Just a short late night post: I have been thinking about all those fun sci-fi and educational games I played as a kid..
Thought I should start making a list of modern educational games.
So, here is the Space sim list. I have not played most of these yet, but am checking them out.
First up is Kerbal Space Program. If the demo videos are to be belived, this game will be a riot. You are in charge of the fictional Kerbal's space program. Develop rockets, build mission plans, and design space craft and probes. Fly your own missions.
Orbiter and Kerbal have a lot in common visually. But Orbiter is designed to be a realistic simulation of the Space Transportation System (Space Shuttle). Highly detailed and accurate, this seems to be heavy on the educational aspect. Includes the ability to program your own simulations.
NASA's Moonbase Alpha is a resource management simulator which takes place on the moon. Your goal is to collect resources, build the base and conduct experiments and missions. I remember playing a very old version of this game back when I was a kid in Space Academy. At the time, it was a top down sim, much like the old Sim City series.
IF you want more games, on various platforms, here is a wikipedia list. I remember playing those Space Shuttle sims on the Commodore 64.