Quote from: DrBagelBites on 07/27/2015 03:57 pm@rfmwguyChatted up some of the companies at the conference, asked the ones in R&D about any sort of electromagnetic engines/propulsions they may be working on. No dice. Most or all are researching hall thrusters/ion propulsion/etc. ...That isn't surprising.
@rfmwguyChatted up some of the companies at the conference, asked the ones in R&D about any sort of electromagnetic engines/propulsions they may be working on. No dice. Most or all are researching hall thrusters/ion propulsion/etc. ...
Quote from: demofsky on 07/27/2015 06:30 amThe device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al. It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...Yes I agree it is very the Experimental EMDrive except Shawyer got 16mNs out of his. It took him several years to get it right. Q was 5,900 but that was because it had a dielectric inside. He used 5 magnetrons, burnt out 3 and burned a hole in a waveguide. But he got there. His experimental data was verified by a expert Uk aerospace industry group set up by the UK gov Dept of Defense. After the experts gave him the thumbs up, the UK gov gave him the 1st grant to build the Demonstrator EMDrive and the rotary test rig.After the UK gov again verified the data from the Demonstrator trials he got the final payment from the UK gov.
The device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al. It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...
Actually, I forgot that Tajmar had a screw-driven reduction in length. The length given must be the external length, the maximum length possible....There is an uncertainty from these two factors:1) We don't quite know the internal length with the screw-modified length...
A much larger resonance peak appeared above 3 GHz, but as we did not have a variable frequency microwave source we had to stick to Q ≈ 50. As our magnetron had an output power of 700 W, we expected a thrust of 98.2 μN according to Shawyer’s models. This was much higher than the resolution of our measurement equipment (< 0.1 μN) and we therefore decided to go ahead with testing and explore this low Q factor regime. After all adjustments, epoxy adhesive was used to fix the EMDrive’s top part on the cavity. Afterwards, some vibration testing was done and the Q factor measurement repeated to be sure that it does not change after extensive testing.
thks for update dr bb...if they answered quickly and didn't ask u what it was it may indicate they know abt it. that might be a good first question. ..have u heard abt. also agree we must avoid third-party advocacy posts...unscientific and not useful
Sir,Could you ask the question of Tajmar whether a slotted resonant iris was used between the WR 340 and WR 340 430 Transition Waveguide flanges for impedance matching purposes in his test setup.
Quote from: Rodal on 07/26/2015 11:58 pmActually, I forgot that Tajmar had a screw-driven reduction in length. The length given must be the external length, the maximum length possible....There is an uncertainty from these two factors:1) We don't quite know the internal length with the screw-modified length...I think the length/height is exactly what Tajmar claims it is -- 68.6 mm:Quote from: M. TajmarA much larger resonance peak appeared above 3 GHz, but as we did not have a variable frequency microwave source we had to stick to Q ≈ 50. As our magnetron had an output power of 700 W, we expected a thrust of 98.2 μN according to Shawyer’s models. This was much higher than the resolution of our measurement equipment (< 0.1 μN) and we therefore decided to go ahead with testing and explore this low Q factor regime. After all adjustments, epoxy adhesive was used to fix the EMDrive’s top part on the cavity. Afterwards, some vibration testing was done and the Q factor measurement repeated to be sure that it does not change after extensive testing.Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.
We iterated our design several times by consulting with R. Shawyer to be as representative as possible. Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor.
Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.
Quote from: cej on 07/27/2015 05:39 pmQuote from: Rodal on 07/26/2015 11:58 pmActually, I forgot that Tajmar had a screw-driven reduction in length. The length given must be the external length, the maximum length possible....There is an uncertainty from these two factors:1) We don't quite know the internal length with the screw-modified length...I think the length/height is exactly what Tajmar claims it is -- 68.6 mm:Quote from: M. TajmarA much larger resonance peak appeared above 3 GHz, but as we did not have a variable frequency microwave source we had to stick to Q ≈ 50. As our magnetron had an output power of 700 W, we expected a thrust of 98.2 μN according to Shawyer’s models. This was much higher than the resolution of our measurement equipment (< 0.1 μN) and we therefore decided to go ahead with testing and explore this low Q factor regime. After all adjustments, epoxy adhesive was used to fix the EMDrive’s top part on the cavity. Afterwards, some vibration testing was done and the Q factor measurement repeated to be sure that it does not change after extensive testing.Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.I think that X-Ray, TheTraveller, Todd "WarpTech" got this right. The dimensions are off by a factor of 2. Tajmar et.al. explicitly state that the top part was adjustable for length (page 3 of their report):QuoteWe iterated our design several times by consulting with R. Shawyer to be as representative as possible. Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor.bold added for emphasisBesides the fact that they explicitly write that the length was adjustable, one can see the length-adjusting frame on Figures 2b and 2c or their report.Figure 2a (COMSOL FEA plot) shows that the adjusted length was smaller than the big diameter.Finally, calculation shows that to resonate at 2.45 GHz, the dimensions had to be off by a factor of 2 and that the adjusted internal length was significantly smaller than the exterior full length.In your statement:Quote Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements. You are confusing "dynamic adjustment" with plain adjustment. I never claimed that there was dynamic adjustment. Rather, that they adjusted the internal length to get the cavity in resonance for TE111, prior to force measurements. This does NOT require any dynamic adjustment, this can be done at the outset, as they did.
Quote from: SeeShells on 07/27/2015 09:07 amLower the power of the magnetron and stabilize the output so less is lost in spurious non-Q effects and one last thought I've had is modifying a fanless CPU cooler to keep the magnetron cooler.http://www.acousticpc.com/images/a_nofan_cr-95c_copper_fanless_cpu_cooler.jpgI'm still thinking about this one.ShellYes. Every DIYer planning to use a magnetron should look at the already discussed paper "The Magnetron - A Low noise, Long Life Amplifier" (also attached to this message). To summarize here (I try to advertise the content of the paper for those who would still not have read it) the tricks to transform a noisy magnetron into a cleaner RF amp is to add a feedback mechanism limiting the temperature and thus emission of the cathode in a more subtle way and control over the anode current. To do this you need to:- Add a switch to disconnect the included lower-end DC power supply off the magnetron, whose sole purpose was to continuously heat the cathode filament, after the tube has started. So after heating has started, let the cathode be heated by back bombardment power alone.- Use an external, well filtered DC power supply to run the magnetron as a reflection amplifier also more specifically known as a directional amplifier, where the drive power injected through a ferrite circulator becomes indistinguishable from the power reflected by a mismatched load.- In such a configuration, there is a phase difference between input and output which also limits the gain, because the free running frequency of the driver is not tuned. Forcing the magnetron to operate at the same frequency as the driver can be done by using the natural magnetron's frequency dependence upon the anode current which is called magnetron pushing, or conversely the reactive component of load (magnetron pulling). The former is used more often.- Add a little solenoid called a buck-boost coil in the magnetic circuit, to control the anode current which changes the free running frequency of the magnetron, into a phase locked amp. The coil creates a magnetic field which increases or reduces the operating voltage, hence the anode current intercept of the load line with a fixed voltage power supply. The coil is ran with low power (< 5 W) from an op-amp that amplifies the phase error signal.- How to acquire noise data and add a feedback control loop is detailed in the paper so I won't rewrite it there. All you need to know is with that basic tuning the author decreased the noise in a frequency band of 300 kHz at 10 MHz from the carrier by more than 100 dB below the carrier level over a broad range of operating voltage, magnetic field, load and gain. With only 0.6 W drive, the gain was 30 dB at 560 W output. Noise at 10 kHz from the carrier can also be decreased in an even finer way.This way you obtain a high-gain, phase-locked, long-life, low noise microwave amplifier from a very cheap commercial oven magnetron.
Lower the power of the magnetron and stabilize the output so less is lost in spurious non-Q effects and one last thought I've had is modifying a fanless CPU cooler to keep the magnetron cooler.http://www.acousticpc.com/images/a_nofan_cr-95c_copper_fanless_cpu_cooler.jpgI'm still thinking about this one.Shell
Quote from: cee on 07/27/2015 05:50 pmSir,Could you ask the question of Tajmar whether a slotted resonant iris was used between the WR 340 and WR 340 430 Transition Waveguide flanges for impedance matching purposes in his test setup.If I have the time. Can't make any guarantees. -IEdit: I think you were talking to me. Let me know if you weren't.
Yes I was asking you dr bb, still new to this format. Appreciate your time.
I show the calculated TE111 Electric Field in theta polar direction for Tajmar's TU Dresden University EM Drive, to compare it with his COMSOL FEA calculationAssumed dimensions:Big diameter = 0.1062 m = (2*0.0541m - 0.002 m)Small diameter = 0.075 m = (2*0.0385 m - 0.002 m)Axial Length = 0.100842 m = 0.735*2*0.0686 mAs per TheTraveller I have subtracted 2 mm for copper thickness from the external dimensions, however this has a negligible influence on the resultsThe axial internal length is 73.5% of the exterior length (it is adjusted internally with a screw prior to testing)TE111 Natural frequency = 2.446 GHzI enclose strictly for discussion, research and illustration purposes Fig. 2 a of Tajmar et.al. COMSOL FEA analysis for comparison with my calculations “…for purposes such as criticism, comment, news reporting, scholarship, or research…” under US Fair Usehttp://fairuse.stanford.edu/overview/fair-use/what-is-fair-use/This is the American Institute of Aeronautics and Astronautics link to Martin Tajmar's et.al. paper, that should be obtained from the American Institute of Aeronautics and Astronautics:Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects M. Tajmar and G. Fiedler51st AIAA/SAE/ASEE Joint Propulsion Conference http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083
...Dr. Rodal,I just wanted to confirm the comsol jpeg rectangular to frustum transition. Yang and others have cut a rectangular slot in the frustrum sidewall and attached the rectangular waveguide. The comsol drawing shows the rectangular waveguide with a conical radial sector cutout, strange configuration, am I viewing that correctly ? A top view of the test setup would confirm that.
We iterated our design several times by consulting with R. Shawyer to be as representative as possible.
Quote from: TheTraveller on 07/27/2015 06:58 amQuote from: demofsky on 07/27/2015 06:30 amThe device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al. It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...Yes I agree it is very the Experimental EMDrive except Shawyer got 16mNs out of his. It took him several years to get it right. Q was 5,900 but that was because it had a dielectric inside. He used 5 magnetrons, burnt out 3 and burned a hole in a waveguide. But he got there. His experimental data was verified by a expert Uk aerospace industry group set up by the UK gov Dept of Defense. After the experts gave him the thumbs up, the UK gov gave him the 1st grant to build the Demonstrator EMDrive and the rotary test rig.After the UK gov again verified the data from the Demonstrator trials he got the final payment from the UK gov.Sigh. I'll try one more time. You keep making these statements over and over. However, you have provided no evidence to support those statements. Who were the experts who "verified" it? Where is a document which shows what was verified? Etc, etc. You promised us a paper which would end all doubts and all that was produced was an old paper which didn't have any new experimental data. I *really* want to be a believer and you make it extremely difficult. I'll say once again, stop posting blindly optimistic projections and focus on your build and get some data which can be independently verified and which shows what you claim...Please! I'm wishing you luck.Frankly, if this had been truly verified at the levels you imply, funding wouldn't be an issue and folks wouldn't be scrambling to do FundMe's for DIY versions. I sit within 50 miles of a LOT of people who would happily throw millions at the project if there was evidence such as you keep insisting already exists.