Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2107797 times)

Offline Notsosureofit

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FYI

Still bumbling along.  This is a shot at an integral form for a generalized cylindrical cavity where c and R are functions of the long axis.  Once you have del f, the thrust/photon and thrust are straightforward.

For:

A = (p/2*L)^2 and B = (X/2*pi)^2 where X = X[sub m,n](ie. TE) or X'[sub m,n](ie. TM)

and c and R are functions of z such that c = c(z) and R = R(z) then

(del f)*f[sub m,n,p]) = B*Int(0,L)[(c/R^2)*(dc/dz)-(c^2/R^3)*(dR/dz)]dz
                      + A*Int(0,L)[c*(dc/dz)]dz

Anyway, give it a look.  I'll be trying cases as time permits.

Thanks  (and watch for typos)


Offline frobnicat

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Rodal I need your expertise ;D

On the magnetic field maps given by Eagleworks simulations and from your exact solutions, is it correct to interpret that the heating power per unit area of frustum inner wall will depend locally as the square of the magnetic field magnitude ? Is the scalar intensity value map below enough to get the heating rate at each point or is the vector map required ? Will we have a smooth transition (in heating rate per unit area) between the PCB plate and cone in spite of the angle they make at the rim ?



Trying to get a more accurate view on displacements : the PCB plate can buckle by thermal expansion against a rigid rim, but the rim is itself heating and expanding, will try an axisymmetric simulation taking both into account + thermal gradient (across thickness) induced "warp".

Offline Mulletron

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Okay I'm going to use E field drive and sense probes (instead of loops) within the cavity placed at 1.36" from the large plate.

It seems to me that the connector should be at the small end. I'm kind of torn on this. It probably doesn't matter. Shawyer/Eagleworks have the connectors at the large end, so I will too.

There is a nifty calculator here to make it easy:
http://www.turnpoint.net/wireless/cantennahowto.html
http://www.lincomatic.com/wireless/homebrewant.html (more info)

Also some backgrounders for those who are interested:
http://www.radartutorial.eu/03.linetheory/tl11.en.html
http://www.maritime.org/doc/neets/mod11.pdf

This is also in agreement with the 15% of 9" cavity height from the large end which came out to 1.35", brought up here: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1331854#msg1331854

The length of the probe will be 1.21" or 31mm, based on a 1/4 wavelength of the desired frequency 2450mhz.

The type of connector will be an N-type female in the top picture, as opposed the one in the bottom picture. That way I only have to drill one hole instead of five per connector. The size of the center hole required for both is within 1/16" so I'm not going to bother with the 4 hole bulkhead connectors I got. I wanted to see them both before I decided on which one to use.

The connectors were purchased from here, I guess they sold out because they now say unavailable:
http://www.amazon.com/gp/product/B00OOF54QW/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B006Z95L8Q/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

I'm sure there are more on Amazon, but if not, I've purchased from these guys before and had a good experience:
http://www.fab-corp.com/home.php?cat=274



« Last Edit: 03/15/2015 01:12 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Star-Drive

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Okay I'm going to use E field drive and sense probes (instead of loops) within the cavity placed at 1.36" from the large plate.

It seems to me that the connector should be at the small end. I'm kind of torn on this. It probably doesn't matter. Shawyer/Eagleworks have the connectors at the large end, so I will too.

There is a nifty calculator here to make it easy:
http://www.turnpoint.net/wireless/cantennahowto.html
http://www.lincomatic.com/wireless/homebrewant.html (more info)

Also some backgrounders for those who are interested:
http://www.radartutorial.eu/03.linetheory/tl11.en.html
http://www.maritime.org/doc/neets/mod11.pdf

This is also in agreement with the 15% of 9" cavity height from the large end which came out to 1.35", brought up here: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1331854#msg1331854

The length of the probe will be 1.21" or 31mm, based on a 1/4 wavelength of the desired frequency 2450mhz.

The type of connector will be an N-type female in the top picture, as opposed the one in the bottom picture. That way I only have to drill one hole instead of five per connector. The size of the center hole required for both is within 1/16" so I'm not going to bother with the 4 hole bulkhead connectors I got. I wanted to see them both before I decided on which one to use.

The connectors were purchased from here, I guess they sold out because they now say unavailable:
http://www.amazon.com/gp/product/B00OOF54QW/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B006Z95L8Q/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

I'm sure there are more on Amazon, but if not, I've purchased from these guys before and had a good experience:
http://www.fab-corp.com/home.php?cat=274


Mulletron:

Dependent on the output power of your RF system, you might also consider using TNC connectors for your frustum RF power injection port.  SMA connectors are good to about 100W, TNC are good to 400W and Type-N connectors can go up to 1,000W dependent on its operating frequency.  As to their preferred location, that all depends on what frustum resonant mode you are interested in exciting and whether you want to drive it via an E-field whip or magnetic loop.  If you look at the Frank Davies frustum mode presentation already on this forum, you will observe that each resonant mode and frequency has strong E-field and B-fields locations and weaker locations and you want to drive it at one of stronger locations.

BTW, I've tried E-field whip antennas as the main RF input and I found that due to the high quality factors in these resonant system, you can literally burn off the tip of the whip antenna from the high E-fields created as the attached picture of the Cannae E-field injection antenna will attest when I drove it with ~80W at 932 MHz.  That is why I now use magnetic loops or side wall slots being driven by a waveguide feed.  I've also gone to B-field loops because I can rotate them and thus directly control the coupling by rotating the loop through 180 degrees. 

With an E-field probe you have to start long and trim the whip length to get a minimum VSWR.  And if you try a different lower frequency, you then have to go with a new longer whip antenna and start trimming again.  Loops can be just as fussy in their required OD, but you only end up with five or six loops of various diameters that can be used for most of the frustum resonances of interest. 

Best, Paul M.

Offline Rodal

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Rodal I need your expertise ;D

On the magnetic field maps given by Eagleworks simulations and from your exact solutions, is it correct to interpret that the heating power per unit area of frustum inner wall will depend locally as the square of the magnetic field magnitude ? Is the scalar intensity value map below enough to get the heating rate at each point or is the vector map required ? Will we have a smooth transition (in heating rate per unit area) between the PCB plate and cone in spite of the angle they make at the rim ?



Trying to get a more accurate view on displacements : the PCB plate can buckle by thermal expansion against a rigid rim, but the rim is itself heating and expanding, will try an axisymmetric simulation taking both into account + thermal gradient (across thickness) induced "warp".

1) Paul March kindly supplied both the COMSOL Finite Element dissipated heat (W/m^2) per unit area (the finite element model takes into account geometrical changes like the "angle" you are concerned with) as well as the NASA Eagleworks thermal IR camera measurements:



so you don't need to rely solely on the magnetic field

2) Assuming an adiabatic process, the volumetric power dissipation Pdissipated in the material due to the applied magnetic field should be:

 Pdissipated = Pi*f*Chi"*(B^2)/(muo*(mur^2)) =  Pi*f*Chi"*(H^2)*muo

f=frequency (Hz)
Chi"= out-of-phase susceptibility (complex component of the susceptibility) of the material
mu = magnetic permeability = muo*mur
mur = relative permeability of the material
B = magnitude of induction = mu* H
H = magnitude of magnetic field strength

So yes, assuming an adiabatic process, the volumetric power dissipation goes like the square of the magnitude of the magnetic field.

3) The magnitude of the total vector resultant matters (one needs to take into account the resultant of the vector components, which has been done in the plot supplied by Paul March).  The direction doesn't matter.

4) Questions like "Will we have a smooth transition (in heating rate per unit area) between the PCB plate and cone in spite of the angle they make at the rim ?" and other statements in this and the other posts I can't follow without seeing the unstated equations, assumptions and values, you use for your models.  For example, I don't understand why you are concerned by "a smooth transition" due to the geometrical angle when we have discontinuous material properties between the epoxy and the copper) :)
« Last Edit: 03/15/2015 08:09 PM by Rodal »

Offline Mulletron

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I gotta say it is an honor receiving Q-thruster advice from the Paul March. I plan using no more than 2 watts. I like N-type connectors though, because they're good for low and high power. So if I ever get a hankering to try high power later (like tapping off the waveguide of a microwave like this guy http://gbppr.dyndns.org/mil/emp3/index.html), the holes for the larger connector will already be there. I'd prefer to keep it safe and just use low power.

The middle pic in this post was extremely helpful and thanks!
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1327467#msg1327467

A tip I wanted to make sure I pass along for any further DIYers out there. Thin copper and drill bits don't mix. A drill bit will ruin your day if you don't step it up slowly. I used the reamers in the pics below for most of the work.

I'm still waiting on word back from the guy on Ebay to list his "microwave resonant cavity" for research. He makes these things usually, but I was lucky enough to get him to build a custom job and he did a good job:
http://www.ebay.com/sch/1952rickey/m.html?item=121586024858&rt=nc&_trksid=p2047675.l2562

« Last Edit: 03/15/2015 03:27 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline frobnicat

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Rodal I need your expertise ;D

...

1) Paul March kindly supplied both the COMSOL Finite Element dissipated heat (W/m^2) per unit area (the finite element model takes into account geometrical changes like the "angle" you are concerned with) as well as the NASA Eagleworks thermal IR camera measurements:
...
so you don't need to rely solely on the magnetic field

Yes, this is a very informative instantaneous map of temperature, but I wanted to reconstruct the dynamic (transients) and also have the gradients through thickness. Preliminary simulations I am doing show the gradients through thickness are negligible for the cone part since copper is such good thermal conductor but through the PCB plate at any time there easily can be more than 1°C difference between the copper side and the other side. This will induce stress in flexion (known as "bow" or "warp" in PCB literature) and tend to make the PCB flex toward the copper (inward). Magnitude of that effect relative to buckling (in plane PCB expansion relative to rim support) I'm still struggling to assert, especially if the PCB as even a very modest inward warp to start with (which is a concern for single sided boards) like a few 10s of microns at belly.
Why I wanted to start again from the primary heat flux dissipated within the skin depth copper side, even if it is with far lower numerical tools than provided by Comsol results. I wish Eagleworks had added a deformation study from the very accurate thermal maps.

Quote
2) Assuming an adiabatic process, the volumetric power dissipation Pdissipated in the material due to the applied magnetic field should be:

 Pdissipated = Pi*f*Chi"*(B^2)/(mu*mur) =  Pi*f*Chi"*(H^2)*muo

f=frequency (Hz)
Chi"= out-of-phase susceptibility (complex component of the susceptibility) of the material
mur = relative permeability of the material
B = magnitude of induction = permeability * H
H = magnitude of magnetic field strength

So yes, assuming an adiabatic process, the volumetric power dissipation goes like the square of the magnitude of the magnetic field.

3) The magnitude of the total vector resultant matters (one needs to take into account the resultant of the vector components, which has been done in the plot supplied by Paul March).  The direction doesn't matter.

Nice, so we do have access to the primary heat flux at each point. Thanks a lot.

Quote
4) Questions like "Will we have a smooth transition (in heating rate per unit area) between the PCB plate and cone in spite of the angle they make at the rim ?" and other statements in this and the other posts I can't follow without seeing the unstated equations, assumptions and values, you use for your models.  For example, I don't understand why you are concerned by "a smooth transition" due to the geometrical angle when we have discontinuous material properties between the epoxy and the copper) :)

Yes there is certainly a huge discontinuity in thermal characteristics of the walls here, I just wanted to know the discontinuity in terms of heat flux due to vector orientation relative to normal of surface elements. Since the maps provided by Paul March take the vector resultant into account the answer to 3) makes 4) not relevant. For my model I wasn't specifically concerned by the transition in power flux being smooth or not, just trying to interpret correctly the plots. At the moment I'm running an axisymmetric model for thermal conduction (in materials) and thermal radiation (in vacuum) comprising the big end PCB plate + portion of cone, but have not yet tools for deformations induced by the thermal and coefficient of expansion gradients.

For the rest I don't see how I could make the statements more clear (more synthetic yes probably), I posted a number of equations showing how a Z tilted pendulum would quantitatively react to a displacement of centre of mass, with shifts toward small end of frustum giving higher LDS readings and not the opposite. The tilt is not known precisely, but it could be reconstructed, if it wasn't for the apparent stiffness/vertical scale issue. I've shown with simple enough equations that there is a very poorly characterised core parameter in the system, by more than an order of magnitude. With significant thermally induced centre of mass displacements (with time constants compatible with those of the rise and fall of the signal) this poorly explained core parameter is not just a serious concern but becomes a major issue. That I explain that well enough or not to be convincing don't change the fact. I know this latest statement is not convincing or "helpful" by itself, just a feeling. But the equations are here. There is just one lacking (the exact ratio LDS_shift/CoMposition_shift) that needs the issue of vertical scale to be resolved. That there is an issue with the apparent stiffness/vertical scale is for me beyond doubt.

Offline Rodal

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....

For the rest I don't see how I could make the statements more clear (more synthetic yes probably)...
Speaking personally, it would be clearer if you would state the equations that you are using for your posted calculations, defining the variables in the equations, and the values of the parameters you used to arrive at a solution. (e.g. what were the material property inputs you used and the equations you used for the personal code thermal calculations?)
« Last Edit: 03/15/2015 07:33 PM by Rodal »

Offline Mulletron

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Ok so the connectors are cut and soldered in. I'm going to leave it this way unless an issue comes up that prompts change. I'm not thrilled about having that nut inside the frustum. I saw pics from Eagleworks where they have the nut inside their frustum here:
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1331854#msg1331854

So maybe it is fine. I like to nuke things.

If it becomes a problem, I'll solder in place the outside nut (which I'm using as a spacer to compensate for the thin frustum) in place and use it to hold the connector in place, while at the same time ditching the inside nut, allowing a smoother presentation on the inside of the cavity.

The whip antenna was salvaged from the 12ga ground wire from a 4 wire Romex cable I had laying around from an old project. The 12ga wire is a perfect fit in the solder cup. Like a glove. I straightened out the wire in a vise, which had a groove in one side of the clamps. A couple rotations and the wires were straight.

I don't want to upload hundreds of pics so most of the build log will be here:
https://drive.google.com/folderview?id=0B4PCfHCM1KYoTXhSUTd5ZDN2WnM&usp=sharing

I'm taking lots of pics to serve as pointers for other DIYers to learn from my mistakes and successes.
« Last Edit: 03/15/2015 07:27 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

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Yes, this is a very informative instantaneous map of temperature, but I wanted to reconstruct the dynamic (transients) and also have the gradients through thickness.....
Paul March gave us several plots, including:

1) Calculated dissipated power W/m^2 vs. location
2) Measured temperature vs location
3) Calculated Magnetic field vs location

The fact is that Paul March gave us the calculated dissipated power W/m^2 vs. location.  In your prior post you referred to Paul's data for the calculated magnetic field, and in this post you acknowledge the measured temperature.

....
Why I wanted to start again from the primary heat flux dissipated within the skin depth copper side, even if it is with far lower numerical tools than provided by Comsol results. I wish Eagleworks had added a deformation study from the very accurate thermal maps.
EDIT (hat tip to @frobnicat): To be precise, Eagleworks did not provide COMSOL calculations (to my knowledge) of a thermal map (temperature vs. location).  What Eagleworks provided are (COMSOL Finite Element) calculations for the dissipated power per unit area (in units of power per surface area: Watt/m^2) surface losses throughout the whole 3-Dimensional surface (both the large and small diameter ends as well as the lateral round conical surface).  And it is the volumetric power dissipation that goes like the square of the magnitude of the magnetic field, which was your question.  So, Paul March had already given you the elements to answer your question: both the magnetic field and the power dissipation density.

The thermal map is a result of IR thermal measurements.


« Last Edit: 03/15/2015 10:21 PM by Rodal »

Offline Rodal

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... I'm still struggling to assert, especially if the PCB as even a very modest inward warp to start with (which is a concern for single sided boards) like a few 10s of microns at belly.
...
Since the bending deformation of the end plate (due to a thermal gradient through its thickness, referred to as "oil canning" in the picture below) is inwards, and you had arrived at the conclusion that such an inward deformation produces a force that is in the opposite direction to the measured force , why are you so interested in performing this calculation?

If your purpose is to show that the actual EM Drive force (due to the Quantum Vacuum or whatever else may make it work in space?) is larger than the measured force, then I  lost track of the discussion somewhere because I recall you stating that you wanted to show the opposite: that the measured force was an artifact.

?

« Last Edit: 03/15/2015 07:59 PM by Rodal »

Offline frobnicat

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....

For the rest I don't see how I could make the statements more clear (more synthetic yes probably)...
Speaking personally, it would be clearer if you would state the equations that you are using for your posted calculations, defining the variables in the equations, and the values of the parameters you used to arrive at a solution. (e.g. what were the material property inputs you used and the equations you used for the personal code thermal calculations?)

By "the rest" I was speaking of the previous post where I defined axis conventions, tilt, displacements... dispersed in a few post, so a synthesis might be needed, agree on that.

For the later results (thermal conduction), I'm not expecting anyone give too much credit in the accuracy of a personal simulation code, I did check for stability and consistency at equilibrium (it's ok) but this was just a basis of discussion, not presented as definitive proof. I don't have know how using more serious simulation frameworks.  The equations are those of thermal transfers proportional to temperature differences and conductions, and Stefan-Boltzmann for radiation (assuming a bath at 20°). For information those are the values for the materials (Tp = Through plane, Ip = In plane) :

COPPER
density          8960 kg/m^3
specHeat          385 J/kg/K
conductionTp      385 W/m/K
conductionIp      385 W/m/K
expansionTp   16.6e-6 m/m/K
expansionIp   16.6e-6 m/m/K
emissivity       0.05 coef<1

FR4
density          1850 kg/m^3
specHeat          600 J/kg/K
conductionTp      0.3 W/m/K
conductionIp     0.85 W/m/K
expansionTp   70.0e-6 m/m/K
expansionIp   13.0e-6 m/m/K
emissivity        0.9 coef<1


Offline frobnicat

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The fact is that Paul March gave us the calculated dissipated power W/m^2 vs. location.  In your prior post you referred to Paul's data for the calculated magnetic field, and in this post you acknowledge the measured temperature.

....
Why I wanted to start again from the primary heat flux dissipated within the skin depth copper side, even if it is with far lower numerical tools than provided by Comsol results. I wish Eagleworks had added a deformation study from the very accurate thermal maps.
To be precise, Eagleworks did not provide COMSOL calculations (to my knowledge) of a thermal map (temperature vs. location).  What Eagleworks provided are (COMSOL Finite Element) calculations for the dissipated power per unit area (in units of power per surface area: Watt/m^2) surface losses throughout the whole 3-Dimensional surface (both the large and small diameter ends as well as the lateral round conical surface).  And it is the volumetric power dissipation that goes like the square of the magnitude of the magnetic field, which was your question.  So, Paul March had already given you the elements to answer your question: both the magnetic field and the power dissipation density.

The thermal map is a result of IR thermal measurements.


Yes, this is exactly what I was looking for (dissipated power by unit area at each location). The document Thermal Analysis 1.pdf (from this post of Star-Drive) do provide COMSOL calculations of a thermal map (temperature vs. location) and I was referring to those about "the very accurate thermal maps".

I share your substantiated opinion that Eagleworks team should definitely substitute the PCB end caps by a plain copper plate, at least for a test or two and see how the results change or not (all other conditions being equal as most as possible).

Offline ThinkerX

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Ok, despite my best efforts (which, admittedly are rather feeble), I can no longer tell what 'frobnicat' is attempting to accomplish.  Is he arguing that all of the 'thrust' produced by this device is some sort of thermal artefact?   From what I can tell, the goalposts seem to have moved at least once.

Executive summary time, please.

Offline frobnicat

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... I'm still struggling to assert, especially if the PCB as even a very modest inward warp to start with (which is a concern for single sided boards) like a few 10s of microns at belly.
...
Since the bending deformation of the end plate (due to a thermal gradient through its thickness, referred to as "oil canning" in the picture below) is inwards, and you had arrived at the conclusion that such an inward deformation produces a force that is in the opposite direction to the measured force , why are you so interested in performing this calculation?

You complain that my hypothesis and variables and equations are not clearly put, but do you read me seriously ? A movement to the left of a part of mass M will make a force to the right as recoil : F(t)=-M d˛CoMPosition(t)/dt˛. Measuring F and ComPosition on same oriented Y axis. Shift to the left (Y-) Force to the right (Y+). Is it clear enough ? Such F(t) is small, very small, even by µN standards. It depends on the second derivative of the shift (wrt time).

Now, if we have the right to go past those negligible recoil effects :
A shift in CoMPosition to the left (Y-) will change the equilibrium rest position in such a way that the LDS distance will increase (Y-). A slow inward deformation don't produces a force  (ah ah, it does, but is too small to be significant). I'm no longer talking of force. I'm talking change of rest equilibrium position (by rest equilibrium I mean : the stable position when there is no force). This effect on LDS reading is not dependent on second nor first derivative of the shift (wrt time).

This was explained here, what is not clear ? Now you can object that in this model I ignored the restoring torque of the flexure bearings. This stiffness will lower the relative magnitude of the effect but not 0 it. I'm waiting for a proper characterization of the pendulum before I can give such magnitude, so far, at 1µm LDS reading per 29.1µN cal. pulse + 4.5s oscillation in charts (when underdamped) the pendulum is not properly characterised, there is a contradiction in the LDS readings data in µm and other known parameters.



Edit : the three bottom charts are roughly to scale concerning the placement of CoMs along the arm (X axis) from data provided by Paul March. The deformations and movements are obviously greatly exaggerated for illustration purpose. The charts seems to imply that the test article CoM shift would be due to frustum copper cone part expansion, but any other significant thermal displacement would play an equivalent role (actually the lengthening of cone may play a minor contribution relative to lighter but "amplified" buckling/warping effect at the big end PCB plate).

Quote
If your purpose is to show that the actual EM Drive force (due to the Quantum Vacuum or whatever else may make it work in space?) is larger than the measured force, then I  lost track of the discussion somewhere because I recall you stating that you wanted to show the opposite: that the measured force was an artifact.

?

I wanted to show that the measured "force" (LDS reading really) might not be a force at all, but a change in equilibrium rest position, as per the diagram showing how the equilibrium rest position is different depending on test article CoM position is here or there along Y axis. No derivative or second derivative implied. CoM sits here, LDS shows a reading, CoM sits there, LDS shows another reading. CoM shifts, LDS follows. Same direction, CoM shifts to left, LDS reading rises.
« Last Edit: 03/16/2015 12:04 AM by frobnicat »

Offline Rodal

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....

For the later results (thermal conduction), I'm not expecting anyone give too much credit in the accuracy of a personal simulation code,....
FR4
density          1850 kg/m^3
specHeat          600 J/kg/K
...

It is not a question of giving personal credit, but my understanding of your posting such calculations is to check whether the experimental results are an artifact or whether they are due to a real thrust that can work for outer space propulsion.  If you don't post the equations and the material properties you use, then how can the reader ascertain how to evaluate what you post?

To give one example, we see now that you used a value of 600 J/kg/K for the specific heat of FR-4 (no reference as to where this came from).  However, Rebecka Domeij B¨ackryd at LINK¨OPING University (Sweden) used a value twice as high: 1200 J/kg/K (see page 14 of http://www.diva-portal.org/smash/get/diva2:18631/FULLTEXT01.pdf )

Offline frobnicat

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....

For the later results (thermal conduction), I'm not expecting anyone give too much credit in the accuracy of a personal simulation code,....
FR4
density          1850 kg/m^3
specHeat          600 J/kg/K
...

It is not a question of giving personal credit, but my understanding of your posting such calculations is to check whether the experimental results are an artifact or whether they are due to a real thrust that can work for outer space propulsion.  If you don't post the equations and the material properties you use, then how can the reader ascertain how to evaluate what you post?

To give one example, we see now that you used a value of 600 J/kg/K for the specific heat of FR-4 (no reference as to where this came from).  However, Rebecka Domeij B¨ackryd at LINK¨OPING University (Sweden) used a value twice as high: 1200 J/kg/K (see page 14 of http://www.diva-portal.org/smash/get/diva2:18631/FULLTEXT01.pdf )

sigh
note taken
« Last Edit: 03/15/2015 09:46 PM by frobnicat »

Offline Rodal

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You complain that my hypothesis and variables and equations are not clearly put, but do you read me seriously ?...
I just stated that I personally have a hard time following your train of thought, and that I personally would prefer to see more equations.  You could justifiably answer that it is my fault because of my lack of reading comprehension.  I don't recall me stating that it was your fault, I actually recognized that it is probably my fault because in physics and technical science I can much better understand equations than words, particularly about things like forces (I surely don't understand Roger Shawyer's discussion of forces in the EM Drive either).



Example, of things I have a problem understanding  (my fault, probably the majority of other readers can understand you perfectly well):

Quote
A movement to the left of a part of mass M will make a force to the right as recoil : F(t)=-M d˛CoMPosition(t)/dt˛. "  OK, so the force is to the right and it is opposite to the measured force


..."Such F(t) is small, very small, even by µN standards. It depends on the second derivative of the shift (wrt time).

===> So now I understand from this last sentence that you think that the "recoil" force was actually negligible (close to zero).  I had the (incorrect) understanding that the reason why you were discussing recoil was because you thought it was IMPORTANT. (I try to only argue about things that I think are important to me and I incorrectly projected that :)  ).

Quote
Now, if we have the right to go past those negligible recoil effects :
... A slow inward deformation don't produces a force  (ah ah, it does, but is too small to be significant). I'm no longer talking of force. I'm talking change of rest equilibrium position (by rest equilibrium I mean : the stable position when there is no force)

===> So you are not talking of forces.  Sorry, I didn't understand that prior to your latest posting. :)
« Last Edit: 03/15/2015 10:15 PM by Rodal »

Offline frobnicat

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You complain that my hypothesis and variables and equations are not clearly put, but do you read me seriously ?...
I just stated that I personally have a hard time following your train of thought, and that I personally would prefer to see more equations.  You could justifiably answer that it is my fault because of my lack of reading comprehension.  I don't recall me stating that it was your fault, I actually recognized that it is probably my fault because in physics and technical science I can much better understand equations than words.

Sorry mister Rodal, my english is chaotic somehow and I really wish we had some telepathy of concepts at hand. Best.

Offline Rodal

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I wanted to show that the measured "force" (LDS reading really) might not be a force at all, but a change in equilibrium rest position, as per the diagram showing how the equilibrium rest position is different depending on test article CoM position...
Sorry again for not recalling your prior posts and needing a brief summary.

QUESTION1: have you calculated the change in Center Of Mass position for these different cases?  (yes or no ?)

 if your answer to QUESTION1 is no, stop reading.

 if your answer to QUESTION1 is yes, then,

QUESTION2: do your calculations for the change in center of mass position give a displacement that is close to the displacement vs. time measurements at NASA Eagleworks?

« Last Edit: 03/15/2015 10:31 PM by Rodal »

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