#8 -- I once worked with an engineer that had worked in an aircraft factory in WWII. He described the process of doing a stress calculation as:

1. Engineer sets up the problem with the appropriate numbers.
2. Papers are passed to another section that converts all the numbers to logarithms and corresponding necessary addition/subtraction problems.
3. Results checked for accuracy, then are attached to the original papers and passed to a third section.
4. This section is full of women (it was WWII) with mechanical adding machines. Here they did all the adding and subtracting of the logs.
5. Results were checked for accuracy, attached to the paperwork and returned to the previous group.
6. Results were translated back to real numbers from the logs and checked for accuracy.
7. Results were then passed back to the engineer.

This normally took about a week to do unless you had full priority which you "might" get your results in 3 days.

Remember, this is for ONE loop around the design process; if it wasn't strong enough, you got to do it again. Also, there was no "cut-and-paste" for entering the numbers. You had to key in each number every time you wanted to perform a calculation. If the adding machine papertape was lost, you got to do the whole calculation all over again. Imagine trying to optimize something!

Obviously, this process wasn't used for all their calculations. They had their sliderules, hand calculations, and engineering handbooks for quick-and-dirty stuff, but this was the general process for the large critical calculations.

-eef