Dyson Spheres & Rings - Better Alternatives Exist?

[Whipley Snidelash]

I seriously doubt that any of these things exist. For one thing there’s something better. Assuming the civilization has the technology to build a Dyson sphere or ring, would they? With that technology and resources it seems to me it would be much simpler to strip the rocky parts of a large planet, cool the iron core and build inside of that. Or there are probably some already stripped and cooled iron cores roaming around in the universe find one and take it over. No need for super materials or structures or searching for raw material.

 

[Bandersnatch]

Building inside a planet you're not able to better utilise the source of energy (sunlight) and you're gaining only modest build area (much less than just building on the surface). The rings and spheres are (conceptually) advantageous, because you can get the most area to build on from the least building material, while maximising the collection of the available solar energy.

 

[Whipley Snidelash]

They could leave a remnant of the iron core molten for power, not that the civilization capable of doing this would have a problem with power. Area would be many times the area of a planet. They would first be living inside this thing. What’s the area of an onion when you count all the layers? And you would have many many more layers in an iron core the size of ours and ours is nowheres near probably the biggest ones available. What’s more excavating the iron core for living space would provide an incredible amount of metal to build out from the surface as well. Don’t forget I am assuming a technological civilization that could’ve created a Dyson sphere or ring. It just doesn’t require inventing some kind of incredible superstrong metal like in Ringworld. It also doesn’t require propulsion like a ring or sphere would. I would appreciate it if no one steals this idea as I am currently writing a story incorporating it.

 

[Bandersnatch]

There are issues with it, though. You still need super strong materials to prevent the outer layers from collapsing onto the inner ones - at 300+ GPa pressures you can't just rely on iron in the core to hold the ceiling. You have to deal with gravity decreasing to zero towards the centre, as well as overall decrease as you remove the excavated material. You need a way to efficiently remove waste heat from the inner layers. You need to keep the layers separated by airlocks to keep normal air pressure.
And - as was mentioned - you lose the benefit of capturing more solar energy. I think the general zeitgeist in the S-F writing is that available energy will be the sole limiting factor for very advanced civilisations, so it would make sense for them to want to build a Dyson sphere at some point. With building inward you'll need to come up with alternative energy sources (but again, more energy usage is more waste heat to remove), or otherwise justify why they don't need all that much energy.

 

[Whipley Snidelash]

Where did you get that pressure from? Unless that’s enough to liquefy iron or make it ductile I don’t see a structural problem considering you have virtually unlimited thicknesses of iron to leave for structural integrity. Some of these questions should be easily handled by an advanced technology capable of doing this project. You have to assume the same technology that could create a Dyson ring or Dyson sphere. I probably should’ve said sooner but this whole idea is based on the technological capabilities of the ringworld engineers in Niven’s Ringworld book.

Is it possible for a planet to have a steel core?

 

[Bandersnatch]

Where did you get that pressure from?

Pressure in the core, from Wikipedia. It'd be less once you started to remove material, but that's what you have to deal with initially.

 

[DrStupid]

Assuming the civilization has the technology to build a Dyson sphere or ring, would they? With that technology and resources it seems to me it would be much simpler to strip the rocky parts of a large planet, cool the iron core and build inside of that.

Of course that would be much simpler. It would also be much simpler to build a small house with a garden than a giant pyramid. But guess what the ancient Egyptians and Mayas did. They built giant pyramids - independent from each other! It would have also been much simpler to go to the beach than to the Moon. However, America went to the Moon – not because it was easy but because it was hard.

You have to assume the same technology that could create a Dyson ring or Dyson sphere.

The technology that could create a Dyson sphere depends on the design. There are very different types of Dyson spheres with very different technical requirements. Some of them could be made of currently known materials (e.g. Dyson swarms or maybe even Dyson bubbles).

 

[BWV]

Given that the construction technology would be some sort of self-replicating autonomous robotic machinery, building planetoids and building on the surface is easier than tunneling, as solar energy to power the operation is always available. Why dig large underground systems when you can just smash a few asteroids together to create a planetoid and build on the surface?

 

[stefan r]

They could leave a remnant of the iron core molten for power, not that the civilization capable of doing this would have a problem with power. ...

They would have problems with power. You have to radiate heat or it gets to hot to live there. They could use orbital rings in order to support radiator structures.

Doing useful work requires moving heat into a cold sink. Because we live in an atmosphere we usually ignore this. We say our car runs on a mix of air and gasoline. People don't say the car engine runs by exhausting steam, carbon dioxide, and nitrogen. Power plants have cooling towers.

If you ram a potato into someone's tail pipe the engine won't work. Supposedly this won't do any damage to the vehicle. Eventually the potato dries out and shrivels. When they try to start the car the potato pops out. They won't know what happened. I have not tested this.

... I would appreciate it if no one steals this idea as I am currently writing a story incorporating it.

 

[member 656954]

I seriously doubt that any of these things exist.

I do too, but for reasons that have nothing to do with engineering. Even though I invoke aliens in my stories, it doesn't mean I expect the universe is festooned with intelligence blithely building megastructures.

But I do applaud colonization on the inside of planets. I used a similar technique in Tyranny, on a smaller scale, to be fair, it's made by humans after all, but the concept does have some narrative advantages. Also, I could ignore most of the technical issues raised in this thread because...made by humans, small scale, science fiction