There must be a mistake there somewhere. In a Mars-direct style of mission (the current nasa reference mission), a crew would spend 6 months in space each way a

There must be a mistake there somewhere. In a Mars-direct style of mission (the current nasa reference mission), a crew would spend 6 months in space each way and 18 months on the surface. http://www.marssociety.org/home/about/faq http://www.marssociety.org/home/about/faq The danger of radiation is seriously overstated. Technically there is not much missing except a political will to go ahead with it.