The longest time spent under water is what, maybe a month or two for those on nuclear submarines? Which is probably 25% the length of one leg of the mars trip?

The longest time spent under water is what, maybe a month or two for those on nuclear submarines? Which is probably 25% the length of one leg of the mars trip? And subs can always just surface and call for help for 99% or problems they’d face? Just fantastical thinking that we’ll make any headway on that trip in the next 50 years.