What ever happened with this idea ( A.C.Clarke) ? The last I heard carbon fiber technology was showing a lot of promise but I haven't heard anything about it in years .
@ Dukedog said in #1:
> What ever happened with this idea ( A.C.Clarke) ? The last I heard carbon fiber technology was showing a lot of promise but I haven't heard anything about it in years .
Well, I haven't heard anything about it.
But judging by the title alone, I guess it was a planned elevator to, well, space. Or at least near to earths orbit. Maybe to a space station?
After checking the wikipedia article briefly, it seems that there's more to it than meets the eye. Well, I guess I know what I will read about the next half an hour.
> What ever happened with this idea ( A.C.Clarke) ? The last I heard carbon fiber technology was showing a lot of promise but I haven't heard anything about it in years .
Well, I haven't heard anything about it.
But judging by the title alone, I guess it was a planned elevator to, well, space. Or at least near to earths orbit. Maybe to a space station?
After checking the wikipedia article briefly, it seems that there's more to it than meets the eye. Well, I guess I know what I will read about the next half an hour.
@george_mcgeorge said in #2:
> Well, I guess I know what I will read about the next half an hour.
Grab your other book!
> Well, I guess I know what I will read about the next half an hour.
Grab your other book!
I guess we have to wait at least 28 years. Who's got the time for that?
@Dukedog #1:
> The last I heard carbon fiber technology was showing a lot of promise but I haven't heard anything about it in years .
Well, that really depends on who you ask and what you mean by promising. Carbon fibres are somewhat promising in that they have sufficiently low density (1300 kg/m^3 optimistically) and sufficiently high tensile strength (1.3*10^11 Pa optimistically) to give scientists and engineers some sliver of hope that a space elevator might – just barely – be physically possible (some authors conclude that is, others that it isn't possible yet). Whether or not it would be practical (useful, economically viable, etc.) to build one is another question.
What's a space elevator?
A space elevator would basically be a very long, tapered tether – attached to Earth's equator – whose cross-sectional area "exponentially increases with height from ground level to geostationary height", 35,786 km (22,236 miles) above the surface of the Earth. Then its cross-sectional area exponentially decreases with height from geostationary height to the height of a (large) counterweight (probably at a height of about 100,000 km).
The tether would be tensioned by the centrifugal force (when analysed in the rotating [and therefore accelerated and not inertial] frame of Earth's surface) acting on the counterweight and the system's overall center of mass would be above geostationary height. Thereby making the system stable.
At least that's the idea. Practically it would be extremely challenging. Most candidate materials (steel, Kevlar, etc.) that the tether could be made of can easily be ruled out because the ratio of their density and their tensile strength is way too large; a tether made from these materials couldn't withstand the tension (or would require astronomically large cross-sectional area in order to do so).
Why build a space elevator?
Because it would rid humanity of the tyranny of the rocket equation. Rockets need to carry fuel in order to deliver their payload to its destination. However, this fuel is a payload itself. Part of it has to be delivered to points along the way to the destination as well. You need fuel to carry the fuel needed to carry the payload. That's why rocket payloads are so small compared to their overall mass. Rockets are ≈90% fuel.
A space elevator would come in really handy. You could ship fuel and rocket components to the counterweight at the top via a cargo robot climbing up the tether (or a cargo elevator electrically being pulled up along the tether). The counterweight could be a space station or space terminal. Starting rockets and spacecraft from there would be very convenient, because they would barely need any fuel in order to escape the Earth's gravity from up there. They would also start with a hefty amount of initial angular momentum which would make interplanetary travel fairly easy. Great!
That's the potential pros. There might also be cons (especially if the tether were to be ripped apart). They are (shortly) addressed in the paper linked below.
I found this 2006 paper an enjoyable read (especially the concluding remarks). You don't need to understand the derivation of every single equation if your goal is simply to get the big picture. The text alone explains things fairly clearly.
users.wpi.edu/~paravind/Publications/PKASpace%20Elevators.pdf
It concludes: "Only the future will tell when, and in what form, the space elevator might eventually be realized."
And future hasn't told us yet :-)
> The last I heard carbon fiber technology was showing a lot of promise but I haven't heard anything about it in years .
Well, that really depends on who you ask and what you mean by promising. Carbon fibres are somewhat promising in that they have sufficiently low density (1300 kg/m^3 optimistically) and sufficiently high tensile strength (1.3*10^11 Pa optimistically) to give scientists and engineers some sliver of hope that a space elevator might – just barely – be physically possible (some authors conclude that is, others that it isn't possible yet). Whether or not it would be practical (useful, economically viable, etc.) to build one is another question.
What's a space elevator?
A space elevator would basically be a very long, tapered tether – attached to Earth's equator – whose cross-sectional area "exponentially increases with height from ground level to geostationary height", 35,786 km (22,236 miles) above the surface of the Earth. Then its cross-sectional area exponentially decreases with height from geostationary height to the height of a (large) counterweight (probably at a height of about 100,000 km).
The tether would be tensioned by the centrifugal force (when analysed in the rotating [and therefore accelerated and not inertial] frame of Earth's surface) acting on the counterweight and the system's overall center of mass would be above geostationary height. Thereby making the system stable.
At least that's the idea. Practically it would be extremely challenging. Most candidate materials (steel, Kevlar, etc.) that the tether could be made of can easily be ruled out because the ratio of their density and their tensile strength is way too large; a tether made from these materials couldn't withstand the tension (or would require astronomically large cross-sectional area in order to do so).
Why build a space elevator?
Because it would rid humanity of the tyranny of the rocket equation. Rockets need to carry fuel in order to deliver their payload to its destination. However, this fuel is a payload itself. Part of it has to be delivered to points along the way to the destination as well. You need fuel to carry the fuel needed to carry the payload. That's why rocket payloads are so small compared to their overall mass. Rockets are ≈90% fuel.
A space elevator would come in really handy. You could ship fuel and rocket components to the counterweight at the top via a cargo robot climbing up the tether (or a cargo elevator electrically being pulled up along the tether). The counterweight could be a space station or space terminal. Starting rockets and spacecraft from there would be very convenient, because they would barely need any fuel in order to escape the Earth's gravity from up there. They would also start with a hefty amount of initial angular momentum which would make interplanetary travel fairly easy. Great!
That's the potential pros. There might also be cons (especially if the tether were to be ripped apart). They are (shortly) addressed in the paper linked below.
I found this 2006 paper an enjoyable read (especially the concluding remarks). You don't need to understand the derivation of every single equation if your goal is simply to get the big picture. The text alone explains things fairly clearly.
users.wpi.edu/~paravind/Publications/PKASpace%20Elevators.pdf
It concludes: "Only the future will tell when, and in what form, the space elevator might eventually be realized."
And future hasn't told us yet :-)
Thanks,informative article. Last I had read was in Popular Science in the early days of carbon fiber research (materials technologies).Back then nanotubes hadn't been invented yet and the big idea was buckyballs.
Some country is trying to do this now. MAybe Japan or even the Saudis ... it'll never work ...
Honestly I prefer the skyhook.
skyhook better
spinlaunch tho
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