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#3020
by
deltaMass
on 10 May, 2015 18:04
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I would like advice on lifetime estimates of the power within the cavity - what is the expected half life? Does a simple expression exist involving the Q-factor? I remind that Q can be defined as the angular frequency multiplied by the ratio of (stored energy) / (rate of energy dissipation).
A simplistic analysis produces an expression for half-life that is independent of the stored energy, viz:
T(half) = Q / (2*w)with w being the angular frequency. Plugging in EW's approx Q ~= 6,000, f ~= 2.4 GHz. we get
T(half) ~= 200 nanoseconds.
This corresponds to a refresh rate of ~5 MHz.
What's the mark:space ratio? Well, this
does depend on the cavity energy we require.
Do we know the cavity energy?ETA There's method in my madness. I am working up to a "decoupled" measurement protocol.
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#3021
by
dustinthewind
on 10 May, 2015 18:04
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On the note about a vacuum test. What about a high altitude balloon launch? Quote from site:
http://www.arhab.org/"Near space is that region of the atmosphere above 60,000 feet but below the accepted altitude of space, 328,000 feet. These altitudes make near space far more like earth orbit than the surface of the earth. Air pressure in near space reaches 99% of a vacuum or better. Air temperatures drop to a low of -60 degrees F or colder. Cosmic radiation is over 100 times greater than at sea level. Near space is located within the ozone layer and therefore is an environment of increased damaging ultraviolet radiation. Near space is reached by helium or hydrogen-filled weather balloons. Since it is far less expensive to send payloads into near space than earth orbit, organizations like NASA will send new designs into near space first, as a test."
I guess the question is at what altitude do wind turbulence become a non-factor. Maybe it is possible to even measure that and then subtract it from measurements inside a container on the balloon.
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#3022
by
deltaMass
on 10 May, 2015 18:10
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I believe there's some meat on that bone. The idea here is to fly two geometrically identical test articles of equal mass close together, and only power one of them using wireless commands. Then the metric of interest is their difference. This helps to get rid of a lot of the guff you mentioned.
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#3023
by
Mulletron
on 10 May, 2015 18:14
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Continuing with the "Test In Space" theme.
We lack cheap space access for unmanned cargo. We have no railgun running from the coast of Ecuador up into the Andes to the east, and we have no Skylon/SABRE SSTO yet. So we must pay many thousands of dollars per launched kilogram rather than what could be only tens of dollars.
What we do have is Cubesat and SpaceX. The problem is that the devices under consideration here won't fit even into the largest Cubesat. So let's talk miniaturisation.
What we have is photons in an asymmetric cavity. So let's use light instead of microwaves. I'll stop there for now.
I like where you're going with this...........and I want to talk miniaturization too. @Notsosureofit is working with 10ghz gunn diodes so he might be able to help.
These might be able to be put to use. These (scroll down to pic) are common in schools and easy to get:
http://demoweb.physics.ucla.edu/content/experiment-2-microwave-opticsJudging from reading (and really reading) the latest tweets from @ElonMusk, I feel that one of these Emdrive tests will find a ride on a rocket real soon.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1368379#msg1368379Note there is also a (very much new)
favorable Io9 article released on April 30th,
(A day after this:
http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/)
that wasn't linked to in the tweet. What was linked to was an old negative article from August last year.
****
http://www.pasco.com/prodCatalog/WA/WA-9314_microwave-optics-basic-system/
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#3024
by
dustinthewind
on 10 May, 2015 18:30
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Continuing with the "Test In Space" theme.
We lack cheap space access for unmanned cargo. We have no railgun running from the coast of Ecuador up into the Andes to the east, and we have no Skylon/SABRE SSTO yet. So we must pay many thousands of dollars per launched kilogram rather than what could be only tens of dollars.
What we do have is Cubesat and SpaceX. The problem is that the devices under consideration here won't fit even into the largest Cubesat. So let's talk miniaturisation.
What we have is photons in an asymmetric cavity. So let's use light instead of microwaves. I'll stop there for now.
I like where you're going with this...........and I want to talk miniaturization too. @Notsosureofit is working with 10ghz gunn diodes so he might be able to help.
Judging from reading (and really reading) the latest tweets from @ElonMusk, I feel that one of these Emdrive tests will find a ride on a rocket real soon.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1368379#msg1368379
Note there is also a (very much new) favorable Io9 article released on April 30th,
(A day after this: http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/)
that wasn't linked to in the tweet. What was linked to was an old negative article from August last year.
Interesting idea. If for instance we went from 1cm wavelength to infrared at 100um then that would be a factor of 100 in wavelength. A 1m object would then be 1cm in length? Maybe we could use glass which reflects infrared? Not too familiar with injecting infrared signals.
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#3025
by
jmossman
on 10 May, 2015 18:39
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I know that the frustum design that I currently have was originally driven by a high power (and dangerous to most people) magnetron. The frequency range of your average microwave oven magnetron and wifi are the same. I verified the frustum will resonate within this frequency range using a spectrum analyzer and a SNA. Mine works on wifi channel 1 and 10. Given that Eagleworks was able to observe thrust with only 2.6 watts for one of their tests*, I think this is an acceptable risk to take. Besides, it is just money right? So I am literally driving the frustum with the RF from the wifi camera (used to observe and is riding on the experiment) and a 2watt amp. I can scale this up to 20 watts using other amps if needed. Amps are cheap and plug and play.
* http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
I think the frequency hopping aspect of the waveform might end up doing me in though.
So this is a gamble. I'm accepting the risk of not getting a successful replication attempt in hopes that if I do, I will have built a ready-made solution for mister tinkerer to easily observe anomalous thrust at home.
If all that fails, I'll just shove in a magnetron.
If one were willing to deal with a USB cable originating from off of the balance beam, another possibility might be to try one of the cheap USB programmable generators identified by @TheTraveller (IIRC)... but you might need to brush up on your Mandarin.
http://www.ebay.com/itm/NEW-138MHz-4-4GHz-USB-SMA-Source-Signal-Generator-Simple-Spectrum-Analyzer-/171776507875?pt=LH_DefaultDomain_0&hash=item27fead7fe3Probably too much to hope for that the generator could merely be connected to an external USB hub, "configured" via a laptop, and then have the external USB hub disconnected from the laptop.... Perhaps turning the amp output on/off (remotely?) would then provide the necessary experimental control?
Wireless USB extenders do exist, but based on my quick read of their reviews, most device USB drivers don't seem to work correctly when tunneled through a "wireless extender"...
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#3026
by
deltaMass
on 10 May, 2015 18:43
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The takeaway is that the entire system - battery, laser and cavity - could easily fit into the palm of your hand. The hard part is the cavity. Let's look at that a little bit.
If you make your cavity of dimensions a large number of wavelengths, then what you end up with is a very frequency-selective (i.e. narrow-band) system. The higher the multiple, the smaller the bandwidth. So it's a good idea to stay with one or two lambda at most, and also because that's what the replication experiments are doing.
But that requires a very precise dimensioning of the cavity geometry. We are talking nanometre accuracy and therefore nano-assembly techniques. Although I possess most of Drexler's books and follow the nano field as a casual observer, I am no expert. Over to you guys.
p.s. Re. Gunn diodes - way back in 1967 I was up at 18 GHz with one, while at Marconi Space & Defense, Stanmore.
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#3027
by
StrongGR
on 10 May, 2015 19:00
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Not a single thing I built defied the laws of physics or the formulas of the trade. . . Maxwell, Ohms law, etc. If something didn't work for some weird reason, it still followed the basic laws and formulas when it ended up.
It doesn't really matter to me what is happening inside of the EM Chamber it must follow the principals of physics and conservation of energy and momentum is one of them. If I have a Air Tank pressurized with 200psi of air and a audio speaker inside that can blast at 100 watts any frequency range no matter what mixture of sound or what mixture of harmonics I crank, the tank will not move, but put a hole in one end and stand back. The second law of thermodynamics states that the entropy of an isolated system never decreases and the EM Chamber is an isolated enclosed system, we think. If we are getting thrust that, thrust must be acting outside the chamber in some form. This is why I asked the simple question if smoke was used in the tests, it wasn't to detect thermal air currents but to see if it was moving away from any thrust from the EM Chamber. Smoke is small .5 to 2 um and might be be directly effected. If not then look for other forms of accelerated energy, providing thrust emanating out of the EM Chamber.
I too would like to see a smoke test. I can't see conservation of momentum being violated. It just goes against everything we know both empirically and theoretically. I think that even in the off chance that the EmDrive is not experimental error, conservation of momentum will still hold albeit in a more subtle manner than the classical analysis would expect.
You gave the illustrative example of a closed container with different traveling and standing waves of different frequencies and amplitudes bouncing around inside. There is a very neat quantum mechanical reason that such a container is not truly closed. Even in an infinite potential well, the wave function can extend outside the walls of the well, leading to effects such as tunneling. Another great example of the wavefunction extending beyond barriers that appears to be somewhat related to the possible effect seen here is the Aharanov Bohm effect: http://en.wikipedia.org/wiki/Aharonov%E2%80%93Bohm_effect. This is due to the wavefunction of a particle outside of a container extending past the barrier of the container and interacting with the EM field on the inside of the container.
Now I leave this paper to ruminate upon:
http://arxiv.org/abs/0708.0681
Perhaps the EmDrive is acting as an evanescent mode photon rocket where momentum is carried away outside the cavity via this mechanism.
I agree with your point. No violation of momentum whatsoever and we are left, if the effect should be confirmed, with some kind of violation of cherished laws of physics. Not so exciting due also to the particular article in play completely understandable by ordinary physics.
As I will post in a few days, general relativity cannot come to rescue in this case. I would like to evaluate the presence of a hypothetical source of energy-momentum from scalar fields that, since sixties, are ubiquitous in physics. No much to be excited so far except for White's interference experiments that could open up some new avenues in experimental general relativity in a lab.
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#3028
by
apoc2021
on 10 May, 2015 19:24
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The reason for the confusion over the violation of classical physics is because this system has nothing to do with classical physics. Moreover, the “thrust” that is being calculated is not thrust at all but space moving the drive from one position to another which can merely be related to thrust but is not, per se, thrust. The controlling factor here is, of course, the resonant frequency. If you match the resonant frequency that space uses to “hold” the object you will develop a “cavity” that the “object will move towards”. The reason why the device cannot be “pushed off of” for conservation of momentum to hold true is because space is already pushing on it satisfying the law.
A couple of postulates to keep in mind that will help with these experiments are:
1. Space creates light.
2. Space itself is a resonating chamber.
Interesting! Would you then be prepared to write down the equations of motion so that we can play with them?
The equations of motion do not exist from an inertial reference frame. We must assume that the object is not moving and that space is moving around and through the object. I am trying to develop the Hamiltonian for space but having difficulty because we have always assumed space to be a virtual plasma and it is not virtual at all, but real.
Bumping this because of its elegance.
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#3029
by
tchernik
on 10 May, 2015 19:42
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The reason for the confusion over the violation of classical physics is because this system has nothing to do with classical physics. Moreover, the “thrust” that is being calculated is not thrust at all but space moving the drive from one position to another which can merely be related to thrust but is not, per se, thrust. The controlling factor here is, of course, the resonant frequency. If you match the resonant frequency that space uses to “hold” the object you will develop a “cavity” that the “object will move towards”. The reason why the device cannot be “pushed off of” for conservation of momentum to hold true is because space is already pushing on it satisfying the law.
A couple of postulates to keep in mind that will help with these experiments are:
1. Space creates light.
2. Space itself is a resonating chamber.
Interesting! Would you then be prepared to write down the equations of motion so that we can play with them?
The equations of motion do not exist from an inertial reference frame. We must assume that the object is not moving and that space is moving around and through the object. I am trying to develop the Hamiltonian for space but having difficulty because we have always assumed space to be a virtual plasma and it is not virtual at all, but real.
Bumping this because of its elegance.
I guess we will know if this is true relatively soon, if EW's interferometer experiments confirm there is a space warp field associated with the microwave resonating cavities, especially those that do provide "thrust".
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#3030
by
deltaMass
on 10 May, 2015 19:50
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I'm asking about the energy in the cavity (for reasons that may be clearer later). Here's a really dumb way to calculate it. This is so ugly, I hope someone shoots it down. It goes like this:
We know the input power, so it remains only to estimate the time to "fill" the cavity. We can think of the Q factor as the number of bounces inside the cavity (!). Taking Q=6,000 and L = 0.25 m, we get t = 5 us.
Thus for an input power of 50 W, the cavity energy is 2.5*10-4 Joules.
Pretty bad hunh?
Another way to calculate it is to take the cavity volume and the average E-field from the simulation, and then the cavity energy is 0.5*epsilon0*E2*V Joules.
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#3031
by
TheTraveller
on 10 May, 2015 20:02
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I'm asking about the energy in the cavity (for reasons that may be clearer later). Here's a really dumb way to calculate it. This is so ugly, I hope someone shoots it down. It goes like this:
We know the input power, so it remains only to estimate the time to "fill" the cavity. We can think of the Q factor as the number of bounces inside the cavity (!). Taking Q=6,000 and L = 0.25 m, we get t = 5 us.
Thus for an input power of 50 W, the cavity energy is 2.5*10-4 Joules.
Pretty bad hunh?
Another way to calculate it is to take the cavity volume and the average E-field from the simulation, and then the cavity energy is 0.5*epsilon0*E2*V Joules.
Resonate circuit has a time constant. 5 time constants to fill.
TC = Q / (2 Pi Fr).
Shawyer did comment on this and gave example.
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#3032
by
deltaMass
on 10 May, 2015 20:09
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I'm asking about the energy in the cavity (for reasons that may be clearer later). Here's a really dumb way to calculate it. This is so ugly, I hope someone shoots it down. It goes like this:
We know the input power, so it remains only to estimate the time to "fill" the cavity. We can think of the Q factor as the number of bounces inside the cavity (!). Taking Q=6,000 and L = 0.25 m, we get t = 5 us.
Thus for an input power of 50 W, the cavity energy is 2.5*10-4 Joules.
Pretty bad hunh?
Another way to calculate it is to take the cavity volume and the average E-field from the simulation, and then the cavity energy is 0.5*epsilon0*E2*V Joules.
Resonate circuit has a time constant. 5 time constants to fill.
TC = Q / (2 Pi Fr).
Shawyer did comment on this and gave example.
t(fill) = 5*Q/w then. With (Q=6000, f = 2.4 GHz) ,
t(fill) = 2 us.Boy I was close. Go figger.
So we now know the cavity energy is about
10-4 Joules.Right?
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#3033
by
deltaMass
on 10 May, 2015 20:16
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So about 0,2 us to empty to half full and then about 1 us to fill up again. Somehow these should be equal, so let's say around a 1 MHz refresh rate to half-empty and refill.
So if we make measurements at times for which the power input is disconnected, we have discovered something new about the system, have we not?
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#3034
by
WarpTech
on 10 May, 2015 20:27
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@ RODAL
Just got a minute but from your p expression;
If L1/c1 = L2/c2
del f = (1/2*f)*((c1*c2)/(L1*L2))*b^2*((1/dD1^2)-(1/dD2^2))
might be a solution ??
Got to check the thinking later.
Night !
I find your previous expression
del f = ( f/(2*c^2)) * (c1^2-c2^2)
more physically appealing, since it goes to zero for equal dielectric constants, regardless or their dielectric length,
while on the other hand
del f = (1/2*f)*((c1*c2)/(L1*L2))*b^2*((1/dD1^2)-(1/dD2^2))
goes to zero for equal dielectric lengths, regardless of their dielectric constants.
The previous expression is only valid approximation for a "uniformly varying dielectric". There is no L1 and L2 in that case.
What do you think might maximize the second expression ? (valid only for L1/c1 = L2/c2 )
I was discussing this last night and we made some interesting observations. In a variable dielectric, like in the frustum, when the waves are accelerating to a higher group velocity, they are losing momentum. This momentum is lost to the material "in the direction of the wave". It is similar to frame dragging. The wave is losing energy trying to drag the waveguide or the dielectric with it.
After the wave is reflected, it again tries to drag the dielectric or frustum with it, and this time it meets more resistance. It becomes an evanescent wave and decays faster.
I do not believe a small end cap is needed and the frustum should taper all the way down to the wave guide feeding it. The reflected waves cannot reach the small plate. That's what the thermal images show as well. Most of the energy I think should be trapped at the big end.
Todd D.
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#3035
by
WarpTech
on 10 May, 2015 20:36
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The reason for the confusion over the violation of classical physics is because this system has nothing to do with classical physics. Moreover, the “thrust” that is being calculated is not thrust at all but space moving the drive from one position to another which can merely be related to thrust but is not, per se, thrust. The controlling factor here is, of course, the resonant frequency. If you match the resonant frequency that space uses to “hold” the object you will develop a “cavity” that the “object will move towards”. The reason why the device cannot be “pushed off of” for conservation of momentum to hold true is because space is already pushing on it satisfying the law.
A couple of postulates to keep in mind that will help with these experiments are:
1. Space creates light.
2. Space itself is a resonating chamber.
Interesting! Would you then be prepared to write down the equations of motion so that we can play with them?
The equations of motion do not exist from an inertial reference frame. We must assume that the object is not moving and that space is moving around and through the object. I am trying to develop the Hamiltonian for space but having difficulty because we have always assumed space to be a virtual plasma and it is not virtual at all, but real.
Bumping this because of its elegance.
See the equations of motion for the Refractive Index, K.
https://www.dropbox.com/s/m3ztc8e5tv921z1/PV%20Approach.pdf?dl=0Todd
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#3036
by
Flyby
on 10 May, 2015 20:44
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Continuing with the "Test In Space" theme.
We lack cheap space access for unmanned cargo. We have no railgun running from the coast of Ecuador up into the Andes to the east, and we have no Skylon/SABRE SSTO yet. So we must pay many thousands of dollars per launched kilogram rather than what could be only tens of dollars.
What we do have is Cubesat and SpaceX. The problem is that the devices under consideration here won't fit even into the largest Cubesat. So let's talk miniaturisation.
What we have is photons in an asymmetric cavity. So let's use light instead of microwaves. I'll stop there for now.
The bitter irony is that we need expensive space access to (hopefully) validate a device that will gives us cheap space access...
Although I think the EMdrive needs either to gain more credibility first (or fail completely) before thinking of sending a test sample in orbit...
There is a lot more to do and test here on earth first, no?
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#3037
by
deltaMass
on 10 May, 2015 20:48
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Sure, but I'm just pointing out what the lack of cheap and readily available space access costs us in terms of either proving or disproving new propulsion theories. It would have saved Woodward 20 years of mucking about, for instance. It will cost this endeavour years also.
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#3038
by
PaulF
on 10 May, 2015 20:57
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Sure, but I'm just pointing out what the lack of cheap and readily available space access costs us in terms of either proving or disproving new propulsion theories. It would have saved Woodward 20 years of mucking about, for instance. It will cost this endeavour years also.
And I proposed a petition to Elon Musk / SpaceX. Nobody replied, is it such a bad idea?
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#3039
by
deltaMass
on 10 May, 2015 21:12
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