Memories of the Saturn V For a bit of mid-week […]

Memories of the Saturn V

For a bit of mid-week cheer, let me share a *fantastic* techno-archaeologist photo essay Ken did on my core memory module from the LVDC (Launch Vehicle Digital Computer). It holds the flight program for Apollo, guiding the huge Saturn V rocket from launch to low-Earth orbit to trans-lunar injection. This triple-redundant autopilot system saved the Apollo 12 mission when lighting struck the rocket twice early in the launch, knocking out displays and controls for the astronauts.

I love the wrap-around electronics design — not yet a fully planar mindset. The outer wrap consists of timing, drive, inhibit and sensing circuits for the magnetic memory array. Built by IBM for NASA, it is festooned hybrid ceramic modules, not integrated circuits. At this point in 1966, the Apollo program consumed 60% of global semiconductor output. (It was also the year that my dad entered the semiconductor manufacturing business, immigrating to Arizona for a job at Motorola, and that is I why I am a U.S. citizen.)

This module stores 8k x 13 bits + parity in a five-pound block. More interesting still is the ghost in the machine. The little iron rings within still hold whatever program they had when powered down (the magnetic memory does not fade). Since there are no tapes or archives of the code saved anywhere by NASA, it is possible that the only remaining copy of the Saturn V flight program is in cores like this.

Here is Ken’s post (even the footnotes are amazing with comparisons across Apollo computers and IBM commercial computers of the time): http://www.righto.com/2020/03/the-core-memory-inside-saturn-v-rockets.html