According to the discussion on talk-polywell, White's QVF theory says that Shawyer's drive should work.
Quote from: JohnFornaro on 11/11/2012 01:46 pmQuote from: 93143 on 11/11/2012 07:37 amQuote from: JohnFornaro on 11/10/2012 02:39 pmYou can't get more energy out of the deceleration than you applied during the acceleration.Sure you can. All you need to do is fly through an electromagnetic decelerator instead of using the thruster. Is this not what the Prius does, when braking downhill? And after your journey over hill and dale, don't you have to fill it up with gas again? Because of entropy?Partly because of entropy - that's why the gas engine isn't 100% efficient. But even if it were, and if the electric motor operation and reclamative braking were 100% efficient, and the batteries didn't leak at all, and there were no frictional or air resistance or rolling resistance losses, you would still not end the journey with more stored energy than you had at the start.This is because the energy required to produce a certain amount of thrust depends on the speed of the vehicle, so no matter how fast you go, it takes at least as much energy to get that fast as you can theoretically get by slowing back down. Basic Newtonian mechanics.
Quote from: 93143 on 11/11/2012 07:37 amQuote from: JohnFornaro on 11/10/2012 02:39 pmYou can't get more energy out of the deceleration than you applied during the acceleration.Sure you can. All you need to do is fly through an electromagnetic decelerator instead of using the thruster. Is this not what the Prius does, when braking downhill? And after your journey over hill and dale, don't you have to fill it up with gas again? Because of entropy?
Quote from: JohnFornaro on 11/10/2012 02:39 pmYou can't get more energy out of the deceleration than you applied during the acceleration.Sure you can. All you need to do is fly through an electromagnetic decelerator instead of using the thruster.
You can't get more energy out of the deceleration than you applied during the acceleration.
Sure you can.
The proposed thruster doesn't appear to have that limitation, which implies that its operating principle is something weird, that may lead to an entropy principle violation or even a conservation violation.
Isn't the efficiency term where entropy is factored in?
It's where entropy is generated. But the Second Law of Thermodynamics provides no reason why η needs to be below unity in principle, because the described system is not a heat engine. And there is certainly no fundamental physical reason η needs to be low enough to prevent local over-unity operation of the described system given an arbitrarily high vehicle speed.
Quote from: 93143There are better ways; they involve rotation...I don't get what point you are trying to make.
There are better ways; they involve rotation...
Basically that the linear acceleration/deceleration system you and I described is monstrously impractical for energy generation, and a steady-state rotating system might be a better plan.
Somebody tell me that my summary of the EM Drive, and the ME drive is incorrect: You put electricity into it, and then it moves forward. ... I also don't seem to grasp how kinetic energy is apparently not related to momentum.
You can't turn electrical energy into kinetic energy without throwing something away...You have to push on something, and it can't be yourself. Newton's Third Law. All of this discussion turns on that.Cars push on the road. Rockets push on their propellant. M-E thrusters (if they work) push on the rest of the observable universe...
Woodward and all claim that the ME device pushes against the frame of rest of the universe, and state that they have derived a mathematical model which correctly restates the idea of action at a distance to support their thesis.
...but since their behaviour seems to be independent of velocity or at least orientation this has some interesting theoretical consequences.
It isn't yet clear what this EM-Drive is supposed to push on.
Shawyer maintains that there is a causal relationship between the group velocity of a wave thru matter, and the actual momentum of the matter, and that he can manipulate it so that there is a preferential direction of momentum. It appears to violate the conservation of momentum...
Also, both momentum and kinetic energy are frame-dependent, but to different powers, while other forms of energy are not frame-dependent. This messes naïve attempts at equivalence right the #### up.
Energy being the capacity to do work, it might make more sense to consider kinetic energy not as inherent in the velocity of a moving object, but rather as inherent in the difference in velocities between two objects. If everything is moving at the same velocity, there's no capacity to do work involved no matter what reference frame you pick.
Posted on talk-polywell:http://www.emdrive.com/yang-juan-paper-2012.pdf
This paper uses a nationally patented device - the rocket indifferent equilibrium thrust measurement device - to measure the propellantless microwave thruster net thrust. Thus further experimentally verifying the feasibility of the practical microwave propulsion device.
Wait a sec. Didn't I say that you can't get more energy out of deceleration than you put in during acceleration? Can you explain what this exchange below means?Quote from: MeYou can't get more energy out of the deceleration than you applied during the acceleration.Quote from: YouSure you can.Quote from: 93143The proposed thruster doesn't appear to have that limitation, which implies that its operating principle is something weird, that may lead to an entropy principle violation or even a conservation violation. Why'd you say "Sure you can [get more energy out of deceleration than you put in during acceleration]"?
Quote from: 93143It's where entropy is generated. But the Second Law of Thermodynamics provides no reason why η needs to be below unity in principle, because the described system is not a heat engine. And there is certainly no fundamental physical reason η needs to be low enough to prevent local over-unity operation of the described system given an arbitrarily high vehicle speed.Thanks for trying, but if eta is over-unity in a locally operated system, it means that the system is using energy. On these various thrustors, that energy comes from the wall socket, AIUI. So, I'm not sure what point you would be making here.
Quote from: JFQuote from: 93143There are better ways; they involve rotation...I don't get what point you are trying to make.Quote from: 93143Basically that the linear acceleration/deceleration system you and I described is monstrously impractical for energy generation, and a steady-state rotating system might be a better plan.Well, fine, but eta is still and always less than unity. No free lunch and all that.
Quote from: 93143...but since their behaviour seems to be independent of velocity or at least orientation this has some interesting theoretical consequences.Hence the thread... Go on...
Quote from: 93143Energy being the capacity to do work, it might make more sense to consider kinetic energy not as inherent in the velocity of a moving object, but rather as inherent in the difference in velocities between two objects. If everything is moving at the same velocity, there's no capacity to do work involved no matter what reference frame you pick.An interesting sidetrack, to be sure. Not clear to me how it applies to this.
Quote from: 93143 on 11/11/2012 10:35 pmhttp://www.emdrive.com/yang-juan-paper-2012.pdfThis paper appears to be a translation of the one written in Chinese, and posted earlier. It cannot be considered a peer reviewed paper.
http://www.emdrive.com/yang-juan-paper-2012.pdf
a device such as is being discussed/postulated/assumed in this thread - a propellantless thruster with a velocity-independent thrust-to-power ratio.
Kinetic energy (as defined for a single object at a single velocity) is frame-dependent, while electrical energy is not. In order to allow conversion of the one into the other, without reacting against anything, either the amount of electrical energy being used or the efficiency of the thruster would have to be quadratically related to the observer's reference frame, which is silly.
Being able to get more energy out of deceleration than you put in during acceleration is entirely contingent on the acceleration (but not the deceleration) being done by a device such as is being discussed/postulated/assumed in this thread - a propellantless thruster with a velocity-independent thrust-to-power ratio.
The only assumption required here is that the performance of the thruster doesn't depend on how fast it's going. This is unprecedented for a propellantless device, and the result is locally-apparent free energy. You cannot invoke conservation of energy to eliminate this result as you seem to be trying to do, because the problem is already fully specified.
Kinetic energy (as defined for a single object at a single velocity) is frame-dependent, while electrical energy is not.
The first part I get. I'm travelling in the same direction and the same velocity as the speeding bullet. I reach out my hand, NEO style, and pick the bullet up, and send it elsewhere. Me and the bullet are in the same frame. If me and the bullet hit the brick wall, stationary in our frame of reference, we go splat.Electrical energy is different, always speeding around at more or less the speed of light; a constant, no matter the frame of reference. So I sorta get that part as well. Still hazy on the link (or lack of link) between the "mechanical", "framed" kinetic energy of a massy "thing", and the "frame" of an electrical energy wave.These experimenters claim that they can take that electricity out of its frame, and direct it to mass in another arbitrary frame of reference.Executive summary: I'm not following you.
Well, if it works, there's two possibilities:* You can make infinite energy with it, which is pretty silly; or* The thrust/power ratio drops off as you go faster, which is pretty silly also.So, if it works, things are going to be silly, it's just a question of which kind of silly.
Quote from: QuantumG on 11/13/2012 12:42 amWell, if it works, there's two possibilities:* You can make infinite energy with it, which is pretty silly; or* The thrust/power ratio drops off as you go faster, which is pretty silly also.So, if it works, things are going to be silly, it's just a question of which kind of silly. That is the same 'sillyness' that Relativity has. Although there the mass increases with velocity when approaching the speed of light.
Quote from: JohnFornaro on 11/13/2012 12:37 amThe first part I get. ... Electrical energy is different, always speeding around at more or less the speed of light; a constant, no matter the frame of reference. ... These experimenters claim that they can take that electricity out of its frame, and direct it to mass in another arbitrary frame of reference.So if you use this battery to directly impart kinetic energy to a vehicle, the kinetic energy it imparts has to be the same in all reference frames, because the energy used to impart it is the same in all reference frames.Except that it can't be, because kinetic energy, when defined as 0.5mv² for a single chunk of matter of mass m at a single velocity v, is inherently not the same in all reference frames.
The first part I get. ... Electrical energy is different, always speeding around at more or less the speed of light; a constant, no matter the frame of reference. ... These experimenters claim that they can take that electricity out of its frame, and direct it to mass in another arbitrary frame of reference.
This is why conservation of energy inherently requires reaction mass. And that is why the M-E people are so keen on pointing out that their idea is not a "reactionless" thruster, but merely a "propellantless" thruster.
Quote from: JohnFornaro on 11/12/2012 02:48 pmThis paper appears to be a translation of the one written in Chinese, and posted earlier. It cannot be considered a peer reviewed paper.I never said it was.
This paper appears to be a translation of the one written in Chinese, and posted earlier. It cannot be considered a peer reviewed paper.
if there were such a thing as a tractor beam that could reach across interstellar distances we could swing though the stars like tarzan, always chosing a new star with the desired relative velocity to us. This also gives us energy for free, at least locally.We can think up various 'propellentless-like' forms of propulsion...
At this point, the system "is formally equivalent to an ideal gas of massive bosons." Massive, in this case, being 6.7 x 10-36kg.
Quote from: KelvinZero on 11/13/2012 05:55 amif there were such a thing as a tractor beam that could reach across interstellar distances we could swing though the stars like tarzan, always chosing a new star with the desired relative velocity to us. This also gives us energy for free, at least locally.We can think up various 'propellentless-like' forms of propulsion...The tractor beam is not propellantless - the stars are the propellant (though pulled towards the craft, rather than the normal pushed away).The tractor beam would also be doing work against the star (to accelerate the ship), so that wouldn't be free, either?cheers, Martin
Furthermore, the device that these people are discussing is protected by the Chinese patent system.
My absolute first reaction to any propellentless proposal is to ask is what happens if we try to construct a perpetual motion machine as described earlier, just as my first reaction to any FTL proposal is how it would behave if we attempted to create a paradox in the usual way.
Quote from: KelvinZero on 11/13/2012 10:41 pmMy absolute first reaction to any propellentless proposal is to ask is what happens if we try to construct a perpetual motion machine as described earlier, just as my first reaction to any FTL proposal is how it would behave if we attempted to create a paradox in the usual way.It is not a perpetual motion machine as energy enters the system, for example by using solar panels. The problem with perpetual motion machines is energy dissipation, not "motion".
Quote from: JohnFornaro on 11/13/2012 02:13 pmFurthermore, the device that these people are discussing is protected by the Chinese patent system.Which device are you referring to? The device covered by their patent claim is for measuring the net thrust of the em-drive. They do not appear to have asserted any claims on their implementation of the em-drive, which seems to be the same as Shawyer's.
Quote from: joek on 11/14/2012 01:34 amQuote from: JohnFornaro on 11/13/2012 02:13 pmFurthermore, the device that these people are discussing is protected by the Chinese patent system.Which device are you referring to? The device covered by their patent claim is for measuring the net thrust of the em-drive. They do not appear to have asserted any claims on their implementation of the em-drive, which seems to be the same as Shawyer's.I re-read the English translation of the Chinese paper. You are correct: the device explicitly mentioned as "patented", is the measuring device, and I mis-read the first time. However, it measures the thrust of another device, the EM-drive, which apparently has not changed in design over the last four years.Their experimental results cannot be duplicated until both devices, the one which thrusts, and the one which measures the thrust, can be built by another, independent, lab, and its net thrust also measured.