What is space elevator used for?

Answer 1

Answer 1.

It WOULD be a device that could lift objects from the surface of the Earth up into Earth orbit without the use of rockets.

Answer 2.

Caveat lector: What is described in "Answer 1" by a previous contributor is a misconception.

The Space Elevator (SE), -- as is proposed by Brad Edwards, which is also known as the "Centrifugally Extended Carbon-Nanotube Tether Space Elevator" and like any of the others proposed systems, -- can only provide for a method to vertically reach a particular altitude relative to sea-level. But it DOES NOT provide a method for the tangential (i.e. the horizontal speed,) for orbital insertion, (i.e. the only angular acceleration that the tether can inject to the payload mass being carried is the angular acceleration that the tether itself has at the altitude in question, which is also the same angular acceleration of our planet).

What the above means is that overtime any object released from the tether at any altitude below the Geostationary Orbit (i.e. the altitude at which the center of gravity of the elevator system will be,) would eventually fall back to Earth's surface. For example; If the mass is released at the operational altitude of the ISS it will pretty much fall back to Earth almost vertically.

Any space elevator, (as for example a SpaceShaft,) is nothing more than a device used to eliminate the need of a rocket's 1st stage in reaching an altitude in which tangential velocities are to be reached by means of propulsion systems. Moreover, even if a satellite is intended for GEO insertion; it will still need to have some on-board propulsion system to at least get away from the elevator's car, (or climber,) and neighboring surroundings of the tether or SE station, which is pretty much as what a rocket's 2nd stage has to do.

Another important factor to further illustrate the mechanics of the popular Edwardian system is the importance of the release of any cargo, including satellites, at GEO. If a propulsion system is ignited while still being held at a required altitude other than GEO or above will put the tether under stress and a consequential deflection which might destabilize the system. N.b. if just one such events does not cause the described consequence, after a number of such activities will certainly destabilize the system.

The requirement of reaching a GEO altitude has other consequences which are related to orbital mechanics. What this means is that a significant amount of fuel will still be needed for the relocation of satellites intended for orbits other than GEO, e.g. anything intended for the ISS will need to travel all the way from GEO down back to the orbit at which the ISS may be, being anywhere between 200 km up to 400 km of altitude. Compare these distances with the distance from sea-level up to GEO which is at 35,786 km (22,000 mi), and this is the minimum possible altitude and not the desired altitude, (see Wikipedia's article about GEO).

So after the extended descriptions I have given above we can redefine the popular belief to:

1. A system to ELIMINATE THE NEED OF THE 1ST STAGE OF A ROCKET and
2. for the ASSISTED ORBITAL INSERTION of spacecrafts by providing some free-ride speed.