After the urine is collected over a couple of days, it's dumped into space, which is beautiful to watch because the urine freezes into a glitter of ice crystals shimmering in the sun.

If you look at astronauts closely, their eyes look kind of puffy. And it gives you this mild headache. But one of the advantages of that, if you will.

NASA's training philosophy is "no surprises." So what they did is put a simulator on Earth where it looks exactly the same as a shuttle toilet and they put a camera down in the bottom of the opening for solid-waste collection, with a light that basically illuminates your asshole.

The opening for solid waste is very small [in the space ship]. It's not toilet-bowl size. And aim is critical. To be honest with you, you don't know where your asshole is pointing within a small circumference.

In weightlessness, one of the physiological changes is a fluid shift. Your blood and fluid is equally distributed in your body. So that makes your calves and thighs and waist skinnier, and it makes your chest and women's breasts broader. The downside is your face is kind of puffy

The solid waste is returned to Earth with the shuttle. If we [astronauts] ever dump solid waste overboard, it's going to give new meaning to wishing upon a falling star.

And you're headed to a place with no bath and no shower. So you can just imagine how crazy it is to get up there, take your diaper off, have a urine-soaked crotch, and all you can do is wet a washcloth and wipe your skin off. You also have to do it on landing and spacewalks, too. It's not a ride that makes you springtime fresh.