Building a Dyson Sphere around a Class-B Star

[Khatti]

I was idly thinking of Dyson Spheres and solar energy when this idea came to me: say you were technologically advanced enough to build a perfect, Dyson sphere and were able to deal with the problems of drift--in other words you belong to a really, technologically advanced civilization! It occurs to me that you would probably build something like this around a Class-B or Class-A star because you could build another smaller, globular structure around the Class-B star that could shield the inhabitants from really dangerous emissions from the star--and the globular shield could use such higher energy emissions to produce energy and possibly even exotic matter. You would need the globular shield anyway to give the inhabitants the semblance of day and night, why not use it for production as well?

Because of the level of assumed technological ability of builders what I'm about to ask may be a ridiculous question--but I'm going ask anyway: What would be the advantages and disadvantages of building such a structure around a Class-B or Class-A star?

 

[Noisy Rhysling]

If they're that advanced why would they need such a clumsy energy source?

 

[Khatti]

If they're that advanced why would they need such a clumsy energy source?

A perfectly legitimate question. It may be the difference between making precious gems and being able to dig them out of the ground. Digging is always likely to be a bit cheaper. I admit this is a bit of idle speculation that caught my fancy. I should take this time to apologize to Ryan and Evo for not posting this in the writing section, but I don't have any story ideas attached to this. I'm just intrigued and I thought I would toss it out there. But you're right, a civilization advanced enough to do this might very well be advanced enough to not bother doing this.

 

[Noisy Rhysling]

They make diamonds in the lab now. Just sayin'.

But let's say that they didn't build this, it was a gift from a more advanced race. It fits their technological level so it's reasonable to have it. How's that?

 

[Khatti]

But let's say that they didn't build this, it was a gift from a more advanced race. It fits their technological level so it's reasonable to have it. How's that?

The thing to remember about a Dyson Sphere is no matter how power is used or made there is still a lot of desirable real estate to be had. That would probably be the main selling point to any race. Those advanced aliens may not be in such a hurry to give the real estate to someone else.

 

[Noisy Rhysling]

The thing to remember about a Dyson Sphere is no matter how power is used or made there is still a lot of desirable real estate to be had. That would probably be the main selling point to any race. Those advanced aliens may not be in such a hurry to give the real estate to someone else.

Suppose they built a bunch of robotic engineers to do this kind of thing. Just set the robots loose as they evolved into something that didn't need an instrumentality. Would that fly?

 

[Khatti]

Suppose they built a bunch of robotic engineers to do this kind of thing. Just set the robots loose as they evolved into something that didn't need an instrumentality. Would that fly?

I wonder if we're talking past each other. I'm interested in how viable it would be to build a Dyson Sphere around something really big, hot, and volatile. While how it got built, and by who, are interesting questions to consider they aren't on my mind right now.

 

[Grinkle]

I read Ringworld years ago, I am not at all versed in whatever are thought to be the main design considerations of a Dyson sphere, so this may be very naive.

My perspective is to consider the surface temperature desired and the diameter required to get that temperature vs the energy output of the star and how much material is available to create a sphere of that diameter and how to vent extra energy out the back of the sphere if needed to maintain temp if things get too warm and how long the star will produce the needed energy to maintain the desired temperature and then you know if the star you are considering is suitable.

 

[Noisy Rhysling]

The thing to remember about a Dyson Sphere is no matter how power is used or made there is still a lot of desirable real estate to be had. That would probably be the main selling point to any race. Those advanced aliens may not be in such a hurry to give the real estate to someone else.

I was addressing this:

"Those advanced aliens may not be in such a hurry to give the real estate to someone else."

 

[Khatti]

I was addressing this

Oh I see what you mean. One thing to remember about those aliens is they would build a DS to their specs, not ours. They might like more or less gravity, They could have a different, not quite compatible, recipe for an atmosphere. Given the thing I'm most concerned about in this scenario, they might be able to take a little more hard radiation than we can. All these things would have to be considered before we move in.

But what immediately intrigues me is whether or not those uber-aliens would find the idea of building a DS around a Class-B star, which coughs up a lot more radiation in the ultra-violet to X-ray spectrum than Sol does, attractive. They idea I have is that they could use the higher energy output to create more energy for themselves. the downside is that the unfiltered output of a Class-B star would put you in the Cancer Ward and cook the atmosphere into something un-breathable. So you have to put some sort of filter/shield between the star and the ground. I thought I had was that the shield/filter would be the logical place to turn that hard radiation into something useful.

I read Ringworld years ago, I am not at all versed in whatever are thought to be the main design considerations of a Dyson sphere, so this may be very naive.

If I were any less naive than you are I wouldn't have submitted this thing. They whole point of asking this question is to see how naive I am. If you read the paperback version of Ringworld circa 1975 you should remember the artist's depiction of the ringworld: a large band surrounding a sun with a smaller band sitting between the sun and the ringworld. The smaller band had shaded patches, and was designed to mimic the shifts of day and night. The shield/filter I'm talking about would be that smaller band. However, in my scenario, that band would be another sphere--and it would have an additional task: filtering out and utilizing the higher frequency radiation that a class-B star to kick out. Those uber-aliens would not have evolved in a star system with a class-B star because nothing has time to evolve in a star system with a class-B star. The star will go nova long before anything more complicated than an amoeba has time to get going. Also, my assumption is that the levels of radiation a class-B would put out would be hell on any of its satellites.

However our uber-aliens, with the amazingly high level of technology, might look at a class-B star and think: If we're smart we should be able to harness all that power for a few million years." After a few million years our uber-aliens are going to have to be elsewhere when the class-B goes nova. But anyone who has the know-how to build a Dyson Sphere has the know-how to be elsewhere when the house goes up.

The beauty of a Dyson Sphere to Freeman Dyson was that it would utilize all the energy of a star. the beauty of our uber-aliens system is that they utilize the energy of their Class-B star twice: once in the filter which deals with the more energetic and dangerous forms of radiation, and once with the lower forms of radiation that has been put through the filter. This lower form of radiation would be akin to the energy output of Sol: of the spectrum and intensity that created life on Earth. The lower intensity radiation would fall on all that real estate beyond the filter and be used to produce food and energy of the sort we would utilize solar cells to harvest.

It's a wonderful scenario--assuming I haven't screwed up anything. That's why I'm laying this all out for you really smart people; so you can tell me where I screwed up!

 

[Noisy Rhysling]

Now I want to write The Spheres of Infinity.

Or maybe not. Too many book unfinished already.

 

[Khatti]

Now I want to write The Spheres of Infinity.

Or maybe not. Too many book unfinished already.

I hear you Brother.

 

[Grinkle]

If we're smart we should be able to harness all that power for a few million years."

Here's a slight twist. Conceive a sphere that is not intended to support life, but instead intended to step-down the energy-density gradient (or thermal gradient maybe) of the high energy star to something directly useable by myriad less-robust equipment. The inside of the sphere contains the energy of the star, the outside of the sphere has tap points for other equipment to connect to, and these tap points provide (for example) a 1000C temp surface that can be used to drive a steam engine, if one wants to envision a steam-age society that was gifted with a long-lived battery. Or it provides some more advanced energy tap point that a star-faring craft could use to re-fuel. Like gas stations.

 

[Noisy Rhysling]

Gonna need some way to keep them on the outside of the sphere?

 

[Grinkle]

In the steam punk scenario? Domes, maybe, if the sphere is spinning. They live on the "top" of the dome, and their "sun" is a hotspot on the surface of the Dyson sphere.

 

[Noisy Rhysling]

In the steam punk scenario? Domes, maybe, if the sphere is spinning. They live on the "top" of the dome, and their "sun" is a hotspot on the surface of the Dyson sphere.

Or a Ringworld "bolted" to the outside?

 

[Grinkle]

Formed to look like a steam locomotive from afar ... ;-)

 

[Noisy Rhysling]

Formed to look like a steam locomotive from afar ... ;-)

That would look LOCOmotive.

 

[Khatti]

Here's a slight twist. Conceive a sphere that is not intended to support life, but instead intended to step-down the energy-density gradient (or thermal gradient maybe) of the high energy star to something directly useable by myriad less-robust equipment. The inside of the sphere contains the energy of the star, the outside of the sphere has tap points for other equipment to connect to, and these tap points provide (for example) a 1000C temp surface that can be used to drive a steam engine, if one wants to envision a steam-age society that was gifted with a long-lived battery. Or it provides some more advanced energy tap point that a star-faring craft could use to re-fuel. Like gas stations.

I would be interested in reading that story.

Dyson Spheres are like Black Holes. Everyone can write a story about them, and every story will be different. If anything each story will be more different. No one builds Black Holes.

 

[Noisy Rhysling]

I would be interested in reading that story.

Dyson Spheres are like Black Holes. Everyone can write a story about them, and every story will be different. If anything each story will be more different. No one builds Black Holes.

Never been to Calcutta?

 

[Khatti]

Never been to Calcutta?

Well okay...there is one exception.

 

[DrStupid]

What would be the advantages and disadvantages of building such a structure around a Class-B or Class-A star?

Noisy Rhysling already addressed the main issue in his first reply: The technological requirements for Dyson Spheres would make them obsolete. But there are still motivations to build such a structure, e.g. as a message for everybody else: WE HAVE BALLS!

 

[Noisy Rhysling]

Noisy Rhysling already addressed the main issue in his first reply: The technological requirements for Dyson Spheres would make them obsolete. But there are still motivations to build such a structure, e.g. as a message for everybody else: WE HAVE BALLS!

Now I'm see a celestial hamster rolling around the galaxy.

Thanks, that's cheaper than ... Um, never mind.

 

[Khatti]

Noisy Rhysling already addressed the main issue in his first reply: The technological requirements for Dyson Spheres would make them obsolete. But there are still motivations to build such a structure, e.g. as a message for everybody else: WE HAVE BALLS!

That might be a better reason than all the practical ones.

 

[Noisy Rhysling]

That might be a better reason than all the practical ones.

Super science doesn't mean super savoir faire.

 

[Khatti]

Super science doesn't mean super savoir faire.

If you came up with the super science you might want to pat yourself on the back for being such a good boy!

And I keep coming back to the idea that might use a star in this way just because it's there anyway. I wonder if people living in small towns in New England ever look at the ruins of the floor mill sitting by the local stream or river and think: "You know we could put up another water wheel, but connect it to an electric generator this time!" And, while the stream may freeze up in the winter, while the wind-turbines do not turn on a still day, while the solar panels don't work so well in the dark, a star in a Dyson Sphere will reliably give you power until it goes nova. And there is still the question of real estate; where, and under what conditions, are people going to live? I often think that, if we leave the solar system and travel to other systems with habitable planets, we may build Bishop's Rings and McKendree Cylinders to live in and forgo the habitable planet. By the time we reach those far star systems we may simply be more comfortable living in a man-made environment than on a planet--where things can fall out of the sky and there's nothing but the atmosphere standing between you and it! Who in their right-mind would want to live that way?!

 

[Noisy Rhysling]

Just seems like a whole lotta work to support a population.

 

[Khatti]

Just seems like a whole lotta work to support a population.

Yeah it would be, but this sort of thing is relative. building the Pyramids, or the city of Athens, or Versailles, was a lot of work, but they did it anyway.

 

[Noisy Rhysling]

Yeah it would be, but this sort of thing is relative. building the Pyramids, or the city of Athens, or Versailles, was a lot of work, but they did it anyway.

Piling rock and stone ain't in this league. Or am I behind the curve on the technology?

 

[Khatti]

Piling rock and stone ain't in this league. Or am I behind the curve on the technology?

True enough. Have to go on family trip, will get back to you.

 

[Noisy Rhysling]

True enough. Have to go on family trip, will get back to you.

Check the orbits before you go, Rich Purnell might have a better trajectory for your trip.

 

[stefan r]

Red giants (AGB stars) have some advantages over B stars. Total luminosity is over 1000X the sun. The lower gravity makes it easy to move the Dyson sphere (swarm) around with solar sails. The red giant's solar wind would have "metals" available for more swarm construction and hydrogen for fusion. Red giants with solar mass do not become super novas.

A binary star gives you some gravity assisted options. Long tethers and orbital rings could add something like a steam punk look.