The main reason is that water is an incredibly precious resource in space. So valuable that even urine cannot be thrown away.

Bag an $11 saving on Lego Creator 3-in-1 Space Astronaut, which can also be turned into a dog or a space shuttle. One of our favorite Lego sets of last year is currently on sale thanks to Amazon.

This also applies to something most people take for granted—doing laundry. So, how do astronauts get their clothes clean during missions? Call it a dirty secret: They don’t. Instead ...