Author Topic: EM Drive Developments - related to space flight applications - Thread 9  (Read 1051008 times)

Offline Rodal

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Be careful: using a similar music wire (Music wire ASTM A228, E = 207 GPa) with

2x the diameter will have 16x the torsional stiffness, hence 1/16 of the displacement for the same force and radius

1.5x the diameter will have 5x the torsional stiffness 1/5 of the displacement for the same force and radius

So stiffer wire will make the system respond more quickly, at the expense of displacement for the same force. That means for 2x stiffness, the ~12uN force I saw over ~100um will be ~50um, which is still within the 3um resolution of the laser displacement sensor.  I happen to have some #18 wire. Can you tell me what the % of the displacement for the same force and radius for that diameter wire will be? Also, what kind of speed response are we talking about here, twice as fast for twice as stiff?

DISPLACEMENT measured at same radius, with same EM Drive force

the static displacement goes like the inverse of D4

Gage #   D (in)        Stiffness Ratio   Increase in stiffness     Displacement at same radius and force

14          0.033        1                         0                                     100 %
18          0.041        2.38                138 %                                   42 %

The dynamic response should usually be proportional to the static displacement times a dynamic magnification factor (usually ~2), therefore still proportional to D4


FREQUENCY with same suspended moment of inertia, same wire length and modulus

The frequency goes like √(k/I)

like the square root of the torsional stiffness k divided by the moment of inertia I

where

k = (Pi * D4/(32 L))  E/(2(1+ν))

So, keeping I constant, and everything else except D constant, the frequency goes like D2 : the square of the diameter of the wire

So, assuming that the rotary moment of inertia I, stays approximately the same (because it is governed by the suspended mass, and the larger diameter wire contributes negligibly to the moment of inertia I), same length and same material, the frequency will go like the square of the diameter.

For #18 compared to #14, this means that the frequency ratio will be (0.041/0.033)2=1.54 , hence 54% higher frequency using #18 wire (D=0.041 in)  of angular motion of the torsional pendulum.  And the displacement will be smaller (0.033/0.041)4=0.42 ratio: only 42% of the previous displacement measured at the same radius with the same EM Drive force

Again, this is assuming that you keep:

* same length of wire between restrained end and the suspended load (whatever the length is)
* same wire modulus (Music wire ASTM A228 )
* #18 wire (D=0.041 in) compared to #14 wire (D=0.033 in)
* same suspended mass and dimensions (same moment of inertia "I" )
« Last Edit: 02/16/2017 11:34 PM by Rodal »

Offline TheTraveller

...
There may well be grey areas in the Rf power to force generation curve and Jamie's thruster may well be in the low power doldrums where  with limited Q the thruster may struggle to achieve a solid operational mode.
...

Only if you can come up with a (plausible) physical reason for this. Otherwise: no extra spooky free parameters.

You mean spooky like:

1) EW force direction reversal with dielectric (small and leading) and without a dielectric (big end leading)at the small end using a tight torsion pendulum?

2) EW TE012 non dielectric force direction big end leading using a tight torsion pendulum?

3) SPR TE01x non dielectric STATIC scale test rig force direction big end leading?

4) SPR TE01x non dielectric DYNAMIC rotary test rig force direction small end leading?

5) Dave's non dielectric small end leading force on a lose torsion pendulum?

6) Jamie's TE013 non dielectric small end leading force on a lose torsion pendulum?

7) My non dielectric TE013 big end leading on a scale?

8) Iulian's non dielectric small end leading on a spring based scale, which is a lose measuring system.


Roger's rotary, Jamie's, Dave's & Iulian's test rigs were lose and would have allowed quite some distance to move before being stopped by the force restrictive element of the test rig. All of the other were either scale based or very tight and allowed very little free movement.

Roger's advise is that the thruster needs to be free to accelerate to generate a small leading accelerative REACTION force as otherwise the static THRUST force will be generated. How much free movement is needed to achieve this yet to be determined. From that above, one would suggest there is a no mans land between the 2 modes, with a grey area. My own feelings are that the size of the grey area has factors of power, freq stability, the amount of phase distortion in the travelling waves at the resonant driving freq plus maybe more factors yet to be discovered.

Should add that Paul has seen big end leading force direction produced from the small end EW dielectric loaded thruster, where it normally produced small end leading force. Spooky or just a grey band operational characterists of EmDrive thrusters?

What seems to be emerging from the data is the tightness or looseness of the test rig, ie um of movement per uN of force does seem to have an effect on the direction of the force that is generated.

Question being does the design and tightness, limited distance to move, of the test rig cause a change in the direction of the generated force? Available data suggests there may be an effect.
« Last Edit: 02/16/2017 09:12 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline Rodal

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...

Question being does the design and tightness, limited distance to move, of the test rig cause a change in the direction of the generated force? Available data suggests there may be an effect.
Question being about this guideline by Shawyer...

So, can you tell us, according to you what governs whether a torsion pendulum is "tight" or "lose" ?

Is it a given displacement? Is the displacement all that matters? regardless of the applied force?  Why?
What is the limit displacement where it goes from tight to lose ?



Is it a given force? Is the force all that matters? regardless of the resulting displacement?  Why?
What is the limit force where it goes from tight to lose ?



Is it a stiffness?  (Force divided by displacement)  Why?
What is the limit stiffness where it goes from tight to lose?



Is it a given velocity? Is the velocity all that matters? regardless of the applied force?  Why?
What is the limit velocity where it goes from tight to lose ?



Is it a given acceleration? Is the acceleration all that matters? regardless of the applied force?  regardless of the mass? Why?
What is the limit acceleration where it goes from tight to lose ?
« Last Edit: 02/16/2017 10:37 PM by Rodal »

Offline Monomorphic

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Here are the latest images showing new main amps location as well as the alterations to the dampening system.

Offline TheTraveller

...

Question being does the design and tightness, limited distance to move, of the test rig cause a change in the direction of the generated force? Available data suggests there may be an effect.
Question being about this guideline by Shawyer...

So, can you tell us, according to you what governs whether a torsion pendulum is "tight" or "lose" ?

Is it a given displacement? Is the displacement all that matters? regardless of the applied force?  Why?
What is the limit displacement where it goes from tight to lose ?



Is it a given force? Is the force all that matters? regardless of the resulting displacement?  Why?
What is the limit force where it goes from tight to lose ?



Is it a stiffness?  (Force divided by displacement)  Why?
What is the limit stiffness where it goes from tight to lose?



Is it a given velocity? Is the velocity all that matters? regardless of the applied force?  Why?
What is the limit velocity where it goes from tight to lose ?



Is it a given acceleration? Is the acceleration all that matters? regardless of the applied force?  regardless of the mass? Why?
What is the limit acceleration where it goes from tight to lose ?


Don't believe there are yet experimentally determined "Freedom of Movement required to engage accelerative, big to small, REACTION force generation" definitions. Rogers guidelines are that the EmDrive must be unrestrained and capable of movement, plus there needs to be an initial external accelerative force big to small.

As to the experimental data:

1) EW test rig shows around 7.7um of movement for 182uN of force or 0.042um / uN of movement as attached.

2) Jamie's test rig showed 112um of movement for 12uN of force or 9.33um / uN of movement.

Which shows the EW test rig is approx 222x stiffer, ie more resistance to movement per unit of applied force. To put that another way, 100uN of force applied to the EW test rig should result in approx 4.2um of movement, where Jamie's test rig should allow 933um of movement. Massive difference in the allowed movement.

112um seems to be enough movement to allow Jamie's EmDrive thruster to engage accelerative, big to small, REACTION force generation and for the EW case, small enough for the TE012 non dielectric EmDrive thruster to not be able to engage REACTION force mode but to instead engage the static, small to big, THRUST force mode.

I suspect Dave and Iulian's test rigs also allowed a lot more movement per 100uN of force than the EW test rig, which is more like a scale.
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Offline TheTraveller

Here are the latest images showing new main amps location as well as the alterations to the dampening system.

Jamie,

Is the damper in line with the centre of rotation of the test rig or off to one side?

If off to one side, might suggest it should be moved so it works in the same rotation axis as the test rig.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline graybeardsyseng

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Here are the latest images showing new main amps location as well as the alterations to the dampening system.

Jamie -
Congrats on "first light" data on your excellent build.  Now the fun part starts of chasing possible error sources etc.   This really is excellent work.

IIRC a few pages back in discussion with Phil you indicated that you didn't yet have a bi-directional coupler .   If it would be helpful I have one I would be happy to loan you as I will not be needing for my build until at least the end of March.   It is a Supex 1.8 to 4 Ghz coupler.   the sensed signals are 14.5 dB down from the thru signal.  Not new but it seems to work well.   As near as I can tell it has about 1 dB insertion loss.  I am attaching a picture below.   If you would be interested PM me. 

BTW - for all DYIers out there - let me point out a most excellent source of materials, often at very low prices.  These are swap meets for amateur  radio operators (hams) - called hamfests or radio rally's  in some countries.  At a recent one here in Dallas I picked up a 5 watt broadband microwave amp capable of operating from 1.8 through 3 Ghz.  Cost - $5.00.   And it works.  Google ARRL hamfest calendar to find locations and dates in the US.  Similar data is available via other national amateur radio organizations (see Wikipedia).

Herman - W5HLP
graybeardsyseng
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Offline Monomorphic

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Here are the latest images showing new main amps location as well as the alterations to the dampening system.

Jamie,

Is the damper in line with the centre of rotation of the test rig or off to one side?

If off to one side, might suggest it should be moved so it works in the same rotation axis as the test rig.

I've already tried this. The damper is off to one side for best results. Dampening along center axis leads to being underdamped as the paddle plows through less oil. The paddle would need to be several times larger and I'm already at the limit of the reservoir now.
« Last Edit: 02/17/2017 12:43 PM by Monomorphic »

Offline Rodal

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I added further calculations to my post:

https://forum.nasaspaceflight.com/index.php?topic=41732.msg1641866#msg1641866

proving that the effect of the change in diameter of the wire due to deformation under load (= yield load or lower) is also negligible for the calculation of the torsional stiffness of the wire and for the calculation of the natural frequency of the torsional pendulum.
« Last Edit: 02/17/2017 03:42 PM by Rodal »

Offline Peter Lauwer

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You mean spooky like:
...

Spooky, yes. (sorry, I'm off for a week, in a holiday house without wifi :-) , so probably not so often online).
Have fun, Peter
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.    Richard Feynman

Online RERT

Monomorphic -

I said I'd have a crack at analysing data from some tap tests, and I've spent most of the afternoon fiddling with your mag tap.xlsx file.

I fitted the data from three sections of 2000 datapoints starting at 300, 429.9 and 549.9 seconds in. These are sections where the high frequency transients appear to have died off. Obviously those transients show that you don't actually have a pure damped SHM, but I'm just ignoring that...

The equation fitted is dx/dt+2a(dx/dt)+ωx=0, where x is the horizontal displacement from the neutral point of the torsion balance. ω is the natural frequency of the undamped pendulum, and a is a constant representing the degree of damping.

The three sections give ω=0.1910.003 and a=2.550.08. Because a>ω the roots of the characteristic equation are both real, indicating that the system is overdamped. The value of ω corresponds to a free oscillation period of the beam around 33 seconds, which seems vaguely plausible. Hopefully I have my definitions straight and haven't made an error...

The most notable feature the data is that the neutral point is clearly drifting down before the first tap, and the beam goes below the initial neutral point before the end.

The procedure I used was to estimate the initial positions and velocities of the beam from the data, and set ω and a to values which best fit the subsequent position of the beam by OLS using the Excel solver.

Now, armed with this equation I should be able to work out where the beam should be at the next tick, given its position and velocity now. Any anomaly from that position can be used to calculate an 'instantaneous' anomalous force (assumed constant over the tick).

If I can get a repeat of the tap test on the same test rig as the next measurement, I will do these calcs again and see if I can extract the instantaneous force. The purpose of this, BTW, is to see whether force onset is gradual or impulsive, and to to see how force varies with frequency during sweeps.

Offline WarpTech

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According to TT's spreadsheet, is your truncated cone  small diameter larger than the Shawyer cut-off diameter?

Yes, very much so. Cuttoff according to the spreadsheet is 2.053Ghz. I'm operating at 2.45Ghz. See surface currents in image below.

I just realized you have the antenna at the small end. In my theory, I am assuming the antenna is at the Big end. The energy and momentum flows from the antenna toward the small end, where it is dissipated and lost as heat, and the output of the antenna itself adds to the force, where the big end is leading and the small end is like a nozzle to focus the losses on the small plate.

With the antenna at the small end, it confounds the model, since both the source and the sink of momentum are at the "same" end and the big end is just a reflector. I know this is how Shawyer did it, but it confounds the experiment since the antenna output is going to make the small end lead, where the dissipation at the small end should make the big end lead. (without air current intervening) Therefore, IMO, I think you would get a greater force with the antenna at the big end, with the big end leading and as it is now, you have a Push-Me Pull-You.



« Last Edit: 02/17/2017 06:26 PM by WarpTech »

Offline Notsosureofit

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With the antenna at the small end, it confounds the model, since both the source and the sink of momentum are at the "same" end and the big end is just a reflector. I know this is how Shawyer did it, but it confounds the experiment since the antenna output is going to make the small end lead, where the dissipation at the small end should make the big end lead. (without air current intervening) Therefore, IMO, I think you would get a greater force with the antenna at the big end, with the big end leading and as it is now, you have a Push-Me Pull-You.

If it is acting as a Push-Me, Pull-You, you should expect a large change in impedance between the input and output.
« Last Edit: 02/17/2017 06:34 PM by Notsosureofit »

Offline WarpTech

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With the antenna at the small end, it confounds the model, since both the source and the sink of momentum are at the "same" end and the big end is just a reflector. I know this is how Shawyer did it, but it confounds the experiment since the antenna output is going to make the small end lead, where the dissipation at the small end should make the big end lead. (without air current intervening) Therefore, IMO, I think you would get a greater force with the antenna at the big end, with the big end leading and as it is now, you have a Push-Me Pull-You.

If it is acting as a Push-Me, Pull-You, you should expect a large change in impedance between the input and output.

The input is measured at 50 Ohms. What is the output you are referring to and how would it be measured? I can only envision it based on the power dissipation and heat generated.

Offline TheTraveller

Recent corro from Roger contained this breadcrumb:

Remember there are two forces at work simultaneously, one that I call thrust (small end to big end) and the opposite which I refer to as the reaction force. When the cavity is free to move, acceleration occurs in the direction of the reaction force. When the cavity stops, both forces cancel out. This is the only way Newtons laws are satisfied, and has been verified many times.

As an EmDrive thruster must be free to move / accelerate or the Reaction force generation stops, would not that occur when the torsion wire has absorbed all the torque a EmDrive thruster could generate and then the stored torque in the torsion wire drives the now stopped EmDrive in reverse, even though there is still power applied?

Ie initially in "Motor mode", then when stopped in "Idle mode" and then as it moves backward in "Generator mode" opposing the torsion wire torque driving it backward.

Spooky action on the torsion pendulum or just how a part of the operational characterists of an EmDrive thruster works?

As attached.
« Last Edit: 02/17/2017 07:08 PM by TheTraveller »
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Offline Notsosureofit

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With the antenna at the small end, it confounds the model, since both the source and the sink of momentum are at the "same" end and the big end is just a reflector. I know this is how Shawyer did it, but it confounds the experiment since the antenna output is going to make the small end lead, where the dissipation at the small end should make the big end lead. (without air current intervening) Therefore, IMO, I think you would get a greater force with the antenna at the big end, with the big end leading and as it is now, you have a Push-Me Pull-You.

If it is acting as a Push-Me, Pull-You, you should expect a large change in impedance between the input and output.

The input is measured at 50 Ohms. What is the output you are referring to and how would it be measured? I can only envision it based on the power dissipation and heat generated.

http://staff.ustc.edu.cn/~jlxie/lixue_appendix/AJP_pushmepullyouboat.pdf for instance.
One would have to guess at the characteristic impedance of the output medium and calculate the effect of the cavity acting as a transformer from the reported results.
« Last Edit: 02/17/2017 07:13 PM by Notsosureofit »

Offline Monomorphic

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I just realized you have the antenna at the small end. In my theory, I am assuming the antenna is at the Big end. The energy and momentum flows from the antenna toward the small end, where it is dissipated and lost as heat, and the output of the antenna itself adds to the force, where the big end is leading and the small end is like a nozzle to focus the losses on the small plate.

With the antenna at the small end, it confounds the model, since both the source and the sink of momentum are at the "same" end and the big end is just a reflector. I know this is how Shawyer did it, but it confounds the experiment since the antenna output is going to make the small end lead, where the dissipation at the small end should make the big end lead. (without air current intervening) Therefore, IMO, I think you would get a greater force with the antenna at the big end, with the big end leading and as it is now, you have a Push-Me Pull-You.


I do plan on mounting an antenna on the big end once I've done some testing with the current set-up. It is a simple matter to add another RF port to the big end and move the antenna.

Offline Rodal

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I just realized you have the antenna at the small end. In my theory, I am assuming the antenna is at the Big end. The energy and momentum flows from the antenna toward the small end, where it is dissipated and lost as heat, and the output of the antenna itself adds to the force, where the big end is leading and the small end is like a nozzle to focus the losses on the small plate.

With the antenna at the small end, it confounds the model, since both the source and the sink of momentum are at the "same" end and the big end is just a reflector. I know this is how Shawyer did it, but it confounds the experiment since the antenna output is going to make the small end lead, where the dissipation at the small end should make the big end lead. (without air current intervening) Therefore, IMO, I think you would get a greater force with the antenna at the big end, with the big end leading and as it is now, you have a Push-Me Pull-You.


I do plan on mounting an antenna on the big end once I've done some testing with the current set-up. It is a simple matter to add another RF port to the big end and move the antenna.
What is the experimentally measured period of rotational oscillations for your torsional pendulum (with the same EM Drive mass, wire and length of wire as for the force vs. time pictures)?

Thanks

Offline Monomorphic

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What is the experimentally measured period of rotational oscillations for your torsional pendulum (with the same EM Drive mass, wire and length of wire as for the force vs. time pictures)?

Dr. Rodal, the honest answer is I do not know yet. Dampening is still in flux, so I haven't performed a detailed analysis. I ran another tap test this morning, but was WAY over damped (attached). This is because the temperature dropped low last night and the lab space was fairly cold this morning. That meant the dampening oil was also colder and more viscous. I am making more adjustments to the dampening paddle tonight, and hope to run another tap test.
« Last Edit: 02/17/2017 10:12 PM by Monomorphic »

Offline otlski

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What is the experimentally measured period of rotational oscillations for your torsional pendulum (with the same EM Drive mass, wire and length of wire as for the force vs. time pictures)?

Dr. Rodal, the honest answer is I do not know yet. Dampening is still in flux, so I haven't performed a detailed analysis. I ran another tap test this morning, but was WAY over damped (attached). This is because the temperature dropped low last night and the lab space was fairly cold this morning. That meant the dampening oil was also colder and more viscous. I am making more adjustments to the dampening paddle tonight, and hope to run another tap test.

It would be useful to know the period both with and without oil damping. Without oil allows us to calculate the moment of inertia.

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