The illogic of Mars (was Re; New Member)

Hi Mike - I agree that we can make reasonable technological and economic
projections that suggest SPS can be practical - but it's still a
projection of 3 or 4 orders of magnitude from what we've got right now,
unfortunately! I guess my point was that, in that projection, a final
factor of 2 in costs could make a lot of difference to profitability and
competitiveness (witness the recent factor of 2 change in oil prices)
but there's no way at this point our projections will be accurate to a
factor of 2.

By the way, an interesting collection of arguments along the
energy/environment lines for a return to the Moon (the other
alternative, besides asteroids/high earth orbit and Mars) is in a new
documentary from Chip Proser - I just got a review DVD which is quite
impressive - you can see a preview here: http://www.stickymedia.com/
(click on the page and then one of the "Preview" options).

Combs, Mike wrote:

> [...] Anything which vastly improves
> the economics of ground-based solar, say, would also do the same for
> SPS, and the advantages based on the physics of the two situations would
> still remain. [...]

I've gotten some pretty convincing papers from NREL that claim a factor
of 10 improvement in solar panel costs is possible using thin film
materials at high production levels, with basically current
manufacturing technology. I'm not quite clear on why nobody's doing
this, but maybe it's just a matter of demand needing to ramp up to meet
the necessary production levels (10's of GW/year).

But... the two are slightly distinct: if launch costs stay high, SPS
requires either very light-weight solar panels or space in-situ
manufacturing, neither of which directly relate to ground-based solar.
On the other hand, if launch costs drop significantly and we don't see
such a rapid improvement in ground solar costs, space solar becomes more
attractive - it really depends which of the components of the system
make up the highest portion of costs. I'm pretty optimistic, but it's
not guaranteed.

Arthur