In my search high and low for evidence of the use of HP calculators in the space program, I found a comment at the bottom of this page about the HP-55. Not much to go by:

I still have my HP-55 from my days with NASA. It is no longer operable due to inability to locate the 82001A battery pack. I also no longer have the external power adapter; but I’m still looking.

HP-55

HP-55

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