The ESA proposes a long duration study to mimic a 17 month trip to and from Mars. But that is because the eggheads at NASA and the ESA will not look at the real practical solution that would get you there in less then one month, Project Orion! Typical, summed up best by Bruce Willis in Armageddon:
Harry Stamper: What’s your contingency plan?
Truman: Contingency plan?
Harry Stamper: Your backup plan. You gotta have some kind of backup plan, right?
Truman: No, we don’t have a back up plan, this is, uh…
Harry Stamper: And this is the best that you c – that the government, the *U.S. government* could come up with? I mean, you’re NASA for crying out loud, you put a man on the moon, you’re geniuses! You’re the guys that’re thinking shit up! I’m sure you got a team of men sitting around somewhere right now just thinking shit up and somebody backing them up! You’re telling me you don’t have a backup plan, that these eight boy scouts right here, that is the world’s hope, that’s what you’re telling me?
The days of NASA thinking shit up may have passed.