Engines of Our Ingenuity

No. 95:
SUPERCONDUCTORS

by John H. Lienhard

Click here for audio of Episode 95.

Today, we ask how an invention is born. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Let's ask whether inventions fight their way into the world from inside inventors' heads, or are they made in response to worldly needs? Look at the steamboat. It was reinvented dozens of times before Fulton. But it never caught on. When Fitch ran a steamboat line in Philadelphia 20 years before Fulton, he couldn't attract enough passengers to pay for it. Of course, Fulton made a much better boat in 1807; but what's more important is that by then there was a public demand for the steamboat.

Compare that with the invention of man-made superconductors. In 1911, mercury was found to have no measurable electric resistance below about four degrees Kelvin. During the next 75 years, scientists found natural superconductors all the way up to 23 degrees Kelvin. Of course, this wasn't invention -- it was just scientific reporting.

But the practical promise of superconductivity is so great. By getting rid of electric resistance, we can work technological feats of near magic. In fact, the US Navy has, for some time, worked on the design of ships using superconducting generators. It requires a helium cryostat to cool them; but these hi-tech generators promise to save far more weight and cost than the cryostats add.

A few years ago, scientists began to see that it might be possible to invent superconductors that would work at higher temperatures -- above the boiling point of inexpensive liquid nitrogen coolant -- maybe even at room temperature.

The break came in 1986 when two Swiss scientists, Mueller and Bednorz, discovered a superconducting oxide. Then Paul Chu, at the University of Houston, rapidly created oxides that were superconducting at twice the temperature of any natural material. Pretty soon he went well beyond the boiling point of nitrogen. Suddenly the dream of practical superconductors could be realized with man-made materials -- it could be done by invention.

And the race was on. The public didn't have to be convinced about the value of this invention. Electrical industries went to war over it. The race to make practical superconducting systems has spawned remarkable tales of determination, on the one hand, and intrigue and espionage on the other.

So what is the stimulus for invention? Well, Fulton studied water transportation for years before his sudden success. And Paul Chu actually began his search for man-made superconductors back in the 1970s, when the task still seemed hopeless. It's nice when the public welcomes your ideas. But it's the human mind -- and not mere necessity -- that mothers invention.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


McKelvey, J. P., Understanding Superconductivity. American Heritage of Invention & Technology, Spring/Summer, 1989, pp. 48-57.

As I've gone through the early episodes rewriting and updating and rebroadcasting them, I skipped over this early one. That is because I have said so much about early steamboat development in other episodes, and advances in superconductivity now leave this episode dated.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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