How do you 'go' in space?

A tour of a space facility in the US apparently prompted Prince Philip to ask how astronauts deal with "natural functions" in space. So how exactly do they go to the toilet (or should that be the loo)?

It's all to do with air flow. On earth, in the West at least, your standard toilet is a water-flush affair, that takes waste and washes it down a pipe.

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