My dad used to work on the Apollo space program. He has any number of stories, all of them funny. Some of them may actually be true. Here's one of them:

The Apollo program, really the entire space program in the 1960s, was in such a godawful rush to get things done that it essentially ran on a "war footing". What this meant was that instead of designing, building, testing, and finishing item A, then designing building, testing, and finishing item B, then C, then D, you basically built A, B, C, and D all at the same time and then put it all together at the end and tested it as one unit. The bonus was you got it all done in a fraction of the time. The risk was you had to be extremely careful about it, because you didn't get to test anything until it was all done.

As this photograph shows, two of the things that were being built at the same time were the mobile launchers (on the right of the photo) and the Vehicle Assembly Building (VAB, on the left). The mobile launchers were to be carted into the VAB by the crawlers, the Saturn V rocket would be assembled in the building, and then the whole thing would get rolled out to the pad.

Now, the program's tolerances, even on stuff this big, were always measured in fractions of an inch. It didn't take much of a margin of error to really screw things up. Making sure everything fit together was a real challenge, and a lot of times things didn't, at least at first. It was such a problem that NASA had ordered a Saturn V with no intention of flying it... they would just use it to make sure absolutely everything fit together (called a "boilerplate").

As the mobile launchers and VAB began to near completion, a few people started to get nervous. Nobody knew if the one would actually fit inside the other. And it could be really expensive if they didn't.

Today we'd use all kinds of whiz-bang laser guided measurement widgets and get all the dimensions down to a tenth of a millimeter. They didn't have anything like that, and while they had all the money in the world, they didn't have the time to invent it. Instead, they sent a guy up to the top of the mobile launcher with a big coil of rope, the yellow nylon kind you can pick up at pretty much any hardware store to this day. Before making the climb, knots were tied in the rope, at first every 50 feet, then every 25 feet, then every 10 feet, and then every foot when they knew they were getting close to the proper length.

Of course they knew about how tall it was all supposed to be, so the guy had roughly enough rope handy. The big problem, 380 feet + (115 m +) in the air, was wind. Every time he tried to lower the rope, the wind would blow it sideways. Can’t get a good measurement that way. So, being a self-starting gung-ho NASA type, he tied a roughly 5 lb (2.2 Kg) weight on the end. No good, wind still blew it sideways. Well, how about 10 lbs? Nope. 15? That’s better, but not quite. 25? There ya go. 25 lbs (11.3 Kg) was heavy enough that the rope stayed nice and straight even in the wind.

So the guy slowly lowered the now properly weighted rope from the top of the burnt-orange umbilical tower to the top surface of the launcher. Simply counting the knots was all that was needed to get a really good measurement. They already knew the heights of the other parts of the system, so the rest was just addition. And, sure enough, they had a good five, six feet to spare.

What nobody seemed to realize was something obvious to any second grader... rope stretches. When you're dealing with lengths less than 10 feet, it doesn't stretch very much, say only a few inches even when you pull it really hard. But with that much weight on the bottom of a measuring rope dropped over that great a span, it really added up.

And so the big day arrived. Getting a mobile launcher wheeled into the VAB was a major milestone in the program, and quite something to see. Lots of people gathered round, press folks, NASA bigwigs, contractor presidents, etc. But, as the crawler began to inch closer and closer to the door of the VAB, it became increasingly obvious that something was very wrong. Things happened slowly enough that a collision didn't actually occur, but the entire show was stopped within feet of the VAB entrance.

The mobile launcher was two feet too tall to fit inside the building.

Now, two feet isn't that much, but it would've been plenty enough to make lots of horrible grinding and crashing noises as the umbilical tower played a slow-motion game of chicken with the top of the VAB entrance door. If nothing else a really nice "blong" noise would've been heard as the thing hit the roof of the building. Instead of risking it, NASA made a big deal about how awesome it was and gee doesn't it look keen and as a special favor to you folks we'll just wait and let you take all the pictures you want and gosh look at the time seems like your passes have all expired time to go home seeya buh-bye!

It was only after a great deal of swearing, finger-pointing, jacking, cutting, and welding that the mobile launcher managed to safely make it inside the building.

At 2 a.m. the next morning.