It’s a bit of a delicate question really, isn’t it?
But one I had to address due to certain scenes in the latest book of the Dreamer Chronicles, Moon Zero.
To explain why would be to spoil the story, so rather than do that, lets cut straight to the point: Astronauts do not have to “hold it”, nor have bizarre tubes leading from their suits at all times (eww!).
Two things people:
1. Giant nappies / diapers (or whatever you call them in your neck of the woods)
2. Cleverly designed toilets with … ahem … vacuum functionality to stop … “things” floating around.
Here’s a snippet I wrote in the Author’s Notes for Moon Zero.
Nappies In Space?
One of the most-asked questions of astronauts is apparently bathroom-related.
Just exactly how do you … ahem … use the little boy’s/girl’s room in zero-gravity, or when you are trapped in a spacesuit?
Obviously any liquids and … other things … need to be contained.
The answer is incredibly simple. They wear nappies (diapers for the Americans). Or more strictly speaking, a “Maximum Absorbency Garment”.
Giant astronaut-sized ones.
However, I’m being a little cheeky, since they only where these when they are involved in a long operation where the usual bathroom facilities are not available. In the ISS (see below), and even in the Space Shuttle, there are toilets, which use suction fittings to avoid any mishaps. The YouTube video shows the type of toilet used – and the special training needed, and the NASA link below has a good summary of “a day in the life of an astronaut”!