In his article “The Systems Engineering Mindset, Problem Solving and Critical Thinking,” James Lackey makes the case that the principles of Systems Engineering can and should be practiced by everyone. I’d like to expand on his point by taking a Systems Engineering tool and applying it to life. In this article I’ll talk about Extremes.
Systems Engineers are responsible for writing requirements – a set of rules which govern performance of a widget to be built. Most of the requirements deal with the typical operation of the widget. For example, a car has to be able drive at 55 mph in temperatures between -20°F and 120°F.
It’s useful to think about the extremes. Think about the speed of a car as an example. If you drive the car at 0 mph on the highway, you will likely cause an accident. If you drive the car at 400 mph, not only are you as likely to cause an accident, there a good chance of a speeding ticket.
What have I learned? Unless I want my customers to cause accidents and get speeding tickets, the car needs to be able to go faster than 0 mph and doesn’t need go faster than 120 mph. And this certainly helps control costs, since designing a car that can do 400 mph would be much more expensive.
Here’s another example. One of my hobbies is woodworking; I’m currently building a dinner chair for the first time, and I don’t know how many slats to put in the back of the chair. One extreme is 0, but that doesn’t provide much back support. At the other extreme is 10,000 slats. But each slat needs to be machined, and requires a matching mortice. Since I’d like to finish the chair this year, I’ve decided on less than 10,000 slats. Six slates seems a reasonable compromise between 0 and 10,000.
If you’re thinking that these examples are silly because no one drives faster than 400 mph or would use 10,000 slats in a chair, you are exactly correct. And that’s kind of the point. You can always narrow it down, but it’s useful to think about how a system, whether it’s a car, a chair, or the electric propulsion subsystem of a geosynchronous communication satellite, will behave under extreme conditions.