A random thought just occurred to me: in 2001: A Space Odyssey, the pods have prominent "caution: explosive bolts" signs on the back, and
Dave Bowman uses these to re-enter Discovery without his helmet.
My question is, what is the in-universe purpose of this system? The hatches on the Apollo Mercury capsules had explosive bolts, I guess in order to ensure they could be opened after re-entry and splashdown. But the pods in 2001 are clearly not designed for re-entry, so the explosive bolts on their hatches must serve a different purpose.
Is anything known about the bolts' intended purpose? (It's not mentioned in the script but perhaps was mentioned in interviews/the book/script drafts etc.)