Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1804470 times)

Offline deltaMass

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It's a shame that Tajmar, being Director of an institute with access to fine equipment and trained staff, did such a shoddy job.
 
1. Not self-contained
2. Not correctly impedance matched
3. Thermal effects not analysed
4. Bloody great hole in the side of the frustum.

He's a good theoretician, but struggles as an experimenter. We all have our strengths and weaknesses.

I would beg you to be more precise about (3). Tajmar did account for thermal effects and did alot to remove them from their measurements. In the Ambient air balance beam measurements they wrapped the entire thing in glass wool placed it in a sealed aluminium box which was stuffed with more glass wool to prevent thermal air currents.

In the torsion balance test the whole chamber was evacuated. And since there was an adjustable hole on the narrow end I doubt it was air tight which means the entire frustum would also have been evacuated.
Fair enough, but the fact that "thrust" persisted for a long time after RF power was switched off means that perhaps the entire magnitude of the "thrust" could be accounted for by heat. That's clearly not how you want measurements to work.

Online Rodal

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EM DRIVE FORCE vs. TIME

Antenna perpendicular to longitudinal direction placed near the Small Base for Yang/Shell frustum (the frustum of a cone that Yang may have used for some of her experiments and that Shell is thinking about using in her experiments)

Compare with http://forum.nasaspaceflight.com/index.php?topic=37642.msg1406309#msg1406309

1) It is better to have the antenna perpendicular to the longitudinal direction, and placed near the Big Base, which results in almost twice the net force as when the antenna is place near the Small Base.

2) We also verified that the worst thing to do is to place the antenna aligned along the longitudinal direction

3) We also verified that one cannot excite Transverse Electric (TE) modes with a dipole antenna, regardless of orientation or placement in the truncated cone, the mode excited by a dipole antenna is a Transverse Magnetic (TM) mode.

4) The smaller force at the Big Base is leading the greater force at the Small Base even though the antenna is placed near the Small Base in this case.  When the antenna was placed near the Big Base, there was practically no phase difference between the force vs. time for both bases.

5) We need to calculate rfmwguy/NSF-1701 geometry with the antenna placed at different places to see whether these conclusions also apply to that geometry. 


__________________________

Quote from: aero


Yang-Shell - 229x196x196

This is the final summary output from the log file.

run 0 finished at t = 13.054 (6527 timesteps)

Total number of slices 14, the last 14 of 32 full cycles, or periods at 0.1 period intervals. That is, at 30.7, 30.8 and so forth to 32.0 periods of the drive center frequency.
Number of time steps, 6527 and total meep time = 13.054 time units.
« Last Edit: 07/28/2015 06:50 PM by Rodal »

Offline deltaMass

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A word about batteries - specifically Li-ion. We have per Wikipedia
250 - 350 W/Kg for specific power, and
100 - 265 W.h/Kg for specific energy.

So if you need 100 W, it will weigh ~0.3 Kg, and that will give you ~80 W.h, or ~40 minutes of continuous power.
If you need 1000 W, it will weigh ~3 Kg, and that will give you ~800 W.h, or ~40 minutes of continuous power once again.

« Last Edit: 07/28/2015 02:41 PM by deltaMass »

Offline martinc

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Quote
Fair enough, but the fact that "thrust" persisted for a long time after RF power was switched off means that perhaps the entire magnitude of the "thrust" could be accounted for by heat. That's clearly not how you want measurements to work.
doesn't that just mean that the driver of the thrust persists for a time, whatever it's source? also how does the thrust decay? is it linear or show some interesting drop off.
« Last Edit: 07/28/2015 02:46 PM by martinc »

Offline birchoff

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It's a shame that Tajmar, being Director of an institute with access to fine equipment and trained staff, did such a shoddy job.
 
1. Not self-contained
2. Not correctly impedance matched
3. Thermal effects not analysed
4. Bloody great hole in the side of the frustum.

He's a good theoretician, but struggles as an experimenter. We all have our strengths and weaknesses.

I would beg you to be more precise about (3). Tajmar did account for thermal effects and did alot to remove them from their measurements. In the Ambient air balance beam measurements they wrapped the entire thing in glass wool placed it in a sealed aluminium box which was stuffed with more glass wool to prevent thermal air currents.

In the torsion balance test the whole chamber was evacuated. And since there was an adjustable hole on the narrow end I doubt it was air tight which means the entire frustum would also have been evacuated.
Fair enough, but the fact that "thrust" persisted for a long time after RF power was switched off means that perhaps the entire magnitude of the "thrust" could be accounted for by heat. That's clearly not how you want measurements to work.

Again I dont think that can be claimed. I included the last figure from the report which he graphs the thrust response of all directions. In graph (a) you can clearly see that the temperature increase is delayed, while the thrust increase is damn near instantaneous, for both the positive/control(up) directions. the negative lags a bit but definitely starts before the temperature begins rising. Also the positive/control(up) begin falling as temp climbs and holds till power is turned off at which time it craters into the negative. Asside from the control (up) orientation showing thrust the only other wierd outlier is the negative direction. But it doesn't appear to be too strongly correlated with temp.

All in all I would hesitate to say you could explain ALL the thrust with temperature given this data trace.



I 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 Use

http://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. Fiedler
51st AIAA/SAE/ASEE Joint Propulsion Conference

http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

Offline DrBagelBites

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Hello all!

I will be live-blogging Tajmar's presentation at https://www.reddit.com/live/vbfu09jnz6ab/


Offline birchoff

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All things considered about Tajmar's test I think the most interesting question I would have is if Tajmar intends to continue testing the EmDrive and what changes do they envision making to their test procedure.

Offline DrBagelBites

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All things considered about Tajmar's test I think the most interesting question I would have is if Tajmar intends to continue testing the EmDrive and what changes do they envision making to their test procedure.

I feel the same. I think asking a technical question will sort of be lost due to him not preparing a response for it as well as the time limitation on his response.

I think the "what's next?" answer would be very valuable.

Offline BL

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“I'm a fan of a web of beamers. These are high power solar-powered lasers and the beams crisscross the solar system. They are of course dynamically steerable. It is like laying down an infrastructure of tramlines. They enable both acceleration and braking. They would greatly help in opening up interplanetary space.”

The inverse square law is NOT your friend.

Offline deltaMass

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Please ask him if he will be doing any further testing first of all. He might just want to walk away from this tar-baby.
If he does want to continue, I'd like to know if he plans to go fully self-contained using battery power.

Offline deltaMass

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“I'm a fan of a web of beamers. These are high power solar-powered lasers and the beams crisscross the solar system. They are of course dynamically steerable. It is like laying down an infrastructure of tramlines. They enable both acceleration and braking. They would greatly help in opening up interplanetary space.”

The inverse square law is NOT your friend.
That is correct. It is also correct that a parallel beam does not obey that law.

Offline Star One

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Please ask him if he will be doing any further testing first of all. He might just want to walk away from this tar-baby.
If he does want to continue, I'd like to know if he plans to go fully self-contained using battery power.

There is no reason he should walk away from it, not everyone carries a pre-conceived bias on the matter?


Well his paper is already hitting the click-bait sites.

http://www.ign.com/articles/2015/07/28/impossible-em-propulsion-engine-confirmed-by-scientists

Perhaps we should just close this thread for a week and start up where we left off after the trolls scamper home.... :)

Didn't someone mention this particular thread was due for closure anyway due to length?
« Last Edit: 07/28/2015 03:40 PM by Star One »

Offline zellerium

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...
Question for the magnetron DIYers. How will you get your Q to 50 so your frustum will accept all the magnetron energy. If it is higher than 50, the bandwidth may not be wide enough for your magnetron.

Give me a narrow band Rf signal that will allow the frustum to be tuned to a Q exceeding 100K and a VSWR feedback signal to track and adjust to cavity resonance changes.

My 100W amp is on the water. I'm so thankful that my mate found it.

Yang certainly had no issues getting the highest reported thrust to power with a magnetron. Of course you cannot accept all of the magnetron's energy with a high Q, they key seems to be maximizing Q around your frequency of maximum power, and matching a load to accept reflected power.

It's a shame that Tajmar, being Director of an institute with access to fine equipment and trained staff, did such a shoddy job.
1. Not self-contained
2. Not correctly impedance matched
3. Thermal effects not analysed
4. Bloody great hole in the side of the frustum.
He's a good theoretician, but struggles as an experimenter. We all have our strengths and weaknesses.
Sounds a bit harsh to me. Tajmar incorporated elements from Shawyer and EW, and impedance matched with a different goal in mind. Now we know that accepting all of the magnetron's energy is not the best option. Self containment sounds lovely, but is in many ways impractical, especially when liquid metal contacts are available.   

People are quick to throw stones at experimenters and then wonder where all of their data went...

Online Rodal

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Prof. Tajmar is at a University.  He does contract research funded by Airbus, aerospace companies and institutes.  Whether he continues this research or not is a function of whether he continues being funded for it, pure and simple. The report itself hints that (if funding continues) they will continue this research:

the final words in the report:

Quote
Next steps include better magnetic shielding, further vacuum tests and improved EMDrive models with higher Q factors and electronics that allow tuning for optimal operation. As a worst case we may find how to effectively shield thrust balances from magnetic fields. 

Since he finishes the report by stating what the next steps in this research are going to be, in my mind asking him whether he intends to continue the research is a wasted question IMHO
« Last Edit: 07/28/2015 03:46 PM by Rodal »

Offline Star One

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Prof. Tajmar is at a University.  He does contract research funded by Airbus, aerospace companies and institutes.  Whether he continues this research or not is a function of whether he continues being funded for it, pure and simple. The report itself hints that (if funding continues) they will continue this research.

Who is funding him for this research?

Online RonM

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Didn't someone mention this particular thread was due for closure anyway due to length?

A few days after Prof. Tajmar gives his presentation would be a good time to close thread 3 and start a new thread. A summary of Prof. Tajmar's results can be in the new thread's OP.

Offline BL

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Re Post #5473 by deltaMass

"That is correct. It is also correct that a parallel beam does not obey that law."

Agree 100%.  Has anyone ever seen an example of such a thing?  I. e., a free space beam of electromagnetic energy of any frequency whose power density was constant at all distances from the source?

Offline deltaMass

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Are we then in violent agreement that the more parallel the beam can be made, the longer its range?

I would refer you to the numerous papers on beaming. Many can be found on the Icarus Interstellar site. I recommend Benford and Landis especially, with a tip o' the hat to Bae.
« Last Edit: 07/28/2015 04:00 PM by deltaMass »

Offline Prunesquallor

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Re Post #5473 by deltaMass

"That is correct. It is also correct that a parallel beam does not obey that law."

Agree 100%.  Has anyone ever seen an example of such a thing?  I. e., a free space beam of electromagnetic energy of any frequency whose power density was constant at all distances from the source?

Laser pulses that are shot at the reflectors that the Apollo astronauts left on the moon start out at a diameter of 3.5 m.  Atmospheric effects cause divergence to about 2 km at the moon.

Edit: tei-po



« Last Edit: 07/28/2015 03:59 PM by Prunesquallor »
Retired, yet... not

Offline deltaMass

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The idea is to not fire a beam through atmosphere, since this is a space-based technology. See also DE-STARS

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