Sex and romantic entanglements among astronauts could derail missions to Mars and should therefore be studied by NASA, warns a top-level panel of US researchers.

NASA plans to return astronauts to the Moon by 2018 and later on to Mars. But a round-trip mission to the Red Planet would probably last at least 30 months and carry six to eight people. That would be a hotbed for intense crew relationships, says a report by the US National Academy of Sciences (NAS).

"With the prospect of a very long-term mission, it's hard to ignore the question of sexuality," says Lawrence Palinkas, a medical anthropologist at the University of Southern California in Los Angeles....

source

That was my first post for news, how exciting!

Now, let us discuss!!!!
I think that this is a serious issue and I would address it by spending some of that juicy NASA funding on making a sex simulator. That way, after your girlfriend has had those golf balls attached to her body and blue screened a "real" hologram will be available for the lonely guys on those trips. Ill let your imagination figure out the physical nessesity of intercourse though.

I say just make sure one of the astronauts are a female and all worries are gone.

One is not enough for a 30 or so month mission.
And sharing with 5 other guys would get.... not good!