Kevin Fong is an astrophysicist, astronaut and anaesthetist who gives an incredibly entertaining talk about human space exploration and our dreams of a manned mission to MARS. This is a mission that stands on the boundary between science fiction and science fact. A mission that would be a minimum of 1000 days in length and which would be twice as long as any previous manned space mission.
Fong focuses on the the incredibly destructive effects of such prolonged weightlessness on the human body. He outlines the somewhat predictable effects of this on the muscles and bones, but surprises us with the changes in vestibular balance, linear acceleronomy, baroreceptor calibration and probably most frighteningly the psychological effects of prolonged isolation in space. Despite considerable work in the area of human adaptation for space and the ongoing development of counter-measures these physiological challenges remain largely unsolved.
In essence Fong explains, to overcome the detrimental physiological effects of prolonged weightlessness engineers need to design a craft capeable of generating 1G of gravitational force to mimick earth's gravity. This could require a craft the size of the London EYE rotating four times per minute. Perhaps if this can be achieved, astronauts might arrive at MARS after 30 months in space in a physcial state capeable of allowing them to stand upright and walk from the landing craft.