Building a spaceship or "transstellar colony ship" is the only official way to win a game of C-evo. You need to have a Space Port built in one of your cities. The ship itself needs parts, not unlike those needed in games of Civ1 and Civ2 but much harder to construct. As with other things you build, the material cost is 25% less than standard if your difficulty level is I and 25% more on level III. The in-game manual tells you the cost for your level. You cannot use "rush-buy" or Freight (C-evo). You can trade spaceship parts with a friendly nation - but not with the standard AI in v 1.2.0 because it is not able to do that (or several other things on offer in the diplomacy screen).