i wonder why before various unobtanium requiring structures we wouldn't try some rail/coil gun in a [close to] vacuum tube going several kilometers up a mountain. After all, 2000 years ago it was possible to build that http://en.wikipedia.org/wiki/Roman_aqueduct , so building something like it up the Kilimanjaro (or any other mountain near equator like this http://en.wikipedia.org/wiki/Nevado_Sajama) should be pretty doable today.
"The barrel was to be 156 metres (512 feet) long, with a bore of 1 metre (3.3 feet).[3] Originally intended to be suspended by cables from a steel framework, it would have been over 100 metres (300 feet) high at the tip. The complete device weighed about 2,100 tonnes (the barrel alone weighed 1,655 tons). It was a space gun intended to shoot projectiles into orbit, a theme of Bull's work since Project HARP."
One cool proposal is StarTram [1], which has a long (100km+) maglev run in an evacuated tunnel to a linear accelerator up the side of a mountain, ending in a magnetohydrodynamic "window" to keep the atmosphere out, launching out the end fast enough to reach orbit. The acceleration of the first plan (30g) is too much for humans, so it'd initially be for cargo only.
The second stage is a crazy-awesome magnetically levitated tube that exits at an altitude of 22km, and gives low enough accelerations that a human could survive.
Or how about just this http://en.wikipedia.org/wiki/Project_Babylon for starters - was worked on by a guy who knew what he was doing:
"The barrel was to be 156 metres (512 feet) long, with a bore of 1 metre (3.3 feet).[3] Originally intended to be suspended by cables from a steel framework, it would have been over 100 metres (300 feet) high at the tip. The complete device weighed about 2,100 tonnes (the barrel alone weighed 1,655 tons). It was a space gun intended to shoot projectiles into orbit, a theme of Bull's work since Project HARP."