Budding Robert Goddards and Werner von Brauns should take a look at Space Agency, an iOS sim that lets you design your rockets and use them to explore the solar system.
By all accounts this game is pretty full-on, so don’t go looking for a casual coffee break game here. I mean, come on – this is actually rocket science. But if you grew up reading the same nerdy space books that I did, you’ll probably be all right.
Space Agency seems to be mission-based, so it’s not a free-form space exploration sandbox like the PC’s Kerbal Space Program. But regardless, it appears to have a lot of depth – there’s no trailer for it here’s a very comprehensive gameplay video that should give you the flavour.