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Why the world still awaits its first space elevator

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dcp123 in reply to nannite

You're worried that we have no power sources other than oil? I don't understand how that's possible for someone who, at least occasionally, reads the Economist.
Power supplies other than fossil fuel date back to at least the horse and electricity supplies other than fossil fuels are as old as electricity. Land transport can be electrified, as can heating.
Hydroelectric power is a thing, so is nuclear. Solar and wind are both scalable beyond our total power demand and are sometimes the cheapest sources of power. And if you're worried about rocket fuel, many of the biggest rockets ever made have used hydrogen and oxygen as fuel. If you have water and electricity, you can make those, or if you want to run a rocket designed to run on kerosene, which wouldn't have enough space to carry an amount of liquid hydrogen that could provide the same thrust, modifying it to work on other oils, including plant oils, shouldn't be a huge challenge.
The oil age will end, but not because we run out of oil just as the stone age ended without us running out of rocks.


Isn't the problem that available materials aren't strong enough for a cable of constant thickness to reach all the way down to Earth? Surely, if you ignore practicality, even a plain old kevlar rope that is suitably thick (miles in diameter?) could support a cable that tapered down to, say, an inch thick at ground level.

I doubt we'll ever find a material ten times stronger than carbon nanotubes, or that it will ever make sense to have a space elevator based on Earth, but I would be curious to know how thick a carbon nanotube rope would need to be at geosynchronous orbit to support a cable stretching all the way to Earth. A constant-thickness carbon nanotube rope (if you could make one) is reported to be strong enough support its own weight up to about 4700 km, but if it's thicker at the top than the bottom, this could go farther and, with a tapered cable that is thick enough at geostationarly orbit, it should be able to reach the Earth and my guess is that the cable would weigh a lot less than the moon, but a lot more than would be practical to lift to orbit.

dcp123 in reply to dcp123

I found an estimate that for kevlar the cable would need to be 260,000,000 times thicker at geosynchronous orbit than at ground level, so supporting a cable 1cm in diameter would require a cable 2,600 km in diameter at geosynchrounous orbit and I think that is with no excess strength for hauling cargo and a perfectly made cable.
For a perfect. Carbon nanotube cable I found a calculation of 1.9 times bigger at the thickest point (geosynchronous orbit) than at ground level. However, they said a real carbon nanotube rope constructed to avoid cascading failures from defective strands would be 70% weaker than that. Using their formula, my calculation (caveat emptor) for the taper ratio for a carbon nanotube cable made the way they suggest it would need to be is 33. So, a cable of 1cm at ground level would only need to be 33 cm at geosynchronous orbit. Of course, you need margin for error and it might be hard for a crawler to go up a cable that varied between us 1cm and 30cm, so you might need to hang some tracks on the thing, but even if you went with 4cm at ground level and margins for error and tracks pushed your ratio up to 100, that would only be 4 meters in diameter (if we knew how to make huge carbon fiber ropes). A cable about 35000km from earth to geosynchronous orbit and up to anothe 35000km beyond that varying between 4cm atthe ends and 4m in the middle would certainly be the largest thing ever made, but I dont see it as theoretically impossible using materials known to exist. Would it ever pay for itself? Probably not, but that's not the same as being impossible.
The article I read is on and is called "On the strength of the space elevator cable"

dcp123 in reply to Jonas_BsAs

It would cdrtainly have to be somewhat longer because a massat geostationary orbit would aplly no tension to the cable at all, but not necessarily twice as long. With a large enough weight at the end, it could be a lot shorter.

A longer cable would have some advantages. Cargo released at geostationary orbit would need thrust to move anywhere else. Cargo released at the end of a cable twice as long would have velocity far in excess of that needed to maintain orbit in that location. I haven't even tried an order-of-magnitude estimate, but I wonder if it would be fast enough to provide escape velocity


Since a geostationary object will have to have its mass center at 36000 km, a space elevator will more than likely have to be almost twice the length, ~72000 km long. This because the weight (mass) of the cable will almost certainly outweigh the station, or floor, with several orders of magnitude.

Ender Wiggins in reply to Comte Arnau

For spun CNTs and reference to the 63GPa try "The Space Elevator" by Edwards,2003. For one of at least several references on the long, strong CNTs try:
Zhang, R.; Wen, Q.; Qian, W.; Sheng, D.; Zhang, Q.; Wei, F., Superstrong Ultralong Carbon Nanotubes for Mechanical Energy Storage. Adv. Mater. 2011,23, 3387-3391
There are a number of references back at least to 2000 out of Los Alamos and Univ. of Cinncinati on growth of CNTs centimeters in length. CNTs of centimeters in length have been spun (Edwards book) by the same machines that spin cotton and make infinite threads with strength near the component fibers. Ren back around 1981 published on growth of arrays millimeters in length. This process has been used by myself and others to grow CNTs much longer and in quantities of pounds per batch.
These references and others can be found with a search on Research Gate and Google.


This is one of those projects where you have to assume that we find an energy source before the petrol runs out. Because its still 50-100 years away (at least), and in 50-100 years, there likely won't be any petrol left (cuz exponential growth, go look it up). If the petrol runs out, the neo-dark age people won't need this. Famines and genocidal world wars would occupy their time just fine.
But if they have a future power source, it would be sweet.


A nice dream, but correct, materials and reality are the problem[s]. Better to clean up our air, oceans, space [junk] and human conflict problems until...
We humans don't, so far, plan wisely ahead globally for diddlysquat.


An elevator from the Moon would be easier as moon´s gravity is six times lower (1.63 m/S2 compared to Earth´s 9.8 m/s2), but being the Moon 384,000 kms away from the Earth, it doesn´t solve any problem.


Pity the dismissal of the concept buries the idea of the space elevator's use on other bodies, like the Moon and Mars, where the materials will be strong enough. While space elevators are unlikely to work on Earth for the foreseeable future, the related technology of skyhooks is perfectly feasible from a materials standpoint.

chinachip in reply to nannite

I'm not running for election, worried about energy, or hoping for space elevators in our generation. BTW:
Do you think the Religions of the world should gather together in Union (UR) and work HARD to solve the worlds problems as the UN & EU [etc] do secular problems? Have a nice day.

Ender Wiggins

Carbon nanotubes have been produced and measured at strengths up to 200GPa which is three times the 63GPa needed to build the space elevator. Carbon nanotubes have also been produced at lengths up to 55cm long - much longer than the 2cm needed to spin them into an endless thread. This material has been around for 10 years. These same carbon nanotubes can be produced in bulk right now - my company is doing it. The only reasons we have not built a space elevator is 1) the ROI is 15 years and 2) bloggers keep repeating the same falsehoods that the material doesn't exist. This "article" is a reposted, poorly-written blog statement from years ago. If one of the writers would check their facts it would be nice.

nannite in reply to chinachip

Discussing the benefits of long chain hydrocarbons, their estimated volume in the crust and the the process that ultimately results in their final state of useless carbon x-oxide, won't get you elected. You especially won't get elected if you can also pull in the first and second law of thermodynamics and apply it to the carbon process-chain. Tying that energy back to life would just make you pariah.
"life requires energy, energy is limited"
George W. Bush said the US would go to Mars and now Trump is talking about getting us back to the moon.
Civilization Progmesses!


If the International Space Station is only 400miles (c600km) above the equator, a cable that cannot RELEASE deliveries at c6% of the way up to 36,000km is pointless.. so thinking on that if the elevator can be created, and a platform/ call it a FLOOR created at 600km, then its useful. But perhaps someone can explain if you forego geostationary orbit, and just target 600km, the issues....


Well, a real cable is a constraint however it might be a fictitious constraint. Why not consider other way to push the cabin. May be something as light in its many formats and sources. It would help to solve impact problems with spacecrafts. Why not consider something similar to a space sail craft that can be guided by a light tunnel?