The Gibraltar Bridge

[Hydey]

Forget the bridge and feed the starving

[Imran Siddiqui]

How about a BIG catapult?

[KrazyHorse]

Originally posted by Zkribbler


Are you talking about skystalks?? Skystalks won't work on Earth. The weight of skystalk streching from orbit down to the ground will overcome the tensile strength of even theoretical materials

I'm picturing a theoretical material right now. It has a tensile strength/cross-sectional area 100 000 times greater than steel, and it weighs 1 kg/cubic meter.

I plan to build a space elevator for less than a million dollars...

[KrazyHorse]

Oh, Zkribbler:

http://www.spacedaily.com/news/future-01f.html

I was a bit too lazy to integrate out the expression I got for tensile strength-to-weight requirements for a space elevator, so I did a quick search.

First off, as should be obvious to most of us,

almost anything would work in principle, provided it was appropriately tapered: widest at geostationary orbit, where tension is highest, and narrowest at the extremities

Then, to demonstrate what the major problem is:

A steel cable 1 millimetre across at ground level would have to be 40 billion kilometres in diameter at geostationary orbit

Even Kevlar, which is stronger and lighter than steel, would need to widen to 16 metres, so you'd need 2 gigatonnes of the stuff

Finally, for a practical solution:

For a cable of practical dimensions, you need a material with enormous tensile strength. NASA's estimates suggest a magic number of 62.5 gigapascals -- that's 30 times stronger than steel and 17 times stronger than Kevlar

This doesn't seem like that far away, given recent materials science research, which has made numerous breakthroughs on the nano-material front.

These tiny, hollow cylinders made from sheets of hexagonally arranged carbon atoms exceed the tensile strength of steel by at least a factor of 100. Even conservative estimates place their strength at 130 gigapascals, which surpasses the magic number by a comfortable margin

Of course, the practical applications of nanofibres to mass-application have still to be determined, but these aren't insurmountable. Also, carbon nanotubules are, as far as most physicists are concerned, yesterday's news...

I particularly like this quote, given at the end of the article:

So if all goes well, when can we expect such a structure to be built? Arthur C. Clarke was once asked this question and came up with the answer: "The space elevator will be built about 50 years after everyone stops laughing". They just stopped.

That jives with the timescale I'd vaguely envisioned: I might just live long enough to see it...

[morb]

first of all, what's in Morraco? why would anyone get in their car on a saturday afternoon and drive to Morraco of all places?

secondly, the only way to build a bridge in this situation that would make sense and be cost effective, etc. is to make a floating bridge with rasing or stacking sections for ship traffic. but then this defeats the whole point of building a bridge there, or to have a marvel of engineering.

the only reason for this bridge to exist is so that terrorists have one more target to bomb IMO.

[KrazyHorse]

Why would anybody drive to PEI? It has a population of 140 000, IIRC...

I'm certain a Gibraltar bridge would have a heck of a lot more traffic than our Confed. bridge would...

[Asher]

Was the Confed Bridge a "make work" project from our lovely government?

[KrazyHorse]

PEI was guaranteed constant access to mainland under terms of joining Canada. The two giant ferries that provide it were about to pull a "Sea King" maneuver, unless replaced, and the bean counters figured out that it would be more economical to actually bite the bullet and buy a bridge now that would increase access and last for 75 years.

BTW, the bridge was contracted for under the Mulroney gov't, and construction started just as Chrétien was taking office...

http://www.confederationbridge.com/en/accueil/index.htm

They did it for a nice, round billion dollars.

[Gatekeeper]

The bridge proposal looks fascinating. Expensive, too, I imagine. Hmm ... what's the frequency of seaquakes in the Gilbratar area? It'd be a darn crying shame if the bridge were built, only to be knocked out of commissiion by a most ill-timed seaquake.

Gatekeeper

[Ned]

Why not a tunnel?

[MrFun]

You mean a chunnel, Ned.

[Asher]

I don't know if it'd be called a chunnel, since it's not a channel it's being dug under, no?

[Zoid]

Originally posted by morb
first of all, what's in Morraco? why would anyone get in their car on a saturday afternoon and drive to Morraco of all places?

secondly, the only way to build a bridge in this situation that would make sense and be cost effective, etc. is to make a floating bridge with rasing or stacking sections for ship traffic. but then this defeats the whole point of building a bridge there, or to have a marvel of engineering.

the only reason for this bridge to exist is so that terrorists have one more target to bomb IMO.

True, the EU is presently doing all they can to shut africans out. A bridge would counteract that purpose...

It´s good to have visions, but they seldom come true. When they built the Öresund bridge between Sweden and Denmark, visionaries raved about a "Öresund region" that would integrate Denmark and Sweden. It would make commuting between countries possible and facilitate an integration of the two former archrivals boosting the economy in both countries.

Reality in the form of quarrel over taxes and stuff did put a spoke in the wheel however. So much for a "Öresund region"

The same will happen in Gibraltar-Morocco region IMO, even more so since Morocco is a third world country.

The visions they have for the bridge can be true, however. But that requires a owerthrow of the capitalist system, or at least a reform.

[Zoid]

Originally posted by Gatekeeper
The bridge proposal looks fascinating. Expensive, too, I imagine. Hmm ... what's the frequency of seaquakes in the Gilbratar area? It'd be a darn crying shame if the bridge were built, only to be knocked out of commissiion by a most ill-timed seaquake.

Gatekeeper

Seaquakes are non-existent AFAIK. The African Plate and The Eurasian Plate meet across the straits, but there´s no main fracture zone there (see pic). Thus it seems fairly stable IMO.

However, volcanism in this region has created giant linear volcanic ridges, notably those forming the Islands of S. Jorge and Pico in the Azores and the Canary islands. These are some of the largest such volcanic ridges actively forming anywhere on earth and represent an important mode of crustal formation, analogous to that observed at mid-ocean ridges.

This doesn´t affect the Gibraltar Strait though, geological conditions isn´t the biggest problem here.

[Zoid]

Originally posted by Ned
Why not a tunnel?

There was some talk of a tunnel a few years ago between Spanish and Moroccan authorities. It didn´t go anywhere IIRC. But this tunnel would only be a railway tunnel due to the technical diificulties with venting exhauste fumes.

The tunnel would be better stuff for Hollywood catastrophe movies though