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davidratcliff6255
Radio Wave


Australia
20 Posts		 Posted - 02/01/2003 :  00:31:28  Show Profile Send a private Message  Visit davidratcliff6255's Homepage  Send davidratcliff6255 an ICQ Message
Poll Question:
Is endless spanning (orbital) bridge possible? See: http://groups.msn.com/DavesBridgesandTowers

Results: (4 votes counted so far)
Yes   (75.0 %) 3 votes
No   (0.0 %) 0 votes
Not sure   (25.0 %) 1 votes



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enigma
PF Advisor


USA
1016 Posts		 Posted - 02/01/2003 :  01:15:17  Show Profile  Send a private Message
On paper, yeah, maybe.

In reality, I'd be leaning toward no.

An object like that would be inherintly unstable. If you have a satellite, and it's orbit gets shifted slightly so it swings a little closer to the earth, it usually isn't a critical problem. The orbit will merely become slightly eccentric, and it will have a closest point (perigee) and a furthest point (apogee).

For the ring, if one part of it gets closer to the earth, the earth not only pulls harder on that side, but the opposite side is now farther from the earth and gets less gravity pulling on it. It will quickly fall to earth.

Now it may (big may) be possible to place some sort of thrusters, but that thing would be ENORMOUS. You would need extraordinarily large amounts of fuel to power the stabilizers... steel weighs ~8 gm/cm^3... the ring would be, what, 60,000km long? It'd be like trying to move a tank by sitting on top of it and blowing.

Thats not to mention interactions with the Van Allen belts, thermal strain from huge temperature differences, vibrations, impacts, repairs, maintanence, and a million other things I'm sure I couldn't even possibly think of.

enigma

"Life is the crummiest book I've ever read. There isn't a hook; just a lot of cheap shots, pictures to shock, and characters an amateur would never dream up."
-Bad Religion
Stranger than Fiction

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davidratcliff6255
Radio Wave


Australia
20 Posts		 Posted - 02/01/2003 :  14:27:39  Show Profile  Send a private Message  Visit davidratcliff6255's Homepage  Send davidratcliff6255 an ICQ Message
Enigma, Perhaps I should not have said 'orbital' - Well I suppose that it would be in orbit, but would no doubt have to be held in place by cables to stop it from wavering about. Main thing is that it would not be supported in any way!
I guess the main question I am asking here is: Provided that you could supply the necessary restraint for a ring girder. Would the tubing crush within itself?
In order to build the bridge in the first place, you would have to float it across the oceans as well as have support on land whilst building it. - So you'd more than likely leave the supports there anyway! (spaced about every 5 km apart)

I don't believe that heat expansion (as well as contraction at the same time on the opposite cooler side) would be an issue. Vibration I have often wondered about though, as the ring would be so stiff (a bit like how a tight string vibrates in the wind).
Sorry, I couldn't decide which forum was more appropriate so put it in both. The following is from the same lines as in the technology forum:

Because we're so used to instability, and massive weigh burying into the ground, and distance, it's all too easy to dismiss an endless bridge. I like the length of pipe idea, it makes sense! Whatever it weighs is all that will be pushing into it! There's nothing sideways except for wind. - Gravity pulls down, not sideways (not necessarily says Walter Wright). That weight is all evenly distributed into the entire length of tubing. There's no weight sideways until the tube meets and joins up. The weight is all evenly distributed. There's nothing there but its own weight! It IS all about gravity, but there's not as much as we think. - Not in an endless bridge anyway! - Endless tower? - No way!
Dave.



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enigma
PF Advisor


USA
1016 Posts		 Posted - 02/01/2003 :  17:27:49  Show Profile  Send a private Message
What sort of altitude are you talking about?

Keep in mind that steel has a yield stress of ~200MPa. The trusses will simply collapse in on themselves from the excessive compression. The truss itself would need to support it's own weight, and that weight would just be enormous.

enigma

"Life is the crummiest book I've ever read. There isn't a hook; just a lot of cheap shots, pictures to shock, and characters an amateur would never dream up."
-Bad Religion
Stranger than Fiction

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davidratcliff6255
Radio Wave


Australia
20 Posts		 Posted - 02/02/2003 :  03:36:28  Show Profile  Send a private Message  Visit davidratcliff6255's Homepage  Send davidratcliff6255 an ICQ Message
Please go to "Technology" forum. Hope you will continue with this discussion there. Please understand also that I have only had a computer for a few months as is a whole new learning experiance for me. This is an excellent site though!
Sorry for any inconveniances. Dave.



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enigma
PF Advisor


USA
1016 Posts		 Posted - 02/02/2003 :  05:14:50  Show Profile  Send a private Message
Can the moderator please lock this thread?

Dave, posting in one place is plenty (and this is why). Most folks just use the 'active topics' button anyways.

enigma

"Life is the crummiest book I've ever read. There isn't a hook; just a lot of cheap shots, pictures to shock, and characters an amateur would never dream up."
-Bad Religion
Stranger than Fiction

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