Space elevator

A space elevator is a type of planet-to-space transportation system. The main component would be a cable (also called a tether) anchored to the surface and extending into space. The design would permit vehicles to travel along the cable from a planetary surface, such as the Earth's, directly into space or orbit, without the use of large rockets. An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and the other end in space beyond geostationary orbit. The competing forces of gravity, which is stronger at the lower end, and the outward/upward centrifugal force, which is stronger at the upper end, would result in the cable being held up, under tension, and stationary over a single position on Earth. With the tether deployed, climbers could repeatedly climb the tether to space by mechanical means, releasing their cargo to orbit. Climbers could also descend the tether to return cargo to the surface from orbit.

Possible materials used in its construction: Carbon nanotubes (CNTs), boron nitride nanotubes, and diamond nanothreads.

It is estimated that a space elevator will have a 95 percent cost advantage over orbital spaceflight and could potentially control all space activities near its planet. Construction would be hugely expensive but return on investment excellent.

Examples:
 * In 2061: Odyssey Three (novel by Arthur C. Clarke), the possibility of a space elevator is realized after a groundbreaking discovery that Jupiter's core had been a solid diamond; as the hardest substance in nature, suddenly available in vast quantities, it facilitates the construction of a solid elevator rather than the more common tether structure previously envisaged and in 3001: The Final Odyssey a ring habitat now exists around the Earth that is connected to the surface via four inhabitable towers (successors to space elevators)
 * The Fountains of Paradise (novel by Arthur C. Clarke) is about the construction of a space elevator on a mountain top on Earth in a fictionalized version of Sri Lanka.
 * The Long Mars (novel by Stephen Baxter and Terry Pratchett): In the parallel Martian worlds, the existence of the elevator is proven as to be a logical step for a long-gone civilization.
 * The Mars Trilogy by Kim Stanley Robinson depicts space elevators on Earth and on Mars, the cables of which are made of carbon nanotubes manufactured on asteroids and lowered into each planet's atmosphere, using the asteroid as a counterweight.
 * a space elevator in New Mombasa, Kenya in the year 2552 is seen in the Halo Universe
 * a space elevator is a World Wonder in Civilization