cfrjlr wrote:
[[proposal for lunar He-3 mining]]
The commercial amount of He3 needed would be 10,000 liters per year to
100,000 liters per year. He3 density is about 0.1g per liter at NTP, so
we need about 1kg to 10 kg of the gas per year. At average concentration
about 150,000 tons of regolith per year would need to be processed.
About 500 tons per day, 22 tones per hour
[[...]]

http://tinyurl.com/aqqa8hs

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About lunar elevators:

For a one time capital cost of US$800Million 2012, a lunar elevator can
be built today using existing available materials.
[[...]]

Some issues to tackle:
* How do you go about mining that regolith? How do you power that
mining equipment? I rather doubt there's any space-qualified
mining equipment available off-the-shelf, so what's the R&D budget
to develop & debug it?
* The Apollo experience says that lunar dust gets *everywhere* and that
it's highly abrasive. How do you fix that mining equipment when
(not "if", but "when") it breaks? Do you have people on-site on the
moon? If so, what's the budget for maintaining them?
* Precisely how do you go about extracting the He-3 from the regolith?
What's the R&D budget to develop and debug this extraction process?

I fear the elevator is only a small part of the overall budget.

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
on sabbatical in Canada starting August 2012
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam