Is a Death Star physically possible?

[A35K]

Now, assuming we have an unlimited amount of funds and resources, and ways to get them to space, is building a Death Star type station actually physically possible? Will a structure that big collapse under its own gravity? And if it doesn't, unless we have artificial gravity generators, it can't be arranged the way it is in the movies, as gravity would be pulling you towards the walls. What if it spins fast enough to counteract the gravity caused by the mass, would it stay together?

[problemecium]

Sure!

Practical? Obviously not of course.
Presumably if the Empire can create artificial gravity, they can also cancel natural gravity. So despite the Death Star's mass, they can make gravity go any direction they want. As to why they decided to make parallel decks, it's a mystery.
Also, even at 160 km across, since the Death Star's interior is mainly empty space or air (since the rooms themselves are obviously hollow):

...

...its density is much lower than that of a typical asteroid, and even 160 km asteroids made of solid rock have really pathetic gravity. If you stuck a marble on the floor, you might notice a slight tendency to move toward the center of the station, akin to a slightly non-level floor, but it wouldn't be anywhere near enough to cause disorientation.
Regarding structural issues, Star Wars seems to feature a lot of materials much stronger than modern-day metals and alloys. Take for example the star destroyer wreckage seen in the trailers for The Force Awakens - it's basically whole. Even airplanes, at their comparatively low speeds and altitudes, tend to splatter everywhere when they crash, so I'm pretty confident a mile-long spacecraft made out of today's materials would not only explode and scatter across several dozen miles on impact, but break up during reentry and spew debris for hundreds of miles. So if the Death Star is made out of unobtanium, it could easily support its own weight.

Honestly, it's the superlaser that's the hard part. Blasting out enough thermal energy to overcome a planet's immense gravitational binding energy, not to mention making a big dramatic explosion like in the film, is a Herculean task even for an interstellar civilization. Much more practical and equally effective would simply be to burn the surface with the laser or use a kinetic-kill weapon (asteroid launcher anyone?).

[RainDreamer]

The laser probably did something to the planet core, since with that kind of energy it is probably a really powerful laser drill too. Although I don't think it would explode either way.

[Mad Rocket Scientist]

It's possible, but very silly.  Point an spacecraft as heavy as an x-wing towards a planet and go into warp.  The energy released is about 2.517*10¹⁷  kilojules.

[AngelLestat]

Quote

Will a structure that big collapse under its own gravity?

I will answer just this..  

Yeah, I dont see any trouble with physsics. It has the half of the moon diameter, so its volume is many times lower.
Then is all full of air, even if you use steel for each internal wall, you will have lower average density than expanded polystyrene.  This mean that your surface gravity will be 0.01 or less. (I am just stipulating, it does not worth to do the math).

That amount of gravity does not generate any structural problem, even less if you use future materials that are lighter and stronger.

[cubinator]

On 12/23/2015 at 2:01 PM, parameciumkid said:

Much more practical and equally effective would simply be to burn the surface with the laser or use a kinetic-kill weapon (asteroid launcher anyone?).

Or Whack-A-Kerbal.

[cantab]

Structurally it should be manageable. There are irregular asteroids larger than the first death star.

As far as blowing up a planet goes, the superlaser is routinely misanalysed. It's powered by a "hypermatter reactor" that effectively draws fuel from hyperspace, so it doesn't need to carry all its fuel onboard. It's described as variously making "the target's atoms to split into matter/antimatter pairs and annihilate themselves" and "sending part of the target's mass into hyperspace", which in either case means the superlaser is no longer obligated to deliver the entire binding energy of its target. The superlaser is arguably not so much a cannon as a disintegration ray.

The details are all made up technobabble of course, but the principle may be valid in reality. For example suppose you could somehow make all the oxygen in the Earth fuse. That's

0.3 Earth masses / 32 proton masses number of fusion reactions, each releasing about 8-9 MeV, which works out at around 10³⁷ Joules - a hundred thousand times Earth's binding energy.

That's just one hypothetical way. Other stuff would work. Maybe you trigger proton decay. Maybe you can turn matter into antimatter, or even directly into gamma rays or something. The message is that to destroy a planet you don't necessarily need to hit it with its gravitational binding energy, the planet already stores the energy for its own destruction, if you only knew how to release it.

[SomeGuy123]

12 hours ago, cantab said:

 

That's just one hypothetical way. Other stuff would work. Maybe you trigger proton decay. Maybe you can turn matter into antimatter, or even directly into gamma rays or something. The message is that to destroy a planet you don't necessarily need to hit it with its gravitational binding energy, the planet already stores the energy for its own destruction, if you only knew how to release it.

Neat.  And once you are talking about "hypothetical physics", you could posit that whatever magic you are invoking to release the energy stored in ordinary matter only works against the dense central core of a planet.  You cannot make the upper crust or atmosphere explode, whatever you are doing requires a big central mass as a target.

This would explain both why the Death Star has to be this big, and why you don't invest smaller resources to make mere atmosphere burning superweapons.  If the Empire could make weapons that can set the atmosphere of a planet on fire that are 1/100 the size of a death star, they would.

This is true in IRL - you cannot make a hand grenade sized nuclear bomb because of critical mass requirements.  The smallest nuke you can possibly made is pretty heavy, and a slight increase in size means a huge increase in output levels, so it makes economic and practical sense to make your nukes all a certain size, which in turn means you need a jet aircraft or a big missile to deliver them.  No nuclear bullets fired from a handgun.

Edited December 25, 2015 by SomeGuy123

[NuclearNut]

6 hours ago, SomeGuy123 said:

This is true in IRL - you cannot make a hand grenade sized nuclear bomb because of critical mass requirements.  The smallest nuke you can possibly made is pretty heavy, and a slight increase in size means a huge increase in output levels, so it makes economic and practical sense to make your nukes all a certain size, which in turn means you need a jet aircraft or a big missile to deliver them.  No nuclear bullets fired from a handgun.

You dont need a airplane or missile to deliver nukes, just three people with a lot of strength.  Or one if you do not need it delivered onto the enemy themselves / can get their undetected.

https://en.wikipedia.org/wiki/W54

[problemecium]

^ That, plus the option of using a fusion-based nuclear weapon. The minimum requirement for that is simply two hydrogen atoms and enough pressure or kinetic energy to fuse them - in other words, the minimum size is limited only by how small you can make the detonator (although admittedly fusion of a mere two atoms won't be very powerful).

Also, no known planetary atmosphere actually can be "set on fire." Some contain materials which can be combined in exothermic reactions, but in no case do they exist in the proper ratios or conditions to produce a self-sustaining combustion reaction. I'm not assuming you didn't know that, but just in case xD
I guess you could build a device that sustains the reaction energy, e.g. a beam that compresses atmospheric nitrogen and superheats it until it reacts with the oxygen in Earth's atmosphere, and continuously provides that pressure to continue the process, but why even bother when a beam that powerful could just kill everyone by burninating them? ;P

Edited December 26, 2015 by parameciumkid
This editor sucks!

[ChrisSpace]

In any case, it is quite pointless to completely destroy a planet when you could spend much less effort making it's surface uninhabitable.

[Bill Phil]

But why destroy a planet? You just need to subjugate the people. Or, better yet, don't provide them the motivation to hate you. Then subjugation is easier. 

And destroying a habitable planet is stupid. It's already habitable! Don't blow that up.

[SomeGuy123]

16 hours ago, NuclearNut said:

You dont need a airplane or missile to deliver nukes, just three people with a lot of strength.  Or one if you do not need it delivered onto the enemy themselves / can get their undetected.

https://en.wikipedia.org/wiki/W54

That thing isn't economical.  You can make the bomb "just" 5 or 10 times bigger and get 300-500 kilotons instead of less than 1 kiloton (the portable version is that weak)

That's what I mean.  The W-79 is estimated to weigh 700-800 pounds with a yield of 350 kilotons.  If the backpack nuke weighs 100 lbs, that's 8 times the weight for 350 times the yield.  (if it only weighs 50 lbs, it's still a 16 time mass increase for 350 times the yield)

[NuclearNut]

9 hours ago, SomeGuy123 said:

That thing isn't economical.  You can make the bomb "just" 5 or 10 times bigger and get 300-500 kilotons instead of less than 1 kiloton (the portable version is that weak)

That's what I mean.  The W-79 is estimated to weigh 700-800 pounds with a yield of 350 kilotons.  If the backpack nuke weighs 100 lbs, that's 8 times the weight for 350 times the yield.  (if it only weighs 50 lbs, it's still a 16 time mass increase for 350 times the yield)

War is more complex than just maximizing the explosive yield of weapons for material input.  

 

Think of your 5-10 times bigger nuclear bomb, can it be backpacked in and placed on a bridge or what not now?  No, it must now be trucked in, meaning that the enemy can now easily identify the movements of your forces and respond with appropriate amounts of force to neutralize the threat you pose.  This larger bomb also has other problems in itself regarding the yield, larger yields means more stuff gets caught in the blast, necessitating a larger launcher if you are using it in an artillery capacity and making it so that you cannot use nuclear weapons at a range close to your own forces, severely limiting their tactical utility (the W54 in 20 ton TNT yield mode could be used within 2 kilometers of exposed friendly infantry). 

If the world ran on higher yields per kg being the be all and end all of war than we would not have infantry rifles but massive artillery pieces.

[kerbiloid]

And when it rotates - all crew inside its outer layers becomes spots on a wall thanks to centrifugal force.

[PB666]

On December 23, 2015 at 2:01 PM, parameciumkid said:

Sure!

Practical? Obviously not of course.
Presumably if the Empire can create artificial gravity, they can also cancel natural gravity. So despite the Death Star's mass, they can make gravity go any direction they want. As to why they decided to make parallel decks, it's a mystery.
Also, even at 160 km across, since the Death Star's interior is mainly empty space or air (since the rooms themselves are obviously hollow):

...

...its density is much lower than that of a typical asteroid, and even 160 km asteroids made of solid rock have really pathetic gravity. If you stuck a marble on the floor, you might notice a slight tendency to move toward the center of the station, akin to a slightly non-level floor, but it wouldn't be anywhere near enough to cause disorientation.
Regarding structural issues, Star Wars seems to feature a lot of materials much stronger than modern-day metals and alloys. Take for example the star destroyer wreckage seen in the trailers for The Force Awakens - it's basically whole. Even airplanes, at their comparatively low speeds and altitudes, tend to splatter everywhere when they crash, so I'm pretty confident a mile-long spacecraft made out of today's materials would not only explode and scatter across several dozen miles on impact, but break up during reentry and spew debris for hundreds of miles. So if the Death Star is made out of unobtanium, it could easily support its own weight.

Honestly, it's the superlaser that's the hard part. Blasting out enough thermal energy to overcome a planet's immense gravitational binding energy, not to mention making a big dramatic explosion like in the film, is a Herculean task even for an interstellar civilization. Much more practical and equally effective would simply be to burn the surface with the laser or use a kinetic-kill weapon (asteroid launcher anyone?).

Having seen the movie, not only do the structural materials survive insane forces and accelerations, but also the living beings survive being dropped from tie fighters on a ground collision trajectory and survive. Within space they routinely exceed 30g. 

The basic physics for the movie are pretty bad. Then we go to the nuclear physics, in which the entire plasma from a star is store within a smallish device on a planet and then injected into space to then kill other planets. You can convert regular matter into a compressed bosonic matter, but once you do that you cannot readily retrieve it, and it certainly would not be in a form that you can transport it across space in a stream and expect it remain as a cohesive plasma when it arrives, all nuclear fusion will be lost, it would simply be protons and electrons.  These flaws can be added to the flaws of the original movie whose plot it basically copies. 

[A35K]

Apparently, in an episode of Star Wars: The Clone Wars, they crash a star cruiser into a planet at lightspeed and destroy it (the planet. Well, the cruiser as well obviously). Since this show is considered 'canon', the Death Star makes even less sense, as it seems all they had to do to destroy a planet was send a Star Destroyer in hyperspace straight into it. Yes, they will lose an (empty, if they're smart) Star Destroyer, but it takes a huge amount less effort and funds to build a Star Destroyer than 2 Death Stars with ridiculous weaknesses. I'm certain if any real military was presented with a plan like the Death Star, even if they had the technology to do it they would scrap it immediately. Not worth it by any means. 

Edited December 28, 2015 by A35K

[cantab]

Hence, I suppose, the idea that things like the Death Star were meant to control the galaxy by terror. The Imperial Star Destroyer and even the AT-AT have been described as designed on the same philosophy - as important as the actual fighting capability is that the weapon should be an imposing presence that daunts any would-be attackers, and the power of such weapons is meant to intimidate the Empire's subjects into toeing the line.

Of course, it didn't work. The rebellion time and again took out the big Imperial stuff, and in the EU (now summarily rendered non-canon by Disney, mind you) the destruction of Alderaan strengthened the rebel cause.

[Pixel of Life]

On 12/23/2015 at 10:01 PM, parameciumkid said:

Honestly, it's the superlaser that's the hard part. Blasting out enough thermal energy to overcome a planet's immense gravitational binding energy, not to mention making a big dramatic explosion like in the film, is a Herculean task even for an interstellar civilization.

 

Indestructible hairdryer, anyone?

[KerbMav]

On 23.12.2015 at 9:01 PM, parameciumkid said:

Take for example the star destroyer wreckage seen in the trailers for The Force Awakens - it's basically whole. Even airplanes, at their comparatively low speeds and altitudes, tend to splatter everywhere when they crash, so I'm pretty confident a mile-long spacecraft made out of today's materials would not only explode and scatter across several dozen miles on impact, but break up during reentry and spew debris for hundreds of miles.

Someone care to calculate the terminal velocity of a Star Destroyer making a Space Shuttle like reentry and landing?

In the prequel trilogy we see really big ships (Star Destroyer predecessors?) taking of from a planet and going into orbit. The Star Wars universe uses repulsorlift technology to levitate just about anything, so a somewhat controlled crash landing using the rest of available power seems to be possible. (Ignoring the questions about the circumstances why the ship should go down on the planet in the first place.)

[GeneralVeers]

On 12/23/2015 at 0:37 PM, A35K said:

Now, assuming we have an unlimited amount of funds and resources, and ways to get them to space, is building a Death Star type station actually physically possible? Will a structure that big collapse under its own gravity? And if it doesn't, unless we have artificial gravity

Yes, it's physically possible. Whether it's practical is moot because we have unlimited funds and resources. Which presumably includes labor.....

No, it won't collapse under its own gravity because its density is not significantly higher than, say, a real-world skyscraper. A real-world skyscraper can handle one Earth gravity easily, and the natural gravity of a Death Star 160 kilometers across is considerably lower than that. Just for giggles, in order for the Death Star to collapse into a black hole, it would have to be at least three times more massive than our Sun.

And finally, we already know the Death Star (actually both of them) has artificial gravity because in all the movies, when a ship flies into a Death Star landing bay, "up" is clearly visible (by way of viewing the direction people are standing) as being towards the station's "north" pole.

 

On 12/24/2015 at 11:29 AM, RainDreamer said:

The laser probably did something to the planet core, since with that kind of energy it is probably a really powerful laser drill too. Although I don't think it would explode either way.

A simple and efficient way to explode a planet is to simply create internal pressure: burrow through the surface and mantle, and deliver a massive charge of energy to the planet's core. Thermal expansion will then blow the planet apart the same way potatoes explode in the microwave.

 

On 12/26/2015 at 0:22 AM, Bill Phil said:

But why destroy a planet? You just need to subjugate the people.

Your own reaction is the reason. "Why blow up a whole planet?? It's insane!! It's pointless!!!" Such an insane and pointless act leaves people like you gaping in speechless horror. That's how to rule effectively: by demonstrating that you're willing to commit insane and pointless acts of mass slaughter against anybody who decides to screw with you. Do that a few times and NOBODY WILL SCREW WITH YOU.

Edited December 30, 2015 by WedgeAntilles

[KSK]

Assuming that you can find a crew who are ready and willing to repeatedly pull the trigger on entire inhabited planets. Death Star covered this quite well - it was one of the better bits of the EU in my opinion.

[radonek]

Deathstar is complete BS, courtesy of thermodynamics. Every spacecraft need to get rid of waste heat, and that mean either expending coolant or sporting big radiators. Deathstar lacks sufficient cooling equipment and tops it by possesing shape with smallest possible surface. It would melt before even moving, much less fire its silly laser. For detail see http://www.projectrho.com/public_html/rocket/spacewardefense.php#radiators

Face it, whole idea of space combat in Starwars is incredibly stupid, from "fighters" that can't rotate&translate to half-medieval weaponry. Thing with space warfare is that any efficient starship is just as efficient weapon. And if you have lightspeed-capable ships, you don't need giant deathstar to destroy planets.

 

[MarvinKitFox]

On 2015/12/26 at 4:39 AM, parameciumkid said:

Also, no known planetary atmosphere actually can be "set on fire."

True, atmosphere tends to have too low density.

Oceans though.... ripe for the "burning"

 

All you need to do is pump in a bunch of muons.

If you have a sea of "heavy water".. i.e. deuterium replacing a significant part of the hydrogen, then a single muon will trigger several *hundred* D-D fusions before expiring.

But no natural planet has that high a percentage of Deuterium.

 

However, if you put in enough muons, so that you get a significant percentage of H-H collisions where *both* of the H are under the influence of a muon at that time, then you get fusion at dang nearly any temperature. Even down to deeep cryo temperatures!

 

So, simply pump in enough muons into a water ocean to replace 1/1000 of a percent of the electrons in that volume with muons, and the whole thing will fuse.

First the H-H will fuse at room temperature, heating the whole ocean up to the low millions of Kelvin, then at those temperatures you will see muon-catalysed fusion of Carbon, Oxygen, possibly even Nitrogen.

Do this to just a 5km sphere of ocean water, and you have the needed 2e32J explosion to rupture the planet!

 

 

(Ok, so you still need to be able to generate several **kilograms** of Muons, and send them off to your target at high relativistic speeds (needed to keep them fresh, Muons have a short half-life), but that is still very much easier than having to supply the needed  2e32Joules of energy yourself, whether as energy in photons, or 60 billion tons of antimatter, or whatever...)

Edited December 30, 2015 by MarvinKitFox

[GeneralVeers]

3 hours ago, radonek said:

Deathstar is complete BS, courtesy of thermodynamics. Every spacecraft need to get rid of waste heat, and that mean either expending coolant or sporting big radiators. Deathstar lacks sufficient cooling equipment and tops it by possesing shape with smallest possible surface.

Lol. What do you think "thermal exhaust port" means??

At least in part, the Death Star (the first one, anyway) disposes of waste heat by venting hot gas. But aside from the above exhaust port, we really can't assume anything about Death Star cooling systems, because the movies never showed us much of anything.

 

3 hours ago, radonek said:

And if you have lightspeed-capable ships, you don't need giant deathstar to destroy planets.

If you mean the trick where you fly a starship right through a planet at FTL, I'm pretty sure that doesn't work in the Star Wars universe. Aside from the fact that it's one of the first things the Galactic Empire would have tried, Star Wars canon includes the Interdictor class Star Destroyer, which prevents hyperdrives from operating in its vicinity--by projecting an artificial gravity field. Within the field, ships can't jump to hyperdrive and any ship entering the field on hyperdrive will drop to sublight speed. So it's a safe assumption hyperdrive simply doesn't work in close proximity to planets. Fire a missile at a planet at supralight speed, and it drops to sublight before it hits.

Of course, the first movie offhandedly contradicts this theory when Han Solo makes his remark about "without precise calculations, we could fly right through a star". Apparently, whoever wrote up the idea for the Interdictor didn't watch the movies enough times.......

Random side note: why the hell doesn't the spellcheck code for this new editor include "hyperdrive" in its dictionary??? Sheesh.