Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2098514 times)

Offline TheTraveller

Can someone explain why the EMdrive experiment isn't run inside Helmholtz Coils (to cancel Earth magnetic field)?

The propulsion could be easily explained by the interaction between the large DC currents used to operate the magnetron/RF power amplifier with Earth’s magnetic field by way of the Lorentz force. In other words, a homopolar motor. This is an experiment that any child can do with a battery and a piece of wire:

http://en.wikipedia.org/wiki/Homopolar_motor

To do a proper measurement, the Earth's magnetic field should be canceled around the experiment using this setup:

http://en.wikipedia.org/wiki/Helmholtz_coil

Assuming one believes Shawyer's experimental reports, wouldn't that interaction with the Earth's negative field be negated by the fact that Shawyer claims to have measured similar thrust/PowerInput for the EM Drive pointing small base UP (vertical), small base DOWN (vertical), small base to the RIGHT (horizontal)  ?

I referring to NASA's experimental setup, not Shawyer's. (I consider Shawyer's setup to be too sloppy - rotating platform, with laptop? with fans? and rotating hard-disk? Extremely unprofessional).

In NASA's setup, there is still a shared ground connection between the source and the device-under-test, so it's not fully balanced AC. You can never be sure about residual ground currents, ground loops etc. It can easily cause this residual force, and explain the large variation between various experimental setups.

It would be a wise precaution to run this experiment inside Helmholtz coils to cancel possible interactions with Earth's magnetic field.
EW is actually replicating Shawyers Teeter Totter balance beam for their next round.

The Teeter Totter balance beam setup (which has the EM Drive mounted vertically, which eliminates thernal buckling effects EW experienced) was used for the 1st test EM Drive and for the 3rd EM Drive, the Flight Thruster. The rotary rig was used to test the 2nd EM Drive as was the Teeter Totter rig.

Shawyers superconduction test rig is a variation of the Teeter Totter test rigs.

That EW are changing their measurement system to Shawyers Teeter Totter balance beam system should tell you something.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Quote from: Rodal
Quote from: Bubs
Extremely unprofessional
?
He's referring to spurious angular momentum from various rotating components of the test equipment possibly coupling into the angular momentum of the platform on the air bearing.

Offline WarpTech

  • Full Member
  • ****
  • Posts: 1223
  • Do it!
  • Vista, CA
  • Liked: 1288
  • Likes Given: 1737
Using low temps and low power is definitely the way to go during this "how does it work?" phase.  Much safer.  But keep your eyes away from it and have a microwave leak detector at hand.

The high-power engineering can be done after the basic principles involved are understood.
2.45GHz is home microwave oven frequency. Most run around 600W. I'm sure forum menber have seen what 600W of microwave can do in regard to plasma creation and other pryotechinque tricks in a microwave oven.

Using a 1kW magnetron could do serious damage to people & equipment around a EM Drive if any microwave energy escaped. So please use microwave leak detectors and limit time close to the cavity.

Shawyer has experienced this. He made this comment about leaking microwaves interfering with his video camera when filming the rotary test rig.

Is why I'll build a Faraday Cage around my test unit so to stop microwave leaks interfering with my test and control system.

From what I read today elsewhere, I gather that you should also cover the walls of your lab in microwave absorbers, so if any does leak out, it isn't reflected back.

Todd

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Why would you care? - photon rocket effects are 3 orders down

Offline Bubs

  • Member
  • Posts: 5
  • Liked: 0
  • Likes Given: 1
There is still a shared ground connection between the source and the device-under-test, so it's not fully balanced AC. You can never be sure about residual ground currents, ground loops etc. It can easily cause this residual force, and explain the large variation between various experimental setups.

It would be a wise precaution to run this experiment inside Helmholtz coils to cancel possible interactions with Earth's magnetic field.
I ran the numbers and was surprised how little current it takes. I assumed it ran in the shield of the RF feed coax and took length to be 0.5m. That yields 4 Amps of ground loop current necessary to produce 100 uN in the Earth's field.

So yeah - except that reversing the test article pretty much reverses the thrust and does NOT reverse your Lorentz force. So I think it's unnecessary.

NASA's RF PA runs around 10Amps, so double that number to 200uN. That's the same order of magnitude (or more) as the measured EMdrive trust, so it would be wise to completely cancel this potential magnetic interaction. Regarding reversing the test article - it depends exactly how the 'reversing' is done - how are the wires re-routed? Could they be re-routed in a different orientation? It can be easily done "wrong", wrt. to earth's magnetic field. It's better to avoid those questions entirely by running inside Helmholtz coils...

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
No and no. That 10 Amps is main current, not residual ground loop current . Reversing the test article leaves the coax feed exiting in the same place, so also no.

Offline Bubs

  • Member
  • Posts: 5
  • Liked: 0
  • Likes Given: 1
No and no. That 10 Amps is main current, not residual ground loop current . Reversing the test article leaves the coax feed exiting in the same place, so also no.

DC loops are notorious in RF power systems. You may think that the 10 Amps are returning via your carefully routed 20 AWG ground wire, while in fact the majority of the current may be returning via the 0000 AWG metallic truss. There is no ground isolation or balanced-DC design in either experiments, so expect the worse.
« Last Edit: 05/08/2015 03:29 AM by Bubs »

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Such a shame it's so difficult to simply put it in space and check. It would have saved Woodward 20 years and I don't know how many years on this already.

I speak as someone who watched Apollo 11 on the moon.

Offline WarpTech

  • Full Member
  • ****
  • Posts: 1223
  • Do it!
  • Vista, CA
  • Liked: 1288
  • Likes Given: 1737
Consider the following EM Drive design:

1st component: A symmetrical resonator cavity that is optimized to store energy at high Q, and plays no role in thrust. Here, we want to store the lowest order mode that the waveguide can sustain because it has the slowest wave velocity inside the waveguide. By targeting the slowest wave velocity, we are maximizing the amount of stored electromagnetic momentum for a given amount electromagnetic energy.

p = E/v, where  v << c inside the waveguide.
E = P*t, energy is power in x time (assuming a lossless cavity)

2nd component: We need a frustum that matches the diameter of the resonant chamber "at the small end" and slowly expands to a TBD length and diameter. As the waveguide expands, the wavelength will be increasing proportional to the increasing wave velocity. We want it to expand to near it's free space value.

3rd component: We need a partial reflector, between the two, so that we can have resonance in one chamber, and thrust in the other. Like a laser.

Principle of operation:

When the energy stored in the resonant chamber is released into the frustum, it expands due to the increased wave velocity to a longer wavelength before it is reflected. It leaves the "nozzle" with momentum p1, but when it arrives at the reflector, it has momentum p2 << p1, because the wave velocity has increased "significantly".

The reflected waves then travel back into the frustum only to find that due to their increased wavelength, now they don't fit anymore, so they are attenuated. Again, absorbing the momentum into the frustum as heat and kinetic energy in the "forward" direction.

To put it quantum mechanically:

N photons are injected at momentum p1 = N*h/lambda_1

N photons are reflected at the far end with momentum p2 = N*h/lambda_2

The wavelengths are not equal. Momentum is conserved because the system moves forward. The red-shifted photons are mimicking a gravitational field. They are trying to escape a gravity well, only to be reflected back in and fall back through the event horizon as wave velocity goes to zero. (Sorry I love that analogy!)

Todd Desiato



« Last Edit: 05/08/2015 05:55 AM by WarpTech »

Offline FieldEffect

Im seeing an overlap between this kind of work and work done by T.T.Brown...
anyone care to briefly comment on it?

(Incase your unfamiliar with T.T. Brown, he discovered Biefeld-Brown effect, but also discovered another force that he insisted was NOT biefeld-brown effect (ion wind), also he believed the dielectric played a primary role in the force, and that a reaction force existed on "all solid material bodies making up the physical environment")

He makes some very peculiar statements in his 1929 article, which lead me to believe he was an honest experimenter (ofcourse he explains in terms of what people knew in the 1920's)
the 1929 article & gravitator patent: http://www.rexresearch.com/gravitor/gravitor.htm#patent

This patent strikes me the most (attached): US3187206 (1965),
He has a Half-Wave Radiator, tapered dielectric member etc...

please tell me what you think because im seeing a fair bit of crossover.

I seriously think there is something to be gleaned from TTBrown's work.

Regards.

PS: Im thoroughly enjoying the thread, wish i was as up to speed as you lot.  8)

Offline deuteragenie

  • Member
  • Posts: 71
  • Germany
  • Liked: 22
  • Likes Given: 0
Latest paper by Dr. White, on http://ntrs.nasa.gov/ , exploring the idea of the quantum vacuum not being an absolute immutable and nondegradable state, and examining  some rami cations of the quantum vacuum being able to support non-trivial spatial variations in density.  They claim that their "considerations showed no predictions that were contrary to observation, and in fact duplicated predictions for energy states associated with the primary quantum number."

http://hdl.handle.net/2060/20150006842

Dynamics of the Vacuum and Casimir Analogs to the Hydrogen Atom
Harold White, Jerry Vera,y Paul Bailey,z Paul March,x Tim Lawrence,{ Andre Sylvester, and David Brady
NASA Johnson Space Center
2101 NASA Parkway, Houston, TX 77058
(Dated: April 2, 2015)

Publication Date:   Apr 02, 2015
Document ID:   
20150006842 (Acquired Apr 28, 2015)
Subject Category:   PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ATOMIC AND MOLECULAR PHYSICS; NUMERICAL ANALYSIS; COMPUTER PROGRAMMING AND SOFTWARE
Report/Patent Number:   JSC-CN-33080
Document Type:   Technical Report
Financial Sponsor:   NASA Johnson Space Center; Houston, TX, United States
Organization Source:   NASA Johnson Space Center; Houston, TX, United States
Description:   9p; In English

There is an error in the integration of equation 11. Apparently their "simple enough" integration was not simple enough!

Indeed.  Should be something like 4 pi A0 C^2 (Rn - R0)

Offline deuteragenie

  • Member
  • Posts: 71
  • Germany
  • Liked: 22
  • Likes Given: 0
Quote
Rodal:
Interestingly (for this thread's discussion due to the significance that the NASA experimenters have placed on the dielectric being responsible for providing the measured thrust) is what happens in the High Density PolyEthylene (HDPE) dielectric polymer insert.  Because the dimensions of the dielectric are not negligible compared to the EM Drive's dimension, and the dielectric is not modeled as just a boundary condition.

The loss tangent of HDPE is reported to be

tan delta = 0.0004

Therefore the intrinsic impedance angle is

intrinsic impedance angle =(ArcTan[0.0004])/2

Therefore, inside the HDPE dielectric the electric and magnetic fields, instead of being out of phase by 90 degrees (as they are in the air or vacuum medium), will be out of phase by:

90 - (ArcTan[0.0004])/2 = 89.9998 degrees

This phase angle (89.9998 degrees)  will show practically no visual difference with 90 degrees at the resolution of the following image :

Mr Rodal can you advise me on the value .0004 in your work above,  is that in degrees or radians or just a figure that one simply takes the arctan of.  Im trying to use the "bc" program in linux command line to get a grip on the overall topic, and bc reports results in radians, hence the requirement to do a 180/pi conversion.

echo "scale=20; 90 - (a(0.0004)/2)*(180/(4*a(1)))" | bc -l
89.98854084470853845905

Thanks
arc

Last three digits are incorrect I believe.
Here is the correct value:

89.98854084470853845862664694223578691171775499331997712909452 ...


Offline deuteragenie

  • Member
  • Posts: 71
  • Germany
  • Liked: 22
  • Likes Given: 0
Im seeing an overlap between this kind of work and work done by T.T.Brown...
anyone care to briefly comment on it?

(Incase your unfamiliar with T.T. Brown, he discovered Biefeld-Brown effect, but also discovered another force that he insisted was NOT biefeld-brown effect (ion wind), also he believed the dielectric played a primary role in the force, and that a reaction force existed on "all solid material bodies making up the physical environment")

He makes some very peculiar statements in his 1929 article, which lead me to believe he was an honest experimenter (ofcourse he explains in terms of what people knew in the 1920's)
the 1929 article & gravitator patent: http://www.rexresearch.com/gravitor/gravitor.htm#patent

This patent strikes me the most (attached): US3187206 (1965),
He has a Half-Wave Radiator, tapered dielectric member etc...

please tell me what you think because im seeing a fair bit of crossover.

I seriously think there is something to be gleaned from TTBrown's work.

Regards.

PS: Im thoroughly enjoying the thread, wish i was as up to speed as you lot.  8)

Asymmetrical Capacitors for Propulsion : http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171929.pdf

Conclusions: "... In spite of decades of speculation about possible new physical principles being responsible for the thrust produced by ACTs and lifters, we find no evidence to support such a conclusion. On the contrary, we find that their operation is fully explained by a very simple theory that uses only
electrostatic forces and the transfer of momentum by multiple collisions
. ".

My understanding is that for emDrive, the new tests were successfully performed in a (close to) vacuum.

Offline FieldEffect

Im seeing an overlap between this kind of work and work done by T.T.Brown...
anyone care to briefly comment on it?

(Incase your unfamiliar with T.T. Brown, he discovered Biefeld-Brown effect, but also discovered another force that he insisted was NOT biefeld-brown effect (ion wind), also he believed the dielectric played a primary role in the force, and that a reaction force existed on "all solid material bodies making up the physical environment")

He makes some very peculiar statements in his 1929 article, which lead me to believe he was an honest experimenter (ofcourse he explains in terms of what people knew in the 1920's)
the 1929 article & gravitator patent: http://www.rexresearch.com/gravitor/gravitor.htm#patent

This patent strikes me the most (attached): US3187206 (1965),
He has a Half-Wave Radiator, tapered dielectric member etc...

please tell me what you think because im seeing a fair bit of crossover.

I seriously think there is something to be gleaned from TTBrown's work.

Regards.

PS: Im thoroughly enjoying the thread, wish i was as up to speed as you lot.  8)

Asymmetrical Capacitors for Propulsion : http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171929.pdf

Conclusions: "... In spite of decades of speculation about possible new physical principles being responsible for the thrust produced by ACTs and lifters, we find no evidence to support such a conclusion. On the contrary, we find that their operation is fully explained by a very simple theory that uses only
electrostatic forces and the transfer of momentum by multiple collisions
. ".

My understanding is that for emDrive, the new tests were successfully performed in a (close to) vacuum.

I agree with you for the most part, but i also believe im seeing too many coincidences.
It was assumed by conspirators that the asymmetrical capacitor and hence a non-uniform electric field would produce anti-gravity, obviously that's false. TTBrown believed the force was from the dielectric.
 
If the mechanism described by marco frasca is correct,
isnt it possible that TTBrown failed to recognise he had actually built a dielectric resonator, and with the very high voltages used, achieved "gross intensity of the electromagnetic energy" (as Marco put it) and then mistakenly put it down to the very high voltages he was using?

wouldnt the AC source emit microwaves at the small electrode (that he advised be half-the wavelength in diameter)? TTBrown mentions things in the 1965 patent like including Lead-Oxide in the dielectric to increase the effect.

also his "Gravitator" (big heavy capacitor/condenser hung like a pendulum) he describes as recieving an impulse when switched on, and would slowly return to its original rest position, even though the potential was maintained.
Would the initial charging of the gravitator at high voltage emit a high-power radio signal that would resonate throughout the dielectric insulators? inducing the effect marco wrote about?

(Im not arguing, I wanna know what you guys think).

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
Quote
Rodal:
Interestingly (for this thread's discussion due to the significance that the NASA experimenters have placed on the dielectric being responsible for providing the measured thrust) is what happens in the High Density PolyEthylene (HDPE) dielectric polymer insert.  Because the dimensions of the dielectric are not negligible compared to the EM Drive's dimension, and the dielectric is not modeled as just a boundary condition.

The loss tangent of HDPE is reported to be

tan delta = 0.0004

Therefore the intrinsic impedance angle is

intrinsic impedance angle =(ArcTan[0.0004])/2

Therefore, inside the HDPE dielectric the electric and magnetic fields, instead of being out of phase by 90 degrees (as they are in the air or vacuum medium), will be out of phase by:

90 - (ArcTan[0.0004])/2 = 89.9998 degrees

This phase angle (89.9998 degrees)  will show practically no visual difference with 90 degrees at the resolution of the following image :

Mr Rodal can you advise me on the value .0004 in your work above,  is that in degrees or radians or just a figure that one simply takes the arctan of.  Im trying to use the "bc" program in linux command line to get a grip on the overall topic, and bc reports results in radians, hence the requirement to do a 180/pi conversion.

echo "scale=20; 90 - (a(0.0004)/2)*(180/(4*a(1)))" | bc -l
89.98854084470853845905

Thanks
arc

In:

tan delta = 0.0004

delta is an angle (whose dimension can be expressed in degrees or in radians, but I have not used delta, so the dimensions of delta did not matter).  It is called the loss angle (see:  https://en.wikipedia.org/wiki/Dielectric_loss   http://www.microwaves101.com/encyclopedias/transmission-line-loss ).  Both the loss angle delta and tan delta characterize a material property.

tan delta is commonly used nomenclature used for the Tangent of the angle delta ( Tangent[delta] ), as such tan delta is a dimensionless number

The "intrinsic impedance angle" on the other hand is an angle, and as such one needs to carefully decide whether one wants to express it in radians or degrees or any other unit as long as one consistently uses it

In the example I gave above, you are correct, it was missing the conversion factor, it should have read

90 - (180/Pi) (ArcTan[0.0004])/2 = 89.98854084470854

Thank you for finding this error :)  I have corrected the original

The important final numerical result (0.00009999999400006368) for the magnitude of the mean (over a period) of the Poyinting vector was not affected:

Cos[(Pi/180) (90 - (180/Pi) (ArcTan[0.0004])/2)]/2= 0.00009999999400006368

Inside the HDPE polymer dielectric the Poynting vector has this small magnitude factor over a period (or multiples thereof).



« Last Edit: 05/08/2015 01:01 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
Consider the following EM Drive design:

1st component: A symmetrical resonator cavity that is optimized to store energy at high Q, and plays no role in thrust. Here, we want to store the lowest order mode that the waveguide can sustain because it has the slowest wave velocity inside the waveguide. By targeting the slowest wave velocity, we are maximizing the amount of stored electromagnetic momentum for a given amount electromagnetic energy.

p = E/v, where  v << c inside the waveguide.
E = P*t, energy is power in x time (assuming a lossless cavity)

2nd component: We need a frustum that matches the diameter of the resonant chamber "at the small end" and slowly expands to a TBD length and diameter. As the waveguide expands, the wavelength will be increasing proportional to the increasing wave velocity. We want it to expand to near it's free space value.

3rd component: We need a partial reflector, between the two, so that we can have resonance in one chamber, and thrust in the other. Like a laser.

Principle of operation:

When the energy stored in the resonant chamber is released into the frustum, it expands due to the increased wave velocity to a longer wavelength before it is reflected. It leaves the "nozzle" with momentum p1, but when it arrives at the reflector, it has momentum p2 << p1, because the wave velocity has increased "significantly".

The reflected waves then travel back into the frustum only to find that due to their increased wavelength, now they don't fit anymore, so they are attenuated. Again, absorbing the momentum into the frustum as heat and kinetic energy in the "forward" direction.

....

Excellent.  This makes to me more engineering sense than the closed cavity design pioneered by Shawyer and imitated in the US and Chinese laboratories.

(Also, let's think of a maser )

So it looks to me that if the UK/US/Chinese measurements are real (*), the design you sketched above should produce more thrust than the present designs.

___
(*) if they are real, I would like to summarize the present understanding regarding the energy paradox.  I thought you had reached a common conclusion but @frobnicat raised apparently new points that apparently still need to be addressed ?

....

To put it quantum mechanically:

N photons are injected at momentum p1 = N*h/lambda_1

N photons are reflected at the far end with momentum p2 = N*h/lambda_2

The wavelengths are not equal. Momentum is conserved because the system moves forward. The red-shifted photons are mimicking a gravitational field. They are trying to escape a gravity well, only to be reflected back in and fall back through the event horizon as wave velocity goes to zero. (Sorry I love that analogy!)

Todd Desiato

Where would the Q factor enter into consideration?

(Without the Q into the thrust force equation, we still have an inefficient photon rocket)
« Last Edit: 05/08/2015 12:34 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
Such a shame it's so difficult to simply put it in space and check. It would have saved Woodward 20 years and I don't know how many years on this already.

I speak as someone who watched Apollo 11 on the moon.
Do you think is difficult to put in space?

(if so why?, because of engineering difficulty, because of expense, or because of the will of any organization to take a risk on a very controversial item that may not work)

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Clearly it's not easy.  EagleWorks would have their rig up there in a heartbeat if it was easy.

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1361
Consider the following EM Drive design:

1st component: A symmetrical resonator cavity that is optimized to store energy at high Q, and plays no role in thrust. Here, we want to store the lowest order mode that the waveguide can sustain because it has the slowest wave velocity inside the waveguide. By targeting the slowest wave velocity, we are maximizing the amount of stored electromagnetic momentum for a given amount electromagnetic energy.

p = E/v, where  v << c inside the waveguide.
E = P*t, energy is power in x time (assuming a lossless cavity)

2nd component: We need a frustum that matches the diameter of the resonant chamber "at the small end" and slowly expands to a TBD length and diameter. As the waveguide expands, the wavelength will be increasing proportional to the increasing wave velocity. We want it to expand to near it's free space value.

3rd component: We need a partial reflector, between the two, so that we can have resonance in one chamber, and thrust in the other. Like a laser.

Principle of operation:

When the energy stored in the resonant chamber is released into the frustum, it expands due to the increased wave velocity to a longer wavelength before it is reflected. It leaves the "nozzle" with momentum p1, but when it arrives at the reflector, it has momentum p2 << p1, because the wave velocity has increased "significantly".

The reflected waves then travel back into the frustum only to find that due to their increased wavelength, now they don't fit anymore, so they are attenuated. Again, absorbing the momentum into the frustum as heat and kinetic energy in the "forward" direction.

To put it quantum mechanically:

N photons are injected at momentum p1 = N*h/lambda_1

N photons are reflected at the far end with momentum p2 = N*h/lambda_2

The wavelengths are not equal. Momentum is conserved because the system moves forward. The red-shifted photons are mimicking a gravitational field. They are trying to escape a gravity well, only to be reflected back in and fall back through the event horizon as wave velocity goes to zero. (Sorry I love that analogy!)

Todd Desiato

Excellent.  This makes to me much more engineering/scientific sense than the closed cavity design pioneered by Shawyer and imitated in the US and Chinese laboratories.

So it looks to me that either the UK/US/Chinese measurements are an artifact, or if they are real (*), the design you sketched above should produce more thrust than the present designs.

___
(*) if they are real, I would like to summarize the present understanding regarding the energy paradox.  I thought you had reached a common conclusion but @frobnicat raised apparently new points that apparently still need to be addressed ?


Mmmm.....   Maybe I'm missing something here?  Do I need a diagram of these coupled cavities?

The statement " The reflected waves then travel back into the frustum only to find that due to their increased wavelength, now they don't fit anymore, so they are attenuated. Again, absorbing the momentum into the frustum as heat and kinetic energy in the "forward" direction. "  makes no sense.  As they travel back into the frustrum the velocity decreases again.   Even if they were "attenuated" w/o momentum transfer you would still have, at best, a self blown photon sail ????

Todd:  If you take my GR calculation and redo it in "index of refraction" terms you should get the same force result.

Ultimately, what needs to be shown here is that the "covariant force vector equal to zero" on a photon in the accelerated frame is the same vector in the cavity rest frame (ie. can be transformed to) such that the force on a photon in the rest frame is a result of the (velocity) dispersion due to the shape of the cavity boundary conditions.  That transformation would show that the effect is to be expected under General Relativity.
« Last Edit: 05/08/2015 01:05 PM by Notsosureofit »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
Yes, I added:

Where would the Q factor enter into consideration?

(Without the Q into the thrust force equation, we still have an inefficient photon rocket)

[and when one enters the Q factor for a closed cavity, I yet have to embrace an explanation for a closed cavity where I can fully see conservation of momentum and conservation of energy satisfied.  For example, Shawyer only takes into account the forces perpendicular to the bases and neglects the counterbalancing forces from the conical surface which result in zero net thrust force]

Ditto for the GR calculation: they are one-dimensional longitudinal approximations, where the index of refraction changes in the longitudinal direction: but the truncated cone is 3-D and has counterbalancing forces due to the forces on the conical surface which cancel the thrust

If I'm wrong, I would like someone to show what happens with the forces on the conical surface (which are at an angle to the longitudinal direction)

I need a free-body diagram showing the force vectors on all the copper surfaces for the 3-D problem force summation  :)

« Last Edit: 05/08/2015 12:58 PM by Rodal »

Tags: