Tuesday, July 21, 2009

How They Built Apollo 11's Software

Wow. Full story here. You can also run a simulation of the Apollo computers here.

An excerpt from the story:

During the Apollo 11 Lunar Module’s descent to the Moon 40 years ago today, Garman played a direct role in preventing a mission abort. Several warning lights and computer overload alarms came on as the craft descended just above the Moon’s surface, causing worry in Mission Control, but all of Garman’s pre-flight simulation experiences told him that the alarms were not critical and the landing could continue. Without hesitating, and without panicking, the 24-year-old NASA computer engineer confidently gave the “go” to continue the mission.

Granville Paules, was a 32-year-old guidance officer for one of the Apollo 11 mission teams and remembers that moment well.

“The alarms went off on during descent,” Paules said. “It was a conflict between the on-board systems and the computer was starting to get overloaded. Garman had a simulation where a similar thing had occurred about three weeks before that, so he knew what to do. It probably would have been a lot scarier, possibly even an abort for the landing, if we had not had that simulation. I can say that the odds of aborting that lunar landing were a lot higher than people want to believe. That simulation gave everybody the confidence to turn off the alarm and ignore it.”

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