The Apollo core rope memory and women's heritage on the Moon

Between 1969 and 1972 there were six Apollo human spaceflight missions to the Moon, each leaving a complex site behind. A common joke now is that the average smart phone has more computing power than an Apollo spacecraft, and while this may be true, that these early computers could take men to the Moon and back is truly astonishing.

Today computing and IT are male-dominated fields, but in the 1960s, it was women - so much so that women were called 'computers'. Why? Programming was considered a menial, repetitive task, suited for the inferior intellectual capacity of women. What this meant, though, was that women were at the forefront of the nascent field of computing before it became prestigious and men edged them out.

A key feature of the Apollo guidance computer was core rope memory, used on all Apollo ascent and command modules. Ken Shirriff explains the technology here.

Prototype of core rope memory
Mark Richards/Computer History Museum

The computer scientist Margaret Hamilton has become famous, especially through the photograph of her standing next to a mountain of code almost taller than her. She was the ultimate 'rope mother', and was responsible for getting the programming right. David Brock explains that the rope mother wasn't actually a gendered title:

The supervisors responsible for overseeing the careful integration of changes and additions to the software were known as “rope mothers,”

regardless of their actual gender identity.

The rope mother’s boss, though, was a woman:

Margaret Hamilton

. Before Apollo, Hamilton worked as a programmer at MIT’s Lincoln Laboratory on the

Semi-Automatic Ground Environment (SAGE) air-defense system. After MIT won the contract to supply the guidance and navigation system for Apollo, Hamilton got a job working on the systems software, and she eventually led the team that created the onboard flight software.

In the video below, you can see women working on many parts of the Apollo guidance computer (of course they are always 'girls'). If you watch carefully, you will see a 'hidden figure' - an African-American worker. At one point, you can see the workroom behind the men talking - note that no women get the chance to speak - full of women wearing a loose sort of shirt over their clothes, and chatting to each other as they go about their delicate and precision work - it's a busy and happy sort of lab!

You can see that women were involved in testing the micrologic units of the Apollo guidance computer and putting all the components together. Clearly it wasn't just the core rope memory, the component that elicits so much excitement. Many parts of the process were automated and the women operated the machines. Some of the women recruited were seamstresses, used to threading.

Core rope memory was not used in the descent modules, which stayed on the lunar surface while the ascent modules took off again to dock with the waiting command module which had been orbiting the Moon all the while. Once the astronauts had all moved into the command module, the ascent module was jettisoned. The command module returned to Earth and the ascent modules crashed onto the surface of the Moon.

• Apollo 11: location unknown

• Apollo 12: 3.94 S, 21.20 W.

• Apollo 14: 3.42 S, 19.67 W

• Apollo 15: 26.39 N, 0.25 E

• Apollo 16: location unknown

• Apollo 17: 19.96 N, 30.50 E.

While the descent modules are intact, the crash location of the ascent modules is a different kind of site, comprising the impact crater, its rays and ejecta, and the material of the modules which are likely to be highly damaged. At those locations, part of the significant fabric is the core rope memory. What does this mean? Well, when the cultural significance (historic, scientific, aesthetic, social, spiritual) of the impact sites is assessed, the presence of this technology gives them extraordinary historic and social significance.

But wait. The story of the core rope memory and Margaret Hamilton is well known now, but didn't we see women working on all aspects of the Apollo guidance computer in the MIT video? I believe we did. So the descent modules also have computer hardware, as well as software, made by women. They are part of the history of space travel and computing, and how women were excluded both from being astronauts and computer scientists. But they're still there, at every Apollo landing site. On the Moon.

I saw part of the Apollo Guidance Computer when I visited Jim Austin's computer sheds near York with archaeologist John Schofield several years ago. At the time I wasn't thinking about this and I wish now I'd realised what a significant piece of women's heritage I was looking at.