Quote from: momerathe on 06/14/2014 10:38 amI've not been following the Q-thruster stuff too closely - is there a plausible story yet about how it doesn't violate conservation of energy? (a question that any purported reactionless drive needs to be able to answer)does it abide by the photon rocket limit?I too would like to know this...There must be some mechanism that limits the Q-thruster/Woodward drive vehicle so that the energy supplied in accelerating it is always greater thanDoes anyone know what that mechanism is?
I've not been following the Q-thruster stuff too closely - is there a plausible story yet about how it doesn't violate conservation of energy? (a question that any purported reactionless drive needs to be able to answer)does it abide by the photon rocket limit?
Thanks for your comments. My stating 'Prove it's impossible' was misguided.I guess I just want some form of propellant-less drive to be possible and my limited knowledge of physics led me to the most obvious objection to it. I hoped there must be an easy answer.93143 hints at a solution to my naive analysis but doesn't really go into detail. I suspect because he too doesn't understand the 'toy' problem enough.He states "An M-E thruster supposedly reacts against the rest of the mass in its lightcone via gravinertial radiation." The mass in the thruster's lightcone once it is switched on? This is obvious nonsense.
The lightcone of the thrusters particles since they were 'created'? That would include the entire (observable?) Universe then.After doing some further reading the KE of the postulated vehicle is supposed to come from the mass-energy of the causally connected Universe... That's one hell of an open system, or is it a closed system?I guess the jury is still out on this.I await news of more research with interest.
[...] A Q-thruster supposedly reacts against transient particles created by quantum fluctuations; the particles may not persist, but the momentum has to go somewhere and presumably does...
If you only consider the kinetic energy of the thruster and vehicle, you can never solve the conservation equations consistently because a single-component kinetic energy is not Galilean-invariant (or Lorentz-invariant, if you insist on using relativity for your toy problems). You're trying to analyze half of an open system and naturally enough getting garbage.
After doing some further reading the KE of the postulated vehicle is supposed to come from the mass-energy of the causally connected Universe... That's one hell of an open system, or is it a closed system?
Quote from: 93143 on 06/15/2014 04:43 am[...] A Q-thruster supposedly reacts against transient particles created by quantum fluctuations; the particles may not persist, but the momentum has to go somewhere and presumably does... That's why I asked if there's a "plausible story". This is not a plausible story, this is at the level of waggling your fingers an going 'oooh, magic!'
Quote If you only consider the kinetic energy of the thruster and vehicle, you can never solve the conservation equations consistently because a single-component kinetic energy is not Galilean-invariant (or Lorentz-invariant, if you insist on using relativity for your toy problems). You're trying to analyze half of an open system and naturally enough getting garbage.you can certainly analyse the energetics of partial systems - in terms of inequalities. Unless the kinetic energy of the exhaust is negative? Or the device is extracting energy from the quantum vaccuum. Either of which would be rather significant discoveries.
I too would like to know this...There must be some mechanism that limits the Q-thruster/Woodward drive vehicle so that the energy supplied in accelerating it is always greater thanDoes anyone know what that mechanism is?
Quote from: Stormbringer on 06/12/2014 10:12 pmjust because Dr white was not satisfied with the sigma level of his data and analysis does not mean he reported negative results. he said quite the opposite. (that the preliminary results were suggestive that he had detected a warp and he was encouraged by them) that is... unless there was a report after the one i saw."Not satisfied with the sigma level" means statistical analysis of the data did not support the conclusion. That's a negative result. At least it's a negative result to real scientists. White not reporting it doesn't mean the result wasn't negative. A preliminary result is what you get when you are doing a preliminary test, not when you do a rigorous experiment and it doesn't give the results you like.(Also, why is it that some parts of your post follow standard capitalization rules and some do not? Do you not realize that standard capitalization lets people read more quickly? By putting a little more effort into generating your content, you will be aiding the many people you are asking to read it by posting.)
just because Dr white was not satisfied with the sigma level of his data and analysis does not mean he reported negative results. he said quite the opposite. (that the preliminary results were suggestive that he had detected a warp and he was encouraged by them) that is... unless there was a report after the one i saw.
I'm not claiming the Q-thruster works. I'm claiming that if it works, it will conserve momentum by reacting against something, and thus any conservation argument that neglects the reaction mass is invalid. Like the M-E thruster, it is not a "reactionless" drive; it doesn't claim to produce force out of nowhere.[...]And yes, the whole point of the Q-thruster is that it exchanges momentum and energy with the quantum vacuum. Just as the point of the M-E thruster is that it exchanges momentum and energy with all matter within the Hubble sphere (there; happy?) of the thruster.
but the fact remains that you cannot demonstrate anything either way by complaining about the kinetic energy of the spacecraft while ignoring the reaction mass.
http://rationalwiki.org/wiki/Statistical_significanceYou may find the section on 'The problems with statistical significance' interesting reading
... it would mean more space and mass allowances for equipment and materials for use at the various destinations such a craft could get to right here in this solar system.
Quote from: Robotbeat on 06/14/2014 05:29 pmOh, it's the same old capacitors/reactionless shtick. Next thread!Granted. It wont work if my inequality above us violated, but why not in general. Can you prove such a thing is impossible?
Oh, it's the same old capacitors/reactionless shtick. Next thread!
Mr Sonny White must know this... Whats going on?
'Prove it's impossible' was misguided.
Quotebut the fact remains that you cannot demonstrate anything either way by complaining about the kinetic energy of the spacecraft while ignoring the reaction mass.I disagree, obviously. I'll go into my thinking in more detail if you want, but I've got no skin in this game so I'm content to let it lie.
It seems like we're more or less on the same page. Could you elaborate on this?
ΔKEexhaust ≥ 0, because we're assuming that you have no effect on the exhaust plume previously emitted, and the KE of the extra exhaust during our time step is axiomatically positive (assumption 2)
(aside: why is this not true for rockets? because from a sufficiently boosted frame it looks like the vessel is decelerating its propellant. So, if you think in terms of the propellant, ΔKEpropellant can be negative. Here, however, the total mass of the vehicle does not change. People complain about "reactionless" drives, but the real problem is a "propellantless" one.)
The hidden assumption here seems to be that the reaction mass for a "propellantless" thruster is initially stationary with respect to the observer.
Well, that's no good...
Why are we so concerned about conservation of momentum and energy if conservation of mass isn't being respected?
It seems (from the references on Wikipedia) that White is trying to leverage the dynamic Casimir effect or something like that, and he asserts that there will be a "wake" of some sort. This is not something out of nothing; it is at most a zero-point energy device.
So the question isn't so much "how does the Q-thruster conserve energy?" as "how does the Q-thruster work?".
If you can't answer that, you have no basis for bringing in stuff like assumption 2.
@IslandPlaya: Just because something's in an inertial reference frame doesn't mean it's in your inertial reference frame. Take a look at my example with the cars.