Could ME thrusters be used to produce torque?

[TallDave]

I still do not understand how energy is being extracted for net power. How does .035 N/w efficiency turn into a net power device?


Remember that a newton and a watt are not units of the same thing, and are thus not directly comparable. Then go revisit my earlier post where I calculated it out and see if you can understand the math. It's pretty basic; it shouldn't be hard.

I agree, this is confusing. But when you consider that the rest of the Universe is losing energy to your drive, it makes intuitive sense.

[chrismb]

So now it's the second law, then? You're dodging all over the map. What happened to relativity?

You're thinking too much on 'paradigms' and not thinking enough on the actual issue.

Relativity is a reality because space is expanding. That means that no two points in the universe actually strictly share the same inertial frame, as a point that is at a distance of [lightspeed x <age of universe>] will be in an inertial frame a full c different to yours, and linearly variant in between. (Close in, you don't notice that so obviously, but it is still responsible for why, for example, magnetism is manifest, so works on the minute scale as well.) So there 'isn't' a null frame in which to 'push' against and 'make colder', thermodynamically speaking. It's the frame-variancy due to relativity which means thermodynamics doesn't 'work' as you're suggesting it might.

(This thread isn't even amusing me, which is the only reason I might normally chip in with these daft ones every now and again, so "I'm out"!...)

[pfrit]

You can generate power this way with ordinary rocket engines too, but since you need to fuel them (and accelerate the fuel up to the flywheel speed) it doesn't come out over unity no matter how fast the flywheel turns, so this is simply a particularly impractical way to build a heat engine...

I've never really thought of this. Are you sure that this would be a bad idea? Remember the helicopters with the wing tip jet engines? The problems with them was not efficiency (they were very efficient) but reliability (they weren't reliable at all) and failure modes (the primary failure mode involved the whole thing disintegrating). It strikes me that this could be a very efficient way to generate electricity because of the very high exhaust temps achieved. That is of course assuming that the quite significant engineering problems could be overcome. Interesting idea. Could I get MSimon or another engineer to weigh in on this? Could this be more efficient way of burning natural gas to generate electricity?

[TallDave]

Relativity is a reality because space is expanding.

???

That means that no two points in the universe actually strictly share the same inertial frame, as a point that is at a distance of [lightspeed x <age of universe>] will be in an inertial frame a full c different to yours, and linearly variant in between.

This sort of makes sense. OTOH, we already know Einstein was wrong about "spooky action at a distance." Quantum entanglement does happen, and there's no reason to think it doesn't operate across any arbitrary distance.

This reminds me of a passage in physicist Brian Greene's Elegant Universe where he points out one of the implications of relativity is that by walking in certain directions across your living room you are traveling in time relative to a very, very distant observer. In theory, with quantum entanglement you could get tomorrow's lottery picks this way. To me this says relativity must be wrong (or at least incomplete) in certain respects.

Maybe you need a GUT to reconcile the inertial frame problem. Maybe that's why no one came up with the Mach drive before...

[paulmarch]

I don't think you understand the issue of frame-specific entropy, then. For 'work' to be done, there has to be some capability for a change of state to occur 'exothermically', that is to say, entropy increases. If you have a well-defined (by position and momentum) set of particles then they have a given entropy, but only with respect to their inertial frame for it differs between frames. For example, if you were to take a look at a lump of granite, it is chemically very inert and all the SiOx consituents are thermalised and so it cannot do any 'work'. But only in its frame, for if it were actually a meteorite you were looking at, heading towards the earth at 30,000kph, then that meteorite-earth system now does have the capacity to do work. So you can't separate out inertial frames to see where 'work done' can go, or be subsequently made use of. If you invent an 'absolute universal frame' then what you are describing is a reducing entropy as the sum of all frames, which we presume to be falsifiable by our modern understanding of thermodynamics.

So now it's the second law, then? You're dodging all over the map. What happened to relativity?

I personally think you should forget paulmarch's comment about reducing the temperature of the universe; it seems to be unhelpful...

Did you read this like I asked you to? I haven't been playing fast and loose with reference frames like you seem to be accusing me of; this works out fine (to first order) with a simple Galilean transformation:

...from rest the energy associated with 0.1 m/s of delta-V is 0.005 J/kg. At 7.5 km/s, the energy associated with 0.1 m/s is about 750 J/kg. The key point is that the lower the velocity difference between an engine and its reaction mass, the lower the required energy output gets. This is the Isp principle.

The reaction mass is distant matter. Plenty of distant matter is moving at very close to whatever reasonable speed you want to go.

From the perspective of the drive, this means you do a small amount of positive work on that distant matter, causing it to move slowly in the direction opposite your thrust vector.

From the ground, the distant matter slows down slightly, doing a large amount of positive work on the already fast-moving M-E drive.

...paulmarch, have I really missed something critical here?

I will admit that the spinner idea seems to me that it might violate the entropy condition, but as I said in my original acknowledgement of this, I haven't done the math, and it's entirely possible I'm wrong. It's also possible, I suppose, that the M-E spinner acts as a kind of universe-wide Maxwell's Demon... but this has nothing to do with conservation of energy, which was your initial argument.

I still do not understand how energy is being extracted for net power. How does .035 N/w efficiency turn into a net power device?

Remember that a newton and a watt are not units of the same thing, and are thus not directly comparable. Then go revisit my earlier post where I calculated it out and see if you can understand the math. It's pretty basic; it shouldn't be hard.

The upshot is that if you can generate torque in the way you've described, you can run a generator with it, and with reasonably efficient M-E thrusters, the power required to produce the torque can be smaller than the power you get from the generator. The key requirement is that the speed of the thrusters at the edge of the device be high enough, since power is force times velocity. This means that the faster you spin the thing, the higher the gain becomes. Energy is not actually created; the M-E thrusters are getting it from the rest of the matter in the universe. As my quote above demonstrates, the faster the thruster moves, the more work is done on it by the force between it and the distant matter (again, P = Fv).

You can generate power this way with ordinary rocket engines too, but since you need to fuel them (and accelerate the fuel up to the flywheel speed) it doesn't come out over unity no matter how fast the flywheel turns, so this is simply a particularly impractical way to build a heat engine...

"From the ground, the distant matter slows down slightly, doing a large amount of positive work on the already fast-moving M-E drive.[/quote]

...paulmarch, have I really missed something critical here?"

No, I think you've got it right per what I currently envision the proposed M-E energy extraction process should be like, but that is just MY current opinion at the moment, and it will no doubt change as new M-E and cosmological experimental data comes in to temper it.

BTW, Tom Mahood, Woodward's graduate student in the 1997-to-1998 time period, had a cute commentary on this M-E energy extraction issue and it went like this: “Tomorrow’s Momentum Today!” And when you perform the units analysis of Newtons/Watt, you end up with “seconds per meter” traversed. So you could also think about this M-E energy extraction process as slowing the rate of time in the universe instead of lowering the average velocity of its ions AKA its temperature.

[MSimon]

Thermodynamics is a statistical process. It doesn't hold on the very micro level.

Exactly. So if it's drawing 'energy' on the whole universe then it will be statistically smoothed smoother than a smooth bowling ball at a 'smoothest bowling ball' competition for regional 'smoothest bowling ball' champions, rather than the granular entropy you're talking about.

Well I dunno. If inertia is a quantum process it may follow non-thermodynamic laws. I guess I didn't explain myself well.

[93143]

You're thinking too much on 'paradigms' and not thinking enough on the actual issue.

This may be because your "unconventional education" makes you an ineffective technical communicator. It's very hard to tell what the actual issue is supposed to be.

Relativity is a reality because space is expanding. That means that no two points in the universe actually strictly share the same inertial frame, as a point that is at a distance of [lightspeed x <age of universe>] will be in an inertial frame a full c different to yours, and linearly variant in between. (Close in, you don't notice that so obviously, but it is still responsible for why, for example, magnetism is manifest, so works on the minute scale as well.) So there 'isn't' a null frame in which to 'push' against and 'make colder', thermodynamically speaking. It's the frame-variancy due to relativity which means thermodynamics doesn't 'work' as you're suggesting it might.

Yes, the picture distorts quite a bit over large distances. But that should all come out in the wash; it won't outright prevent any interaction remotely resembling what I've described. By your argument, an ion engine can't work because space is expanding between the electrodes and the propellant, thus preventing momentum exchange.

Also, I'm pretty sure magnetism has nothing to do with the expansion of the universe. Special relativity yes. Hubble's Law no.

I still think you're hung up on something, and I can't think what. Perhaps I should try to grind through the math and try to figure out precisely how this is actually supposed to work - but I REALLY don't have time right now...

Relativity is a reality because space is expanding.

...wait... could it be that you don't understand relativity? An expanding universe is just one particular class of solutions to Einstein's field equations. If our universe ever stops expanding and begins to contract, relativity will continue to be a good description (and in fact the solution that describes the universe, being a spacetime and not just an instantaneous universe, will actually not change). Time dilation and length contraction and the lightspeed limit will not go away.

An inertial frame is a velocity, not a position. Two objects a considerable distance apart can be in almost the same inertial frame, while two objects quite close together (like a proton and an LHC magnet) can be in vastly different inertial frames. This has nothing to do with relativity, and relativity modifies the details considerably but leaves the basic idea intact.

(This thread isn't even amusing me, which is the only reason I might normally chip in with these daft ones every now and again, so "I'm out"!...)

Oh, come on, is that all you got? Weak sauce.

On the other hand, maybe I should get some work done...

[MSimon]

You can generate power this way with ordinary rocket engines too, but since you need to fuel them (and accelerate the fuel up to the flywheel speed) it doesn't come out over unity no matter how fast the flywheel turns, so this is simply a particularly impractical way to build a heat engine...

I've never really thought of this. Are you sure that this would be a bad idea? Remember the helicopters with the wing tip jet engines? The problems with them was not efficiency (they were very efficient) but reliability (they weren't reliable at all) and failure modes (the primary failure mode involved the whole thing disintegrating). It strikes me that this could be a very efficient way to generate electricity because of the very high exhaust temps achieved. That is of course assuming that the quite significant engineering problems could be overcome. Interesting idea. Could I get MSimon or another engineer to weigh in on this? Could this be more efficient way of burning natural gas to generate electricity?

I was actually contemplating building something like this once using pulse jets (V1 style). I figured it would be a very low cost way to build a jet engine powered generator using low tech.

http://www.youtube.com/watch?v=ZFyvLz74 ... re=related

http://dvice.com/archives/2009/09/video-jet-power.php

I never worked out the efficiency.

[Helius]

And since the 5% of our universe’s mass/energy that makes up “normal” baryonic matter is composed of an estimated 1x10^80+ atoms & ions, speeding up ~1x10^30 atoms contained in a spaceship to some small percentage of the speed of light is not going to lower the temperature of the universe to any level measureable by our current state of the art IR instrumentation.

A good explanation. But I can already see you're going to have a problem with the environmentalists.

"STOP UNIVERSAL COOLING NOW!"

"STEALING MOMENTUM FROM OTHER GALAXIES IS WRONG"

"EXTRATERRESTRIALS HAVE RIGHTS TOO"

Al Gore will make a chart that shows the Universe is cooling at an unprecedented rate, Briffa will extrapolate from one star that we're all going to freeze to death in 50 years, and that will be the end.

Perhaps someone should inform the SETI folks they might take as evidence the existence of civilizations on the far side of the Universe by otherwise inexplicable local energy losses. I know a bunch of UFO folks that'd be on board with that explanation in a heartbeat. Personally, I think it's all a far fetch.

[chrismb]

By your argument, an ion engine can't work because space is expanding between the electrodes and the propellant, thus preventing momentum exchange.

Not that it doesn't work, but it doesn't work as efficiently once the ions are relativistic and their speed is comparable with the expansion rate of the universe (which is c).

Also, I'm pretty sure magnetism has nothing to do with the expansion of the universe. Special relativity yes. Hubble's Law no.

All part of the same deal. Honest!

If our universe ever stops expanding and begins to contract, relativity will continue to be a good description (and in fact the solution that describes the universe, being a spacetime and not just an instantaneous universe, will actually not change). Time dilation and length contraction and the lightspeed limit will not go away.

That's true, insofaras the 'c' in the Lorentz factor is the expansion rate of space, which in turn is the velocity of light, so you're actually talking about the same thing and don't seem to realise that. (viz. time dilation will change of you were to inpose a 'c' change).

Oh, come on, is that all you got? Weak sauce.

Please don't drag me back in again. I'm done here and want to leave you to your own interpretations.

[alexjrgreen]

That's true, insofaras the 'c' in the Lorentz factor is the expansion rate of space

I can only make sense of this if you're talking about the size of the visible universe.

[chrismb]

That's true, insofaras the 'c' in the Lorentz factor is the expansion rate of space

I can only make sense of this if you're talking about the size of the visible universe.

So now these thrusters are not only going to pull some magic energy from the whole of our visible 3D unieverse, you want to extend the conversation to the larger set of dimensions in which our 3D universe exists! I'm outa this one, guys! This has no bearing on the reality of technology we can ever expect to see.

[alexjrgreen]

That's true, insofaras the 'c' in the Lorentz factor is the expansion rate of space

I can only make sense of this if you're talking about the size of the visible universe.

So now these thrusters are not only going to pull some magic energy from the whole of our visible 3D unieverse, you want to extend the conversation to the larger set of dimensions in which our 3D universe exists! I'm outa this one, guys! This has no bearing on the reality of technology we can ever expect to see.

You're not listening.

Why do you think that space is expanding at the speed of light?

[TallDave]

their speed is comparable with the expansion rate of the universe (which is c).

Why do you think that space is expanding at the speed of light?

It can actually be expanding much faster than the speed of light, depending on which two points you select.

There is no speed-of-light limitation on the expansion of the universe. During inflation it expanded much faster than that, and the cumulative increasing distance between sufficiently distant points also increases faster than c.

[chrismb]

I can only make sense of this if you're talking about the size of the visible universe.

So now these thrusters are not only going to pull some magic energy from the whole of our visible 3D unieverse, you want to extend the conversation to the larger set of dimensions in which our 3D universe exists! I'm outa this one, guys! This has no bearing on the reality of technology we can ever expect to see.

You're not listening.

Why do you think that space is expanding at the speed of light?

Because the 'deepest' space objects [to us] are ([age-of-the-universe].[speed-of-light]) away, because Hubble's constant = 1/[age-of-the-universe] (try it - reduce all the variables down and see what you get!) and because, if you think about it, it's the only thing that makes complete sense. This is a bit of 'flat-earth' type thing - might seem unbelievable at the moment, but one day...

What you 'observe' with light is something that happened a moment ago (however short). It is trivially obvious that you can't observe anything that is travelling relatively to you quicker than you are expanding away from where it was, hence nothing appears to move faster than that speed, whatever interial frame you are in relative to the other thing. It is by definition that we 'observe' something a moment ago.

Do you really want the truth about this, do you think you could 'believe' something unimaginable?: Light is stationary (relative to the physical location of the universe at time=0), we move relative to light, within the very 'first' inertial frame.