Dyson Sphere

[Grasshopper27]

Posted this in another thread, but went to so much work I wanted to give it its own thread.

A ring world would be possible within reason, a Dyson Sphere is not reasonable. The amount of matter required to build such a construct would require star harvesting for hundreds of light years in every direction. The shell would need to withstand forces beyond anything even our Sun has to deal with. It would need to be about 40,000 miles thick. Again, the amount of material required to build a shell twice as thick as the Earth is all the way around the Sun is hard to imagine.

There is currently enough matter in the Solar System (not counting our Sun) to build a sphere 10 feet thick. To build one 40,000 miles thick would require matter from 211,200 solor systems (counting their stars). If you have the ability to harvest 211,200 solor systems for matter, then you don't need a Dyson Sphere in the first place.

On the plus side, growing room would not be an issue for awhile. The interior surface area of the Dyson sphere exceeds the total surface area of Earth by a factor of just over half a billion. Since all the surface area would be as close or as far as the builders wanted (mountains or flat lands), all of the space would be habbitable. This means that we would have 2 to 3 billion times more liveable surface area than we do now.

Every man, woman, and child could be instantly given 25 million square miles of land (half the Earth's livable surface area) What you'd actually DO with 25 million square miles of land is another matter.

Grasshopper

 

[Viper GTS]

I'd never heard of it until it was mentioned in a STTNG episode.

Damn cool concept, but nothing I'll see in my lifetime.

(or anyone else's, for that matter)

Viper GTS

 

I'm in

Beware of the dreaded Comet Cursor popup:|

 

[rgwalt]

OK, I'm really going to dork it up here, so get ready...

A ring world is much more practical. First, you can spin it for gravity. With a Dyson's Sphere, we'll have to learn how to manipulate gravity, and then install gravity generators all over the surface. What happens when a generator breaks down? Second, you really don't need 25 million square miles of space. A ring world would still multiply our habitable surface area by a factor of 3 million. Third, a sphere makes space travel a lot more difficult. You have to build a hatch in the side of the sphere for people/spacecraft to enter and leave. You will want to have access to the outside of the sphere for maintance purposes. How do you open a hatch without the air leaking out? More magical gravity generators? With a ring world, you can have space-ports on the ledge. Send your ship tumbling off the ledge at the right time, and it already will have a velocity of 920 miles/sec (the spin speed necessary for gravity), so no need for a launching platform!

A ring world is definitely the way to go.

Ryan

 

[StageLeft]

Be nice if you quacks would post some links so we know wtf you're on!!

 

[Viper GTS]

Originally posted by: Skoorb
Be nice if you quacks would post some links so we know wtf you're on!!

A Dyson Sphere is a huge spherical shell surrounding a star.

Basically the theory is you have a massive living space (the inner surface of the sphere) + virtually unlimited energy.

Viper GTS

 

[conjur]

Loved reading these (Ringworld series) in high school

And would LOVE to see a movie based on those!

 

[Ketteringo]

I vote to move this to highly technical

 

[Atlantean]

Where are you getting this from?? Why would it have to be 40000 miles thick? the earth is only like 8800 miles thick and it seems to withstand the suns forces just fine... what was the original thread?

 

[FenrisUlf]

Gravity. You need mass to provide gravity. You couldn't spin a Dyson Sphere or the gravity over it's surface would be irregular, tapering to zero at the poles, making a large chunk of your surface unlivable. Plus the angular velocity of spin would require incredibly strong materials to withstand the centripital force. So you would need lots of mass to provide gravitational force. A bigger problem with the Dyson sphere is providing day/night cycles. And getting rid of excess heat - if all of a star's energy is being dumped into the inside of the sphere, it's going to heat up. The earth has only half its surface area exposed to the sun at once and half exposed to space to radiate excess heat. The only way to get rid of the heat in a Dyson sphere is to transfer it to the outside of the sphere as fast as the sun is producing it. All the dirt and structure would make pretty good insualtion, making heat transfer difficult. Plus you need to protect against comets and rogue interstellar debris from poking holes in your sphere. I think a Ringworld would be a better idea. At least somewhat more feasable. Read Larry Niven's "Ringworld" for some good technical info (don't forget to read the postscript info on the science and engineering research he had to do on the design).

 

[Atlantean]

I have read ringworld... It was quite a good book, and I read the other ringworld books as well (there was three of them wasn't there?). Larry Niven came up with some interesting ideas in those books. The idea of a ringworld is an interesting one, but how would you stabalize a ring that size (realisitically)? It would take an aweful lot of power to stabalize a ring the size of the one in ringworld, but I believe that you are right about it being more feasible than a dyson sphere.

 

[MaxDepth]

Originally posted by: Skoorb
Be nice if you quacks would post some links so we know wtf you're on!!

the "stuff"

 

[silverpig]

Originally posted by: grasshopper26
Posted this in another thread, but went to so much work I wanted to give it its own thread.

A ring world would be possible within reason, a Dyson Sphere is not reasonable. The amount of matter required to build such a construct would require star harvesting for hundreds of light years in every direction. The shell would need to withstand forces beyond anything even our Sun has to deal with. It would need to be about 40,000 miles thick. Again, the amount of material required to build a shell twice as thick as the Earth is all the way around the Sun is hard to imagine.

There is currently enough matter in the Solar System (not counting our Sun) to build a sphere 10 feet thick. To build one 40,000 miles thick would require matter from 211,200 solor systems (counting their stars). If you have the ability to harvest 211,200 solor systems for matter, then you don't need a Dyson Sphere in the first place.

On the plus side, growing room would not be an issue for awhile. The interior surface area of the Dyson sphere exceeds the total surface area of Earth by a factor of just over half a billion. Since all the surface area would be as close or as far as the builders wanted (mountains or flat lands), all of the space would be habbitable. This means that we would have 2 to 3 billion times more liveable surface area than we do now.

Every man, woman, and child could be instantly given 25 million square miles of land (half the Earth's livable surface area) What you'd actually DO with 25 million square miles of land is another matter.

Grasshopper

40 000 miles of solid material doesn't provide enough gravity for you?

I'd think the gravity would be so intense it'd crush you.

 

[Grasshopper27]

Originally posted by: rgwalt
OK, I'm really going to dork it up here, so get ready...

This IS ATOT you know...

A ring world is much more practical. First, you can spin it for gravity. With a Dyson's Sphere, we'll have to learn how to manipulate gravity, and then install gravity generators all over the surface. What happens when a generator breaks down?

Gravity generators are a given. If you can built a Dyson Sphere, you already have the ability to alter gravity. You'll need it to collect those 210,000 solor systems worth of matter to build the damm thing.

When a gravity generator breaks down, the backups turn on. If you can build something of this size, you should be able to have a lot of backup systems.

Besides, if we're talking sci-fi here, the anti-gravity generators on the Enterprise do not just shut down if they fail, they spin down and provide 10 to 15 minutes of gravity without power.

You can of course just turn them off and kill gravity right away, but if they fail, it takes time for the effect to fade.

Imagine an ocean of water the size of 30 planet Earths slowly lifting off the interior surface of such a sphere if the gravity really did fail! Then imagine when it got turned back on!

Second, you really don't need 25 million square miles of space. A ring world would still multiply our habitable surface area by a factor of 3 million.

Correct, a ring makes about a billion times more sense. It provides plenty of surface area, can be rotated, could be built using more pratical levels of technology, and still solves the space problem.

Third, a sphere makes space travel a lot more difficult. You have to build a hatch in the side of the sphere for people/spacecraft to enter and leave. You will want to have access to the outside of the sphere for maintance purposes. How do you open a hatch without the air leaking out?

Did you never see "Relics" in TNG? You have energy shields that hold back the air/water/land around the access portals, and of course access portals are simple to build if you can already construct a Dyson Sphere.

That is one point that is often missed. The technologies required to built it also allow it to function. For example, it will need massive station keeping thrusters to make sure it doesn't drift off alignment with the sun.

With a ring world, you can have space-ports on the ledge.

How do you keep the air/water/land from falling off the ledge?

Send your ship tumbling off the ledge at the right time, and it already will have a velocity of 920 miles/sec (the spin speed necessary for gravity), so no need for a launching platform!

You're again missing the point. If you have the ability to construct a ring world, you are not concerned with such things. You have star drives with FTL ability, high speed sub light travel for use within star systems, etc.

Grasshopper

 

[Analog]

STNG, the enterprises entered it and got stuck.

 

[rgwalt]

Ah, but with a ring world, you don't need FTL drive. You can use the materials already in the solar system to construct it. You can build walls 1000 miles high on either edge to keep the air from spilling out, too.

Here is another point... how do you generate a day/night cycle in a dyson's sphere? With the ring world, you can rotate a ring of squares that are cabled together around the sun, maybe in the region of mercury's orbit. These squares will cast shadows on the ring world, and create the day/night cycle.

Ryan

 

[Kadarin]

Originally posted by: yellowfiero
STNG, the enterprises entered it and got stuck.

That episode sadly ignored the possibilities of exploring plotlines having to do with the sphere itself to focus on the issue with Scotty. The fact that they were in a Dyson Sphere was almost irrelevent. Read the novels Orbitsville and Orbitsville Departure by Bob Shaw for a much better treatment of Dyson Spheres.

 

[Grasshopper27]

Originally posted by: Atlantean
Where are you getting this from?? Why would it have to be 40000 miles thick? the earth is only like 8800 miles thick and it seems to withstand the suns forces just fine... what was the original thread?

The Earth is 26,000 miles thick actually.

The reason it has to be 40,000 miles thick? Support and mass. It has to be of a certain size and mass to withstand the forces placed against it, and this is assuming it is made out of some super strong material.

You have to understand the scale of this, it makes a planet look puny by comparison.

What is a Dyson Sphere? & FAQ

Look at section 8: How strong does a rigid Dyson shell need to be?

Very strong. According to Frank Palmer:

Any sphere about a gravitating body can be analysed into two hemispheres joined at a seam. The contribution of a small section To the force on the seam is g(ravity)*d(ensity)*t(hickness)*A(rea)*cos(angle).

The integral of A*cos(angle) is (pi)*R^2.

So the total force is g*d*t*(pi)*R^2. Which is independent of distance, neatly enough.

The area resisting the force is 2*(pi)*R*t.

Thus, the pressure is g*d*R/2; this can be translated into a cylindrical tower of a given height on Earth. If that tower built of that material can stand, then the compression strain is not too great.

At 1 AU, that comes to 2*([pi]*AU/YR)^2, or -- by my calculations -- in the neighborhood of 80 to 90 THOUSAND kilometers high.

The tendncy to buckle, moreover, is another problem.

That is where I got the 40,000 mile figure (80 to 90 thousand kilometers)

The force of the sun has nothing to do with it. The forces required for station keeping thrusters, the forces placed on it as it drifts through the Galaxy, and the forces placed on it due to its physical size in space all have an effect.

Grasshopper

 

[JeffreyLebowski]

well instead of a force field to hold in the atmosphere, which would be risky cause a power loss would be catostrophic. The ring would have walls, say 100 miles high, and the "roof" would be made of a clear material that can be "tinted". And the "tint" would rotate around the ring.

 

[Grasshopper27]

Originally posted by: FenrisUlf
Gravity. You need mass to provide gravity.

True, but you wouldn't spin a Dyson Sphere, you'd need artifical gravity generators. Any specices advanced enough to build a Dyson Sphere is advanced enough to have artifical gravity.

You couldn't spin a Dyson Sphere

You couldn't spin it because it would rip itself to shreds, almost no matter what you built it out of. The forces placed on it would be hard to imagine.

A bigger problem with the Dyson sphere is providing day/night cycles.

This is solved by the internal shields which can be turned clear or opaque (they would be placed in the "sky" between the surface and the sun). Again, if you can build this, you have shield technology.

And getting rid of excess heat - if all of a star's energy is being dumped into the inside of the sphere, it's going to heat up.

Again, shields would do most of the work here. In addition, you could simply have raidators on the outside of the sphere and collectors on the inside, pipe the heat through and out into space, no big deal to anyone who can build this.

Plus you need to protect against comets and rogue interstellar debris from poking holes in your sphere.

Again, if you can build this, you have long since developed shield technology.

You're right however, a ring world makes a million times more sense.

Grasshopper

 

[Grasshopper27]

Originally posted by: silverpig
40 000 miles of solid material doesn't provide enough gravity for you?

I'd think the gravity would be so intense it'd crush you.

It might, but it might not. The Earth is 26,000 miles thick, but it is moving through space at a high rate of speed and spinning. The Dyson Sphere would be stationary.

That would affect it, somehow.

Grasshopper

 

[Grasshopper27]

Originally posted by: rgwalt
Ah, but with a ring world, you don't need FTL drive. You can use the materials already in the solar system to construct it. You can build walls 1000 miles high on either edge to keep the air from spilling out, too.

Building a ringworld without FTL drive would be difficult. You could use the existing planets, but you'd need so much power to do it, that you'll have solved the FTL drive issue in the process.

It is hard to imagine just how much energy would be required to "harvest" Jupiter for raw materials... It would probably take less energy to make a faster than light trip to a near by star.

Grasshopper

 

[Grasshopper27]

Originally posted by: Astaroth33

Originally posted by: yellowfiero
STNG, the enterprises entered it and got stuck.

That episode sadly ignored the possibilities of exploring plotlines having to do with the sphere itself to focus on the issue with Scotty. The fact that they were in a Dyson Sphere was almost irrelevent. Read the novels Orbitsville and Orbitsville Departure by Bob Shaw for a much better treatment of Dyson Spheres.

ROTFL! So true!!!

Who bloody cares about Scotty, you're in a DYSON SPHERE!!!!

Grasshopper

 

[Kadarin]

Originally posted by: grasshopper26
The Earth is 26,000 miles thick actually.

Er, no.

According to NASA, the diameter of the Earth is as follows: 12756 Kilometers = 7,926.210928 Miles

The circumference of the Earth at the equator is approximately 25,000 miles.

 

[rgwalt]

With all this new technology you are assuming that a species will have, you might as well assume they have a "conjuring" device that can make a dyson's sphere out of a banana peel and a bear can. *poof*

Ryan