The latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?Thanks and have a nice weekend because this Monday will really be interesting.PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.
Quote from: Chrochne on 07/25/2015 09:59 amThe latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?Thanks and have a nice weekend because this Monday will really be interesting.PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.I've read that even with low thrust it would still be useful for getting around the Solar System?
Quote from: Chrochne on 07/25/2015 09:59 amThe latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?Thanks and have a nice weekend because this Monday will really be interesting.PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.I'm concerned with the title of the article EM Drive getting to Pluto in 18 months being so at odds with what I heard Prof. Tajmar's experimental data had obtained a couple of months ago: less than 50 microNewton for hundreds of watts inputPower, in a partial VacuumTo put this in context, see: http://emdrive.wiki/Experimental_Resultsif this is compared with Yang 270,000 microNewtons for 300 watts inputPower in AirShawyer 174,000 microNewtons for 400 watts inputPower in AirNASA 55 microNewtons for 50 watts inputPower in Airit can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower Vacuum. Unless Prof. Tajmar has obtained much higher numbers than what he got a couple of months ago, on the contrary, these data is going to be seen by John Baez and Sean Carroll and others as showing what they already called "the incredibly shrinking force" as the thrust/InputPower, instead of increasing with further examination progressively shrinks.I don't understand how raising the hopes sky-high with "reaching Pluto in 18 months" is commensurate with new results showing a thrust that is orders of magnitude smaller than what others previously claimed.On the contrary, raising the hopes sky-high (in another EM Drive forum people are already posting that Tajmar's presentation is going to be "huge" news) can only serve to further raise skepticism. It would have been much better if people would have waited to see what Tajmar actually presents.
it can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower Vacuum.
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Quote from: SeeShells on 07/25/2015 08:53 amThe EMDrive has shown a red flag byAir=thrust, No air=little thrustAir = acoustic vibration on big end plate greater than small end plate (enables switch from IDLE to MOTOR mode).No air = no acoustic vibration (hard to get out of IDLE mode).
The EMDrive has shown a red flag byAir=thrust, No air=little thrust
Quote from: X_RaY on 07/24/2015 10:04 pmTo get more control about the transmission factor into the resonator and get impedance matching against the magnetron there may be a (relative) simple way.For that one need a 3 stub tuner, 50 Ohm broadband load, two high voltage schottky diodes and a xy-oscilloscope.If the coupling is realized as a waveguide(the magnetron is), it is possible to use 2 schottky in a small distance(i think the needed was 45 deg? of phaseshift inside the waveguide) to get I,Q signal. Power schottky are available for high voltages (for example 170V) but it would be important to use a verry short length of the schottky stub-antenna inside the high power waveguide otherwise the magnetron kill the diode.The signals on the diodes will generated by signal mixing of the forward(45deg) and reflected(also 45deg) wave component. That results in 2 canals with 90 deg phase difference --> Inphase and QuadratureUse a xy-oscilloscope, put the load at the end of the magnetron and tuner line (unused tuner, screws as out as possible). Put the RF on. Measure the Voltage of the diodes. Tune both channels to be null Volt DC with the scope offsets. Switch the RF off.After this, place the waveguide antenna feed onto the cavity.Switch the RF on again and use the waveguidtuner to get impedance matching (the scope have to show null Volts for both channels as you are calibrated before) tadaaa Z=~50 Ohm Tuner:Take a (rectangular) waveguide for the frequency of interest.Calculate the wavelength using the dimensions of your waveguide.Drill 3 holes into the waveguide at the middle of the a-axis, the first is random, the next two have to be in a distance of, i think it was for example(take a look of some design rules..) 1*lambda/8, 3*lambda/8, or 5*lambda/8 or something like that. Take some screws and put they into the holesDetector diodes:Same game, drill a hole (random) in a waveguide (some half wavelength away from the tuner) and a second in a distance of Lambda/8 to the first (or lambda/4? can't remember exactly) than stick one wire of the diode into the hole and fix it. This technique is also be used in gunn oscillator transceivers (CW).I have tested the procedure for commercial µW-sensors, it will work good luck and have fun while testingThis is a great idea, and will indeed work, BUT. It uses a "pure" 50 ohm load as the "reference". The frustum is very likely nowhere near a 50 ohm load, nor is that the load that the magnetron is expecting to see for maximum radiated power ( best match) in all likelyhood.My own thought is that trying to design a cavity (frustum) "tuned" to a spectrally noisy source like a magnetron is a thankless task. How about designing the cavity (frustum) to a "best practices" standard. OFHC walls and ends, internally silver plated. Later you could even niobium plate it for superconducting tests. I'd consider making the frustum capable of at least 60 PSI internal pressure, or internal hard vacuum for later filling with arc suppressors, maser gain media for higher frequency designs, or testing under vacuum. The source would be a klystron (or other high power/high gain/relatively low phase noise amplifier of your choice - NOT a noisy oscillator like a magnetron), coupled to the frustum via a crossguide or other well matched dual-directional coupler. This would almost take the frustum out of the equation, leaving you with a microwave source, driving the klystron, that could be a good lab quality microwave synthesizer. This gives you control over frequency, modulation (AM/FM,perhaps even phase), and power. The coupler gives you direct forward and reflected power, allowing direct match and Q measurement via power meters or spectrum analysis (or even a VNA), and the sampled signals could be used to directly phase or frequency lock the synthesizer at any point of interest (like measured thrust). Most modern lab quality synthesizers can be easily phase locked to a coupler output with a bit of signal conditioning. I know this kind of turns the approach "on its head". Experimenters seem to be trying to make the perfect frustum for a very imperfect source. I think SeaShell has recognized this by making a frustum that can be relatively easily modified, and may negate atmospheric effects. I submit it's the microwave source that needs control, not the frustum. In other words, there's nothing "magic" about a magnetron. There may be something about the inherent modulation of an easily available magnetron (they're inherently very low Q oscillators, and amplitude modulate 100% at 50 or 60 Hertz if they are powered by a microwave oven supply). This could be (relatively) easily tested with a fully controllable source, with the frustum itself as a "fixed" element in the experimental protocol.Just some thoughts.
To get more control about the transmission factor into the resonator and get impedance matching against the magnetron there may be a (relative) simple way.For that one need a 3 stub tuner, 50 Ohm broadband load, two high voltage schottky diodes and a xy-oscilloscope.If the coupling is realized as a waveguide(the magnetron is), it is possible to use 2 schottky in a small distance(i think the needed was 45 deg? of phaseshift inside the waveguide) to get I,Q signal. Power schottky are available for high voltages (for example 170V) but it would be important to use a verry short length of the schottky stub-antenna inside the high power waveguide otherwise the magnetron kill the diode.The signals on the diodes will generated by signal mixing of the forward(45deg) and reflected(also 45deg) wave component. That results in 2 canals with 90 deg phase difference --> Inphase and QuadratureUse a xy-oscilloscope, put the load at the end of the magnetron and tuner line (unused tuner, screws as out as possible). Put the RF on. Measure the Voltage of the diodes. Tune both channels to be null Volt DC with the scope offsets. Switch the RF off.After this, place the waveguide antenna feed onto the cavity.Switch the RF on again and use the waveguidtuner to get impedance matching (the scope have to show null Volts for both channels as you are calibrated before) tadaaa Z=~50 Ohm Tuner:Take a (rectangular) waveguide for the frequency of interest.Calculate the wavelength using the dimensions of your waveguide.Drill 3 holes into the waveguide at the middle of the a-axis, the first is random, the next two have to be in a distance of, i think it was for example(take a look of some design rules..) 1*lambda/8, 3*lambda/8, or 5*lambda/8 or something like that. Take some screws and put they into the holesDetector diodes:Same game, drill a hole (random) in a waveguide (some half wavelength away from the tuner) and a second in a distance of Lambda/8 to the first (or lambda/4? can't remember exactly) than stick one wire of the diode into the hole and fix it. This technique is also be used in gunn oscillator transceivers (CW).I have tested the procedure for commercial µW-sensors, it will work good luck and have fun while testing
This is a good news bad news article for sure. Without knowing the mechanical and electrical configuration, its hard to judge...However, for a lab that is known for eliminating measurement "noise", this experiment appears to rise above it in a vacuum; meaning this is not a propellant force, it is a propellantless force.The door has been cracked open. Maybe one of us can help walk through it...
...If anyone who is much better than me at this want to jump in feel free otherwise it's gonna be awhile.
Quote from: SeeShells on 07/25/2015 02:04 pm...If anyone who is much better than me at this want to jump in feel free otherwise it's gonna be awhile. Look at the mean free path : https://en.wikipedia.org/wiki/Mean_free_path and the vacuum https://en.wikipedia.org/wiki/Vacuum Wikipedia articles:NASA and Tajmar tested (5*10^(-4) to 5*10^(-6) Torr) under high vacuum defined as (10^(−3) to 10^(−9) Torr) hence10^13 – 10^9 molecules per cubic centimeter as compared to 2.7 × 10^19 molecules per cubic centimeter at ambient pressureso, ambient air has more than a milllion 10^6 =1,000,000 (to up to 10^10=10 billion) times more molecules per cubic centimeter
Quote from: Rodal on 07/25/2015 12:07 pmit can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower Vacuum. I look at this quite differently. If ANY verifiable, repeatable, non-experimental-artifact thrust significantly exceeding photon rocket level is demonstrated, it is mind-blowing. I seriously doubt that the experiments being performed today would have stumbled upon the optimal combination of design parameters that maximize performance. Getting the general principles accepted and understood is step one. THEN the engineers can go wild and see what the potential really is. Having goals for that performance (e.g. space applications) is, I think useful even if the lab results are not there yet.
The Wright brothers demonstrated that the combination of the tecnology of the internal combustion engine and the science of aerodynamics could result in a heavier-than-air machine with lift/weight>1. Many experts had declared that impossible. One could argue that the P-51 or the B-29 were straightforward engineering enhancements of those basic principles.
I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?
I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.
Quote from: mwvp on 07/25/2015 01:24 amQuote from: Rodal on 07/25/2015 12:47 am...1) aero is modeling the Copper as a Drude material. The Drude material constants he is using are equivalent to a material of unrealistically small resistivity. An idea would be to try different Drude material constants that effectively bring up the resistivity such that a reasonable Q=45,000 is obtainedThat sounds like cheating, a bad idea if it masks a flawed premise, like using an over-coupled dipole where a loosely coupled 1/4 wave probe or loop should be used. Or even an eigenmode excitation from Mpd. Just saying. I know, I need to stop criticizing and do it. I want to. My computer isn't amenable.I would think if the Drude model came from Meepers, the units, being normalized to u0 and e0, would be natural and not the problem. But I speak from ignorance I'm eager to relieve.Quote from: Rodal on 07/25/2015 12:47 am2) it is due to the fact that Meep is attempting to obtain Q from a time decay from the time response.That should be entirely valid. However, think of the whispering gallery, with start-up transients. It matters where, as well as when the measurement is made.Quote from: Rodal on 07/25/2015 12:47 amOtherwise Meep needs to perform volume and surface integrations of the fields, in order to calculate Q during this transient period.Perhaps Mpd (Meeps eigenmode harmonic solver) could do that real fast?<<I would think if the Drude model came from Meepers, the units, being normalized to u0 and e0, would be natural and not the problem. But I speak from ignorance I'm eager to relieve.>>No, take a look at the Drude model, its properties are very dependent on frequency. The Drude model constants available are for the optical range and wholly inapplicable to the 2.45 GHz range. The Drude model constants are not u0 and e0
Quote from: Rodal on 07/25/2015 12:47 am...1) aero is modeling the Copper as a Drude material. The Drude material constants he is using are equivalent to a material of unrealistically small resistivity. An idea would be to try different Drude material constants that effectively bring up the resistivity such that a reasonable Q=45,000 is obtainedThat sounds like cheating, a bad idea if it masks a flawed premise, like using an over-coupled dipole where a loosely coupled 1/4 wave probe or loop should be used. Or even an eigenmode excitation from Mpd. Just saying. I know, I need to stop criticizing and do it. I want to. My computer isn't amenable.I would think if the Drude model came from Meepers, the units, being normalized to u0 and e0, would be natural and not the problem. But I speak from ignorance I'm eager to relieve.Quote from: Rodal on 07/25/2015 12:47 am2) it is due to the fact that Meep is attempting to obtain Q from a time decay from the time response.That should be entirely valid. However, think of the whispering gallery, with start-up transients. It matters where, as well as when the measurement is made.Quote from: Rodal on 07/25/2015 12:47 amOtherwise Meep needs to perform volume and surface integrations of the fields, in order to calculate Q during this transient period.Perhaps Mpd (Meeps eigenmode harmonic solver) could do that real fast?
...1) aero is modeling the Copper as a Drude material. The Drude material constants he is using are equivalent to a material of unrealistically small resistivity. An idea would be to try different Drude material constants that effectively bring up the resistivity such that a reasonable Q=45,000 is obtained
2) it is due to the fact that Meep is attempting to obtain Q from a time decay from the time response.
Otherwise Meep needs to perform volume and surface integrations of the fields, in order to calculate Q during this transient period.