But What Would Hold It Up?

[crokett]

Japan to start work on a space elevator:

http://www.timesonline.co.uk/tol/new...cle4799369.ece

So the obvious question is, what would hold it up? Or is it similar to a ball on a string that I whirl around? And in this case the string is long enough to get the 'ball' far enough away so centripetal force overcomes gravity?

[Kristofor]

Japan to start work on a space elevator:

http://www.timesonline.co.uk/tol/new...cle4799369.ece

So the obvious question is, what would hold it up? Or is it similar to a ball on a string that I whirl around? And in this case the string is long enough to get the 'ball' far enough away so centripetal force overcomes gravity?

Beanstalk, Skyhook, space elevator call it what you like, it's a pretty common device in Sci-fi books/movies... You're right-on that centripetal acceleration of either the cable or an anchor is what would keep it in place. I've seen a number of articles in the last few years about the materials needed to spin the cables getting close (within a factor of 1.2-3x rather than orders of magnitude) to the strength needed (at the mm scale at least) to build a working system. They have to be tethered on/near the equator though, so it's not something they'll be building/assembling on the main islands...

Kristofor.

[LCHIEN]

http://en.wikipedia.org/wiki/Space_elevator for details
The space elevator consists of an anchor point on earth (at the equator) and a large mass at or above the geostationary orbit point 22,000 miles above the earth (way beyond the space station orbit of a few hundred miles). Items in the 22,000 mile orbit rotate at the same rate as the earth and thus appear to be directly overhead at all times to the anchor point. A large mass beyond that point tethered will be slung outwards by centrifugal force. A very strong and lightweight cable can be used to tether the mass and hoist payloads to the orbiting station taking much less power than conventional launches.

So far the caluclations for the cable properties require strength to weight ratios somewhat in excess of what we currently know how to make. we also don't know exactly how to get the large station at the right point... currently we can barely get large payloads to the low earth orbit. The cable will have to support its 22,000 mile long weight (some of it at reduced gravitiational pull) and the pull of the station in space which will keep it taut, I presume.

Anyway once the space elevator is in place and working, then we can put large payloads in high earth orbit all the time for relatively low cost using self-powered climber units that will either be dropped for conventional style re-entry or used for counterweights to help other climbers get up there.

[Wood_workur]

anyone think the mass needed to make the string stay taught may act as a gyroscope and mess up the rotation of the earth?

[crokett]

anyone think the mass needed to make the string stay taught may act as a gyroscope and mess up the rotation of the earth?

I sure hope they've thought of that.

[Wood_workur]

I sure hope they've thought of that.

or better yet get us stick in good weather.