Engines of Our Ingenuity


John Lienhard presents Fitz Walker

Today, our guest, NASA engineer Fitz Walker considers the Microwave Oven. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

microwave oven

My wife is a murderer. She murdered our wonderful microwave oven. I had it longer than I knew her. That oven was one of the first things I bought after I graduated college and was finally out on my own. Without it, I probably wouldíve starved to death.

We all dread that phone call informing us that a loved one had passed away unexpectedly. I received one such call during a business trip away from home. My wife called to admit she had committed felony "microslaughter" by accidentally setting the microwave timer to 30 minutes instead of 30 seconds. The food sheíd tried to heat up caught fire and proceeded to destroy the internals of my beloved device.

Accidents happen of course and we did get a good ten year run from it. But now we had to resort to that primitive food heating device, the oven. Where it took a whole 15 minutes to heat up yesterdayís dinner. Surely itís a crime to have to wait that long to sate my hunger pains.

Whatís even more remarkable is how our lives can center around this magic box. Every place Iíve worked has had one or two in every break room. No home is considered complete without one.

Even so, I couldnít just go out buy any new model; we had to mail order that special one since the local stores didnít have the exact type we wanted. That meant a whole week without a way to quickly heat up food. Being without out a microwave oven is like saying we can live without air conditioning. Sure, it would be life, but a horrible soul draining life.

So as I was lamenting my temporary regression in kitchen technology, this got me thinking. Iíve never really known life without this ubiquitous device. How did it enter our lives?

I found out that like many inventions of our time, the microwave oven was invented in part by accident. A sweet, sweet accident: Percy Spencer, a radar engineer from Raytheon, noticed the candy bar in his pocket had suddenly melted, and he immediately realized the high frequency transmitter heíd just turned on was the culprit. When he started placing various other food items in front of the experimental device, he had similar results. Some of which, such as when fresh eggs were heated, were quite explosive.

Microwave oven Magnetron

The device he used is called a Magnetron. And while it sounds like something out of science fiction, itís actually just a very high frequency form of vacuum tube. One of the most common uses of Magnetrons is in radar systems.

Percy quickly realized that this technology had enormous commercial potential and proceeded to help develop a food warming device for every day use. Despite the first models being very large, very expensive, and even needing plumbing for water cooling, their usefulness was almost immediately proven in the marketplace.

It was only a matter of time before they were simplified and miniaturized onto what we use in our kitchen today. And yes, that very same microwave in your home or at work very likely still has in it that one last 20th century electronic dinosaur — the vacuum tube.

Microwave patent diagram
Microwave patent diagram

Iím Fitz Walker on behalf of the University of Houston, interested in the way inventive minds work.

(Theme music)

A Brief History of the Microwave Oven

What Is a Magnetron?

American Radio Relay League. The ARRL Uhf/Microwave Experimenter's Manual. Connecticut: American Radio Relay League, 1990. Print.

Images are from the following sources:
Microwave Oven is from the Oregon State University Website.
Microwave patent diagram is from Mindfully.org.
Microwave oven Magnetron is from Wikipedia Commons.


Fitz Walker has worked in the aerospace industry for over 10 years. Currently he works doing space station software quality roles at the Johnson Space Center. He has a degree in Avionics Engineering from Embry-Riddle Aeronautical University and has written for several magazine and web publications on a range of topics from robots to radio controlled model airplanes. He also has a FAA glider pilot license and a passion for building scale models. A native of Connecticut, he claims to have moved to Texas as soon as he could.

This episode was first aired on January 27, 2012

The Engines of Our Ingenuity is Copyright © 1988-2012 by John H. Lienhard.