Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2165800 times)

Offline DIYFAN

  • Member
  • Posts: 48
  • Liked: 28
  • Likes Given: 149
Looking over the last several posts, I see absolutely nothing related to space flight applications.  All I see is more of exactly what got the previous version of this thread to disappear for a while.

I would respectfully disagree.  I find the discussion both highly pertinent to possible space flight applications and quite thought provoking.  We must not lose the forest for the trees, but at the same time, it is difficult to comprehend the forest without the trees.

Offline savuporo

  • Senior Member
  • *****
  • Posts: 5155
  • Liked: 975
  • Likes Given: 345
None of these experiments have demonstrated a linear acceleration: all of them have measured rotational accelerations.  None of the EM Drives have been tested in a vacuum.  None of the measured forces are high enough to levitate the drive.
Forget about levitation. I havent read much or anything about it, but are the forces even in the same ballpark as existing magnetic torquer rods for cubesats ? If yes, in theory this could assist with attitude control in deep space, at least for desaturation.

Anyone ? Anyone ?

I mean, actual spaceflight application. Desaturation spends fuel. Can we get a propellantless desaturation device, with main attitude control provided by reaction wheels ?

Again, from the claimed experimental setups, are the reported angular momentums even on a scale where they could turn a cubesat - even if it takes a long time to do so ? Its not like torquer rods are fast or anything, but they only work within earths magnetic field.

And if it cannot turn a cubesat, the entire thing is no better than Steorn Orbo, is it ?
« Last Edit: 01/05/2015 02:45 AM by savuporo »
Orion - the first and only manned not-too-deep-space craft

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
....

Beyond unorthodox pseudo-forces orientation conventions, this "dynamic environment" condition seems quite problematic and ill defined. Ignoring theoretical musings, Shawyer makes 3 phenomenological predictions :
....
- That a horizontal EM thruster restrained from accelerating horizontally (through an opposing spring) will record no thrust, page 3 figure 3 "Because the thruster is at rest, no force will be measured on the load cell"
....

A spring (with finite stiffness) attached to a wall NEVER prevents an object attached to it from accelerating, thus Shawyer's statement is not well stated or it is incorrect.  Only an infinitely stiff (rigid) spring would prevent an object from accelerating.  Otherwise (for finite spring constant) the system will just obey a solution of the second order differential equation:  m d^2x/dt^2 +c dx/dt +  k x = F. 

If the displacement is a function of time, such that the second order derivative of the displacement with respect to time is not zero, there is an acceleration a = d^2x/dt^2 =( F - c dx/dt -  k x )/m  .   In words: the acceleration equals the applied force minus the viscous force, minus the spring force, all divided by the mass. 

If the displacement is not a function of time, we have simply (the "steady-state" solution) F=k*x (force=springConstant*displacement)

In the NASA Eagleworks tests of the truncated cone:

1) The truncated cone EM thruster was restrained by the torsional spring constant of the torsional pendulum used for measurement.  The torsional spring constant effectively acts like a spring attached to a wall (the difference being that in the NASA Eagleworks test we have a torsional pendulum where the EM Drive performs a rotation instead of a rectilinear motion)

2) The truncated cone EM thruster was initially at rest (prior to power input).

3) A time-varying displacement (effectively due to a rotation around the torsional axis) was recorded and thus a force was calculated by NASA Eagleworks using the known constants of the system.

4) We have verified this: we modeled NASA Eagleworks torsional pendulum, and furthermore analyzed the data using Fourier Transforms to obtain the Power Spectral Density and the Autocorrelation of the response.

Thus:

Shawyer's statement "That a horizontal EM thruster restrained from accelerating horizontally (through an opposing spring) will record no thrust" in http://www.emdrive.com/EmDriveForceMeasurement.pdf is not well stated or it is incorrect, as shown, for example, by the experiments carried out at NASA Eagleworks.

« Last Edit: 01/05/2015 07:39 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
None of these experiments have demonstrated a linear acceleration: all of them have measured rotational accelerations.  None of the EM Drives have been tested in a vacuum.  None of the measured forces are high enough to levitate the drive.
Forget about levitation. I havent read much or anything about it, but are the forces even in the same ballpark as existing magnetic torquer rods for cubesats ? If yes, in theory this could assist with attitude control in deep space, at least for desaturation.

Anyone ? Anyone ?

I mean, actual spaceflight application. Desaturation spends fuel. Can we get a propellantless desaturation device, with main attitude control provided by reaction wheels ?

...

As an example you can use for calculations, Shawyer reported (for his "Shawyer Demo") a measured force = 0.1023 Newtons (1/10th of a Newton) for a power input of 421 watts.

NASA Eagleworks (Brady et.al) reported (for the TE mode of the truncated cone) a measured force = 0.00005541 Newtons (55.41 MicroNewtons) for a power input of 2.6 watts.
« Last Edit: 01/05/2015 05:40 PM by Rodal »

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1367
I thought I would make up a summary of the dispersion relation approach, as I keep

doing this in bits and pieces.

1. The initial question was:

  In General Relativity (GR), if an RF cavity subject to an accelerating frame of

reference (AFR) displays asymmetric frequency dispersion, will an asymmetric RF

cavity which exhibits wavelength dispersion generate an accelerating frame of

reference.

2. It turned out that the asymmetric cavity dispersion relation is easily solved

for an AFR in which the wavelength dispersion dissapears, being replaced by a

frequency dispersed Doppler pair.  Energy is conserved.

g = (X[subm,n])^2*(c/4*pi^2)*lambda^2*((1/a^2)-(1/b^2))

where a anb b are the end plate radii and the X are the Bessel function zeros.

X[subm,n] = m-th root of dJ[subn](x)/dx = 0

[1,0]=3.83, [1,1]=1.84, [1,2]=3.05, [2,0]=7.02, [2,1]=5.33, [2,2]=8.54, [3,0]

=10.17, etc.

Lambda < cutoff wavelength.

Lambda is the free space wavelength c/f.

giving thrust per photon:

T = (X[subm,n])^2*(h/4*pi^2)*lambda*((1/a^2)-(1/b^2))


3. The surprise was that the force "on the photons" T, which would be required to

maintain that acceleration closely matched the experimental forces reported for

these cavities. The difference from other calculations is that there is a term

dependent on the particular mode of the cavity, (X[subm,n])^2, not just the area

of the end plates.


T = P*Q*(X[subm,n])^2*(1/c*4*pi^2)*lambda^2*((1/a^2)-(1/b^2))

TM211 T=9.84e-5 vs 9.12e-5 P=16.9 Q=7320
TM211 T=2.39e-4 vs 5.01e-5 P=16.7 Q=18100
TE012 T=1.32e-4 vs 5.54e-5 P=2.6  Q=22000


4. So where do things stand?

If the experimental forces are real and repeatable then since the acceleration of

the "Doppler" frame is considered the "Gravitational Potential" in GR.  The

corresponding term in the rest frame could only be an "Electromagnetic Potential",

calculated from the dispersion relation of the cavity.

That is to say, in GR, there is no valid equation here without introducing a cross

term between gravity and electromagnetism.  So, new physics would be required.

The Sachs-Schwebel "quaternion" formulation of GR has a cross term which "looks

like" it might fit, but it's hard for me to evaluate.  There is no shortage of

other theoretical attempts.


5. Momentum:

Conservation of momentum would have to be satisfied with the cross term.  The

suggestion from the experimental results (assuming they are real), that the

required momentum transfer is the same (or nearly the same) as that available from

the rest frame photons, implies that the cross term contains a field of very high

energy density compared to that of the photons. (to "push off" ?)

   


Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
I thought I would make up a summary of the dispersion relation approach, as I keep doing this in bits and pieces.
....

Thanks for the summary, much appreciated.

Quote from: Notsosureofit
The difference from other calculations is that there is a term  dependent on the particular mode of the cavity, (X[subm,n])^2, not just the area of the end plates.

Indeed! It is very impressive that not only your calculations are not that far from actual results but that your theory correctly predicts mode dependence and that the magnitude of the mode dependence corresponds with experimental results: the Transverse Electric TE012 mode produces much more [thrust force/input power] than the Transverse Magnetic TM211 mode , which was confirmed by the NASA Eagleworks experiments!  Neither the Shawyer nor the simplified McCulloch equations show this mode-dependence.
« Last Edit: 01/05/2015 06:41 PM by Rodal »

Offline RotoSequence

  • Full Member
  • ****
  • Posts: 777
  • Liked: 572
  • Likes Given: 780
I got some help making those equations look pretty with LaTeX, but I'm not sure it's rendered correctly. Are these accurate?

EDIT: Formulas were rendered inaccurately, and have been unlinked.

Thrust per photon:
http://i.imgur.com/V24BnsY.png
\mathrm T = \left( \mathrm X _{m,n} \right) ^2 \left( \frac{\hslash}{4} \pi ^2 \right) \lambda \left( \frac{1}{a^2} - \frac{1}{b^2} \right)

Force on the photons:
http://i.imgur.com/YvP9Zj9.png
\mathrm{T = P} \mathbb Q \left( \mathrm X_{m,n} \right) ^2  \left( \frac{1}{\mathrm{c}} 4 \pi ^2 \right) \lambda^2  \left( \frac{1}{a^2} - \frac{1}{b^2} \right)

« Last Edit: 01/06/2015 02:28 AM by RotoSequence »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
I got some help making those equations look pretty with LaTeX, but I'm not sure it's rendered correctly. Are these accurate?

Thrust per photon:

\mathrm T = \left( \mathrm X _{m,n} \right) ^2 \left( \frac{\hslash}{4} \pi ^2 \right) \lambda \left( \frac{1}{a^2} - \frac{1}{b^2} \right)

Force on the photons:

\mathrm{T = P} \mathbb Q \left( \mathrm X_{m,n} \right) ^2  \left( \frac{1}{\mathrm{c}} 4 \pi ^2 \right) \lambda^2  \left( \frac{1}{a^2} - \frac{1}{b^2} \right)

@RotoSequence: thank you for putting this in Latex.



@Notsosureofit:  did you mean to use the "reduced Planck constant", also called "Dirac constant"  hbar as in the Latex equations above or did you mean to use the Planck constant h as per your post ?

where

 h =  hbar * 2 * Pi

Given the de Broglie wavelength λ of a photon and the speed of light c, the energy E of the photon is
 
E = h c / λ = hbar * 2 * Pi * c / λ

It seems to me that you meant

1) to use h (instead of hbar in the Latex equation)

2) the factors of (Pi^2) in the first Latex equation and 4 Pi^2 in the 2nd Latex equation are in an incorrect position: the factors should be  (h/(4 Pi^2)) in the first equation and  (1/(c 4 Pi^2)) in the second equation

Please check, thanks
« Last Edit: 01/06/2015 01:58 AM by Rodal »

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1367
g = (X[subm,n])^2*(c/(4*pi^2))*lambda^2*((1/a^2)-(1/b^2))

T = (X[subm,n])^2*(h/(4*pi^2))*lambda*((1/a^2)-(1/b^2))

T = P*Q*(X[subm,n])^2*(1/(c*4*pi^2))*lambda^2*((1/a^2)-(1/b^2))

I'm not where I can double check, but I usually use h and "My Dear Aunt Sally".

Probably should call the last one NT...
« Last Edit: 01/06/2015 01:49 AM by Notsosureofit »

Offline RotoSequence

  • Full Member
  • ****
  • Posts: 777
  • Liked: 572
  • Likes Given: 780
Thrust per photon, with Planck's constant instead of the reduced constant: http://i.imgur.com/Lm9OVYD.png

EDIT: The original image has been unlinked because the formula is rendered inaccurately.
« Last Edit: 01/06/2015 02:27 AM by RotoSequence »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
Thrust per photon, with Planck's constant instead of the reduced constant:



I think that the factors of (Pi^2) in the first Latex equation and 4 Pi^2 in the 2nd Latex equation are in an incorrect position (they should be in the denominator instead of the numerator): the factors should be  (h/(4 Pi^2)) in the first equation and  (1/(c 4 Pi^2)) in the second equation.
« Last Edit: 01/06/2015 02:01 AM by Rodal »

Offline RotoSequence

  • Full Member
  • ****
  • Posts: 777
  • Liked: 572
  • Likes Given: 780
I think that the factors of (Pi^2) in the first Latex equation and 4 Pi^2 in the 2nd Latex equation are in an incorrect position (they should be in the denominator instead of the numerator): the factors should be  (h/(4 Pi^2)) in the first equation and  (1/(c 4 Pi^2)) in the second equation.

Hmm. Are you sure? Oh well, here they are just the same:

EDIT: Added NotSoSureOfIt's third equation to the list:







Old versions:

Changed T to NT http://i.imgur.com/kBUnXiA.png
http://i.imgur.com/NjgzBtl.png
« Last Edit: 01/06/2015 03:39 AM by RotoSequence »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
I think that the factors of (Pi^2) in the first Latex equation and 4 Pi^2 in the 2nd Latex equation are in an incorrect position (they should be in the denominator instead of the numerator): the factors should be  (h/(4 Pi^2)) in the first equation and  (1/(c 4 Pi^2)) in the second equation.

Hmm. Are you sure? Oh well, here they are just the same:





Yes, thanks.  That's what I think.  But these are @Notsosureofit equations, hopefully he can double check them and see whether he agrees  :)

PS: I agree with Notsosureofit, the second equation would better read NT, where "N" stands for the thrust of all the photons, instead of the thrust of a single photon "T".
« Last Edit: 01/06/2015 02:13 AM by Rodal »

Offline RotoSequence

  • Full Member
  • ****
  • Posts: 777
  • Liked: 572
  • Likes Given: 780
PS: I agree with Notsosureofit, the second equation would better read NT, where "N" stands for the thrust of all the photons, instead of the thrust of a single photon "T".

Edited :)

EDIT: And because my friend who showed me LaTeX insists, c4 is becoming 4c ;)

Also added Notsosureofit's third equation, hopefully without error!

« Last Edit: 01/06/2015 03:40 AM by RotoSequence »

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 700
  • Likes Given: 728
Guys, Guys......I stopped reading some time ago.....now we are into the 2nd thread.

Time to "let it go"........prove it one way or another.   The energy spent back and forth could have been put into a cad file, exported into STEP or IGES format by now....(someone please do it)

Then maybe if time permits i'll print out a test model.

Someone then talk maybe to Nanoracks, and lets get it tested. :)
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1367
Guys, Guys......I stopped reading some time ago.....now we are into the 2nd thread.

Time to "let it go"........prove it one way or another.   The energy spent back and forth could have been put into a cad file, exported into STEP or IGES format by now....(someone please do it)

Then maybe if time permits i'll print out a test model.

Someone then talk maybe to Nanoracks, and lets get it tested. :)

What are STEP and IGES ?

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
Guys, Guys......I stopped reading some time ago.....now we are into the 2nd thread.

Time to "let it go"........prove it one way or another.   The energy spent back and forth could have been put into a cad file, exported into STEP or IGES format by now....(someone please do it)

Then maybe if time permits i'll print out a test model.

Someone then talk maybe to Nanoracks, and lets get it tested. :)

What are STEP and IGES ?

They are graphics file data formats for supposedly "vendor neutral" purposes for digital exchange of CAD (Computer Aided Design) drawings. (As opposed to, for example vendor-specific AutoCad data files, for which you need vendor-provided software like AutoCad to be able to read them).

Imagine if somebody told airplane or rocket developers [if NASA Eagleworks or Shawyer can be compared [?] to the Wright Brothers or Goddard] :"I stopped reading some time ago, it has now been [months (?) for us] since you guys have been writing about this in this forum.  Time to "let it go": give me detailed engineering-quality drawings showing how to make this so that I can fabricate it to test whether this flying machine or rocket does indeed fly"   :)

For Nanoracks vision, see:  http://nanoracks.com/about-us/our-vision/ or this video:




« Last Edit: 01/06/2015 03:16 PM by Rodal »

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1367
Hmmm...

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3226.html

"A self-accelerating electronic wave packet can acquire a phase akin to the Aharonov–Bohm effect, but in the absence of a magnetic field."
"The vector potential in question is a gauge-dependent quantity, namely a mathematical construct whose form is not uniquely defined."

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3196.html

"The Aharonov–Bohm effect predicts that two parts of the electron wavefunction can accumulate a phase difference even when they are confined to a region in space with zero electromagnetic field. Here we show that engineering the wavefunction of electrons, as accelerating shape-invariant solutions of the potential-free Dirac equation, fundamentally acts as a force and the electrons accumulate an Aharonov–Bohm-type phase—which is equivalent to a change in the proper time and is related to the twin-paradox gedanken experiment. This implies that fundamental relativistic effects such as length contraction and time dilation can be engineered by properly tailoring the initial conditions. As an example, we suggest the possibility of extending the lifetime of decaying particles, such as an unstable hydrogen isotope, or altering other decay processes. We find these shape-preserving Dirac wavefunctions to be part of a family of accelerating quantum particles, which includes massive/massless fermions/bosons of any spin."

See:

http://www.nature.com/nphys/journal/vaop/ncurrent/extref/nphys3196-s1.pdf
« Last Edit: 01/06/2015 05:59 PM by Notsosureofit »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
The main criticism against propellant-less EM Drives has been conservation of momentum.

It is discussed here that conservation of momentum for certain effects (like the Aharonov-Bohm Effect) is neither trivial nor has it been satisfactorily derived

Feynman's conservation of momentum paradox and the Aharonov-Bohm Effect

http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1129&context=physicsfacpub

Quote
what is the correct force expression for the force on the solenoid and
second, the assumption that Newton’s third law holds in the sense that the
change of the solenoid’s momentum is compensated by the change of the
electron’s momentum. The discussion of “Feynman’s paradox” shows that
the latter is not always the case. It is possible that a change in field momentum
is an essential part of the Aharonov-Bohm discussion, which is exactly
what Aharonov and Casher claim in 1984 [45]. Many theoretical papers have
discussed this issue [16, 17, 36, 37]. These discussions involve imbalanced
forces, field momentum and relativistic terms, all of which are present in our
above discussion. However, none of the discussions gives an explicit and exact
derivation of the delicate balance of all the momentum terms, but often
resort to a treatment of simplified systems. For example, Aharonov and D.
Rohrlich [16] discuss a flux tube with a radially moving charge, instead of a
charge passing by the flux tube. While the issue of whether the charge distribution
of the solenoid is perturbed has been addressed [17, 36, 46], none of
the discussions mention the relativistic electric field imbalance.
As it is possible to describe a solenoid as a collection of moving charged
particles, the above treatment of the Feynman paradox provides hope to settle
the theoretical discussion on forces. Integration over a solenoidal current
distribution would provide an exact derivation of momentum conservation
for the Aharonov-Bohm case.
« Last Edit: 01/06/2015 05:55 PM by Rodal »

Offline savuporo

  • Senior Member
  • *****
  • Posts: 5155
  • Liked: 975
  • Likes Given: 345
Guys, Guys......I stopped reading some time ago.....now we are into the 2nd thread.
Not being read or heard. There is absolutely nothing related to spaceflight here.

Again, NASA tested what, a 20 watt setup ? That is within power budget of a 3U cubesat. Flight model ? Demonstrate torque, if not directional thrust ?
Orion - the first and only manned not-too-deep-space craft

Tags: