Can you imagine how irritable these people would get at each other ?

Sounds like marriage.

The pumps don't work 'cause the Vandals stole the handles
Bob Dylan

No privacy, little free time, no sex, everything you say and do being monitored...

For centuries ship's crews had to deal with exactly this kind of thing. The usual solution was to have a well defined set of rules and a captain who had absolute command. When disputes arose, the captain was judge, jury, and even executioner if necessary.

I suspect something like that would be necessary for interplanetary travel as well.

I don't have to, I was in jail for only a month for a traffic violation and can very much understand what it'd be like. It was only then that I understood what the phrase "hell is other people" really meant. There's no way a Mars mission is going to happen without someone eventually snapping, the confinement breaks everyone eventually.