5 Whys - A Tale of Measures

Asking "why" is fundamental to process improvement and is mentioned in 6sigma process review as well as ITIL's root cause analysis (RCAs). Here is an interesting illustration of where asking "why?" can lead you:

When you see a Space Shuttle sitting on its launch pad, there are two big booster rockets attached to the sides of the main fuel tank. These are solid rocket boosters, or SRBs. Thiokol at their factory in Utah makes the SRBs. The engineers who designed the SRBs would have preferred to make them a bit fatter, but the SRBs had to be shipped by train from the factory to the launch site. The railroad line from the factory happens to run through a tunnel in the mountains. The SRBs had to fit through that tunnel. The tunnel is slightly wider than the railroad track. The US standard railroad gauge (the distance between the rails) is 4 feet, 8.5 inches, when you would expect it to be perhaps 4 or 5 feet - in other words a multiple of the measuring system of that time and place. When the railroads were built, the engineers used feet. So why was that rather odd measurement used? Because that is the way they built them in England, and English expatriates built the US Railroads. Why did the English build them like that? Because the first rail lines were built by the same people who built the pre-railroad tramways, and that is the gauge they used. Why did “they” use that gauge? Because the people who built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing. Why did the wagons have that particular odd wheel spacing? Well, if they tried to use any other spacing, the wagon wheels would break on some of the old, long distance roads in England, because that’s the spacing of the wheel ruts. So who built those old rutted roads? Imperial Rome built the first long distance roads in Europe (and England) for their legions. The roads have been used ever since. And the ruts in the roads? Roman war chariots formed the initial ruts, which everyone else had to match for fear of destroying their wagon wheels. Since the chariots were made for Imperial Rome, they were alike in the matter of wheel spacing. Carts and wagons through the ages still had to conform to the same wheel spacing – the ruts in the road ever-deepening. As this popular tale ends, the roman War Chariot was designed the width that it was to accommodate two horses with which to pull it.

Therefore, a major Space Shuttle design feature of what is arguably the worlds most advanced transportation system was determined over two thousand years ago by the width of a horse’s arse.