The Space Elevator Comes Closer to Reality

space.com ^ | 27 Mar 02 | Leonard David

[mrsmith]

.
"A line directed from a [planet] to a [satellite] sweeps out equal areas in equal times."

I wish someone would point out the reason the shear forces on the cable from this law are not considered a problem for the elevator.

[justshutupandtakeit]

I am saving my money for the car engine which runs on water.

[Pablo64]

"The amount of potential energy stored in the thing would be staggering."

That was one of my first thoughts as well. What if this sucker breaks? What kind of problems would be caused by a severl thousands of miles of cable crashing back to earth (or am I missing something that the physics guys can clue me in on)?

The other question that I had was regarding the initial deployment. The article indicated that they would snake the cable down from orbit. What, exactly, would make the cable want to come "down" as opposed to "left" or "right" or even "up"? If they are in orbit, aren't they free from most of the effects of gravity (just what pull there is to hold them in orbit)? Wouldn't they have to shoot the cable back down through the atmosphere with some type of rocket?

Very interesting article, but it sure brings up lots of questions, as well as painting some very strange mental pictures (envision our planet with hundreds of these cables sticking out from the surface, like a big, giant spiked hairdo!!)

[js1138]

Imagine the potential conflict with commsats in geosynch orbit.

Comsats have a life expectancy of maybe 10 years. The hub of a space elevator would resemble "Cloud City" from Star Wars -- it could be big enough to house a broadcasting empire.

My first thought was: "What about terrorists?" But with a dozen or so of these things, the effect of losing one would be affordable with normal underwriting.

As for safety, the hub would be in orbit. There would be a tethered weight extending beyond orbital altitude, exerting a constant pull. This would have to disengage quickly in an emergency -- such as loss of the ground connection.

[avg_freeper]

I challenge any one to point to an equatorial region that isn't under constant tyranny and upheaval.

Hey, I know what we could do! We could spend Trillions of dollars on it just so some limp do-nothing future president from Georgia (Jimmy Jr.?) can give it back to the natives. That would be swell!

[tom paine 2]

A pure stock play on nanotechnology is the Nanophase Technology company trading on the NASDAQ under the symbol NANX

[FourtySeven]

I wonder if in this elevator, they could finally make the "close door" button work.

Now that would be an achievement!

[NonZeroSum]

What kind of problems would be caused by a severl thousands of miles of cable crashing back to earth (or am I missing something that the physics guys can clue me in on)?

Well, when I asked the question over at sci.space.policy, here was one response from Andrew Case:

"The danger is a breakage higher up the cable, causing the lower portion to fall to earth. If you make the break high enough you can wrap around the planet, destroying everything on the equator for probably at least a couple of miles on either side. Assuming a linear density of only one ton per meter, that's a thousand tons per km. Striking the earth at an average velocity of (number out of the air) 4 km/s, that's 2 kilotons per km. Note also that blast effects due to impact will be scaling more like 1/d rather than the point blast 1/d^2.

An absolute worst case scenario would involve a cable break near GEO, in which case the last few hundred KM would be reentering at more like 8 km/s for a total of 16 kilotons per km."

[FourtySeven]

We should send Daschle up as the first human passenger. In honor of his elevator shoes, naturally. Maybe we could just forget to bring him down, once up there. He's be reunited with his ego, anyway, which has been in geosynchronous orbit above Washington for years.

LOL......this was good.

[SuperLuminal]

A clear indication of the depths to which American-born science has deteriorated.

Without immigration, there would be no science of any kind in the U.S.

Still, IMHO, in the long run we would be better off with a 10-15 year elimination of all immigration....legal or otherwise.

Science, for native-born and educated Americans, will not return to its status and accomplishments of 30-60 years ago until the entire government asylum system for brainwashing the government's children is completely destroyed/eliminated.

[john in missouri]

Um, maybe this is a dumb question, but wouldn't all those cables cause a drag and affect the earth's rotation?

In a word, no. The overall weight factor would be virtually zero because of the great weight of the earth's mass. It would be like the stress of a ball bearing hanging by a thread from the Brooklyn Bridge. Not even that.

In terms of drag, the atmosphere rotates with the earth, so again we're talking about essentially no effect at all.

If we can keep ourselves from destroying each other, we are about to pass the era of the Mayflower, Cortez, Hernando de Soto and Henry Hudson. The shipping lanes are about to open, and colonization of space is about to begin. I hope it does begin to happen within our lifetime.

Next major projects after that: earth orbital space colonies (long term) and terraforming Mars (real long term, say a thousand years).

[Doctor Stochastic]

Comsats? With the cable, the satellite could be grounded.

[js1138]

Concerning the potential destruction resulting from a break:

First, the land points would probably be at sea, a variation on the deep sea oil rigs. Second, the cable would encounter considerable air resistance as it fell, and presumably it would be light for its cross-section. Being made of carbon, the higher portions would burn on re-entry.

Recall that for a 22,000 mile cable, 21,980 miles of it would be re-entering the atmosphere.

[RightWhale]

a test cable on the moon

Is there a selenostationary orbit? Moon launches could easily be done with any kind of catapult.

[js1138]

A half dozen of these suckers could replace all comsats. And be quickly repairable. A dozen would give a margin of comfort against one or two disasterous failures.

I believe Clarke's book addresses terrorism. It should. He lives in Sri Lanka.

[RightWhale]

Singapore

[aimhigh]

Now I just need the $5 billion, Edwards added.

Ya, me too. And I suppose you want that out of my pocket.

[RightWhale]

Case's case is first assumptions worst-case. Reality won't be anywhere near that. There might be a lot of soot in the air. Some splashing, some fires here and there.

[RightWhale]

Earth-moon L-4 and L-5 could be considered stable selenostationary to a degree if you don't mind lima-bean orbits, but they aren't particularly close to the moon.