Author Topic: EM Drive Developments Thread 1  (Read 763731 times)

Online Rodal

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Re: EM Drive Developments
« Reply #2440 on: 10/22/2014 05:29 PM »
Paper by Prof. Barrett and Masuyama in the proceedings of the Royal Society, containing theory, equations and experiments:

http://royalsocietypublishing.org/content/469/2154/20120623








« Last Edit: 10/22/2014 05:33 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #2441 on: 10/22/2014 05:33 PM »
There is also information supporting existence of a conductive layer next to the end walls of the cavity.

http://www.chee.uh.edu/sites/chbe.egr.uh.edu/files/faculty/economou/jap_sheath.pdf

And look at the photo of the flight thruster. I don't see any place for leaks in the axial direction.

 Mean specific thrust = 326mN/kW

http://www.emdrive.com/flightprogramme.html
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Online Rodal

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Re: EM Drive Developments
« Reply #2442 on: 10/22/2014 05:37 PM »
...

 I don't see any place for leaks in the axial direction.

...

Look at direction of thrust force with respect to the ionic air:






I can envision the "upper electrode" being formed by the perimeter edge of the the flat base of cone and the "insulation" taking place at the gap between the flat base and the round surface of the truncated cone.

Thrust would be greater on the larger base due to its larger perimeter.

There are all those bolts directed in the axial direction of the cone.  Corona discharge could take place at those bolts/and/or/at the perimeter edge of the flat base. 

« Last Edit: 10/22/2014 06:52 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #2443 on: 10/22/2014 05:49 PM »
What you are saying is that these EM thruster devices need to be checked with a smoke trails, like air flow in a wind tunnel is highlighted. Hold a lighted punk stick next to it and turn the device on.

Wouldn't their be some time delay between power on/off and thrust on and off?

Does anyone want to take a crack at estimating the dimensions of the flight thruster. It operated at 3.85GHz and weighed 2.92 Kg. That is a new operating frequency data point for us if we can get dimension. If nothing else, we should be able to get the taper angle pretty accurately, as well as the ratios of big/little and big/height.
« Last Edit: 10/22/2014 05:56 PM by aero »
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Online Rodal

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Re: EM Drive Developments
« Reply #2444 on: 10/22/2014 05:54 PM »
What you are saying is that these EM thruster devices need to be checked with a smoke trails, like air flow in a wind tunnel is highlighted. Hold a lighted punk stick next to it and turn the device on.

Wouldn't their be some time delay between power on/off and thrust on and off?
Have to think about what would a time constant involved in delay depend on.  The electric effect is practically instantaneous.  Momentum transfer has to do with hydrodynamics.  There is no heat capacity and thermal difussivity involved like in a thermal effect.  Time constant could depend on Reynolds number, hence viscosity, but viscosity of air is low. Also, speed of sound in air is 343 metres per second, which is pretty fast for these considerations.

What is the time delay for the craft shown in this video?  Seems to take off in an impulsive manner:


« Last Edit: 10/22/2014 06:10 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #2445 on: 10/22/2014 06:19 PM »
The time delay is not noticeable. I don't know if the time delay difference between this device and the EM thrusters could be detected. I don't think it can be with the data we have available to us.
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Offline aero

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Re: EM Drive Developments
« Reply #2446 on: 10/22/2014 06:20 PM »
...

Does anyone want to take a crack at estimating the dimensions of the flight thruster. It operated at 3.85GHz and weighed 2.92 Kg. That is a new operating frequency data point for us if we can get dimension. If nothing else, we should be able to get the taper angle pretty accurately, as well as the ratios of big/little and big/height.

Please provide a link for this " flight thruster.. operated at 3.85GHz and weighed 2.92 Kg.", and if possible attach a picture.  Thanks

here - http://forum.nasaspaceflight.com/index.php?topic=29276.msg1275021#msg1275021
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Offline zen-in

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Re: EM Drive Developments
« Reply #2447 on: 10/22/2014 06:52 PM »
The time delay is not noticeable. I don't know if the time delay difference between this device and the EM thrusters could be detected. I don't think it can be with the data we have available to us.

Actually the time delay is visible in these two plots of thrust data vs time.   The first one is from Shawyer's 2008 paper.   His 2013 and 2014 IAC papers don't have this kind of raw data.   Both the up and down thrust roughly follow an exponential rise after power is applied and there is continued acceleration after the power is turned off.

The second plot is from the JSC paper - Brady, White, et al.  This also has a roughly exponential rise and continued thrust after RF power is turned off until the Cal pulse wipes it out.

Both experiments show the signature of a thermal effect.  As in a Crookes radiometer.
« Last Edit: 10/22/2014 06:56 PM by zen-in »

Online Rodal

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Re: EM Drive Developments
« Reply #2448 on: 10/22/2014 06:57 PM »
The time delay is not noticeable. I don't know if the time delay difference between this device and the EM thrusters could be detected. I don't think it can be with the data we have available to us.

Actually the time delay is visible in these two plots of thrust data vs time.   The first one is from Shawyer's 2008 paper.   His 2013 and 2014 IAC papers don't have this kind of raw data.   Both the up and down thrust roughly follow an exponential rise after power is applied and there is continued acceleration after the power is turned off.

The second plot is from the JSC paper - Brady, White, et al.  This also has a roughly exponential rise and continued thrust after RF power is turned off until the Cal pulse wipes it out.

Both experiments have a thermal effect signature.

Yes, some kind of a delay but not thermal for NASA Eagleworks. Around page 30 to 40 of this thread I calculated the thermal time delay based on the thermal diffusivity (thermal capacity and thermal conductivity) for the NASA Eagleworks experiments and ruled out the time delay and time decay as due to thermal effects because the Fourier time due to thermal effects is much longer than the ~2 second delay in the NASA Eagleworks experiments in the pulse rise from the baseline.

The exponentially decaying rise after the initial 2 sec pulse may indeed be a thermal effect.  Maybe related to their "baseline problem due to the magnetic damper interaction with the power cable..."

Ionic wind time delay ?

Paul March had also though about thermal effects and wrote about it.  It is interesting that while these researchers can rule out thermal effects (based on standard heat transfer texts) the theory of ionic wind has not been written until recently.  Perhaps nobody has computed or ruled out ionic wind, really...
« Last Edit: 10/22/2014 07:08 PM by Rodal »

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #2449 on: 10/22/2014 07:03 PM »
What about the gauge constant for the springs?  How far does it have to move for the force to be read ?

Online Rodal

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Re: EM Drive Developments
« Reply #2450 on: 10/22/2014 07:05 PM »
What about the gauge constant for the springs?  How far does it have to move for the force to be read ?

<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>  Brady et.al. page 3
« Last Edit: 10/22/2014 07:07 PM by Rodal »

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #2451 on: 10/22/2014 07:07 PM »
What about the gauge constant for the springs?  How far does it have to move for the force to be read ?

<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>

Yes, but how much displacement are we talking about and how long does it take to get there?

Online Rodal

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Re: EM Drive Developments
« Reply #2452 on: 10/22/2014 07:26 PM »
What about the gauge constant for the springs?  How far does it have to move for the force to be read ?

<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>

Yes, but how much displacement are we talking about and how long does it take to get there?

The displacements are never given in the Brady report.  They only write over and over again about "displacements that correspond to ... microNewtons"

They also write:

<<Immediately prior to a test run data take, the displacement/force relationship is verified by inducing a known force onto the pendulum arm and measuring the displacement. This is done via the electrostatic fins calibration mechanism. This mechanism uses two sets of aluminum fins, one set on the fixed structure and one set on the pendulum arm. The fins overlap without touching. A calibration voltage is applied to the fixed structure fins, which induces a force upon the pendulum arm fins and an associated displacement that is measured by the LDS. The electrostatic fins design provides a constant force over a reasonably large range (between 30-70% overlap), so adjustments to the calibration mechanism between test run data takes and even between test article reconfiguration are usually not required. Calibration of the overlap/force relationship was accomplished using a Scientech SA 210 precision weighing balance (resolution to one micronewton).>>

Online Rodal

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Re: EM Drive Developments
« Reply #2453 on: 10/22/2014 07:33 PM »
What about the gauge constant for the springs?  How far does it have to move for the force to be read ?

<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>

Yes, but how much displacement are we talking about and how long does it take to get there?

Also Paul March wrote in this thread:  << The Riverhawk C-flex torsion bearing's spring constant is a nominal 0.007 in-Lb/deg., but that varies with the mass load mounted on the torque pendulum arm and selected balance point of the test article mass and its counterbalance mass on the other end of the pendulum arm relative to the torque pendulum’s center of rotation. >>

However this torsional spring constant greatly disagrees with the natural frequency quoted by Paul March. The natural frequency quoted by Paul March indicates a much stiffer spring constant.

Offline aero

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Re: EM Drive Developments
« Reply #2454 on: 10/22/2014 07:52 PM »
I made a kludge estimate of the Flight thruster dimensions operating at 385 GHz.

w-small =    7.062943185   cm
w-big =   11.02062266   cm
height =    7.114289902   cm

I didn't find anything to use as a reference length so I took Shawyer's statement, "The small end diameters are set just above the cut-off diameter corresponding to the mode and frequency of the design." and made the assumption that he used the same rule here as on the Experimental device, Shawyer a". Then using the wavelength = 2.45 GHz and w_small = 11.1 cm for Shawyer a", simply reduced the small diameter down for frequency ratio. With that and the pixel measurements off the photo, converted all to cm.

The CAD tools should give better pixel lengths but I don't know where to get a better reference length.
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Online Rodal

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Re: EM Drive Developments
« Reply #2455 on: 10/22/2014 07:56 PM »
I made a kludge estimate of the Flight thruster dimensions operating at 385 GHz.

w-small =    7.062943185   cm
w-big =   11.02062266   cm
height =    7.114289902   cm

...

I am dizzy with all the tests that Shawyer has conducted and with the different names he gives the tested device.  Am I correct that this "flight thruster" is yet a different tested device than the "experimental" and the "demonstrator" Shawyer devices?  Did he test this "flgiht thruster" before or after the other two?

==> Perhaps you can send another e-mail to Shawyer saying that we need actual dimensions of his devices to make sense of the data
« Last Edit: 10/22/2014 07:59 PM by Rodal »

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #2456 on: 10/22/2014 07:59 PM »
What about the gauge constant for the springs?  How far does it have to move for the force to be read ?

<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>

Yes, but how much displacement are we talking about and how long does it take to get there?

Also Paul March wrote in this thread:  << The Riverhawk C-flex torsion bearing's spring constant is a nominal 0.007 in-Lb/deg., but that varies with the mass load mounted on the torque pendulum arm and selected balance point of the test article mass and its counterbalance mass on the other end of the pendulum arm relative to the torque pendulum’s center of rotation. >>

However this torsional spring constant greatly disagrees with the natural frequency quoted by Paul March. The natural frequency quoted by Paul March indicates a much stiffer spring constant.

A much higher frequency might indicate flex in the arm itself.  (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)

Online Rodal

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Re: EM Drive Developments
« Reply #2457 on: 10/22/2014 08:06 PM »
....
A much higher frequency might indicate flex in the arm itself.  (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)

A higher frequency because you think that the frequency is due to beam bending rather than torsion of the bearing?

In other words, this would mean that the frequency Paul March is referring to would not be the lowest frequency.

I did some calculations some time ago based on known stiffness of the Faztek beams (1.5" by 1.5"), and the bending frequency would be way too high compared to Paul March's stated frequency assuming the inverted pendulum to be effectively clamped by the bearings as a cantilevered beam.  So if the frequency given by Paul March is related to beam bending it would have to be also due to substantial flexibility from the bearings (not providing a perfect clamp).

My impression is that the discrepancy in stiffness is due to the total supported weight.  Paul March stated that the torsional stiffness is dependent on weight.  I used the number given by Paul March, (25 pounds if I remember correctly), but the total weight could be quite different and hence explain the different stiffness value, as the frequency is dependent on the square root of the (torsional) stiffness divided by the mass (moment of inertia) .  Hence the frequency is very dependent on the unknown supported mass, both appearing in the denominator and also affecting the numerator because of the torsional spring constant (unknown dependence on supported mass).
« Last Edit: 10/22/2014 08:31 PM by Rodal »

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #2458 on: 10/22/2014 08:14 PM »
....
A much higher frequency might indicate flex in the arm itself.  (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)

A higher frequency because you think that the frequency is due to beam bending rather than torsion of the bearing?

In other words, this would mean that the frequency Paul March is referring to would not be the lowest frequency.

I did some calculations some time ago based on known stiffness of the Faztek beams (1.5" by 1.5"), and the bending frequency would be way too high compared to Paul March's stated frequency assuming the inverted pendulum to be effectively clamped by the bearings as a cantilevered beam.  So if the frequency given by Paul March is related to beam bending it would have to be also due to substantial flexibility from the bearings (not providing a perfect clamp).

Tough call w/ all that stuff hanging out there.  Can't see too much in the pictures and not too crazy about the way the chamber is set on.  Could be anything that vibrates.  What were the frequencies ?

Online Rodal

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Re: EM Drive Developments
« Reply #2459 on: 10/22/2014 08:22 PM »
....
A much higher frequency might indicate flex in the arm itself.  (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)

A higher frequency because you think that the frequency is due to beam bending rather than torsion of the bearing?

In other words, this would mean that the frequency Paul March is referring to would not be the lowest frequency.

I did some calculations some time ago based on known stiffness of the Faztek beams (1.5" by 1.5"), and the bending frequency would be way too high compared to Paul March's stated frequency assuming the inverted pendulum to be effectively clamped by the bearings as a cantilevered beam.  So if the frequency given by Paul March is related to beam bending it would have to be also due to substantial flexibility from the bearings (not providing a perfect clamp).

Tough call w/ all that stuff hanging out there.  Can't see too much in the pictures and not too crazy about the way the chamber is set on.  Could be anything that vibrates.  What were the frequencies ?
As having done R&D in dynamics work too  I completely agree with your statement "w/ all that stuff hanging out there...not too crazy about the way the chamber is set on."

Concerning the natural frequency, this is exactly what Paul March wrote:

Quote
The natural oscillation period of the pendulum arm when loaded with the RF amplifier, its RF plumbing and the test article was around 4.5 seconds.

So that is

f = 0.222 Hertz

omega = 1.39626 radians / second
« Last Edit: 10/22/2014 08:24 PM by Rodal »

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