The report spends 350 pages laying out a detailed case for the space elevator. The central argument — that we should build a one as soon as possible — is supported by a detailed accounting of the challenges associated with doing so. The possible pay-off is as simple as could be — a space elevator could bring the cost-per-kilogram of launch to geostationary orbit from $20,000 to as little as $500.
IMHO, this and the difficulties in obtaining a counterweight makes 2035 seem optimistic even if the enormous political and economic hurdles can be overcome.This report lays out a number of technological impediments to a space elevator, but by far the most important is the tether itself; materials science has still to invent a substance that could provide the strength, flexibility, and density needed for a space elevator.