Consider the typical SRF cavities described in this paper: http://arxiv.org/pdf/physics/0003011.pdfEach cell in the stack of cavities could be thought of as being two cones arranged back to back: <><><><> (see Figure 5). We would then expect any forces to try and pull the two half-cavities apart.These were operated at 1.3 GHz, 200 kW CW RF, with a measured Q of ~ 5e9. Applying the quoted formula of F ~ Po*Q/c, we get a force of 3e6 N.The cavities have a wall thickness of about 2 mm, and a major radius of ~100 mm, giving a strain of > 2000 MPa in the niobium. The yield strength of niobium is somewhere in the range of 80-150 MPa, depending on temper and annealing. And yet the cavities did not fly apart.Anyone care to poke holes in this?

I'm incredibly appreciate of all the work that went into the dimensional estimates of the various drives but I'm having some difficulty understanding where the dimensional values came from regarding the attached image:Shawyer reported a large plate diameter of .28m - so using that as a given.Going straight off the image (not taking into account perspective) at the junction of the cone and the cylinder I get about .169m for the small plate diameter. This is a difference of 40mm with what was originally estimated and about 73mm from Dr. Rodal's calculation (96.13) of the small plate diameter. This is an enormous difference and I can't believe it. I'm going to model this and lay it on top of the photo in perspective so I can find out what the numbers are closer to.Also the cone length was estimated to be .345m - which is larger than the plate diameter. Between which two points is this measurement for?

Quote from: StrongGR on 05/20/2015 12:13 pmAs promised I am posting the latest draft about general relativity and electromagnetic field. The relevant conclusion is that there is thrust. Thanks to the comments by Jose Rodal, it can be shown that this can be meaningful and the best geometry is that of the frustum tending to a cone. There is no violation of conservation law due to the presence of the gravity that can escape the device producing a reaction.I post it here for your comments that are very welcome as usual. You can find the final equation at page 12 for your evaluations. Later on, I will post a version with a somewhat different presentation to arxiv.I like you paper but have a request for a point of clarification. I got really confused when you went from equation 55 to equation 56. Why did you invert the c^{4}/G term? (Actually I got confused way before that but I won't go there.

As promised I am posting the latest draft about general relativity and electromagnetic field. The relevant conclusion is that there is thrust. Thanks to the comments by Jose Rodal, it can be shown that this can be meaningful and the best geometry is that of the frustum tending to a cone. There is no violation of conservation law due to the presence of the gravity that can escape the device producing a reaction.I post it here for your comments that are very welcome as usual. You can find the final equation at page 12 for your evaluations. Later on, I will post a version with a somewhat different presentation to arxiv.

Quote from: StrongGR on 05/20/2015 05:46 pmQuote from: hhexo on 05/20/2015 05:42 pmr2=10^5.5r1=1is a correct example.It is my approximation: r2 increasingly large and r1 decreasing toward zero otherwise one should change the final formula. So, in your example it would be better to have r2=10 m and r1=10^-3 m and so on. This is a cone. Yes. But the dependence on r2 is stronger than the one on r1, because r2 is to the sixth power whereas r1 is just squared.So: if you keep r1 constant and vary r2, you don't need many orders of magnitude to have a reasonable effect; if you keep r2 constant and vary r1, you need to go down a lot of orders of magnitude.If we have an r2 of one meter, r1 must be 10^-16, which is a tenth of a femtometer, which is less than the size of a proton. We cannot possibly manufacture such a cone and I think it would not work anyway because the resulting "small end plate" doesn't have enough electrons to behave like an ideal EM-reflecting plate. Although maybe it doesn't need to and it's just the cavity shape that matters.What if we considered other shapes? We started with the truncated cone because of the EmDrive, but what if we considered a pillbox cavity (which is basically a rounded cone...)? All the equations would be different, for sure, but it might be worth exploring. Maybe in another thread. Quote from: StrongGR on 05/20/2015 05:46 pmAnother way around, as suggested above, is to fill with some material the cavity. The formula goes like mur^-2 and mur much smaller than 1.Yes, varying mu may be profitable too.

Quote from: hhexo on 05/20/2015 05:42 pmr2=10^5.5r1=1is a correct example.It is my approximation: r2 increasingly large and r1 decreasing toward zero otherwise one should change the final formula. So, in your example it would be better to have r2=10 m and r1=10^-3 m and so on. This is a cone.

r2=10^5.5r1=1is a correct example.

Another way around, as suggested above, is to fill with some material the cavity. The formula goes like mur^-2 and mur much smaller than 1.

Quote from: aero on 05/20/2015 06:19 pmQuote from: StrongGR on 05/20/2015 12:13 pmAs promised I am posting the latest draft about general relativity and electromagnetic field. The relevant conclusion is that there is thrust. Thanks to the comments by Jose Rodal, it can be shown that this can be meaningful and the best geometry is that of the frustum tending to a cone. There is no violation of conservation law due to the presence of the gravity that can escape the device producing a reaction.I post it here for your comments that are very welcome as usual. You can find the final equation at page 12 for your evaluations. Later on, I will post a version with a somewhat different presentation to arxiv.I like you paper but have a request for a point of clarification. I got really confused when you went from equation 55 to equation 56. Why did you invert the c^{4}/G term? (Actually I got confused way before that but I won't go there. I have taken out a l0^-1 that so becomes l0^-2.

Quote from: StrongGR on 05/20/2015 07:42 pmQuote from: aero on 05/20/2015 06:19 pmQuote from: StrongGR on 05/20/2015 12:13 pmAs promised I am posting the latest draft about general relativity and electromagnetic field. The relevant conclusion is that there is thrust. Thanks to the comments by Jose Rodal, it can be shown that this can be meaningful and the best geometry is that of the frustum tending to a cone. There is no violation of conservation law due to the presence of the gravity that can escape the device producing a reaction.I post it here for your comments that are very welcome as usual. You can find the final equation at page 12 for your evaluations. Later on, I will post a version with a somewhat different presentation to arxiv.I like you paper but have a request for a point of clarification. I got really confused when you went from equation 55 to equation 56. Why did you invert the c^{4}/G term? (Actually I got confused way before that but I won't go there. I have taken out a l0^-1 that so becomes l0^-2.Sorry, but I still don't understand how that converts c^{4}/G to (c^{4}/G)^{-1}.I suspect that there is a transcription error somewhere, and that (c^{4}/G)^{-1} was intended all along.

I'm incredibly appreciate of all the work that went into the dimensional estimates of the various drives but I'm having some difficulty understanding where the dimensional values came from regarding the attached image:Shawyer reported a large plate diameter of .28m - so using that as a given.Going straight off the image (not taking into account perspective) at the junction of the cone and the cylinder I get about .169m for the small plate diameter. This is a difference of 40mm with what was originally estimated and about 73mm from Dr. Rodal's calculation (96.13) of the small plate diameter. This is an enormous difference and I can't believe it. I'm going to model this and lay it on top of the photo in perspective so I can find out what the numbers are closer to.Also the cone length was estimated to be .345m - which is greater than the large plate diameter. Between which two points is this measurement for?

Where did you (Rodal) get the design factor of .844 that you used in calculating the small diameter of .09613m?

Quote from: phaseshift on 05/20/2015 09:04 pm..Shawyer reported a large plate diameter of .28m - so using that as a given...I'm almost certain that the small plate diameter is close to .17m. This produces a design factor of .5197. ...No, it is even worse, using that value for the small diameter (0.17 m), the DesignFactor (calculated with this equation http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ) is even smaller:smallDiameter = 0.17 m;bigDiameter = 0.28 m;f = 2.45*10^9 Hz;cst = 1.7062895542683174; cM = 299705000 m/s (speed of light in air);results in the following DesignFactorDesign Factor = 0.4853 (instead of the 0.5197 value you quoted above)

..Shawyer reported a large plate diameter of .28m - so using that as a given...I'm almost certain that the small plate diameter is close to .17m. This produces a design factor of .5197. ...

Quote from: phaseshift on 05/20/2015 09:49 pmQuote from: Rodal on 05/20/2015 09:32 pmQuote from: phaseshift on 05/20/2015 09:04 pm..Shawyer reported a large plate diameter of .28m - so using that as a given...I'm almost certain that the small plate diameter is close to .17m. This produces a design factor of .5197. ...No, it is even worse, using that value for the small diameter (0.17 m), the DesignFactor (calculated with this equation http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ) is even smaller:smallDiameter = 0.17 m;bigDiameter = 0.28 m;f = 2.45*10^9 Hz;cst = 1.7062895542683174; cM = 299705000 m/s (speed of light in air);results in the following DesignFactorDesign Factor = 0.4853 (instead of the 0.5197 value you quoted above)Which is interesting given that his experimental thruster had a DF of .497. So I don't know if he incorrectly reported .844 or the equation is wrong. I can say for certain that the small plate diameter in the photo is not even close to 96mm - I couldn't be that much off with my eyes closed lolI can see people next stating that Shawyer just transposed the numbers: he meant to write DesignFactor = 0.484 (which gives a sD = 0.17027 m)but he wrote insteadDesignFactor =0.844

Quote from: Rodal on 05/20/2015 09:32 pmQuote from: phaseshift on 05/20/2015 09:04 pm..Shawyer reported a large plate diameter of .28m - so using that as a given...I'm almost certain that the small plate diameter is close to .17m. This produces a design factor of .5197. ...No, it is even worse, using that value for the small diameter (0.17 m), the DesignFactor (calculated with this equation http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ) is even smaller:smallDiameter = 0.17 m;bigDiameter = 0.28 m;f = 2.45*10^9 Hz;cst = 1.7062895542683174; cM = 299705000 m/s (speed of light in air);results in the following DesignFactorDesign Factor = 0.4853 (instead of the 0.5197 value you quoted above)Which is interesting given that his experimental thruster had a DF of .497. So I don't know if he incorrectly reported .844 or the equation is wrong. I can say for certain that the small plate diameter in the photo is not even close to 96mm - I couldn't be that much off with my eyes closed lol

Quote from: Rodal on 05/20/2015 09:53 pm...I can see people next stating that Shawyer just transposed the numbers: he meant to write DesignFactor = 0.484 (which gives a sD = 0.17027 m)but he wrote insteadDesignFactor =0.844 Yes, good possibility - I did the EXACT same thing about 10 minutes ago.

...I can see people next stating that Shawyer just transposed the numbers: he meant to write DesignFactor = 0.484 (which gives a sD = 0.17027 m)but he wrote insteadDesignFactor =0.844

I suggest that we wait for the person who has read most of Shawyer's papers (TheTraveller). Perhaps TheTraveller can find another paper on the Demonstrator Engine by Shawyer besides the one I quoted, and check whether Shaywer quotes the same DesignFactor 0.844 or the more sensible number 0.484

Quote from: Rodal on 05/20/2015 10:04 pmI suggest that we wait for the person who has read most of Shawyer's papers (TheTraveller). Perhaps TheTraveller can find another paper on the Demonstrator Engine by Shawyer besides the one I quoted, and check whether Shaywer quotes the same DesignFactor 0.844 or the more sensible number 0.484This is my source: http://www.emdrive.com/IAC-08-C4-4-7.pdf

But then you have that U_0^4 that depends on Q^2 and P^2. As said before, I am not certain that I get a really macroscopic effect even if an interferometric device, sensible enough, can grant observation of the effect. I have to work out some numerics to see really what is going on. There is also the contribution coming from the square of the mode that can take the effect down.