Doug,

I've been puzzling about this for a while since I saw your resonse.

In a simplistic way, you're right, if what we're doing is an Apollo-style one-time visit to another planet or moon, and we're throwing everything away on our return.

However, if you also look at the option to reuse the whole spacecraft on the next mission without relaunching it, then you're comparing the mass of fuel needed to dock with a (hypothetical) elevator to that of a heatshield AND the entire craft it is attached to.

In this case, the elevator may become a better option, especially if it is also an in-space refinery and gas station using solar power to process ice into fuel. If the ice is not lifted out of earth's gravity well, it is cheaper than the launch/re-entry/trash model.

Of course, as we sit here discussing a space elevator, we're like ancient tribesmen discussing why you would want to build a 3600m tarmac runway when one can simply paddle across the river to the other bank in a dugout canoe.

The scale of engineering required to clear debris all the way out to GEO and beyond and build a space elevator, even if the materials were available, is simply beyond our current political and industrial organisation. We would have to evolve our society considerably before we could seriously contemplate building one (and that would also answer the question, "why spend money in space when we have so many problems on earth?")

((Of course, the evolved society might not be a bucolic utopia with cake for all to eat. It might be a much harsher industro-technological society that subsumed individuality to the need to get a space elevator up before we become extinct. Or it might be a well-adjusted ad free society. Who knows?))