When a colonisation crew of four escaping a threatened earth, awakens by ship failure, a useless artist must save the mission and mankind from a captain, incorrectly believing one of them isn’t human.

I think you've got a great start, just keep working at it and you'll get it. My suggestion would be to be careful not to confuse your backstory with your story. I'm guilty of this a lot as well. Just keep in mind the story is about your main character, not the world in which they exist.

Without getting too heavily into screenplay structure, I agree with bondthewriter on this one. Don't worry about the rest of the setup - just make sure the inciting incident for your CORE narrative is explained. It does sound like this story begins because they are woken from hypersleep.

I've found this logline really hard to write off the top of my head - but I will say that I think you need to keep mention of what it is that the artist is protecting; specifically, the survival of the human race.

Thanks for your feedback.
I thought that the 10 first pages should explain how the thinking machine gets created, and how it enlighten the humans - giving sight to the blind and ears to the deaf, but at the cost of its persistence. Its simply unstoppable. A secret project to preserve the human race is created with a mission to settle on a new planet etc...
Thats the setup.
But I guess one can leave out the setup from the logline? I tried to have some of it there (with "threatened earth"). Infested earth is probably better but then I want to make clear its not a virus or a plague but rather an uncontrollable evolution (like the industrial revolution).