Sorry for giving you the wrong impression. I'm not in the military.

I'm only an expat worker in the Middle East. But I guess the conditions we faced seems to be worse than what US military personnel faced!
It's just a fact that some Arab countries in the Middle East like Saudi, Qatar, etc tend to be extremely shrewd with handling of expats from 3rd world countries.
Prison-like living conditions is the average despite the fact they are one of the richest nations on the planet.
Back to topic. I know how it is to be away from everyone you know with very little opportunity of returning home. In a place that virtually treats you like a prisoner.. I endured it for two years while trying to work flawlessly in the HQ.
I believe it's possible. You just need a crew who can effectively manage their emotions, remain very calm even in life-threatening situations and be reasonable.
I read an article about the very rigorous process of selecting submarine crews for the US Navy. I think such standards must be imposed even on the civilian specialists that will be included on deep space missions.
Submariners spent years on missions, many months underwater without surfacing and without any view! And they seem fine. But of course, the people who crew submarines aren't your usual Navy guys, they are quite something out of this world maybe!