Hopefully someone has enough patience to answer a couple of noob questions.1. Does any one know the input impedance of a frustum at resonance?If I remember right a parallel L C resonance circuit has a very high impedance at resonance and a series L C circuit has a very low impedance at resonance. Also if I remember right if the source impedance is not matched to the load impedance then most of the power is dissipated back at the source.2. For a given mode of operation has a relation ship between frequency and thrust been shown? I would guess that lower frequencies would require larger frustum dimensions to keep the same mode. Only NASA has given all the dimensions of the EM Drive necessary to calculate the mode shapes and natural frequencies.
What I understand (FWIW) is that the conical waveguide would have the same properties as a tapered microstrip; tapered impedance and velocity, except inverse. Waves are reflected off both ends, but with a shifted phase. A phase that creeps further with each reverberation...
...Actually a photon rocket is not really "propellantless" as it throws away photons. We could say that its exhaust is "pure energy" (in the sense that the exhaust particles have no rest mass), ...
2) Dielectric losses (not just due to the dielectric insert, but don't forget that it is not unusual to coat the interior of the EM Drive with a polymer coating to protect the copper, as was done by NASA Eagleworks).
Quote from: TheTraveller on 05/28/2015 09:32 pmQuote from: aero on 05/28/2015 09:15 pmQuoteEDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2 the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles? Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity? Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?Only the Experimental EM Drive used an internal small end dielectric. As a result, it had low Q and low thrust.The Demonstrator and Flight Thruster EM Drives are high Q and high thrust devices which did not use a dielectric.Shawyer says using a dielecrtic:1) increases loss,2) reduces Q,3) reduces thrust.His reported results back up that claimSo why the interest in dielectrics?First read this: http://forum.nasaspaceflight.com/index.php?topic=37642.msg1381229#msg1381229 which should answer your question. Besides that post, there are respectable people in the aerospace community, outside this thread who have the following opinion:1) NASA's experiments have falsified the results reported by Shawyer and NWPU2) NASA only measured thrust using a dielectric insert. No thrust measured without it.I think that it is important for NASA at some point to conduct further experiments without a dielectric and using a magnetron at higher power as they intended to do, to clarify this situation. I am not convinced about the test without a dielectric because:a) it was conducted very early in NASA's testing programb) only a test was performedc) it involved mode TE012 which, according to Brady's report, was difficult to replicate even with a dielectric, so they had to move on to mode TM212 which was never tested yet without a dielectric.
Quote from: aero on 05/28/2015 09:15 pmQuoteEDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2 the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles? Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity? Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?Only the Experimental EM Drive used an internal small end dielectric. As a result, it had low Q and low thrust.The Demonstrator and Flight Thruster EM Drives are high Q and high thrust devices which did not use a dielectric.Shawyer says using a dielecrtic:1) increases loss,2) reduces Q,3) reduces thrust.His reported results back up that claimSo why the interest in dielectrics?
QuoteEDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2 the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles? Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity? Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?
EDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2 the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.
Momentum of evanescent waves push particles: (they can also be used as tweezers)<<A single evanescent wave possesses a spin component,which is independent of the polarization and is orthogonal to the wave vector.Furthermore, such a wave carries a momentum component, which is determined bythe circular polarization and is also orthogonal to the wave vector. We show thatthese extraordinary properties reveal a fundamental Belinfante’s spin momentum,known in field theory and unobservable in propagating fields. We demonstrate thatthe transverse momentum and spin push and twist a probe Mie particle in anevanescent field. This allows the observation of ‘impossible’ properties of light andof a fundamental field-theory quantity, which was previously considered as ‘virtual’.>>http://arxiv.org/pdf/1308.0547
http://arxiv.org/pdf/1308.0547I think this is the key. I know all the math isn't quite there yet but it feels right and I will take the extra time to dig it out. Like the writer said we need to invent fire.
Forbes...http://www.forbes.com/sites/investor/2015/05/29/investor-alert-emdrive-could-make-uber-seem-about-as-disruptive-as-a-sweat-smear/2/The reason I’m writing this? If this force engine were to work, every industry you invest in will be turned upside down. Admittedly, this is a very early call. Inventing a time machine would be more dramatic than EmDrive but not a lot more. A force engine would be like inventing fire.
Flight Thruster build update:From the best photo of the Flight Thruster I could find and allowing for 2mm thick walls, to add thermal mass and reduce the rate of thermal expansion, the following internal Flight Thruster dimensions were obtained:Length: 138.6mmSmall diameter: 125.7mmBig diameter: 231.4mmApplying those to my spreadsheet generated:Df: 0.638Frequency: 3.85GHzMode: TE013I then asked Roger Shawyer did I get close? His reply:Df: 0.635Frequency: 3.9003GHzMode: TE013I'm VERY happy with that as my Rf gen can easily go to that frequency. Time now to finalise drawings and get some copper sheet laser cut.Roger also mentioned it is best to give the internal frustum surfaces a nice bright shinny polish. No need for Silver or Gold overcoats.
Quote from: frobnicat on 05/29/2015 10:46 pm...Actually a photon rocket is not really "propellantless" as it throws away photons. We could say that its exhaust is "pure energy" (in the sense that the exhaust particles have no rest mass), ...Yes, a photon rocket is propellant-less.The word "propellant-less" is a utilitarian, practical, business-like word. It originates from the fact that most of the weight of a rocket is the propellant and only a small percentage is the payload. It comes from the fact that there are huge earth-shattering practical benefits from any space propulsion that is propellant-less.For chemical rockets the payload fraction is often less than 1%For comparison, modern jet airliners have considerably higher useful load fractions, on the order of 45-55%.Propellant-less means that you don't have to carry on-board a huge reservoir of propellant in order to get propulsion. Thus Solar Sails are propellant-less propulsion. Electodynamic tethers are propellant-less propulsion.And a photon-rocket is propellant-less. For economic considerations (and $$$ talks), no on-board storage tanks for propellant ====> means "propellant-less"
Quote from: SeeShells on 05/30/2015 01:08 amForbes...http://www.forbes.com/sites/investor/2015/05/29/investor-alert-emdrive-could-make-uber-seem-about-as-disruptive-as-a-sweat-smear/2/The reason I’m writing this? If this force engine were to work, every industry you invest in will be turned upside down. Admittedly, this is a very early call. Inventing a time machine would be more dramatic than EmDrive but not a lot more. A force engine would be like inventing fire.I wouldn't be worried to much about that article in Forbes...There is a good analogy with 3dprinting, as far as being disruptive technology.Shawyer proves me wrong this year with his amazing new 2015 papers and tests...
OK Rodal 5th time.You said dE/dr = 0. Why?
...The practical significance of the geometrical attenuation constant α for the possible motion of the EM Drive is that the geometrical attenuation constant α is related to the fact that in truncated cone waveguides, a strict distinction between pure propagating and pure evanescent modes cannot be made. One mode after the other reaches cut-off in the truncated cone waveguide as it it gets closer to the small end of the truncated cone.See the recent discovery that:Momentum of evanescent waves push particles: (they can also be used as tweezers)<<A single evanescent wave possesses a spin component,which is independent of the polarization and is orthogonal to the wave vector.Furthermore, such a wave carries a momentum component, which is determined bythe circular polarization and is also orthogonal to the wave vector. We show thatthese extraordinary properties reveal a fundamental Belinfante’s spin momentum,known in field theory and unobservable in propagating fields. We demonstrate thatthe transverse momentum and spin push and twist a probe Mie particle in anevanescent field. This allows the observation of ‘impossible’ properties of light andof a fundamental field-theory quantity, which was previously considered as ‘virtual’.>>http://arxiv.org/pdf/1308.0547https://en.wikipedia.org/wiki/Mie_scatteringhttp://thermopedia.com/content/137/http://www.orc.soton.ac.uk/publications/theses/1460T_lnn/1460T_lnn_03.pdf
Intriguingly, this would appear to line up with comments of Shawyer's (at least as reported elsewhere here) that you can't measure the EMDrive thrust by putting it on a scale.