Skip to main content


As many of the famous NASA astronauts start to reach the twilight years of their lives, it is perhaps a shock to realise that it is now almost 50 years since that extraordinary moment when we watched those grainy and slightly ghostly images of Neil Armstrong taking his first steps on the Moon. The lunar module landed six hours earlier on a dark lava flow that resulted in it being called the Sea of Tranquillity by Earth-based Moon-observers.

Buzz Aldrin was the other person in the landing module, while Mike Collins stayed in the Command Module that orbited the Moon, and to which the Lunar Module returned after spending just under an Earth-day on the Moon. The whole team returned to Earth in the 24th July.

Apollo 11 lifting-off on July 16th 1969 from Cape Canaveral


There have been many attempts to rubbish the whole idea that anyone has ever set foot on the Moon, but no-one in a position of responsibility in the long-running NASA Moon-landing project has ever come forward to support such a notion. That having been said, there is no doubt that their achievement is even more astonishing given the relatively primitive computing powers available to NASA at the time.  There were in fact four separate computers, but the one most associated with the landing was the Automatic Guidance Computer – or AGC.  These were advanced bits of kit for their time and only matched in commercial markets when PCs such as the Commodore 64 or ZX Spectrum came long about ten years later. In addition, they did not have to run any fancy graphics or User Interfaces, so were focused entirely on their specific tasks.

One of four computers carried on the Apollo 11 mission: Image NASA

However, the technical statistics still give one pause for thought. The Apollo 11 AGC had 2k of RAM (yes, as in two thousand bytes), and 36 K or ROM. The Apple Iphone 6 has about 488,000 times as much RAM as the AGC; the Iphone has some 3.5 million times as much ROM. Depending upon the application, the Iphone computer is up to 30 million times faster than the AGC. In fact, there is more computing power in one Iphone 6 than the whole of NASA had throughout all of the  Apollo missions. In fact, there is more computing power in a small domestic appliance such as a toaster than was available to any of the Apollo missions.

Would you rather have had a couple of Iphones controlling the mission rather than the AGC? It is tempting to say “Of course!!”, but the old systems had many great advantages, not least being the fact they were designed to be self-recovering in the event of a programming crash. That is not to say they were immune to failure.

The contract for the Apollo computers contained no hard criteria against which to develop a specification so it was a case of working in blind faith that the aim could be achieved. However, by 1966 it was realised that the rocket-based AGC could not cope with all of the tasks of managing and navigating the mission, so a large, ground based computer was used to send data to the rocket’s which used by the AGC for navigation. However, the AGC had to be able to navigate the modules when they went out of signal – as in the dark side of the Moon, and also to land the moon-module to avoid the 1.5 second round-trip delay in signals between the Earth and Moon.

Just as the Moon-lander was making its last descent to the surface, a radar system went on the blink and started to send a mass of error signals to the AGC, overloading it. Instead of crashing, the AGC stopped work on all other problems. switched itself off, and re-started again in a controlled manner. Unlike a PC-crash, all the data had been saved automatically and the restart was near instantaneous. The AGC had done what it was designed to do and the mission was saved.

The other reason that things worked so well in those days was that everyone wore ties!

The Apollo 11 mission team after the lunch in 1966. Wernher von Braun is the chap with the binos.


It is a sobering thought to consider how much was achieved by NASA as well as the faith those Astronauts had in the new technology they had aboard. It makes one realise just how dependent modern weapons systems are upon complex and mind-mindbogglingly fast calculations being made millions of times a second at the press of a button or the wiggle of a joystick etc. What would we do, and where would we be, without the computer in all its various forms?




Comments on On this day in 1969 man walked on the moon

Leave a Reply

Your email address will not be published.Required fields are marked *.

This site uses Akismet to reduce spam. Learn how your comment data is processed.