The best time to switch governors is right after you have built your spaceport and you are starting to build the earth satellite. If you are hard building the spaceport, the higher base production from Magnus will speed up the completion of the spaceport. The 5-turn downtime matters less for earth satellite, because royal society builders provide a percentage of the total project cost and the earth satellite project has the lowest cost of all science victory end-game projects. If you don't already have the royal society, the more reason to get the downtime before you do. If you are purchasing the spaceport with Reyna or Moksha, you obviously want her/him out of there asap and install Pingala/Magnus. The choice of Magnus vs Pingala also depends on how many builders you can afford to speed up the science project. If you can afford to sacrifice one 7-charge builder per turn (the max), then it favors Pingala. If you can't afford to sacrifice any builder then Magnus can the better choice depending on how many IZs you have in range. (If you are as "maniac" as I am, I suggest modeling the production in a spreadsheet.) As a rule of thumb, any great person that provides a percentage toward space race projects (Goddard, von Braun, Kwolek) will favor the higher base production (ie Magnus) and any great person that provides raw production toward space race projects (Korolev, Sagan) will favor the higher percentage bonus production (ie Pingala). In your choice of governor, you will need to evaluate if science or production will become the main bottleneck. If you are getting so much free raw production from great people that production becomes no limiting factor, then science most likely becomes your bottleneck and you just need to place Pingala wherever he will provide you the most science. However, these questions should only be of interest to you if you are an extreme min-maxer. And if it were the case, you wouldn't see any of these great people in your game, because they come too late. First, really high production in your main spaceport city only really matters if you are researching all the late game techs at the pace of one per turn (and sometimes more if you are pillaging or using great persons such as Darwin). If you think you can get to Offworld mission in 15 turns, then you ideally need to produce all the required parts before then. You then need a lot of production. If you think you will only get to Offworld mission in 30 turns, then you only need half as much production. You need to evaluate if you are facing either a production or a science bottleneck. Second, you need to keep in mind that the UI is misleading: it doesn't show the production you get from Space Initiative, ICS and Synthetic Technocracy. Third, you also need to factor the production you will get from royal society builders. Now, in an ideal scenario (such as the one in this game where Offworld mission is right after Smart Materials and where production becomes the main bottleneck) you would need about 330 total base production with Pingala to get 1050 hammers with a 7-charge royal society builder to build the Exoplanet in 2 turns and churn out 1 laser project per turn (without Hong Kong).