re elevator to the top floor reading from a amoco performance products data sheet their erl resin with t carbon fiber reinforcement has a compressive strength of psi it has a density of lb cu in therefore the theoretical height for a constant section column that can just support itself is million inches or ft or statute miles now a real structure will have horizontal bracing either a truss type or guy wires or both and will be used below the crush strength let us assume that we will operate at of the theoretical strength this gives a working height of miles for a constant section column a constant section column is not the limit on how high you can build something if you allow a tapering of the cross section as you go up for example let us say you have a pound load to support at the top of the tower for simplicity in calculation this requires square inches of column cross sectional area to support the weight the mile of structure below the payload will itself weigh lb so at mile below the payload the total load is now lb a increase the next mile of structure must be thicker in cross section to support the top mile of tower plus the payload each mile of structure must increase in area by the same ratio all the way to the bottom we can see from this that there is no theoretical limit on area although there will be practical limits based on how much composites we can afford to by at lb and how much load you need to support on the ground for which you need a foundation that the bedrock can support let us arbitrarily choose billion as the limit in costruction cost with this we can afford perhaps lb of composites assuming our finished structure costs lb the lb figure is just for materials cost then we have a tower payload mass ratio of at a mass ratio per mile the tower height becomes miles this is clearly above the significant atmosphere a rocket launched from the top of the tower will still have to provide orbital velocity but atmospheric drag and g losses will be almost eliminated g losses are the component of rocket thrust in the vertical direction to counter gravity but which do not contribute to horizontal orbital velocity thus they represent wasted thrust together with drag rockets starting from the ground have a velocity penalty to contend with this analysis is simplified in that it does not consider wind loads these will require more structural support over the first miles of height above that the air pressure drops to a low enough value for it not to be a big factor dani eder dani eder meridian investment company w h rt box athens al location deg n deg w m alt
