Core rope memory

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Core rope memory test sample from the Apollo program.

Core rope memory is a form of read-only memory (ROM) for computers, first used in the 1960s by early NASA Mars space probes and then in the Apollo Guidance Computer (AGC)[1] and programmed by the Massachusetts Institute of Technology (MIT) Instrumentation Lab and built by Raytheon.

Software written by MIT programmers was woven into core rope memory by female workers in factories. Some programmers nicknamed the finished product LOL memory, for Little Old Lady memory.[2]

Memory density[edit]

Rope memory from the Apollo Guidance Computer

By the standards of the time, a relatively large amount of data could be stored in a small installed volume of core rope memory: 72 kilobytes per cubic foot, or roughly 2.5 megabytes per cubic meter. This was about 18 times the amount of magnetic core memory (within two cubic feet).[citation needed]

Data units per cubic foot Data units per cubic meter
Bytes Bits Bytes Bits
Core rope ROM 72 KB 576 Kbit ~2.5 MB ~20 Mbit
Magnetic core RAM 4 KB 32 Kbit ~140 KB ~1 Mbit

Popular culture[edit]

In some moon landing conspiracy theories, confusion between core rope and regular core memory is used to advance the claim that the Apollo mission computer memory system could never have passed through the Earth's magnetic field undisturbed. Regular core memory would likely be susceptible to transiting magnetic fields of this magnitude,[citation needed] whereas core rope is not.


  1. ^ "Software as Hardware: Apollo's Rope Memory". Retrieved 29 Sep 2017.
  2. ^ Directed and Produced by: Duncan Copp, Nick Davidson, Christopher Riley (2008-07-07). "The Navigation Computer". Moon Machines. Episode 3. 22:40 minutes in. Science Channel.

External links[edit]