CH: Earliest Possible Space Elevator

[John Fredrick Parker]

Pretty straightforward -- how soon could a space elevator be built, and what in the past century could have gone differently to make it happen sooner?

[KeeCoyote]

The real problem is making enough long enough carbon nano-tube filaments and then weaving them into wires thick enough that some bird or plane will not get sliced by the wires. So say about 2020 at the earliest /.

[arosenberger14]

An earlier discovery of carbon nanotubes (CNT's) is entirely plausible as the ability to produce and image them was available as far back as the '60s. Have them become popular 10 or 20 years earlier than OTL and you advance their development and composites by about a decade but you still need to wait for computers to catch up.

Still, it's a very, very tricky and expensive business. I'm a materials engineer so I'm pretty well acquainted with the issues of materials design that would need to be solved. Making a CNT based space elevator will take at least 30 years of development and design, assuming that the incentive even exists and it's cheap enough to be cost effective. For example, I believe that the composites used in the 787 took over a decade of research before they were commercialized. CNT's are like that x100. Personally, I'd be shocked to see a space elevator by 2050.

[John Fredrick Parker]

Originally Posted by arosenberger14

An earlier discovery of carbon nanotubes (CNT's) is entirely plausible as the ability to produce and image them was available as far back as the '60s. Have them become popular 10 or 20 years earlier than OTL and you advance their development and composites by about a decade but you still need to wait for computers to catch up.

Still, it's a very, very tricky and expensive business. I'm a materials engineer so I'm pretty well acquainted with the issues of materials design that would need to be solved. Making a CNT based space elevator will take at least 30 years of development and design, assuming that the incentive even exists and it's cheap enough to be cost effective. For example, I believe that the composites used in the 787 took over a decade of research before they were commercialized. CNT's are like that x100. Personally, I'd be shocked to see a space elevator by 2050.

Could the 1960's and 70's see more development of CNT, so that by the time Clarke, Heinlen, et el make the Space Elevator concept popular, they're quickly identifiable as the ideal materials? If this happens, how soon could TTL see the kickstarting the 30 years of development and design? And once that happens, how soon might this idea be developed enough to warrant a serious mention in, say, the US State of the Union?

[Dathi THorfinnsson]

Earliest Space Elevator Construction? - Alternate History ...

Space Elevator? - Alternate History Discussion Board



Alternate Space Launch Methods - Alternate History Discussion Board

(only tangentially about space elevators)


Sure, buckyballs and nanotubes could have been discovered earlier. So what? we still can't grow kilometer long nanotubes (or even meter long ones, AFAIK) , let alone weave them into a structure thousands of km long.

[GlennKGraham]

You might be interested in the ISEC Space Elevator Conference that's in Seattle next weekend (Aug. 25-27) http://www.isec.org/sec/index.php/technical-program.

Also, I recently published the first part of a sci-fi trilogy, entitled, "Sowers of God: The Holes of Mare Frigoris," which has a lunar Helium-3 mining operation (to provide fuel to the Earth's fusion reactors) that is supported by a Space Elevator. http://www.facebook.com/SowersOfGod.

[Jello_Biafra]

Honestly, I can't venture a guess about a classic space elevator anchored to a counterweight beyond geosync altitude, because that requires carbon nanotubes.

But an orbital ring is theoretically possible even with our current materials, since the "elevators" to connect to the orbiting ring only have to just breach the atmosphere. Then you use the same maglev system that allows the tower to be suspended from the ring to accelerate your cargo to orbital speed.

[anotherlurker]

afaik we have everything needed to construct a space elevator on mars, or the moon.

[Dathi THorfinnsson]

Originally Posted by Jello_Biafra

Honestly, I can't venture a guess about a classic space elevator anchored to a counterweight beyond geosync altitude, because that requires carbon nanotubes.

But an orbital ring is theoretically possible even with our current materials, since the "elevators" to connect to the orbiting ring only have to just breach the atmosphere. Then you use the same maglev system that allows the tower to be suspended from the ring to accelerate your cargo to orbital speed.

Ayayay.
hanging stationary towers off an orbiting ring? And you think this is easier? Ouch. The energy loss at each tower will be huge, and failsafes for a magnet failing, for instance, would be ... interesting.

Youd also need multiple towers, probably four plus, pretty much equally spaced around the world. Plus, balancing loads when something was going up or down the elevator would berl really, really tricky.

The ,,cheap,, solution, might be spaceprts like in donald kingsburys ,,the moongoddess and the son,, basically orbitting mass drivers that catch a suborbital rocket, and accelerate it to orbital speed. Thats still tricky, but easier by one or two orders of magnitude than your orbital ring.

[Jello_Biafra]

Originally Posted by Dathi THorfinnsson

Ayayay.
hanging stationary towers off an orbiting ring? And you think this is easier? Ouch. The energy loss at each tower will be huge, and failsafes for a magnet failing, for instance, would be ... interesting.

Youd also need multiple towers, probably four plus, pretty much equally spaced around the world. Plus, balancing loads when something was going up or down the elevator would berl really, really tricky.

The ,,cheap,, solution, might be spaceprts like in donald kingsburys ,,the moongoddess and the son,, basically orbitting mass drivers that catch a suborbital rocket, and accelerate it to orbital speed. Thats still tricky, but easier by one or two orders of magnitude than your orbital ring.

Easier than building something that requires building materials that do not exist.

The only reason I brought it up was because it was still technically a space elevator. Yours, while much more feasible, isn't really a space elevator.

[frlmerrin]

Youd also need multiple towers, probably four plus, pretty much equally spaced around the world. Plus, balancing loads when something was going up or down the elevator would berl really, really tricky.

If the mass and velocity magnitude of the elevator going up is approximately equal and opposite to that of the elevator going down and the mass of the elevator is small with respect to that of the cables and the mass of the cables are small with respect to the ring one would not expect this to be a particularly difficult system to load ballance.

But an orbital ring is theoretically possible even with our current materials, since the "elevators" to connect to the orbiting ring only have to just breach the atmosphere. Then you use the same maglev system that allows the tower to be suspended from the ring to accelerate your cargo to orbital speed.

At first glance this seems wrong the tensional loads in this would be the same as in a simple elevator design. Perhaps I have misunderstood the concept you suggest? Please could you explain a little more?

[Jello_Biafra]

Originally Posted by frlmerrin

If the mass and velocity magnitude of the elevator going up is approximately equal and opposite to that of the elevator going down and the mass of the elevator is small with respect to that of the cables and the mass of the cables are small with respect to the ring one would not expect this to be a particularly difficult system to load ballance.



At first glance this seems wrong the tensional loads in this would be the same as in a simple elevator design. Perhaps I have misunderstood the concept you suggest? Please could you explain a little more?

The problem is that the simple elevator has to be much, much taller. A simple space elevator has to go well past geostationary altitude of 35,786 kilometers, and be anchored to a counterweight of some kind. The classic space elevator is held aloft by centripetal force, with the counterweight being swung by the earth's rotation like a ball at the end of string.

The problem is that the force involved, and sheer weight of the tether would be astronomical. It defies the tensile strength of anything but carbon nanotubes, and as it was previously mentioned, we can't even make meter long carbon nanotubes, let alone 40,000 kilometer long ones.

With an orbital ring, the tower only has to to be around 130 kilometers tall, and can be supported at least partially by the centripetal force of the orbital ring by hanging it from the ring via a magnetic levitation mechanism.

[Herzen's love-child]

I really don't see the necessary technology development starting a whole lot earlier. The technology is the easy part. You need the capital, the political and commercial will and a damn good reason for such a mega-enterprise. I think it will require further baby-step commercialization of space before a serious SE project makes it off the CAD drawing board.
This is Future History in my view. 2050 or later sounds plausible.

[Dathi THorfinnsson]

Originally Posted by frlmerrin

If the mass and velocity magnitude of the elevator going up is approximately equal and opposite to that of the elevator going down and the mass of the elevator is small with respect to that of the cables and the mass of the cables are small with respect to the ring one would not expect this to be a particularly difficult system to load ballance.

But if the mass of the elevator going up is near the mass going down, you have little to no net lift to orbit. Which rather reduces the viability of your elevator.

As for the mass of the ring, youd probably need the mass LOCALLY to be much greater than the mass of the payload coming up, which, given that means that mass, linear density, has to extend the entire circumference of the earth, means a LOT of mass in orbit ... which you first have to get ther without a ring.

[Dathi THorfinnsson]

A skyhook, too, would make more sense. Think a orbiting at, say 400km with arms 300km long rotating at the precise speed needed so the end dipping down is briefly stationary. Theoretically, a suborbital craft can arrange to be there at that precise poimt in spacetime, dock, and be hauled into orbit as the arm continues to rotate.

The docking process will be left as an exercise for the reader

[Jello_Biafra]

Originally Posted by Dathi THorfinnsson

But if the mass of the elevator going up is near the mass going down, you have little to no net lift to orbit. Which rather reduces the viability of your elevator.

As for the mass of the ring, youd probably need the mass LOCALLY to be much greater than the mass of the payload coming up, which, given that means that mass, linear density, has to extend the entire circumference of the earth, means a LOT of mass in orbit ... which you first have to get ther without a ring.

Sending mass up on both sides of the earth would balance the load.

Besides, the mass of the ring is at slightly higher than orbital velocity so it's taught. That's a lot of angular momentum, which means the stress of lifting something will be tiny.

[frlmerrin]

With an orbital ring, the tower only has to to be around 130 kilometers tall, and can be supported at least partially by the centripetal force of the orbital ring by hanging it from the ring via a magnetic levitation mechanism.

Can you point me in the direction of some maths on the stability of this please?