For those of you looking to sign up for one of those ‘always planned, never quite executed’ missions to Mars, there’s some bad news about radiation exposure while in transit to and from.
Better, more even shielding would improve matters, but only a bit, since 95 percent of the exposure comes from cosmic rays that would pass right through most shields.
“It is clear that the exposure from the cruise phases alone is a large fraction of (and in some cases greater than) currently accepted astronaut career limits.” the authors conclude. For the ESA and Canada, these limits are 1 Sievert; NASA sets its limit as a three percent chance of developing a fatal cancer as a result of exposure. All of that would seem to indicate that any astronauts lucky enough to complete a round-trip journey to Mars would probably find themselves permanently grounded afterwards.
I’m kinda stupid, so don’t laugh when I ask what seems like a simple question… who not create a magnetic field around the ship to shield from cosmic rays and other high energy radiation? Wouldn’t it be more effective and certainly lighter than, I don’t know, two or three thousand pounds of lead foil sandwich?