Carbon nanotubes are seductive. They are very strong, diamond like, in that circularized plane. But when you extend the tube to macro dimensions, you have problems with phonons and the &#x27;rogue waves&#x27; that add up over such long distances (relative to atoms). These phonon effects can and do add up to break the nanotube as there is so much energy in the phonon that it overcomes the intermolecular bonds. You can help a bit with an onion layering of nested nanotubes, each a little bit bigger. But that doesn&#x27;t get you much further. Doping the tubes with other atoms reduces the strength by a lot, but may increase the length. Isotopes of carbon, like C10 or C14, do help a fair bit. However, they tend to be too radioactive to be stable for a project like this. You&#x27;d have to continually replace the rope as the dopant isotopes would decay away and the nanotubes would self destruct again. In the end, we need new ideas to help with this. Perhaps some strange electron-phonon interaction? I don&#x27;t know.