I bought High Frontier recently, and have been trying to work my way up the learning curve out of the gravity well of confusion. As games go these days, this one really is rocket science. The map I have "only" goes out to the Jovian Trojans; there's a poster map which goes out to Pluto, the Kuiper Belt, and beyooooooond. It's somewhat educatiomonal too, reflecting both the astronomy and engineering fairly accurately, even if it's somewhat simplified. The basic game rules make things easier (well, less difficult), but the extended game throws in stuff like radiation hardening and heat management, challenges I've dealt with in my real-life engineering work.
I'll be looking for folks interested in giving it a try soon... it looks quite interesting, and reasonably short for a game of its depth.