Probably pointless post, but I just realised that I never won a space victory all my time playing Civ4. May be I should try that.
After 9 months of cIV I only had one space victory.
It was my first cIV game on chieftain (or was it warlord?) level.
Then I played "P666-02 fix another trash game" and gave it some real thoughts.
It was not really the same old game I usually play (going cultural or domination mainly, with the odd diplomacy victory now and then).
Give it a try, you'll like it (although the end game is a bit dull).
What I learned from this game:
- space race is about teching and building
- state property makes late game building really easy
- you don't need more than 3 high production cities, if you have enough hybrid cities.
- casings can really be slow built. No point having 5 casings while you cannot even start building the engine.
- with a little MM, you can shave off 10+ turns of the late game building. How?
1) overflow. This is VERY significant if you cash rush things just before starting you space part.
2) starvation. You don't need to have sustainable population. You need the hammers.
3) chopping. You can $rush factories, but cannot $rush parts. So conquering a good production site with forests, you can keep those wooden hammers for this late rush. You think it's not worth it? count again! In the Iron Works city, each chopping gives some 100 hammers

4) Statue of liberty can give you a free engineers. Don't forget to $ rush those factories and powerplants. Don't want to build it? what are you building in your IW city? casings?
5) settling prophets and engineers is a long term winning move. Space ship is long term.
6) internet. Believe it or not, you can "trade" until the end of the game. In fact, if you beeline to fiber optics, it's really easy to get all necessary techs.