SkepticJ said:
Any ordered matter will fall apart eventually won't it? Why is atomic flaws happening after many years a problem for this space ribbon? Please forgive my lack of complex material science knowledge.
This isn't a long time-scale thing in an entropy-always-increases way. Basically, when an ordered phase forms, it does so because the free energy of that phase is lower than the phase it's forming from (this is, essentially, the energy of crystallisation in freezing, for example). The phase will configure itself to lower its overall free energy, given the temperature, the pressure, and the chemical composition*. The free energy is calculated from two functions - the
enthalpy, and the
entropy. The entropy is a configurational energy term.
Essentially, it is
always energetically desirable, due to the entropy, to have a few defects in an ordered structure. The equilibrium concentration of those defects can be calculated, and it is likely that thermal equilibrium (i.e. some defects) would be reached from a perfect original crystal over a timescale of
few years, even for a very stable structure such as carbon nanotubes.
It's probable, though, that if manufacture can be made cheap enough, and nanotubes can be made long enough, that they'll make stronger composites than carbon fibre - but they won't be orders of magnitude stronger, due to these missing carbon atoms. Your graph compares a theoretically perfect macromolecule to an engineering material - it's no wonder the apparent difference is so striking.
Hope that helps - unless you're familiar with the thermodynamic basics I've quite possibly flubbed explaining it well, though.
(* This is a simplification; there are metastable phases, for example, and transformations can be thermodynamically desirable but kinetically impossible if the temperature is dropped sharply (in glasses, for example), but it'll do for now.)
Could you explain this thermodynamic instability? Is it basically entropy? One problem a cnt ribbon would have is O1 in the upper atmosphere. Not sure what kind of damage it'd cause but oxidation from these reactive atoms cause damage to craft in low earth orbit over time.
