While it is true that an elevator is much more mechanically efficient than a rocket, the total effort and embodied to build and maintain a 12 mile high platform to launch rockets or spaceplanes is going to represent an enormous investment that would not be matched by thousands of launches from sea level, even before establishing that there efficacy gains from launching at 12 miles altitude are almost a rounding error. And you aren’t going to have a single pump drawing fluid up a 12 mile pipe; a positive pressure pump at 20 bar (~300 psi) could lift water 200 meters (not accounding for losses). Doing this repeatedly over a 12 mile total head would require nearly a hundred pump lines in series going up the structure. And of course, we’re probably talking about cryogenic propellants such as LOx and LH[SUB]2[/SUB] which have to be refrigerated despite all of the mechanical energy you’re putting in to pressurize and move them. You’d be lucky to get more than vapor at the top.
Stranger