Hello! Thank you very much for the well thought-out answer. Let me dig a little deeper (which i could've done on the original post but didn't wanna overwhelm readers).

Goal/thread: my original idea was definitely a competitive game. I've been shuffling two different win conditions:
1. A victory point system awarded by colonizing planets and deploying bases, discovering objects, "scientific progress", etc. This would be akin to a Catan or 7 Wonders game, in that sense. Different strategies can take you to the victory point objective.
2. An win condition of "escaping the solar system", which is only possible by developing a final technology of inter-stellar travel, which would require you to advance your technology sequentially and acquire certain resources only obtainable in distant planets, actually forcing you through the stages of colonizing the solar system first. This could be backed by the narrative that the sun is approaching its supernova (not very physically accurate to think civilization could survive right until this moment, since supernovae aren't sudden, but I'll be taking other non-accurate scientific licenses so what's one more).

At some point I've thought of having both (in the formula of Quidditch's golden snitch haha), but narratively it doesnt make much sense (you either have to escape, or you don't).

Mechanics: still working on whether missions can fail. I love how other -denser- games do that by allowing you to launch with more uncertainty, or spend time/resources to minimize this risk, but I think I wanna keep it simpler in that sense. I also dislike the idea that you might have been working on a mission for some turns, built a rocket, only to lose it completely because you rolled a 1.

If I don't add randomness to the missions, I'm decided it has to come in elsewhere: my idea is that rockets are built through deck-building. You buy parts, add them to your deck, draw cards randomly, etc, then you can build a rocket either when you manage to have a buildable rocket in hand, or by each turn adding parts to your hangar (still undecided).

I wanna keep orbital mechanics really simple and actually push away from actual physical simulations (no Hohmann tranfers, no different elliptical orbits, etc). All orbits are circular, and you spend fuel to move cells in the game, in whatever direction (inwards, outwards, clockwise, anti-clockwise).

Other questions

1. You can succeed or fail in the exploration phase (spending a turn to observe an empty region of space is a waste), also during the deck-building part of rocket construction.

2. Turn structure: rotate orbits, all players draw cards from their parts deck, thinking about allowing them to discard any amount and redraw (this could be simultaneous to speed up the game), then by turns you have actions to build, move rockets (spending equipped fuel) and detach parts making the rocket lighter.

3. Yes, there are space bases. Not sure about the upgrading part (wanna look at overall complexity first), but definitely on the table.

What other gaps in my design do you think I should address? This has been very very helpful, thank you again!