Shuttle Design Criteria: Width of Horse's Ass

When we see a space shuttle sitting on the launch pad, there are two
big booster rockets attached to the sides of the main fuel tank.
These are the solid rocket boosters, or SRB's. The SRB's are made by
Thiokol at a factory in Utah. The engineers who designed the SRB's
might have preferred to make them a bit fatter, but the SRB's had to
be shipped by train from the factory to the launch site.

The railroad line to the factory runs through a tunnel in the
mountains. The SRB's had to fit through that tunnel. The tunnel is
slightly wider than a railroad track,and the US standard railroad
gauge (the distance between the rails) is 4 feet, 8.5 inches. That's
an exceedingly odd number.

Why was that gauge used? Because that's the way they built them in
England, and the US railroads were built by English expatriates.
Why did the English people build them like that? Because the first
rail lines were built by the same people who built the pre-railroad
tramways, and that's the gauge they used.

Why did "they" use that gauge then? Because the people who built the
tramways used the same jigs and tools that they used for building
wagons, which used that wheel spacing.

Okay! Why did the wagons use that odd wheel spacing? Well, if they
tried to use any other spacing, the wagons would break on some of
the old, long distance roads, because that's the spacing of the old
wheel ruts.

So who built these old rutted roads? The first long distance roads in
Europe were built by Imperial Rome for the benefit of their legions.
The roads have been used ever since.

And the ruts? The initial ruts, which everyone else had to match for
fear of destroying their wagons, were first made by Roman war
chariots. Since the chariots were made for or by Imperial Rome they
were all alike in the matter of wheel spacing, thus, we have the
answer to the original question.

The United States standard railroad gauge of 4 feet, 8.5 inches
derives from the original specification for an Imperial Roman army
war chariot. Specs and bureaucracies live forever. So, the next time
you are handed a specification and wonder what horse's ass came up
with it, you may be exactly right, because the Imperial Roman
chariots were made to be just wide enough to accommodate the back-
ends of two war horses.

So a major design feature of the shuttle, which is arguably
the world's most advanced transportation system, was determined by
the width of a horse's ass.

TangoMan