Millionaire and space enthusiast Dennis Tito surprised the world with his announcement that he plans to fund a couple’s expedition to Mars. Apparently, the trip is planned to take place in 2018 during a conjunction of our planet with Mars, will take 501 days, and will involve sending a married couple in a capsule roughly the size of a Winnebago. But as time goes on, more news is trickling out of the “Inspiration Mars” program, and some of it is raising eyebrows.

For example, there’s the news that the Mars capsule will involve a rather interesting form of radiation shielding… made of feces. You read that right, the capsule will contain shielding composed of human feces (among other things) that will shield the couple inside from harmful cosmic radiation. But before people begin visualizing some ugly, creepy concoction, let me assure them that this concept is not as unusual as it sounds.

When it comes right down to it, this is the greatest health threat the people who go will face, followed shortly thereafter by muscle atrophy, boredom and cramped conditions. And rather than line the capsule with expensive and heavy metals, such as lead, the engineers designing the Inspiration Mars capsule thought they might kill two birds with one stone.

According to Taber MacCallum, co-founder and CEO of the Paragon Space Development Corporation and member of the Inspiration Mars team, explained that the idea had to do with waste recycling and storage. Since the couple will be eating, drinking and defecating within the capsule for a full 501 days, the waste has to go somewhere.

The proposed solution? Put it in the walls, along with food and liquid waste, and then desiccate it all to recycle the water. Or, as MacCallum put it:

It’s a little queasy sounding, but there’s no place for that material to go, and it makes great radiation shielding… Dehydrate them as much as possible, because we need to get the water back. Those solid waste products get put into a bag, put right back against the wall.

But to be fair, this proposal is not exactly new. In fact, the idea was mentioned back in 2011 by Michael Flynn, a life support engineer at NASA Ames Research Center, who proposed using urine and feces to shield space stations. Packing for Mars author Mary Roach The Geek’s Guide to the Galaxyalso mentioned it in a 2011 edition of The Geek’s Guide to the Galaxy. NASA’s Innovative Advanced Concepts program is also working out the nuts and bolts of this concept under the name of “Water Walls Architecture”.

Water, MacCallum explained, is the key ingredient here, since it serves as a better radiation shield than metal. It’s the nuclei of atoms that block the radiation you see, and water contains more atoms (and therefore more nuclei) per volume than metal does. Food and waste also provide good radiation shielding, and because the food blocks rather than absorbs the radiation, it will remain safe to eat.

Naturally, McCallum was sure to note that they are still working out some of the logistical problems. For one, they still need to figure out how best to keep the Mars-bound couple from experiencing too many nasty sights and smells on their journey.

Gotta admit, this isn’t something you think about when you hear the word “space travel” do you? But then again, you have to account for things like this. Until people can survive without consuming food and water, and expelling waste, long-term space missions will have to figure out what to do about all the dirty, ugly business people get into!

Sources: newscientist.com, IO9