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September 23, 2003 6:34 PM   Subscribe

An Elevator to the Stars. The paper of record claims this isn't science fiction, but do we really believe that in ten years we'll be able to build a 60,000 mile long cable capable of supporting 13 ton cargo loads? Would you trust this to take you into asynchronous orbit? (Or maybe you just want to make like Joe Kittinger and jump out at 100,000 feet.)
posted by alms (24 comments total)

 
that's geosynchronous... asynchonous would presumably involve spinning at a different speed than that required for gravity and centrifugal force to balance out.

Incidentally, geosyncronous orbit is like really far away. 24000 miles or so, depending on the weight of the object. Compared with the low earth orbits of shuttles, space stations, which are about 200 miles. This is why there's such a long delay in satellite conversations: the limitations of the speed of light actually come into play.

Another interesting factor is that I think they have to be built near the equator. Which brings up all sorts of funky political issues. Will there be some new form of colonialism dedicated to guaranteeing the north access to these things? A panama canal for the 21st century?
posted by condour75 at 6:46 PM on September 23, 2003


Did anyone read the Red Mars trilogy? If a beanstalk like this were to ever fall it would be bad.
posted by bshort at 6:47 PM on September 23, 2003


Also here.
posted by dg at 6:53 PM on September 23, 2003


This idea has come up on MeFi and elsewhere a couple of times in the past (3/27/2002, 1/7/2001) and it really looks like it will be feasible within the next decade or so.

One of the impressive things about the work that's gone into it so far is that many of the problems that could come up have already been anticipated.

Thus, condour75, the base station will most likely be out at sea, in order to help avoid lightning and ease security concerns.

And bshort, it's thought that if this sort of elevator was severed somewhere, any portion that reentered would most likely burn up before it hit land. (In the Mars trilogy, IIRC, the cable came down because someone deorbited the counterweight, which seems like a very low-probability event in this sort of system.)
posted by Zonker at 6:54 PM on September 23, 2003


awwwww... I had this wonderful image of a balmy South American port city with a shimmering cable reaching upwards to the zentih. And a cast of colorful expats and rough harbor trade making backroom deals for space access. Sort of a mix of Star Wars, Miami Vice, a Jimmy Buffett album, and Casablanca. Oh well. [note: Condour does not endorse Jimmy Buffett.]
posted by condour75 at 7:06 PM on September 23, 2003


umm, excuse my idiotsyncratic use of terminology in the fpp. mea culpa.
posted by alms at 7:07 PM on September 23, 2003


Well, to get around the bean stalk wiping out some innocent bystanding country you could rig it to disintegrate in the event of collapse. Unlucky for the people presently using it but in the overall scheme of things good. If the elevator breaks or becomes structurally unsound charges detonate along it's length breaking it into a number of smaller parts which either burn up on reentry or are further demolished.
posted by substrate at 7:07 PM on September 23, 2003


...and rough harbor trade making backroom deals for space access.

or spaced out harbor trade making backroom deals for rough sex.
posted by quonsar at 7:14 PM on September 23, 2003


or traded out harbor spacers making deals for rough backroom access sex. the possibilities!
posted by quonsar at 7:16 PM on September 23, 2003


A NASA page about the concept. And let's not forget Fountains of Paradise, the 1979 novel where Arthur C. Clarke popularized the idea.
[Note: ?! does endorse Jimmy Buffett, but is horrified to be reminded of Miami Vice.]
posted by ?! at 7:17 PM on September 23, 2003


Here's an interesting little tidbit: In 1976 a group of Equatorial countries made a bid to declare sovereign rights over their prospective chunk of geosync orbit. Apparently they were entirely ignored.
posted by condour75 at 7:33 PM on September 23, 2003


On that NASA page it says the earth-end of the cable would be tethered to a base tower 50km tall(!).

Why not just tether it to the ground? It seems like building a tower that high would be a challenge in and of itself.
posted by bshort at 7:35 PM on September 23, 2003


A planet where apes evolved from men?
posted by namespan at 8:01 PM on September 23, 2003


You anchor to a tower to provide a clear separation point in case the cable parts. The cable is attached to a counterweight that is in an unstable orbit -- it will want to fly away, if released, but it's held to the earth by the cable.

If the cable parts, it'll have to fall at least 50km before it hits the ground. While it's falling, you reel in the portion of the cable that's still attached -- the rest flies away with the counterweight.

As to building a 50km tower? Yeah, it's hard. But when you're building a structure that goes far higher, that's easy.

A more elegant solution than the counterweight is an over-tall tower. You need the center of mass to be in a geosync orbit. So, you make the tower go out to twice that distance -- nearly 80,000km tall, which puts the center of mass at geosync. Why do this? The end of the tower will be whipping around the Earth at well over escape velocity. For earth orbit, you get off in the middle -- but to go to Mars, you just go to the end, and let go at the right moment, and you're on your way.

Then, you go crazy. Build three or four more towers. Build a ring connecting them. Build them higher -- flinging payloads across the solar system.

It's a wild dream -- but the only real implausible part was finding a substance that could handle the tension. Carbon nanotubes appear to be just the thing. All the rest is engineering and money.
posted by eriko at 8:03 PM on September 23, 2003


Why anchor the entire cable at one location? If it's hundreds of bundled fibers, why not split them off at the earth end and anchor them at multiple points? That way you have reduncancy and it makes it easier to repair a few faulty parts without having to disable the entire cable.

...and don't anybody bring up that "frayed knot" joke.
posted by fatbobsmith at 8:09 PM on September 23, 2003


It sounds like NASA decided that no matter how tall the (theoretical) tower is, it won't work until we come up with either exponentially stronger materials or radically different construction methods. Pity, that.
posted by yhbc at 8:12 PM on September 23, 2003


That NASA link's from January, 2001, yhbc. I'd say it's obsolete by now, especially in light of the conference Los Alamos held a couple of weeks ago. (And in any event, whenever NASA says that alternatives to the Space Shuttle aren't ready / affordable / reliable / etc., you should consider the source, and take their pessimism with a large grain of salt.)
posted by Zonker at 8:26 PM on September 23, 2003


I'm confused. Does it take a rocket scientist to build a space elevator?
posted by fatbobsmith at 9:07 PM on September 23, 2003


...and rough harbor trade making backroom deals for space access.
or spaced out harbor trade making backroom deals for rough sex.
or traded out harbor spacers making deals for rough backroom access sex. the possibilities!

Like the 60,000 Mile High Club?

Does it take a rocket scientist to build a space elevator?
That's the scary part. Kids wanting to grow up to become Elevator Operators.
posted by wendellseviltwin at 9:16 PM on September 23, 2003


Not that this means anything to anyone, but my failed NaNoWriMo effort last year involved one of these 'elevators,' anchored in Hawaii. I find it interesting that most writings related to the concept advocate "the central Pacific" as the ideal anchor point.
posted by pzarquon at 10:09 PM on September 23, 2003


i've said it before and i'll say it again, if anyone was to seriously build one of these things i would drop everything to work on it (read the mars trilogy as a kid and became a structural engineer).

As for the actual material i'm a bit concerned how well the carbon tubes will behave in out of plane characteristics. There are a few materials out there now that are exceptionally good in tension but not at all good when a force is placed in a directin not corresponding to that tension load (carbon fiber is one of them). Additionally, typically a stronger material will have a much more brittle behavior (thus it will snap instead of bend). If i ever go back to get a PhD i'd love to experimentally look at the carbon material as a structural engineer (ie: as a large mass of material) and not as a chemist (one of the main issues holding the whole scheme back is that while we can now produce the tubes in very short strands we have yet to find a way to produce a large amount of them)

I've also heard suggestions that Perth (australia) may be an option for a base as it's "near" the equator and is a stable nation (as long as you consider calling everyone "bruce" stable).

As for the 50 Km tower i'd say it'd probably be more cost effective to have the cable extend out towards space (becuase the tower would extremely lower the center of gravity for the system, plus i'm not quite sure how the lowered level of gravity in relation to distance form the centroid of the earth effects the whole equation). You'd have more luck building it on top of a mountain (or just burying the cables 50 km into the earth).

the beauty of science fiction is it lets you dream before you have to work.
posted by NGnerd at 10:36 PM on September 23, 2003


In my half-awake haze I read the FPP link as "An elevator to the stairs."
posted by mmoncur at 6:14 AM on September 24, 2003


Dr. Anders Jorgensen of Los Alamos raised concerns that as the ribbon swung around through the Earth's magnetic field, it would create strong electric currents.

Call me crazy, but does this not sound like the best alternative energy source ever? Just treat the earth's magnetic field as one gigantic generator?
posted by ook at 3:00 PM on September 24, 2003


Well, what happens after we've used up all the rotational energy of the Earth? Huh? Huh? I'll tell you what'll happen: global warming, except only on one side of the globe!
posted by kindall at 5:19 PM on September 24, 2003


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