There is no washing machine in space. Water is heavy and therefore expensive to take on a 250-mile journey above Earth. That pretty much means what you think it does — astronauts have to wear the same clothes, including underwear, for several days in a row before they can put on a clean outfit.
So how does one pack for space?
NASA instructor and engineer Robert Frost provides some insight in a response on Quora.
Here’s the packing list:
1 pair of shoes for the treadmill
1 pair of shoes for the bike
1 pair of exercise shorts for every 3 days of exercise
1 T-shirt for every 3 days of exercise
1 work shirt for every 10 days
1 T-shirt for under the workshirt for every 10 days
1 pair work pants/shorts for every 10 days
1 pair underwear for every 2 days
1 pair socks for every 2 days
2 pairs Russian overalls (optional)
This doesn’t include the spacesuit that astronauts wear during launch and landing, and when working outside.
NASA points out that because astronauts live in temperature-controlled environments and don’t go outside except when wearing their spacesuit, clothes don’t get as dirty as they do on Earth.
Most of the clothing brought to the space station doesn’t come back home. Dirty clothes are placed in a bag and most of it is put on a resupply vehicle that makes a one-way trip to the space station several times a year. The Progress cargo capsules then burn up in the Earth’s atmosphere.
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