Elevator Into Space

Vehicular transportation IS possible, however, and far more practical and reachable than a space elevator. I am not so much concerned about the possibility of the latter as much as the ramifications of any problems. What would happen should that cable break, say, a mile or so up. Wouldn't that cable still attacted to the ground prove incredibly dangerous as it fell? No material however strong would ever be "unbreakable," and the potential for danger exceeds anything the space program has ever done, because the potential for injury and death to those around would be so high.

I used to love flying kites as a kid, and my dad and I built one 6' high by 5' across. We had more than a mile of string on it, and it was the wind on the string that controlled the flight of the kite more than anything else. I would imagine that the wind would play even more havoc with something as big as a "space elevator."

Research could and should be done into developing either better fuels or more efficient engines for vehicular transportation. Look at what research has done for the computer industry.

I am not so much concerned about the possibility of the latter as much as the ramifications of any problems. What would happen should that cable break, say, a mile or so up.

Nor more so than the explosion of a launch vehicle on the pad... and probably less so. Even if it were to break 5 miles up, the area that would be impacted by the falling cable would be less than 5 miles from the anchorage... to the west. The range of fall would be easy to calculate and that area could be armored to protect against such an event.

Research could and should be done into developing either better fuels or more efficient engines for vehicular transportation. Look at what research has done for the computer industry.

There is a theoretical limit to the amount of energy that can be released by a chemical reaction... and we are approaching that already. The laws of physics are strict... we know the amount of energy it takes to raise 1Kg 100 miles... and what it takes to give it a velocity that equals the pull of gravity at that distance. If that was all we needed, then there would be little problem... but we ALSO have to raise the weight of vehicle AND reaction mass... and reaction mass for the reaction mass... and so on. The individual vehicle approach is the least efficient way of lifting to space.

Another theoretical approach is the "ferris wheel" approach... a modified form of the elevator. It also uses a long carbon-carbon filament, but it never touches the ground. Instead a two or four cable system in a cross, is rotating with the hub at the geosynchronous point. The "arms" rotate down into the atmosphere to be met by fast flying aircraft that attach and "ride" the wheel up into space. Return is accomplished similarly. "Catching" the wheel can occur at altitudes where jumbo jets fly, or even higher.

carbon nano-tubes are about an order of magnitude less than the required strength-to-weight

Strictly speaking, there is no minimum required strength-to-weight ratio. In theory, the cable could be built out of anything so long as it is tapered enough (i.e. the point where it meets the earth has to be strong enough to hold the amount of payload to be transported up the cable; higher points need to be progressively wider to carry the weight of the payload plus the weight of the cable up to that height). The catch is that the taper ratio is a function of the strength-to-weight ratio. Carbon nanofibers, if they can be mass-produced, brings the taper ratio down to the point of being merely difficult (something on the order of 100:1, IIRC) rather than downright prohibitive.

That's probably the only viable objection to the whole thing. Mechanically it's doable, financially it's doable, the only problem is its attraction to psychotics - i.e., a security issue.
Even that can be handled. There is a big incentive to secure a relatively small area - not particularly hard. And even if someone did manage to attack it, the damage done would be repairable: fixing the last mile of a 64,000-mile rope just kinda hanging there would just be a matter of churning out a little more rope from what made it in the first place.

It would also help if the owners made it unmistakable clear that they understood, and were willing to take advantage of, the ability to drop big rocks from very high up.

However, that is a social engineering problem beyond the scope of our discussion.

But again, the argument seems to focus on the elevator versus a chemical rocket. Who says the next fuel for space travel can't be some yet to be discovered? If we can imagine a fiber strong enough to stretch into space, why can't we imagine molecular transportation, faster-than-light travel, or vehicles powered by some unknown source of fuel? Each possibility has equal possibilities. People told the early aviators that flying was impossible, remember?

Granted, I am not a physicist, but I did take some classes in college and have done some reading into Stephen Hawkins, string theory and other theories of space and time. Here are some basic questions I have with all this:

If attached to the ground, would the cable or fiber bundle or whatever, flex or remain tight? If tight, wouldn't the anchors have to be incredible strong? Would they be so strong as to impose damage to the earth's crust or the plates? If flexible, wouldn't that make travel difficult or even dangerous? Wouldn't flexibility create the potential for binding?

Again I ask about the effects of the wind. Tall buildings are built to withstand the wind, even sway, but were talking about the potential of Jet Stream winds on this thing, which can and do change direction and are much more powerful. What about tornadoes or other earth storms. Building this thing out of carbon fibers, wouldn't that make it the world's biggest lightening rod?

I do like the ferris wheel approach, but now you have essentially defeated the point of the elevator in the first place haven't you? If it requires a chemically fueled vehicle to get the payload up that high, why not a little higher?

I have no doubt that science can and probably will come up with materials and the technology to build something like this. But I think in the process, wouldn't the science necessary to create it make it obsolete?

I am assuming that the carbon fibers, in addition to strength would have to be light weight. If so, then why not apply this technology to vehicular travel? Lighter, stronger vehicles mean more cargo capability. Plus vehicular travel could take place virually anyplace because it could start from anyplace; whereas, I don't imagine every city will have its own space elevator.

Strictly speaking, there is no minimum required strength-to-weight ratio.

I guess I'd quibble and say that it should be 'theoretically' speaking. If it's not technically feasible - for such reasons as taking a zillion tons of material and being a thousand miles in cross section at the critical point - well, I'd consider that a pretty strict limitation.

My own recollection is that even carbon nano-tubes are still 'downright prohibitive', but that includes a recognition that - for something that would wrap clear around the earth and with a hellacious impact if it fell - we'd need factors of safety more akin to bridges and dams than to aircraft or spacecraft. That's a judgment, not a law of physics, but it means we're still a ways from being ready to start. (*smile*)

I've read Sheffield's "Web Between the Worlds" and Clarke's "Fountains of Paradise". Of the two, Sheffield's book does a much better job of portraying the engineering challenges.

And both basically just assumed materials that were strong enough to do the job.

For those that might be perusing old threads:

The August 2005 IEEE Spectrum has a detailed article written by Edwards from Carbon Designs on the Space Elevator. There seems to be some new points regarding the technology:

The elevator would be ribbon shapped - wide and VERY thin. Simplifies the technology needed to grab and move along it and minimizes potential damage from space debris, micrometeors and the like. The elevator would go up at 190 mph.

To build the elevator would require an unbelievable amount of current rocket launches (5 ton payload per, and need to get hundreds of tons to build the elevator). Alternatively, we'd build a smaller elevator to be used for the construction phase.

The bottom would be anchored on an oil-drill like ocean platform that could be moved a kilometer this or that way, to move the ribbon out of the way of things that may damage it... satellites, debris, etc.

The location of the bottom would be near the Galapagos islands, which would minimize the problems related to weather - tornados, hurricanes, lightning, wind, air traffic.

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