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Calling the Space Elevator
CornfedPig writes "SPACE.com has an article that suggests building an elevator to a 100,000 km-high penthouse could be possible within the next few years at a cost of about $5B US. Widespread availability of low-cost carbon nanotubes appears to be the gating factor. Existence of such an elevator could drop the cost of lifting things (satellites, people, CowboyNeal) into orbit to a couple of hundred dollars a pound. Anyone remember Clarke's The Fountains of Paradise?" Space elevator stories come along every few months; we never seem to be getting any closer to actually doing it. I imagine it will happen at some point in my lifetime, but...
This is the type of thing that would have to be so heavily guarded that it would be a serious pain in the ass to use. There would most likely have to be some sort of wide radius no fly zone around it, as well as a very invasive search for anyone wanting to ride up. Very soon the reasons for not doing this will no longer be technical, but rather political and organizational.
When I want your opinion I will beat it out of you.
Whenever I look at the Towers of light and the enourmous hight which it rises into the atmosphere.. I wonder if this is what a space elevator will look like. One of the striking things about it is how far the light penetrates into the upper atmosphere. From my rooof, 2.5 miles away, I was able to get a fix on the angle to the top and place the highest point I could see at about 15 miles up!
For those of you who do not live out here, all I can say is that tv and photos simply do not do memorial any justice. It provides a humbling sense of scale when looking up into the infinity to which it rises.
Ok, I admit it, I submitted the slashdot story before last on this topic, and I linked to the same paper that was mentioned in the next story, and this article is a piece on the same guy who wrote the same paper.
Technically, the bottom line is:
No we can't do this right now. The fibers aren't strong enough to do this without bankrupting the global economy. An exponentially tapering fiber can theoretically do this at any time, but it would be wayyyyyy too big and heavy to install. (e.g. a steel cable would be ~hundred meters wide at the thickest point, and >38000km long...)
For the suggested construction technique, the carbon 'rope' needs to be able to give 72.5 Gpa strength, plus safety factor (typically 2). A single fiber gives about 73 Gpa right now. So we've no safety factor at all... but:
Joining the individual fibers together- nobody has done this whilst maintaining enough of the strength. Splicing normally soaks up 15-30% of the strength, and so we're now 15-30% down on the required strength, and nobody has even managed to do splices this good with carbon fiber.
Only a little percentage off then, but this pushes the mass up incredibly when you do the maths.
Still, we're very close. 3 reasonably simple(?) breakthroughs (one to gain strength, one to splice the rope, one to actually scale up production from one 3cm fiber to trillions of 3cm fibers in a reasonable time) and we're saying 'Hi!' to the rest of the solar system.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Correct me if I'm wrong, but doens't using a space elavator to lift things steal from the angular momentum of the earth? I mean, you'd only lose a negligable amount from lifting satellites, and space stations, but CowboyNeal? I don't want to end up on the "permanant dark side of the earth".
No, the theory is sound, the initial fiber would only weigh 20 tonnes, if you can achieve the necessary strength which right now we are a smidgen short of. The cable is very thin and flexes easily, so the lunar tidal forces are no problem. The paper says it would be built on an oil rig type structure on the equator, well away from dry land, so NIMBY is obviated.
Voltages? I don't think anyone knows what would happen with that, as far as I know it wasn't mentioned in the original paper either. It might be soluble. Lightning strikes could spoil your whole day that's for sure.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"If we had a few hundred space elevators on the planet, how long would it take before we could move the entire mass of our planet into space?
Given the length of time your ride on the space elevator and for the consideration of others. PLEASE do not ride the elevator after eating mexican food.
Thanx,
-The managment
"as plurdled gabbleblotchits on a lurgid bee" - Prostetnic Vogon Jeltz. (One man's humorous is another mans flamebait)
I have read the same paper you talked about in your previous post. The writer does mention lightning strikes and discusses a few solutions.
One solution is that the place where he proposes building it has on average 3-4 lighting strikes per year which is the lowest in the world. It also has the lowest number of storms in the world per year. Also, ocean currents make a sort of tidal pool area and hurricanes do not go into this section of the Pacific.
Another nice thing about the design is that it will not be nearly as destructive as what everyone thinks of when they mention falling space elevators. One of the requirements for the glue for splicing the nanotubes is that it have a melting point that is below the heat experienced in re-entry. This means that all of the re-entering elevator except for the lower 60 to 100 miles of it will break up into little pieces each less than 10 cm in length and they will burn up on re-entry. The 60 to 100 miles that does not will fall into some of the emptiest ocean in the world.
Also, to deal with winds, the shape of the cable is a cresent shape designed to face into the wind so that it does not flutter.
As Mr. Clarke says "A space elevator will be built 20 years after everyone stops laughing."
I'm not laughing, are you?
Are there any astro uber geeks that can comment on the stability of this system from the standpoint of
- small changes of mass from the upper end of the elevator (like from space objects hitting and sticking, etc.)
- small oscillation modes (rubber band like) in the connecting fiber
Otherwise, I'd be Real Nervous® about having the base station of the elevator anywhere near MyBackYard."Provided by the management for your protection."
'Buckytubes' (I hate that name) are within an order of magnitude of the strength required.
The suggested building method is to put a bulky object (eg captured asteroid) in geosync orbit and lower the cable down, moving the 'roid back up slowly to ensure the centre of mass remains geosync.
How thick do you think this thing'll be? I think that it *not* being visable is going to be a larger problem. ISTR that the core will only be of the order of a few centimetres diameter, you'd not see it at 100m, hardly a problem across "much of the Earth's surface"
Voltage potential? You think the Earth circles the Sun because we're +ve and it's -ve? The only real issue would be a conductor moving through the Earth's magnetic field.
You should call yourself PhysicsTroll, not PhysicsGenius...
-Yarn - Rio Karma: Excellent
A factor in space launches IIRC is the wind velocity in the upper atmosphere, which at times can reach hundreds of knots. I also recall that the high wind velocity was a factor in the post-explosion breakup of the Challenger space shuttle.
Although the atmospheric density and pressure is much lower at these altitudes (50-1000km+), the wind force is a factor, and it makes me wonder how a geo-stationary elevator shaft could be designed to withstand the energy of such wind forces.
If it could work, it'd probably kick off a revolution in space industry.
Big Daddy, Johnny, Burp, Aunt Zelda, Scott, Slurp, Big Momma
As other posters have noted, we don't have any
materials strong enough for an elevator all the
way to geosynchronous orbit, so it's a bit too
soon for anyone to claim we could build one in
the next 10 years.
HOWEVER, we do have materials strong enough for
a "hypersonic tether". This'd be a much shorter
tether, only a few thousand km long, and moving
at a good clip around the Earth, with the lower
end just above the atmosphere.
With this in place, you could use cheap sounding
rockets, just barely capable of making it out of
the atmosphere, to rendezvous with the tether as
it swept past. The cargo would be grabbed by the
tether and snatched up into low orbit, while the
sounding rocket fell back to Earth.
There aren't any good online references, but you
can find USENET discussions of the technology on
Google Groups, keywords "hypersonic tether".
>;k
You are talking about orbital towers. That is an outmoded idea.
:-P We would use ultra-strong carbon nanotubes. About 60 times as strong as steel.
We will probably use a superstrong nanotube rope, instead. It would go out past GEO orbit. A weight, such as a smallish asteroid or something, would tethered past GEO. This would create tension on the rope, due to the counterweight wanting to fling off into space. This way, you would need no tower.
Tidal forces of the Earth on the structure call for superstrong material. Side tidal forces from the moon require it to be flexible as well.
Really? We would need a superstrong material to build 50,000 miles high?
How do you build it? Not in place...
We pretty much know how to do it. We just have to improve our carbon nanotube manufacturing process.
Imagine that thing towering over your neighborhood. Pretty scary. Now realize that it is going to be visible from much of the Earth's surface and add NIMBY into the equation.
It would be extemely doubtful that it would crash. With the counterweight, should it become detached from the ground, it would fly off into space!!! Also, this thing is badass. IWLTH1IMBY(I would love to have one in my backyard)
The voltage potential from top to bottom is going to make this thing deadly deadly deadly without ultra-secure precautions.
You mean, kind of like a powerline??? If you touched a powerline you would be just as dead, if not moreso. Just put a fence around it.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
Also, BTW, geo orbit is at 24,000 miles, I believe. The further you put the counterweight out, the smaller it needs to be. That is why 50,000 miles is a good length. As an added bonus, you can launch spacecraft off the end. A spacecraft launched from the end of the rope would fly off into space at an extremely high rate of speed. This concept is called tethers. It's just like if you swung a bola around your head and let it go, it would fly off and hit somebody in the head real fast.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
You mean like the exclusion areas that (25 miles, IIRC) that are already established and working around launch areas? (And that were patrolled on launch days before 9/11).
If you read the article, the current proposal is to put the earthside connection somewhere on a platform in the middle of the Pacific Ocean -- this should not be that difficult to handle.
One solution is that the place where he proposes building it has on average 3-4 lighting strikes per year which is the lowest in the world.
The problem with using ONLY this solution is that, seeing as this is nothing but a giant grounding wire, every single of those 3-4 lighting strikes would hit the elevator.
"Your superior intellect is no match for our puny weapons!"
What i want to know is, would this be a good thing to invest it? They say it will cost $5bn, so they need money from SOMEWHERE, right?
So say if i had a significant amount of money.. like $1million (hell, $500,000 or $100,000) and invested in the construction of this thing (or invested in a company that is constructing it by buying shares), would this be a wise investment, with good return?
Would direct investment by supplying monies for construction and then demanding a % share of profits operating the elevator forever into the future be better then just buying shares in a company that is producing the elevator?
Any thoughts?
I'm always wondering what would be a very good sure bet for investment with VERY good returns, and something like these seems to be an ultimate one. The benefits of a space elevator are simply amazing, and the elevator will be in use for decades if not centuries, until replaced by something better, or a better elevator..
Martin.
You can tell how powerful someone is by the magnitude of the crime they can commit and be able to get away with.
"Oh, hello Mr. Tyler. . . going down?"
!#@%*)anks for hanging up the phone, dear.
20 years might be plausible, but the actual quote is "50 years after everyone stops laughing."
;-)
I've stopped laughing by the way. So clock is ticking.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"In his book 3001, the Earth's equator is studded with a series of tethered space platforms. Clarke's vision of these things includes a lot of interesting detail that I suspect is accurate.