Mirari

So I’m writting lecture today for Fluid Dynamics class tomorrow and I decide to do a problem based on the space shuttle. Specifically, what is the velocity of the space shuttle as a function of time *after* it jetisons it’s solid rocket boosters.

What I found out while researching this is that the space shuttle actually slows down after it loses its solid rocket bosters because it is to heavy for its main engines (those three big cones sticking out the back). !!! is what you should be saying. Putting a shuttle into orbit is all about speeding it up fast enough speed, so why would you possibly slow down if you didn’t have too?

Here is where things get interesting. Solid rocket boosters burn from the inside out along the entire interiour. Increasing the length of the booster then is a way of increasing the thrust. Increasing the diameter would increase, then, the length of time that the booster burns for. So then it would seem that an easy fix to the problem would be to make the solid rocket booster wider. Then the solid rocket booster would burn long enough that when they are jetisoned the shuttle will be light enough it won’t slow down.

But, of course, that isn’t the case so why? Well, it turns out that the solid rocket booste segments are manufactured in Utah of all places and have to be shipped to Florida by rail. The rail lines pass through the mountains using tunnels. These tunnels were bored long ago and are only just wide enough for trains of standard gauge. The solid rocket booster segments then must fit through these tunnels, effectively limiting their size. Since their size is limited, the duration over which they can burn is limited.

!!! Seriously !!! Well, maybe. I don’t really know, but the pieces all fit together. The best part of all this is though that the width of rail road tracks was set over 2000 years ago in Rome. Roman chariots would wear grooves into their roads and anyone who wanted to use those roads would have to make sure their axels were the same width or risk breaking them. Even after the Roman empire fell, anyone wishing to use the roads still had to make their axels the same width. Old habits die hard and our rail road tracks are evidence of this.

So: Rome set a standard width for their chariots, rail roads adopted this out of conviniece, a company in Utah wins a contract to build solid rocket boosters for the new space shuttle, NASA engineers discover a limit to the size of the solid rocket boosters, and the space shuttle has to slow down for a bit durring it’s accent towards space.

PS Mickey asked a really good question, “Why not carry less fuel so the space shuttle is light enough when the solid rocket boosters are let go?” The reason is that while you can’t make the boosters last longer, you can make them stronger. So, you make it so that the shuttle is too heavy for 10 seconds or so. Durring this time, you still gain height, which is good, even though you are slowing down. Plus, you are getting as much fuel as possible going as fast as possible.