At the risk of being crude, but in the interest of trying to solve a problem cheaply and practically, could not the astronauts simply "go" in a bag, seal it up, and when enough are collected (in an air- and smell-tight larger bag, of course), be chucked out the airlock?

If this is possible, then why worry about a complex, expensive, and limited system? I would hate to see that device slow up or stop an otherwise intriquing plan - oh to see Gemini land on the Moon :^).

Please don't tell me that a few bags of stinky stuff is going to pollute interplanetary space, and this is assuming they don't just dump it into Earth's atmosphere to burn up if they can store it for most of the trip. Just what did the Apollo astronauts do with their waste?

Thinking of the far future, space archaeologists might enjoy finding a bag of human waste from the Second Golden Age of Lunar Exploration. They could learn a lot from it. And if you think I am kidding, just ask a paleontologist how valuable finding dinosaur poo is for learning about those big ol' thunder lizards.

Certainly this is hardly the glamorous part of manned space exploration, but the reality is it cannot be ignored as is usually done in science fiction. And I won't say anything about this being another reason why machines can explore space more efficiently.