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#1620 by OnlyMe on 13 Oct, 2016 22:19
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That was kind of my point! Any kinetic energy of the fuel in the launch/observer's frame has nothing to do with the rocket's performance. The combustion rate and resulting combustion related kinetic energy of combustion do. The efficiency of the rocket would drop off as the rockets acceleration begins to exceed the combustion rate. Other than that once the rocket is in deep space or has attained an escape velocity for any relevant gravity, kinetic energy in any frame becomes a fictitious value.
Forgive me, it maybe because English is not my native language, but I do not understand clearly what you means.
Of course, if the rocket is escaping from the earth, we have to take into account the gravity losses, but I do not see why kinetic energy in any frame would becomes fictitious.
IMHO, the "upper stage paradox" is perfectly solved by the formula of Wicoe.
We can take into account the earth gravity well by adding a term.
"The increase of kinetic energy of a rocket (or the upper stage, which is still a rocket) equals the chemical energy delivered by its own fuel burnt less the total kinetic energy gained (has to be read as "lost" if negative) by the propellant, less the energy lost as waste heat, and less the gravity losses if it is initially in a gravity well"
While it is possible to add kinetic energy to your calculations when evaluating the rocket from the earth' s frame, it remains fictitious because the rocket's kinetic energy is different in different frames. An object's kinetic energy in its own frame of reference is always zero, setting aside heat and quantum effects... And it is zero in the rocket's frame whether the rocket is inertial or accelerating.
It does not add any real force/power to the combustion of the fuel and since it is different when calculated from different frames it has no impact on continued acceleration. It sometimes seems important because in some arguments, it can be confused with changes in an object's inertia. (A word which itself can sometimes be confusing, depending on how it is used.)
Some while back I read a paper that was evaluating the practicality of sending a spaceship to another star system, at 0.2 c. They addressed the issue far better than I. I will try to see if I can find that paper online (no promises). I believe it was available on arXiv.
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#1621 by OnlyMe on 14 Oct, 2016 00:20
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...
Some while back I read a paper that was evaluating the practicality of sending a spaceship to another star system, at 0.2 c. They addressed the issue far better than I. I will try to see if I can find that paper online (no promises). I believe it was available on arXiv.
It would be a great contribution if you could provide a link for that reference ! (evaluating the practicality of sending a spaceship to another star system, at 0.2 c).
Thanks !
Is it this one?
https://arxiv.org/abs/1005.3833
https://www.technologyreview.com/s/419075/can-humanity-design-a-probe-capable-of-visiting-another-star/
http://icarusinterstellar.org/icarus-project-status
Sorry, no. I'll keep looking, but though I keep copies of almost every paper I read, so far I don't find in my archives.
Two things I can say are; first the main issue I noted in the paper was that they were concerned about physical degradation of the hull from impacts with interstellar dust and even atoms. They did conclude that, that could be resolved with engineering..., second they referred to the kinetic energy of the spaceship itself as representing? a fictitious element? I don't recall the exact way they put it, beyond the inclusion of the fictitious label. This last only by passive recall that came up reading through the discussion here. -
#1622 by rfmwguy on 14 Oct, 2016 00:26
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http://www.iepc2017.org/
Electric Propulsion conference every 2 years...next year in October in Atlanta...probably not ready for things like the EmDrive concept. -
#1623 by Rodal on 14 Oct, 2016 00:32
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Breakthrough Propulsion Workshop in Estes Park, Colorado, 2016 -- Courtesy of SSI.org
http://ssi.org/
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#1624 by dustinthewind on 14 Oct, 2016 01:19
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1.Found very strong TE013 in the new Bell geometry with circularizing antenna. All components are composed of a perfect conductor. Need to work on making just the large end a perfect conductor and the rest silver plated. FEKO's modeling abilities are limited, so I am using geometry imported from another app, which complicates things.
2 Questions about TE013 mode:
Why is the energy density always highest at the small end, what time-evolutions produces this?
Why does FEKO call kA/m a "surface current"? I think it should be the Magnetic field strength, H at the surface.
If it were a surface current it would have units of kA/m2, and for any TE mode, the value should be zero, because no magnetic flux is escaping the frustum. In order to drive current around the circumference of the frustum, it requires a NET flux through the loop. There is no NET flux if the flux is toroidal AND 100% inside the loop. The TE mode almost assures there are NO Lorentz forces acting on the frustum since there is no current flowing.
(Note, this is not the case for TM modes, where the magnetic flux is circular.)
Regarding my theory: If Shawyer's new patent is correct, then I probably have it backwards in my EM Drive Theory, because I said the power is dissipated at the big end, where he made the big end superconducting and the small end out of aluminum. This implies that the dissipation is happening at the small end, not the big end. Still, as it dissipates, it's weight moves toward the big end so the frustum can move forward.
I think essentially what I need is the energy density distribution throughout the frustum. Which can be derived from these images. It's just eps0E2.
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html
2.
http://www.ittc.ku.edu/~jstiles/220/handouts/Surface%20Current%20Density.pdf
See below...
How does one "measure" the wavelength in each of these Modes? From where to where?
Where would you say the center of mass of the field is located in each of these modes?
https://www.dropbox.com/s/3pho5edqu7qbcmr/Screen%20Shot%202016-10-13%20at%202.13.31%20PM.png?dl=0
Thanks!
Regarding the wavelength. I would guess there is a function that provides a multiplier at each coordinate along the axis which is constantly changing the length of lambda. For f*lambda=c either the frequency is changing for a constant velocity, the velocity is changing with constant frequency, or maybe the PV equations would apply which change both frequency and speed by the K value.I am not sure atm.A standing wave should have a constant frequency so I would guess the speed of light is changing. A group of B-field equal potential lines would cover a length of about 1/2 lambda. The first image is difficult to say judging only by 1/2 cycle so instead I would take the ratio of the separation of two equal potential lines near the big plate to the separation of the two same equal potential lines near the narrow end to get an idea of the difference in apparent wavelength multiplier. It is odd though, that compression of the magnetic field lines by the metal appear to shorten the wavelength. I'll have to think about that.
Center of mass for the field would have to do with how energy per volume is distributed over space. Integrated, the energy should be the same for both sides, at the center, I would guess.
I think TE modes eliminate static electric fields that appear from charge separation.
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.htmlQuoteBelow are images of the energy density, averaged over one cycle, on a cross-section through the cavity for the same three TM modes as used in our previous examples. The grey scales are normalised individually, so that white = the maximum energy density in each particular image.
The energy density he plots here makes me wonder if there is a way to rapidly shift modes using the same radiation which may then shift the center of mass rapidly. It reminds me of Shell's talking about shifting modes between TE and TM. It seems that would require a frequency change to change the center of mass though. The center of mass would come to a halt inside the cavity also. Maybe a mix between the modes? -
#1625 by lmbfan on 14 Oct, 2016 01:45
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The equation for the small end of the new patent frustum (with some help from Wolfram Alpha) is as follows:
x = ((a-y) sqrt(L^2-y^2))/y
Where the origin (x=0, y=0) is at the center of the big end, a is the distance from the origin to the apex of the cone, and L is the length of the cone segment. X increases along the radius of the big end, y increases from the big end to the small end.
Solving for y using just this equation is... messy. My intuition is that I will need to dust of my trig to get f(x). -
#1626 by Rodal on 14 Oct, 2016 02:45
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...
Some while back I read a paper that was evaluating the practicality of sending a spaceship to another star system, at 0.2 c. They addressed the issue far better than I. I will try to see if I can find that paper online (no promises). I believe it was available on arXiv.
It would be a great contribution if you could provide a link for that reference ! (evaluating the practicality of sending a spaceship to another star system, at 0.2 c).
Thanks !
Is it this one?
https://arxiv.org/abs/1005.3833
https://www.technologyreview.com/s/419075/can-humanity-design-a-probe-capable-of-visiting-another-star/
http://icarusinterstellar.org/icarus-project-status
Sorry, no. I'll keep looking, but though I keep copies of almost every paper I read, so far I don't find in my archives.
Two things I can say are; first the main issue I noted in the paper was that they were concerned about physical degradation of the hull from impacts with interstellar dust and even atoms. They did conclude that, that could be resolved with engineering..., second they referred to the kinetic energy of the spaceship itself as representing? a fictitious element? I don't recall the exact way they put it, beyond the inclusion of the fictitious label. This last only by passive recall that came up reading through the discussion here.
Is it this one ?
https://arxiv.org/abs/1608.05284
The interaction of relativistic spacecrafts with the interstellar medium
Thiem Hoang, A. Lazarian, Blakesley Burkhart, Abraham Loeb
It is a study funded by Breakthrough Starshot examining the impact of stray atoms, cosmic dust for spacecraft flying at 0.2 c
https://breakthroughinitiatives.org/Initiative/3 -
#1627 by OnlyMe on 14 Oct, 2016 03:40
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...
Some while back I read a paper that was evaluating the practicality of sending a spaceship to another star system, at 0.2 c. They addressed the issue far better than I. I will try to see if I can find that paper online (no promises). I believe it was available on arXiv.
It would be a great contribution if you could provide a link for that reference ! (evaluating the practicality of sending a spaceship to another star system, at 0.2 c).
Thanks !
Is it this one?
https://arxiv.org/abs/1005.3833
https://www.technologyreview.com/s/419075/can-humanity-design-a-probe-capable-of-visiting-another-star/
http://icarusinterstellar.org/icarus-project-status
Sorry, no. I'll keep looking, but though I keep copies of almost every paper I read, so far I don't find in my archives.
Two things I can say are; first the main issue I noted in the paper was that they were concerned about physical degradation of the hull from impacts with interstellar dust and even atoms. They did conclude that, that could be resolved with engineering..., second they referred to the kinetic energy of the spaceship itself as representing? a fictitious element? I don't recall the exact way they put it, beyond the inclusion of the fictitious label. This last only by passive recall that came up reading through the discussion here.
Is it this one ?
https://arxiv.org/abs/1608.05284
The interaction of relativistic spacecrafts with the interstellar medium
Thiem Hoang, A. Lazarian, Blakesley Burkhart, Abraham Loeb
It is a study funded by Breakthrough Starshot examining the impact of stray atoms, cosmic dust for spacecraft flying at 0.2 c
https://breakthroughinitiatives.org/Initiative/3
Your are good!
That is a paper I picked up a digital copy of recently and it does cover the interstellar dust issue.
Not what I was looking for or thought of as the source for treating the ship's kinetic energy as fictitious, however, after a brief review it may even be that it was the right paper that came to mind, but not where the issue of dismissing the ship's kinetic energy as fictitious originated. I will have to think and work on that a bit more.
For the time being, best anyone who cares should just take the fictiticious kinetic energy comments as my own and badly conveyed. -
#1628 by WarpTech on 14 Oct, 2016 03:58
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See below...
How does one "measure" the wavelength in each of these Modes? From where to where?
Where would you say the center of mass of the field is located in each of these modes?
https://www.dropbox.com/s/3pho5edqu7qbcmr/Screen%20Shot%202016-10-13%20at%202.13.31%20PM.png?dl=0
Thanks!
Regarding the wavelength. I would guess there is a function that provides a multiplier at each coordinate along the axis which is constantly changing the length of lambda. For f*lambda=c either the frequency is changing for a constant velocity, the velocity is changing with constant frequency, or maybe the PV equations would apply which change both frequency and speed by the K value.I am not sure atm.A standing wave should have a constant frequency so I would guess the speed of light is changing. A group of B-field equal potential lines would cover a length of about 1/2 lambda. The first image is difficult to say judging only by 1/2 cycle so instead I would take the ratio of the separation of two equal potential lines near the big plate to the separation of the two same equal potential lines near the narrow end to get an idea of the difference in apparent wavelength multiplier. It is odd though, that compression of the magnetic field lines by the metal appear to shorten the wavelength. I'll have to think about that.
Center of mass for the field would have to do with how energy per volume is distributed over space. Integrated, the energy should be the same for both sides, at the center, I would guess.
I think TE modes eliminate static electric fields that appear from charge separation.
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.htmlQuoteBelow are images of the energy density, averaged over one cycle, on a cross-section through the cavity for the same three TM modes as used in our previous examples. The grey scales are normalised individually, so that white = the maximum energy density in each particular image.
The energy density he plots here makes me wonder if there is a way to rapidly shift modes using the same radiation which may then shift the center of mass rapidly. It reminds me of Shell's talking about shifting modes between TE and TM. It seems that would require a frequency change to change the center of mass though. The center of mass would come to a halt inside the cavity also.
Interesting. So if we could shift frequencies from a mode where the CM is near the small end, to a frequency where the CM is near the big end, then the CM of the copper frustum should go the other way, such that the CM of the system doesn't move. Then allow the energy to dissipate before doing it again.
That could work, as long as the CM of the field doesn't oscillate back and forth. Then it's just a matter of how much mass can the field carry, which is just a matter of Q. Cool indeed!
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#1629 by dustinthewind on 14 Oct, 2016 04:08
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http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html
If we were in a half wavelength TE mode and flipped to a 1.5*lambda TM mode around 7 GHz I wonder if that might do the trick but I wonder if its the same thing Shell was doing. I find it interesting some modes have their energy density further ahead and compacted into a very small area.
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#1630 by meberbs on 14 Oct, 2016 04:37
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See below...
How does one "measure" the wavelength in each of these Modes? From where to where?
I have asked TheTraveller for a physical definition for guide wavelength, since the normal definition doesn't make sense in a resonating cavity, but he has yet to provide one. (He always just gives an equation with no associated physical meaning in response.)
I am not sure what you read but I am guessing that it was doing calculations in an accelerating reference frame, which requires "fictitious" forces that do "fictitious" work. Here is a paper that discusses this: https://arxiv.org/pdf/0803.2560.pdfSorry, no. I'll keep looking, but though I keep copies of almost every paper I read, so far I don't find in my archives.
Two things I can say are; first the main issue I noted in the paper was that they were concerned about physical degradation of the hull from impacts with interstellar dust and even atoms. They did conclude that, that could be resolved with engineering..., second they referred to the kinetic energy of the spaceship itself as representing? a fictitious element? I don't recall the exact way they put it, beyond the inclusion of the fictitious label. This last only by passive recall that came up reading through the discussion here.
Is it this one ?
https://arxiv.org/abs/1608.05284
The interaction of relativistic spacecrafts with the interstellar medium
Thiem Hoang, A. Lazarian, Blakesley Burkhart, Abraham Loeb
It is a study funded by Breakthrough Starshot examining the impact of stray atoms, cosmic dust for spacecraft flying at 0.2 c
https://breakthroughinitiatives.org/Initiative/3
Your are good!
That is a paper I picked up a digital copy of recently and it does cover the interstellar dust issue.
Not what I was looking for or thought of as the source for treating the ship's kinetic energy as fictitious, however, after a brief review it may even be that it was the right paper that came to mind, but not where the issue of dismissing the ship's kinetic energy as fictitious originated. I will have to think and work on that a bit more.
For the time being, best anyone who cares should just take the fictiticious kinetic energy comments as my own and badly conveyed.
The use of the word fictitious is unfortunate, because it is unrelated to the colloquial definition, and the forces themselves are quite real when you are in a rotating reference frame. The Coriolis force and centrifugal force are examples. Also this comic is related: https://xkcd.com/123/ -
#1631 by OnlyMe on 14 Oct, 2016 07:04
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See below...
How does one "measure" the wavelength in each of these Modes? From where to where?
I have asked TheTraveller for a physical definition for guide wavelength, since the normal definition doesn't make sense in a resonating cavity, but he has yet to provide one. (He always just gives an equation with no associated physical meaning in response.)
I am not sure what you read but I am guessing that it was doing calculations in an accelerating reference frame, which requires "fictitious" forces that do "fictitious" work. Here is a paper that discusses this: https://arxiv.org/pdf/0803.2560.pdfSorry, no. I'll keep looking, but though I keep copies of almost every paper I read, so far I don't find in my archives.
Two things I can say are; first the main issue I noted in the paper was that they were concerned about physical degradation of the hull from impacts with interstellar dust and even atoms. They did conclude that, that could be resolved with engineering..., second they referred to the kinetic energy of the spaceship itself as representing? a fictitious element? I don't recall the exact way they put it, beyond the inclusion of the fictitious label. This last only by passive recall that came up reading through the discussion here.
Is it this one ?
https://arxiv.org/abs/1608.05284
The interaction of relativistic spacecrafts with the interstellar medium
Thiem Hoang, A. Lazarian, Blakesley Burkhart, Abraham Loeb
It is a study funded by Breakthrough Starshot examining the impact of stray atoms, cosmic dust for spacecraft flying at 0.2 c
https://breakthroughinitiatives.org/Initiative/3
Your are good!
That is a paper I picked up a digital copy of recently and it does cover the interstellar dust issue.
Not what I was looking for or thought of as the source for treating the ship's kinetic energy as fictitious, however, after a brief review it may even be that it was the right paper that came to mind, but not where the issue of dismissing the ship's kinetic energy as fictitious originated. I will have to think and work on that a bit more.
For the time being, best anyone who cares should just take the fictiticious kinetic energy comments as my own and badly conveyed.
The use of the word fictitious is unfortunate, because it is unrelated to the colloquial definition, and the forces themselves are quite real when you are in a rotating reference frame. The Coriolis force and centrifugal force are examples. Also this comic is related: https://xkcd.com/123/
I do also have a copy of that paper and ran across it when trying to find where I came up with treating the kinetic energy of a spaceship as fictitious. But no cigars here either.
Really I think it best to leave things with the last sentence in my last post on the issue. Since January of this year I have been dealing with a situation that has had a significant impact on my ability, and perhaps the patience required, to spend the time and effort most of these papers deserve. Considering the circumstances it would not be unreasonable to assume that I might even at times have difficulty separating my own random associations while reading a technical paper or report with the report itself.
What I am getting at is that even though I have a clear memory of having read a report/paper that treated the kinetic energy of a spaceship as fictitious, I also recognize that it is entirely possible that, that is a false memory conflating my own random thoughts and extrapolations with the content of the paper I was reading at the time. In the future I will attempt to dig out the reference before posting, when possible.
I still feel that (without reference) the kinetic energy of a rocket (spaceship or even EMDrive), as defined from any frame of reference other than that of the rocket, has nothing to do with how the rocket's propulsion system functions. The rate and results of combustion are not affected by the rocket's velocity associated kinetic energy. -
#1632 by RERT on 14 Oct, 2016 09:08
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Monomorphic -
The comment that the fields in your simulation of Shawyer's new frustrum are above the breakdown potential gradient in dry air doesn't seem to have got a lot of airtime, but it does seem that the whole solution can't be valid because of that.
Are these runs being done with the cavity implicitly vacuum? Does FEKO allow the cavity to be filled with air as a dielectric, and can it compute the consequences of breakdown in that case? -
#1633 by RERT on 14 Oct, 2016 09:16
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Gilbertdrive -
I too considered that P/v might be a maximum for thrust, but dismissed the idea because I thought it was frame dependent. The only way I could see to have a thrust level low enough to be valid in any frame was to have thrust below P/c.
The frame dependence is most acute at low velocities: one can multiply P/v by large factors, with no material change to P from relativistic effects, just by changing to a frame moving at a few cm/s.
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#1634 by Gilbertdrive on 14 Oct, 2016 09:21
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I do also have a copy of that paper and ran across it when trying to find where I came up with treating the kinetic energy of a spaceship as fictitious. But no cigars here either.
Really I think it best to leave things with the last sentence in my last post on the issue. Since January of this year I have been dealing with a situation that has had a significant impact on my ability, and perhaps the patience required, to spend the time and effort most of these papers deserve. Considering the circumstances it would not be unreasonable to assume that I might even at times have difficulty separating my own random associations while reading a technical paper or report with the report itself.
What I am getting at is that even though I have a clear memory of having read a report/paper that treated the kinetic energy of a spaceship as fictitious, I also recognize that it is entirely possible that, that is a false memory conflating my own random thoughts and extrapolations with the content of the paper I was reading at the time. In the future I will attempt to dig out the reference before posting, when possible.
I still feel that (without reference) the kinetic energy of a rocket (spaceship or even EMDrive), as defined from any frame of reference other than that of the rocket, has nothing to do with how the rocket's propulsion system functions. The rate and results of combustion are not affected by the rocket's velocity associated kinetic energy.
Ask to the dinosaurians if the Kinetic energy of the asteroid that killed them was fictitious.
The Kinetic Energy is a given referential is very concrete when there is a collision.
For example, the Kinetic Energy of an asteroid in the earth referential is very relevant when the asteroid hit the earth.
If somebody shots on me, the Kinetic energy of the bullet in my reference frame will seem very relevant of my point of view.
The fact that the Kinetic Energy is frame dependent does not means at all that it is not very usefull, and relevant.
Anyway, in GR, everything has frame dependance. That is why the name of relativity because almost everything is relative to a reference frame.
The time is frame dependent.
The distances are frame dependent (an observer that cross the solar system at 0,9C will see smaller distances)
The speeds are frame dependent. (and that is because of that that the Kinetic Energy is frame dependant)
The relativistic mass are frame dependent.
The rest mass is not.
With your way of thinking, almost everything would be fictitious.
The only thing not fictitious that I could ask to a girl about her would be her rest mass. Not sure it is the best thing to do.
Also, it is true that the rate and results of combusion are not affected by the Kinetic Energy of a rocket, but that is taking the things in the wrong way. That is the Kinetic Energy of the rocket that is directly affected by the rate of the combustion. A sugar rocket will get less Kinetic Energy than a metane/Lox rocket.
That is also true that the consideration of the rocket alone in the earth referential is not adapted, you have to take into account the rocket propellant. -
#1635 by Gilbertdrive on 14 Oct, 2016 09:34
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Gilbertdrive -
I too considered that P/v might be a maximum for thrust, but dismissed the idea because I thought it was frame dependent. The only way I could see to have a thrust level low enough to be valid in any frame was to have thrust below P/c.
The frame dependence is most acute at low velocities: one can multiply P/v by large factors, with no material change to P from relativistic effects, just by changing to a frame moving at a few cm/s.
I do not claim that P/V is necessary a maximum for thrust. I claim 3 points.
1) No experiment showed more thrust than P/V, V taken in the laboratory reference frame.
2) If it is possible to gret more thrust than P/V in a laboratory, that it is a new way of producting energy. I do not postulate the Emdrive to be isolated, so I will not tell it is free energy. But it is at least a new energy bonanza.
3)If we admitt than thrust is constant for constant power, it would dismiss many theories. I do not see why to dismiss these theories, since 1). -
#1636 by RERT on 14 Oct, 2016 09:48
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RE: Universal Propulsion
I have to say I found this announcement overall negative. When Shawyer says he is working with a UK Aerospace Company, and it turns out to be a man with a garage and a lot of ambition instead of BAe or a similar corporation, I am disappointed. Firstly, no credibility is lent to his cause by his partner. Secondly, his earlier statement was accurate but misleading. I think this revelation moves my swing-o-meter a little towards the delusional/crooked end of the spectrum. He needs to be much more careful with his language - even 'small UK aerospace company' or 'UK aerospace startup' would have been much more honest.
I guess the one good point is that no-one will be arguing about spurious thermal effects if an EMDrone actually flies...
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#1637 by Gilbertdrive on 14 Oct, 2016 09:53
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RE: Universal Propulsion
True, but an effect type MHD would be still be possible. It would be at least a revolution on earth, but not necessarily usable in space.
I have to say I found this announcement overall negative. When Shawyer says he is working with a UK Aerospace Company, and it turns out to be a man with a garage and a lot of ambition instead of BAe or a similar corporation, I am disappointed. Firstly, no credibility is lent to his cause by his partner. Secondly, his earlier statement was accurate but misleading. I think this revelation moves my swing-o-meter a little towards the delusional/crooked end of the spectrum. He needs to be much more careful with his language - even 'small UK aerospace company' or 'UK aerospace startup' would have been much more honest.
I guess the one good point is that no-one will be arguing about spurious thermal effects if an EMDrone actually flies... -
#1638 by TheTraveller on 14 Oct, 2016 10:33
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I also do not beleive that Shawyer will give us flying cars in 2017.
What about a propellerless / jetless winged drone?
What order of magnitude for the weight of the jetless winged drone ? What order of thrust ?
Say 50kg thrust or 500N which at specific force 10, 000N/kWrf would need 50Wrf. -
#1639 by RERT on 14 Oct, 2016 10:38
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Well, it's friday morning, I swear nothing stronger than tea has passed my lips for more than 24 hours, and yet still I think it's about time to provoke some weekend fun, with a hypothesis 'du jour'.
1. The vacuum is not immutable
2. It is like a frictionless fluid which has both a local mass density and velocity field
3. Its mass density is almost entirely uniform, because non-uniformity dissipates very quickly
4. Consequently the net gravitational effect of the vacuum on any object is almost entirely nil, and the mass of the vacuum is undetectable in the lab.
5. The EMdrive works by transferring momentum to the vacuum, creating a 'flow' of massive vacuum.
6. However, the vacuum is special: we cannot detect motion through the vacuum. Once it is moving, it has 'dark momentum' - actually I quite like that name. 'dark momentum' is inherent in 'dark matter' after all...
7. Similarly, variations in the local mass-density of the vacuum on astronomical scales might account for 'dark matter'.
8. The EMdrive is propellant-less much like an Ocean Liner: it finds its reaction mass in its path. It is indeed not a rocket.
9. Gradients in the local velocity field of the vacuum caused by the EMdrive might cause local gravitational effects, which would be expected to dissipate quickly, much like the wake of a ship. However, a ship is not limited in its thrust to power ratio by the energy to momentum ratio of the waves which dissipate its wake. Nature takes as long as it needs to do that.
Anyway: I know this is not an 'explanation' of the EMdrive or Dark Matter, but it does have explanatory power and more than a hint of Occam's razor about it. When we look for dark matter and find nothing, the answer is obvious if slightly tautologous - 'nothing' has mass....
I guess now is when I'm told about the glaring mistake...
