Each crew member had both a set of skills and a number of personality traits that radically changed how they reacted to your decisions. They might be xenophobic and disapprove if you were too nice to aliens, or curious and want you to investigate everything no matter the risk.
One of the neatest things was the "promise" mechanic. A group of unhappy crew members would corner you and ask you to promise to change your ways - to stop helping aliens, or to take every opportunity for scientific exploration. You could either brush them off, making them a bit less happy still, or make the promise. This would make them happy again, but it constrained your future choices.
So what happened to the game? I made the mistake of putting in a lot of polish and content before it was actually fun to play. So when I had to change things to try and fix the gameplay, each change was a lot of effort. Eventually, I started again from scratch, and put together a simpler prototype that was actually fun.
With the prototype in place, I started work on the proper, pretty version, with a beautiful star map and a clean UI. But at that point, I had been working on the project for about four years, and was really tired of it.
So in September 2013, I spent a few days putting together a prototype of an airship construction and combat game. Something more viscerally satisfying involving explosions. (I was pretty angry at the time: the company I'd been freelancing for was self-destructing and had failed to pay me several thousand dollars worth of invoices.)
I put Airships on IndieDB, and the immediate reaction was highly positive. It quickly got more attention, more followers, more comments, than Space Exploration had managed to attract in months. So I continued working on Airships, still intending to get back to SE:SS sometime soon.
Well, that never actually happened, because Airships kept being better-received and more fun for me to work on. What was meant to be a quick prototype gradually turned into an actual game.
So will we ever see SE:SS return? Perhaps. The prototype I have is actually pretty fun to play. There's still lots of work to be done on Airships and related projects, but after that, I have a shortlist of about 3 games I might make next, and SE:SS is one of them. By then, I hope that a few years' perspective on the game will let me complete it rather than going around and around.