Rope memory module for the Model 100 Apollo Guidance and Navigation Computer

This is a rare rope memory module made for the Block I (before the Apollo 1 fire) Model 100 Apollo Guidance and Navigation Computer.  The computers that formed the basis of the Apollo Guidance and Navigation System (AGNS) were at the cutting edge of technology in the 1960s. They were the first to use the integrated circuit technology that subsequently gave us desktop computers and so many of the consumer electronic products that fill our lives today.

Each computer had two types of memory, erasable and fixed. The fixed memory contained the programs, constants and landmark coordinates using 36,864 terms or words, each of 15 bits length. That came to a grand total of 74 kilobytes of memory.

The fixed memory was made from coincident-current ferrite cores woven into a rope with copper wires and sealed in plastic. Software components were encoded into a core according to the "pattern" of its weave. Each core functioned as a small transformer, with up to 64 wires connected to each core. If a wire passed through a particular core, a "1" would be read. If a particular wire bypassed the core, a "0" would be read. If you wanted to change the software contained in fixed memory, you had to rewire the sealed core to change the bits. The erasable memory was made from similar materials but with a different design. Each core in the erasable memory could be changed using magnets. Turning clockwise to indicate a "1" or anti-clockwise indicating a "0".

Here is a video showing how Francois Rautenbach extracted the original software from the rope memory modules of AS 202, the first Saturn V flight and the first computer using integrated circuits.

The module is labeled: C P ASSY 1031103 NO.  1003733-011, MFG BY RAYTHEON CO., SERIAL NO. RAY 4

Thanks to Jim Loocke for the technical description of this artifact.

Comments

[Wilhelm F Zantow]

A fine point--The rope cores were a nickle alloy wound on a steel bobbin not a ferrite. Word selection was achieved first by pulsing all the cores and inhibiting all but the desired core. this generated 196 ones and zeros. Further selection was achieved by forward biasing 16 diodes of the possible 196. Bill Zantow 18/9/09

[David Meerman Scott]

Hi Bill, many thanks for commenting. Did you work on these?

[Jimmie W. Loocke]

Hi Bill,
Just wanted to touch base. You seem to know a lot about the Block 1 rope memories. I have 2 of these in my collection. I am trying to determine why they have a yellow stamp that says " Flight 202 on 6 0f them and "Flight 501' on the remaining ones 1 is not marked . Any Ideas. Thanks Jimmie Loocke