Unless you're envisioning spacecraft with literally hundreds of astronauts, the first will be anything but easy to solve. Doesn't help having an awesome spaceship if everyone on board goes batshit crazy after six months.
Bubbleheads are tested in Submarine School for compatibility with the idea of living in the intellectual equivalent of a sewer pipe for months on end with each other. I'd assume NASA would do the same. End of the day make sure you know who holds the keys to the weapons locker.