Der folgende Artikel stammt aus den HP-65 Users‘ News (Volume 1, Number 2). Darin wird beschrieben, wie der HP-65 Taschenrechner beim Apollo/Sojus Rendezvous im Juli 1975 für Berechnungen von Kurskorrekturen kurz vor dem Andocken sowie zur präzisen Ausrichtung der Funkantenne benutzt wurde. Bei einem Ausfall des Apollo Bordcomputers wäre der HP-65 das einzige Hilfsgerät für Kursberechnungen gewesen, solange sich das Raumschiff im Funkschatten der Bodenstation befunden hätte.

HP-65 in Space Rendez-Vous

An HP-65 programmable pocket calculator — just like the one you own — played an important role in the historic Apollo/Soyuz July 1975 space rendez-vous.

The calculator was used to calculate two critical mid-course correction manoeuvres just prior to the link-up between the U.S. Apollo and the Russian Soyuz spacecraft. These manoeuvres took place 12 and 24 minutes after terminal phase initiation (i.e. the closing stages of the flight before rendez-vous).

It was also used as a back-up for Apollo’s onboard computer during the final lining up prior to rendezvous and docking. Here, the first job concerned the coelliptic manoeuvre (putting both spacecrafts into identical orbits) when the vehicles came within approximately 100 miles of each other. The second task covered the terminal phase initiation calculations when Apollo was 22 miles from Soyuz. In both instances, the HP-65’s answers to the problems were compared with those of the onboard computer.

Had the onboard computer failed, however, the HP-65 remained the only available source for calculating the mid-course manoeuvres because — at that phase of the mission — the spacecraft was not in communication with ground stations. A third set of calculations performed by the HP-65 enabled the astronauts to point Apollo’s high-gain antenna precisely at an orbiting satellite to optimize communications with Earth.

NASA scientists wrote programs of up to 1,000 steps and recorded them on magnetic cards for the astronauts to feed into the HP-65 to perform the critical calculations automatically during flight.

Two HP-65’s were taken on the space trip, along with four sets of programs and six spare battery packs. This is not the first HP pocket calculator to go in space: an earlier model, the HP-35, earned its space wings on the Skylab missions.

A NASA technician (centre) and colleagues from McDonnelI Douglas Corporation working on the HP-65 calculator carried aboard the Apollo Command Module during the recent Apollo/Soyuz link-up project. The 10-day mission tested a common docking system and performed joint experiments between American and Russian crew members. (NASA photo)