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#1100
by
bmcgaffey20
on 29 Sep, 2016 06:25
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So if I understand correctly, the EMdrive acts like a mach effect device, by concentrating energy in high amounts in a small area to produce artificial gravity control through the acquisition of artificial mass? Because of E=MC2 that means a given amount of energy concentrated in a small area should have some affect with gravitation or mass... right? Basically if you "charge" up an emdrive with energy you can create artificial mass with a lopsided center of gravity with specific geometric shape.
If this is what is going on, it would be easy to test the affect. Photons with lower energy will show a lower effect, and photons of the gamma ray spectrum would be the highest energy and would have the highest effect if you could get them to reflect inside the frustum....
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#1101
by
meberbs
on 29 Sep, 2016 06:49
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I think the debate now is about whether a constant force producing a constant acceleration is even possible in classical mechanics regardless of the EmDrive. Some are suggesting it's not possible, that nature won't allow it because it runs into 'overunity'. Some say a true constant force will produce a gradually reduced acceleration. I find that position untenable.
emphasis mine.
No, no one has made that bolded statement (except maybe Shawyer), you keep turning what we are saying inside out and creating strawmen. (What has been said is that it takes increasing power to produce a constant force as the object accelerates, and no one has contested constant force = constant acceleration, because that is F = m*a)
A closed system that obeys the expression F = k * P (Force applied is directly proportional to Power applied, where k is a constant) is simply inconsistent with basic mechanics as it would break CoE, and the equation F*v = P, which comes from the basic definition of the terms. Therefore no such force can exist.** Rockets do not meet this description, but Shawyer's description of the emDrive does.
The Mach effect also does not meet this description (According to people who understand its principles better than me such as Rodal), but for some reason Woodward wrote a paper that makes it appear he doesn't understand the basic physics involved. Instead he could have just said "the Mach effect means the drive is not a closed system".
...With that said, I think any criticism of the third part of Woodward's Paper first has to explain why the Mach Effect transient mass fluctuation, as described by Woodward, either doesn't exist; or could not have the behavior described.
...
You are expecting criticism of the paper to answer things not said in the paper. The paper does not make the argument that F = k*P does not apply to the drive, and it does not describe any of the aspects of the Mach effect thruster that make it an open system, nor does it even mention transient mass fluctuations, let alone explain how those could resolve this issue as they are categorically different than normal expelling exhaust.
** Special relativity modifies this slightly, allowing the constant k to be up to 1/c due to 0 rest mass particles carrying momentum and energy.
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#1102
by
RERT
on 29 Sep, 2016 12:07
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I've always been ready to accept the the EMDrive breaks CoE if viewed as a closed system, but some parts of this discussion are most unintuitive.
Suppose we abandon any idea that the net force generated by the EMDrive is constant. Let's instead just assert that the change in kinetic energy is some fixed fraction of the electrical input power - the EMdrive is a device for turning electrical energy into kinetic energy. So
(dE/dt) = kP (equation 1)
Where E is the energy of the system, 0<k<1, and P is the input electrical power, and all items are measured in the rest frame of the device.
This seems profoundly unobjectionable: there is no free energy, in fact energy is always being dissipated in the rest frame of the device.
Where I get instantly stuck is as follows:
E = γmc² - the definition of relativistic energy
where 1/γ=√(1-v²/c²)
(dE/dt) = mc²dγ/dt = mc²(v/c²)γ³(dv/dt) = mvγ³(dv/dt) = 0 if v is 0
Now, this is purely related to the definition of gamma: and it requires (dE/dt) to be zero when v is zero, i.e. in the rest frame of the device. The equation is simpler without using special relativity, but the result is the same.
(dE/dt) = (d/dt) (½mv²) = mvdv/dt = 0 when v = 0
So despite appearing unobjectionable, the (Equation 1) can't happen!
If anyone can explain, or provide an analysis of the dynamics where equation 1 holds, or otherwise show me where I'm wrong, I would be very grateful.
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#1103
by
Fan Boi
on 29 Sep, 2016 13:07
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I don't believe the EM drive is a closed system. In my mind it is something like a ring-laser-gyroscope in that aspect: A closed device that still "feels" the entire universe, otherwise it wouldn't work (someone else pointed this one out earlier and I agree, kind of a rewording of the bucket argument).
My opinion on the constant force equals constant acceleration: The ship gains mass as it accelerates so the same force applied will continuously create less acceleration. If the ship is going fast enough it will have the same mass as Jupiter at some point and an EM drive pushing on Jupiter won't do much. Maybe that is oversimplified, not sure.
One more thought:
If you take a video of a glass falling off a table and breaking and you watch it backwards it still obeys the laws of physics. You only know you are watching it backwards because of an instinct.
If you take a video of a glass of ice melting and watch it backwards you observe heat going from cold to hot. You know you are watching it backwards because it no longer makes sense.
Maybe it is too earlier for an answer but: If you take a video of an EM drive in action and you could somehow play it backwards, will it still make sense?
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#1104
by
birchoff
on 29 Sep, 2016 13:52
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So if I understand correctly, the EMdrive acts like a mach effect device, by concentrating energy in high amounts in a small area to produce artificial gravity control through the acquisition of artificial mass? Because of E=MC2 that means a given amount of energy concentrated in a small area should have some affect with gravitation or mass... right? Basically if you "charge" up an emdrive with energy you can create artificial mass with a lopsided center of gravity with specific geometric shape.
If this is what is going on, it would be easy to test the affect. Photons with lower energy will show a lower effect, and photons of the gamma ray spectrum would be the highest energy and would have the highest effect if you could get them to reflect inside the frustum....
First, the EmDrive may or may not be governed by Mach Effects. The only reason it has come up in this thread is because at the SSI workshop it was offered as a possible explanation for the anomalous thrust that has been measured.
Now if it was proven or assumed that the EmDrive is governed by Mach Effects then it would mean that within the EmDrive the following is happening. Either one part of, or the entire internal cavity of the EmDrive is having its Mass fluctuate. This fluctuation only changes the mass of one part of or the entire internal cavity of the EmDrive. To get unidirectional force you would also need a force applied against the fluctuating mass when it is heavier and when it is lighter. In Woodward's MET devices this is triggered via the electrostrictive property of the stack his devices are built out of. I believe there was a recent discussion on this forum about how the same thing can happen within a copper frustum. In addition, I believe Paul March mentioned the same thing on this forum a while back (somewhere in the first couple of threads, IIRC).
This doesn't mean an EmDrive is governed by Mach Effects it just means it could be and if it was, you would expect to find something mimicking the process laid out above going on inside the Frustum.
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#1105
by
birchoff
on 29 Sep, 2016 14:08
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Hey, does anyone know of a timeframe to look forward to seeing the proceedings from the SSI Workshop? Not asking for an exact date just would like a possible date range to pencil into my mental calendar.
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#1106
by
HMXHMX
on 29 Sep, 2016 14:24
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Hey, does anyone know of a timeframe to look forward to seeing the proceedings from the SSI Workshop? Not asking for an exact date just would like a possible date range to pencil into my mental calendar.
Since all the work is being done by volunteers, and involves transcribing several different audio tracks, identifying questions and comments speakers by voice, cleaning up video problems (we lost our original videographer due to an injury two days before the event) and a lot of other boring work, I'm reluctant to give a schedule. (Also, just to manage expectations, the video is archival, not "TED" like quality.) Finally, the technical committee needs to get everyone's papers for the proceedings, and I believe they have given a deadline of early December for that submittal, prior to layout of the final proceedings hardcopy and PDFs.
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#1107
by
birchoff
on 29 Sep, 2016 15:13
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Hey, does anyone know of a timeframe to look forward to seeing the proceedings from the SSI Workshop? Not asking for an exact date just would like a possible date range to pencil into my mental calendar.
Since all the work is being done by volunteers, and involves transcribing several different audio tracks, identifying questions and comments speakers by voice, cleaning up video problems (we lost our original videographer due to an injury two days before the event) and a lot of other boring work, I'm reluctant to give a schedule. (Also, just to manage expectations, the video is archival, not "TED" like quality.) Finally, the technical committee needs to get everyone's papers for the proceedings, and I believe they have given a deadline of early December for that submittal, prior to layout of the final proceedings hardcopy and PDFs.
Sounds like I should table any plans to do some light reading till next year. While keeping my ear to the ground for any changes. Thats fine. Just trying to set my own expectations.
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#1108
by
dustinthewind
on 29 Sep, 2016 15:46
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I found this article interesting and possibly relevant to this discussion: http://phys.org/news/2016-09-antimatter-lasers.html
Note this statement: "A key concept behind the team's work is based on the quantum electrodynamics (QED) prediction that "a strong electric field can, generally speaking, 'boil the vacuum,' which is full of 'virtual particles,' such as electron-positron pairs," explained Igor Kostyukov of IAP RAS. "The field can convert these types of particles from a virtual state, in which the particles aren't directly observable, to a real one."
Wow, thanks for sharing this. I'm looking forward to reading about this. It sounds a lot like what I was thinking about the vacuum and possibly indicating some of the concepts Richard Feynman and Wheeler were suggesting.
I thought so too. If those virtual particles can become real particles then you can push on them in some way I would think. But even then, why no exhaust of these now real particles? Could they become real for only a brief moment and then become virtual again?
The problem is, it takes an electric field of a billion-billion volts per meter to do it!
https://en.wikipedia.org/wiki/Schwinger_limit
It only happens on the scale of electrons and charged sub-atomic particles.
I was speculating if light it self is a disturbance of the very fabric of our universe or these pairs. These pairs would appear to have zero rest mass, similar to light. If they become sufficiently separated (maybe a plank length) and they appear to gain mass as light appears to carry momentum by the energy it has. matter/anti-matter pairs might be the mechanism of how the mass of light could change. The disturbance of the anti-mater particle as light, if it is negative mass running in reverse time (resulting in positive mass till its time is canceled by the positive mass) could provide a mechanism for signals to go backwards in time as in the Feynman diagrams and the mach effect. Maybe it isn't necessary to separate them to the point we have full fledged electron-positron pairs. Maybe we could still keep it in the linear range, but just separate them enough to modify the mass of the light sufficiently such that a back reaction results on the pairs from the reflection of heavier light in the cavity on one side. After many reflections energy would effectively be transferred to the cavity from the many interactions of the light.
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#1109
by
gustavo
on 29 Sep, 2016 16:37
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Recently, I was thinking about the nature of reciprocity in some cases of natural phenomenon, for example, Newtons Thrid Law of Motion, or, Faraday's law of induction.
Considering that spacetime distortion, due to a gravity field, leads to a change in the light path, or, a change in light velocity, when observed from a region with diferent spacetime metric.
Would a induced change in light velocity, induce a distorion in spacetime (to keep c constant at local reference), thus, generating gravity?
It's the opposite direction of:
Mass > Gravity > Spacetime distortion > Light distortion.
Where, a induced light distortion would create:
Light distortion > Spacetime distortion > Gravity
Note that the spacetime warp would happen because c must be constant.
I can explain it better later, but right now I dont have much time.
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#1110
by
Bob012345
on 29 Sep, 2016 17:28
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I think the debate now is about whether a constant force producing a constant acceleration is even possible in classical mechanics regardless of the EmDrive. Some are suggesting it's not possible, that nature won't allow it because it runs into 'overunity'. Some say a true constant force will produce a gradually reduced acceleration. I find that position untenable.
emphasis mine.
No, no one has made that bolded statement (except maybe Shawyer), you keep turning what we are saying inside out and creating strawmen. (What has been said is that it takes increasing power to produce a constant force as the object accelerates, and no one has contested constant force = constant acceleration, because that is F = m*a)
A closed system that obeys the expression F = k * P (Force applied is directly proportional to Power applied, where k is a constant) is simply inconsistent with basic mechanics as it would break CoE, and the equation F*v = P, which comes from the basic definition of the terms. Therefore no such force can exist.** Rockets do not meet this description, but Shawyer's description of the emDrive does.
The Mach effect also does not meet this description (According to people who understand its principles better than me such as Rodal), but for some reason Woodward wrote a paper that makes it appear he doesn't understand the basic physics involved. Instead he could have just said "the Mach effect means the drive is not a closed system".
...With that said, I think any criticism of the third part of Woodward's Paper first has to explain why the Mach Effect transient mass fluctuation, as described by Woodward, either doesn't exist; or could not have the behavior described.
...
You are expecting criticism of the paper to answer things not said in the paper. The paper does not make the argument that F = k*P does not apply to the drive, and it does not describe any of the aspects of the Mach effect thruster that make it an open system, nor does it even mention transient mass fluctuations, let alone explain how those could resolve this issue as they are categorically different than normal expelling exhaust.
** Special relativity modifies this slightly, allowing the constant k to be up to 1/c due to 0 rest mass particles carrying momentum and energy.
Ok, I understand the difference. You're saying it takes an increasing power (electric) to maintain a constant force. If I'm accelerating an object with a rail gun that would seem to be the case but I'm providing a force in a fixed frame. But there are ways of applying a fixed force at a fixed power in an accelerating frame. Photon beam propulsion does provide a fixed force at a fixed power up to relativistic speeds or at least relativistic effects limit things. And rockets certainly do provide a constant thrust for a constant power, for a limited time. So that disproves your asserting that such a constant force at constant power is outside the bounds of classical mechanics. The confusion is because the rocket applies it's thrust in a constantly accelerating reference frame and normal simpler mechanical systems apply a force from a fixed reference frame. That makes all the difference.
You also make a point about a 'closed' system. Shawyer claims the EmDrive is open, as does Woodward about his device.
Would you agree with this: If an EmDrive works at all, making a constant force in some frame, then it would keep accelerating as long as power were applied. Agree? If not you should at least admit an EmDrive up to k=2/c. But I've already shown photon recycling can break the 2/c limit. Thanks.
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#1111
by
Bob012345
on 29 Sep, 2016 17:48
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I started thinking about this topic the other way around and was wondering if there any comments. Suppose you locate a comet making it's way through the solar system at 100,000 MPH. Using convention rockets to match speeds we send up a very small EM device and attach it to the comet facing it's direction of travel and turn it on (battery powered for this thought experiment). Will it eventually scrub off speed from the comet while at the same time making copious amounts of electricity? Could the EM drive works "both ways"? It would seem to me that if the EM drives works it will scrub speed off the comet (simple retro-rocket), but what consequence for what is happening inside the EM device?
I doubt that. I think it would take power to slow something down just as it takes power to accelerate something.
Consider going to a distant planet to explore. You want to speed up then slow down and stop. Both take power.
The more I read that the more awkward it appears. What I was trying to say is:
The EM drive seems to convert electrical energy into kinetic energy without a reaction mass, but is their a configuration where it does the opposite? (I am not even sure what 'opposite' means in this context, but thought I would put it out there).
That is a very good way of looking at the problem. A few years ago I had the same idea with another device I was experimenting with. Any electromagnetic machine should operate as a generator or a motor. The other constraint I had to consider was the CoE conundrum. However this is easily seen in electromagnets: It is easy to move a strong magnet slowly across a thick Copper plate. When you attempt to move it quickly the resistance due to increased eddy currents makes it very hard. A lot of physical phenomena are reversible when the conditions are right. Most chemical equations are shown with the ⇔ operator. An electrodynamic tether is one example of propellantless propulsion that is reversible. When the induced current along the tether is used to charge batteries or just dissipated as heat the spacecraft drops to a lower orbit and has less kinetic energy. This has been proposed as a method for de-commisioning satellites. However before this "generator" mode of an EM-Drive is considered there are many prerequsites. No one to my knowledge has built an EM-Drive with a fustrum that was self-oscillating. By that I mean a cavity oscillator configuration. If you had a self-oscillating cavity would it generate RF energy if momentum was added to it? The doppler shift theory is not credible. If it were satellites would change their orbits whenever RF was transmitted to the ground,
No-one caught the error in my earlier post with the CoE equations. If you graphed ΔKe = (F2Δt)/(2M) and P = WΔt = (FΔt)/Kc they would both be straight lines; no parabola. However they do have different slopes. If the power applied to the EM-Drive was doubled, resulting in twice the force, the rate of change of its kinetic energy would increase by 4.
The only reason why this CoE conundrum exists is because it is claimed an EM-Drive produces a constant force for some constant input power. If this condition is relaxed and we say the force produced by any reactionless drive must decrease over time so as to satisfy CoE when a constant input power is applied it might be possible to make better theoretical progress.
The EmDrive is equivalent to a rocket operating in a regime where the thrust is constant and the chemical power is constant but instead of running out of mass quickly, it never does. If you relax the condition, you don't gain much because it would then take such immense energy storage to get to the nearest star for example, that even with nuclear, you'll never get reasonable accelerations.
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#1112
by
Bob012345
on 29 Sep, 2016 17:56
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Recently, I was thinking about the nature of reciprocity in some cases of natural phenomenon, for example, Newtons Thrid Law of Motion, or, Faraday's law of induction.
Considering that spacetime distortion, due to a gravity field, leads to a change in the light path, or, a change in light velocity, when observed from a region with diferent spacetime metric.
Would a induced change in light velocity, induce a distorion in spacetime (to keep c constant at local reference), thus, generating gravity?
It's the opposite direction of:
Mass > Gravity > Spacetime distortion > Light distortion.
Where, a induced light distortion would create:
Light distortion > Spacetime distortion > Gravity
Note that the spacetime warp would happen because c must be constant.
I can explain it better later, but right now I dont have much time.
Paraphrasing a rather drunk Cmdr. Deanna Troi: "Time? This is no time to talk about time. We don't have the time!... What was I saying?"
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#1113
by
Tellmeagain
on 29 Sep, 2016 18:14
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Ok, I understand the difference. You're saying it takes an increasing power (electric) to maintain a constant force. If I'm accelerating an object with a rail gun that would seem to be the case but I'm providing a force in a fixed frame. But there are ways of applying a fixed force at a fixed power in an accelerating frame. Photon beam propulsion does provide a fixed force at a fixed power up to relativistic speeds or at least relativistic effects limit things. And rockets certainly do provide a constant thrust for a constant power, for a limited time. So that disproves your asserting that such a constant force at constant power is outside the bounds of classical mechanics. The confusion is because the rocket applies it's thrust in a constantly accelerating reference frame and normal simpler mechanical systems apply a force from a fixed reference frame. That makes all the difference.
...SNIPPED
This understanding is not correct, "rocket applies it's thrust in a constantly accelerating reference frame". Actually rocket applies it's thrust in an inertial reference frame. In the "constantly accelerating reference frame" (I assume you are talking about the rocket itself as a frame) there is no thrust, because there is no acceleration. In an inertial reference frame, the rocket equation can be derived as
F(external force)=Ma+(v(of rocket)-v(of exhaust))dM/dt. This equation is good for any inertial reference frame. For rocket that does not experience external force (air drag, gravity, etc), the equation becomes Ma=(v(of rocket)-v(of exhaust))(-dM/dt). This right side is just the thrust, and it is with any inertial reference frame, and not with the constantly accelerating reference frame. For details you can see my discussion in the pdf file ( Woodward_updated.pdf , in section III) downloadable in this post,
http://forum.nasaspaceflight.com/index.php?topic=40959.msg1589319#msg1589319
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#1114
by
gustavo
on 29 Sep, 2016 18:19
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Recently, I was thinking about the nature of reciprocity in some cases of natural phenomenon, for example, Newtons Thrid Law of Motion, or, Faraday's law of induction.
Considering that spacetime distortion, due to a gravity field, leads to a change in the light path, or, a change in light velocity, when observed from a region with diferent spacetime metric.
Would a induced change in light velocity, induce a distorion in spacetime (to keep c constant at local reference), thus, generating gravity?
It's the opposite direction of:
Mass > Gravity > Spacetime distortion > Light distortion.
Where, a induced light distortion would create:
Light distortion > Spacetime distortion > Gravity
Note that the spacetime warp would happen because c must be constant.
I can explain it better later, but right now I dont have much time.
Paraphrasing a rather drunk Cmdr. Deanna Troi: "Time? This is no time to talk about time. We don't have the time!... What was I saying?"
Hahahaha, oh man, this reminds me of a physics professor back in my college days.
But hey, we know (do we?) that there are wavelength variations inside a frustrum cavity, and some months ago, the White–Juday warp-field interferometer gave positive results (positive and repeatable?) for the warp effect inside of the EmDrive... Just saying...
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#1115
by
Tellmeagain
on 29 Sep, 2016 18:49
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Ok, I understand the difference. You're saying it takes an increasing power (electric) to maintain a constant force. If I'm accelerating an object with a rail gun that would seem to be the case but I'm providing a force in a fixed frame. But there are ways of applying a fixed force at a fixed power in an accelerating frame. Photon beam propulsion does provide a fixed force at a fixed power up to relativistic speeds or at least relativistic effects limit things. And rockets certainly do provide a constant thrust for a constant power, for a limited time. So that disproves your asserting that such a constant force at constant power is outside the bounds of classical mechanics. The confusion is because the rocket applies it's thrust in a constantly accelerating reference frame and normal simpler mechanical systems apply a force from a fixed reference frame. That makes all the difference.
...SNIPPED
This understanding is not correct, "rocket applies it's thrust in a constantly accelerating reference frame". Actually rocket applies it's thrust in an inertial reference frame. In the "constantly accelerating reference frame" (I assume you are talking about the rocket itself as a frame) there is no thrust, because there is no acceleration. In an inertial reference frame, the rocket equation can be derived as
F(external force)=Ma+(v(of rocket)-v(of exhaust))dM/dt. This equation is good for any inertial reference frame. For rocket that does not experience external force (air drag, gravity, etc), the equation becomes Ma=(v(of rocket)-v(of exhaust))(-dM/dt). This right side is just the thrust, and it is with any inertial reference frame, and not with the constantly accelerating reference frame. For details you can see my discussion in the pdf file ( Woodward_updated.pdf , in section III) downloadable in this post,
http://forum.nasaspaceflight.com/index.php?topic=40959.msg1589319#msg1589319
Professor Woodward derived the rocket equation from F=dp/dt=d(Mv)=Mdv/dt+vdM/dt, where he implicitly talked about the v in Mdv/dt as relative to an inertial frame but the v in vdM/dt as relative to the rocket. This kind of derivation is incorrect. What dp/dt=Mdv/dt+vdM/dt means physically needs careful analysis. We can not mindlessly apply chain rule of derivative to dp/dt without knowing what it really means. They way I used in my pdf file causes no confusion.
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#1116
by
wicoe
on 29 Sep, 2016 19:09
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Photon beam propulsion does provide a fixed force at a fixed power up to relativistic speeds or at least relativistic effects limit things.
Another limiting factor for a photon rocket is the final mass. A photon rocket converts mass into the energy of photons. Sooner or later it will run out of "fuel" mass, likely well before relativistic effects come into play. The formula can be found here:
https://en.wikipedia.org/wiki/Photon_rocket
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#1117
by
OnlyMe
on 29 Sep, 2016 19:41
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....
My opinion on the constant force equals constant acceleration: The ship gains mass as it accelerates so the same force applied will continuously create less acceleration. If the ship is going fast enough it will have the same mass as Jupiter at some point and an EM drive pushing on Jupiter won't do much. Maybe that is oversimplified, not sure.
....
The mass of an object is always defined in its own frame of reference. A rock does not gain mass when it is thrown.
The confusion most often begins with the term "
relativistic mass" which is misleading unless you pay attention to the
relativistic qualifier, which restricts it to some preferred frame of reference, usually an inertial frame associate with the lab or say the earth itself. The term encompasses an object's rest mass and its kinetic energy/momentum. The kinetic energy/momentum is dependent on the frame of reference it is being compared to..., usually whatever it is going to collide with.
When discussing the EmDrive, a satellite or spaceship, once it has reached an escape velocity or greater, and is outside the atmosphere of a planet, the planet and its gravity well are no longer significant issues, relative to continued acceleration.
Once you set aside gravity and for simplicity sake, things like how frame dragging, in the larger contexts of the solar system and even galaxy, what may be important are things like the composition of the quantum vacuum and how it might interact with massive objects.
I for one believe that if EM waves inside a can can make it move, then the EM waves outside the can that it moves relative to, have to be considered as producing at least a potential resistance to that motion... And that resistance should scale relativistically. If so even if you get a constant thrust for a constant expenditure of energy, the acceleration would not be constant/uniform. At classical velocities it may appear so, but ultimately the discussion assumes relativistic velocities.
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#1118
by
birchoff
on 29 Sep, 2016 20:41
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...
...With that said, I think any criticism of the third part of Woodward's Paper first has to explain why the Mach Effect transient mass fluctuation, as described by Woodward, either doesn't exist; or could not have the behavior described.
...
You are expecting criticism of the paper to answer things not said in the paper. The paper does not make the argument that F = k*P does not apply to the drive, and it does not describe any of the aspects of the Mach effect thruster that make it an open system, nor does it even mention transient mass fluctuations, let alone explain how those could resolve this issue as they are categorically different than normal expelling exhaust.
** Special relativity modifies this slightly, allowing the constant k to be up to 1/c due to 0 rest mass particles carrying momentum and energy.
I agree that none of those things are mentioned. However, it is the lack of mentioning those things that I believe has lead to a lot of the criticisms of that said paper. Context is very important. I have had this discussion about Woodward's refutation of over unity paper at least three times now. And every time I am left with the impression that either the critique didn't completely read the paper or their interpretation is completely different from mine. Each time it ends up being the interpretation and once you prod you realize is that there is a mismatch in expectations. Given the title, I think critiques expected a straightforward well laid out argument for why devices governed by ME are open systems and how momentum transfer occurs so as not to violate CoM/CoE. Instead what that paper does from the outset, is state that devices governed by ME ARE SIMPLE MECHANICAL SYSTEMS. For a critic that isn't convinced of this statement, there are no references to previous papers included at the end to help them come to terms with that statement. After that statement is made, Woodward proceeds to explain why OverUnity in Simple Mechanical systems cannot occur. Then launches in on why he supposes his critiques make the mistake he says is not possible. Then finishes up with a description of how one should do the calculation for a device governed by ME. If I hadn't invested enough time to read most of the papers they have put out and engaged in discussions with other followers of ME about how it works. I have zero doubt I would take the same position as many critics of the paper have made. When there are a bunch of papers he has published that do a good job going into the description of how his MET's work.
However, once you understand the idea Woodward is proposing with Mach Effect Theory. Then I would strongly argue that the first 3/4 of the paper makes sense. the last 1/4 is still a little problematic for me personally but that's because I don't know if the description he provides at the end is enabled by the mass fluctuations taking place in the MET. I suspect that is the case; since the kinetic energy of the internals of the MET device would be very different from the rest of the ship it is propelling.
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#1119
by
birchoff
on 29 Sep, 2016 21:18
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Ok, I understand the difference. You're saying it takes an increasing power (electric) to maintain a constant force. If I'm accelerating an object with a rail gun that would seem to be the case but I'm providing a force in a fixed frame. But there are ways of applying a fixed force at a fixed power in an accelerating frame. Photon beam propulsion does provide a fixed force at a fixed power up to relativistic speeds or at least relativistic effects limit things. And rockets certainly do provide a constant thrust for a constant power, for a limited time. So that disproves your asserting that such a constant force at constant power is outside the bounds of classical mechanics. The confusion is because the rocket applies it's thrust in a constantly accelerating reference frame and normal simpler mechanical systems apply a force from a fixed reference frame. That makes all the difference.
...SNIPPED
This understanding is not correct, "rocket applies it's thrust in a constantly accelerating reference frame". Actually rocket applies it's thrust in an inertial reference frame. In the "constantly accelerating reference frame" (I assume you are talking about the rocket itself as a frame) there is no thrust, because there is no acceleration. In an inertial reference frame, the rocket equation can be derived as
F(external force)=Ma+(v(of rocket)-v(of exhaust))dM/dt. This equation is good for any inertial reference frame. For rocket that does not experience external force (air drag, gravity, etc), the equation becomes Ma=(v(of rocket)-v(of exhaust))(-dM/dt). This right side is just the thrust, and it is with any inertial reference frame, and not with the constantly accelerating reference frame. For details you can see my discussion in the pdf file ( Woodward_updated.pdf , in section III) downloadable in this post,
http://forum.nasaspaceflight.com/index.php?topic=40959.msg1589319#msg1589319
Professor Woodward derived the rocket equation from F=dp/dt=d(Mv)=Mdv/dt+vdM/dt, where he implicitly talked about the v in Mdv/dt as relative to an inertial frame but the v in vdM/dt as relative to the rocket. This kind of derivation is incorrect. What dp/dt=Mdv/dt+vdM/dt means physically needs careful analysis. We can not mindlessly apply chain rule of derivative to dp/dt without knowing what it really means. They way I used in my pdf file causes no confusion.
I didn't ask this in my previous comment on your report. But can you point out where Woodward actually does a derivation of the Rocket Equation, because in the paper all he does is state the Rocket Equation as you have done. Then talk about the differences between the force represented by the Ma term which you have rewritten as Mdv/dt and the vdM/dt term. This is specifically done to call out the situation where if the mass change of a vehicle is perpendicular to the motion of that vehicle does it affect the velocity of that vehicle. I don't see any derivation being done here more an interpretation of what the terms in the equations mean physically. with the question about the effect of motion on the vehicle being left to the reader to answer. Which I said seems to have been done because in a MET there is a component whose mass is actively being changed, as the Mach Effect Transient mass fluctuation is triggered. Since this is explained as an interaction with the rest of the mass of the far universe, via a gravitational version of absorber theory. I do not think it a stretch that he also believes the mass change in a MET also occurs perpendicular to the motion of the vehicle a MET is propelling.
