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.

Although the first jet engine powered military aircraft were flown by the germans during world war II, the jet engine was invented and patented by 23 year old British RAF officer Frank Whittle in 1930. As an officer with a history of academic and flying skill, you would think that developing his new,  simpler, technology would have been straight forward. It was anything but. 

Whittle first tried to get the air ministry interested in technology. Like all our government funding panels still do today, the air ministry made the mistake of asking an expert weather the technology was worth pursuing. Like actors in a scripted play, the expert delayed for a year, and then wrote back that the idea was "impractical". The air ministry, putting its full trust in experts, abandoned the idea of the jet engine in 1930. (coincidentally, the german engineer responsible for developing their jet engines has been known to say that if the british air ministry had developed the technology then, world war II would have been completely avoided due to british air superiority)

Whittle continued to try to develop his technology and over the next 10 years he: was forced to let his patent lapse due to lack of funding, raised a small amount of money and founded Power Jets Ltd., failed again and again to get the attention and funding of the government, started using stimulants to work longer days, and watched the initial funders of Power Jets Ltd. default on payments and return their shares. 

Finally, in 1939, Whittle had a working prototype and got the buy-in of the air ministry. This was by no means a sign that the development troubles were over. In fact, before the gas turbine would become a commercial success, Whittle would suffer two nervous breakdowns due to the stress of convincing people to keep developing his technology.

How could a technology that seems to conform so well to the ideas behind Occam's Razor, have been so hard for the decision makers of the day to understand? There are many reasons why this could have been the case, however, I want to highlight two interesting reasons: 1) the decision makers put a lot of faith in technical experts, and 2) the decision makers of the day did not fairly compare the new technology against the technology of the day. Having already talked about the value of experts, lets focus on number 2. 

We can't be sure what the decision makers were thinking at the time, but clearly, there was not consensus that Whittle's invention was the breakthrough it turned out to be. Even more clearly, nobody at the time viewed the technology as the simplest way to power aircrafts and produce electricity for homes. They were blinded to the overall simplicity of the idea by the details. Would the exhaust thrust be sufficient, could the compressor work in the proposed configuration, could the blades survive in that environment. The sum of these unsolved details paints a picture of complexity and risk. In reality however, these were all issues that Whittle could solve easily through adaptation of existing technology. However, it is human nature to view something unknown in a negative light. And in this light the overall real simplicity of an idea is always lost to the unsolved details. 

This is especially devilish. All our technical training teaches us that simple ideas are best, but our human nature tricks us into thinking that old ideas with solved details are inherently simpler then new ones with unsolved details. It isn't Occam's Razor itself that is flawed, but our own unconscious perception of "simplicity" wich gives incumbent technology an unfair advantage.   

Did we, as a technical society, learn anything from this experience? In a word, No. In two words, really No. Nothing should make this more clear then the fact that jet engine technology is now thought of as one of the simplest forms of energy generation. It is the standard by wich all new technologies are compared. We are as technically biased against new ideas as always.