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Re: A question on Open Source...
« Reply #75 on: September 19, 2006, 05:22:02 am »

I'm rather the opposite.  I often feel the urge to report my own posts when I feel i'm contributing to a problem, such as a endlessly over-and often done discussion.  Like Star Wars vs. X, or Star Wars physics.  It was a great work of fiction, but any pretentions to it or its technology being a kind of physically explanable reality is very silly.  I mean, lightsabers, flakking turbolasers, blasters that seem to have no more range, accuracy or firepower than (sub)standard modern military weaponry. 

I suppose it's fun to apply physical knowledge (such as we have it) to situations such as the movies, but having done this many, many times before I guess i'm jaded to it now;  It will never make sense, the writer nor the effects managers were calculating the whatnot in the whatsit when they made the pretty green laser things.

For some odd reason, I still enjoy applying my scant physical knowledge to Star Trek, but I think that's because I like it more. :3
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Re: A question on Open Source...
« Reply #76 on: September 24, 2006, 10:08:20 am »

Death 999, sorry this took so long. I’ve been busy...
I would quote you in sections, but all the associated copying and pasting is soooo long, so hopefully this is understandable.

When considering adiabatic things, one still uses the ideal gas equation to obtain various relations, which is handy. It’s just that the basic relation CdT = -PdV for adiabatic changes is the starting point.

Of course, once the temperature falls to below the melting point, the material (almost certainly containing lots of iron if nickel is present in significant quantities) will condense to form a hot liquid or solid (depending on the pressure), which would be visible. Note that melting and boiling points depend not only on the temperature, but also on the pressue.

You are right that an expanding gas would be denser in the inside. However, f=3 only for a monatomic gas. If the asteroid is the most common, it is probably composed of silicates, which will have f=5 (for a power of 5/2 in the adabatic equation relating temperature and pressure).

I am not sure why you don’t like my wonderful red circle. At any rate, you can’t draw any line in any image in that picture through the center of the asteroid that is nearly twice as long as the asteroid itself.
What do you mean by “potato”-shaped asteroids being the normal? How can you draw any conclusions about the area of the asteroid behind that in our field of view being short? If anything, I would think it’s at least the same distance as roughly circular part of the asteroid we can see. This is because the glow is seen around the side of the asteroid, and hasn’t had time to travel to the center.
...or are you not counting the white area in the first picture as part of the asteroid? I think it is, but the pictures on Saxton’s site didn’t show the thing before the turbolaser hit...

If the explosions are identical to the planted charges, then we should also see that they are not so high energy afterall! Too low energy in fact, so it ends up as “???”.
Anyway, if the turbolaser particles somehow penetrated the asteroid, they would still have deposited more energy on the surface then in the center, and they would continue to deposit a decreasing amount of energy throughout the whole thing before emerging on the other side in reduced (perhaps invisible) state.
The beam of the turbolaser certainly moves slowly, but the asteroid only explodes a bit before the beam hits, leading on to believe that the velocity of the turbolaser I similar to that of the tracer. Of course, if it were not, then the tracer would be pointless, as relativistic particles would be essentially “point and shoot” (though not at long ranges, but slow tracers wouldn’t help there), and tracers would be useless.

I do not see a bright spot on the far side of the asteroid. Could you circle it? It might have something to do with the red dot I put in the center. I needed to reconvert the image to .jpg form, which blurs everything due to some probably stupid reason (I do all measurements with downloaded originals converted to .bmp).

Your three points seem right, but an explanation can’t have any inconsistencies, which a boiling asteroid seems to have. Another explanation might be that the explosion is low powered, with the debris quickly scattering to small mostly non-glowing bits (or just have the glow provided by the turbolaser tracer), not a threat to the star destroyers.

Overall, my GCS vs. Super Star Destroyer assessment was not based on any of my own things, but on the movie that was linked! I was just reinterpreting the movie... Even assuming a canon Galaxy class starship has much better technology, the super star destroyer could still win since is so much bigger, increasing its combat ability.
I also said that Saxton’s site was not worthless, but usually good. My main issue was his choice of sources, but canon policy is a nebulus topic for me...
Meanwhile, I also said that st-v-sw.net had mistakes.
When working with so much material, one is bound to make at least SOME mistakes and omissions, especially with as complicated an issue as sci-fi science!
I would consider both sites to be much better then that slightly loony stardestroyer.net site, which was why I refered to st-v-sw it originally. If I had know about Saxton’s site then, I would have linked to it too with the same warning I gave for st-v-sw.net (besides also mentioning the sources thing):
“I believe it has a few mistakes, but it's mostly good...”

I was under the impression that the Imperials had a much more powerful fleet overall, but some had essential Empire-maintained duties elsewhere, so their ambush fleet was not decisively more powerful then the rebels. Then the rebels won due to better crews and construction doctrine (not sure about the latter – I might be confusing it with the Star Wars games I played a long time ago...), and getting lucky by destroying the super star destroyer (lesson: do not put windows on your ship).
...and finally, how did the Ewoks take massive casualties? It seemed to me that they were completely outfighting the imperials, and only had three dead or so.

Cheers,
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Re: A question on Open Source...
« Reply #77 on: September 25, 2006, 05:30:33 pm »

In reference to the movie, okay, I didn't notice that that was what you were reacting to, it just sounded like the kind of thing that certain ST fans say (I actually knew one who said that the Defiant would be able to destroy the SSD in about 3 seconds with no risk to itself, every time).

Now that I've actually watched the movie, I have to agree with your assessment.

Quote
Of course, once the temperature falls to below the melting point, the material (almost certainly containing lots of iron if nickel is present in significant quantities) will condense to form a hot liquid or solid (depending on the pressure), which would be visible. Note that melting and boiling points depend not only on the temperature, but also on the pressue.

My point was that it will only be able to cool to that temperature by evaporating, and once it has done so, it is so dilute that it will not recondense.

Oh, and yes there is pressure dependence; but being in a vacuum does produce the lowest boiling points.

Quote
When considering adiabatic things, one still uses the ideal gas equation to obtain various relations, which is handy. It’s just that the basic relation CdT = -PdV for adiabatic changes is the starting point.

Actually, this is for a thermal gas, which though adiabatic remains homogeneous and ergodic. This gas is not homogeneous, and is most certainly nonergodic.

How is this most relevant? First, position is very much a function of velocity. The faster you go, the further you are from the point source. If you go with one angle, you will quickly self-select to be with particles moving at that same angle. This is the opposite of homogeneity.

Second, time has not been given to permit the energy in the spin degrees of freedom to equilibrate with the energy in the kinetic degrees of freedom. In any case, such equilibration will require collisions to conserve momentum.  So, the silicate factor would only be a concern for the part of the gas which is still close enough to the center to still be undergoing collisions at an appreciable rate.
This system is thus nonergodic.

If you stuck it in a box that was two asteroid radii wide, then sure, I would immediately grant that it would remain quite hot, as the system would lose its velocity selection. This would then permit more collisions, which would allow energy exchange with the spin degrees of freedom.

But it's not in a box.

As for the circle:
I only looked at it in the low-res version at first (I didn't realize there was a high-res version until returning to it). It appeared to have a bright dot on the far side from entry. Further, due to mixing bright and dark tends to favor bright, the boundary favored the explosion and made the asteroid look smaller.
This point is conceded.

As for the planted charges: Well, yeah, it's smaller than otherwise. I'm trying to fit the visuals, not maximize SW power. Check out the trees they blew up in RotJ, check out just about any of the explosions. They look like central explosions, not side explosions.

As for the turbolaser and relativistic particles:
I have a model for the turbolaser, that I didn't get into before because it's just my idea and I'm not really saying you should go for it.
However, it does permit some things you said were not permitted.

The green streak is a plasma lens which focuses a laser onto point in front of it. That point may have a small projectile present, or nothing. That laser tweezes the projectile, causing nuclear fusion; or some exotic physics gets involved. Either way, that greatly amplifies the effect.

Thus we have a laser, and somehow it gets 'turbo', and the green streak still does something. It also explains the 'flak bursts' sometimes seen.

Note that this fits nicely with the graphics of the Death Star and the mini-superlasers seen on the small landing craft in AotC.... only in this case, the high-powered reaction is done under a more controlled circumstance. And right next to the shooter, where if it went off in the wrong way it would be catastrophic. Which is one reason such systems may not be used routinely.

This reconciles the minimal but nonzero damage to shielded objects with the collossal damage to unshielded ones (shields usually screw up the lens so that the high-powered reaction does not occur; but you still get hit by the laser, the target projectile, and the plasma; and sometimes shields don't work fully and the high-energy reaction occurs at least a little bit).


In any case, more pertinent to the present discussion, it also may explain why the bolt as a whole moves very slowly, but the damage leaps ahead of it just a little bit; and it permits relativistic particles to be created upon impact.


Re: Stardestroyer.net:
The front page and certain elements of the presentation are indeed silly. The individual more technical pages are not. I have not looked at every page, but I'd be curious as to what you think is loony.

Re: Imperial navy at Endor:
Sounds about right. Note that naval engagements typically occurrred at very long range. The imperial training may not have emphasized short range, which is where most of the fighting actually took place. I am not familiar with canon sources comparing the relative merits in construction of star destroyers and the rebel vessels.

Re: ewok battle:
The ewoks siezed the advantage in the opening moments, and continued to outfight the ground troops, though taking not insignificant casualties. The armored elements caused a great deal of trouble until the counters came into play.

I recall about an even number of scenes of ewoks and imperials dying. The ewok scenes were played up for the teddy bear aspect, of course.

It would be interesting to do a tally.


In any case, I am enjoying this debate much more now that I know you weren't like that guy I referred to up top.
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Re: A question on Open Source...
« Reply #78 on: October 02, 2006, 02:11:58 am »

I’m not sure what you mean by “cool to that temperature by evaporating”. I think you might be right about the fact that the gas would never recondense, however. The temperature would fall, but the pressure would fall as well, preventing condensation (I overlooked the pressure falling previously).

As a side note, you don’t “boil” things in a vacuum, you sublimate them, transiting directly from a solid to a gas. Since there is no pressure, breaking the solid structure converts straight to a gas, instead of just to a liquid.

The adiabatic calculation is of course, an approximation, but it is roughly decent, for in the interior of the gas there are still many collisions. Density is a function of position for sure, which reduces the radius in which we would expect to see a glow, but then again, our earlier example had the turbolaser providing just barely enough energy to vaporize it, which sure would be a coincidence.
I actually had looked for the equations for a ball of gas expanding in a vacuum earlier, but didn’t find any on the internet, and I don’t remember any of my thermodynamics books having them either. I lack the time to try to derive them, as you can probably tell since I’ve been taking too long to respond to everything on this board...

Also on the glow, it seems to only expand in some directions, and not in others. The brightness gradient also varies from extremely high in some zones to decent in others, which is inconsistent with fast vaporization of the asteroid.

Your turbolaser idea was similar to one I entertained a couple years ago, but I believe it has an important flaw. The green bolt moves with the initial velocity of the Star Destroyer, but if the Star Destroyer is accelerating, the barrel of the turbolaser will no longer line up with the green bolt when it hits the object. Also, a powerful and small enough laser would show up in the atmosphere when dealing with blaster fire.

I don’t have any of the movies right now to look at in more detail (I had tapes that are now at my parents house). Actually, I haven’t touched anything with “Star Wars” in its name since Episode One. *shudder*. I used to be a big fan too; I could quote the armaments and shields and such (from the Tie Fighter game) of the different ships...

It’s been a couple years since I’ve visited stardestroyer.net, so I don’t remember specifics right now. I’ll try to take a look at a few of the pages sometime in the next week or so and comment.

P.S. Do you work in the sciences? I find that most people would never know what “ergodic” means...
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Re: A question on Open Source...
« Reply #79 on: October 02, 2006, 11:29:14 pm »

I’m not sure what you mean by “cool to that temperature by evaporating”

I mean that the temperature drops as the gas expands into a larger volume. Of course, it is doing so in a completely different way than the expanding box method, rather using a velocity selection method.

As a side note, you don’t “boil” things in a vacuum, you sublimate them, transiting directly from a solid to a gas. Since there is no pressure, breaking the solid structure converts straight to a gas, instead of just to a liquid.

Well, yeah, if you want to be technical.

The adiabatic calculation is of course, an approximation, but it is roughly decent, for in the interior of the gas there are still many collisions. Density is a function of position for sure, which reduces the radius in which we would expect to see a glow, but then again, our earlier example had the turbolaser providing just barely enough energy to vaporize it, which sure would be a coincidence.

or careful doling out of the firepower. Excess might be counterproductive.

I actually had looked for the equations for a ball of gas expanding in a vacuum earlier, but didn’t find any on the internet, and I don’t remember any of my thermodynamics books having them either. I lack the time to try to derive them, as you can probably tell since I’ve been taking too long to respond to everything on this board...

My approach would be to calculate the relative velocities, basing it on the angle subtended by the source for two dimensions. In the third dimension, we would have to worry about hotter particles overtaking colder particles released earlier.

With that approach, we can get the time between collisions even without the temperature as a function of expansion. That would give a hint as to the optical depth, which would in turn indicate how much glow we'd see.

Also on the glow, it seems to only expand in some directions, and not in others. The brightness gradient also varies from extremely high in some zones to decent in others, which is inconsistent with fast vaporization of the asteroid.

Inconsistent with homogeneous vaporization, sure. If the middle vaporized first, as makes sense, then it would fly out in the directions it could.

We also don't know what magnetic or otherwise anisotropic forces the turbolaser field itself carries.

Your turbolaser idea was similar to one I entertained a couple years ago, but I believe it has an important flaw. The green bolt moves with the initial velocity of the Star Destroyer, but if the Star Destroyer is accelerating, the barrel of the turbolaser will no longer line up with the green bolt when it hits the object. Also, a powerful and small enough laser would show up in the atmosphere when dealing with blaster fire.

I know about the first problem; it's much more severe for fighters, of course. I believe you meant the bolt is oriented back toward the cannon only in the cannon's original rest frame, not that it moves with the original velocity...
In any case, there are a variety of solutions which do varying levels of violence to the idea of turbolasers, continuity, physics, etc.
The simplest would be that the laser does not need to be sent straight up the plasma, but merely needs to hit the plasma, energizing it. This does minimum violence to continuity and the concept of turbolasers, but isn't exactly gentle to physics.
As for the second, it could be an infrared or deeply UV laser such that we wouldn't see it anyway.

The other option is that the electromagnetic energy was locked into the plasma trail when it was fired; when the plasma is distorted then the energy is released. Problem is, the only way we've found to freeze light does involve a carrier wave being sent through the medium in question, so we'd need a laser going all the time instead of just on impact.

P.S. Do you work in the sciences? I find that most people would never know what “ergodic” means...

PhD student in physics at UPenn.
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Re: A question on Open Source...
« Reply #80 on: October 10, 2006, 04:55:07 am »

With a very high energy event, I would think that the process would be more homogeneous, leading to a more homogeneous dispersion pattern, at least during the time at which there is no more solid left. As for variable firepower or anisotropic abilities for the turbolaser, I would think Occum’s Razor comes into play, though the nature of the turbolaser being unknown somewhat dulls the razor...

This isn’t my area of expertise, but wouldn’t a low powered laser in the atmosphere be invisible at any color (unless the atmosphere is polluted), while any powerful enough to excite the atmosphere would be visible? Presumably these weapons would use powerful lasers...

Anyway, I think a simpler explanation would be that the green stuff is normally invisible, but that the laser somehow “activates” it. The part that hits before the green area hits does interact, but it is just leftover and does very little damage.

Re: Stardestroyer.net
Again, I do not like the fact that he refers to many technical manuals and books. Also, he seems to not consider many explanations that might be superior to his own in almost all topics.
For example, skimming the photon torpedo page, he seems to instantly take the tech manual’s statement as an upper limit. He certainly thinks that the blast cannot somehow be directed energy, citing the worry from backblast, but he says somewhere that shields reflect energy, and exploding debris would be backblast too. He states that torpedoes are not effective against highly moanuverable targets and thus what would be the point of phasers? Well, torpedoes in a DS9 episode were effective against Birds of Prey, and there are several reasons that phasers would be useful too (precision, variability against different shields, etc etc etc...), so that statement seems ignorant. He says that quantum torpedoes have some sort of disadvantage (in deployment or ability) compared to regular torpedoes, but nearly all new weapon systems take time to supply to an entire fleet.
Another very specific point in the large website (obtained from a link to the torpedo page): he seems to think that the Star Destroyers were taking many asteroid impacts since that was what was shown on screen, but there is no reason to assume this, especially since the screentime would show...things happening. He also assumes in the ROTJ battle that the ships were constantly exchanging fire, but there seemed to be only a few Calamari Cruisers, and the battle was at long rage for quite awhile, well outside the effective range of turbolasers based on the velocities.
It’s too big of a website for me to address completely unless I had dozens of hours to write, calculate, and look things up. He seems very opinionated in almost every page. I do like the Creationism versus Science section though. Wink
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Re: A question on Open Source...
« Reply #81 on: October 12, 2006, 04:36:45 pm »

With a very high energy event, I would think that the process would be more homogeneous, leading to a more homogeneous dispersion pattern, at least during the time at which there is no more solid left.

And with that last caveat in place, we have no argument left; but that occurs rather late in the process.

As for variable firepower or anisotropic abilities for the turbolaser, I would think Occum’s Razor comes into play, though the nature of the turbolaser being unknown somewhat dulls the razor...

I like that image. I don't find it at all unreasonable to suspect variable firepower; and as you suggest below in reference to photon torpedoes, directionality isn't at all unreasonable.

This isn’t my area of expertise, but wouldn’t a low powered laser in the atmosphere be invisible at any color (unless the atmosphere is polluted), while any powerful enough to excite the atmosphere would be visible? Presumably these weapons would use powerful lasers...

"Exciting the atmosphere" would be a frequency requirement, not a power requirement.


Anyway, I think a simpler explanation would be that the green stuff is normally invisible, but that the laser somehow “activates” it. The part that hits before the green area hits does interact, but it is just leftover and does very little damage.

I'm unsure what you mean -- where is this activating laser coming from, that it does not hit that leading portion?

Again, I do not like the fact that he refers to many technical manuals and books. Also, he seems to not consider many explanations that might be superior to his own in almost all topics.

I'll agree there. His ST shields page in particular aroused my ire, after which I proposed my ST shield theory on the discussion boards. His only rebuttal was that I couldn't explain X, where X was something his theory couldn't explain either. Kind of annoying.
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Re: A question on Open Source...
« Reply #82 on: October 16, 2006, 04:32:02 am »

Directionality for turbolaser (or other ‘laser’ weapons – what are the ones on the fighters called?) batteries is more difficult then for torpedoes (photon, proton, either way...) since the actual laser could come into the beam at any angle, while directionality can be built into torpedo weapons. There’s also the problem of actually having a proper angle on the green stuff with the laser in the first place, since fighter weapons seem to be pointing in a fixed direction. Variable firepower is easier to accept, though.

For the rest, it looks like I accidentally deleted several sentences when revising my post. Simply exciting the atmophere’s molecules is dependant on frequency of the photons, but any sufficiently powerful laser will encounter problems in the atmosphere since it will ionize many air molecules in its path, which should be quite visible.

For my turbolaser explanation, I had meant to say that the laser interacts with the green stuff before the green stuff is fired, so the laser never even leaves the Star Destroyer. The leading edge may simply not have been hit by the laser. Do all turbolaser hits start the explosion before the green part hits, or do only some of them? If the latter, it may just be impreciseness in shooting the laser at the green stuff before it exists the barrel.
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Re: A question on Open Source...
« Reply #83 on: October 16, 2006, 04:28:28 pm »

Ah, got it.

By the way, in many cases, destruction does not begin before the green bolt arrives.
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