-
#2660 by mwvp on 06 Feb, 2016 10:38
-
Must-see viewing for Meep'ers...
Not much posts here today. Time to look a bit of Leonard Susskind's Lectures on youtube to learn and refresh some of the basics
Thanks, great links, I've seen a couple of Susskind's lectures. I'll try the GR lectures soon, having given up on Kip, Thorne & Wheeler after ~ chapter 3 many years back. I'm doing the UTEP ee5303 FDTD class, using Octave (Matlab clone) to DIY FDTD code at the atomic-level. It's giving me insights into why Meep is the way it is, and a much better grasp of what can be done with simulations, and how to use the tools.
I'm about half way through it, having spent ~ 15 hours so far. I very much recommend it for anyone really serious about simulating. Otherwise there's facile, feckless FEKO for quck & dirty deeds
https://www.youtube.com/channel/UCPC6uCfBVSK71MnPPcp8AGA
http://emlab.utep.edu/ee5390fdtd.htm
BTW, I've gotten a couple emails lately that Comsol is in town (around Chicago) to present seminars on chemical and high/low frequency analysis, a two-week trial version of Comsol, and of course, free lunch. Comsol does seminars around major cities in US/Europe every few months it seems, probably around three a year for the last couple years here. They have videos and tutorials for EM cavities too.
I ran through the Comsol demos, but lacking knowledge and experience, I can't say having a powerful tool makes you better off. After ten classes of EE5303 and writing some Matlab code, I understand a lot more about how to use the tools effectively, their capacity and limitations.
-
#2661 by flux_capacitor on 06 Feb, 2016 11:58
-
{snip}
Hello,
For a uniform E field, the velocity of the ExB drift (a special case of guiding center drift) is constant.
See:
https://en.wikipedia.org/wiki/Guiding_center#Electric_field
or
http://people.duke.edu/~ad159/files/p142/4.pdf
for more.
Best
Thank you for your input, and welcome to the forum
You forgot to mention the Lorentz force, which acts upon charged particles, within areas where constant (or non-constant) E×B fields are applied via an electromagnetic coil (or a magnet) and two electrodes where a voltage is applied.
The equation of motion of a free particle of charge q and mass m moving in uniform electric and magnetic fields is:
m a = q E + q v × B
Where a is the particle's acceleration. This is known since 1897 thanks to physicist Joseph John Thomson who made the first precise measurement of charged particle's acceleration in uniform E×B fields at Cambridge University's Cavendish Laboratory.
An applied Lorentz force is a body force and it does accelerate charged particles. Even in areas where the E-field is constant. Electrons and ions in a plasma can't have a constant velocity when a Lorentz force is applied upon them, due to the work done by the fields. In uniform B and E fields, it is the acceleration of the charged particle which is constant.
See:
http://en.wikipedia.org/wiki/Lorentz_force for the basics
and better, the book Fundamentals of Plasma Physics, Springer 2004 (Chapter 2: Charged Particle Motion in Constant and Uniform Electromagnetic Fields, pp. 33-58) -
#2662 by rfmwguy on 06 Feb, 2016 13:23
-
#2663 by CW on 06 Feb, 2016 13:23
-
{snip}
Hello,
For a uniform E field, the velocity of the ExB drift (a special case of guiding center drift) is constant.
See:
https://en.wikipedia.org/wiki/Guiding_center#Electric_field
or
http://people.duke.edu/~ad159/files/p142/4.pdf
for more.
Best
Thank you for your input, and welcome to the forum
You forgot to mention the Lorentz force, which acts upon charged particles, within areas where constant (or non-constant) E×B fields are applied via an electromagnetic coil (or a magnet) and two electrodes where a voltage is applied.
The equation of motion of a free particle of charge q and mass m moving in uniform electric and magnetic fields is:
m a = q E + q v × B
Where a is the particle's acceleration. This is known since 1897 thanks to physicist Joseph John Thomson who made the first precise measurement of charged particle's acceleration in uniform E×B fields at Cambridge University's Cavendish Laboratory.
An applied Lorentz force is a body force and it does accelerate charged particles. Even in areas where the E-field is constant. Electrons and ions in a plasma can't have a constant velocity when a Lorentz force is applied upon them, due to the work done by the fields. In uniform B and E fields, it is the acceleration of the charged particle which is constant.
See:
http://en.wikipedia.org/wiki/Lorentz_force for the basics
and better, the book Fundamentals of Plasma Physics, Springer 2004 (Chapter 2: Charged Particle Motion in Constant and Uniform Electromagnetic Fields, pp. 33-58)
AFAIK, a static uniform B-field does not transfer energy to a charged particle, but only changes the direction of its velocity vector. In a configuration of static, crossed E and B field, isn't it just the E field component that can (at all) add to a charged particle's kinetic energy? -
#2664 by rfmwguy on 06 Feb, 2016 13:44
-
Another Special Announcement - Please keep our EMDrive friend Phil Wilson, The Traveller in your thoughts. He is back in the hospital as of today. Get well soon, Phil - Your NSF friends.
-
#2665 by Notsosureofit on 06 Feb, 2016 13:51
-
Just for fun:
Let's suppose that a photon is able to transfer all of its energy to a "dark" particle of mass 20,000 times that of the equivalent mass of the photon such that it's new kinetic energy results in a speed of 0.01c. Then the momentum exchange is 200 times that of a photon rocket.
As I said, just for fun.
Probably too much snow and too much chocolate, but I decided to calculate said "dark" particle (or at least its minimum mass) using the 500 microN maximum static force at Q=2000, P=1 kW, f=1.7 GHz from the notsosureofit hypothesis chart in the Emdrive Wiki. This is ~170 times the photon rocket force.
For a single photon interaction, the result is a mass greater than 1.6 x 10^-37 kg or 8.1 x 10^6 Gev. Pretty hefty ! But it is one way to satisfy classical COE and COM. Don't forget this is the static force.
Edit: Just thinking that there is no reason not to have "dark" particles up to the plank mass ~2.2 x 10^-8 kg, so there is plenty of room to play here.
Would the particle still be around when we switch the power off?
If it is not stable does it have a unique decay patten?
This really doesn't say anything about the characteristics of the particle per se. It is just an exercise to see what the implication of COE and COM requires in this model.
Now that being said, should the emdrive be demonstrated with repeatable measurements, you could view it as an instrument to measure the minimum energy density of the vacuum. For instance, in this particular calculation at 1000W, the required minimum energy density is ~ 2 x 10^-10 joules/m^3. That's just below the cosmological value ~ 10^-9 but far, far from the quantum value of 10^113.
Since the required minimum experimental value of the vacuum energy density depends on the power input to the device, a working emdrive can require a minumum energy density for the vacuum OR an upper limit on the obtainable static force from the emdrive.
Notice that these implications are drawn only for this rather simple model. -
#2666 by flux_capacitor on 06 Feb, 2016 13:59
-
AFAIK, a static uniform B-field does not transfer energy to a charged particle, but only changes the direction of its velocity vector. In a configuration of static, crossed E and B field, isn't it just the E field component that can (at all) add to a charged particle's kinetic energy?
Precisely! The ambient B-field does not add kinetic energy to charged particles, it only bend their trajectory; their velocity vector stays the same. However, the ambient applied E-field (applied from electrodes' voltage) does accelerate the particles. The "trick" in an MHD accelerator is the combination of applied E and B fields, which accelerate both species -negative electrons and positive ions- towards the same direction, instead of separating them as in an MHD generator.
Credits: For a Fistful of Amperes © JP Petit 1989 (now freely downloadable and attached below).
-
#2667 by Rodal on 06 Feb, 2016 14:15
-
Just for fun:
Let's suppose that a photon is able to transfer all of its energy to a "dark" particle of mass 20,000 times that of the equivalent mass of the photon such that it's new kinetic energy results in a speed of 0.01c. Then the momentum exchange is 200 times that of a photon rocket.
As I said, just for fun.
Probably too much snow and too much chocolate, but I decided to calculate said "dark" particle (or at least its minimum mass) using the 500 microN maximum static force at Q=2000, P=1 kW, f=1.7 GHz from the notsosureofit hypothesis chart in the Emdrive Wiki. This is ~170 times the photon rocket force.
For a single photon interaction, the result is a mass greater than 1.6 x 10^-37 kg or 8.1 x 10^6 Gev. Pretty hefty ! But it is one way to satisfy classical COE and COM. Don't forget this is the static force.
Edit: Just thinking that there is no reason not to have "dark" particles up to the plank mass ~2.2 x 10^-8 kg, so there is plenty of room to play here.
Would the particle still be around when we switch the power off?
If it is not stable does it have a unique decay patten?
This really doesn't say anything about the characteristics of the particle per se. It is just an exercise to see what the implication of COE and COM requires in this model.
Now that being said, should the emdrive be demonstrated with repeatable measurements, you could view it as an instrument to measure the minimum energy density of the vacuum. For instance, in this particular calculation at 1000W, the required minimum energy density is ~ 2 x 10^-10 joules/m^3. That's just below the cosmological value ~ 10^-9 but far, far from the quantum value of 10^113.
Since the required minimum experimental value of the vacuum energy density depends on the power input to the device, a working emdrive can require a minumum energy density for the vacuum OR an upper limit on the obtainable static force from the emdrive.
Notice that these implications are drawn only for this rather simple model.
When you state << view it as an instrument to measure the minimum energy density of the vacuum>>
in which of these different senses do you use the words "measure the minimum energy density of the vacuum"?
0) The minimum experimental value of the vacuum energy density required for the photon coupling (to a dark particle with unknown characteristics) measurement (dependent on the forward power input to the EM Drive)
1) The minimum energy density value of the Quantum Vacuum within an experimental uncertainty band.
2) A minimum value of theoretical alternative vacua, below Dirac's sea: the Quantum Vacuum state completely full of negative-energy electron states and nothing else, with no holes, but above the classical vacuum state totally devoid of particles or antiparticles.
3) The minimum energy density value of a mutable, degradable Quantum Vacuum with real multiple levels of energy density as proposed by Dr. White et.al.
4) Another meaning ? -
#2668 by RotoSequence on 06 Feb, 2016 15:33
-
Another Special Announcement - Please keep our EMDrive friend Phil Wilson, The Traveller in your thoughts. He is back in the hospital as of today. Get well soon, Phil - Your NSF friends.
Take care of yourself and get better, T.T.
-
#2669 by Notsosureofit on 06 Feb, 2016 15:49
-
Just for fun:
Let's suppose that a photon is able to transfer all of its energy to a "dark" particle of mass 20,000 times that of the equivalent mass of the photon such that it's new kinetic energy results in a speed of 0.01c. Then the momentum exchange is 200 times that of a photon rocket.
As I said, just for fun.
Probably too much snow and too much chocolate, but I decided to calculate said "dark" particle (or at least its minimum mass) using the 500 microN maximum static force at Q=2000, P=1 kW, f=1.7 GHz from the notsosureofit hypothesis chart in the Emdrive Wiki. This is ~170 times the photon rocket force.
For a single photon interaction, the result is a mass greater than 1.6 x 10^-37 kg or 8.1 x 10^6 Gev. Pretty hefty ! But it is one way to satisfy classical COE and COM. Don't forget this is the static force.
Edit: Just thinking that there is no reason not to have "dark" particles up to the plank mass ~2.2 x 10^-8 kg, so there is plenty of room to play here.
Would the particle still be around when we switch the power off?
If it is not stable does it have a unique decay patten?
This really doesn't say anything about the characteristics of the particle per se. It is just an exercise to see what the implication of COE and COM requires in this model.
Now that being said, should the emdrive be demonstrated with repeatable measurements, you could view it as an instrument to measure the minimum energy density of the vacuum. For instance, in this particular calculation at 1000W, the required minimum energy density is ~ 2 x 10^-10 joules/m^3. That's just below the cosmological value ~ 10^-9 but far, far from the quantum value of 10^113.
Since the required minimum experimental value of the vacuum energy density depends on the power input to the device, a working emdrive can require a minumum energy density for the vacuum OR an upper limit on the obtainable static force from the emdrive.
Notice that these implications are drawn only for this rather simple model.
When you state << view it as an instrument to measure the minimum energy density of the vacuum>>
in which of these different senses do you use the words "measure the minimum energy density of the vacuum"?
0) The minimum experimental value of the vacuum energy density required for the photon coupling (to a dark particle with unknown characteristics) measurement (dependent on the forward power input to the EM Drive)
1) The minimum energy density value of the Quantum Vacuum within an experimental uncertainty band.
2) A minimum value of theoretical alternative vacua, below Dirac's sea: the Quantum Vacuum state completely full of negative-energy electron states and nothing else, with no holes, but above the classical vacuum state totally devoid of particles or antiparticles.
3) The minimum energy density value of a mutable, degradable Quantum Vacuum with real multiple levels of energy density as proposed by Dr. White et.al.
4) Another meaning ?
Well, 0) in this train of thought.
Wavefunction calculations are exceedingly slow w/ my available time and years out of date. I have noticed that calculations involving bounded Schrodingers equations have made some progress over the years but it is still too early to tell if that has application to the analytic description of the emdrive.
Edit: If someone wanted to play w/ numbers they could calculate a "limit" from the "flattened" force curve in Yang's papers.
-
#2670 by zen-in on 06 Feb, 2016 17:42
-
Another Special Announcement - Please keep our EMDrive friend Phil Wilson, The Traveller in your thoughts. He is back in the hospital as of today. Get well soon, Phil - Your NSF friends.
Get well Phil! You have a lot of friends pulling for you. -
#2671 by Bob Woods on 06 Feb, 2016 19:17
-
Another Special Announcement - Please keep our EMDrive friend Phil Wilson, The Traveller in your thoughts. He is back in the hospital as of today. Get well soon, Phil - Your NSF friends.
Phil, best wishes and make those doctors earn their keep.
Dave, if you hear more please let us know. I'll be monitoring EMDriveResearch also. -
#2672 by n-s-k on 06 Feb, 2016 20:32
-
{snip}
Hello,
For a uniform E field, the velocity of the ExB drift (a special case of guiding center drift) is constant.
See:
https://en.wikipedia.org/wiki/Guiding_center#Electric_field
or
http://people.duke.edu/~ad159/files/p142/4.pdf
for more.
Best
Thank you for your input, and welcome to the forum
You forgot to mention the Lorentz force, which acts upon charged particles, within areas where constant (or non-constant) E×B fields are applied via an electromagnetic coil (or a magnet) and two electrodes where a voltage is applied.
The equation of motion of a free particle of charge q and mass m moving in uniform electric and magnetic fields is:
m a = q E + q v × B
Where a is the particle's acceleration. This is known since 1897 thanks to physicist Joseph John Thomson who made the first precise measurement of charged particle's acceleration in uniform E×B fields at Cambridge University's Cavendish Laboratory.
An applied Lorentz force is a body force and it does accelerate charged particles. Even in areas where the E-field is constant. Electrons and ions in a plasma can't have a constant velocity when a Lorentz force is applied upon them, due to the work done by the fields. In uniform B and E fields, it is the acceleration of the charged particle which is constant.
See:
http://en.wikipedia.org/wiki/Lorentz_force for the basics
and better, the book Fundamentals of Plasma Physics, Springer 2004 (Chapter 2: Charged Particle Motion in Constant and Uniform Electromagnetic Fields, pp. 33-58)
Oh absolutely,
I believe we agree,
the instantaneous acceleration of the particle is not zero (or we could forget about cyclotron radiation),
but its average value over one Larmor orbit is (in the aforementioned special case of the ExB drift), as the velocity of the guiding center is constant.
Or should I go back studying Chen?
Thank you for the warm welcome,
Best -
#2673 by dustinthewind on 07 Feb, 2016 03:12
-
...
It is my understanding that Desiato (NSF user "WarpTech") arrived at a similar conclusion (the EM Drive 'falling into" by gravitation) using a different Quantum Vacuum formulation.
Also Dr. Brandenburg (a physicist with controversial science-fiction ideas, which I don't share. Paper on EM Drive attached below) arrives at the same conclusion using a similar theoretical formulation.
It is my understanding that White thinks that this negative energy density can be viewed as gravitationally negative mass through Einstein’s E=m*c^2 equivalence equation.
For this to occur the Quantum Vacuum must be mutable and degradable, at least at very close ranges on the order of subatomic processes.
It is my understanding that Dr. White proposes that this QV compressibility constant is governed by the Casimir force equation’s r^4 separation sensitivity as described in the “Dynamics of the Vacuum” paper, attached below.
-----------------------------------------------------------------
This is one of the many motivations (as well as Minotti's, Lobo's, Alcubierre, Woodward's, etc.) that drove me to formally consider and solve the relevant frame-indifferent relativistic momentum equation, to mathematically explore its consequences.
...
Thanks for sharing the Brandenburg paper. I found it interesting. Some notes as I read were,
I am thinking that space-time should really be energy-space-time where we might not have any space-time with out the energy from the big bang. Was most of the beginning energy light to begin with? It is even speculated electrons may be made of light by some. Maybe light by destructive interference converted to invisible light by destructive interference to rapidly expand space-time? Could the thermal death of the universe be expanding space time by increasing that radiation background that over time destructively interferes?
I liked the analogy of 2 dark objects in a bright background gravitationally attract. This reminded me of us being the negative energy universe where we have some base energy level but our matter is negative relative to it. Could the increasing entropy of our universe be evidence for the flow of space time out of matter? Negative energy matter being gravitationally attracted to an outflow of space time?
I was messing around with the idea of a negative well particle by making a Fourier sum of waves to get a well from 1-A*exp(-(x-d)^2/w) to get some negative well in a vacuum in a 1-D sense. Anti-matter is then some collection of waves that unravel the Fourier sum? Notice how the waves become more violent near the particle.
His illustrations of the tilted plate capacitor I thought might be confusing because it is not specified how the B field is being generated. If B exists by v x E = B then B is only the relativistic compression of the capacitor, which by v x B + E = E which gives the relativistic enhanced E field by Lorentz contraction of the capacitor. This B field disappears as soon as the charge begins traveling along the electric field lines by v x E where as the velocity is no longer perpendicular to the electric field.
On the other hand if the B' field exists because of a Helmholtz coil then when this B' field is added to the B field of the Capacitor we get v x E + B' = B + B'. A charge traveling in a Helmholtz coil B field can loop because as the velocity changes the relativistic dipole charge distribution due to current in the coil rotates with the velocity of the observing charge. This doesn't happen for the B field generated by the capacitor. I assume he is considering a Helmholtz B field because he later illustrates a charge traveling in loops?
Another thought is why not the vacuum mass be persistent, as these waves that interfere still exist and can carry momentum. They can emerge as particles from time to time as do Freak or Rogue waves in the ocean by random constructive interference.
-
#2674 by dustinthewind on 07 Feb, 2016 03:44
-
Also, could we induce a flow of space time if we have a cavity where light is added but by the shape of the cavity light is trapped inside? After adding such energy flip the polarization of light into the cavity by 180 degrees and cancel all the stored light. What happened to all the momentum? Did is just disappear or is it possible it could be transferred to the vacuum?
Another interesting question is if the wave in the cavity is a standing wave or a traveling wave. I want to think it's traveling.
Illustration sort of relates to this idea: http://forum.nasaspaceflight.com/index.php?topic=39464.0 but also to EM cavities and concepts of space-time.
Could a magnetron be so successful because it can introduce radiation that may destructively interfere with existing radiation in the cavity? Not sure how the momentum would be all in the same direction or if it really could introduce destructive interference with existing radiation.
-
#2675 by dustinthewind on 07 Feb, 2016 05:39
-
...
but its average value over one Larmor orbit is (in the aforementioned special case of the ExB drift), as the velocity of the guiding center is constant.
...
Are we talking about if the charge exits with a greater velocity than when it entered? In regards to this paper? Brandenburg GEM theory of Q thruster II (3).pdf Link: http://forum.nasaspaceflight.com/index.php?topic=39004.msg1487670#msg1487670 page 6
-
#2676 by n-s-k on 07 Feb, 2016 09:11
-
...
but its average value over one Larmor orbit is (in the aforementioned special case of the ExB drift), as the velocity of the guiding center is constant.
...
Are we talking about if the charge exits with a greater velocity than when it entered? In regards to this paper? Brandenburg GEM theory of Q thruster II (3).pdf Link: http://forum.nasaspaceflight.com/index.php?topic=39004.msg1487670#msg1487670 page 6
Thank you for the link,
I believe we are indeed talking about Fig. 5 on page 6.
It is my understanding that the left schematic "Uniform motion" is correctly representing the motion of a charged particle ExB drifting in a homogeneous field with zero net acceleration.
In the schematic on the right, or yours, as a consequence of the radial E field gradient, the particle should accelerate towards the center. -
#2677 by rfmwguy on 07 Feb, 2016 15:25
-
I've avoided twitter, but noticed #emdrive is somewhat active so I created @rfmwguy there since I've seen my moniker mentioned. That's all I need, another locale to keep me distracted
Oh well, at least I dumped reddit several months ago and can afford to replace it.
-
#2678 by Rodal on 07 Feb, 2016 15:46
-
I've avoided twitter, but noticed #emdrive is somewhat active so I created @rfmwguy there since I've seen my moniker mentioned. That's all I need, another locale to keep me distracted
Sorry, but with Twitter limiting Tweet length to 140 characters, I fail to see how #emdrive is doing any good to the controversy surrounding the EM Drive. Looking at the superficial content in
Oh well, at least I dumped reddit several months ago and can afford to replace it.
https://twitter.com/hashtag/emdrive?lang=en
this seems to be corroborated.
-
#2679 by Notsosureofit on 07 Feb, 2016 15:52
-
This forum is more than I can keep up with as it is !
