system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When NASA made the first space suits, how did they know what space would be like? I.e., how did they know what to put on the suits?
gpt
It was theorized to be a vacuum hundreds of years before we went to space. We can also produce vacuum chambers here on earth to design and test such a suit.

Keep in mind we’ve been making pressurized suits for several decades before space flight including for deep sea diving.