Are there rules for what you can and cannot wear in space? Is it possible to flaunt good fashion even in a spaceship? Well, the short answer to that is, yes, it is very much within the bounds of the possibility to wear regular clothes in space.
It’s really not very surprising when you look into how a space station is designed to accommodate astronauts. Inside the spacecraft, the pressure is kept at about 1 atm. This is the same as the pressure on Earth. All environmental factors such as temperature and humidity are controlled so that the astronauts can live comfortably. The spacecraft is properly sealed on all ends to maintain these conditions. So, while the astronauts are inside the spaceship, they are free to wear any of the regular clothes they have been allowed to bring with them. It is only when they are outside, do they have to wear space suits for protection.
NASA actually does a lot of research on what kind of clothes are appropriate to bring to space. From shoes to underwear, they are very thorough in their studies for space-appropriate attire. Aside from flight suits, trousers, sleep shorts, soft slippers, underwear, knit shirts, and lined zipper jackets are included in an Astronaut’s space wardrobe. The clothes that astronauts bring with them are usually commercially available lightweight clothes, with some exceptions.
Outside, of course, is space. So understandably, protection is needed. Astronauts wear the extravehicular mobility unit or EMU suits when going out. It’s designed to be more comfortable, flexible, and durable than any previous spacesuit. It includes gloves, upper torso, lower torso, and arms; all manufactured to fit men and women astronauts perfectly. They are assembled on the spot and come with many interchangeable parts. Unlike previous suits, these space suits are not custom fitted for each astronaut, making them a more reusable and cost-effective spacesuit option.
Cotton clothes are avoided because the possibility of lint developing on them can be hazardous. Clothes that are not flame retardant are not taken to space because any chance of a fire occurring has to be canceled out.
Unfortunately, there is no possibility of doing laundry in space just yet. This is why astronauts are encouraged to pack sufficient clothes and underwear to last them about three months. That makes 99 to 100 sets of underwear! Shirts and trousers are usually re-worn a lot. A space station gets resupplied around every three months, which is when the fresh supply of laundry comes in.
Thus, although it is okay to wear regular inflammable clothes inside a space station (with some exceptions, of course), astronauts need to gear up in space suits and be properly protected when venturing outside into space.