Mass extinction from Star Destroyer crash?

[cubinator]

The Chixulub impactor was about 10 km wide, and it is largely accepted as the primary cause of the Cretaceous extinction. A typical Star Destroyer is a little over a kilometer long, and the Super Star Destroyer Executor was reportedly 19 km long:

This implies that, if Executor ran off course and impacted a planet, it would have as much effect or more than the apocalyptic asteroid. Of course, it depends on it's speed on impact, and what happens to any nuclear reactors on board, but I find it interesting that the ship is large enough to have such an effect on a planet if it crashed. Thoughts?

[gogozerg]

Oh, now I understand why it has an aerodynamic shape. For maximum impact velocity at ground level.

[StrandedonEarth]

The dimensions aren't as important as the mass. SSD's are hollow metal lattices, with over a quarter million meaty bags of water aboard. So they probably don't mass nearly as much as an asteroid of similar dimensions. Velocity is where the kinetic energy really kicks in, given that kinetic energy equals mass times the square of velocity.

Large asteroid impacts dwarf nuclear weapons. The power generating capabilities of an SSD's reactors are unknown, but they have to power a heckuva lot of weapons, engines, and other equipment on board. So I would hazard the guess that compared to a similarly sized asteroid, most of the destructive potential would come from the reactors.

OTOH, in Timothy Zahn's Heir to the Empire trilogy (an excellent read, by the way; I wish Ep.7 had been based on it) an old capital ship crash had poisoned a planet with its chemical fallout, and the inhabitants there probably would have gone extinct if not for intervention by Lord Vader and the Empire

[cantab]

Yeah, it entirely depends on speed. As far as what actually happens in Star Wars and the "Extended Universe" goes, there are of course a few examples.

Most obviously, we see the large spacecraft in The Force Awakens, and it turns out that's an Executor-class. Its low-speed crash landing, slow enough for the ship to survive largely intact, did not significantly affect the planet.

At the other extreme, a planet that was hit by a large starship in hyperspace was "fractured to the core", likely rendering it uninhabitable.

But how fast might a Star Wars ship ram a planet in "normal space"? It's hard to know, because they don't appear to follow normal orbital mechanics and their speeds are quoted in fictitious units of "Megalights (MGLT)" or "MGLT per hour".

It's shown, in a background shot, that the Death Star was about 3 Megalights from Alderaan when it fired. And the novel mentions it's about "six planetary diameters" away, and Alderaan is about the size of Earth. That suggests that 1 MGLT is 25,000 km.

Then we know that the Imperial (I) Star Destroyer could do 60 MGLT. Yeah, Star Wars using the same unit name for speed and distance, whee. But it's probably 60 MGLT per hour, so 1.5 million km/h or 400-ish km/s.

That's fast, even by full scale solar system standards. The fastest anything on a solar orbit can hit Earth is 72 km/s.

What about mass and density? Well, no idea, maybe I'll look into it later. But with that speed meaning that kilo-for-kilo a Star Wars ship at full speed would be about a hundred times as destructive as a natural Earth impactor, and with the general scale of Star Destroyers, I feel confident that full-speed ramming would be immediately devastating and likely render much if not all life on the planet extinct. Though in practice in the Star Wars Universe, decent planetary shields would stop it.

It's a waste of a good Star Destroyer though, considering that a single ISD could use its guns to turn the entire planetary surface to glass and kill everything on it in about a day. (Again provided it's not opposed by shields or surface weaponry).

[StrandedonEarth]

52 minutes ago, cantab said:

Then we know that the Imperial (I) Star Destroyer could do 60 MGLT. Yeah, Star Wars using the same unit name for speed and distance, whee. But it's probably 60 MGLT per hour, so 1.5 million km/h or 400-ish km/s

Wow, I had no idea what the top normal-space speed of an ISD was. That skews the kinetic-energy equation a bit. But it's still only 0.13% of lightspeed! Not even relativistic! Good thing they have hyperdrive.

[magnemoe]

1 hour ago, gogozerg said:

Oh, now I understand why it has an aerodynamic shape. For maximum impact velocity at ground level.

As I understand the guns is along the sides, It would be stupid not to let the guns traverse fully forward  
 point it against target and most guns could aim at target while it had an minimal cross section. 
Lots of the combat in Star Wars is based on WW2 combat however the capital ships fight in 3 dimensions. 
 

[todofwar]

14 hours ago, StrandedonEarth said:

The dimensions aren't as important as the mass. SSD's are hollow metal lattices, with over a quarter million meaty bags of water aboard. So they probably don't mass nearly as much as an asteroid of similar dimensions. Velocity is where the kinetic energy really kicks in, given that kinetic energy equals mass times the square of velocity.

Large asteroid impacts dwarf nuclear weapons. The power generating capabilities of an SSD's reactors are unknown, but they have to power a heckuva lot of weapons, engines, and other equipment on board. So I would hazard the guess that compared to a similarly sized asteroid, most of the destructive potential would come from the reactors.

OTOH, in Timothy Zahn's Heir to the Empire trilogy (an excellent read, by the way; I wish Ep.7 had been based on it) an old capital ship crash had poisoned a planet with its chemical fallout, and the inhabitants there probably would have gone extinct if not for intervention by Lord Vader and the Empire

I thought it wasn't just the impact of one ship but the fallout from a decent sized battle. Also, they were actively poisoning the planet in order to keep the local population subservient since they were very good assassins.

[kerbiloid]

SW ships widely use hypereditjump. Megalight is not necessary a unit of length. It can be an energetical or temporal-fugue-ian unit. Like "yet 3 Snickers and 2 diapers to target" and two different megalights are not necessary equal in kilometers.

Maybe just take a 1 km-destroyer as scaled 3 times battleship and get its mass as 3^2.5 ~= 15 times heavier than a typical battleship, i.e. ~1 mln tonnes,

Edited November 14, 2016 by kerbiloid

[_Augustus_]

In Episode VI the Executor crashes into the Death Star but does next to no damage.

At the Battle of Jakku the Super Star Destroyer known as the Ravager directly impacted the surface, but didn't wipe out everything on the surface, unless maybe Jakku wasn't always desert...

Edited November 14, 2016 by _Augustus_

[cubinator]

1 hour ago, _Augustus_ said:

In Episode VI the Executor crashes into the Death Star but does next to no damage.

The Death Star had big shields, I suppose.

1 hour ago, _Augustus_ said:

At the Battle of Jakku the Super Star Destroyer known as the Ravager directly impacted the surface, but didn't wipe out everything on the surface, unless maybe Jakku wasn't always desert...

It probably wasn't going as fast as the Chicxulub impactor.  It likely wasn't going very fast in the first place and also had a chance to brake. But if it had been traveling at 20 km/s, Jakku would likely have had Problems™.

[Mikki]

20 hours ago, cubinator said:

Thoughts?

With sufficient amount of dark ene force on board - yes.

[kerbiloid]

1 hour ago, cubinator said:

It likely wasn't going very fast in the first place and also had a chance to brake.

We can watch IV or VI (don't remember) episode of SW where a destroyer impacts a planet and measure with the player timescale how many seconds did it take to penetrate atmosphere. The thickness of visible atmosphere we can estimate.
(Can't do this right now, as it would require to find where are SW)

 

[cubinator]

7 minutes ago, kerbiloid said:

We can watch IV or VI (don't remember) episode of SW where a destroyer impacts a planet and measure with the player timescale how many seconds did it take to penetrate atmosphere. The thickness of visible atmosphere we can estimate.
(Can't do this right now, as it would require to find where are SW)

 

A SSD impacts Death Star II in VI. There's also the bit where one breaks up on reentry over Coruscant in episode III.

[DDE]

3 hours ago, _Augustus_ said:

In Episode VI the Executor crashes into the Death Star but does next to no damage.

At the Battle of Jakku the Super Star Destroyer known as the Ravager directly impacted the surface, but didn't wipe out everything on the surface, unless maybe Jakku wasn't always desert...

It was a desert back when it fell.

BTW, there are plenty of Star Destroyers falling out of the sky in the new Battlefront.

1 hour ago, cubinator said:

The Death Star had big shields, I suppose.

The escalation of shield efficacy in SW is crazy. The Executor took three FTL Star Destroyer impacts without suffering a single casualty by console explosion.

19 hours ago, magnemoe said:

As I understand the guns is along the sides, It would be stupid not to let the guns traverse fully forward  

There's a minor problem with this on the basic ISDs. The main guns are clustered in batteries around the command tower, with next to no firing arc whatsoever.

[DDE]

4 minutes ago, cubinator said:

There's also the bit where one breaks up on reentry over Coruscant in episode III.

The Invisible Hand - way to turn Adam Smith into a perpetual motion machine - is a much smaller spacecraft than classic SSDs, let alone the big bad boy above, or its cousins made by Hsiao; plus landing was a glancing descent.

However, it does give us a valuable data point: most SW ships stay in a quasi-orbit using hovering technology, and hence crash merely at terminal velocity.

Spoiler

Bonus: that big boy isn't the only super SSD in the Legends canon anymore.

And somebody has leaked the info on the design of USS South Carolina to the Empire:

 

[Matuchkin]

21 hours ago, StrandedonEarth said:

OTOH, in Timothy Zahn's Heir to the Empire trilogy (an excellent read, by the way; I wish Ep.7 had been based on it) an old capital ship crash had poisoned a planet with its chemical fallout, and the inhabitants there probably would have gone extinct if not for intervention by Lord Vader and the Empire

That really reminds me of Ray Bradbury's Frost and Fire.

Just now, DDE said:

Wait, why do the engine nozzles resemble those of jet engines? Would ion engines (or whatever high-efficiency stuff they use) need such nozzles? And how do the kilometer wide plumes of million-degree-centigrade exhaust affect the atmosphere/ environment of the planets they are sometimes used in?

[magnemoe]

1 hour ago, DDE said:

It was a desert back when it fell.

BTW, there are plenty of Star Destroyers falling out of the sky in the new Battlefront.

The escalation of shield efficacy in SW is crazy. The Executor took three FTL Star Destroyer impacts without suffering a single casualty by console explosion.

There's a minor problem with this on the basic ISDs. The main guns are clustered in batteries around the command tower, with next to no firing arc whatsoever.

its no reason why consoles should explode, they don't have internal batteries like phones
Nor is it any reason to use high voltage near them. 
Now the power electronic powering the shields probably have their own shields

Stupid gun placement, either you put them on the sides as I read somewhere, or you put them on top and bottom. 
Both the pictures here show stupid placement, why no guns on bottom? And you would want to present the front, then let half the gun bear on the side.

Note that battleship broadsides makes sense, you want your broadside to the enemy in an battleship duel, all your guns can aim and you are hardest to hit. 
The accuracy is far lower for the range than sideways so an broadside makes you harder to hit at long range. 
 

[kunok]

Enjoy the films, games and books and stop trying to make sense of Star Wars physics.

You can't really assume anything, unless is some kind of SW cannon physics handbook (I would buy one), because we don't know how far are the physics different in that universe from the real one. 

Edited November 14, 2016 by kunok
dislexia

[PB666]

 

Alright lets just devolve this discussion into the real world and pull it out of fantasy.

 

Presumbably the chixulub impactor was ovoid or spherical shape, and largely a silico-metalic bolloid that had a density comparable to a planet inner solar system satellite. It was probably an inner solar system object, and based on our observations this appears to fit the risks.

So basically to get the quasi-donut shaped impact crater you need a spheroid object hit land or shallow water, and its going to throw out ejecta many times is size, sort of a scooping effect cause by the inertia of material in the roid compressing and moving outward. The central ring is cause by kinetic melting at the impact and isotatic rebound.

So first we have to deal with tactical issues. You cannot make a crater from a mid air collision, certainly would not have isostatic rebound from the central melting. So chixulub is rougly sherical, is averaged surface area to mass is low, reducing kinetic friction. Presumably the asteroids explode because the heat penetration into the surface causes the rapid expansion of volatile chemicals. But if the impactor is fairly dense with few fissures it would not explode, much, it might on the surface, but there's alot of activity on the surface anyway. So the core of the bolloid survives and smacks the Yucatan, causing any vacationing dinosaurs to suddenly wish they had drank more tequila.

This star killer is what an occupied ship with high axial ratio, is surface area to mass is relatively low.
Now lets say it was a miss, it was headed to mars from say planet x but someone was asleep at the wheel. Ok so its traveling at say 30km/second. shields are not up because the driver is sleeping (prolly had to much tequila).

And so lets just say he had shields are up so lets estimate the kinetic load in those shields. So lets just say we have traveled through 1/10th of the atmosphere at 1000 kg per square meter of air, it has to move out of the way at 10,000s of meters per second. E = 1/2 mv2 and we get billion to trillion joules of energy (lots of heat per meter). Not really dissipating the energy because, alas the ship has traveled from (Space) 80km to 20km in 1 second. So now we have power per surface area, which is now nastily in the gigwatts per squar meter range heading at before impact to the terrawatts per meter.  So lets just say there is not a shield that can survive this. OK so no windows and metal has melted and cavitated, and the interior plastics are no hot gases and the whole thing has immense internal pressure. Boom. and micro impact craters and alot of dead trees and scattered metalic debris.

Ok so our ship comes in nose first, we stave off the explosion for a third of a second or so, but the same thing happens; ships density within a foot of the surface is two low to resist the implosions events followed by over heating and explosion. 

Your star killer would make a nice mid-air kaboom and break lots of windows and leave a modest crater, but the mass and density is nothing near chixulub so . . . .

 

 

 

[_Augustus_]

2 hours ago, Matuchkin said:

Wait, why do the engine nozzles resemble those of jet engines? Would ion engines (or whatever high-efficiency stuff they use) need such nozzles?

Because they have to be used in an atmosphere too.

[StrandedonEarth]

11 hours ago, todofwar said:

I thought it wasn't just the impact of one ship but the fallout from a decent sized battle. Also, they were actively poisoning the planet in order to keep the local population subservient since they were very good assassins.

As I recall, the battle put a pretty good light show in the sky but little else until the ship crashed. And while the Empire did their own subtle contaminating, their decontamination droids were working much slower than they were capable of to keep the Noghri dependent on, and grateful to, the Empire. I got the impression that the Noghri would have been doomed without help. The entire planet's ecology suffered a mass extinction event before the Empire even stepped in.

[wumpus]

3 hours ago, Matuchkin said:

That really reminds me of Ray Bradbury's Frost and Fire.

Wait, why do the engine nozzles resemble those of jet engines? Would ion engines (or whatever high-efficiency stuff they use) need such nozzles? And how do the kilometer wide plumes of million-degree-centigrade exhaust affect the atmosphere/ environment of the planets they are sometimes used in?

For the same reason there are battleship parts all over Star Wars Star Destroyers: they are commercially available such that model builders simply buy off the shelf model kits, take the "good stuff" and cover the model with it.  In the case of cover art, the engines are probably cut and pasted from freely available Air Force promotional pictures (or similarly unencumbered photos).  Even KSP has vacuum and atmospheric nozzles backwards, why would Star Wars get it right?

1 hour ago, PB666 said:

Your star killer would make a nice mid-air kaboom and break lots of windows and leave a modest crater, but the mass and density is nothing near chixulub so . . . .

Except that we can be reasonably certain that there are no planets in the Solar System that can produce Star Destroyers.  So if one popped up near Earth, than obviously it can cross the distances between the stars and is probably traveling at relativistic speeds and probably on the higher end to tradeoff needing "shields" (because all those hydrogen and helium atoms looks like so many nuclear emissions at speed) vs. extra time.  I'd suspect that the relativistic time (or faster if from a fantasy galaxy like Star Wars) will be worse than Chixulub.

I'd also assume that when "shields" fail, that all the stored energy that they absorb gets released rather quickly (unless they already popped the extra energy into mass in the gas tanks or something.  I guess that wouldn't violate too many laws of physics too badly).  It really sounds like something with some nasty failure modes (but a good reason to avoid such modes.  And if you can travel at relativistic speeds, creating matter from absorbed energy doesn't sound that hard).

I still think there's going to be quite a bang.

[adsii1970]

On 11/13/2016 at 6:54 PM, magnemoe said:

As I understand the guns is along the sides, It would be stupid not to let the guns traverse fully forward  
 point it against target and most guns could aim at target while it had an minimal cross section. 
Lots of the combat in Star Wars is based on WW2 combat however the capital ships fight in 3 dimensions. 
 

I would go further back. Episode II reminds me more of broadsides by old sailing ship standards. Think "Pirates if the Caribbean" or "Master and Commander."

[DDE]

2 hours ago, adsii1970 said:

I would go further back. Episode II reminds me more of broadsides by old sailing ship standards. Think "Pirates if the Caribbean" or "Master and Commander."

They had gun ports. Gun ports. Episode VI at least left room for a Battle of Jutland-level distances early in the battle.

7 hours ago, Matuchkin said:

Wait, why do the engine nozzles resemble those of jet engines? Would ion engines (or whatever high-efficiency stuff they use) need such nozzles? And how do the kilometer wide plumes of million-degree-centigrade exhaust affect the atmosphere/ environment of the planets they are sometimes used in?

You are really overthinking it. Some of these "ion" engines have a jet engine spin-up sound.

[Hast5250]

The star destroyer would probably mostly burn up before it impacted the planet, but there would still be considerable damage; IE the destruction of a massive city.