Megastructures

Megascale engineering is the construction of structures on a scale of at least 1000 km in length (10⁶ metres, hence the prefix "mega"). Such large-scale structures are termed megastructures. The only category beyond this is "gigastructures".

Astroengineering is the extension of megascale engineering to megastructures on a stellar scale or larger, such as Dyson spheres, Ringworlds, and Alderson discs.

With current technology, only a space elevator or some launch-assist platforms could be built using conventional engineering techniques. Carbon nanotubes may have the requisite tensile strength for a space elevator.