Economics (was Critical time)

Mike Combs wrote: > OK. But if a mass-driver launched sufficient
mass to build 5 Island 3's over its operational lifetime, that would
be around 5 billion tons. How many individual kilogram launches would
that be? If we amortized construction & infrastructure costs, how
finely-divided would those costs wind up being?

Robert Clements replied> You're still not included all of the
infrastructure launch costs involved in setting up the mass drivers
.... There's been a recurring nightmare in space exploration where
large fortunes have been spent in developing technology to the point
where you no longer have any money left to fly the actual mission....

The two of you have hit on the fundamental dilemma: average cost vs.
marginal cost. (Personally, I don't think people should graduate from
high school not understanding the distinction, but the pitiful state
of education is a whole other topic.) For mature industries with
large markets, the answer is almost always going to be to reduce
marginal costs (e.g., the music industry with CDs). But for fledgling
industries, finding the right balance of improving capital to push
marginal costs down is very tricky.

For the Moon specifically, since no suitable propellant is found on
the moon, a propellantless techology (i.e., mass drivers or thethers)
will eventually be most successful, if mass launched increases
continually. But we don't have that assurance that launches from the
Moon will increase.

By the same token, most of these alternate propulsion ideas for
Earth-to-orbit are tackling the wrong problem. The cost of hydrogen
and oxygen is basically just the cost of electrolysis and
liquification. I've read conflicting analyses of what that cost is,
but I think in every case, the cost of LH/LOx fuel was less than
$10/kg payload to LEO. The rest of the tremendous Shuttle launch
costs are for employing a veritable army of technicians and for
amortizing the large capital costs. (I forget the exact figure, but
I've read that if the airlines were run the way NASA runs the shuttle,
the cost of a trip from New York to Los Angeles would be something
like $100,000 to $1 million.)

++JohnWheeler