Simple, take number of all GT and LT games that there not limited by some scenario properties, and how many of them even had spaceship parts built. Or maybe some of them even completed spaceships? So divide number of games with SS components build from total games and you get probability of having spaceship involved. My guess would be that it is below 10% for even attempting to build it, and probably 0% for completion. But thats my "gut feeling", so I want to know the reality.