-
#2980 by Rodal on 02 Jun, 2016 17:13
-
After 4 iterations of designing the torsion pendulum I've settled on this aluminum carbon fiber very lightweight platform.
This is a test wire and a little heavier for just testing.
You'll notice the threaded rods on the sides that will be used to beam ballance and the wire goes through the center of a small hole. The wire will be adjusted with weights in the Z and Y dimension on the platform to be in the center of the hole. This assures beam balance.
Underneath the U channel is where the wire is captured 1/2 way between the top and bottom and it's centered to the middle section of the carbon fiber tubes.
The wire tension is set by a guitar Tuner Tuning Peg Machine Head.
This setup even with the heavy wire is extraordinary sensitive and when I finish off the brackets for the frustum and sliding balance weight on the carbon fiber tubes I'll be finishing off the electronics to drive my frustums.
Just a update, back to work.
Shell
What a clean looking design. Marvelous ! -
#2981 by TheTraveller on 02 Jun, 2016 17:23
-
battery powered/solar powered portable microwave the size of a thermos bottle.
http://nextbigfuture.com/2016/05/solid-state-rf-technology-enables-cheap.html
This may be of interest to future DIYer EM drive projects
Of particular interest is:
"The technology platform includes NXP’s MKW40Z Kinetis microcontroller (MCU) with a 2.4 GHz signal generator, a MMA25312 pre-driver, MHT1008 driver and MHT1004 final stage amplifier into a single, integrated closed-loop module."
The MKW40Z Kinetis microcontroller comes in a BLE and wireless radio version. If they plan on making this work with your iphone... that would be even better.
Single frequency excitation with real time forward, reflected power feedback / force generation and very high cavity Q is the pathway to achieving good and reliable EmDrive thrust generation.
While a direct injected design (maggie antenna inside the frustum) is low cost, you need to understand the lack of control and feedback that you build into the system. EmDrive engineering bottom line is you need to be lucky to get any force generation and even then it may not be very reliable or very strong.
Design for maximum data feedback and wide operational single frequency operation.
While VNA data is OK for initial resonance scoping, you need to be able to tune to real time max forward and min reflected power (VSWR) as your start when applying power and to expect force generation.
Even then the best force generation freq may not be the best VNA rtn loss freq nor lowest VSWR freq. -
#2982 by SeeShells on 02 Jun, 2016 17:23
-
Shell,
The brass piece is
What hardware are you using to thread the wire through? I don't need to pass through completely like you, but I need something better to grab onto the wire. Please let me know.
http://www.ebay.com/itm/1-8-NPT-BRASS-PIPE-CAP-LOT-OF-5-/121761696359?hash=item1c59900a67:g:pmYAAOSwVL1V-aS0
I drilled a hole through both the bottom just a couple thousand larger than the wire. The top I did a little bigger to be able to visually see the wire to adjust the wire to the center.
To secure the wire to the bottom little hole I just did a square knot between two wires. It will provide a load point for your platform to set on without stressing your wire.
Got it?
Shell
Added: If you find that using just the piano wire square knot doesn't want to hold or might break then do another trick I had to do when I was using the heavy U channel. I made the square knot and then took some dental floss and tied off a larger knot of it above the square knot.
This provided a cushion on the wire square knot and a larger surface for the beam to rest on.
-
#2983 by Gilbertdrive on 02 Jun, 2016 17:30
-
I briefly touched on this a few months ago. I'm not in a position where I can experiment right now to verify because I'm in a state of flux of my own. Studying this thing for the past couple of years has me thinking that the resonant rf isn't the cause of the thrust (thousands of times better than a photon rocket), rather it's the perturbation needed. The non Newtonian motion of the matter in the cavity is the final cause. So I propose adding this. A visual:
Very impressive video.
When you speak of the perturbation, do you means the vibration of the cavity ? The movement of electrons in copper ? or other types of perturbations ?
I emitted the hypothesis earlier (and maybe some others before that I did not see) that the vibration could help to get periodically the resonance if the system is not perfectly calibrated. The sound in copper is around 4600 M/S. So, when a side of the frustrum moves, it takes some times before the other side is pushed or pulled. If the frustrum is not at the exact size required for good resonance, it may get good resonnance for a little period of time at each vibration. And, since the speed of light is around 65000 times the speed of the sound in copper, even if the resonance is maintained during one tenth of each vibration, it should work, with around one tenth of the thrust of an always resonnating emdrive. Of course, when Q is very high, the thrust would be less thant a tenth.
So, my hypothesis would explain that vibrations make the emdrive work, still in the theory where the resonance make the thrust
Added to the fact that the magnetrons does not make only the exact frequency, it may also help to get some resonnance when it is not perfectly collimated.
That should at the same time allow both magnetrons, and Solid state /RF Generators to work, and explain why the magnetron can not be just replaced in any build. In my hypothesis, only almost perfectly realized frustrum, would work with a non vibrating, and pure frequency generator. I remember that the Traveller told us how precise the frustrum had to be, referring to Shawyer. -
#2984 by zellerium on 02 Jun, 2016 17:58
-
I never noticed that graphic for Cannae. They use an asymmetric dialectric (cone, pyramid?) inside a symmetric cavity and NASA uses a symmetric dialectric insert in an asymmetric cavity. Those are the inverse of one another geometrically.
Cal Polytech used symmetric insert with symmetric cavity, correct? Did they ever try different shapes of HDPE, like a cone?
We only had a symmetric cylindrical HDPE disc, but a cone shape was recommended to us by the microwave industry professional who lent us the antenna. He anticipated that a gradually tapered dielectric would mimic a frustum very closely.
Roger Shawyer's first patent has a cone shaped dielectric
-
#2985 by X_RaY on 02 Jun, 2016 18:12
-
The optimal shape of a dielectric to act this way depends on the EM mode for sure.I never noticed that graphic for Cannae. They use an asymmetric dialectric (cone, pyramid?) inside a symmetric cavity and NASA uses a symmetric dialectric insert in an asymmetric cavity. Those are the inverse of one another geometrically.
Cal Polytech used symmetric insert with symmetric cavity, correct? Did they ever try different shapes of HDPE, like a cone?
We only had a symmetric cylindrical HDPE disc, but a cone shape was recommended to us by the microwave industry professional who lent us the antenna. He anticipated that a gradually tapered dielectric would mimic a frustum very closely.
Roger Shawyer's first patent has a cone shaped dielectric -
#2986 by TheTraveller on 02 Jun, 2016 19:38
-
I never noticed that graphic for Cannae. They use an asymmetric dialectric (cone, pyramid?) inside a symmetric cavity and NASA uses a symmetric dialectric insert in an asymmetric cavity. Those are the inverse of one another geometrically.
Cal Polytech used symmetric insert with symmetric cavity, correct? Did they ever try different shapes of HDPE, like a cone?
We only had a symmetric cylindrical HDPE disc, but a cone shape was recommended to us by the microwave industry professional who lent us the antenna. He anticipated that a gradually tapered dielectric would mimic a frustum very closely.
Roger Shawyer's first patent has a cone shaped dielectric
I really fail to understand why any serious EmDrive builder is using dielectrics or non freq tunable magnetron based Rf generators with no forward and reflected power feedback?
Roger's best with dielectrics and magnetrons was 16mN at 850W Rf:
http://emdrive.com/feasibilitystudy.html
To get that result his frustum and Rf delivery system build was very complex and featured at least 3 ways to physically tune the frustum and waveguide Rf delivery system. As far as I know, no DIY EmDrive build is attempting to replicate all that Roger incorporated into his 1st Experimental EmDrive. It is not enough to take a bit from his Experimental and/or Demonstrator magnetron based builds and expect success. As far as I know Roger never used kitchen magnetrons nor their power supplies as I believe he knew of their wide frequency splatter and lack of frequency control shortcomings.
I measured 8mN at 95W Rf using no dielectric, no physical tuning, no Rf waveguide delivery system and single frequency tunable Rf excitation in TE013 mode with real time forward and reflected power outputs from the 100W Rf amp.
But go your hardest guys, who knows you may get lucky and get a lot of dynamic variables to all hit the force generation sweet spot at the same time. -
#2987 by Monomorphic on 02 Jun, 2016 19:45
-
I reworked my setup so that I can capture RF trace as well as the movement of the laser. This reduced the size of the monitor station... which was much appreciated by my better half.
Removed the ruler and went with a grid instead. It's much easier to calibrate this setup as all I have to do is hit anywhere in the middle of the grid.
-
#2988 by Rodal on 02 Jun, 2016 19:45
-
I never noticed that graphic for Cannae. They use an asymmetric dialectric (cone, pyramid?) inside a symmetric cavity and NASA uses a symmetric dialectric insert in an asymmetric cavity. Those are the inverse of one another geometrically.
Cal Polytech used symmetric insert with symmetric cavity, correct? Did they ever try different shapes of HDPE, like a cone?
We only had a symmetric cylindrical HDPE disc, but a cone shape was recommended to us by the microwave industry professional who lent us the antenna. He anticipated that a gradually tapered dielectric would mimic a frustum very closely.
Roger Shawyer's first patent has a cone shaped dielectric
I really fail to understand why any serious EmDrive builder is using dielectrics or non freq tunable magnetron based Rf generators with no forward and reflected power feedback?
Roger's best with dielectrics and magnetrons was 16mN at 850W Rf:
http://emdrive.com/feasibilitystudy.html
To get that result his frustum and Rf delivery system build was very complex and featured at least 3 ways to physically tune the frustum and waveguide Rf delivery system.
I measured 8mN at 95W Rf using no dielectric, no physical tuning, no Rf waveguide delivery system and single frequency tunable Rf excitation in TE013 mode with real time forward and reflected power outputs from the 100W Rf amp.
But go your hardest guys, who knows you may get lucky and get a lot of dynamic variables to all hit the force generation sweet spot at the same time.
Because Shawyer used inorganic dielectrics with relative permittivity =38 instead of the materials being discussed.
To understand why anisotropic polymers like PTFE and HDPE, with a relativite permittivity (~2) closer to vacuum and air (~1) than the relative permittivity of the inorganic polymers used by Shawyer (~38) may make a difference, it is helpful to have a background and engineering experience in Materials Science to appreciate that what is at stake here is not the dielectric properties but what matters is electrostriction. Also helpful is a background in General Relativity to understand Woodward's Mach effect theory would help in understanding what is at stake.
It would be hopeless to try to understand the effect of HDPE and PTFE on the basis of relative permittivity, without taking into account Woodward's Mach effect theory, so I understand your failure to understand this, it makes sense: these materials purpose is NOT to serve as a simple dielectric based on permittivity.
Suggestion: to understand this, read Woodward Mach Effect papers. -
#2989 by TheTraveller on 02 Jun, 2016 19:49
-
Because Shawyer used inorganic dielectrics with relative permittivity =38 instead of the materials being discussed.
To understand why anisotropic polymers like PTFE and HDPE, with a relativite permittivity (~2) closer to vacuum and air (~1) than the relative permittivity of the inorganic polymers used by Shawyer (~38) make a difference, one has to have an academic background and engineering experience in Materials Science to tell that what is at stake here is not the dielectric properties but what matters is electrostriction. Also academic background in General Relativity to understand Woodward's Mach effect theory would help in understanding what is at stake.
That is your theory based on no physical experimental data. So why share it to real world EmDrive builders as it may not be correct and may mislead them to obtain null results? -
#2990 by Rodal on 02 Jun, 2016 19:51
-
No, it is not my theory, it is Woodward's theory. Please read NASA's reports: Dr. White's, Paul March, Brady et.al., Star-Drive's comments and read Prof. Woodward's papers.Because Shawyer used inorganic dielectrics with relative permittivity =38 instead of the materials being discussed.
To understand why anisotropic polymers like PTFE and HDPE, with a relativite permittivity (~2) closer to vacuum and air (~1) than the relative permittivity of the inorganic polymers used by Shawyer (~38) make a difference, one has to have an academic background and engineering experience in Materials Science to tell that what is at stake here is not the dielectric properties but what matters is electrostriction. Also academic background in General Relativity to understand Woodward's Mach effect theory would help in understanding what is at stake.
That is your theory based on no physical experimental data. So why share it to real world EmDrive builders as it may not be correct and may mislead them to obtain null results?
Also please see these:
1) Hackaday Aachen Germany team achieved best results by using a polymer insert
2) Cannae copper cavities required a polymer insert. -
#2991 by Carl G on 02 Jun, 2016 20:18
-
The forums rules clearly state that a basic level of civility is required here. Breach that rule and you will lose your post. If you breach it continuously you will be sent to the naughty step until you calm down.
-
#2992 by tchernik on 02 Jun, 2016 21:08
-
That is your theory based on no physical experimental data. So why share it to real world EmDrive builders as it may not be correct and may mislead them to obtain null results?
AFAIK the dielectric inserts aren't fixed to the frustum, therefore the DIYers can test their builds with and without them. Nobody is misleading anyone else into nullifying their results.
This is just one more variable to explore in a laundry list of variables mentioned here before. -
#2993 by mwvp on 02 Jun, 2016 21:47
-
Ok, after some reconsideration, I can see how I may be rigorously mistaken in asserting that an EM Drive perhaps is, because of my off-the-cuff fuzzy notions. Rather than thrust (force), lets say transfer efficiency; how much a rocket may increase its velocity for a given amount of energy:
...But, for the interaction with the sun fields, sun plasma, sun photons, a closed and small cavity does not make a big sense. Additionnaly, all the tests were conducted on earth, with earth magnetic field, and not exposed to the interplanetary fields. So, if the emdrive was working with these fields, all the tests that were conducted would be irrelevant. In fact, all the conducted tests are rather supposing a negligeable interaction with external fields. If the aim was of maximizing the interaction with external fields, the device would be completely different.
I don't assert interactions, other than with the vacuum in the frustrum, and the radiation of heat, are necessary or happening.
The idea of the photonic thruster described is that the same photons are used several times, but it works only because there is the mother platform to push against. This is also why the efficiency ratio compared to a photon rocket is decreasing when the speed of the mission spacecraft relatively to the mother platform is increasing.
The energy conservation principle makes that the energy lost by the redshifting photons is gained by the mission spacecraft, in the form of Kinetic Energy relatively to the mother platform. The total momentum of the system composed of the mother platform and the mission spacecraft is not changed. Except when some photons (or waste heat) are lost in space
The emdrive has no mothership to push against, it can not work with the same principle that the Photonic laser thruster
No not exactly. Consider a cavity containing radiation at frequency F. The forces at each end of the cylinder for reflecting boundaries are 2 x (twice) the incident energy. Imagine one end is coated with a magic material that absorbs Doppler down-shifted radiation at frequency F - [cavity acceleration]. The end that absorbs radiation, dissipating it as heat, only experiences 1 x incident energy as radiation pressure force.
Consequently, one need only kick the can, nudge it a bit, for the can to begin converting electromagnetic energy into kinetic energy and heat.
It is my understanding that a conical frustrum is anisotropic with respect to dispersion and dissipation. Moreover this is similar to what occurs in photonic cooling and optomechanical oscillation.
How much? How useful is it? Surely any analysis and theory must take into account enhanced thermal dissipation of energy and momentum, especially as a result of Doppler spreading induced by acceleration.
Cavity optomechanics
http://arxiv.org/abs/1303.0733
-
#2994 by mwvp on 02 Jun, 2016 22:05
-
...
1) the electromagnetic pressure is way too small and the GHz frequency too high to envision significant mechanical vibrations of the EM Drive walls. Shawyer claims a maximum of less than 200 milliNewtons, many NASA experiments, particularly in vacuum, and also by Tajmar are in the microNewton range. One can readily show that the mechanical vibrations produced by such forces are of extremely small magnitude. Besides that, the frequency of oscillation of the microwaves is several orders of magnitude higher than typical mechanical vibrations. Therefore the mode shapes would be extremely high and therefore the video is unrepresentative of these extremely tiny vibrations (they would not be flexural vibrations as shown in the video but extremely small motions)
Optical radiation pressure can induce megahertz frequency mechanical oscillations. Or can cool and damp them. See:
http://arxiv.org/abs/1303.0733
The magnetron has a number of resonators. Yang's configuration has a tuned coupling waveguide section. If the frequency seperation of the frustrum and the coupling network and/or magnetron is near a peak on a favorable slope for an acoustic instability, the frustrum (IMHO) just might start singing. But I really doubt it would be for long, considering the disparity of frequencies and sensitivity of the cavity to heat.
Nevertheless, if heat or vibration cause doppler reflected energy that enhances radiation pressure, further heat/pressure will affect the frustrum, and could sustain a resonance.
-
#2995 by Monomorphic on 02 Jun, 2016 22:08
-
Plot of the laser during my ~6 minute unpowered test a few days ago. The HVAC was running during this test. I hope there is a way I can relabel the axis here with pixels = cm and T = seconds. Also including the raw data.
Will do another one of these tests without the HVAC running tonight.
-
#2996 by Rodal on 02 Jun, 2016 22:14
-
The first thing to realize is that the governing equations for optical cavities you are linking to are fundamentally different (and so are the mode shapes) than the governing equations for TE and TM modes in microwave cavities....
1) the electromagnetic pressure is way too small and the GHz frequency too high to envision significant mechanical vibrations of the EM Drive walls. Shawyer claims a maximum of less than 200 milliNewtons, many NASA experiments, particularly in vacuum, and also by Tajmar are in the microNewton range. One can readily show that the mechanical vibrations produced by such forces are of extremely small magnitude. Besides that, the frequency of oscillation of the microwaves is several orders of magnitude higher than typical mechanical vibrations. Therefore the mode shapes would be extremely high and therefore the video is unrepresentative of these extremely tiny vibrations (they would not be flexural vibrations as shown in the video but extremely small motions)
Optical radiation pressure can induce megahertz frequency mechanical oscillations. Or can cool and damp them. See:
http://arxiv.org/abs/1303.0733
The magnetron has a number of resonators. Yang's configuration has a tuned coupling waveguide section. If the frequency seperation of the frustrum and the coupling network and/or magnetron is near a peak on a favorable slope for an acoustic instability, the frustrum (IMHO) just might start singing. But I really doubt it would be for long, considering the disparity of frequencies and sensitivity of the cavity to heat.
Nevertheless, if heat or vibration cause doppler reflected energy that enhances radiation pressure, further heat/pressure will affect the frustrum, and could sustain a resonance.
Please consider the electromagnetic pressure that can be generated with a laser, vs the one for microwave radiation at 2.45 GHz. A microwave cavity is not an optical cavity.
Somebody (not you) was mixing them up some time ago and even went as far as proposing to do away with the side conical walls in a microwave cavity. That would not work (because there is pressure on the conical walls of a microwave cavity). Optical "cavities" on the other hand do not need side walls.
Also, take a look at the conservation of energy and conservation of momentum equations for a microwave resonant cavity.
But the main point is that fundamentally, none of this can result in force/inputPower exceeding the one of a perfectly collimated photon rocket. -
#2997 by Monomorphic on 02 Jun, 2016 22:34
-
But the main point is that fundamentally, none of this can result in force/inputPower exceeding the one of a perfectly collimated photon rocket.
Dr. Rodal, the photonic laser thruster exceeds the force/input power of a photon rocket up to a certain velocity - when the two intersect. If the emrive recycles photons in a similar way, then couldn't it also have a force/input power exceeding a photon rocket up to a certain velocity?
-
#2998 by Rodal on 02 Jun, 2016 22:36
-
These are all interesting concepts, but these issues have to be addressed, for us to make progress in understanding this:But the main point is that fundamentally, none of this can result in force/inputPower exceeding the one of a perfectly collimated photon rocket.
Dr. Rodal, the photonic laser thruster exceeds the force/input power of a photon rocket up to a certain velocity - when the two intersect. If the emrive recycles photons in a similar way, then couldn't it also have a force/input power exceeding a photon rocket up to a certain velocity?
1) A photonic laser thruster only works by having a supply vehicle move in the opposite direction. There is no separate supply vehicle in the EM Drive
2) how does one recycle photons and exceed a photon rocket force/Input power in a microwave cavity? -
#2999 by Monomorphic on 02 Jun, 2016 22:40
-
2) how does one recycle photons and exceed a photon rocket force/Input power in a microwave cavity?
By using a frustum of course!
