Megastructures - what would it take?

[Xyph]

Dyson shells, ringworlds, orbitals, and the like - obviously these structures would all require materials of incredible tensile strength (less so with orbitals, perhaps), close to the strong nuclear force, etc., but could such a material ever be made? Nanotech seems to be coming up with materials with tensile strengths far above naturally occuring materials, so what are the chances something could be created with a strength close to that required by megastructures?

[mezarashi]

I think we may be a long way from using our nanotechnology for that. It *is* nanotechnology. These structures would be in kilometers if not millions of kilometers. I think what is preventing us from building such structures is the logical usefulness of these structures as well as the economics rather than our incompetence in materials engineering. We can make plenty of strong steel/carbon alloys. Even if we could build it using silicon oxide (the most common element on the Earth's crust), the sheer size of these structures means that we'll have to probably borrow material from other planets. The transportation costs would not be justifiable.

 

The carbon chains we have been creating are nonetheless amazing. The intermolecular forces can be very very strong. All we need is just the correct arangement. Diamond is just carbon after all isn't it?

[[Tycho?]]

Things with more strength would be required for what he's talking about. Larry Nivens Ringworld is a structure that loops around a star and has a radius of 1 AU, it rotates to give artificial gravity to the surface. Someone calculated how strong the material would need to be, and it is indeed on the same order of magnitude of the strong nuclear force.

 

I dont think "nanotechnology" as it is currently understood would be sufficient for something like that. That would require manipulation on not just an atomic scale, but the sub-atomic scale of protons and neutrons. I dont think anybody would even know how to approach such a problem.

[calbiterol]

Not to be nit-picky or anything, but silicon oxide isn't an element. The most common element in the earth's crust, by the way, is oxygen, IIRC.

[bascule]

The most common element in the earth's crust, by the way, is oxygen, IIRC.

 

According to this you're right:

 

http://www.windows.ucar.edu/tour/link=/earth/geology/crust_elements.html

 

The 8 most common elements in Earth’s crust:

46.6% Oxygen (O)

27.7% Silica (Si)

8.1% Aluminum (Al)

5.0% Iron (Fe)

3.6% Calcium (Ca)

2.8% Sodium (Na)

2.6% Potassium (K)

2.1% Magnesium (Mg)

[MIG]

EROR

[Ophiolite]

Let's just start with a skyhook.

[arkain101]

nm my post

[marklar]

Having a ringworld with gravity would require huge material strength and having gravity in a dyson sphere would not be possible accross it's whole surface, so let's forget about gravity.

 

If the structure is in a zero gravity orbit it doesn't have to be strong, in fact it doesn't even have to be held together as long as it is extremely accurately placed (thrusters would probably be handy).

 

If gravity is your thing, then you would need a long string of rings rotating with the orbital path as their axis (kinda like a candy necklace). The string of this necklace would be a guide and have no force exerted on it.

 

Anyway, a sufficiently large ring made of thousands of planets (finding a way to empty out a couple of black holes would help) could have a crust thickness similar to the diameter of the Earth meaning it would have it's own natural gravity without having to simulate it artificially.

[Pleiades]

Ok, let’s say we build a Dyson sphere at 1 AU, that’s nice because that’s where the earth is. At that distance, if we used all the matter in the solar system (excluding the sun) we’d only be able to make it 28 feet thick. In fact, we wouldn’t even be able to make it 28 feet because I calculated all this using the volume of all the planets, not their densities.

 

There is however enough matter to make a ringworld of reasonable size.