Quote from: TheTraveller on 07/26/2015 06:54 PMWhat I can't understand about Tajmar's build is he could have easily duplicated Shawyer's 1st Experimental EMDrive ...This Tajmar mini EMDrive is really a very strange build.Tajmar's paper: Quote We would like to thank Roger Shawyer for his assistance

What I can't understand about Tajmar's build is he could have easily duplicated Shawyer's 1st Experimental EMDrive ...This Tajmar mini EMDrive is really a very strange build.

We would like to thank Roger Shawyer for his assistance

Would it be correct to say that the Shawyer construction injects the microwaves near the top or small end, rather than from the sides? There was definitely discussion of this previously but I can't seem to find it.

Have been told the max return loss was an estimated 12.5dBs.This is a terrible result with at best 360Ws making it into the cavity and then only if the cavity bandwidth is wide enough to handle the magnetron's power output bandwidth. If not then even less power gets inside the cavity and even more gets rejected and reflected back to the magnetron to heat it up.Sorry but a terrible design and build.

Quote from: TheTraveller on 07/26/2015 07:34 PMHave been told the max return loss was an estimated 12.5dBs.This is a terrible result with at best 360Ws making it into the cavity and then only if the cavity bandwidth is wide enough to handle the magnetron's power output bandwidth. If not then even less power gets inside the cavity and even more gets rejected and reflected back to the magnetron to heat it up.Sorry but a terrible design and build.Given the information we have from the paper and this new information whats the Df

Who from this forum is going to be at the AIAA conference?

Quote from: WarpTech on 07/26/2015 06:19 PMQuote from: X_RaY on 07/26/2015 05:56 PM@WarpTechwas confused yesterday caused by the notification "kr". Dr Rodal posted the description of what is meaning it (namely not the radii of the cone at a given point at the z-axis, but the radius based on the cone apex).@Rodal Thanks for the explanationhttp://forum.nasaspaceflight.com/index.php?topic=37642.msg1409751#msg1409751I'm not confused by this. I know that kr = k*r, is the distance from the cone apex in terms of phase. I agree the paper is confusing in the way it is written because they also use k_{r}. In my equation for the tapered cylinder using Bessel functions, I had z*w/c, which is the same thing. For a given k value based on the input frequency, k being the wavenumber of the propagating mode in the z direction, r is the distance from the apex. It is simply their way of normalizing the graph, because computing the Hankle functions is easier that way. The graphs I posted for the Reissner-Nordstrom metric are equivalent representations for k=1, where r is the radial coordinate. It is the radial solution for a charged black hole. What is wrong with that? What we are dealing with is a frequency dependent, electromagnetic metric. It does not affect matter the way normal gravity would, but it does effect the EM waves that fall in the right bandwidth in such a way as to mimic gravity. ToddIs your underlying idea that the expanding photon gas give some extra thrust? May be in such a situation you described (open horn antenna?) could be more thrust like simple photon rocket.(expanding of the photon gas plus backreaction while radiation?)For conical cavity thrusters who are not spitz and closed to be a resonator the situation is different? I am not sure.Some times ago i had a similar idea...Look at point "2."http://forum.nasaspaceflight.com/index.php?topic=37642.msg1382616#msg1382616Or do you think this is at the end a pure gravity effect?

Quote from: X_RaY on 07/26/2015 05:56 PM@WarpTechwas confused yesterday caused by the notification "kr". Dr Rodal posted the description of what is meaning it (namely not the radii of the cone at a given point at the z-axis, but the radius based on the cone apex).@Rodal Thanks for the explanationhttp://forum.nasaspaceflight.com/index.php?topic=37642.msg1409751#msg1409751I'm not confused by this. I know that kr = k*r, is the distance from the cone apex in terms of phase. I agree the paper is confusing in the way it is written because they also use k_{r}. In my equation for the tapered cylinder using Bessel functions, I had z*w/c, which is the same thing. For a given k value based on the input frequency, k being the wavenumber of the propagating mode in the z direction, r is the distance from the apex. It is simply their way of normalizing the graph, because computing the Hankle functions is easier that way. The graphs I posted for the Reissner-Nordstrom metric are equivalent representations for k=1, where r is the radial coordinate. It is the radial solution for a charged black hole. What is wrong with that? What we are dealing with is a frequency dependent, electromagnetic metric. It does not affect matter the way normal gravity would, but it does effect the EM waves that fall in the right bandwidth in such a way as to mimic gravity. Todd

@WarpTechwas confused yesterday caused by the notification "kr". Dr Rodal posted the description of what is meaning it (namely not the radii of the cone at a given point at the z-axis, but the radius based on the cone apex).@Rodal Thanks for the explanationhttp://forum.nasaspaceflight.com/index.php?topic=37642.msg1409751#msg1409751

Tajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Dielectric = NoneFrequency = 2.44GhzInput Power = 700w (output of magnetron)are that really the diameters used in the paper?(i dont have the paper )Is it possible that this are the radii? if i look at the picture the height is almost equal to the a-side of the waveguide...the a-side of WR430=109,22mm and WR340=86,36mmthe big diameter is almost equal to that

Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor. A standard WR340 waveguide was then used to connect the magnetron to the EMDrive.

Quote from: X_RaY on 07/26/2015 09:10 PMTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Dielectric = NoneFrequency = 2.44GhzInput Power = 700w (output of magnetron)are that really the diameters used in the paper?(i dont have the paper )Is it possible that this are the radii? if i look at the picture the height is almost equal to the a-side of the waveguide...the a-side of WR430=109,22mm and WR340=86,36mmthe big diameter is almost equal to that Quote from: M. Tajmar and G. Fiedler Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor. A standard WR340 waveguide was then used to connect the magnetron to the EMDrive. 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. Fiedler51st AIAA/SAE/ASEE Joint Propulsion Conference http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

Third, because the cavity geometry is axisymmetric, you can use the free RF program Superfish to determine the modes in the cavity, the best place to excite each mode, and the Q of each cavity mode. Superfish will run fine on a PC. Many accelerators far more complex than what you are doing were designed using Superfish and its support programs. The program will allow you to see the field patterns for the different cavity modes, which is helpful.

Quote from: Rodal on 07/26/2015 06:31 PMQuote from: frobnicat on 07/26/2015 06:29 PMThose with access to the paper can check that maybe the vertical set-up of frustum (on horizontal balance measurement) is with the waveguide axis aligned with arm : if we define a plane with both the axis of frustum and axis of waveguide, thrust would be expected only in this plane of symmetry, if this plane is parallel to vertical axis of rotation it would come as a surprise that there is some measured thrust vector orthogonal to such plane of symmetry, by symmetry argument alone, regardless of possible mechanisms unless some very strong (and strange) kind of parity breaking, i.e. naming axis of frustum is X and waveguide is (roughly orthogonal) Y it's like measuring net thrust on Z, sorry for the clumsy wording...Thanks, I have authorized access to the paper but I had not checked that. What figure in the paper are you referring to ? is it this one?

Quote from: frobnicat on 07/26/2015 06:29 PMThose with access to the paper can check that maybe the vertical set-up of frustum (on horizontal balance measurement) is with the waveguide axis aligned with arm : if we define a plane with both the axis of frustum and axis of waveguide, thrust would be expected only in this plane of symmetry, if this plane is parallel to vertical axis of rotation it would come as a surprise that there is some measured thrust vector orthogonal to such plane of symmetry, by symmetry argument alone, regardless of possible mechanisms unless some very strong (and strange) kind of parity breaking, i.e. naming axis of frustum is X and waveguide is (roughly orthogonal) Y it's like measuring net thrust on Z, sorry for the clumsy wording...Thanks, I have authorized access to the paper but I had not checked that. What figure in the paper are you referring to ? is it this one?

Those with access to the paper can check that maybe the vertical set-up of frustum (on horizontal balance measurement) is with the waveguide axis aligned with arm : if we define a plane with both the axis of frustum and axis of waveguide, thrust would be expected only in this plane of symmetry, if this plane is parallel to vertical axis of rotation it would come as a surprise that there is some measured thrust vector orthogonal to such plane of symmetry, by symmetry argument alone, regardless of possible mechanisms unless some very strong (and strange) kind of parity breaking, i.e. naming axis of frustum is X and waveguide is (roughly orthogonal) Y it's like measuring net thrust on Z, sorry for the clumsy wording...

Notice from the COMSOL FEA picture of the electromagnetic field in my post http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409813#msg1409813that the waveguide is NOT aligned with the center axis of axi-symmetry of the truncated cone EM Drive.

If you were to cut the EM Drive truncated cone along a plane intersecting the axis of axi-symmetry where the electromagnetic field is shown in the COMSOL image, the waveguide enters the EM Drive completely on the 1/2 of the EM Drive. The center axis of the waveguide is way off, away from the plane where the electromagnetic field is shown.Thus << if we define a plane with both the axis of frustum and axis of waveguide>> is not the correct plane, because the waveguide is entering the EM Drive off-axis.Could you envision a torque, due to the waveguide entering the EM Drive not symmetrically, resulting from two thrust vectors: one thrust vector aligned with the axis of axi-symmetry of the EM Drive and the other axis being the axis of the waveguide?Imagine a vertical vector (due to the EM Drive cone) and a horizontal force vector that is acting at a distance R from the vertical vector. This seems to result in a torque. If everything is rigid, this torque is reacted by the table, and it may show up as a torsional displacement, registering as a horizontal force (which arises from the torque produced by the waveguide acting asymmetrically).

Tajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Dielectric = NoneFrequency = 2.44GhzInput Power = 700w (output of magnetron)are that really the diameters used in the paper?(i dont have the paper )Is it possible that this are the radii? if i look at the picture the height is almost equal to the a-side of the waveguide...the a-side of WR430=109,22mm and WR340=86,36mmthe big diameter is almost equal to that 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. Fiedler51st AIAA/SAE/ASEE Joint Propulsion Conference http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083if everyone is able to share a link to the paper (without the need to pay for) please send me a PM

Quote from: X_RaY on 07/26/2015 09:10 PMTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Dielectric = NoneFrequency = 2.44GhzInput Power = 700w (output of magnetron)are that really the diameters used in the paper?(i dont have the paper )Is it possible that this are the radii? if i look at the picture the height is almost equal to the a-side of the waveguide...the a-side of WR430=109,22mm and WR340=86,36mmthe big diameter is almost equal to that 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. Fiedler51st AIAA/SAE/ASEE Joint Propulsion Conference http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083if everyone is able to share a link to the paper (without the need to pay for) please send me a PMUsing the WR340 flange narrow dimensions I estimate the big end diameter at 110mm, which very strongly suggests the big and small end diameters are radius and not diameters as claimed.Likewise the cavity length when compared to the flange longer length suggests it too has been half sized.This suggests all the dimensions need to be doubled.With those mods and assuming the length is the overall length and not the inside length with the screwed in small end plate, it is possible to get TE111 resonance at 2.45GHz. Df is 0.562. At 700W input and a Q of 48.8 the Force prediction is 128uN, which means their Df is lower than 0.562 or they have other numbers wrong.

We started by designing a model optimized for a frequency of 2.45 GHz using COMSOL in order to be able to use commercial magnetrons used in standard microwave ovens. We iterated our design several times by consulting with R. Shawyer to be as representative as possible. Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor. A standard WR340 waveguide was then used to connect the magnetron to the EMDrive.

Regarding the dimensions the paper was explicit. (Maybe wrong but explicit.)QuoteWe started by designing a model optimized for a frequency of 2.45 GHz using COMSOL in order to be able to use commercial magnetrons used in standard microwave ovens. We iterated our design several times by consulting with R. Shawyer to be as representative as possible. Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor. A standard WR340 waveguide was then used to connect the magnetron to the EMDrive.From "Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects M. Tajmar and G. Fiedler"51st AIAA/SAE/ASEE Joint Propulsion Conferencehttp://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

Quote from: X_RaY on 07/26/2015 09:10 PMTajmar Experimental resultsCavity Length(m) = 0.0686Big Diameter(m) = 0.0541Small Diameter(m) = 0.0385Dielectric = NoneFrequency = 2.44GhzInput Power = 700w (output of magnetron)are that really the diameters used in the paper?(i dont have the paper )Is it possible that this are the radii? if i look at the picture the height is almost equal to the a-side of the waveguide...the a-side of WR430=109,22mm and WR340=86,36mmthe big diameter is almost equal to that 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. Fiedler51st AIAA/SAE/ASEE Joint Propulsion Conference http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083if everyone is able to share a link to the paper (without the need to pay for) please send me a PMUsing the WR340 flange narrow dimensions I estimate the big end diameter at 110mm, which very strongly suggests the big and small end diameters are radius and not diameters as claimed.Likewise the cavity length when compared to the flange longer length suggests it too has been half sized.This suggests all the dimensions need to be doubled.With those mods and assuming the length is the overall length and not the inside length with the screwed in small end plate, it is possible to get TE111 resonance at 2.45GHz. Df is 0.562. At 700W input and a Q of 48.8 the Force prediction is 128uN, which means their Df is lower than 0.562 or they have other numbers wrong.In quoting 700W as the cavity input power, it would seem Tajmar doesn't understand what a return loss dB of 12.5 means and that it drops his 700Ws to 360Ws at best. Any person who understands VSWR would know what a 69:1 VSWR means, which is your Rf generator is gonna get very HOT from the reflected power.Using 360Ws as the cavity input power, the Force prediction drops to 66uNs and at an oxidised Q of 20.2 it drops further to 27uNs.

Whats the predicted thrust if you drop the 700W to 360W using the initial Q of 48.8? Also what do the numbers look like if you assume the model that was used was the one in equation 1 of The Development of a Microwave Engine for Spacecraft Propulsion