“Roger Tranquility. We copy you on the ground. You got a lot of guys about to turn blue. We’re breathing again.”

45 years ago, the reason everyone at NASA Mission Control were holding their breath was that Neil Armstrong and Buzz Aldrin had just managed to land on the Moon, but had almost run out of gas getting there. When the lunar module finally touched down, it had less than 30-seconds of fuel remaining in its tanks.

As a child, I remember watching the landing as I sat on our living room shag carpet – transfixed – in front of our black and white TV. I too was holding my breath.

A couple of minutes earlier the entire mission had almost been aborted due to a glitch in the on-board Apollo Guidance Computer – the first integrated circuit computer ever built. A “1201 alarm” signalled that the computer was overloaded because it ran out of the memory it needed for its calculations.

How much memory?

Only 4KB of read/write memory and a whopping 32KB of read-only memory.

Think about that for a moment.

45 years ago the most sophisticated computer ever built – the one that was responsible for landing two men on the Moon – had enough memory to store about a one-second audio file!

Fortunately, the computer was designed to reboot itself when an error like this happened. It did, but when it came back on-line it reported yet another error… During the exhaustive training simulations that had taken place before the flight, these sorts of computer errors usually resulted in an aborted landing. But Armstrong chose not to do that and instead, took over manual control of the lunar module – deftly guiding it over the computer-targeted landing spot (which turned out to be a crater filled with “Volkswagen” sized boulders). A gutsy move for someone in a little spacecraft 250,000 miles away from home.

So why did Armstrong elect to continue the landing, despite being perilously low on fuel? In a post-flight debriefing, he summed it up as follows: “We had gone that far and we wanted to land. We didn’t want to practice aborts…”

I still get goose-bumps when I listen to a recording of the flight.

You can watch the final 60 seconds of the landing (as seen through the window of the lunar module) here:



Tranquility Base here, the Eagle has landed