NASA HP-41 Flight Procedures Handbook

[jonmoore]

Whether the 41 was actually used or not isn't the pertinent point here. The fact NASA felt the 41 could be used as part of a backup plan (and created a portfolio of suitable programs) is reason enough to prove that those classic HP calculator ads were more than clever marketing on HP's part.

BTW, that HP in space blog is probably my favourite HP related blog from over the years. It's something I return to time and time again - so many tasty nuggets of calculator lore to be found amongst its posts.