Rockets: So Old School?

By Seth Shostak

Could rocket scientists be an endangered species?

You're probably betting "no," given the contemporary efforts to hurl hardware to the moon, to Mars, and to a passel of other unearthly locales. The rocket biz is busy, and it's diversifying. An enthusiastic troupe of private companies is also getting into the act, hoping to cash in by lifting off.

It seems that "rocket scientist" is a job category that's here for the long haul, like "mortician." But all this activity masks an important point: rockets are not a terribly efficient way to lift things into space. For every pound of payload, there are typically 25 pounds of rocket and fuel, and in some cases the vehicle is just thrown away after use. Rockets also suffer from a heavy foot on the accelerator, subjecting payloads and passengers to G-forces that warp faces into Botox ads. In addition, and despite nearly a hundred years of building these flame-belching devices, they're still vulnerable to colorful self-destruction. This is probably not a list of features you would accept in your next family car.

However, there's an intriguing alternative to traditional reaction technology that could beat rockets at their own game. It's called the space elevator.

What's a space elevator? Simply described, it's a thin ribbon, about 3 feet wide and 60 thousand miles long, stretching upwards from the surface of the Earth. The lower end is bolted to a heavy anchor (think of an oil drilling platform), and the top is capped with a counterweight. It's all arranged so that the center of mass falls at the geosynchronous orbital point, about 22,000 miles up. Like a rock on a string swung 'round your head, the ribbon is under tension, stays straight, and rotates with the Earth. Consequently, it can serve as a "track" for solar-powered motorized climbers that leisurely lift satellites, people, or other payloads into space. No combustion required.

The physics for this was noodled out a long time ago, and despite your intuition, it would work. Sure, it might take a week to crawl your way up to orbit, but if you're a telecommunications satellite, you won't get bored en route. The cost would be 100 times less than using a rocket, and you wouldn't have the usual constraints that rockets make on payload size or shape. You could also avoid the "shake, rattle and roll" of a launch - heading skyward would be a slow and steady affair, not a shuddering blast of smoke and fire. Countdowns might become déclassé.

Clearly the space elevator could grab a lot of the space transport business. So why is it still on the drawing boards, and not hauling satellites or tourists into orbit?

The answer is that the technology to build the ribbon is not yet in hand. To withstand the forces that keep the ribbon taught, the material used to make it must be a thousand times stronger than steel.

There's only one known material boasting that kind of tensile strength: carbon nanotubes, which are cylindrical molecules built of atoms holding hands with strong, covalent bonds. But a factory that can turn carbon nanotubes into a sheet a yard wide and long enough to stretch one-fourth of the way to the moon is not something you'll find at your local industrial park.

Read the rest at Huffington Post.