# How would the foundation/anchor for a space elevator work?

In a perfect scenario the space elevator is in Geosynchronous Orbit, it could be suspended a papers width above an egg, the egg would never be harmed and there would always be just enough room to slide a piece of paper between the egg and the elevator.

In reality there are a lot variables. The elevators orbit will be impacted by the moon (think tides). The land under the elevator will move (think continental drift).

How do you make or control the interaction between the elevator and the Earth?

If it was even possible (which I doubt) to anchor the elevator to the continental plate the forces would be much greater then Post-glacial rebound resulting in... well I don't know, but I think it would be bad.

Edit To Clarify: While it is possible that the end of the space elevator that touches the ground is is a thin flexible rope/wire that drifts around ground and absorbs fluctuation in distance between GSO and the surface like a kit string. In this question I am imagining that the elevator is solid inflexible tower, stretching into the sky.

• A detail to observe here is that although there may be a mass-element of the space elevator rotating in a geosynced fashion, the mass-element of the elevator reaching Earth usually will not. The cable will drift along the Earth's surface, which simply follows from the fact that Earth's rotation speed is not the local Keplerian speed. Commented Dec 28, 2016 at 15:32
• @AtmosphericPrisonEscape I have edited the question, a cable drifting like a kite string would not need a foundation or anchor, Commented Dec 29, 2016 at 16:29
• A good stabilization approach involves the elevator not being in equilibrium at GEO but with center of mass located past it, centrifugal acceleration providing an extra tension that counteracts drift, weather/wind, tidal forces, solar pressure and all other influences by pulling the tether outwards; this requires a solid anchor. Also, anchored lift doesn't need to be exactly on the equator, just near to it.
– SF.
Commented Dec 29, 2016 at 23:25
• You don't mention the density and tensile strength of the tether material. Or the capacity of the elevator. These would determine total amount of kilograms of the elevator structure. At geosynch altitude, newtons per kilogram is zero. Force from tether mass below geosynch is largely canceled by force from mass above. You'd want a net force upward to keep the elevator aloft. At the moment too little info is provided to see how much that net force would vary. Commented Jan 1, 2017 at 0:37

One proposed concept:

Central shaft vertical with branching diagonally downwards tunnels; constructed using the mining techniques. The tunnels filled with reinforced concrete (steel beams immersed in concrete). The tether branching/split into multiple strands, each anchored to a separate beam.

Each of the beams can support several hundred tons, and is about impossible to remove - it would require displacing thousands of tons of soil to rip the beam free; it's more likely to rip the beam apart than break it loose. This solution can be easily scaled as the shaft can go kilometers deep, and provide hundreds of such anchors; the total anchor strength can easily exceed durability of the tether.

• I think you should incorporate some of the detail you have in the comment under the question into this answer. The two parts together make a better complete picture. Commented Dec 30, 2016 at 15:46

The foundations would be more concerned with getting traffic on and off the cable in an efficient way, rather than cable engineering, especially since you are thinking of a rigid static cable. I imagine a curved, conical tower construction similar to a tall volcano shape, where cargo trains would approach the elevator site, start going uphill, and smoothly transfer onto the cable without pause. Descending trains, on the other tracks on the cable, would detach from the cable and slide down the mountainside on rails to flatten out and continue away from the site (probably rolling to a stop in warehouses for unloading and prepping for launch again).