Comment Re:The bases have to be built from local material (Score 2) 46
Radiation levels as recorded by Curiosity on the trip were only double that of either LEO or Mars, while definitely not good even without additional shielding you're probably not looking at too much additional cancer risk. Putting significant amounts of radiation shielding around one small area of the craft where the crew is likely to spend most of their time (the cockpit, sleeping quarters?) would easily bring the trip exposure levels down to something a little more reasonable. With ZERO additional shielding (assuming of course they weren't hit by a solar storm) on a round trip to Mars of over 2 and a quarter years Astronauts would only be exposed to 1.01 seiverts (1 sievert lifetime spaceflight exposure is considered acceptable). By far most of that exposure as you noted is from the trip but with even the simplest radiation mitigation measures on Mars (piling dirt on living/sleeping quarters) and a solar storm shelter you could keep your exposure below 1 sievert and stay on Mars for many years. Though without heavy shielding on the transport multiple trips back and fourth for an individual would of course be very risky.