Design does not happen in one step

Design happens between these extremes. There is an element of diving-in when one begins a design. The territory is new. Exploration is needed. Discovery of possibilities must take place before one can weigh them. Sometimes a quick approximation of a real design happens, and this is a good thing because it informs the designer that the intent is achievable. Progress is evaluated and new avenues considered. It is what Hagel calls the 'dialectic' -- an idea is tried, practical experience comes along to challenge it, and then a new idea or proposal is synthesized and this cycle continues.

During the development of the American Apollo lunar lander, there were more than one million documented design changes -- screws, bolts, shock absorbing materials, hand-rail mounts, sunlight shielding, fuel tanks, navigation systems, propulsion, landing radar, communications -- everything in the machine was designed and re-designed and re-designed again. At several points along the way the whole concept even had to be scrapped and reworked from nearly the beginning. But eventually the Lunar Module design was completed (at about the same time as the first machines themselves) and eight copies flew in space with almost no equipment failures of any kind even though, at the time, it was the most technically sophisticated machine ever built.