Dyson Spheres

[ÑóẊîöʼn]

Dyson Sphere Faq

A Dyson sphere in the solar system, with a radius of one AU would have a surface area of at least 2.72e17 km^2, around 600 million times the surface area of the Earth. The sun has a energy output of around 4e26 W, of which most would be available to do useful work.

Considering there are around 6 billion people on this tiny little earth with lots of space to spare (Including the ocean floors), This would would mean that trillions of people can live in a Sphere built around the sun.

If a Sphere were to be built around a larger, hotter star, say a blue supergiant, then the distance from the star in the heat would be comfortable would be a lot larger, and hence a larger Dyson Sphere.
This raises the possibilty of people having entire continents to themselves.

Or if a dyson sphere was totally dedicated to production, the output would be massive.

On a more important note, Dyson Spheres are good news for extra-solar colonists:
Because a Sphere is better at retaining heat the closer it is built to the star, this means that relatively cool red dwarf stars (Which are the most common in the galaxy) can have warm, spacious habitats bult around them.
Barring the discovery of FTL travel, it will have to work like this:
The colonist's ship will have to be a giant build-a-Dyson-Sphere kit; when the ship arrives at the destination, the hull and the building materials stored in it will be dismantled and construction will begin.
As well as materials to build the sphere itself, the ship will carry mineral and organic material, to provide the sphere with life and variety.

Building a sphere may increase our chances of contact with another civilisation; they will be quite intrigued as to why a star suddenly (In cosmological terms) winked out into the infra red, and when they take a look at it more closely and discover the cause is artificial, they will eventually send out something to investigate. (Probe Etc.)

Sounds like a good deal; Build a Dyson Sphere and you get more living space and energy, plus easier colonisation and increased chance of contact. Any thoughts?

[SittingBull47]

That would be pretty cool. If there were multiple Dyson Spheres, then you can have seperate planets for different people (by that i mean anarchists, communists, capitalists, Fascists). If that were the case, then we could watch the Fascists destroy themselves, providing a lesson as well. Most likely, were propably years away from even seriously thinking about Dyson Spheres, were still concerned with dust on the moon.

[MiDnIgHtMaRaUdEr]

Sounds like your best idea since the black hole gun.

[Individual]

Would this even be practical in say, 100,000 years? Highly doubtful.

It is a possible improvement/betterment for society. However it is very un-practical. A completely synthetic planet. How exactly would you produce supply of all of the elements? How would you make water and develop and sustain a living atmosphere and climate control?

Don't get me wrong, for this is a decent idea. However it is almost impossible to construct, leaving me to wonder if you are serious.

[Rastafari]

http://www.che-lives.com/forum/index.php?a...ST&f=22&t=19343

similar

[MysticArcher]

"How exactly would you produce supply of all of the elements? How would you make water and develop and sustain a living atmosphere and climate control?"

not sure about creating the organic materials needed, though since you have an effectively unlimited amount of energy (being around a star and all) organic compounds could be easily produced, just like they are made in labs today

as for raw material I imagine either planets that already orbit the star the sphere is built around (probably uninhabited ones with bad environments, where no thing could live) or asteroids could furnish some of the material

the people building the sphere would probably start with parts for a rudimentary sphere, just the metal and solar panels and a small life supported area, brought with them from Earth and from there they'd build more and gather more resources

[MiDnIgHtMaRaUdEr]

A shell built around the sun would not have gravity or an atmosphere. Sounds like nothing more then a glorified space station.

[ÑóẊîöʼn]

A shell built around the sun would not have gravity or an atmosphere.

You're wrong, in two ways; 1. the sphere will rotate, the centrifugal force providing gravity (It can rotate along two planes so that the polar areas get gravity too)
2. The sphere will have suffecient mass to provide it's own gravity (It's huge) The shell will be several hundred kilometres thick, with holes the width of the moon at equidistant points along the shell wall to allow spacecraft in and out.

In Spheres with atmospheres it will have a door on the exterior and the interior surfaces that will close and open alternately to prevent atmosphere loss.
Obviously such huge airlocks will require something special to operate them; massive electromagnets should suffice.

[MiDnIgHtMaRaUdEr]

In order for a shell to have enough gravity to support an atmosphere, the shell would have to be made of solid iron, and be about 20,000 kilometers thick. Centrifical force won't do for an atmosphere. To get an earth gravity from centrifical force at 1 AU would require the shell to be spinning at several million miles per hour, creating the air currents from hell. Also any such sphere would be highly unnecessary. Why not use indepentent free floating space stations instead?

[ÑóẊîöʼn]

In order for a shell to have enough gravity to support an atmosphere, the shell would have to be made of solid iron, and be about 20,000 kilometers thick.

Iron may have the density but it doesn't have the structural strength. A shell made of iron would tear itself apart. I think we may have to invent a new compound, perhaps a tungsten/diamond hybrid.

As for the thickness of the shell, I think it depends on where you were hoping to get your gravity:
From the the shell spinning or the shell's mass. If you want to create gravity by centrifugal force, you could get away with a thinner shell, but if you wanted to attain 'mass-gravity' then you would have to have the shell as thick as the Earth is wide. (I forget the exact number).

Centrifical force won't do for an atmosphere. To get an earth gravity from centrifical force at 1 AU would require the shell to be spinning at several million miles per hour, creating the air currents from hell.

I don't think that the spinning speed will be that high, and neither does it matter, no more than the spinning of the earth affects the currents. With currents of air or water the thing you have to watch out for is how you arrange the continents and oceans. Make a continent too large and the interior will be too hot and dry.
Make the oceans too large and then you'll have supermassive hurricanes and unstoppable tornadoes.
Even a shell with mass-based gravity might have to spin a little to stop it from collapsing into the star.

Also any such sphere would be highly unnecessary. Why not use indepentent free floating space stations instead?

Spheres may be difficult to build but the advantages are clear: Massive amount of space, massive amount of energy gathered from the internal star, more permanent than a space station, better security, nicer to live in if the interior is earth-like, PLUS you can build multiple shells for even MORE space (But an extra shell outside of the original would get no sunlight and would probably be used as a factory floor, and an extra one inside would most likely be a warmer replacement for the original.)

[MiDnIgHtMaRaUdEr]

Why should we build a shell around the sun in the first place? Mohammad does not go to the mountain, the mountain goes to Mohammed! If technology gets to that point that we could build a shell around the sun, then why not just use Jupiter's hydrogen and do the fusion our own damn selves on a mobile space colony? Or if need be, even figure a way to put out the sun and use that hyrdogen?

[Rastafari]

Let's say we set jupiter on fire and have a new rising sun.

[MiDnIgHtMaRaUdEr]

Originally posted by Rastafari@Mar 8 2004, 08:07 PM
Let's say we set jupiter on fire and have a new rising sun.

Eh, you can't just "light" jupiter. In a natural fusion reaction, a celestial body needs to have a hyrdogen core, or at least hydrogen under some considerable pressure. Under that sort of pressure, the hyrdogen fuses to helium, generating large amounts of energy and quite a consererable amount of outward force to prevent the star from collapsing upon itself. The amount of pressure on Jupiter is not sufficient, and even if you could "light" Jupiter, it would blow itself apart.

[Rastafari]

the problem with most of you "holier-than-thou" authoritarian puritanical types is that you can't take a joke.
go to google.com, type in "Arthur C. Clark" + "Sands of Mars," and see what you dredge up, my friend.

[The Red Factor]

Is this all based on the fact that we'll have other planets to mine the amount of material needed to create something that big? This will be a loooooooooooooooooooooooooooooooooooong time away.

[Don't Change Your Name]

Originally posted by The Red Factor@Mar 9 2004, 11:09 AM
Is this all based on the fact that we'll have other planets to mine the amount of material needed to create something that big? This will be a loooooooooooooooooooooooooooooooooooong time away.

Exactly.
Honestly, while the idea is so cool, it is far away in time. At least 1000 years, when this world is full of humans and it is running out of resources and the environment is ruined. And I'm not sure if the technology we have now will help us create such an enrmous thing. So, unfortunately, we won't live to see it. Or so it seems.

Oh, and by the way, it will take a long time to build this, and a lot of investments. So I see this in the future, when capitalism starts collapsing (if it doesn't collapse before that moment) and the earth is ruined. Of course that by that moment there will be a lot of people that will work in this project, but I think this is for the future, so I wouldn't worry that much on this for a while.

[MiDnIgHtMaRaUdEr]

I still say its a pointless project. There is no need for an "earthlike" enviroment anyways. It'll be just like being on the Starship Enterpise, or maybe a Borg Cube... Who knows?

[Snark]

Several problems-

1. Solar wind would be a big, big issue.

2. What about foreign bodies, ie comets and asteroids? If their orbits cross the sphere, you've got a hole a mile across faster than you can think about it.

3. The cumulative heating from all that insolation would need to be shunted to the outside very quickly and efficiently. The shell would have to be an almost perfect conductor.

4. Local gravity would not be high. The shell would not support strong local gravity even if it were an AU across.

5. I sure hope you have a plan for getting several planets' worth of materials to another star.

6. Setting up a sustainable ecosystem would be hard as hell.

[ÑóẊîöʼn]

1. Solar wind would be a big, big issue.

How would it? if we occasionally let some of the (Very ephemeral) hydrogen ions out of the massive airlocks that allow spacecraft through, there'll be no problem.
Also, the interior dimensions would be huge. It may take trillions of years for enough hydrogen ions to build up to noticeable levels.

2. What about foreign bodies, ie comets and asteroids? If their orbits cross the sphere, you've got a hole a mile across faster than you can think about it.

If the shell is thick enough to support an atmosphere, it can easily withstand such impacts.
Also there will be thousands, if not millions, of solar powered engines equidistant along the interior of the sphere to prevent it being knocked out of it's 'orbit'
Spacecraft and other directly controlled entities will use the airlocks.

3. The cumulative heating from all that insolation would need to be shunted to the outside very quickly and efficiently. The shell would have to be an almost perfect conductor.

Look at this:

It should be noted that at 1 AU, the energy flux is around 1.4e3 W/m^2, which calculates as around 395 K, or 122 degrees C if the sphere is a blackbody. This is a bit too hot for an earthlike biosphere (Earth is cooled by its rotation, which effectively halves the energy flux, and its spherical shape, that lowers it further), and a dyson shell need some rather impressive cooling to work.

Emphasis added.

Not only is a type II dyson not a pure black colour, it is also fairly reflective (Clouds, oceans, etc) and therefore the heat would take longer to build up as it bounces around inside the sphere.
Combine that with the probability that the airlocks would be 'leak points' in the otherwise insulatory dyson shell, and I think it might just be cool enough for for a earth-like biosphere.

4. Local gravity would not be high. The shell would not support strong local gravity even if it were an AU across.

Maybe the shell's radius will be 1AU across, but not it's entire diameter. The shell will be thick of necessity, hopefully about 12,000 miles thick, as thick as the earth is wide. That should be enough mass for earthlike gravity.

5. I sure hope you have a plan for getting several planets' worth of materials to another star.

If we find a system that has the appropiate materials, why not use the materials around the star they were found? If we find a red dwarf with a bunch of lifeless bodies orbiting them, why not use the red dwarf? especially as since it's a cooler star we can worry less about heat disspiation problems.

6. Setting up a sustainable ecosystem would be hard as hell.

Why should it be? haven't you heard of the Eden Project? if we can achieve that sort of thing now why shouldn't we be able to build an entire ecosystem in the future?

-NoX

[Snark]

Well, you addressed all my questions- except one. I'm an ecologist....and I can't think of anything that would be more incredibly difficult than building an ecosystem from scratch. Our biosphere is such an incredibly complex emergent system, with so many unknowns and hidden variables, that I have very little faith that we can start up our own, with nothing but human knowledge. Computers might be able to help a bit, but we're talking about a dynamic, organic system of literally unimaginable complexity. Three billion years of trial and error and dynamism can't be replicated by humans. A single miscalculated variable would cripple the system.

Also, just thought of another thing- what about solar flares? A small solar flare would crank out a pulse of radioactivity and heat that could sterilize an entire area of the sphere for the forseeable future. Your red dwarf idea might help this, but a normal star is too volatile for the idea.

Also, do you really think we can engineer a substance with the strength to withstand the tidal forces it would be subject to? We're talking about forces literally beyond the scope of anything we've got experience with.