Figure from ROBOT, Moravec, Oxford, 1998, Chapter 5: The Age of Robots, page 158
Synchronous skyhook

A synchronous orbital bridge
A tapered cable, anchored to the equator, kept taut by a ballast 150,000 kilometers above, supports a stream of ascending and descending hypersonic elevators in the cheapest and cleanest way to link Earth and space. The cable tapers to a maximum diameter at synchronous orbit, 40,000 kilometers above the surface, and has minimum cross section at both ends.