I've been spending a lot of time over the last weeks installing and learning to use an FDTD program. It has taken me longer than it should, but I first had to install a Linux OS, then a MATLAB like program and learn how to use them. I'm still learning but have my FDTD program running now with the Brady cavity modeled as best we could divine it.
Later tonight I'm going to hit it with a Gaussian pulse around 1880.4 MHz, and hope in the morning to have resonate frequencies and Q values from the dimensions we have. That run will take about 6 hours on my single thread installation. If I need to, I will adjust the length and/or the big end diameter in order to find the right Q value. I've taken the small end internal diameter to be the size of the PE resonator disc and will leave that dimension alone.
Anyway, that's what I've been working on and I hope to have something interesting soon. And I hope I don't need to install and learn to use the multi-processor version of the program. Six hour runs aren't very long but it does limit me to 2 or 3 runs a day, and I was hoping to look at other things besides Q and dimensions.
(I wish I could afford something like this -)
http://www.remcom.com/xf7?pi_ad_id=12808652781&gclid=CM_FsNvMg8ICFYdffgod4UQAqQ
To bad your neighbor or good friend isn't a spinner...
What's a spinner? I mean, what do I know. I'm just a
magazine publisher.
I may have a very shallow grasp of what can be done or not with microwaves (at what practical efficiencies) but isn't it possible to use a hollow waveguide and interrupt it for 1mm or so, I mean a waveguide with a fixed part linked to wall plugged RF amp, and a mobile part (coaxial with rotation). Would the leak be too big ? Is a waveguide simply not appropriate for efficient power transmission ?
As I understand (weakly, feel free to educate me) RF is "transverse" (E and B orthogonal to propagation) so maybe any power RF wireless transmission scheme might show intrinsic torque between mobile part and fixed part (waveguide or antenna), no ? This could be mitigated by sampling at various relative orientations, or by having a freely rotating part (full 360°) to integrate and even out any orientation dependency ...
I wonder if a light enough "carousel" mounted on a sapphire cup bearing (near point like contact) could have low enough stiction to measure 10ľN or so at ends of arm. See attached picture for the overall idea. Alternatively instead of a dry point like contact use a "floater bearing" in water (or liquid metal or low vapor pressure oil for vacuum compatibility). Probably high viscosity but no stiction.
Let it spin, measure thrust from acceleration profile first, then from equilibrium speed against viscosity. Check for periodic dependency of signal relative to angle of rotation (as "real" signal part wouldn't depend on that). Make the whole system as symmetric as possible around the axis (cylindrical walls around...).
Need to change the direction of the thrust and the direction of rotation in your pictures:
it should be pointing the other way around,
towards the bigger end, thus the rotation should be
clock-wise in your picture.
...
Need to change the direction of the thrust and the direction of rotation in your pictures:
pic...
it should be pointing the other way around, towards the bigger end, thus the rotation should be clock-wise in your picture.
Ah yes, this should be spinning this way (or not at all). Thanks.
Can add a thin window transparent to microwaves to isolate the chamber from ambient pressure and make partial vacuum inside. Rotation could be measured with a mirror + laser = optical lever for small displacements and/or optical coder if it does spin.
Question remains : can a cavity (or cavities) can be fed through a waveguide, with a small "gap" in it between a fixed part and coaxial moving part ? Would be convenient to have a wall-plugged RF amp and send only waves to a light apparatus. I know so far I demanded rather more demo with fully integrated system...
Just want to make sure (given the flipping of thrust arrows above that just happened) that the emdrive (if it actually works)
flies through the air pointy end first, right? Is the sign of thrust flipped in reaction less engines and I didn't get the memo?
Given the way the "thruster" is mounted in his space plane and the direction for cavity acceleration here:
http://www.emdrive.com/iac2014presentation.pdfThe signs for thrust are flipped in his presentation.
Anyone else in build mode now? I'm gathering materials now, rf connectors and the like.
@Ron Stahl:
I'm just noting you can't skimp on the balance and vacuum and have people take your findings seriously. Paul March had propellantless thrust in his extra bedroom in 2003-4 and no one took it seriously because he had no vacuum.
I'm not trying to be taken seriously. I'm not even taking this seriously. Building one is just for my enjoyment. I don't have access to a vacuum, nor will I spend more than a few bucks on this setup. What I'm going to do since I don't have vacuum, is put the test article inside a sealed container, pack it with tissue or foam to act as an air baffle and to distribute heat around evenly, and put that on the torsion balance.
Next subject:
Here's another emdrive theory paper I found:
https://hal.archives-ouvertes.fr/hal-01074608/documentThis guy says he can make it better even.
To bad your neighbor or good friend isn't a spinner...
What's a spinner? I mean, what do I know. I'm just a magazine publisher.
A spinner is a person or company who operates a spinning lathe. Google gives a long list of metal spinners, and some information. Look at the picture of the lathe and tools in the background.
http://en.wikipedia.org/wiki/Metal_spinningYou will note from the picture that they are using metal mandrels. That is for high quantity production. For low quantity production they use wooden mandrels, but wooden mandrels wear out after a few hundred uses. That is, they flake or pit so become useless. The tools are about a meter long with a lever mechanical advantage of 10 - 20, so when the operator lays his full strength into the lever, the pressure on the mandrel gets pretty intense for wood to bear.
Just want to make sure (given the flipping of thrust arrows above that just happened) that the emdrive (if it actually works) flies through the air pointy end first, right? Is the sign of thrust flipped in reaction less engines and I didn't get the memo?
Given the way the "thruster" is mounted in his space plane and the direction for cavity acceleration here:
http://www.emdrive.com/iac2014presentation.pdf
The signs for thrust are flipped in his presentation.
They claim they measured the thrust force pointing towards the big end, not the small end of the truncated cone.
Here is Shawyer's presentation the thrust is directed towards the big end.
http://4.bp.blogspot.com/-1a86Dh-Q6Rk/VFLSQlO8TgI/AAAAAAAA3x8/S2cXXAv3rcQ/s1600/emdrivedata.png[
That YouTube is for the demonstrator engine, which Shawyer states exhibited force direction in both "reaction" and "thrust":
take a look at his spreadsheet.
In the text of his paper
http://www.emdrive.com/IAC-08-C4-4-7.pdf Shawyer states: "The direction of acceleration was opposite to the direction of thrust". If by direction of acceleration he means the acceleration of the center of mass of the EM Drive and other equipment , this definition is opposite to the common definition of thrust However, NASA (Brady et al) also claim the thrust is pointing towards the big end.
Just want to make sure (given the flipping of thrust arrows above that just happened) that the emdrive (if it actually works) flies through the air pointy end first, right? Is the sign of thrust flipped in reaction less engines and I didn't get the memo?
Given the way the "thruster" is mounted in his space plane and the direction for cavity acceleration here:
http://www.emdrive.com/iac2014presentation.pdf
The signs for thrust are flipped in his presentation.
Both Shawyer and NASA define the thrust force in these devices as pointing towards the big flat end, away from the dielectric at the small end of the truncated cone.
I don't understand your sarcastic tone. Posting a video of Shawyer's "Demonstrator Engine" (which Shawyer claimed exhibited different measurements in "thrust" and "reaction" directions) moving in the opposite direction does not address the fact that NASA (Brady, March, White) and Shawyer defined the thrust as pointing towards the big end.
How do you address the fact that
NASA defined the measured thrust is pointing towards the big end, away from the dielectric?
See how NASA defines the thrust direction here (@35 minutes) towards the short end, consistent with Shawyer's spreadsheet, opposite from the dielectric located at the long end:
NASA defines the thrust direction they measured on the torsion pendulum towards the left, away from the dielectric:
<<<<<<<<<<<<<<<---------------------------------------------------------------------------------------
Rather than being sarcastic about it, we should discuss and understand why:
A) Shawyer and NASA define the thrust direction towards the big end,
B) Shawyer states that the acceleration is in the opposite direction of the thrust. This indeed is contrary to rocket and jet engines thrust definition. Also the rotation in the Shawyer video is in the opposite direction to the one he uses for thrust.
If NASA is also defining thrust in the opposite direction to jet engines and rocket engines, why is NASA using this wrong definition? Shouldn't NASA at least get this right?
Wasn't the movement of NASA's torsional pendulum towards the big end?
This adds to the confusion in these papers which makes anyone skeptical of the subject matter...
Anyone else in build mode now? I'm gathering materials now, rf connectors and the like.
@Ron Stahl:
I'm just noting you can't skimp on the balance and vacuum and have people take your findings seriously. Paul March had propellantless thrust in his extra bedroom in 2003-4 and no one took it seriously because he had no vacuum.
I'm not trying to be taken seriously. I'm not even taking this seriously. Building one is just for my enjoyment. I don't have access to a vacuum, nor will I spend more than a few bucks on this setup. What I'm going to do since I don't have vacuum, is put the test article inside a sealed container, pack it with tissue or foam to act as an air baffle and to distribute heat around evenly, and put that on the torsion balance.
Next subject:
Here's another emdrive theory paper I found:
https://hal.archives-ouvertes.fr/hal-01074608/document
This guy says he can make it better even.
Sounds like you need to have a fire extinguisher.
So what is the point? Suppose your balance moves. Then what? Suppose it doesn't move? Then what? You don't have any way to remove spurious sources so whether it moves or not, you won't have any kind of comnclusion you can make. So what is the point?
This is why I have said now several times, you need to put the bulk of the effort into the instrumentation, not the thruster. If you buy an acrylic aquarium:
http://www.ebay.com/itm/25-Gallon-Thick-Acrylic-Fish-Tanks-Various-Dimensions-/221398540134?pt=LH_DefaultDomain_0&hash=item338c619f66and a used used roughing pump (which may even not need to be rebuilt) the real work is putting an acoustic enclosure around the pump (so your wife doesn't leave you) and running the had line to the aquarium. It's really not that hard to do and all your other efforts will be worth something.
But you see why I am not a fan of unfunded efforts. They turn into this--which is useless as is.
If NASA is also defining thrust in the opposite direction to jet engines and rocket engines, why is NASA using this wrong definition? Shouldn't NASA at least get this right?
Wasn't the movement of NASA's torsional pendulum towards the big end?
This adds to the confusion in these papers which makes anyone skeptical of the subject matter...
They did get it right. The thrust is supposed to be generated to the larger end:
". . .Shawyer's paper includes the fundamental assertion underlying the theory: "[t]his force difference is supported by inspection of the classical Lorentz force equation F = q(E + νB). (1) If ν is replaced with the group velocity νg of the electromagnetic wave, then equation 1 illustrates that if vg1 is greater than vg2, then Fg1 should be expected to be greater than Fg2." This statement makes two assumptions which Shawyer does not substantiate and which may explain the discrepancy between Shawyer's predictions and those of conventional physics. First, Shawyer assumes that radiation pressure is the result of the Lorentz Force acting on charged particles in the reflecting material. This is refuted by Rothman and Boughn[36] and is not consistent with the standard theory of radiation pressure. Second, Shawyer asserts that quantum energy is transferred at the
group velocity, and thus momentum of the photon and the consequent radiation pressure must vary with group velocity. Photon momentum varies with
phase velocity. Group velocity measures the rate of propagation of information. The phase velocity is constant throughout the frustum resonator, consequently radiation pressure would not be expected to produce unbalanced forces."
http://en.wikipedia.org/wiki/EmDriveShawyer built this thing because he doesn't understand the difference between group velocity and phase velocity. If it is producing thrust, it is producing thrust by accident.
30 seconds in shows acceleration in the other direction
consistent with his statement, "The direction of acceleration was opposite to
the direction of thrust....." page 8 here:
http://www.emdrive.com/IAC-08-C4-4-7.pdfBut
inconsistent with slides 1, 2 and 3 here:
http://www.emdrive.com/iac2014presentation.pdfand the his video here:
http://emdrive.com/dynamictests.htmlMaybe it can be reversed. Much inconsistency here.
@Rodal
See how NASA defines the thrust direction here (@35 minutes) towards the short end, consistent with Shawyer's spreadsheet, opposite from the dielectric located at the long end:
That stuff about Cannae above....doesn't follow. We're talking about Shawyer's design here.
....
@RodalSee how NASA defines the thrust direction here (@35 minutes) towards the short end, consistent with Shawyer's spreadsheet, opposite from the dielectric located at the long end:
That stuff about Cannae above....doesn't follow. We're talking about Shawyer's design here.
Yes it follows:
1) This is a thread about EM Drives in general. Not a thread exclusively about Shawyer.
2) This thread has as much or more detailed discussion about the NASA experiments by Brady et.al than by Shawyer.
3) Shawyer refers to the NASA direction of thrust in his spreadsheet, which I reproduce again:
