Radiation Tradeoffs for Mars

Radiation is the ultimate limiting factor in human space flight. It has been the elephant in the spacecraft since the 1960s, when it first became clear that tiny particles rather than micrometeoroids were the high-speed threat to worry about in space, and it sets bounds on what parts of the Solar System are reachable by human explorers riding chemical rockets.Mars is near the limit of where human beings can go on a small spacecraft. In a sense, it’s bad luck that Nature tempted us with a barely livable planet close enough to reach with rudimentary technology. If not for Mars, the next step for human spaceflight would be finding ways to build spaceships the size of ocean liners instead of trying to fly people around in a space Prius, and then we could go explore more interesting destinations in the Solar System. But you go to space with the planets you’re dealt.Traditionally, the chief strategies for dealing with radiation risk in Mars planning have been optimism and denial. Optimists…