They compromised. The probability of getting the crew back safely was set at three nines, or 999 times in 1,000. The probability of completing the assigned mission was set at two nines, 99 times in 100. And that, Johnson recalled, is how it happened, in a ten-minute conversation. “We wrote those numbers down, and they had a most profound effect on the cost of the program. If you took one decimal point off of that thing, in theory you could probably cut the program cost in half. If we’d added one more, there’s no way in the world we could ever have done it —there’s not enough money in the world
...more
