PLA (the most common hobbyist plastic used) isn't all that good for functional stuff. It's extremely easy to print with, which is why it's used most commonly, b

PLA (the most common hobbyist plastic used) isn't all that good for functional stuff. It's extremely easy to print with, which is why it's used most commonly, but as you said it has a small temperature range where it's usable, it breaks down quickly under UV radiation, it gets pretty brittle, and it doesn't hold it's shape over repeated stress. I don't think it would "crack instantly" or melt in space right away, but it wouldn't work long term at all. But if you just go outside of that most basic plastic, there are tons of other options. Printing with PETG is just as simple in many cases, but it can withstand higher temperatures and is pretty easy to make watertight seals with. ABS is a great plastic that is also easy to print with once you learn the quirks. It is used a lot in automotive stuff since it's fairly resistant to a lot of temperatures and is pretty hard. Polycarbonate (PC) is also a great plastic to print with if you need it to withstand a lot of work and different temperatures. All of those can be printed on hobbyist machines, and I have all of them in the room next to me. And both PLA and ABS have been used on the space station and tools that the ISS 3d printer has printed have been used in space walks! It's pretty exciting stuff, and while what NASA is using is obviously more advanced than a $300 3d printer you can get online today, it's still using a lot of the same stuff and is pretty close to what you or I could print in our house if we wanted to.