Occam's Razor Examples Part 2: The Jet Engine

Part two: Occam's Razor and the jet engine

Part one of this two part series focused on the idea that some of the central tenants of the "simple is better" mantra are not always correct. Part two will hopefully get back to the heart of why Occam's Razor is an inappropriate way of deciding what technology is "good" or "bad". Through the post we will look at a technology that today, is the standard to wich all new energy technologies are compared against: the jet engine. Weather it is used for propulsion (jet engine) and energy production (natural gas turbine), the well understood simplicity of this technology makes it a tempting target to compare new systems against. 

If you are a thermal engineer (and who isn't), you are probably very familiar with the Brayton Cycle and the idea of the jet engine. If you are not a thermal engineer (and who is) then you may only be casually familiar with them. They are, in simple terms, the things that propel airplanes. They do this by first compressing a gas, heating it up by burning kerosene, extracting some of the energy to run the compressor and then letting the remaining hot high pressure gas shoot out the back through a nozzle. If you have never read through the entire jet engine wikipedia page then you are in for a real treat. 

Today jet engine technology is used not only to provide power for nearly all commercial air traffic, but it also provides 20% of our electrical energy via natural gas plants. In other words, this technology has been a great success. It has transformed the way we produce energy both in the air and on the ground.  Today, the simplicity of the system is well understood: air is compressed, fuel is burned, exhaust is expanded, exhaust is expelled. The straight shot, once through, one major moving part construction of modern turbines is especially compelling. It is tempting to use this technology as an example the power of Occam's Razor. It would appear that the simplest technology has won.  However, the history of the technology tells a very different and compelling story.

Occam's Razor Examples Part 1: The Automobile

Recently I was talking with my good friend, when they made the mistake of bringing up Occam’s Razor. After 30 minutes of rousing debate, we arrived at two concrete examples that we both thought proved our argument. In the interest of friendship and the sanity of the folks sitting around us at the coffee shop, we decided to agree to disagree. However, I think they are both so interesting, that I decided, with the permission of my friend, to write up a two part post about both examples. Here is part one:

Part one: Occam’s razor and the automobile

One of the key tenants of the social construct we call occam’s razor is that simpler systems will have better reliability then complex ones. This seems obvious as more complex systems will have more points of failure and therefore, will fail more often. This self explanatory belief is what drives many of the incantations of Occam’s razor during pitches and brainstorms. “The reliability of that system is going to be terrible because its too complex”.

In previous posts I have tried to show how any incantation of Occam’s razor is flawed and destructive. I wont dwell more on the irrationality of Occam’s razor here. Instead, I want to analyze the relationship between complexity and reliability. Can we always fall back on the idea that apparent complexity leads to more failures? In short, no. In fact, when it comes to technology many systems with higher levels of complexity have better reliability. The changes in automobiles over the past 20 years can help us.