanman on 05/06/2015 02:52 amWarp 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.Regarding FTL - can I beg to differ?Everything in the universe warps space-time. A rocket at rest warps space-time. An accelerating rocket warps it more.IMHO - warping space-time to infinity still brings us to the speed of light because the speed of gravity (the warp) is limited to c. The EM Drive has nothing to do with FTL and I personally don't think FTL exists; in my mind the speed of light is the speed of reality.http://en.wikipedia.org/wiki/Speed_of_gravity
So the crux of the issue for me, is that photons and matter particles behave differently, and are Apples & Oranges which cannot be judged by the same standards: When you fully drain the momentum of a particle of propellant/matter (wrt your reference frame), then its velocity drops all the way down to stationary - but when you fully drain a photon of its momentum (wrt your reference frame), then it drops out of existence (ie. fades to nothing), because it loses energy rather than losing velocity.So:Photon Propellant != Matter PropellantMatter is persistent, and you can see that exhaust hanging around after it's left the rocket.Photons are not persistent, so they can disappear and leave you scratching your head about who/what was pushing your rocket to begin with.
....Todd,It is exciting to read your explanation about exponentially decaying waves that have been squeezed beyond their cut-off diameter in the waveguide. You write very clearly.It's great that you found your way into this thread Please see the following reference (https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-17-1-34&id=175583, click "Get PDF" to download the paper for free):It is shown that all modes run continuously from travelling waves through a transition to an evanescent (exponentially decaying) wave region and the value of the attenuation increases as they approach the cone vertex. A strict distinction between pure travelling waves and pure evanescent (exponentially decaying) waves cannot be achieved for conical waveguide. One mode after the other reaches cutoff in the tapered hollow metallic waveguide as they approach the cone vertex.Unfortunately, this analysis is for an open waveguide, not for a closed cavity, but the fact that a strict distinction between pure travelling waves and pure evanescent waves cannot be achieved for a conical waveguide, also has implications for modes approaching cutoff in the truncated cone cavity. ADDENDUM:One thing that has not been explored is whether these truncated cones are being prematurely ended towards the cone vertex. The tested designs are almost cylindrical.Roger Shawyer has progressively (but very slowly with time) increased the cone angle of his truncated cones, culminating in the superconducting design he unveiled last October 2014. NASA Eagleworks and Yang in China have truncated cone designs that look like earlier Shawyer designs, with smaller cone angles.For reference. the tangent of the cone's half angle thetaw and the cone's half angle thetaw, in ascending order, for the following cases are:(Notice how Shawyer progressively increased the cone's half-angle, with time, in his experimental designs, by a factor of 7 in the tangent of the half-angle)Example (and geometry) { Tan[thetaw],thetaw (degrees) }Shawyer Experimental {0.104019, 5.93851}Shawyer Fligth Thruster {0.19086, 10.8055}Shawyer Demo {0.219054, 12.3557}NASA Eagleworks frustum {0.263889, 14.7827}Egan's example {0.36397 , 20}Prof. Juan Yang (2014) {0.4538, 24.4 }Shawyer Superconducting 2014 {0.7002, 35}The people looking at running experiments here are (understandably) also looking at earlier designs with small cone angles and prematurely terminated before reaching the vertex. The group from a university was looking at running experiments with perfectly cylindrical geometry.Given the latest write-up by Shawyer (concerning his choice of R1 being too large) it appears that what you are bringing up concerning modes near cutoff has not yet been appreciated or explored, as the researchers are not focusing on general wave solutions in the complex plane containing simultaneously both real and imaginary components.Best regards, PS: @aero has valiantly attempted to run a full analysis, of general waves, containing simultaneously both real and imaginary components, using MEEP. Unfortunately MEEP is finite difference code and hence he has only been able to run 2-D simulations (due to computer time limitations). It is known that this problem (truncated cone) is 3-D, as a 2-D analysis cannot simulate very important features of the geometry. The MEEP solutions have also been very difficult to interpret, because of the lack of suitable post-processing software to explore the solutions.@Mulletron envisioned a completely conical EM Drive, terminating at the vertex (at the beginning of the thread when we were all trying to explore all possibilities with an open mind). A perfect cone may not be the best solution because in a perfect cone ALL modes are cut-off and hence there will not be any resonance, but in reality it is impossible to have a perfect cone, since the vertex will always terminate with a finite dimension (not a point). I explored some time ago some geometries, and it looks like there is plenty of room to explore truncated cones that terminate at different distances from the cone vertex.
So the crux of the issue for me, is that photons and matter particles behave differently, and are Apples & Oranges which cannot be judged by the same standards: When you fully drain the momentum of a particle of propellant/matter (wrt your reference frame), then its velocity drops all the way down to stationary - but when you fully drain a photon of its momentum (wrt your reference frame), then it drops out of existence (ie. fades to nothing), because it loses energy rather than losing velocity.So:Photon Propellant != Matter PropellantMatter is persistent, and you can see that exhaust hanging around after it's left the rocket.Photons are not persistent, so they can disappear and leave you scratching your head about who/what was pushing your rocket to begin with.Maybe the experimenters need to vary the angles of that waveguide, so that you have a series of cases where you tap greater and greater amounts of energy from the photons. The steeper and longer the waveguide, the more energy you're draining (transferring to your rocket/apparatus as momentum). The shallower the waveguide, the less energy you're draining (transferring to your rocket/apparatus as momentum).Shouldn't the experimenters be trying to measure the energy of the photons that leave the resonant cavity via the waveguide exit? Wouldn't establishing some sort of correlation there be useful for proof of principle??
What you are describing is just red shift. I think. It is very confused.In an ordinary rocket the propellent has no momentum with respect to the rockets reference frame. You burn it and give it a huge momentum with respect to the rockets reference frame. In reaction the rocket gets a huge momentum in the other direction. In the original reference frame they both have huge momentum gain in opposit directions. That is how conservation of momentum works.A photon rocket is not much different. A photon has some amount of momentum despite being massless. As the photon rocket accelerated away you would see the photons slowly red shifting. But you could not be "scratching your head about who/what was pushing your rocket" until it reached the speed of light which would be never. Instead you would be scratching your head wondering what vaporized the asteroid behind you. Hint: the photons didn't just disappear. A photon rocket has an exhaust that is hotter and more destructive than any other kind of rocket giving the same thrust.
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.
Quote from: ppnl on 05/06/2015 05:28 amWhat you are describing is just red shift. I think. It is very confused.In an ordinary rocket the propellent has no momentum with respect to the rockets reference frame. You burn it and give it a huge momentum with respect to the rockets reference frame. In reaction the rocket gets a huge momentum in the other direction. In the original reference frame they both have huge momentum gain in opposit directions. That is how conservation of momentum works.A photon rocket is not much different. A photon has some amount of momentum despite being massless. As the photon rocket accelerated away you would see the photons slowly red shifting. But you could not be "scratching your head about who/what was pushing your rocket" until it reached the speed of light which would be never. Instead you would be scratching your head wondering what vaporized the asteroid behind you. Hint: the photons didn't just disappear. A photon rocket has an exhaust that is hotter and more destructive than any other kind of rocket giving the same thrust.But I'm not talking about light that the rocket-rider would see, I'm talking about light that the guy back on the launchpad would see. The launchpad guy would see the photon exhaust as red-shifted for a different reason, which is that the photons would have transferred some of their energy (momentum) to the rocket - ie. those photons are coming out of the rocket with lower energy than what they had when they were originally created inside the cavity. That's not really a red-shift.
Hmm, so let me maybe replace the photon rocket idea with a solar sail.So you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.But suppose your sail could experience multiple collisions with each photon that came out of the emitter? So that's the waveguide that's allowing this to happen. And each of those collisions is transferring some momentum. So the sum total of all momentum that a photon can transfer to the waveguide can't exceed the original momentum of the photon when you first produced/emitted it. So net thrust is zero because of the anti-thrust from producing the original photon.Hmm, so now it doesn't work again...I better go ask GoatGuy.