While doing research on the internet, I occasionally come across some interesting, engineering related trivia. When I do, I like to pass this on to my colleagues and clients. The following is an example:
Did you know that a major design feature in the space shuttle - the world's most advanced transportation system - was determined over two thousand years ago by the width of a horses backside.
When we see a space shuttle sitting on it's launch pad, there are two solid rocket boosters, or SBR's attached to the side of the main fuel tank. These SBR's are were by Thiokol at their factory in Utah. The engineers who designed the SBR's would have preferred to make them fatter, but the SBR's had to be shipped by train to the launch site. The railroad line from the factory had to run through a tunnel in the mountains. The tunnel is slightly wider than the railroad tracks.
The U.S. standard railroad gauge (distance between the rails) is 4 feet, 8.5 inches. Why was that gauge used?
Because that's the way they built them in England, and the U.S. railroads were built by English expatriates. Why did the English build them that way? Because the first rail lines were built by the same people who built the pre-railway tramways, and that's 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.
The wagons used that spacing because that was the spacing of the existing wheel ruts in the roads and using any other spacing would cause the wagon wheels to break off on some of the old, long distance roads.
These roads were built by the Roman empire, and the ruts in the road which everyone had to match for fear of destroying their wagon wheels, were made by Roman war chariots. The specifications for the wheel spacing on the Roman chariots was 4 feet, 8.5 inches, which is slightly wider than the width of two horses rumps.
So you see, that the design of the solid rocket boosters was determined over two thousand years ago, by the width of two horses backsides.