27-06-2004 18:08									#31
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quote: Originally posted by DRoseDARs This proposed cable is 2.5 times longer the the Earth's circumference at the Equator. If it were to come down, it'd wrap around Earth 2.5 times, probably a bit more since the Earth-bound end of it might be dragged along for a bit.

Will it really happen? I recall reading that pretty much most of the cable will just drift off into space.

	27-06-2004 19:37									#32
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the cable is not real heavy. It's not wider than a sheet of paper.

Although there would be terrorism concerns. Someone could fly a plane right into it. Even an unmanned plane...

	27-06-2004 19:48									#33
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quote: Originally posted by Urban Ranger No, Ted, that's an Orion.

He'd still hit it

	28-06-2004 02:16									#34
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quote: Originally posted by Dissident the cable is not real heavy. It's not wider than a sheet of paper.

Someone explain this to me: The article for this appeared in today's (sunday) paper and said "The cable would be about 3 feet wide and thinner than a piece of paper, but capable of supporting a payload up to 13 tons."

Huh?

Well, which is it: Thinner than paper or 3 feet wide? Or am I missing a crucial piece of the riddle?



Also amusing: They include two pictures, one of Bradley Edwards, head of the project, and an artist's graphic of the floating anchor station. There's a warning sign on the side of the platform stating, in print no bigger than that found on a freeway sign, "RESTRICTED AREA - MAINTAIN 8 MILE RADIUS"

People are going to read that at 8 miles distance? I'd be sqwinting to read that at 1/2 a mile...

	28-06-2004 02:22									#35
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As I understand it, it is as thin as paper but 3 feet wide in the sense that a normal piece of paper is about 8 inches wide and 11 inches long.

	28-06-2004 02:32									#36
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Sooo it's a sheet: thin as paper and 3 feet wide by 62,000 miles long? No, that doesn't work. Thanks, but I think I'm still missing something here...

	28-06-2004 03:16									#37
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I belive thats what they were desribing a Ribbon basicaly. This has the advantage of being less suseptable to space debress because only a small hole would be punched in the ribbon by a random piece of space debree such as a nut or bolt.

Also the Discover article pointed out that the Evelator boxes would grip the ribbon with what looks like 2 belt sanders. A much simpler and reliable system then Mag lev Cohesion. Main draw back is that you cant pass someone going in the other direction. Perhaps some sections of double ribbon would be added much like on train tracks.

Also keep in mind that a Space Elevator Cable becomes progressivly thinner closer to the earth as the bottom of the cable need only be strong enough to carry the Boxes that are on it. Each progressivly higher piece of cable need to hold all the weight of what is below it so it becomes thicker and thicker untill you reach Geosycronus orbit. The dimention they give sounds reasonable for the bottom of the cable but not the top which just off the top of my head would probly need to be 3 feet wide AND 3 feet thick.

	28-06-2004 04:02									#38
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Ridicoulous. Rebuilding WTC New York in 15 years is a more likely project.

	28-06-2004 04:12									#39
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quote: Ridicoulous

Hey, that is Paiktis's real surname

	28-06-2004 04:13									#40
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I must say though: that would be one f**k of a lot of muzak to have to endure

	28-06-2004 05:01									#41
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Well *****es ... GOING UP

	28-06-2004 09:26									#42
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Aerosmith -
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Edit: Fixed to be more annoying

	28-06-2004 09:35									#43
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quote: Originally posted by Impaler[WrG] I belive thats what they were desribing a Ribbon basicaly. This has the advantage of being less suseptable to space debress because only a small hole would be punched in the ribbon by a random piece of space debree such as a nut or bolt. Also the Discover article pointed out that the Evelator boxes would grip the ribbon with what looks like 2 belt sanders. A much simpler and reliable system then Mag lev Cohesion. Main draw back is that you cant pass someone going in the other direction. Perhaps some sections of double ribbon would be added much like on train tracks. Also keep in mind that a Space Elevator Cable becomes progressivly thinner closer to the earth as the bottom of the cable need only be strong enough to carry the Boxes that are on it. Each progressivly higher piece of cable need to hold all the weight of what is below it so it becomes thicker and thicker untill you reach Geosycronus orbit. The dimention they give sounds reasonable for the bottom of the cable but not the top which just off the top of my head would probly need to be 3 feet wide AND 3 feet thick.

So is it a ribbon or a cable? A ribbon has flat sides, a cable is rounded. Or is it both, depending on where you look along its length?

	28-06-2004 22:32									#44
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quote: Originally posted by Impaler[WrG] I belive thats what they were desribing a Ribbon basicaly. This has the advantage of being less suseptable to space debress because only a small hole would be punched in the ribbon by a random piece of space debree such as a nut or bolt.

For one thing, a cable is much harder to be hit than a really wide and thin ribbon.

Also, when the ribbon is fully stressed, a hole can cause the whole thing to rip apart.

	28-06-2004 22:55									#45
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On the other hand, a ribbon would have a high surface area and really low terminal velocity. This would seem to make it rather safe from the doomsday scenarios offered by DRose.

	29-06-2004 03:52									#46
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Drose has a point. Who will be the first couple to do it in the space elevator? That's a record many people would want to get.

	29-06-2004 04:30									#47
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15 years is based on technical considerations. Throw in political and economic ones and it's anyone's guess.

	29-06-2004 08:30									#48
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quote: Originally posted by DanS On the other hand, a ribbon would have a high surface area and really low terminal velocity. This would seem to make it rather safe from the doomsday scenarios offered by DRose.

Why on earth do you need a cable that long?

	29-06-2004 08:53									#49
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quote: Originally posted by Dr Strangelove And you're just the man for the job.

Actually, I thought Lazarus smells bad without farting?

	30-06-2004 02:14									#50
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quote: Originally posted by Urban Ranger Why on earth do you need a cable that long?

in this case the cable has to be long enough to "balance" things out. The end has to have enough centrifugal force on it to keep the ribbon taut.

	30-06-2004 03:12									#51
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Even if the cable won't damage the Earth, it'd still suck for those riding the elevator at the time. Doesn't make it any less cool though.

	30-06-2004 03:17									#52
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quote: Even if the cable won't damage the Earth, it'd still suck for those riding the elevator at the time.

Yes, their terminal velocity might be quite a bit higher.

	30-06-2004 08:37									#53
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quote: Originally posted by Dissident in this case the cable has to be long enough to "balance" things out. The end has to have enough centrifugal force on it to keep the ribbon taut.

The other end of the cable should be anchored.

	01-07-2004 03:55									#54
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I'm talking about the space end. There is nothing to anchor it to.

	01-07-2004 04:04									#55
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quote: Originally posted by Urban Ranger The other end of the cable should be anchored.

To what? You definitely need to put your "anchor" further away than geosynchronous orbit (~40 000 km IIRC)

And the closer your anchor is to geosynchronous the more mass you need to put there. It's a simple question of requiring that the net force on the upper part balances out the net force on the lower end.

	01-07-2004 04:06									#56
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quote: Originally posted by Dissident I'm talking about the space end. There is nothing to anchor it to.

The sugestion I've heard for anchoring the space end is to put a huge hunk of mass on the end somewhere above geosyncronous orbit. That would provide a counterbalance to the mass below. But the minimum possible length would be the height of geosyncronous orbit. Making it exactly this height would require an infinite anchoring mass.

	01-07-2004 04:15									#57
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quote: Originally posted by Immortal Wombat That's arguable. 15 years is somewhat optimistic, shall we say. And of course, once we have built it, it'll break or fail or something. And being stuck in a lift 10 miles above the earth for 18 hours while the engineers try to fix things - that wouldn't be much fun.

I don't think it's intended for people (it would be exciting tho), but as a cheap way for launching satelites and stuff into orbit.

	01-07-2004 04:22									#58
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Let's see now. In the accelerating reference frame of the rotation of the earth, the "force" a mass m experiences is equal to m * (GM/(r^2) - r*w^2) (downward) with M the mass of the Earth, r is the distance from the centre of the Earth to the mass and w is the angular frequency of the Earth's rotation i.e. 2Pi/24hours (assuming you put all these in the right units)

Now, say we assume that we have a material with a maximum (mass) tensile strength of s (s is gotten by dividing the cross-sectional tensile strength t by the mass density p so s = t/p and thus has units of Newton*metres/kilograms = metres^2/seconds^2).

Say that we want to hold up a maximum car mass of m. This makes the bottom of the cable required have a linear mass density of u0 = m/s*(GM/R0^2 - R0*w^2) where R0 is the radius of the Earth.

	01-07-2004 04:22									#59
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quote: Originally posted by KrazyHorse The sugestion I've heard for anchoring the space end is to put a huge hunk of mass on the end somewhere above geosyncronous orbit. That would provide a counterbalance to the mass below. But the minimum possible length would be the height of geosyncronous orbit. Making it exactly this height would require an infinite anchoring mass.

that's why you make it longer.

The figure I heard was twice the height of geosynchronous orbit.

	01-07-2004 04:35									#60
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