Jay Buckey describes well the three chief biomedical problems facing manned missions to Mars.1 Although I find his discussion of the radiation problem too pessimistic, we do need to think carefully about mission design and engineering in overcoming it.
Above all, one needs to shorten the transit time to Mars and therefore study the trade-offs between the cost of extra propulsion versus the obvious gains (from reducing exposure to radiation and zero-G, as well as reducing the complexity and weight of life support). For example, with additional propulsion between Earth and Mars instead of just coasting, the "Speedboat" mission2 would shorten the transit time to 100 days in each direction and permit a stay at or near Mars of 30 days. The total mission duration of less than eight months is well within the time frame of experience with the MIR and ISS space stations.
In-transit shielding against radiation is ...
