Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2102874 times)

Online Rodal

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....

In my opinion such a low tempo low priority side project that could probably be fully funded from the couch change from break room lounge chairs should not be micromanaged like it's a multi-billion dollar resource intensive space probe project and put under deadline pressure like that.

Probably the "micromanaging deadline" you are referring to is due to internal pressure at NASA because there are other NASA centers that were specifically chartered with "Advanced Space Propulsion" R&D: NASA Johnson was not chartered by management to conduct such "Advanced Space Propulsion" R&D, but instead it was chartered with human spaceflight training, research, and flight control.  Due to the demise of the Space Shuttle operations, there has been a curtailing of Johnson's funding.  By contrast, for example,  the George C. Marshall Space Flight Center (MSFC) was chartered as the U.S. government's civilian rocketry and spacecraft propulsion research center.

It is probably a response to criticism that NASA has too many centers spread through the country, created during the Apollo era when the budget for NASA was much larger (as a proportion of the US budget) and the ensuing in-fighting for where (at what NASA centers) should  "Advanced Space Propulsion" be conducted in an era of falling budgets.
« Last Edit: 03/03/2015 02:51 PM by Rodal »

Offline Mulletron

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http://www.ebay.com/itm/AERCOM-Microwave-RF-Isolator-Circulator-2-4GHz-20dB-isolation-Low-I-L-TESTED-/281549538390?ssPageName=ADME:L:OU:US:1120
Picked up one of these puppies on Ebay to protect my amp. Another example of broken time reversal symmetry in action.

Got about an oz of very expensive liquid metal from here:
http://www.amazon.com/Gallium-Indium-Eutectic-GaInSn-68-5%25/dp/B00KN92MWW/ref=sr_1_3?ie=UTF8&qid=1425074693&sr=8-3&keywords=galinstan

So back to the copper from way back: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326742#msg1326742
...
Been working with the supplier with a machine shop I posted about way back:
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326669#msg1326669
I'm going that route. The quote I got is: price: $120.00 layout + $51.63 for part + freight. So I have to pay the layout, then anyone else who wants one of these:

but built in 16oz copper, with a smooth butt seam inside, and 1/4" flange around edges, can get one for about 50 bucks plus shipping. If all this works out, it'll fulfill my goal of making a replication by DIYers easier. For me, paying the layout plus price about breaks even with buying the sheet myself and fumblefuddeling around trying to solder up a cone at home. So I'm happy. I'll get back with more later, when the items are at home.

Hello Mulletron,

Hope you'll be able to conduct another test, and I guess there are many other people like me who encourage you to continue.
How do you intend to measure the (very tiny) thrust ? Reading back NASA's paper, it seems they had to run the experiment in a lab with complex (and expensive) tools to remove all parasite effects that would interfere with the thrust from the apparatus. Maybe you have access to such equipment ?

--
Mathieu

Going to do a Cavendish experiment:
http://www.intalek.com/Index/Projects/Research/CavendishExperiment.htm
https://www.fourmilab.ch/gravitation/foobar/ (link is down right now, hope it comes back)


Don't need expensive gear. You can do amazing things with some fishing line and ingenuity.
« Last Edit: 03/03/2015 03:37 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Notsosureofit

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http://www.ebay.com/itm/AERCOM-Microwave-RF-Isolator-Circulator-2-4GHz-20dB-isolation-Low-I-L-TESTED-/281549538390?ssPageName=ADME:L:OU:US:1120
Picked up one of these puppies on Ebay to protect my amp. Another example of broken time reversal symmetry in action.

Got about an oz of very expensive liquid metal from here:
http://www.amazon.com/Gallium-Indium-Eutectic-GaInSn-68-5%25/dp/B00KN92MWW/ref=sr_1_3?ie=UTF8&qid=1425074693&sr=8-3&keywords=galinstan

So back to the copper from way back: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326742#msg1326742
...
Been working with the supplier with a machine shop I posted about way back:
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326669#msg1326669
I'm going that route. The quote I got is: price: $120.00 layout + $51.63 for part + freight. So I have to pay the layout, then anyone else who wants one of these:

but built in 16oz copper, with a smooth butt seam inside, and 1/4" flange around edges, can get one for about 50 bucks plus shipping. If all this works out, it'll fulfill my goal of making a replication by DIYers easier. For me, paying the layout plus price about breaks even with buying the sheet myself and fumblefuddeling around trying to solder up a cone at home. So I'm happy. I'll get back with more later, when the items are at home.

Hello Mulletron,

Hope you'll be able to conduct another test, and I guess there are many other people like me who encourage you to continue.
How do you intend to measure the (very tiny) thrust ? Reading back NASA's paper, it seems they had to run the experiment in a lab with complex (and expensive) tools to remove all parasite effects that would interfere with the thrust from the apparatus. Maybe you have access to such equipment ?

--
Mathieu

Going to do a Cavendish experiment:
http://www.intalek.com/Index/Projects/Research/CavendishExperiment.htm
https://www.fourmilab.ch/gravitation/foobar/ (link is down right now, hope it comes back)


Don't need expensive gear. You can do amazing things with some fishing line and ingenuity.

Same here.  The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.

Online Rodal

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If one looks closely at the contour plots of the TM modes in http://forum.nasaspaceflight.com/index.php?topic=36313.msg1340906#msg1340906, one will notice that Egan's contour plots have the maximum of the magnetic field occurring at the cone surface while my contour plots have the maximum of the magnetic field occurring at a distance from the cone's surface.  I have examined the source of this discrepancy.  My conclusion is that Egan's plots are incorrect regarding this feature, and they are inconsistent with the equations on Egan's post.  If anybody is interested to know why, I can post the mathematical proof and discussion for this conclusion.
« Last Edit: 03/03/2015 04:59 PM by Rodal »

Online flux_capacitor

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Does anyone clearly understand the reaction force R vs opposite thrust T in Shawyer's newest document "A Note on the Principles of EmDrive force measurement" that I attach to this message? Especially, the problem of the "restrained thruster" of fig. 3 where no movement could be detected at all?

Shawyer seems to imply that the EmDrive needs to experience an acceleration (even the slightest one) to create a force that would me measurable. A fully restrained cavity would not move at all. It reminds me of the the Mach effect thruster, where according to Woodward the material needs to undergo a proper acceleration while being energized, otherwise the transient mass fluctuation does not occur.

Evidently, Eagleworks' RF resonant cavity test article is fixed to the rest of the apparatus, but Shawyer explains any small thermal effect makes the walls move hence the center of gravity of the cavity also move a bit, and this would be enough for any small force to appear.
« Last Edit: 03/03/2015 08:51 PM by flux_capacitor »

Offline frobnicat

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Does anyone clearly understand the reaction force R vs opposite thrust T in Shawyer's newest document "A Note on the Principles of EmDrive force measurement" that I attach to this message? Especially, the problem of the "restrained thruster" of fig. 3 where no movement could be detected at all?

Shawyer seems to imply that the EmDrive needs to experience an acceleration (even the slightest one) to create a force that would me measurable. A fully restrained cavity would not move at all. It reminds me of the the Mach effect thruster, where according to Woodward the material needs to undergo a proper acceleration while being energized, otherwise the transient mass fluctuation does not occur.

Evidently, Eagleworks' RF resonant cavity test article is fixed to the rest of the apparatus, but Shawyer explains any small thermal effect makes the walls move hence the center of gravity of the cavity also move a bit, and this would be enough for any small force to appear.

From memory, nobody clearly understands what Shawyer is saying about forces and accelerations in this paper. I recall at least two comments on the apparent contradictions if you haven't seen them, by me and Rodal, here and there.
Stormbringer also makes an attempt here. Maybe better to unwind from the start with Mulletron bringing up this article.
Sorry if I forgot other contributors take on that.

To make my current line of inquiry explicit : if small thermal effect makes the walls move hence the center of gravity of the cavity also move a bit, then this might be enough for sustained small deviations of the linear displacement readings to appear, because the measures on Eagleworks balance have a gravitational pendulum component. Such sustained deviation would not need sustained net thrust.

Online Rodal

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Does anyone clearly understand the reaction force R vs opposite thrust T in Shawyer's newest document "A Note on the Principles of EmDrive force measurement" that I attach to this message? Especially, the problem of the "restrained thruster" of fig. 3 where no movement could be detected at all?

Shawyer seems to imply that the EmDrive needs to experience an acceleration (even the slightest one) to create a force that would me measurable. A fully restrained cavity would not move at all. It reminds me of the the Mach effect thruster, where according to Woodward the material needs to undergo a proper acceleration while being energized, otherwise the transient mass fluctuation does not occur.

Evidently, Eagleworks' RF resonant cavity test article is fixed to the rest of the apparatus, but Shawyer explains any small thermal effect makes the walls move hence the center of gravity of the cavity also move a bit, and this would be enough for any small force to appear.

No, it is indecipherable to me.  No wonder people asked him about this: other people have difficulty understanding Shawyer regarding these forces.

And what do Shawyer and W..... (if  W..... was also involved in this) mean by "fully restrained" ???????????

There is no infinitely rigid restraint in nature.  In NASA's Eagleworks tests the EM Drive is restrained by the torsional stiffness of the torsional pendulum's couple of RiverHawks.     Fully-restrained is mambo-jambo wording to me.  It would be better to use equations. A minimum acceleration is needed? What is the magnitude of that minimum acceleration and what governs its magnitude?  Need a stiff restraint to have no force? How stiff?  Is there a number? What governs the number?

But it may be my fault because I would much prefer an analytical paper where equations and mathematical symbols would greatly outweigh the number of words.   

« Last Edit: 03/03/2015 10:10 PM by Rodal »

Online flux_capacitor

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Thanks you two. I was under the bad impression I was silly for not understanding Shawyer's explanations.

Online Rodal

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Thanks you two. I was under the bad impression I was silly for not understanding Shawyer's explanations.
There is an easy way to test this.
Paul March said that they need to maximize the thrust for the experiment to be verified at NASA Glenn.
Paul March measures the displacement vs. time with an optical method as previously discussed in detail by zen-in  "Philtec D63 fiber-optic displacement sensor measures distance from its target mirror by measuring the intensity of the reflected light.".

If Shawyer is correct that the less restraint the better, then Paul March could lessen the current restraint in his experiments by replacing the RiverHawk bearing with another one (if available) having less stiffness.  If Shawyer is correct, the decrease in restraint should produce an increase in the measured response.
« Last Edit: 03/04/2015 12:04 AM by Rodal »

Online Rodal

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If one looks closely at the contour plots of the TM modes in http://forum.nasaspaceflight.com/index.php?topic=36313.msg1340906#msg1340906, one will notice that Egan's contour plots have the maximum of the magnetic field occurring at the cone surface while my contour plots have the maximum of the magnetic field occurring at a distance from the cone's surface.  I have examined the source of this discrepancy.  My conclusion is that Egan's plots are incorrect regarding this feature, and they are inconsistent with the equations on Egan's post.  If anybody is interested to know why, I can post the mathematical proof and discussion for this conclusion.
OK.  I will interpret the "likes" I got for the previous post, as meaning that they would like me to explain why I have arrived at the conclusion that Egan's contour plots that show the maximum of the magnetic field occurring at the cone surface are incorrect, and why my contour plots have the maximum of the magnetic field occurring at a distance from the cone's surface.

The solution to the resonant truncated cone 3-D cavity can be most conveniently expressed in spherical coordinates because the electromagnetic waves propagate as spherical waves inside it.  Spherical coordinates having three components: a spherical radius r (the radius of the sphere around the origin and two angles: a polar angle θ and an azimuthal angle φ.  The azimuthal angle φ describes a rotation around the longitudinal axis of the cone.  If you look at a cross-section (at a given value of the azimuthal angle φ, for example at φ=0) of the truncated cone that looks like a trapezium, the polar angle θ is perpendicular to the longitudinal axis.  We take θ =0 at the longitudinal axis, such that θ = - θw when touching the cone wall at the left and θ= + θw when touching the cone wall at the right.



The solution for the electromagnetic fields can be expressed in terms of three separate multiplicative functions: one function in terms of the azimuthal angle φ, another function in terms of the spherical radius r and a function in terms of the polar angle θ.

Clearly the problem we are facing (with respect to the location of the maximum of the magnetic field in the θ direction) has to do with the function that depends on θ.  This function is an associated Legendre function.  Greg Egan names this function Q(θ), see http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html.

The eigenvalue problem is finding a value "n" such that a function that Egan names Q1, where Q1=n(n+1)Q(θ), is zero at the edges (at the walls).   

Below I show a plot of Q1=n(n+1)Q(θ) as a function of θ, showing that indeed Q1=0 at the walls: at θ= - 20 degrees and at θ=20 degrees.

The function that determines the variation of the transverse magnetic field with θ, is the derivative of Q(θ) with respect to θ . Egan names this derivative Q'(θ).

I show below a plot of this function, Q'(θ), calculated by Mathematica analytically as the derivative of Q(θ) with respect to θ.  One can observe that this function (that governs the variation of the magnetic field in the polar angle direction θ) reaches an extremum before the ends.

I also show below a plot of the analytical expression that Greg Egan used to calculate this derivative:

Q'(θ) = n [cos θ Pn(cos θ) Pn1(cos θ)] / sin θ

Observe that this plot is exactly the same as the previous plot.  Greg Egan's analytic expression for the derivative Q'(θ) is correct: it agrees with Mathematica's calculation (one can also show this equality analytically with Mathematica by using == which gives "True" as a result).

So, why is Greg Egan showing the magnetic field reaching a maximum at the walls?

It occurred to me that perhaps this was due to Egan not including the sin  θ term (perhaps because sin θ goes to zero for θ going to zero, and therefore the expression for  Q'(θ) becomes 0/0 at θ=0, which needs special handling in a numerical code.  Analytically, however,  Limit  Q'(θ)  for θ -->0 is Q' -->0 )

Therefore, I show a plot of the numerator of Q'(θ) :
 
 Q'(θ) = n [cos θ Pn(cos θ) Pn1(cos θ)] / sin θ

Numerator Q'(θ) = n [cos θ Pn(cos θ) Pn1(cos θ)]

CONCLUSION: the plot of the numerator of Q'(θ)  (which therefore doesn't include sin θ occurring in the denominator) reaches an extemum at the walls, just like Greg Egan's plots.  Greg Egan's expression for Q'(θ) is correct: it should not give an extremum at the wall.  What are incorrect are the plots for the transverse magnetic fields for the TM modes.



Greg Egan's plots for the transverse modes may be based on using the numerator of Q'(θ) and neglecting sin θ in the denominator.  There is one issue remaining: the plot of the numerator is symmetric around the center, if Greg Egan's plots are due to only using the numerator, he would have had to further write the code such that for negative values of the polar angle ( θ < 0 ) the negative of the numerator is used instead, in order to result in the asymmetric magnetic field (the magnetic field has different signs for negative θ than for positive θ).
« Last Edit: 03/04/2015 11:55 AM by Rodal »

Offline frobnicat

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Thanks you two. I was under the bad impression I was silly for not understanding Shawyer's explanations.
There is an easy way to test this.
Paul March said that they need to maximize the thrust for the experiment to be verified at NASA Glenn.
Paul March measures the displacement vs. time with an optical method as previously discussed in detail by zen-in  "Philtec D63 fiber-optic displacement sensor measures distance from its target mirror by measuring the intensity of the reflected light.".

If Shawyer is correct that the less restraint the better, then Paul March could lessen the current restraint in his experiments by replacing the RiverHawk bearing with another one (if available) having less stiffness.  If Shawyer is correct, the decrease in restraint should produce an increase in the measured response.

The "restraint", understood as the rest equilibrium restoring torque, is more a matter of inclination of the plane XY of rotation of the arm of balance in gravity than from the flexure bearings stiffness :

The application point of the calibration pulses is 11.5''=.292m from the axis, and the linear displacement measured at 14.5''=.368m from the axis (inferred from the nice lateral view in this post) and knowing the arm's end is 15.5'' from axis and faztek beam is 1.5'' sided.

Calibration pulse of 29.1N at .2921m gives a torque of 8.50e-6 Nm
The 2 flex bearings are given for .007 in-Lb/deg each (+-10%), that is 9.06e-2 Nm/rad (total)
Under a torque of 8.50e-6 the angle of deflection would be 8.50e-6/9.064e-2=9.38e-5 rad
That would make a linear deviation of 34.5 m

In all charts, the deviation associated with calibration pulse of 29.1N is roughly between 1 and 2.5 m, one order of magnitude less.

The other way around :
For charts with 2.5m deviation on cal. pulse, deflection angle=6.79e-6 rad, that would make the flexure bearings restoring torque at 6.16e-7 Nm (given the stiffness). Compared to 8.50e-6 Nm of the torque induced by the cal. pulse that represents only 7.25%


m dev / cal. pulse       ratio of restoring torque due to stiffness of flexure bearings
2.5                                7.25 %
2                                   5.80 %
1                                   2.90 %


The only thing that I see that can account for the apparent lacking torque is the equilibrating torque induced by the inclination of the plane of rotation of the arm toward the CoM of the rotating assembly, that is equivalent to a hanging pendulum. The way it is used, the balance is more than 90% a hanging pendulum and less than 10% a torsion pendulum driven by flexure stiffness.

If this analysis holds, small changes in stiffness of flexure bearings would make for a minor impact on results. Changes in inclination would be the major way to tune the (linearised hanging pendulum equivalent) stiffness.

Online Rodal

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....
The only thing that I see that can account for the apparent lacking torque is the equilibrating torque induced by the inclination of the plane of rotation of the arm toward the CoM of the rotating assembly, that is equivalent to a hanging pendulum. The way it is used, the balance is more than 90% a hanging pendulum and less than 10% a torsion pendulum driven by flexure stiffness.

If this analysis holds, small changes in stiffness of flexure bearings would make for a minor impact on results. Changes in inclination would be the major way to tune the (linearised hanging pendulum equivalent) stiffness.

A hanging pendulum hangs from a rigid support located above the weight.  Its period depends only on the length of the pendulum's arm (and g , the acceleration of gravity, which is practically constant on Earth).  The flexural stiffness of the pendulum's arm is negligible.

But here nothing is hanging from the stainless steel chamber "rigid ceiling" supported by arms with negligible flexural stiffness.

What I see is the EM Drive weight supported by a frame of Faztek aluminum beams, Faztek beams that are supported from below, not from the stainless steel chamber ceiling.



What rigid support (located above the EM Drive) is the EM Drive hanging from ?  (Where is the "hanging pendulum" rigid support located ?)

What constitutes the arm of the "hanging pendulum"?  Why does it have negligible flexural stiffness? (The flexural stiffness of the aluminum Faztek beams is far from being negligible)

Do you really mean a hanging pendulum (whose period depends only on the length of the arm)?
Or do you mean a flexural pendulum (whose period depends on the stiffness of the arm)?


And if you agree that the flexural stiffness of the arms are not negligible, why take into account only the portion above the weight?  What about the flexural stiffness below the weight? 
Aren't the Faztek beams supported from below?

What I see is your "z" axis going up to a Faztek frame or "bridge" and the "bridge" being supported by two vertical Faztek beams, and those vertical Faztek beams are supported from below, not from above.

Is that then really an inverted flexural/torsional pendulum since it is made by Faztek aluminum beams supported from below?


« Last Edit: 03/04/2015 02:44 AM by Rodal »

Online aero

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Do you mean that this might actually be right? I've ignored the fields that look like this because I thought they were supposed to be symmetric.
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Online Rodal

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Do you mean that this might actually be right? I've ignored the fields that look like this because I thought they were supposed to be symmetric.

electric fields are asymmetric like this about the longitudinal axis like this (electric azimuthal field TE013):

it has to be asymmetric because the electric field in the circumferential (azimuthal) direction is constant for TE013, hence when looking at the cross-section, the field vector (at a given distance away from the bases) is coming out of the paper at the right and it is going into the paper at the left, and viceversa for the other (total of 3) different fields along the axis)

« Last Edit: 03/04/2015 02:42 AM by Rodal »

Offline Star-Drive

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Dr. March,

I'm trying to model various aspects of the whole system to put upper bounds on thermal effects, and possibly also reconstruct the thrust(t) original signal from the distance(t) given in the charts. It would be a nice boost to this (amateur level) effort if you could confirm either :
- That the flexure bearings have a stiffness of 0.007 in-Lb/deg ? Each ? Both together ? Do you know the exact model reference ?
- That the vertical scale in the charts (indicated in m, around 500) are relevant or not relevant.

I ask this question because I find a contradiction between the stiffness around the vertical axis and the recorded deviation from the 30N calibration pulses (at .007 in-Lb/deg the deviation of the linear displacement sensor would be above 40m, at .014 in-Lb/deg still above 20m). The readings amount for between 1 to 2.5 m for the 30N calibration pulses. So I'm stuck.

While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilisation or tuning purpose) ? That could explain the varying deviation (in m) for the same calibration pulses thrusts. Also wondered if this is what was implied in this post :
Quote from: Star-Drive
...
These thermally induced actions to the left requires the torque pendulum's arm to move to the right to maintain the balance of the torque pendulum's arm in the lab's 1.0 gee gravity field, since we also use the Earth's g-field to help null the pendulum's movements.
...

Thanks


Frobnicat:

To answer your question:

" - That the flexure bearings have a stiffness of 0.007 in-Lb/deg ? Each ? Both together ? Do you know the exact model reference?"

The two torsion bearings used in or torque pendulum are supposed to have a stiffness of 0.007 in-Lb/deg, +/-10% and is made by the Riverhawk Co. in New York USA.  As to their model number find the data sheet for same attached. 

"- That the vertical scale in the charts (indicated in m, around 500) are relevant or not relevant."

The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm.  The data sheet for same is attached.

"While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilization or tuning purpose)?"

The design of our Torque pendulum follows what JPL and Busek Co did at their respective facility, see attached report from Busek.  We found that if we tried to keep the arm completely horizontal though that the pendulum's neutral point would wonder erratically and make alignments near impossible.  So yes I balance the pendulum arm so there is always a slight tilt in it, however this tilt angle magnitude is not controlled as well as it probably should.

Best, Paul M.

Thank you very much for those precious informations. The tilt angle magnitude can probably be inferred from the deviation against the calibration pulses, if we can model the gravitational pendulum component on top of the flexure bearing restoring torque component.

For that we need to know :

Mass of :
  frustum, without dielectric : 1.606 kg
  microwave power amplifier : below 8kg ? 
  faztek horizontal beam : 2.18 Lb (from 1.09Lb/Ft) ?
  Ideally, Total mass with a rough estimate of position of each part...
 
Distances along the arm from vertical axis of rotation to the centre of :
  Long end of arm (frustum side) : 15.5''
  Short end of arm (amplifier side) : 8.5''
  Frustum : 15.5 - 4 = 11.5'' ?
  Electrostatic Fins Calibration System : 15.5-4 = 11.5'' ?
  Linear Displacement Sensor : 15.5-1 = 14.5'' ?
  microwave power amplifier : between 4.25'' and 8.5'' ? 

Stiffness of flexure bearings : .014 in-Lb/deg total  (2 times .007 each)

In short : what is the total mass of the whole rotating assembly, where is the centre of mass of the whole rotating assembly relative to axis of rotation, and what is the moment of inertia around the (almost) vertical axis of rotation (for the later, to assess the dynamics and not just the equilibrium).

green : explicitly provided value
orange : inferred from pictures or derived by me from faztek sellers, to be confirmed
red : not found, do we have better than bounds for those ?




Some of your questions are answered below in ( ).

Mass of:
frustum, without dielectric : 1.606 kg
microwave power amplifier : below 8kg ? (7.64118 kg + 0.200 kg mass)
faztek horizontal beam : 2.18 Lb (from 1.09Lb/Ft) ?  (0.92338 kg)
Ideally, Total mass with a rough estimate of position of each part...

Distances along the arm from vertical axis of rotation to the centre of :
Long end of arm (frustum side) : 15.5''    (14.75)
Short end of arm (amplifier side) : 8.5''    (9.25)
Frustum : 15.5 - 4 = 11.5'' ?                   (11.25)
Electrostatic Fins Calibration System : 15.5-4 = 11.5'' ?  (11.25)
Linear Displacement Sensor : 15.5-1 = 14.5'' ?  (13.88)
Center of microwave power amplifier assembly: between 4.25'' and 8.5'' ? (~7.5)

Best, Paul M.
Star-Drive

Online aero

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Thank you Dr. Rodal - So here is the complete set for some magnetic source run. I didn't record any details except I can see  that the antenna in in the location of the magnetic antenna I use.  Is it possible that all of the images are correct? If so that would increase my confidence in the meep output.

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I'm currently trying to finish up the cross section drawing on the flight demonstrator, but i kinda fail to understand how it fits together....

Looking closely (top down wise) at the lower rim it seems to me there is :

-small shiny rim (could be the edge of the alu cone?)
-brownish plate (copper plate?)
-small shiny rim
-thick plate (most probably holding the screw thread)

I'm puzzled about the second small, shiny rim...
Why would you need an additional small slab of alu under the (supposedly) copper plating?
Any one has an idea?
« Last Edit: 03/04/2015 04:50 AM by Flyby »

Offline Notsosureofit

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The "Copper" is just the reflection of the floor from the side of the flange.  The 2 bright lines are reflections from the edge bevels.  If they used the Copper CF (or wire) seals they are located inside of the bolt line.

Online Rodal

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Thank you Dr. Rodal - So here is the complete set for some magnetic source run. I didn't record any details except I can see  that the antenna in in the location of the magnetic antenna I use.  Is it possible that all of the images are correct? If so that would increase my confidence in the meep output.
Yes, they can all be correct.  But we need your help in identifying the images you posted.  The electric and magnetic fields are vectors in 3-D space, with orthogonal base vector components.


For example, what does this represent? Is this a contour plot of the electric field component oriented along the axial direction  (the vector component oriented along the "y" axis)? The reason why I think it is the axial component is because the axial component should be symmetric about the "y" axis (which it is)

Notice how although you impose flat faces, the electromagnetic field inside the cavity wants to be spherical (thus the 2 curved boundaries between the 3 contour regions).  Left to its own, Nature will do what it wants to do: to propagate as spherical waves.  The radii of the 2 curved boundaries look correct.  The radii of curvature seem to have the same center as the focal point of  intersection of the sides of the truncated cone (the vertex or apex of the cone).

« Last Edit: 03/04/2015 01:25 PM by Rodal »

Online Flyby

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nah, it is not to be dismissed as reflection of the surroundings or floor. Reflections do no behave like that on a cylindrical object...
Believe me, you'd need a very odd shaped floor to achieve such type of reflections on a cylindrical object..

I added 2 renders that use raytracing, and from different height to catch a glimps of the bright surroundings and the wood table. No way you're getting that parallel bright edge as seen on the original picture.

there is only 1 way to explain it : it is a different, brownish material that is sandwiched between high reflective surfaces...
maybe, but highly improbable, it is a brown-ish tape at the edge...

But it is NOT a reflection.
The similarity of colour between the strip and the wood table is merely coincidence..

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