Quote from: birchoff on 07/25/2015 10:21 pmQuote from: Rodal on 07/25/2015 10:10 pmQuote from: flux_capacitor on 07/25/2015 10:08 pmFrom the intro in the abstract paper:How can Tajmar says:QuoteAfter developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventorand then measure:QuoteDue to a low Q factor of <50Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?Take a look at my prior posts (the ones were I suggested questions for Dr. Bagelbytes to ask). I think that there was gross overcoupling.Perhaps intentional to the magnetron's bandwidth.Not sure if it was overcoupling. But the magnetron only outputted 2.4ghz. They would have needed something that outputed 3Ghz to get a higher QAlso, the waveguide was almost as big as the fustrum! Based on what has been discussed in these threads I am shocked they get a result at all!
Quote from: Rodal on 07/25/2015 10:10 pmQuote from: flux_capacitor on 07/25/2015 10:08 pmFrom the intro in the abstract paper:How can Tajmar says:QuoteAfter developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventorand then measure:QuoteDue to a low Q factor of <50Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?Take a look at my prior posts (the ones were I suggested questions for Dr. Bagelbytes to ask). I think that there was gross overcoupling.Perhaps intentional to the magnetron's bandwidth.Not sure if it was overcoupling. But the magnetron only outputted 2.4ghz. They would have needed something that outputed 3Ghz to get a higher Q
Quote from: flux_capacitor on 07/25/2015 10:08 pmFrom the intro in the abstract paper:How can Tajmar says:QuoteAfter developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventorand then measure:QuoteDue to a low Q factor of <50Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?Take a look at my prior posts (the ones were I suggested questions for Dr. Bagelbytes to ask). I think that there was gross overcoupling.Perhaps intentional to the magnetron's bandwidth.
From the intro in the abstract paper:How can Tajmar says:QuoteAfter developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventorand then measure:QuoteDue to a low Q factor of <50Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?
After developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventor
Due to a low Q factor of <50
Quote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.What do you mean by the aparatus not being self contained?
With such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.
Quote from: WarpTech on 07/25/2015 10:40 pmThis graph clearly shows that the group velocity for small kr is faster than light.Seriously?
This graph clearly shows that the group velocity for small kr is faster than light.
Tajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Dielectric = NoneFrequency = 2.44GhzInput Power = 700w (output of magnetron)Pressure = 4×10-6Q = 20.3 (seems like this was measured and calculated after they finished all reported testing)Force (mN) = 0.02
Quote from: RonM on 07/25/2015 10:56 pmQuote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.I'll drink a couple of beers to it. Then again, I was planning on doing that tonight anyway. Still, the results are positive. There's more work to do to figure out what is or is not going on....Intriguing... by all means. But I need to see an explaination for why the vertical orientation still registering thrust on the torsion balance. I have been following these emdrive threads with the assumption that a torsion balance could only move horizontally left(positive) or right(negative). So if arranging the thruster in a vertical orientation still registers thrust in the positive direction and my assumption is correct. Either there is still another source of error in the measurement or preferrably or that behavior tells us more about how the emdrive is propelling itself.
Quote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.I'll drink a couple of beers to it. Then again, I was planning on doing that tonight anyway. Still, the results are positive. There's more work to do to figure out what is or is not going on....
Could an explanation for the EmDrive's internal workings be paralleled to something like cavitation bubbles in liquid? Such as: It's kind of a wild thought, but for some reason it made sense to me.
Quote from: birchoff on 07/25/2015 10:52 pmQuote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.What do you mean by the aparatus not being self contained?The power supply was not a part of the device for which a force was measured. Instead, it was connected to the device via Galinstan contacts. Thus the measured device was not self-contained, and leaves open the possibility of spurious forces caused by this external connection (thermal catenary sag for one, electromagnetic coupling for another, etc.).
Quote from: birchoff on 07/25/2015 11:13 pmQuote from: RonM on 07/25/2015 10:56 pmQuote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.I'll drink a couple of beers to it. Then again, I was planning on doing that tonight anyway. Still, the results are positive. There's more work to do to figure out what is or is not going on....Intriguing... by all means. But I need to see an explaination for why the vertical orientation still registering thrust on the torsion balance. I have been following these emdrive threads with the assumption that a torsion balance could only move horizontally left(positive) or right(negative). So if arranging the thruster in a vertical orientation still registers thrust in the positive direction and my assumption is correct. Either there is still another source of error in the measurement or preferrably or that behavior tells us more about how the emdrive is propelling itself.This gets into an earlier discussion about what might be happening inside the fustrum. Shell speculated that evanescent waves collapsed at the big end which prompted DrBagleBites to recall a simple cavitation experiment. In essence, there may be a weakness around the seams of the base an evanescent waves (or something) are leaking out the sides asymmetrically.This type of leakage could explain the chaotic behaviour exhibited by the baby EM Drive, for instance.Quote from: DrBagelBites on 07/07/2015 08:20 pmCould an explanation for the EmDrive's internal workings be paralleled to something like cavitation bubbles in liquid? Such as: ...It's kind of a wild thought, but for some reason it made sense to me.
Could an explanation for the EmDrive's internal workings be paralleled to something like cavitation bubbles in liquid? Such as: ...It's kind of a wild thought, but for some reason it made sense to me.
I'm sure someone has addressed this concern before but just in case it hasn't been brought up, has anyone considered the gyroscopic effect? My understanding is that a magnetron works by moving electrons in a circular path. I realize that the mass of the electrons and therefore the corresponding gyroscopic effect would be very small, but we are talking about exceedingly small forces here. The emdrive is being tested on a torsion pendulum and a gyroscope hanging from a pendulum will attempt to move in a precession motion. This might help explain why, according to some reports, the orientation of the engine affects the measured thrust. If it is the gyroscopic effect that is producing the apparent thrust, then it will of course be useless as any sort of engine.
Quote from: Prunesquallor on 07/25/2015 10:32 pmQuote from: birchoff on 07/25/2015 09:14 pmTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Ugh... This thruster is teeny. Like half a shot glass. Edit: corrected cutDr. Rodal - using your exact solution, what is the resonant frequency of this cavity?And does that huge waveguide hanging off the side make the device something other than a conical frustum? Looks like different geometry to me.aero
Quote from: birchoff on 07/25/2015 09:14 pmTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Ugh... This thruster is teeny. Like half a shot glass. Edit: corrected cut
Tajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385
The nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far
Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results.
Quote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.Tajmar concludes:QuoteThe nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far This is the most lukewarm kind of support imaginable.The authors state that they can not confirm or refute the claims of the EMDrive !!!!!(page 9 of Tajmar's report)If the authors themselves conclude that they cannot confirm or deny the EM Drive claims, there is nothing here for John Baez or Sean Carroll to have to respond to. All that Baez and Carroll have to do is to quote the authors saying that the authors accept that their report is inconclusive !
Quote from: aero on 07/25/2015 10:57 pmQuote from: Prunesquallor on 07/25/2015 10:32 pmQuote from: birchoff on 07/25/2015 09:14 pmTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Ugh... This thruster is teeny. Like half a shot glass. Edit: corrected cutDr. Rodal - using your exact solution, what is the resonant frequency of this cavity?And does that huge waveguide hanging off the side make the device something other than a conical frustum? Looks like different geometry to me.aeroAero, your intuition is correctEven the lowest modes, have a frequency higher than 2.45 GHz:This are the lowest natural frequencies I calculate for those dimensions:4.376 GHz "TE111 Cyl" Q=56,5994.717 GHz "TM010 Cyl" (*) Q=24,677The Q's are based on pure copper and perfect geometry, a copper alloy would have lower Q.the only way I can see this "EM Drive" having a natural frequency at 2.45 GHz would be because of the huge opening for the waveguide, which should lower the natural frequency.__________(*) the equivalent of TM010 in a cylinder (a degenerate mode since there is no such thing as TM010 in a truncated cone because p cannot be 0 because the fields in a truncated cone longitudinal direction cannot be constant , so this mode should be called something else)
Quote from: Rodal on 07/26/2015 01:01 amQuote from: aero on 07/25/2015 10:57 pmQuote from: Prunesquallor on 07/25/2015 10:32 pmQuote from: birchoff on 07/25/2015 09:14 pmTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Ugh... This thruster is teeny. Like half a shot glass. Edit: corrected cutDr. Rodal - using your exact solution, what is the resonant frequency of this cavity?And does that huge waveguide hanging off the side make the device something other than a conical frustum? Looks like different geometry to me.aeroAero, your intuition is correctEven the lowest modes, have a frequency higher than 2.45 GHz:This are the lowest natural frequencies I calculate for those dimensions:4.376 GHz "TE111 Cyl" Q=56,5994.717 GHz "TM010 Cyl" (*) Q=24,677The Q's are based on pure copper and perfect geometry, a copper alloy would have lower Q.the only way I can see this "EM Drive" having a natural frequency at 2.45 GHz would be because of the huge opening for the waveguide, which should lower the natural frequency.__________(*) the equivalent of TM010 in a cylinder (a degenerate mode since there is no such thing as TM010 in a truncated cone because p cannot be 0 because the fields in a truncated cone longitudinal direction cannot be constant , so this mode should be called something else)Meeper alert - other than frustum size, there is one other variance in design...slit antenna from waveguide launcher.This is quite different from other tests. wasn't going to link to idiots playing with magnetrons, but below you will see the effects of a polarized output, what happens when you insert a grid or slit.Effective radiation is reduced significantly. Does an omni pattern provide more radiation? I think yes. Did it affect tajmars experment? Possibly....
We would like to thank Roger Shawyer for his assistance
Quote from: deltaMass on 07/25/2015 10:37 pmWith such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.Tajmar concludes:Quote from: Tajmar and FiedlerThe nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far This is the most lukewarm kind of support imaginable. Shawyer is encouraged by this ? ( http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission )Quote from: Wired article The 'impossible' EmDrive could reach Pluto in 18 months Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results. The authors state that they can not confirm or refute the claims of the EMDrive !!!!!(page 9 of Tajmar's report)If the authors themselves conclude that they cannot confirm or deny the EM Drive claims, there is nothing here for John Baez or Sean Carroll to have to respond to. All that Baez and Carroll have to do is to quote the authors saying that the authors accept that their report is inconclusive !
...The difference between upwards and downwards measurements was 229 μN and therefore close to our expectation of 2x98 μN. The horizontal direction was supposed to be our zero thrust reference, and indeed it was about only 1/3 of the downwards measure...observations are as follows: The balance configuration seems to indeed measure thrust in the correct direction and magnitude as claimed byShawyer. The horizontal direction was supposed to measure only thermal effects and no thrust. We observed a turn-oneffect (of the same magnitude compared to other thrust directions but with an opposite value) and then anincrease to about 100 μN until the power was turned off. We then saw a behavior that was indeed expected froma thermal side-effect: The thrust still further increased a bit (delay from thermal shielding) and then went downto zero. The thruster up/down direction showed a very different behavior. They increased to 620 μN and 391 μNrespectively and then remained constant for a much larger time compared to the horizontal direction. A differentorientation of the magnetron (horizontal versus vertical) may have caused different thermal signatures andtherefore buoyancy effects. Still, this behavior was really different and repeatable. In the much lower powermeasurements from Brady et al on the torsion balance, we can also see that it took some time after power turnoff that the balance reading went back to zero as if the EMDrive got somehow charged and produced thrust which rather decays contrary to a simple switch off after power is removed.Our weakest part in this setup was certainly the simple connection of the magnetron with three flexible siliconisolated wires to the power supply. A current of several Ampere is flowing over those wires which can generatesignificant magnetic forces (although we tried to keep the wires close together such that the magnetic effects cancel) that may have influenced our measurements. This together with the buoyancy effect made this measurement setup less convincing compared to a torsion balance setup.