With space travel so expensive, how can we afford to build such massive structures in space?
Make no mistake, lifting the materials from the Earth for even a Bernal Sphere would bankrupt the global economy. That’s why we will use space resources. Most studies have looked at mining the moon, although Earth-approaching asteroids are another option. A pound of ore can be lifted from the moon to a high Earth orbit for less than 1/20th the energy as from Earth to that same orbit. In addition to having low gravity, the moon is also airless, so we wouldn’t necessarily have to lift the ore with rockets. Instead, a mass-driver could catapult lunar resources to a location in space (Earth/Moon L-2 point) where they could be captured and transported to an orbital refinery.
