(...)Table 3, page 28 of the original Chinese paper shows:Vertical Axis: ( (Frequency[Hz] * Diameter[cm] )/(Hz*cm) )2 * 10- 20Horizontal Axis: (Diameter / Height)2I didn't have the time yet to chase what Diameter is she referring to.To me it is a table for mode shapes in terms of natural frequency and geometry.Let me know what you think
Quote from: TheTraveller on 05/24/2015 08:13 pmQuote from: deltaMass on 05/24/2015 08:06 pmThis discussion is clearly interminable, in the literal sense of that word. Whatever experimental results accrue, in past, present or future, there will always be doubt. This is why I am so strongly in favour of a space-based test. I've already laid out my reasons. Without that, I'd lay odds that one could return to this forum in years to come and people would still be arguing the toss.Let's cut the Gordian Knot!The test program I plan to run will remove ALL doubt that the EMDrive generates real propellantless thrust without needing a space test. One of my goals is to be able to hold the EMDrive & while switching it on and off, to be able to FEEL the thrust.You may have posted it somewhere before Traveller, but I haven't had the chance to read the entirety of threads 1 and 2. Do you have a general idea of what kind of timeline you are going to be working off of with your test program? Do you expect to have a build ready in the next two months, with another month or two for testing, or do you expect it take longer?Just trying to get a sense of experimental development on this device given we can't expect EW results until at least late July.
Quote from: deltaMass on 05/24/2015 08:06 pmThis discussion is clearly interminable, in the literal sense of that word. Whatever experimental results accrue, in past, present or future, there will always be doubt. This is why I am so strongly in favour of a space-based test. I've already laid out my reasons. Without that, I'd lay odds that one could return to this forum in years to come and people would still be arguing the toss.Let's cut the Gordian Knot!The test program I plan to run will remove ALL doubt that the EMDrive generates real propellantless thrust without needing a space test. One of my goals is to be able to hold the EMDrive & while switching it on and off, to be able to FEEL the thrust.
This discussion is clearly interminable, in the literal sense of that word. Whatever experimental results accrue, in past, present or future, there will always be doubt. This is why I am so strongly in favour of a space-based test. I've already laid out my reasons. Without that, I'd lay odds that one could return to this forum in years to come and people would still be arguing the toss.Let's cut the Gordian Knot!
Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.http://www.supergluecorp.com/super-glue/epoxies/copper-bond Does anyone have an opinion on this joining method?
Quote from: TheTraveller on 05/25/2015 11:37 amPlan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.http://www.supergluecorp.com/super-glue/epoxies/copper-bond Does anyone have an opinion on this joining method?I would go for an old fashioned soldering. Why introduce another unknown variables caused by the glue?BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.
You'll need to verify how the epoxy glue reacts to temperature, because your frustum will get hot...Migth also need to roughen the exterior to give the epoxy a better adherence.0.5mm thickness will most likely warp when soldering, so I'd go for the glue+strip on the outside.Then the challenge will be to get the 2 edges align according the curve of the cone, as they will tend to angle. The strip you place on top of it, will need to be slightly curved also...
@TheTravellerRe. the join - you may find that you don't get all the way down to the original resistivity with that approach, and the EM will see a resistive discontinuity, which will distort mode shapes in some way. But I can't say if this is a major or minor effect. Indium might be better, but I'm unsure how you'd apply it. It's usually used in a pressure fit. My gut tells me that what you propose is good enough.Re. the RF feed - you'll want to do all drilling (air vents too) before soldering the final end cap on, else you might leave copper scurf rattling around in there. This will tend to lower the Q. The placement of the RF feed hole is rather chicken-and-egg because you won't know the impedance to be matched until you use it. That's unless you or someone else can calculate it. This problem is exacerbated if you don't have variable frequency ability. Perhaps instead you're going for the variable end plate approach. In any case, you're going to need something to do the impedance matching. Paul March started out using a "trombone" style matcher for this, and now has something considerably more sophisticated.Re. venting heated air - this will cause the weight to change as dm = d(rho)*V*g Newton, where d(rho) is the change in air density between the two temperatures and V is the cavity volume. If you are weighing the cavity then this will obviously be a significant factor. Fortunately it can be cancelled away by flipping the cavity upside down, since thenF + dm = apparent (measured) upthrust = weight lossF - dm = apparent (measured) downthrust = weight gainwhere F is the true thrust.Solve for F, dm as usual:F = (up + down) / 2dm = (up - down) / 2
Quote from: Rodal on 05/25/2015 02:26 am(...)Vertical Axis: ( (Frequency[Hz] * Diameter[cm] )/(Hz*cm) )2 * 10- 20...... I don't understand the 10^-20 yet unless it's just unit fixing...
(...)Vertical Axis: ( (Frequency[Hz] * Diameter[cm] )/(Hz*cm) )2 * 10- 20...
...I also think I found a (minor?) error in the 2013 paper. In my estimation, equations 4 and 6 are correct. Where I disagree is that her premise is that there are charged particles in the volume, and then on equations 7 and 8, she removes the particle momentum density and the energy density of the field, for no apparent reason and then IMO, she abruptly ends the section....
If the microwave electromagnetic field consists of charge particles, due to theelectromagnetic force, the charge particles can travel within the electromagneticfield, so the charge particles can acquire energy and momentum from theelectromagnetic field. This indicates that electromagnetic field have energy andmomentum.
The microwave electromagnetic field of charged particles , if present , due to the electromagnetic force
Quote from: Paul Novy on 05/25/2015 11:52 amQuote from: TheTraveller on 05/25/2015 11:37 amPlan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.http://www.supergluecorp.com/super-glue/epoxies/copper-bond Does anyone have an opinion on this joining method?I would go for an old fashioned soldering. Why introduce another unknown variables caused by the glue?BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.Thanks for the comment.I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.
Quote from: TheTraveller on 05/25/2015 12:04 pmQuote from: Paul Novy on 05/25/2015 11:52 amQuote from: TheTraveller on 05/25/2015 11:37 amPlan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.http://www.supergluecorp.com/super-glue/epoxies/copper-bond Does anyone have an opinion on this joining method?I would go for an old fashioned soldering. Why introduce another unknown variables caused by the glue?BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.Thanks for the comment.I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.That epoxy is not electrically conductive, is it? It's for pipes, not circuits so the electrical connection for currents to flow from end plates to side walls may be compromised. Try this;http://www.mgchemicals.com/products/adhesives/electrically-conductive/silver-conductive-epoxy-8331/
What the EmDrive thruster does is to produce a force, which we call the thrust, in one direction. This is a force that you can measure. If you put your hand against the end plate that's producing the thrust you'll feel it pushing against you. And, as with all machines that follow Newton's principles, it will therefore accelerate in the opposite direction. So this is not a reactionless thruster, because those things just don't exist outside of science fiction, but it is a propellantless thruster.
Quote from: WarpTech on 05/25/2015 05:16 am...I also think I found a (minor?) error in the 2013 paper. In my estimation, equations 4 and 6 are correct. Where I disagree is that her premise is that there are charged particles in the volume, and then on equations 7 and 8, she removes the particle momentum density and the energy density of the field, for no apparent reason and then IMO, she abruptly ends the section....Can you please elaborate why you think this is just a minor error by Prof. Yang and her co-authors?(And by the way, I am looking at the 2010 paper, not the 2013 paper, in my comments below)They write (2010 paper, translation page 4, original page 28)http://www.emdrive.com/NWPU2010translation.pdfQuoteIf the microwave electromagnetic field consists of charge particles, due to theelectromagnetic force, the charge particles can travel within the electromagneticfield, so the charge particles can acquire energy and momentum from theelectromagnetic field. This indicates that electromagnetic field have energy andmomentum. The microwave electromagnetic field inside the cavity is composed of photons (at microwave frequencies), which as we all know, have no charge whatsoever. So the microwave electromagnetic field does not consist of charge particles. This is the difference between Greg Egan's equations http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html, who finds no net thrust force, since he doesn't consider this term at all.If there are any charges and currents, they are only present in the copper metal (translation says "brass"), and not inside the empty microwave cavity. This seems to me a major issue, and not a minor point.EDIT: The original in Chinese says (my translation)QuoteThe microwave electromagnetic field of charged particles , if present , due to the electromagnetic force The "if present" seems to have been changed in the translation to "if it consists of". Either way, "If present" or "if it consists of" is a big if. We have to understand whether this condition is met, and if so, what are these charged particles.Are the authors considering charged particles to be present in the empty cavity? In essence are the authors effectively considering virtual charged particles like the QV of Dr. White ?Or are the authors considering having ionized air inside the cavity ?
...As mentioned I have silver epoxy and will be using it as the 1st 2 layers, then using the Copper/Metal epoxy for an overcoat. My experience with silver epoxy is that it doesn't have a lot of strength and can't be replied on to generate a physically strong joint...
I'll have to return to this quote again.QuoteWhat the EmDrive thruster does is to produce a force, which we call the thrust, in one direction. This is a force that you can measure. If you put your hand against the end plate that's producing the thrust you'll feel it pushing against you. And, as with all machines that follow Newton's principles, it will therefore accelerate in the opposite direction. So this is not a reactionless thruster, because those things just don't exist outside of science fiction, but it is a propellantless thruster.This behaviour with a force being felt from the "thrusting" end plate is also, assuming it is large enough, consistent with pressing on a bend in space time.If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.On a separate note, is it correct to say that the drive, as described by Shawyer has a duty cycle. That is it behaves like a pulse jet with bursts of thrust (v1 doodlebug). If so, is there experimental data to confirm this, or is the duty cycle so fast that it gets averaged out in measurement.