Perhaps a more general solution to the problem of melting nylon bolts would be to search diligently for a material that does not melt. While perhaps more difficult to obtain (read that as "custom manufacture") bolts can be made from almost any solid. I can just imagine Paul with his pen-knife carving a bolt from a wooden dowel rod. Or baking a ceramic bolt in this wife's kitchen oven.Seriously though, the bolts problem is a materials issue. What are the necessary characteristics of the bolts, then what are the various materials that satisfy those specifications? Now that we know the specifications, who wants to volunteer to make 4 bolts?Edit Add: Or maybe there exists an epoxy (glue) that would serve to attach the dielectric disks?
the nylon bolts themselves could be contributing to the measured force we are seeing? It has a much smaller volume than the PE and PTFE discs, but they have a much higher dissipation factor than PE or PTFE that could translate into more work done converting E&M momentum into mechanical forces.
All:I tried epoxy and superglue bonding the PE and PTFE discs to the frustum end-caps, but these two plastics just happen to be the slickest and hardest plastics to bond to anything else. Drat! And yes I tried to find aluminum oxide or other low-loss dielectric ceramics bolts & nuts in long enough lengths (~2.50") to work in my application with no luck, but I'll admit I didn't look very hard at the time for I had many other things to do.Aero: I'm not going to start carving out bolts from wood dowels! But that does make me wonder if any wood would have a low enough dissipation factor at 2.0 GHz to be useable... So many things to think about... Best, Paul M.
Surface roughening of the copper and of the HD PE results in mechanical interlocking sites and causes bondstrength to increase dramatically. A surface roughness of approximately 60-125 microinches is often used as a guideline for assemblies that are to be bonded with adhesives. Shotblasting of the copper surface is usually needed. This is an insurmountable problem for your extremely thin copper surface: there is practically no thickness of copper on the fiber-reinforced flat end to be able to roughen the copper.
Paul, I have experience with bonding hard to bond polymers, it can be done successfully, but it is not trivial, as you have also experienced. This combined with the permanent nature of an adhesive, would also lead me to seek bolt alternatives, particularly for an R&D effort were you are going to have to dismantle, disassemble and reconfigure your setup from time to time.
Do the screws to fix the dielectric inside the frustum go through the end PCB plate ? In this case, even if the hole in the copper is much smaller than the wavelength (in nylon ?), wouldn't that allow a significant amount of em energy to escape and bounce around between the frustum and vacuum chamber walls ? Aero's simulation with Meep seemed to say that evanescent waves could funnel through much thinner cracks, if not to let escape real travelling photons at least for near field interactions with things outside the frustum...
Quote from: Rodal on 02/22/2015 02:03 am... then many scientists tried to replicate their experiment but hopes fell with the large number of negative replications, and the withdrawal of many positive replications.Sad but true. There is, however, somewhat of a renaissance occurring right now with LENR+ (commercially viable LENR). The current most promising method uses a mixture of nickel powder, iron powder, and LiAlH4 heated to 1100 C under pressure. Multiple universities in the U.S. have recently opened programs with full funding to investigate LENR+. Don't count this phenomena out entirely. Coupled with an EM Drive, the space flight applications become very interesting. Admittedly, controversy abounds, and it is still early to say what the probability of success and implications might be, but nonetheless, it doesn't hurt to keep a finger on the pulse on the most current efforts underway.
... then many scientists tried to replicate their experiment but hopes fell with the large number of negative replications, and the withdrawal of many positive replications.
If you would like I can sputter coat the mating surface to the end plate w/ copper (or something that would make it easier to adhesive bond). Only cost you the postage.....
Quote from: Star-Drive on 02/22/2015 03:26 pmAll:I tried epoxy and superglue bonding the PE and PTFE discs to the frustum end-caps, but these two plastics just happen to be the slickest and hardest plastics to bond to anything else. Drat! And yes I tried to find aluminum oxide or other low-loss dielectric ceramics bolts & nuts in long enough lengths (~2.50") to work in my application with no luck, but I'll admit I didn't look very hard at the time for I had many other things to do.Aero: I'm not going to start carving out bolts from wood dowels! But that does make me wonder if any wood would have a low enough dissipation factor at 2.0 GHz to be useable... So many things to think about... Best, Paul M.The marine adhesive made by 3M (5200 or 5220 fast cure) will stick to anything; even under water. I have used it on HDP. Most adhesives will just drop off once they have cured. One trick I learned for gauging the dissipation factor of a plastic is to put it in a microwave oven at high power for 10 minutes; or less. But I think the problem you are seeing is not from the dissipation factor of the plastic because your power level is relatively low. Try putting one of the nylon bolts in a microwave and see if it melts. What may be happening is the thin Copper coating is getting very hot and melting the nylon bolt. The radiation pattern from the loop antenna inside the cavity directs most of the rf power to the large end, irrespective of the mode.
A recent publication [Phys. Rev. Lett. 92, 020404 (2004)PRLTAO0031-900710. 1103/PhysRevLett.92.020404] raises the possibility of momentum transfer from zero-point quantum fluctuations to matter, controlled by applied electric and magnetic fields. We present a Lorentz-invariant description using field-theoretical regularization techniques. We find no momentum transfer for homogeneous media, but predict a very small transfer for a Casimir-type geometry.
About half the time when I think this through, the darn thing thrusts backwards.
.....it was producing less than half of what it did before and in the wrong direction!......Apparently not having the PE discs firmly mounted to the frustum's small OD end cap hindered the thrust producing mechanism that conveys the generated forces in the PE to the copper frustum.
Quote from: Notsosureofit on 02/21/2015 08:49 pm@ Star-DriveWe've battled the Nylon vs Teflon fasteners for years in our plasma chambers. These days we replace the Nylon ones every run. Teflon holds up very well, just won't take much mechanical load.Notsosureofit:We've fried a number of nylon bolts and have found that the best way to keep them from getting cooked is to keep them out of the high E-field regions in the cavity. For Instance we tested the copper frustum in its TM010 mode and mounted a 5.0 inch OD by 1.0" thick PTFE disk at the center of the large OD end cap of the copper frustum with one 1/4-20 nylon bolt. We got some large thrust signatures in that configuration, see attached slide, but the dam nylon bolt kept melting and dropping the PTFE discs into the main body of the cavity. Brother did that look like a magnitude 9 earthquake on our uN resolution force measurement system! That said, I'm wondering if the nylon bolts themselves could be contributing to the measured force we are seeing? It has a much smaller volume than the PE and PTFE discs, but they have a much higher dissipation factor than PE or PTFE that could translate into more work done converting E&M momentum into mechanical forces.Best, Paul M.
@ Star-DriveWe've battled the Nylon vs Teflon fasteners for years in our plasma chambers. These days we replace the Nylon ones every run. Teflon holds up very well, just won't take much mechanical load.
http://www.tara.tcd.ie/handle/2262/38886http://www.ncbi.nlm.nih.gov/pubmed/16711970http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.96.130402QuoteA recent publication [Phys. Rev. Lett. 92, 020404 (2004)PRLTAO0031-900710. 1103/PhysRevLett.92.020404] raises the possibility of momentum transfer from zero-point quantum fluctuations to matter, controlled by applied electric and magnetic fields. We present a Lorentz-invariant description using field-theoretical regularization techniques. We find no momentum transfer for homogeneous media, but predict a very small transfer for a Casimir-type geometry.An oldie but goodie. These are the older papers. Note the bold part.I bet that having those PE discs smashed up against each other and the copper is important! From what Paul reported, it is. Here's why I think so:http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329454#msg1329454http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329531#msg1329531 Quoting me.QuoteAbout half the time when I think this through, the darn thing thrusts backwards.Quoting @Paul March http://forum.nasaspaceflight.com/index.php?topic=36313.msg1335190#msg1335190Quote.....it was producing less than half of what it did before and in the wrong direction!......Apparently not having the PE discs firmly mounted to the frustum's small OD end cap hindered the thrust producing mechanism that conveys the generated forces in the PE to the copper frustum. Paul, would you be willing to introduce a small gap between the copper and PE as a test? Like tighten down the Nylon bolts and wedge a wooden shim in there?Also, I know this is kinda high speed, but do you have any gold leaf? To wedge between the PE and Copper? http://en.wikipedia.org/wiki/Gold_leaf#Culinary_usesThe reason I'm saying all this is, if we're gonna call these things Quantum Vacuum thrusters, we need to treat it like a Casimir experiment, instead of a plasma thruster.Break: IRT the new stuff I've been posting about PT symmetry, this is a nice plain english rundown of how it works from different people, saying the same thing as the other researchers.http://www.lap.physik.uni-erlangen.de/lap/?page=research_krstic_chiral&language=en (Also see those references at the bottom, this is very exciting stuff. I think I may actually be right on this one )And onto the subject of the Nylon bolts:So there's a bunch of different types of nylon. Anyone know what kind of nylon those bolts might be made of? Wouldn't it be something if nylon was doing some of the thrusting the whole time.I feel really goofy right now holding a mirror up to the computer screen.
....Treat this thing as a large collection of Casimir Cavities, might work if I can convince Dr. White to do so, and only after we both read through your referenced papers on the topic. And oh yes, get to Glenn Research Center for a successful replication of what we've seen to date before the end of March, or I may find myself in retirement before I was ready.....
Quote from: Star-Drive on 02/22/2015 11:17 pm....Treat this thing as a large collection of Casimir Cavities, might work if I can convince Dr. White to do so, and only after we both read through your referenced papers on the topic. And oh yes, get to Glenn Research Center for a successful replication of what we've seen to date before the end of March, or I may find myself in retirement before I was ready.....I put the emphasis on: get to Glenn Research Center for a successful replication of what we've seen to date before the end of March, or I may find myself in retirementThat would be a horrible waste of human talent and experience, somebody extremely difficult to replace, particularly after demonstrating that the EM Drive works in a hard vacuum, and given the better funded efforts in China, that the US should match or exceed.Those who think that the EM Drive technology is being pursued "under wraps" in the US appear to be misinformed and disconnected from Aerospace Companies Mgt and federally-funded R&D.There is a shortfall of funds at NASA, and federally-funded R&D in general under present budget conditions.There is barely more than one month left until the end of March.People interested in the EM Drive: this shortfall of funds is real, and EM Drive R&D in the US is in clear and present danger.
By the looks of things, there will be another "sputnik" moment--but this time it will be the Chinese not the Russians, and the EM Drive not the satellite. As much as I'd like to see the US stay out ahead on this one, if the new sputnik-EM Drive-China moment needs to happen to revive the support of the US government and spur a corresponding rise in NASA's budget, then let's hope it happens, and soon.