Space Elevators Face Wobble Problem

NewScientist is reporting that while the strength of the tether has long been considered the main problem in building a space elevator, a new study suggests that a dangerous wobbling problem may also be a serious obstacle. "Previous studies have noted that gravitational tugs from the Moon and Sun, as well as pressure from gusts of solar wind, would shake the tether. That could potentially make it veer into space traffic, including satellites and bits of space debris. A collision could cut the tether and wreck the space elevator."

Comments

When will it become a reality?

[genesus]

During a speech he once gave, someone in the audience asked Arthur C. Clarke when the space elevator would become a reality.

"Clarke answered, 'Probably about 50 years after everybody quits laughing,'" related Pearson. "He's got a point. Once you stop dismissing something as unattainable, then you start working on its development. This is exciting!"

http://science.nasa.gov/headlines/y2000/ast07sep_1.htm

I am more concerned about the static problem

[Black Art]

I would be more concerned about the space elevator becoming a giant van degraff generator. Something that long would present some very interesting problems. Huge frikin lightning rod might be a better description.

Re:wreck the elevator

[alta]

Actually, no. The rotation of the earth would cause the ribbon to wrap around the earth in an easterly direction. To refute myself as well: http://en.wikipedia.org/wiki/Space_elevator#In_the_event_of_failure says that most of it would burn up on re-entry and that which doesn't will have less force than a piece of paper. So, please disregard my statements, but it sounded impressive the first time I said it ;)

Re:A collision could cut the tether...

[zippthorne]

No, most designs specify a thin ribbon. So, no matter where it breaks, it won't impact the ground at more than terminal velocity for thin, burnt sheets.

The design that specified steel cable did so specifically to show how impractical it would be to attempt a cable using existing materials.

The Stealth Fighter and Bomber Are Unstable, Too

[curmudgeon99]

The Stealth Nighthawk fighter could not be controlled by a human, it is so aerodynamically unstable. But with the help of some good software, that plane flies. The same is true of the B-2 Batwing bomber, it only flies because a computer stabilizes it.

There will be controllable vanes (for the atmosphere) and thrusters (for space) to control the car's behavior. The wobble would be predictable and all the traffic would be required to avoid it, in the same way power boats are required to steer around sailboat.

being unstable doesn't preclude it being usable

[slew]

Just because it's unstable doesn't mean it's impossible to get working.

For instance most modern fighter aircraft are aerodynamically unstable, but they still fly. For example, the F16 was deliberatly designed to be unstable (to gain better manuverability). Of course the F16 has a computer control system to make it flyable by humans, but if the computer dies, well, unstable tumble modes ahead... I've also antecdodally heard that some modern bridges and tall-buildings are also not inherently stable (and are actively stabilized by computer control systems).

But to be honest, I think the engineering of a space elevator is pretty much beyond our forseeable technical ability (material science, control systems, assembly techniques, not to mention project management, risk/return estimation, and financing/underwriting).

If you think the problems are merely about waiting for technology, just think of the chunnel. It was imagined for a long time, but even after they got all the science and technology and assembly issues under control, the project management, risk/return estimation and financing/underwriting issues managed to kill a few companies before if finally got done.

Re:Then why not a space escalator?

[esampson]

You do realize that most goods imported are imported on ships rather than airplanes, right? The reason for this is because while it is possible to import everything by airplane (as was done in the Berlin airlift) it is much more expensive to do so. In the case of a person traveling across the ocean the extra energy can be justified by the convenience of rapid travel. Most shipped items however don't have to be anywhere in any particular hurry so if it takes a few weeks for them on a boat it is no big deal.

Similarly a space elevator can be used for things such as hauling materials and supplies up to geosynchronous orbit and if it takes days or weeks or even months that's no big deal since the materials don't care. In the mean time the energy saved on transporting literally hundreds of millions of tons (eventually) of payload into space via elevator would be immense.

Re:Then why not a space escalator?

[gwait]

It would definitely ground any storm coming along, with a nice big flash!
Their copper tether was nowhere near as long as a satellite tether would be, and theirs wasn't shorting out a thunderhead like a satellite tether would,

Now, IF you could somehow manage the danger of a sudden lightning strike, I think you're right that there would be large voltages across the length of the tether, and you should be able to harvest it for a power source. The act of harvesting the electrical charges might even be a part of the solution..