I found the solo variant really hard to accomplish in 10 turns, so I tried keeping the mission deck in a seperate deck. That way if I wanted to trade out a mission I knew where to go. Completing 6 missions in 10 turns seems really hard solo.
I know it's been a few years since you posted this, but I recently started playing Moonshot solo. At first I found it frustrating, as your hand gets clogged up with missions. But I think that's part of the challenge, deciding whether to cycle through missions by scrubbing ones on the board or push your luck that you'll get the equipment you need to launch the ones already on the table. There are some neat subtleties to the solo play I hadn't seen before. Took me three plays to beat but I think I have a handle on it now.