I've slightly trimmed this thread as the troubles of a social media site has no reflection on this site's thread. This thread is about the EM Drive.
Long time reader, first time poster here.
I'm not qualified to comment on any of this (software engineer with an armchair
physics fascination), but I will anyway.
So here's my hypothesis as to an explanation for Emdrive thrust.
Imagine a cavity injected with high frequency EM radiation, sitting on the
ground in Earth's gravational field.
There is an ever so slight difference in gravitational field strength between
the top and bottom of the cavity - stronger at the bottom than the top. For a
10cm high cavity in Earth's gravity at sea level the difference in field
strength is about 1 part in a million between the top wall and the bottom wall
(back of napkin calculation).
Relativity says that light is red-shifted in a stronger gravitational field.
This means that the momentum of the photons hitting the bottom of the cavity
will be less than those hitting the top. This difference in momentum produces
a force towards the top of the cavity (away from the center of the Earth). This
results in an asymmetric force between the top and bottom of the cavity and
hence thrust.
What's potentially interesting about this is that the thrust per KW will be
subject to an inverse square law of the distance from a massive body because
the delta between the gravitational field strength between the top and bottom
of the cavity will decrease and tend to zero the further the cavity is away
from a massive object.
This hints that energy may be conserved by virtue of the fact that more energy
will be required to produce a constant thrust as distance from a massive body
increases.
This also hints that momentum is conserved because the momentum the photons
lose due to red shifting is conserved by moving the cavity.
Another observation is that the efficiency of the emdrive will be greater when
the delta between gravitational field strength between the top and bottom of
the cavity is greater - this means increasing the height of the cavity should
increase performance.
Another observation is that higher Q implies higher thrust: multiple reflections
increases amount of differential red shifting.
This hypothesis also implies that perfectly horizontal thrust will not be
possible due to gravitational force being a vector. Given that concensus has
not been reached that thrust is larger than error bars, I'm not sure if this
has been ruled out.
Doing the math for this is beyond my ability. It would be great if someone
could do some modeling.
Anyway, I'm happy for this idea to be torn apart. It came to me over lunch
just now and I just had to write it down.
If you read this far: thank you for giving a layperson a chance to air his
thoughts!
Cheers,
James.
It seems clear that any thrust from this effect could not be greater than a photon rocket (and in fact must be far less than that), while actually reported thrusts are hundreds to thousands of times greater than photon-rocket thrust.
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Roger's 1st Experimental EmDrive, with a long & position adjustable dielectric at the small end, did generate force toward the big end, which is explainable as per his theory.
Well, looks like all Dave's posts written since may 16th ware deleted.
Does anyone know what's happened?
Well, looks like all Dave's posts written since may 16th ware deleted.
Does anyone know what's happened?
We will be looking after this thread via the general NSF moderation for the interim period. Moderators can remove messages when required, members can remove their own messages if they wish. The answer your question, the above was a combination of both. Everything past this comment would be personal and not for this public thread.
Dave is a good guy and still a welcome member of this forum.
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Roger's 1st Experimental EmDrive, with a long & position adjustable dielectric at the small end, did generate force toward the big end, which is explainable as per his theory.
1) What mode shape was excited in that experiment?
2) In what report is this experiment, including force direction and location of the dielectric inside the frustum of a cone, discussed?
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Roger's 1st Experimental EmDrive, with a long & position adjustable dielectric at the small end, did generate force toward the big end, which is explainable as per his theory.
Is there a report where we can find out at what end of the EM Drive did he place the dielectric material? (at the Big End or at the Small End)?
At the small end as I stated. This information has been published here several times. See attached image and a portion of the paper Roger provided to EW. Note the big end plate position could be adjusted in and out as well as the amount of dielectric rod penetration inside the small end of the frustum adjusted to get the force generated tuning as good as it could be.
As in the last attachment, the Experimental EmDrive is the SPR Type 2 (4th line down in the central table) showing how the small end located dielectric generated force toward the big end.
Would the following paper apply also to microwaves?
http://arxiv.org/abs/1603.07224
Photon mass drag and the momentum of light in a medium
as a direct consequence of the fundamental conservation laws of nature and the special theory of relativity, the energy and momentum of light propagating in a medium are carried by quasiparticles, coupled states of fi eld and matter, which have a finite rest mass and the Minkowski form of momentum...The finite rest mass of the quasiparticle directly leads to a photon mass drag effect optomechanically displacing the medium along the photon flow
Thanks for driving this point home. With the exception of EmDrive tests in vacuum with no dielectric and of course no air present.....there's always a medium present.
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Roger's 1st Experimental EmDrive, with a long & position adjustable dielectric at the small end, did generate force toward the big end, which is explainable as per his theory.
Is there a report where we can find out at what end of the EM Drive did he place the dielectric material? (at the Big End or at the Small End)?
At the small end as I stated. This information has been published here several times. See attached image and a portion of the paper Roger provided to EW. Note the big end plate position could be adjusted in and out as well as the amount of dielectric rod penetration inside the small end of the frustum adjusted to get the force generated tuning as good as it could be.
As in the last attachment, the Experimental EmDrive is the SPR Type 2 (4th line down in the central table) showing how the small end located dielectric generated force toward the big end.
Thank you. I had not finished writing my post, when I realized that you had already answered the location. Do you know an answer to this question:
What
mode shape was excited in that experiment by Shawyer?
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Roger's 1st Experimental EmDrive, with a long & position adjustable dielectric at the small end, did generate force toward the big end, which is explainable as per his theory.
Is there a report where we can find out at what end of the EM Drive did he place the dielectric material? (at the Big End or at the Small End)?
At the small end as I stated. This information has been published here several times. See attached image and a portion of the paper Roger provided to EW. Note the big end plate position could be adjusted in and out as well as the amount of dielectric rod penetration inside the small end of the frustum adjusted to get the force generated tuning as good as it could be.
As in the last attachment, the Experimental EmDrive is the SPR Type 2 (4th line down in the central table) showing how the small end located dielectric generated force toward the big end.
Thank you. I had not finished writing my post, when I realized that you had already answered the location. Do you know an answer to this question:
What mode shape was excited in that experiment by Shawyer?
Roger has, to my knowledge, never shared that information. What he did say to me was the Flight Thruster and all further builds were done using TE013 mode plus the Demonstrator EmDrive build and all further builds no longer used a dielectric and used spherical end plates.
As far as I know, the Demonstrator EmDrive build was the last to use mechanical tuning as from the Flight Thruster onward, all tuning was electronic other than the very small length adjustment using piezo adjusters to compensate for acceleration generated cavity detuning experienced in very high Q cryo cavities.
Any experts, on Shawyer's or McCulloch's theory: can Shawyer's theory or McCulloch's theory explain the direction of the thrust measured by Monomorphic?
McCulloch's theory cannot, except by thermal effects, or other forms of experimental error.
Roger's 1st Experimental EmDrive, with a long & position adjustable dielectric at the small end, did generate force toward the big end, which is explainable as per his theory.
Is there a report where we can find out at what end of the EM Drive did he place the dielectric material? (at the Big End or at the Small End)?
At the small end as I stated. This information has been published here several times. See attached image and a portion of the paper Roger provided to EW. Note the big end plate position could be adjusted in and out as well as the amount of dielectric rod penetration inside the small end of the frustum adjusted to get the force generated tuning as good as it could be.
As in the last attachment, the Experimental EmDrive is the SPR Type 2 (4th line down in the central table) showing how the small end located dielectric generated force toward the big end.
This image:
has the force direction being
thrust, towards the Big End for the Shawyer with dielectric (Type 2).
It has
Tajmar TU Dresden force direction as
"reaction" towards the Small EndIt has
NASA standard test force directions as
"thrust" towards the Big EndNASA's force direction is towards the Small End.
I thought that TU Dresden force direction was also towards the Small End.
What is the reason for these discrepancies? Need to understand this in order to understand the
force direction for Shawyer's frustum with a dielectric type 2.
This image:
has the force direction being thrust, at the Big End for the Shawyer with dielectric (Type 2).
It has Tajmar TU Dresden force direction as "reaction" towards the Small End
It has NASA standard test force directions as "thrust" towards the Big End
NASA's force direction is towards the Small End.
I thought that TU Dresden force direction was also towards the Small End.
What is the reason for these discrepancies? Need to understand this in order to understand the force direction for Shawyer's frustum with a dielectric type 2.
You might want to compare the 2 blue lines?
I did ask Roger about the EW direction. Was told it was based on the information he received.
This image:
has the force direction being thrust, at the Big End for the Shawyer with dielectric (Type 2).
It has Tajmar TU Dresden force direction as "reaction" towards the Small End
It has NASA standard test force directions as "thrust" towards the Big End
NASA's force direction is towards the Small End.
I thought that TU Dresden force direction was also towards the Small End.
What is the reason for these discrepancies? Need to understand this in order to understand the force direction for Shawyer's frustum with a dielectric type 2.
You might want to compare the 2 blue lines?
I did ask Roger about the EW direction. Was told it was based on the information he received.
1)
What does "force direction" (third column in the table) mean in this Shawyer's table (force direction "thrust" indicated towards Big End for Type 2 Shawyer with dielectric)
2) If the Tajmar force direction is interpreted as correct, is there a discrepancy then for NASA's tests, since the majority of NASA's tests had the force and displacement towards the Small End?
This image:
has the force direction being thrust, at the Big End for the Shawyer with dielectric (Type 2).
It has Tajmar TU Dresden force direction as "reaction" towards the Small End
It has NASA standard test force directions as "thrust" towards the Big End
NASA's force direction is towards the Small End.
I thought that TU Dresden force direction was also towards the Small End.
What is the reason for these discrepancies? Need to understand this in order to understand the force direction for Shawyer's frustum with a dielectric type 2.
You might want to compare the 2 blue lines?
I did ask Roger about the EW direction. Was told it was based on the information he received.
1) What does "force direction" mean in this Shawyer's table (force direction "thrust" indicated towards Big End for Type 2 Shawyer with dielectric)
2) Is there a discrepancy then for NASA's tests, since the majority of NASA's tests had the force and displacement towards the Small End?
Thrust and Reaction are just labels. See below for acceleration force direction.
As I said Roger's acceleration force direction for the EW frustum is from the info he received from NASA, which may not be information that EW or Paul has released?
I never noticed that graphic for Cannae. They use an asymmetric dialectric (cone, pyramid?) inside a symmetric cavity and NASA uses a symmetric dialectric insert in an asymmetric cavity. Those are the inverse of one another geometrically.
Cal Polytech used symmetric insert with symmetric cavity, correct? Did they ever try different shapes of HDPE, like a cone?
You might want to compare the 2 blue lines?
I did ask Roger about the EW direction. Was told it was based on the information he received.
1) What does "force direction" mean in this Shawyer's table (force direction "thrust" indicated towards Big End for Type 2 Shawyer with dielectric)
2) Is there a discrepancy then for NASA's tests, since the majority of NASA's tests had the force and displacement towards the Small End?
Thrust and Reaction are just labels. See below for acceleration force direction.
As I said Roger's acceleration force direction for the EW frustum is from the info he received from NASA, which may not be information that EW or Paul has released?
Thank you for trying to clarify this confusing picture, as shown in the table, partly due to some experimenters not clearly showing the direction of measured force in their reports.
The red arrows are your interpretation, correct? (Is it correct that the red arrows were not in Shawyer's original drawing, ).
I hope that future reports on EM Drive experiments make all these variables, mode shape and direction of thrust, crystal clear, as it is a matter of interpretation now, what direction was the anomalous force directed towards, and having the direction of anomalous force for NASA's experiments in the wrong direction (contrary to what Star-Drive stated) doesn't help the interpretation of that chart.
That's going to be another benefit of an accelerating rotary experiment, as the direction of movement from the rotary experiment (if any) should be plain to see from a video. It will be most interesting to see whether a battery-powered EM Drive can rotary accelerate !
I never noticed that graphic for Cannae. They use an asymmetric dialectric (cone, pyramid?) inside a symmetric cavity and NASA uses a symmetric dialectric insert in an asymmetric cavity. Those are the inverse of one another geometrically.
Cal Polytech used symmetric insert with symmetric cavity, correct? Did they ever try different shapes of HDPE, like a cone?
Whether the Cannae cavity is a symmetric cavity with constant cylindrical cross-section is a matter of interpretation by Shawyer (who apparently ignores in that table the effect of the relatively huge pillbox resonant section in Cannae's drive). To my opinion, and to NASA's opinion (Brady, White, March et.al. wrote that there was a clear Poynting vector field in the Cannae drive), the Cannae cavity is NOT symmetric, as the dielectric is at the right hand pipe extension in this picture (therefore Cannae's drive is very UNsymmetric, due to the huge resonant chamber in the shape of a pillbox as used in particle accelerators, at the left end:
Also McCulloch analyzed the Cannae drive with McCulloch's formula interpreting the Cannae drive as an unsymmetric cavity.
Also, NASA did NOT use a cone dielectric for the Cannae drive, they used a PTFE ("Teflon") cylinder. You can see the dielectric in this COMSOL FEA model: (it is Shawyer that used a cone dielectric inside a cavity with constant cylindrical cross-section in one of his patents)
Also, NASA did NOT use a cone dielectric for the Cannae drive, they used a PTFE ("Teflon") cylinder. You can see the dielectric in this COMSOL FEA model: (it is Shawyer that used a cone dielectric inside a cavity with constant cylindrical cross-section in one of his patents)
This image has always confused me, so I'm not sure I'm seeing exactly what you're saying. The long thin rod down the center of the right pipe extension is the antenna right? Is the PTFE this cyclinder at the end and the antenna runs through that? What are the approximate dimensions and shape of the PTFE insert in Cannae drive?
EDIT: Corrected typo
Also, NASA did NOT use a cone dielectric for the Cannae drive, they used a PTFE ("Teflon") cylinder. You can see the dielectric in this COMSOL FEA model: (it is Shawyer that used a cone dielectric inside a cavity with constant cylindrical cross-section in one of his patents)
This image has always confused me, so I'm not sure I'm seeing exactly what you're saying. The long thin rod down the center of the right pipe extension is the antenna right? Is the PTFE this cyclinder at the end and the antenna runs through that? What are the approximate dimensions and shape of the PTFE insert in Cannae drive?
Unfortunately this detail may be covered by an NDA between Cannae and NASA.
All we know from NASA's Brady et.al report (*) is
Figure 9 shows a test article mounted on the torsion pendulum during a test campaign, and a test block diagram follows. The longer beam pipe is the RF drive antenna that in practice ends up being a ¼ wave resonance system in its own right and has a dielectric PTFE slug in the throat in both the slotted and null test article. It is this characteristic that became an item of further consideration after completion of the test campaign.
Computer modeling of the electric field within the pillbox and beam pipe (using COMSOL Multiphysics® software, hereafter referred to as “COMSOL®”) illustrates the relative weakness of the electric field in the vicinity of the cavity slots and relative strength of the electric field within the beam pipe, especially in the drive antenna coaxial cable and the region around the cable within the PFTE dielectric slug as seen in Fig. 14. Consideration of the dynamic fields in the ¼ wave resonance tube shows that there is always a net Poynting vector meaning that the RF launcher tube assembly with dielectric cylinder common to both the slotted and smooth test articles is potentially a Q-thruster where the pillbox is simply a matching network.
(Typo PFTE instead of PTFE is in the original report)
so, you are right, the rest is our interpretation. The
electromagnetic field inside what I interpret as the PTFE slug has the shape of a cone with the apex pointing towards the right, away from the pillbox end. Again, this is the electromagnetic field shape, that's all we know from that picture?
(*) Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum
David A. Brady*, Harold G. White†, Paul March‡, James T. Lawrence§, and Frank J. Davies**
NASA Lyndon B. Johnson Space Center, Houston, Texas 77058