Mars trip to use astronaut poo as radiation shield NewScientist

The man and woman aboard the Inspiration Mars mission set to fly-by the Red Planet in 2018 will face cramped conditions, muscle atrophy and potential boredom. But their greatest health risk comes from exposure to the radiation from cosmic rays. The solution? Line the spacecraft’s walls with water, food and their own feces.
“It’s a little queasy sounding, but there’s no place for that material to go, and it makes great radiation shielding,” says Taber MacCallum, a member of the team funded by multimillionaire Dennis Tito, who announced the audacious plan earlier this week.
McCallum told New Scientist that solid and liquid human waste products would get put into bags and used as a radiation shield – as well as being dehydrated so that any water can be recycled for drinking. “Dehydrate them as much as possible, because we need to get the water back,” he said. “Those solid waste products get put into a bag, put right back against the wall.”