Bad design in Star Wars

[Wyrm]

Is any amount down to 0 J for each turn enough? See, turning on a perfect circle actually costs no energy intrinsically. This is because the force is perpendicular to the displacement at all times. As anyone who knows basic physics knows, energy is only exchanged when the force is applied parallel to the displacement.

Technically true, but most viable methods we know for making an object push itself to one side or the other still require you to expend energy. Do you use magnets? In the Death Star's frame the torpedo is now a moving magnetized object that creates eddy currents in the shaft; the torpedo must supply the energy to start and stop the currents. Do you use rocket engines? You must expend fuel and energy to create the exhaust plume. The list goes on.

That's a matter of engineering, not physics. There's nothing physically preventing the torpedo from doing a square-dance on a dime using only a car battery, using some funky technology. [/hyperbole] There's also no saying what kind of power usage is excessive, for a little torpedo given that one starfighter cranks out more watts than the entire US.

Also, I'd like to point out that the Rebs knew how many turns the shaft had, whether that number is zero or over nine thousand. Whatever the energy cost for a turn is, it must come under the energy budget of the torpedo. Because if it even looked like there would be too many sharp turns for the topredo, someone would have said, "You know, that's an awfully large number of kinks for a photon torpedo to navigate through. Let's make sure it's even possible for our torpedoes."

[erik_t]

One might reasonably consider the duct to be an example of Poiseuille flow (note that this is a laminar analysis, while the flow in the duct would likely be turbulent and therefore experience a high pressure drop just from the straight duct). A well-designed sharp* corner might experience a pressure drop of 15% of the average dynamic pressure.

Fifteen percent sounds like a large drop.

Working through the equations,

Which ones?

The equations for a Poiseuille flow. I assume that if you question my understanding that you know enough to follow along. You can find an article on the subject on freaking wikipedia, for crying out loud. Now, is that an unfair assumption? Frankly I don't have the time or interest to hold your hand.

we might find the following ratio between bend pressure drop and total pressure drop:

http://tiny.cc/b3saCY

The image doesn't show at the time I write this. Please stick to Unicode for your notation.

Yes, obviously that would work great since you can't even look anything up.

Pratio = (0.15 * N * Ubar) / (0.15 * N * Ubar + 8 * nu * L / R^2)

was, as I recall, the equation.

Where N is the number of sharp* bends we desire, u_bar is the required average velocity, v (nu) is the kinematic viscosity and L the length of the tube. Assuming 10 bends, 7.5m/s air at 1500K, we might find that the ten (!) bends only contribute about 10% of the total pressure loss. This is, again, a substantial overestimate due to the assumption of laminar flow.

None of this answers why "any features on the order of meters will be swamped by features on the order of tens of kilometers". How does the fluid know that it's traveling down a pipe that is ~80 kilometers long?

I am not a textbook. I have presented the final comparison between 0.15*(dynamic pressure) and a Poiseuille flow. If you're curious beyond that, go look it up. The derivation is straightforward.

Yes, I addressed this on the previous page. "Provided you have the juice" is a pretty big assumption for a disposable item, of course. No fancy reactors here, not if you want a torpedo that costs less than a fighter...

Is any amount down to 0 J for each turn enough? See, turning on a perfect circle actually costs no energy intrinsically. This is because the force is perpendicular to the displacement at all times. As anyone who knows basic physics knows, energy is only exchanged when the force is applied parallel to the displacement.

Anyone who knows physics knows it's F(dot)R, but I digress. Turning on a perfect circle depends entirely on what your reaction force is exerted upon. I'm losing faith that you're interested in learning the correct answer here vs. "winning" the "debate".

I wish I could say I was surprised. It's a frustratingly common theme here.

[Wyrm]

Working through the equations,

Which ones?

The equations for a Poiseuille flow. I assume that if you question my understanding that you know enough to follow along. You can find an article on the subject on freaking wikipedia, for crying out loud. Now, is that an unfair assumption? Frankly I don't have the time or interest to hold your hand.

What, you mean this one?

∆P = 8μLΦ/πr⁴

Huh. And here I thought you knew what you were talking about. Let me show you something. We can rearrange the equation above like so:

∆P/L = 8μΦ/πr⁴

See the ∆P/L part? Do you know what that is? That's the pressure gradient along the length of the pipe, and you can replace that part with |∇P| and the equation would work just as well. The pressure gradient is, of course, completely local, and I've just eliminated L from the equation, and with it any fundamental dependence on the length of the pipe. Your move.

Yes, obviously that would work great since you can't even look anything up.

Pratio = (0.15 * N * Ubar) / (0.15 * N * Ubar + 8 * nu * L / R^2)

was, as I recall, the equation.

The derivation is obviously wrong, you ass. The dynamic pressure isn't constant, because the gas's density depends on the absolute pressure. That changes through the pipe.

I am not a textbook. I have presented the final comparison between 0.15*(dynamic pressure) and a Poiseuille flow. If you're curious beyond that, go look it up. The derivation is straightforward.

Except I trivially eliminated L from the Poiseuille flow equation, and the derivation is obvious crap. Still waiting for that dependence on L.

Anyone who knows physics knows it's F(dot)R, but I digress. Turning on a perfect circle depends entirely on what your reaction force is exerted upon.

The thing the reaction force is exerting itself on is the Death Star, which is very much more massive than the proton torpedo, and may be safely ignored in our problem.

I'm losing faith that you're interested in learning the correct answer here vs. "winning" the "debate".

I wish I could say I was surprised. It's a frustratingly common theme here.

Go fuck yourself. If you really knew your fluid dynamics, you would know that the apparent dependence on L in the Poiseuille flow is only an artifact on how the problem is commonly posed, and what really drives the fluid on is the pressure gradient. This is why I was genuinely confused when you stated that a few meter-sized kinks would not make a difference in a kilometers long pipe due to the difference in scales.

[raptor3x]

Do we know anything about the flow coming out of this exhaust port? Considering we're venting out into space and that this thing would apparently be open all the time with no way of closing, I'm wondering if the Knudson number of the flow is even high enough for Navier-Stokes to be valid.

[raptor3x]

Also, I seem to recall a loss of 15% of the dynamic head being associated with a wide open gate valve, so that doesn't seem unreasonable for a series of two sharp bends with guide vanes.

[erik_t]

The equations for a Poiseuille flow. I assume that if you question my understanding that you know enough to follow along. You can find an article on the subject on freaking wikipedia, for crying out loud. Now, is that an unfair assumption? Frankly I don't have the time or interest to hold your hand.

What, you mean this one?

∆P = 8μLΦ/πr⁴

Huh. And here I thought you knew what you were talking about. Let me show you something. We can rearrange the equation above like so:

∆P/L = 8μΦ/πr⁴

See the ∆P/L part? Do you know what that is? That's the pressure gradient along the length of the pipe, and you can replace that part with |∇P| and the equation would work just as well. The pressure gradient is, of course, completely local, and I've just eliminated L from the equation, and with it any fundamental dependence on the length of the pipe. Your move.

This equation, which you so obviously googled, is based on a reduction of the Navier-Stokes equations. Specifically, things reduce to:

dP/dx = μ d2u/dy2

Since this is effectively f(x)=g(y), it follows that dP/dx and the μ-term are both constant. The pressure gradient is emphatically not local; in order to satisfy Navier-Stokes, it is constant along the entire (constant-section) length of the pipe. This is non-controversial and is known to anyone who has taken even an undergraduate class in fluid mechanics.

The derivation is obviously wrong, you ass. The dynamic pressure isn't constant, because the gas's density depends on the absolute pressure. That changes through the pipe.

The gas is assumed to be incompressible through the duct domain, which is an excellent assumption for flows that are solidly subsonic. This is well-known to anyone who has even a cursory background in the sciences.

You have no rigorous knowledge of the subject and frankly I do not have the time nor the patience to argue at length with a fucking googlewarrior.

[Wyrm]

This equation, which you so obviously googled,

I got it off your own link to wikipedia. And somehow I'm to blame for it being inappropriate. Huh.

is based on a reduction of the Navier-Stokes equations. Specifically, things reduce to:

dP/dx = μ d2u/dy2

Since this is effectively f(x)=g(y), it follows that dP/dx and the μ-term are both constant. The pressure gradient is emphatically not local; in order to satisfy Navier-Stokes, it is constant along the entire (constant-section) length of the pipe. This is non-controversial and is known to anyone who has taken even an undergraduate class in fluid mechanics.

And yet, if I take a short section of pipe, punch two pressure probes into the pipe to get the pressure difference, I can deduce the volumetric flow through that section of pipe without knowing the total length of the pipe. Your protestations notwithstanding, there does seem to be a symmetry in the physics of the situation. Maybe it's a difference in how we define "local", but in my book "local" does not mean "immune to the physical conditions." It means that once you have the pressure gradient defined for every point in the pipe, you can forget about the length and just use the pressure gradient to figure out the dynamics.

You have yet to show that the fluid has any memory of how far it has traveled, let alone prescience of how far it has yet to go.

The derivation is obviously wrong, you ass. The dynamic pressure isn't constant, because the gas's density depends on the absolute pressure. That changes through the pipe.

The gas is assumed to be incompressible through the duct domain, which is an excellent assumption for flows that are solidly subsonic.

And what, praytell, justifies that assumption? The gas is emptying out into hard vacuum, for fuck's sake. Just about any gas speed is supersonic in hard vacuum. And assumed to be incompressible? Where the static pressure goes from some unnamed but almost certainly substatial pressure to basically nothing? How could it not expand by a significant amount as the pressure on it goes down?

This is well-known to anyone who has even a cursory background in the sciences.

It is also well-known to anyone with a cursory background in the sciences that before a model can be used, the assumptions behind them have to be justified.

You have no rigorous knowledge of the subject and frankly I do not have the time nor the patience to argue at length with a fucking googlewarrior.

If you don't want to argue with me, stop. It's that simple, really.

[PainRack]

The Death Star debate actually just rankles more of Lousy Rebel thinking.

Think about it. You sent 500+ X-wings and you failed to take out the Death Star. Yet, you expect a smaller snubfighter attack to succeed, because the Empire hasn't failed to consider a snubfighter a threat and has weaker screens? Oh, but you have a one shot kill now!

And frankly, why the hell would anyone send snubfighters to take on a Death Star? Why not some Rebel cap ships?

And of course, the known canonical position that Rebel leaders GATHERED on Yavin and STAYED.

[Tiriol]

The Death Star debate actually just rankles more of Lousy Rebel thinking.

Think about it. You sent 500+ X-wings and you failed to take out the Death Star. Yet, you expect a smaller snubfighter attack to succeed, because the Empire hasn't failed to consider a snubfighter a threat and has weaker screens? Oh, but you have a one shot kill now!

And frankly, why the hell would anyone send snubfighters to take on a Death Star? Why not some Rebel cap ships?

And of course, the known canonical position that Rebel leaders GATHERED on Yavin and STAYED.

The problem at that point was that the Rebels didn't have enough capital ships as it was, or maybe none at all (the Mon Cal and their fleet hadn't yet joined the cause, if I recall correctly). And it was pretty clear to me that the Rebel starfighter assault on the Death Star was a desperate, last-moment measure - to utilize the single weakness they found in the behemoth hoping that universe might spare them.

[PhilosopherOfSorts]

Send the capital ships out to do what? Even something the size of an Executer would be, depending on if the superlaser could target it, either a momentary distraction or, at most, a minor irritation to the Death Star.

The fighers might not have had much of a chance, even knowing about the exaust port, but they had a better chance than a rebel fleet assault would.

Its the differance between certain death and uncertain death.

[Simon_Jester]

The Death Star debate actually just rankles more of Lousy Rebel thinking.

Think about it. You sent 500+ X-wings and you failed to take out the Death Star. Yet, you expect a smaller snubfighter attack to succeed, because the Empire hasn't failed to consider a snubfighter a threat and has weaker screens? Oh, but you have a one shot kill now.

If you have the fighters, if you have a slightly credible chance of making the plan work, and if you're about to lose a base many times more valuable than the fighters... why not?

I get the feeling that if we're going to incorporate the mass-scale X-wing attack, the simplest answer is that the Rebels didn't realize just how far along the construction really was. They were picturing a battle station still under construction- one with its reactors cold, its defense batteries not yet installed, and quite possibly large gaps in the superstructure that fighters could fly into to get to the interior and do real damage. Then their admiral panicked and goofed when (he? she?) saw a "fully armed and operational battle station" in front of her.

Another possibility- whoever dispatched the mission was thinking in terms of shooting up the support infrastructure, not the Death Star itself. That would at least delay construction. And, again, the admiral in charge of the carrier operation panicked and goofed.

[Serafina]

The Death Star debate actually just rankles more of Lousy Rebel thinking.

Think about it. You sent 500+ X-wings and you failed to take out the Death Star. Yet, you expect a smaller snubfighter attack to succeed, because the Empire hasn't failed to consider a snubfighter a threat and has weaker screens? Oh, but you have a one shot kill now.

If you have the fighters, if you have a slightly credible chance of making the plan work, and if you're about to lose a base many times more valuable than the fighters... why not?

I get the feeling that if we're going to incorporate the mass-scale X-wing attack, the simplest answer is that the Rebels didn't realize just how far along the construction really was. They were picturing a battle station still under construction- one with its reactors cold, its defense batteries not yet installed, and quite possibly large gaps in the superstructure that fighters could fly into to get to the interior and do real damage. Then their admiral panicked and goofed when (he? she?) saw a "fully armed and operational battle station" in front of her.

Another possibility- whoever dispatched the mission was thinking in terms of shooting up the support infrastructure, not the Death Star itself. That would at least delay construction. And, again, the admiral in charge of the carrier operation panicked and goofed.

No.
The simplest answer is:
An attack with fighters on such a massive battlestation is simply suicidal. Even the best pilots lead by the best commander ever would have no chance.

Unless you have a weak point like DS-I had. And the rebels did not know about it during that attack.

There is NO way you can deal enough damage with fighters if the Death Star is even halfway finished to "destroy" it, simply due to its sheer mass. Thats like taking on a mountain with a spoon - you might actually carve some small "holes" into it, but it hardly matters.

Both Death Stars were destroyed by an explosion from their own reactor. Otherwise, even a whole fleet would have needed a long, long time to destroy it, even if it did not fight back.

You are propably right that the rebels did not expect real resistance during their attack - but there is no need for anyone to panick. They just stand no chance.

[FSTargetDrone]

Remember, Dodonna's very words about the Death Star:

"Its defences are designed around a direct, large-scale assault. A small, one-man fighter should be able to penetrate the outer defense."

The simplest answer is:
An attack with fighters on such a massive battlestation is simply suicidal. Even the best pilots lead by the best commander ever would have no chance.

Unless you have a weak point like DS-I had. And the rebels did not know about it during that attack.

What? Of course they knew about it. And of course they thought they had a chance, or at least the mission planners did, when Dodonna goes on to say how the Empire "doesn't consider a small one-man fighter to be any threat, or they'd have a tighter defense. An analysis of the plans provided by Princess Leia has demonstrated a weakness in the battle station." That's the entire point of the briefing in which Dodonna goes into detail about the exhaust port and the chain reaction.

[Thanas]

^They did not know about it during the first 500+ fighter attack, that is what she means.

[FSTargetDrone]

^They did not know about it during the first 500+ fighter attack, that is what she means.

Ah, I stand corrected. Sorry Serafina!

[Simon_Jester]

No.
The simplest answer is:
An attack with fighters on such a massive battlestation is simply suicidal. Even the best pilots lead by the best commander ever would have no chance.

Unless you have a weak point like DS-I had. And the rebels did not know about it during that attack.

There is NO way you can deal enough damage with fighters if the Death Star is even halfway finished to "destroy" it, simply due to its sheer mass. Thats like taking on a mountain with a spoon - you might actually carve some small "holes" into it, but it hardly matters.

Both Death Stars were destroyed by an explosion from their own reactor. Otherwise, even a whole fleet would have needed a long, long time to destroy it, even if it did not fight back.

I'm not sure you're clear on what I meant. I must have messed up my presentation.

First, we have the distinction between "mission kill" and "blast it into vapor." No plausible number of X-wings could possibly carry enough megatonnage to blow the Death Star into little pieces, I agree, but that wasn't what I was talking about. The Death Star is a massive amount of steel* wrapped around what almost has to be a great deal of sensitive, expensive equipment; if superlasers were easy to build everyone would have one.

*or some steel-like material

The Rebels aren't carrying enough firepower to destroy all the steel outright, but if they can get at the internal components then they don't have to. Attacking a partially completed station with little opposition, they would be able to probe the interior, identify stuff that looks expensive and hard to replace, and blast it. The main armor belt and shields might be designed to stand up against anything up to and including concentrated teraton range energy weapon strikes, but the goal here would be to bypass those defenses by attacking before they are fully assembled. Computers, power plants, and superlaser focusing systems are going to be a lot easier to damage than kilometer-thick armor plate. And before construction is complete, while there are still holes in the superstructure, it's still possible to get at those components with guided missiles.

If a mission like that worked, it would NOT end with the Death Star hull being physically blown apart, but the damage to critical "avionics" would be great enough to set construction back by months or years while replacement parts were fabricated and flown in. And since you're trying to inflict a mission kill on the Death Star, not to vaporize it, so its sheer mass is irrelevant.

Hence my point: the best explanation for the fighter attack is that the carrier was sent in expecting to encounter a construction site with an unfinished Death Star that had exposed components which could realistically be damaged using megaton-range weaponry. This seems a lot more likely than "the Rebels did something colossally dumb knowing in advance that it could never work."

Of course, this would only be possible if the Death Star's armor belt, shielding, and turbolasers weren't on line (much as the Rebels believed to be true of the DSII going into the Battle of Endor).

[Serafina]

Star Wars HAS demonstrated to have a lot of backup systems.
So there propably is a LOT of stuff to destroy.

Granted, you could cripple the station that way.

But the question is - how much use is it?

There hardly is any unreplacable equipment on the Death Start - it is using everyday military technology, scaled up to eleven.
Superlasers ARE everyday military equipment - they are used on the Clones LAATs (the skimmers)

So, even if you blast most of the equipment to bits - it will only delay the building, not stop it.
And the delay propably not be that long.


And the point really is:
If the Rebels fail with a LARGE starfighter attack on the UNFINISHED Death Star and FAIL to do any damage, would you worry if they attack in smaller numbers, against a shielded, armed and amored one?

[Simon_Jester]

Star Wars HAS demonstrated to have a lot of backup systems.
So there propably is a LOT of stuff to destroy.

Granted, you could cripple the station that way.

But the question is - how much use is it?

There hardly is any unreplacable equipment on the Death Start - it is using everyday military technology, scaled up to eleven.
Superlasers ARE everyday military equipment - they are used on the Clones LAATs (the skimmers)

Yes, and battleship sized artillery pieces were (broadly speaking) just scaled up breech-loading rifles. That doesn't mean that they were cheap throwaway items; nations that needed heavy naval artillery would go well out of their way to reuse existing guns rather than commission new ones.*

Scaling equipment up isn't cheap, and you can't do it without rearranging your factory to produce the scaled up parts. When you're talking about superheavy items in low demand (there will only ever be, say, one to a hundred of them in all the world), very few facilities will be set up to make them. And there's no economy of scale in manufacturing them (again, because demand was so low). That makes for very long lead times in production, and similarly long lead times if you have to order another set after the manufacturer thought he was done making them for you.

If the analogy to existing naval construction holds, destroying expensive pieces of equipment with long production lead times could set construction back by many months, even by years. Artifacts that size aren't slapped together from off the shelf parts over a week of working overtime.

*You see a lot of this in, for instance, Churchill's histories of the World Wars. He spent several years in charge of the British Navy during major periods of naval construction, and there was a fair amount of talk taking the form of "take guns from Obsolete Battleship X and use them for purpose Y." The guns themselves were treated as valuable capital equipment, with good reason.
________

I'm not talking about this as if it would be a decisive attack. But a lot of things get done in war not because they will end everything with one shot, but to buy time to come up with something else, and I think the massed X-wing attack in Death Star makes more sense as one of them. It's a spoiling attack, one they probably launched because they couldn't scrape up the firepower to do anything more.

And the point really is:
If the Rebels fail with a LARGE starfighter attack on the UNFINISHED Death Star and FAIL to do any damage, would you worry if they attack in smaller numbers, against a shielded, armed and amored one?

No, not particularly. I think everyone agrees on that.

[Serafina]

If the analogy to existing naval construction holds, destroying expensive pieces of equipment with long production lead times could set construction back by many months, even by years. Artifacts that size aren't slapped together from off the shelf parts over a week of working overtime.

It does - to a certain extent.
A lot of the scaled-up equipment on the death star would be hard to replace.
Oh, but wait - what is actually scaled up on the death star?

The Superlaser and the Reactor - everything else ins NOT scaled up.
The Turbolasers are normal turbolasers, the electric equipment was on the same scale, it's tractor beams were just tractor beams and so on.

You have TWO targets where you can cause actual damage because they MIGHT be hard to replace.

And that assumes that your analogy applies far enough. Which is questionable.
Why?
Again, simple: We know that DS-II was constructed from raw materials - because only raw materials were delivered to it.
This means that they either have to construct factories inside the Death Star (because we did not saw them on the outside) or that the stuff is molecuarly assembled on the spot.
Propably a mixture of the two things.

Either way, there is no shortage of production facilities.


But all of this is moot - the Rebels failed to do any damage with a large attack against the unfinished battlestation.
Would YOU worry, as an imperial officer, if they attack your finished station with a way smaller force?

To use an naval analogy: One hundred planes are raiding your superbattleship while it is still under construction. It takes no damage.
Now, it is ready, and is attacked by a single plane - do you worry about that?

[Simon_Jester]

It does - to a certain extent.
A lot of the scaled-up equipment on the death star would be hard to replace.
Oh, but wait - what is actually scaled up on the death star?

The Superlaser and the Reactor - everything else is NOT scaled up.
The Turbolasers are normal turbolasers, the electric equipment was on the same scale, it's tractor beams were just tractor beams and so on.

I submit that the engines and hyperdrive must have been scaled up considerably.

Look, I agree that many of the Death Star's systems could be based on off-the-shelf hardware. If nothing else, you can use many small systems in parallel. But the exceptions are important enough that serious damage to them would still have to be a major setback in construction. The Death Star is relatively useless without the superlaser even if the rest of it is in perfect working order. Even if you're assembling the superlaser parts on the spot from raw materials, you'll still have to stop and make them over again... and Heaven help you if the attack damages your manufacturing equipment.

To reiterate, this would likely not be a decisive blow to the Death Star program, but it could still cause serious time and cost overruns, which would buy the Rebellion time to act in other ways against the program directly or indirectly.
________

But all of this is moot - the Rebels failed to do any damage with a large attack against the unfinished battlestation.
Would YOU worry, as an imperial officer, if they attack your finished station with a way smaller force?

As I said before in response to your last post:

And the point really is:
If the Rebels fail with a LARGE starfighter attack on the UNFINISHED Death Star and FAIL to do any damage, would you worry if they attack in smaller numbers, against a shielded, armed and amored one?

No, not particularly. I think everyone agrees on that.

[Serafina]

Oh, ok - sorry for overreading your concession.

To reiterate, this would likely not be a decisive blow to the Death Star program, but it could still cause serious time and cost overruns, which would buy the Rebellion time to act in other ways against the program directly or indirectly.

It certainly would. But what good would it be?

If the empire notices that the site has been compromised AND can be sucessfully attacked, then they are certainly going to reinforce it.
Which, in turn, makes any "real" attack even more difficult.

The main weapon of the Death Star is not its superlaser - it's sheer size.
Even if you somehow disable the superlaser, take out its hyperdrive and half its weapons - it's still an armored giant battlemoon which can supply a whole sector fleet.

The point is?
It is very, very hard to destroy the Death Star by conventional means. you could propably raze it with a fleet big enough - but did the Rebellion have such an fleet?
I doubt that even the whole MonCal fleet could beat DS1 even without the Superlaser or any reinforcements.

Therefore, an attack on its building site has very, very few chances to actually suceed.

[Thanas]

I am not so sure about the MonCal fleet. As they were able to keep the whole empire at bay and still supply the rebellion with warships, they must have had a very strong capital ship fleet numbering at least several hundreds, if not thousands of heavy cruisers.

[The Romulan Republic]

I am not so sure about the MonCal fleet. As they were able to keep the whole empire at bay and still supply the rebellion with warships, they must have had a very strong capital ship fleet numbering at least several hundreds, if not thousands of heavy cruisers.

Or the Empire (despite its unquestionably vast military) was spread rather thin patrolling an entire Galaxy to maintain order, while the Mon Calimari only had to defend a single sector at most? Mon Mothma basically states in RotJ that the Imperial fleet is spread around the Galaxy Rebel-hunting, so its not so unreasonable to assume they might be feeling some troop shortages. Also, if Mon Calimari had a planetary sheild (I'm not certain weather it canonically did, but I would expect such a major world to have at least theatre sheilds over the most populated areas), then an attack by the Empire might have turned into a lengthy seige without a Superlaser.

I'm not disagreeing that the Mon Cals had a big fleet. Perhaps a match for a couple of Sector fleets at least (assuming that they had about a Sector fleet's worth going up against the DS2, and that they kept a comparable portion of their fleet on defense). Just that it didn't have to be that big. "Thousands of heavy cruisers" would arguably equal a large fraction of the Empire's entire fleet, and while there are admittedly big chunks of the EU with which I am unfamiliar, I can't think of anything in-canon to support such numbers. Nor do I see one world that only recently overthrew its enslavers being able to field that kind of a force.

[Thanas]

I am not so sure about the MonCal fleet. As they were able to keep the whole empire at bay and still supply the rebellion with warships, they must have had a very strong capital ship fleet numbering at least several hundreds, if not thousands of heavy cruisers.

Or the Empire (despite its unquestionably vast military) was spread rather thin patrolling an entire Galaxy to maintain order, while the Mon Calimari only had to defend a single sector at most? Mon Mothma basically states in RotJ that the Imperial fleet is spread around the Galaxy Rebel-hunting, so its not so unreasonable to assume they might be feeling some troop shortages. Also, if Mon Calimari had a planetary sheild (I'm not certain weather it canonically did, but I would expect such a major world to have at least theatre sheilds over the most populated areas), then an attack by the Empire might have turned into a lengthy seige without a Superlaser.

Mon Calamari did have a planetary shield. However, one would think the empire would have spared at least a few sector groups to use against them. Remember that the Hapans, a minor power that was not known for having much combat experience, did rate at least 60 ISDs as occupation forces (and those were only the ones the Hapans captured when the Empire withdrew).

As the MonCal are way more important than the Hapans, I would expect the empire to have a magnitude of more forces. And while the planet is defended by a shield, the shipyards demonstrably are not, so the MonCal would have needed a large fleet to defend them - as well as the rest of their territory.

So no, a fleet of hundreds of Cruisers or even in the small thousands does not seem excessive to me. Especially considering that it is one of the big five/six shipyard worlds in the galaxy.

[Darth Tanner]

Mon Calamari did have a planetary shield.

It didn't have one operational for the World Devastator attack although I understand that there was one for the intial Imperial invasion but it was sabotaged by the Quarren. If they did have one would a couple of sector fleets be enough? If it was comparable to Alderaans then it could soak up a huge fleet for months of constant bombardment which the Empire is unlikely to be able to spare.

did rate at least 60 ISDs as occupation forces

Occupation forces? I understood it that the Hapan Queen handed over a lot of rogue Jedi in order to get the Empire to ignore them. The ISDs they had were captured from the warlords that tried to muscle in on their territory in the post endor apocalypse of the warlord period.

As they were able to keep the whole empire at bay

I thought Moncal was enslaved by the Empire (Hence Ackbar being Tarkins slave) and that the reason their fleet was with the rebels was because they ran away rather than be seized by the Empire when the planet fell.