Hi
You mean like this?
qraal
Interesting, page 4:
We plan to build an EMDrive model similar to White et al. on our upgraded thrust balance as shown in Fig. 3. Our vacuum chamber is much larger allowing for better electromagnetic shielding. We plan to optimize the thermal design to limit any centre of gravity shifts due to thermal expansion. In addition, other geometries will be extensively tested as well.
Figure 3 attached. It is designed to work with a light and compact solid-state microwave source mounted on the cavity. A much better design IMHO than their previous cavity with the giant hole on its side to fit a WR340 waveguide and a microwave oven magnetron, that was operating below optimal resonance.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
I understand your point. But on the other hand if the power source is not part of the test article + torsion pendulum system, any force detected could originate from momentum exchanged with the power supply, which in this case is outside of the test bed. If I remember correctly, that was a major error source pointed out by Juan Yang in her latest published paper, when she reviewed her previous "high power" tests (where the magnetron was outside of the balance system).
So if we follow the two arguments, the amplifier would have to be mounted directly on the balance arms, but detached from the cavity. Then this heat producing part would not move on the apparatus when the cavity is turned 180° vertically of horizontally.
Hi
You mean like this?
qraal
Interesting, page 4:
We plan to build an EMDrive model similar to White et al. on our upgraded thrust balance as shown in Fig. 3. Our vacuum chamber is much larger allowing for better electromagnetic shielding. We plan to optimize the thermal design to limit any centre of gravity shifts due to thermal expansion. In addition, other geometries will be extensively tested as well.
Figure 3 attached. It is designed to work with a light and compact solid-state microwave source mounted on the cavity. A much better design IMHO than their previous cavity with the giant hole on its side to fit a WR340 waveguide and a microwave oven magnetron, that was operating below optimal resonance.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
Good concerns. Please note that with separated amplifier and frustum, you still can't ground the frustum to the beam because doing so also makes the important and easy test meaningless due to altered 3-D structure of ground loops.
Hi
You mean like this?
qraal
Interesting, page 4:
We plan to build an EMDrive model similar to White et al. on our upgraded thrust balance as shown in Fig. 3. Our vacuum chamber is much larger allowing for better electromagnetic shielding. We plan to optimize the thermal design to limit any centre of gravity shifts due to thermal expansion. In addition, other geometries will be extensively tested as well.
Figure 3 attached. It is designed to work with a light and compact solid-state microwave source mounted on the cavity. A much better design IMHO than their previous cavity with the giant hole on its side to fit a WR340 waveguide and a microwave oven magnetron, that was operating below optimal resonance.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
Hi Peter,
1x skin depth at 3.55GHz is 1.09 um. 5x = 5.45 um.
Which means a 5.45 um deep scratch will act like a cut all the way through the copper and disrupt normal eddy current flow.
If scratches and polish don't matter, please tell that to the guys that build accelerator cavities.
Hi
You mean like this?
qraal
Interesting, page 4:
We plan to build an EMDrive model similar to White et al. on our upgraded thrust balance as shown in Fig. 3. Our vacuum chamber is much larger allowing for better electromagnetic shielding. We plan to optimize the thermal design to limit any centre of gravity shifts due to thermal expansion. In addition, other geometries will be extensively tested as well.
Figure 3 attached. It is designed to work with a light and compact solid-state microwave source mounted on the cavity. A much better design IMHO than their previous cavity with the giant hole on its side to fit a WR340 waveguide and a microwave oven magnetron, that was operating below optimal resonance.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
Hi Peter,
1x skin depth at 3.55GHz is 1.09 um. 5x = 5.45 um.
Which means a 5.45 um deep scratch will act like a cut all the way through the copper and disrupt normal eddy current flow.
If scratches and polish don't matter, please tell that to the guys that build accelerator cavities.
TT, does your concern about
surface variation of only a few nanometers deep also apply to Monomorphic's build based on adjoining copper tape ?
Hi
You mean like this?
qraal
Interesting, page 4:
We plan to build an EMDrive model similar to White et al. on our upgraded thrust balance as shown in Fig. 3. Our vacuum chamber is much larger allowing for better electromagnetic shielding. We plan to optimize the thermal design to limit any centre of gravity shifts due to thermal expansion. In addition, other geometries will be extensively tested as well.
Figure 3 attached. It is designed to work with a light and compact solid-state microwave source mounted on the cavity. A much better design IMHO than their previous cavity with the giant hole on its side to fit a WR340 waveguide and a microwave oven magnetron, that was operating below optimal resonance.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
Hi Peter,
1x skin depth at 3.55GHz is 1.09 um. 5x = 5.45 um.
Which means a 5.45 um deep scratch will act like a cut all the way through the copper and disrupt normal eddy current flow.
If scratches and polish don't matter, please tell that to the guys that build accelerator cavities.
TT, does your concern about surface variation of only a few nanometers deep also apply to Monomorphic's build based on adjoining copper tape ?
Hi FC,
Micro meters, not nano meters.
Big time concern about the foil.
Do hope Jamie moves on to applying an electro polished copper finish to his cavity.
At 2.45 GHz, Roger has set +-10 um as the max cavity build error. That is not an academic value but a real world engineering tolerance to be achieved.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
I understand your point. But on the other hand if the power source is not part of the test article + torsion pendulum system, any force detected could originate from momentum exchanged with the power supply, which in this case is outside of the test bed. If I remember correctly, that was a major error source pointed out by Juan Yang in her latest published paper, when she reviewed her previous "high power" tests (where the magnetron was outside of the balance system).
So if we follow the two arguments, the amplifier would have to be mounted directly on the balance arms, but detached from the cavity. Then this heat producing part would not move on the apparatus when the cavity is turned 180° vertically of horizontally.
I completely agree with this if you have an amplifier on the setup (cavity + torsion balance). (I intend to not use an amplifier on the torsion balance at all, but to couple the microwave signal contactless in with a special coupling cavity, as described earlier by me [https://arxiv.org/abs/1706.04999]. And yes, then you have to show that this method does not impose forces or moments itself. Btw,
White et al., 2016 have not done this for the suppy of DC current with liquid metal contacts, if I remember well.)
1x skin depth at 3.55GHz is 1.09 um. 5x = 5.45 um.
Which means a 5.45 um deep scratch will act like a cut all the way through the copper and disrupt normal eddy current flow.
If scratches and polish don't matter, please tell that to the guys that build accelerator cavities.
You might have a point. But I still reach reasonable Q values with unpolished walls (up to 30k @ 2.5 - 3.5 GHz).
TT, does your concern about surface variation of only a few nanometers deep also apply to Monomorphic's build based on adjoining copper tape ?
Hi FC,
Micro meters, not nano meters.
Big time concern about the foil.
Do hope Jamie moves on to applying an electro polished copper finish to his cavity.
At 2.45 GHz, Roger has set +-10 um as the max cavity build error. That is not an academic value but a real world engineering tolerance to be achieved.
My bad, ok: micrometers.
But still, if you and Shawyer are right for this very tight resolution at those frequencies, then not only copper tape is a big concern; making the structure with a 3D printer would also prove to be difficult: Jamie's FDM 3D printer (Prusa Mk2) offers a Z-resolution of 0.05 mm, i.e.
50 µm. I don't see how one could hand-polish accurately such surface below that after printing.
1x skin depth at 3.55GHz is 1.09 um. 5x = 5.45 um.
Which means a 5.45 um deep scratch will act like a cut all the way through the copper and disrupt normal eddy current flow.
If scratches and polish don't matter, please tell that to the guys that build accelerator cavities.
You might have a point. But I still reach reasonable Q values with unpolished walls (up to 30k @ 2.5 - 3.5 GHz).
Hi Peter,
How are you measuring Q and is it unloaded or loaded Q?
30k seems very high for unpolished copper.
If you are using 2 ports, make the sample port measure power, via at least 20dB isolation and then vary freq to find max power and the high/low freq where power drops 50%.
Do that at say 10mW, 100mW, 1W, 10W, 100W, etc or every 10dBm to properly map the loaded Q vs power curve.
TT, does your concern about surface variation of only a few nanometers deep also apply to Monomorphic's build based on adjoining copper tape ?
Hi FC,
Micro meters, not nano meters.
Big time concern about the foil.
Do hope Jamie moves on to applying an electro polished copper finish to his cavity.
At 2.45 GHz, Roger has set +-10 um as the max cavity build error. That is not an academic value but a real world engineering tolerance to be achieved.
My bad, ok: micrometers.
But still, if you and Shawyer are right for this very tight resolution at those frequencies, then not only copper tape is a big concern; making the structure with a 3D printer would also prove to be difficult: Jamie's FDM 3D printer (Prusa Mk2) offers a Z-resolution of 0.05 mm, i.e. 50 µm. I don't see how one could hand-polish accurately such surface below that after printing.
Hi FC,
It is not a binary system. Of course the results improve, the more cavity build defects are reduced.
Electropolishing is a good and proven way to eliminate mechanical polishing scratches. However not all Electropolishing achieves the desired results. There seems to be a bit of Black Magic or trade secrets involved.
But still, if you and Shawyer are right for this very tight resolution at those frequencies, then not only copper tape is a big concern; making the structure with a 3D printer would also prove to be difficult: Jamie's FDM 3D printer (Prusa Mk2) offers a Z-resolution of 0.05 mm, i.e. 50 µm. I don't see how one could hand-polish accurately such surface below that after printing.
I'm not sure anyone (besides Shawyer) claims to have built a cavity with tolerances below 1.0mm, much less 0.01mm. It is the most difficult and expensive item to accomplish on the "General Principles of EmDrive design" list. But in my opinion, the best way to do it is to 3D print the parts in wax and use the lost wax process to create copper parts, which are then machined to the necessary tolerances and polished.
Based on VNA it seems as if the copper foil is working at these power levels. There is return loss precisely where simulations predicted, with the smith chart confirming it is a resonator. I would be worried about the copper separating at higher powers, but at 25W max I don't think that will be an issue.
I did design the cavity so I can switch between foil-covered end-plates and solid copper end-plates. I will run a VNA sweep on each configuration to see if there is a big difference in Q.
Temperature sensor inside the draft enclosure is working. I ended up going with a 4-20mA signal with pt100 resistance temperature sensor. Here is a screen cap of all 5 channels of data I will be collecting off the torsional pendulum. I can still add up to three more channels. Every once in a while I notice a fairly strong repetitive RF signal in this band. I'm not sure what it is except perhaps my neighbor's microwave oven. Does anyone recognize the signal in channel 4?
Hi
You mean like this?
qraal
Interesting, page 4:
We plan to build an EMDrive model similar to White et al. on our upgraded thrust balance as shown in Fig. 3. Our vacuum chamber is much larger allowing for better electromagnetic shielding. We plan to optimize the thermal design to limit any centre of gravity shifts due to thermal expansion. In addition, other geometries will be extensively tested as well.
Figure 3 attached. It is designed to work with a light and compact solid-state microwave source mounted on the cavity. A much better design IMHO than their previous cavity with the giant hole on its side to fit a WR340 waveguide and a microwave oven magnetron, that was operating below optimal resonance.
I think it is not a good idea to integrate heat producing parts (the amplifier) with the cavity. It means that rotating the frustum by 180 degrees (and vertical), an important and easy test, will be rather meaningless.
Hi Peter,
1x skin depth at 3.55GHz is 1.09 um. 5x = 5.45 um.
Which means a 5.45 um deep scratch will act like a cut all the way through the copper and disrupt normal eddy current flow.
If scratches and polish don't matter, please tell that to the guys that build accelerator cavities.
Can you imagine how small the difference is regarding the
volume to surface ratio due to a few µm deep scratch for such a cavity resonator, at 2...4 GHz? Sure the wall currents are slightly bent at the scratch but in contrast to the local wavelength this is so damn tiny that it almost don't matter because the conductivity in the region dont change.
What impacts the Q factor is the conductivity of the walls and maybe inhomogeneities of the order of lets say 1/10 of the wavelength or something like that. Monomorphic has shown some calculations to this subject a few threads ago. Dr. Rodal showed an analytic calculation of the Q factor as well as others.
I would be happy if you show us a Q comparison (i.e. calculations or even measurements!) of a cavity with the high surface quality you state, with the same one after a few scratches were made.http://forum.nasaspaceflight.com/index.php?topic=39214.msg1474347#msg1474347http://www.gregegan.net/SCIENCE/Cavity/Cavity.htmlhttp://forum.nasaspaceflight.com/index.php?topic=39772.msg1503747#msg1503747http://forum.nasaspaceflight.com/index.php?topic=39772.msg1503825#msg1503825http://forum.nasaspaceflight.com/index.php?topic=39772.msg1504635#msg1504635I bet even with the best VNA you can get (within its uncertainty range) you will see no difference even using high average values. If you think you can reject this please deliver real results!
Hence the comments about such stringent geometry and polishing requirements being an example of 'raising the goalpost' for experimentalists.
Followed by "If you don't have it, you won't see it. Told you so".
Not very auspicious.
I really hope the ongoing experiments prove otherwise.
Hence the comments about such stringent geometry and polishing requirements being an example of 'raising the goalpost' for experimentalists.
Followed by "If you don't have it, you won't see it. Told you so".
Not very auspicious.
I really hope the ongoing experiments prove otherwise.
As I suggested before, please share with the real world accelerator cavity and waveguide makers they can stop polishing their interior surfaces and using electro polishing to eliminate scratches, plus they can throw away all their very tight manufacturing tolerances.
Maybe look into a space rated waveguide and explore the manufacturing tolerances, then talk to people that make accelerator cavities?
See attached image showing the inside of an accelerator cavity. Maybe tell him his cavity will still work well without the precision machining and scratch free optical quality polishing.
Also attached a paper on using electropolishing for accelerator cavities. If polise was not important, why go to all the bother?
Answer: Tight build tolerance and optical scratch free surface are critical to achieving the best Q possible. Will lower standards still work? Probably but I suspect with a steep drop off in results.
Monomorphic
There's loads of things in the 2.4Ghz band, here's a list of common uses https://en.wikipedia.org/wiki/List_of_2.4_GHz_radio_use
Anything on the list look familiar?
Solved. I checked my spectrum analyser and didn't see anything in the frequency band so I knew it was something else. It was the cheap variable voltage transformer I was using to power the calibration coil. I guess I taxed it too much and it was going wonky. I switched to a higher quality 8.5A 12V power source and it's gone now.
Hence the comments about such stringent geometry and polishing requirements being an example of 'raising the goalpost' for experimentalists.
Followed by "If you don't have it, you won't see it. Told you so".
Not very auspicious.
I really hope the ongoing experiments prove otherwise.
As I suggested before, please share with the real world accelerator cavity and waveguide makers they can stop polishing their interior surfaces and using electro polishing to eliminate scratches, plus they can throw away all their very tight manufacturing tolerances.
Maybe look into a space rated waveguide and explore the manufacturing tolerances, then talk to people that make accelerator cavities?
I agree I'm no expert.
Personally, I'm more interested in the experiments trying to conclusively prove that 1) these things actually exist and 2) work in a vacuum as thrusters with greater efficiency than a perfectly collimated photon rocket.
Due to lack of proof on the matter, super-strong Emdrives that can levitate cars for me simply don't exist. If some clear evidence emerges tomorrow, I'd change my mind, but there is none so far.
With those interests in mind, I think a passably good cavity that could be made by a DIY builder or an engineer with regular materials and machinery, and without impossible space-industry quality requirements, could be used to prove those points.
Roger Shawyer himself started there, as far as I know. His first Emdrives weren't that much different from what several DIY engineers are doing now. And none of his designs have been tested in a vacuum chamber, also as far as I know. Thus NASA EW's and now Prof. Tajmar's experiments will have a clear advantage towards those 2 goals I mentioned.