[Spaceships] Nanocomposite and structural materials
 

I'm doing a bit of modelling of the engineering requirements of space habitats with spin gravity (for FLAT BLACK, where there is no synthetic gravity). In particular, I'm investigating how thick (and therefore massive) you have to make the hull of a cylinder spinning on its axis to support its own mass and that of a load (of armour, habitat, radiation shielding &c.) against the centrifugal effect of their inertia. It turns out (unsurprisingly) that the necessary thickness (and therefore mass and cost) of the structural hull depends strongly on the density and tensile strength of the structural material. I figure that:

t = r(P₁ + a₁λ)/(σ - ra₁ρ)

where

t = minimum thickness of the structural hull
P₁ = air pressure at the deck level
a₁ = centripetal acceleration at the deck level
λ = areic mass of the load (armour, shielding, habitat fittings, landscaping etc.)
r = radius of the cylinder
σ = tensile strength of the hull material (safe limit)
ρ = density of the hull material

I can find figures for the strength and density of some of the materials mentioned in GURPS Spaceships, such as mild steel and high-tensile steel, high-strength aluminium alloy, and titanium. Also, for polyester reinforced with glass fibre (a surprisingly good material for the purpose at TL7), epoxy reinforced with aramid fibre, epoxy reinforced with graphite fibre, diamond, cubic boron nitride, and carbon nanotubes (buckytubes). But there are some posited futuristic materials mentioned in Spaceships of which the identities are artfully vague, and for which figures are supplied implying their relative effectiveness as armour but not their actual density and tensile strength: metallic laminate (TL8), advanced metallic laminate (TL9), nanocomposite (TL10), space-adapted wood, living tissue, living bioplastic (TL10), exotic laminate.

Armour materials might not be the same as structural materials, of course.

Can anyone suggest what structural materials might correspond to the armour materials listed in Spaceships and what their densities and tensile strengths might be? Since FLAT BLACK is TL10 I'm most interested in what might correspond to nanocomposite.

Re: [Spaceships] Nanocomposite and structural materials
 

I built a little calculator based on this work. It's an Excel workbook with no macros.

Just at the moment the list of possible building materials is a bit incomplete and some of the values for strength are questionable. But I put it on Dropbox for review and personal use anyway.

https://www.dropbox.com/s/7iilf35hdx...ator.xlsx?dl=0

Re: [Spaceships] Nanocomposite and structural materials
 

For some reason the words glass fibre reinforced polymer cover the number 1550.

Re: [Spaceships] Nanocomposite and structural materials
 

The link leads you to a browser page that shows a version of the sheet that is suitable only for giving an impression. It can't actually be used.

Click on "open with" in the menu bar on the page and select "MicroSoft Excel online" or "MicroSoft Excel " (if you have it installed). Or click on the more menu "…" in the top right and select "download".

Re: [Spaceships] Nanocomposite and structural materials
 

This is already covered in Spaceships on page 30

Re: [Spaceships] Nanocomposite and structural materials
 

"Manocomposite" is kind of a catch all term in GURPS for different types of material that's the next step up from modern and next gen metal-matrix composites.

The main types covered are titanium nanocomposite, polymer nanocomposite, advanced polymer nanocomposite , ceramic nanocomposite (not sure if this would make a great building material since it's pretty brittle), and advanced nano-laminate.

Density is pretty easy to figure for these material.

Titanium Nanocomposite: 4g/cc.
Polymar Nanocomposite: 1.5g/cc.
Advanced Polymer Nanocompsite: 1.6g/cc.
Ceramic Nanocomposite: 3.19g/cc.
Advanced Nano Laminate: 1.27g/cc.

Tensile strength on the other hand... isn't as so clear cut since GURPS doesn't really go into this aspect of armor materials in detail and it doesn't help that outside of some very early experimental examples, a lot of these materials are currently hypothetical. However there is at lest some correlation between it and how good a material is at stopping bullets I can guessitmate titanium nanocomposite as having a tensile strength of at lest around 1,400 mega parcels, give or take (though given that there would probably be a ton of different types for different jobs this number is bound to differ a bit for structural material vs armor ones). The other examples are bit trickier to figure out thought IMHO titanium nanocompsite is probably the best example.

One ton (metric) of titanium nanocompsite costs (at TL10) $132,277.20.

One square meter of it one centimeter thick weighs 10.2kg and has a DR of 69.

Hope this was at lest some help.

Re: [Spaceships] Nanocomposite and structural materials
 

With all due respect: it is not. Even on page 30, Spaceships does not identify structural materials corresponding to those armour materials, nor name the armour materials specifically, nor list the density or tensile strength of any material.

Re: [Spaceships] Nanocomposite and structural materials
 

Thank you. Density figures get me halfway there; names of specific materials may help me find at least speculative values for tensile strength.

Re: [Spaceships] Nanocomposite and structural materials
 

No problem man, this kinda of stuff is pretty much by bread and butter heh. Your Flat Back setting is pretty kick-awesome so I got no issues giving what assistance I can.

Pyramids 3-86 Cutting Edge and 3-96 Tech and Toys IV both have an articles written by David Pulver that have a lot of info on advanced armor material so you might want to check them out if you can.

Re: [Spaceships] Nanocomposite and structural materials
 

For starters that's the best your going to get, but beyond that the answer doesn't really exist. Structural weight is included in the Control Room system, not the individual systems. Further more given that the largest ships is only 700 yards long and I'm pretty sure that we already build bigger ships is very plausible.

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.