1974 · Magnetic-Card Programmable Calculator · Work 945 of 1,871
A training room at the space flight centre in Houston, on a grey steel console a pocket calculator fifteen centimetres tall, its case tapering toward the top, with an olive-bronze frame and a dark brown-black key face, at the top a dark glass window with a faint red glow, two small slide switches, rows of black keys, two yellow-orange keys, one pale blue key and light grey and cream keys, every key plain smooth and unmarked, a hand in a white shirt sleeve sliding a narrow dark magnetic card into the slot under the window, beside it an open white cloth pouch with a hook-and-loop flap, grey consoles with dark screens, fluorescent light.
What it was used for
Hewlett-Packard sold the HP-65 programmable pocket calculator from 1974 for 795 US dollars. The Smithsonian lists its fields of use as science, engineering, finance, statistics, mathematics, navigation, medicine and surveying; it was designed for repeated calculations. Programs of up to 100 steps were written onto narrow iron-oxide magnetic cards of about 7.2 x 1.1 cm and read through a slot below the display; 40 cards came with the machine, 19 of them pre-recorded and 1 for cleaning the head. NASA selected the calculator for the Apollo-Soyuz Test Project flight of 1975: it carried rendezvous and guidance equations and was to take over if the Apollo Guidance Computer failed. The Smithsonian's example was built in Singapore.
What was new
The National Air and Space Museum calls the HP-65 "the first magnetic card programmable handheld scientific calculator". The qualifiers carry the claim: handheld, scientific and magnetic-card programmable was new only in combination. The machine could do what no pocket device had done before: store a user-written program outside the case and reload it at will. The Smithsonian records that Hewlett-Packard staff dubbed it a "personal computer" - a machine with 35 keys and 100 program steps. The barb is in the ratio: a 795-dollar production item flew in 1975 as the fallback for a spacecraft's onboard computer.
What the sources leave open: Price, 100 steps, card count and Singapore manufacture come from the Smithsonian object page; the Apollo-Soyuz role from the National Air and Space Museum object page. NASM says its example may have been retained or acquired by NASA later; the page does not say that this particular unit flew in 1975.