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.

There are several reasons. Despite all the pro-station propaganda of the
past few decades that prominently sold the space station as a way point
to the planets, the stark physical reality is that it just isn't useful
for that purpose.

Although many planetary missions begin with an earth parking orbit, its
orbital plane is carefully chosen to coincide with that of the
interplanetary trajectory. To do otherwise would waste a *lot* of fuel
for no good reason. But the space station is in a high inclination orbit
to improve coverage of the earth and to make it easier for the Russians
to reach it from their high latitude launch sites. Since all of the
planets are in orbital planes not far from our own, they're all very
hard to reach from a high inclination earth orbit.

Even if the station were in a more equatorial orbit, the chance of its
orbital plane magically coinciding with that of any desired
interplanetary trajectory anytime during the interplanetary launch
window is extremely small.

Basically, the space station -- as conceived and especially as built --
is pretty much useless for all of the magical things it was once claimed
would do. Acting as an interplanetary way station is just one of them,
and the people who said it would should have known better. It's an
incredible scandal.

Phil