Today, we build an elevator into outer space. 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.

In 1979 Arthur C. Clarke wrote a science-fiction book, The Fountains of Paradise. A few months later, he wrote a two-page letter. You can read it at the end of Charles Sheffield's sci-fi novel, The Web Between the Worlds.

The letter absolves Sheffield of plagiarism. You see, Sheffield had cooked up the same mad premise that Clarke had. Both authors proposed to replace rocket launches with an elevator, anchored at the equator, and reaching up beyond the level of geosynchronous orbit. That's where an orbiting vehicle rides directly over one point on Earth. Clarke congratulated Sheffield for arriving at the same idea independently.

If their idea sounds crazy, bear in mind that both Clarke and Sheffield were distinguished scientists who later turned to science fiction. Clarke was a noted astronomer. Sheffield was chief scientist of the Earth Satellite Corporation. Both used science fiction to teach us about space travel.

And now, an elevator into space! The main element was a cable with an extremely high tensile strength -- strong enough to support its 22,248-mile length. The cable was to be a single perfect crystalline carbon or silicon fiber. We can already make whisker-like strands of such material. And, of course, we routinely put geosynchronous satellites into orbit.

Above the geosynchronous level, a satellite will fly away from earth. Below, it will fall back into Earth. So the cable above pulls on the cable below and holds it in place.

The cable would be tapered in thickness. It would be thickest at the point of geosynchronous orbit, where the stresses would also be greatest. I won't try to recite all the technology needed to make such a thing work. You can read Clarke and Sheffield to see how they put such a thing in place -- how they anchor it -- how they counterweight it above the geosynchronous level -- how they conserve the energy of rising and falling cars.

There's great similarity. Both authors were bound by the same laws of physics. Both used the same obvious name for the machine that spun the huge single fiber. Both called it a spider.

Sheffield and Clarke's wild idea had actually been invented independently by others before them. A Russian engineer suggested a version he called a "Cosmic Funicular" as early as 1960.

I certainly won't live to see such a technology. It's too large, too complex. But some of you might. The idea is plausible. Besides, rockets are a clumsy, inefficient way to get free of earth. An elevator into space is a mind-bending notion. But it could happen. It could, one day, really happen.

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

(Theme music)

Sheffield, C., The Web Between the Worlds. New York: Ballantine Books, 1979, (1988 printing.)

Clarke, A. C., An Open Letter to the Bulletin of the Science Fiction Writers of America. ibid. pp. 245-246.

Sheffield, C., Beanstalk Update: Dynamic Beanstalks and Indian Rope Tricks. ibid. 1988, pp. 247-249.

Clarke, A. C., The Fountains of Paradise. New York: Harcourt Brace Jovanovich, 1979.

I am grateful to John Proffitt, Station Manager of KUHF Radio Station, who pressed me for many years to talk about this wild idea and who provided his copy of the Sheffield book.