In article ,
wrote:
I would like to know why we don't travel to Mars by first lifting many
loads of fuel to the space station. The actual spaceship would be
assembled in space, at the space station, from parts that are lifted
there the same as the fuel is lifted, by conventional rockets...

The idea is an old one -- early studies simply *assumed* that even a lunar
expedition, never mind one to Mars, would have to be done that way -- and
things will undoubtedly be done that way (using some space station, not
necessarily the current one) eventually. The question is whether it's
worth doing this for initial, relatively modest expeditions.

The answer depends quite sensitively on the assumptions you make, like
whether the current space station is used (it's in a poor orbit and is not
equipped for the job), just how big your expedition is, and whether your
goal is a one-shot program like what Apollo became, or something with an
orderly growth path.

There are two classical problems with this concept. First, it incurs some
up-front investment which isn't repaid quickly, so it scores poorly by the
standards of people who propose one-shot programs (some of whom don't
realize that that is what they are proposing...). Second, it involves you
immediately with the extremely expensive and inefficient bureaucracy that
runs current US manned spaceflight, and some advocates of NASA Mars
expeditions fantasize that their schemes can somehow avoid such
involvement if only they avoid using the shuttle and the station.

...the thrust required might be only
1/20 of what it would be if launched from earth, so a small propulsive
system will do the job.

Yes and no. There are still efficiency losses if thrust is too low, so
you don't want to make the propulsion system too small.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |