Thursday, July 16, 2009

Weave Me to the Moon

40 years ago today, Apollo 11 lifted off from Kennedy Space Center on its mission to put human beings on the moon. As you might expect, news organizations are digging back into the story of the mission in the run up to the anniversary of the actual landing. Along those lines, the BBC has a fascinating story about a group of ladies who were key to the success of the mission, for a fairly odd reason.

A key to the success of the mission was the Apollo Guidance Computer (APC), the forefather of modern fly-by-wire technology. The APC was a frighteningly powerful piece of equipment for its time, but pales in comparison to the mundane laptop on which I type this (said one designer, it "was tiny compared to the one in your cellphone . . . in every dimension except size."). Reliability was key, especially for something being built when computers occupied entire buildings.

To help achieve that goal, the engineers came up with a brilliant solution:

In order to make sure that the software was robust it was 'woven' into so-called 'rope core memories'.

These used copper wires threaded through or around tiny magnetic cores to produce the ones and zeroes of binary code at the heart of the software.

Pass the copper wire through the core and the computer read it as a one. Pass it around and it was read as a zero.

'Once you get it wired it's not going to change without breaking those wires,' said Mr Hall.

The rope core memories would become know as 'LOL memory' after the 'little old ladies' who knitted together the software at a factory just outside Boston.

These ladies would sit in pairs with a memory unit between them, threading metres and metres of slender copper wires through and around the cores.
Thus, among the many unsung heroes of the mission were the little ol' weaving ladies.

I'm also amused that "LOL" has a history beyond its Internet slang meaning. Heck, I almost laughed out loud about it!

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