I don't know how NASA did it, but in the 60s and 70s the IBM Selectric typewriters had those replaceable balls and you could swap one in with special math symbo

I don't know how NASA did it, but in the 60s and 70s the IBM Selectric typewriters had those replaceable balls and you could swap one in with special math symbols on it. https://www.duxburysystems.org/downloads/library/texas/apple/cnthesis/selectric.htm https://www.duxburysystems.org/downloads/library/texas/apple... https://mathoverflow.net/questions/19930/writing-papers-in-pre-latex-era https://mathoverflow.net/questions/19930/writing-papers-in-p...