Re: [Spaceships] Nanocomposite and structural materials
 

Okay. Fine.

Re: [Spaceships] Nanocomposite and structural materials
 

I would note that Spaceships doesn't actually say that armor and structure are made of the same stuff, and in fact they probably aren't. However, given the general theme of UT, I would assume nanocomposite is a composite material that is at least partially carbon nanotubes, and since we have canonical references to space elevators, I'd assume fibers on the optimistic end of what can be done with carbon nanotubes (say, density 1.6g/cc, tensile strength 60 GPa) are available.

Re: [Spaceships] Nanocomposite and structural materials
 

Right. I’m asking about the structural materials that are consistent with a technological base that uses nanocomposite etc. as armour. The density and tensile strength of nanocomposite etc. themselves would be worst case values.

I already have carbon nanotubes and a guesstimate for carbon nanotube FRP in my spreadsheet, but they are awfully good. Pure oriented buckytubes would be better than diamond, which I’d worry about because diamondoid is listed as a TL11 material. Buckytube FRP at TL10 also seems like a huge jump from aramid FRP at TL9.

Re: [Spaceships] Nanocomposite and structural materials
 

Depending on what 'better' you're talking about, that might or might not be true. On a nano scale single-walled carbon nanotubes have the highest ratio of tensile strength to weight of any conventional material we know of, by a quite large margin (though it's not clear that strength will ever be possible to demonstrate on a macro scale), but diamond is far superior for compressive strength and hardness.

Re: [Spaceships] Nanocomposite and structural materials
 

Naturally. The better that I am talking about is "better for building the structural hull of an Oberth cylinder", where tensile stress in the circumferential direction is extreme, tensile stress in the lengthwise direction is rather more modest, compressile stress in the radial direction is only about a couple of hundred kilopascals, and mass is at a premium. That's really playing to the strengths of oriented fullerene fibres.

Re: [Spaceships] Nanocomposite and structural materials
 

Ok, so one of the things to take into account is sabotage. And while I'm not a materials scientist, the relative densities suggests that diamond fragments will be worse

And while AFAIK early studies say breathing nanotubes is also bad for you, it also seems a lot more survivable than a storm of what's essentially worse-than-glass fragments, especially with TL10 medicine. That, and the nanotubes will be embedded in a composite; with the right composite, the material can deform and break with an explosion, rather than shatter.

Making a non-brittle diamond-like substance that could be used as a structural material without those flaws seems fairly high-tech. TL11 suggests that it would require nanotech to arrange the atoms properly.