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Either my calculations are wrong or a single star destroyer can shrug off a two mile diameter rock traveling at .5 C.
My calculations as follows: 4000m*4000m*4000m*10000(Kg per cubic meter)*94000mps^2

Well, I don't have the numbers for the Star Destroyer's shields in my head but, firstly, your formula is a bit wrong. Kinetic energy is calculated by
E = 0.5*(m*v^2)
Seems like you forgot divide it by 2. Also, did you convert your miles to metres in your calculation?

Secondly, anything travelling at 0.5c would be subject to relativistic effects and so would have about 15% more kinetic energy than the normal formula gives. The relativistic formula for kinetic energy being
E = γmc^2 - mc^2
where
γ = 1 / (sqrt(1 - (v/c)^2))

If I did my math right said rock would have a KE of 8.9x10^30 Joules. Well above what an ISD can handle with its shields.

fusion wrote:Either my calculations are wrong or a single star destroyer can shrug off a two mile diameter rock traveling at .5 C.
My calculations as follows: 4000m*4000m*4000m*10000(Kg per cubic meter)*94000mps^2

A 2 mile diameter rock has a hell of a lot of momentum. Momentum is conserved. Just how strong are the bolts that hold the shield generator to the space ship?

Put another way, I can take a thimblefull of scalding water and toss it on your forhead, giving you an annoying burn Alternatively, I can shoot you in the face with a .45 having the same amount of joules in KE as would be delivered through heat by the water. Which one hurts more?

Perhaps it should also be pointed out that 2 miles is not 4 000 metres, but closer to 3 200. And a volume with a diameter would ordinarily be assumed to be somewhat spherical and not cubical...
It won't affect the result very much though, but still...

I got 7.19x10^30J without correcting for relativity. With, it's about 115% of that, 8.27e30.

Another important consideration is POWER. That is, those 8.27e30 joules are delivered in 1/37000th of a second, so the SD needs to shed power at a rate of ~3.1x10^35 watts.

Hehe, memories... One of the first threads I posted in here was "How many Borg Cubes would it take to kill 1 Star Destroyer?" and I concluded their best shot would be to crash into it at near C...

Feil wrote:

fusion wrote:Either my calculations are wrong or a single star destroyer can shrug off a two mile diameter rock traveling at .5 C.
My calculations as follows: 4000m*4000m*4000m*10000(Kg per cubic meter)*94000mps^2

A 2 mile diameter rock has a hell of a lot of momentum. Momentum is conserved. Just how strong are the bolts that hold the shield generator to the space ship?

Put another way, I can take a thimblefull of scalding water and toss it on your forhead, giving you an annoying burn Alternatively, I can shoot you in the face with a .45 having the same amount of joules in KE as would be delivered through heat by the water. Which one hurts more?

Excellent point. A physical impactor like an asteroid delivers energy in a very different way than a directed-energy beam weapon, like a turbolaser bolt.
Fortunately, we have the precedent of three Imperator-class Star Destroyers colliding with the Executor, thus demonstrating that shield systems are designed to protect a ship against that sort of attack.
Anyway, were that not the case, we should expect to see "ramships" or even asteroids-with-engines-strapped-on being used as a common means of anti-capital ship attack.

When we talk about shield strength, though, we generally use heat capacity, not kinetic energy dumping, don't we?

Cykeisme wrote:

Feil wrote:

fusion wrote:Either my calculations are wrong or a single star destroyer can shrug off a two mile diameter rock traveling at .5 C.
My calculations as follows: 4000m*4000m*4000m*10000(Kg per cubic meter)*94000mps^2

A 2 mile diameter rock has a hell of a lot of momentum. Momentum is conserved. Just how strong are the bolts that hold the shield generator to the space ship?

Put another way, I can take a thimblefull of scalding water and toss it on your forhead, giving you an annoying burn Alternatively, I can shoot you in the face with a .45 having the same amount of joules in KE as would be delivered through heat by the water. Which one hurts more?

Excellent point. A physical impactor like an asteroid delivers energy in a very different way than a directed-energy beam weapon, like a turbolaser bolt.
Fortunately, we have the precedent of three Imperator-class Star Destroyers colliding with the Executor, thus demonstrating that shield systems are designed to protect a ship against that sort of attack.
Anyway, were that not the case, we should expect to see "ramships" or even asteroids-with-engines-strapped-on being used as a common means of anti-capital ship attack.

Well, the Executors shields were down for a while after that incident and we see ram-ships used during the Corellia-trilogy.

Cykeisme wrote: Fortunately, we have the precedent of three Imperator-class Star Destroyers colliding with the Executor, thus demonstrating that shield systems are designed to protect a ship against that sort of attack.

Were those Imperators moving at any significant velocity relative to the Executor? As I recall, they were exiting hyperspace into formation, and came a little too close. One would assume that if they were planning to begin station-keeping upon entry to realspace, their realspace velocities would be almost equal to those of the Executor. I'm not contesting that starships have impressive abilities to withstand physical impacts, but It seems a situation where annihilation energy (I presume) was absorbed by the Executor in a fairly low-momentum circumstance isn't any more impressive than withstanding barrages from Mon Calamari cruisers at Endor.

Except a small asteroid moving at slow velocities banged up the Star Destroyer pretty well in the movies.

Where the shields were down for the holo-conference.

Isn't there any other way to explain that asteroid strike, because it strikes me as a tad silly that they would drop shields just to have a chat about being unable to find the Falcon, considering that they were in an asteroid field which could only cause them damage if they lowered shields. Why not use a burst transmission?

Besides the fact that physical impacts cause damage differently than energy weapons do, aren't there separate ray and particle shields?

Feil wrote:

Were those Imperators moving at any significant velocity relative to the Executor?

Yes, Admiral Griff's three destroyers exited hyperspace at relativistic speeds right on top of the Executor. They never even slowed significantly, as they arn't even visible at impact. So, at minimum greater than 0.5 c. The three impactors were annihilated, and Executor was unscathed but suffered serious temporary shield loss, requiring it to delay its mission.

As I recall, they were exiting hyperspace into formation, and came a little too close. One would assume that if they were planning to begin station-keeping upon entry to realspace, their realspace velocities would be almost equal to those of the Executor.

No. Admiral Griff was trying to show up Lord Vader, who he had a continuing rivalry with. They were NOT trying to join a formation. They were trying to show up the Executor and Vader up by capturing a group of fleeing rebels first.

I'm not contesting that starships have impressive abilities to withstand physical impacts, but It seems a situation where annihilation energy (I presume) was absorbed by the Executor in a fairly low-momentum circumstance isn't any more impressive than withstanding barrages from Mon Calamari cruisers at Endor.

Turbolasers being energy weapons are primarily thermal in nature and carry comparatively little momentum. To calculate the momentum of a massless particle you can used U/c. Even the 8.3E23 J yeild of an ISD I's - Heavy Turbolaser (198 Teratons) only carries 2.8E15 J (667 kilotons) of momentum. Which according to AOTC:ICS isn't enough to more than score the hull of a warship.

Its also worth noting that Ramships were used by the rebels at the battle of Endor according to the ROTJ novelization with little no effect; as not a single vessel is either lost of even mentioned as being severly damaged by them. Also according to Slave ships the bracing for the guns and most likely sheild generators and tractor beam emplacements can withstand the equivalent of gigatons of momentum. You would be hard pressed to find examples of SW ships being weak to kinetic impacts. As there are many examples of even larger ships such as ISD's crash landing on planets, relatively intact, and in some instances salvageable.

Lazarus wrote:

Isn't there any other way to explain that asteroid strike, because it strikes me as a tad silly that they would drop shields just to have a chat about being unable to find the Falcon, considering that they were in an asteroid field which could only cause them damage if they lowered shields. Why not use a burst transmission?

It is no siller than the Emperor using himself as bait at Endor. When a Sith lord orders you to holo-conference, you holo-conference...or you take a mandatory retirement the hard way. Seriously, none of those captains wanted to even be in the asteroid field to begin with. but it is the Death Squadron, so their undoubtedly used to following orders without question. As far as Vader is concerned, he had nothing to worry about, he has precognition afterall. As far he's concerned he was willing to sacrifice all their lives to regain his only son.

Spartan wrote:Turbolasers being energy weapons are primarily thermal in nature and carry comparatively little momentum. To calculate the momentum of a massless particle you can used U/c. Even the 8.3E23 J yeild of an ISD I's - Heavy Turbolaser (198 Teratons) only carries 2.8E15 J (667 kilotons) of momentum. Which according to AOTC:ICS isn't enough to more than score the hull of a warship.

Does the ICS really measure the strength of the hull in joules? That seems strange. Also, you measure momentum in kgm/s, not joules...

Nope, it says that SW level fusion rockets can barely scratch a warships neutronium clad hull. But your right I should have expresses momentum in joules.

Ghetto edit:

That should say: Your right I should not have expressed momentum in joules.

Cykeisme wrote:Fortunately, we have the precedent of three Imperator-class Star Destroyers colliding with the Executor, thus demonstrating that shield systems are designed to protect a ship against that sort of attack.

Of course they are. The question is: how much? A piece of nylon can protect against physical attack too, but it's a question of what its limits are.

Surlethe wrote:When we talk about shield strength, though, we generally use heat capacity, not kinetic energy dumping, don't we?

We talk about whatever effect the attack will have on the shields. In the case of a turbolaser strike, some energy is deflected and some is absorbed into the shield system, in addition to waste heat created by the process. In that situation, we typically talk about heat capacity since that is what will typically cause the shield system to fail.

In the case of a massive kinetic impact (like an asteroid or a collision between two starships), we talk about momentum, since the momentum transfer will likely knock the shield equipment off of its mountings before the shield equipment overheats and burns out.

Mad wrote:

Surlethe wrote:When we talk about shield strength, though, we generally use heat capacity, not kinetic energy dumping, don't we?

We talk about whatever effect the attack will have on the shields. In the case of a turbolaser strike, some energy is deflected and some is absorbed into the shield system, in addition to waste heat created by the process. In that situation, we typically talk about heat capacity since that is what will typically cause the shield system to fail.

In the case of a massive kinetic impact (like an asteroid or a collision between two starships), we talk about momentum, since the momentum transfer will likely knock the shield equipment off of its mountings before the shield equipment overheats and burns out.

Another possibility is that the shield generator's innards will be deformed to the point that it stops working, which is a variation upon the previous idea. My original webpage explaining the article assumed rigidity of the device itself purely for the sake of simplicity, in the hopes that people would find it easier to understand.

Spartan wrote:Even the 8.3E23 J yeild of an ISD I's - Heavy Turbolaser (198 Teratons)

I've looked everywhere for the yeild of an ISDs HTL's.. where does 198 TTs come from? And is that per gun or per turret?

Darth Wong wrote:

Mad wrote:

Surlethe wrote:When we talk about shield strength, though, we generally use heat capacity, not kinetic energy dumping, don't we?

We talk about whatever effect the attack will have on the shields. In the case of a turbolaser strike, some energy is deflected and some is absorbed into the shield system, in addition to waste heat created by the process. In that situation, we typically talk about heat capacity since that is what will typically cause the shield system to fail.

In the case of a massive kinetic impact (like an asteroid or a collision between two starships), we talk about momentum, since the momentum transfer will likely knock the shield equipment off of its mountings before the shield equipment overheats and burns out.

Another possibility is that the shield generator's innards will be deformed to the point that it stops working, which is a variation upon the previous idea. My original webpage explaining the article assumed rigidity of the device itself purely for the sake of simplicity, in the hopes that people would find it easier to understand.

Something I always meant to ask about: Are the shields directly in contact with the hull? If not, could they have an effect where a physical impactor pushes them inwards to the hull to dissapate some of the momentum?

SVPD wrote:Something I always meant to ask about: Are the shields directly in contact with the hull? If not, could they have an effect where a physical impactor pushes them inwards to the hull to dissapate some of the momentum?

You can't "dissipate" momentum; you can only control the manner in which it is transferred, in order to distribute the reaction forces over as large a surface area of load-bearing structure as possible. You could very easily design a shield generator to decelerate impactors but not enough to keep them from touching the hull at all, and this may in fact be the case for SW shields.