Slashdot Mirror
The Space Elevator
As a child in the late 60s and early 70s, some of my earliest memories are TV images of the moon shots, the sense of excitement and adventure, and confident assertions by adults that this was only the beginning, that progress was indeed unstoppable, and that it was a near certainty that by the time I was old enough to ask a girl out on a date, the question "would you like a ride in my spaceship" would be greeted not with derision, but with awe. Of course the sad reality is that none of this has come to pass. Space has remained dangerous, expensive, and inaccessible to all except the rare test pilot, scientist, or those for whom capitalism has been unusually kind. Luckily, there are some promising new ideas in space transportation that could represent the breakthrough we have been waiting for in the years since walking on the moon became passé.
In their new book The Space Elevator, Bradley C. Edwards and Eric A. Westling present a compelling argument, backed up with a great deal of quantitative analysis on both scientific and economic grounds, that a space elevator is near-term-feasible. The authors argue that carbon nanotube fibers are both strong and light enough that a 100,000 km elevator, constructed of a 2m wide carbon nanotube "ribbon," could be constructed in 10 years for a cost of US $6 billion, and be capable of lifting a 13-ton payload to geosynchronous orbit once every few days. If feasible, it would present a stunning breakthrough in space accessibility, and likely usher in a new age of space development and exploration.
Edwards writes in the forward:
One day, a few years ago, I read a statement that the space elevator couldn't be done, and I set out to find out why. From there, things got very interesting and resulted in a research proposal being submitted to NASA. The proposal was funded and resulted in, first a six-month study and then a two year study. The core of this manuscript started out as the technical report from the six month investigation I conducted for NASA under the NASA Institute for Advanced Concepts (NIAC) program.
Edwards and Westling begin the book with some history. Until recently, it was thought that alternatives to chemical rockets as a means to reaching LEO (low Earth orbit) were, at least for the foreseeable future, the stuff of science fiction. The idea of a space elevator, foreseen as early as 1903 by the brilliant Russian science speculator Konstantin Tsiolkovsky, foresaw a tower to geosynchronous orbit and beyond.
He was the first to identify the concept that the part of the tower beyond geosynchronous orbit would have an outward "force" due to Earth's rotation that would support the portion of the tower below geosynchronous altitude.
Essentially a space elevator is a geosynchronous satellite with an unusually high aspect ratio. So high, in fact, that even though the satellite is in orbit over a fixed point on the Earth's surface, the lower portion of the satellite actually touches the surface of the Earth. The key, of course, to making this concept workable is to find a material that has the tensile strength to withstand the extreme forces that such a tower or cable would be subjected to. Though a space elevator would need to reach 35,785 km to geosynchronous orbit, since gravity drops off as the square of our distance from Earth, we can collapse the 35,785 km down to its equivalent height as if it were all in 1g, giving 4940 km. This magic number represents the self-support height that a space elevator cable would need to exceed. The self-support height is the maximum length of material, formed into a cable, that can support its own weight in a 1g gravity field before breaking, and can be calculated by dividing tensile strength by density.
It turns out that a steel cable has a self-support length of 54 km, graphite whiskers (fibers) 1050 km, and carbon nanotubes 10,204 km. This last figure is an important result that shows that carbon nanotubes are significantly stronger than would be needed to build a space elevator. The difference between the 4940 km minimum self-support length and the carbon nanotube self-support length of 10,204 km all translates into significant payloads that could be lifted into space using this technology.
So if the space elevator is feasible right now for only US$6 billion (less than half of NASA's annual budget), why aren't we building one ASAP and preparing to retire the shuttles? The answer is that carbon nanotube technology is so new (invented in 1991) that we haven't yet created the infrastructure for mass production. In fact, the authors admit that we haven't even created a nanotube in the lab that demonstrates the requisite strength. While carbon nanotubes have a theoretical tensile strength of 300 GPa (billion newtons per square meter), strengths of only 11.2 to 64.3 GPa have been experimentally measured thus far. Edwards and Westling have heavily based their thesis on nanotubes reaching a tensile strength of 130 GPa in mass-produced volume, so they are to some extent reaching for the future here. Clearly they are counting on a kind of Moore's law to kick in, where the efficiency to cost curve of nanotube production improves exponentially as breakthroughs are made, then asymptotically slows as the theoretical upper bound is approached.
Now assuming that we can economically mass produce carbon nanotube ribbon at a strength of 130 GPa, what's next? Here Edwards and Westling present a well-researched plan for turning the raw material of the carbon nanotube into a functioning space elevator within 10 years. An initial kind of bootstrap cable would be lifted into LEO on board several trips of the space shuttle. This cable would be constructed of carbon nanotubes arranged in parallel with a reinforcing cross-connect adhesive, so that if a nanotube was severed, the remaining tubes would take up the load. The cross sectional dimensions of the cable would be highly asymmetrical, 1 micron in thickness, 13.5 to 35.5 centimeters in width, hence the cable is referred to as a "ribbon". After some assembly in LEO, the initial ribbon and deployment mechanism would be integrated into a spacecraft and sent to geosynchronous orbit, where it would deploy by basically unwinding the spool of ribbon towards Earth, while the spacecraft-spool assembly itself is boosted higher to maintain the total system in geosynchronous orbit. Once a few km of ribbon is unspooled, gravity gradient forces will kick in, ensuring a stable vertical orientation as deployment proceeds. Eventually the end of the ribbon would reach Earth where it would be anchored to a mobile sea-platform, located near the equator, which would have the capability to move the lower end of the cable to dodge known space-junk and electrical storms.
This prototype space elevator will be relatively weak and vulnerable to damage from meteoroids and uncharted space junk, so it will be essential to quickly strengthen the ribbon by widening it. Edwards and Westling's plan calls for "climbers" (electric-powered vehicles that climb the ribbon using a mechanical traction drive) to immediately ascend the ribbon, splicing additional carbon nanotube material onto the existing ribbon, then permanently parking at the far end of the ribbon to add to the elevator's counterweight mass. After 230 iterations of this process, the ribbon will be complete, 2m wide and capable of lifting 20 tons of climber + payload.
Getting a 100,000 km space elevator into position and insuring its survival is a daunting engineering challenge, and much of the book is dedicated to answering what-if scenarios and attempting to prove to the skeptical mind that such an ambitious undertaking is feasible. To this end, each space elevator subsystem is analyzed at length and competing solutions are evaluated for cost and efficiency.
For example three different methods for supplying electrical power to the climbers are evaluated:
- run power up the cable,
- beam power via microwave, and
- beam power via laser.
Answer: use a laser.
An optimal shape (i.e. taper profile) for the ribbon is proposed, so that the part of the ribbon in the atmosphere is narrow to minimize wind-loading forces and the section between 500km and 1700km is widened and slightly curved to maximize survivability from meteoroid or space junk impacts. The destructive effects of wind, lightning, atomic oxygen, debris impacts, radiation damage, and ribbon oscillations are considered and solutions are presented. The conclusion: none of these adverse effects are show-stoppers.
Some basic FAQs are presented and answered, such as where does the energy come from to accelerate a climbing payload on the ribbon to orbital velocity. Answer: from the rotational inertia of the planet. If we shipped a whole continent into space, our days would get a bit longer.
After a comprehensive technical and engineering analysis of the space elevator concept, the authors move on to the economics of the concept and present a sort of skeletal business plan for "Space Elevator, Inc." They present many interesting uses for the space elevator including energy applications that could significantly improve the environment and reduce the combustion of fossil fuels. If the space elevator succeeded in reducing launch costs below $100/kg, large orbiting photovoltaic arrays might be built in space that would collect power and beam it to Earth via microwaves. These ideas are far from new (such an apparatus was patented in the early 1970s), but the reduced launch costs of the space elevator make them far more feasible.
The authors take a detour in explaining some promising results on the nuclear fusion front. Progress on the reduced-radiation IEF concept (Inertial Electrostatic Fusion) for fusion reactors would be accelerated by 3HE mining on the moon, which the space elevator would make feasible.
The rationale for building the ribbon up to 100,000 km is examined. The major advantage of such a tall ribbon is that the centripetal acceleration of the ribbon tip is substantial enough that payloads could be flung to Venus, Mars, or the asteroid belt with little additional energy expenditure. This, the authors argue, would bring down the cost of robotic planetary probes to the point where individual universities could afford their own space programs.
And finally, a working space elevator can be used to manufacture new space elevators at a much lower cost than the initial implementation. The authors suggest that the first significant commercial application of the space elevator might simply be in making additional space elevators and selling them to commercial clients. In this manner, elevators with payload capacities up to 200 tons could be deployed using wider ribbons, making possible a large-scale human presence at geosynchronous orbit and bringing the kind of commercial activities that would go along with that, such as tourism.
The book ends with a flight of fancy of sorts into a future where space elevators have become commonplace. Space elevators around Mars create an efficient Earth-Mars transportation network. Elevators on the moons of Jupiter throw spacecraft down into Jupiter's turbulent upper atmosphere to scoop up 3HE and ship it back to Earth in decade-long space convoys where it will power the latest and greatest IEF fusion power-plants.
While The Space Elevator goes a long way towards convincing skeptics of the feasibility of the general idea, the big question marks that remain in my mind are:
- Will carbon nanotubes really reach the 130 GPa level in cost-effective mass production that will be required for elevator construction?
- Much of the elevator deployment plans depend on the flawless execution of robotic mechanisms controlled remotely from Earth, including the trip from LEO to geostationary orbit, the deployment down to Earth, and the subsequent strengthening of the ribbon by robotic climbers that splice additional nanotube material onto the existing ribbon. As we learned with the Hubble Space Telescope, it is essential to have astronaut access for unexpected but critical repair missions. But much of the space elevator deployment will take place above LEO, out of access of human shuttle missions. What do we do if there is a glitch during deployment that requires an astronaut repair? We will need to seriously address such contingencies, lest we get saddled with a stuck elevator that could become the mother of all space junk.
- Have there been any successful tether missions to date in space? While the answer appears to be yes, I would have liked to learn more about them.
Doubts aside, this is a compelling work that will likely become both a manifesto and bible for the space elevator movement, presenting a convincing argument that the space elevator is our best chance yet to bring Moore's law economies to space. It is an engaging read and I highly recommend it.
Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Read Terry Pratchett's Science of Discworld books for more information on this......
Kingdom of Loathing (www.kingdomofloathing.com) Addicted is me
Good Lord - the amount of Muzak one would have to listen to on the trip to the moon should be enough to stop a project like this in its tracks!
... now I don't need to buy the book!
Honestly, that was more of a synopsis than a review dont'cha think??
A little planning goes a long way...
when my flying car will get me there faster?
-- www.globaltics.net
Political discussion for a new world
The whole space elevator thing is a conspiracy being run by The Illuminati. They plan to run wires up within the elevator shaft providing an unparalleled antenna for their mind control rays. At the top they are going to have a lounge and war room from which they can watch their world and plan our lives.
Call me paranoid all you want, but it's about time the trut... oh just a sec, there's someone at my door...
Trolling is a art,
I dont know about you guys, but the whole concept seems flawed from the start. How about maintenance? What if the payload falls? I dont want to live anywhere near this thing....
Why does Bush not say that his goal for America is to construct this during this decade? (similar to JFK, etc)
This time in our history will be looked back at for terrorism, war, and world diplomatic struggles. Why not unite and construct something of this magnitude to unite us all? I am sure the terrorist strikes will stop themselves if the US gains a reputation for a R&D and science nation instead of a warring and military nation. If the U.S. put a 6 month hold on current military spending on new aircraft/ships/etc they could afford this construction 10 times over.
[I can picture a world without war, without hate. I can picture us attacking that world, because they'd never expect it]
NASA already is funding this kind of research. They have already invested $600,000 into Seattle-based company High Lift Systems, according to a BBC article.
Sounds to me the right thing to do -- invest in other companies to do the ground work, and see if it really is viable. If not they go bust -- Oh well. If it goes well, then great!
than the World Trade Center. Imagine planeloads of terrorists and religious extremists trying to make their point by colliding with the "elevator". Heck, for that matter imagine some unwitting student pilot in a Cessna.
No one ever had to evacuate a city because the solar panels broke!
I know this subject has been cover before on slashdot. I think the idea is awesome. Of course I can't figure out how this all works I assume that the tip of the elevator would have to be massive and be travelling pretty fast. It would eventually sink back down to Earth just like the ISS does (it needs a boost back up every now and then).
Maybe this sounds like a great book to understand all that. I might just go pick one up here.
How exactly do you supply the amount of fuel required to something like this at the rate required? Do we even have propulsion systems able to generate a fraction of the amount of thrust needed?
- This and all my posts are public domain. I am a Physicist. I am not your Physicist. This is not Physically advice
The good reason to reach for this which can't be emphasized enough in the current environment is that for a relatively modest investment, the impact on the economy would be enormous (and good). Compared to other proposals to jumpstart the economy, this one has incredible bang for the buck.
Obviously this isn't a short-term, instantaneous fix, but this is exactly the sort of project that something like the United States should undertake to help maintain its lead in the economy, if it is interested in maintaining it. The economic advantage of having the only working space elevator (even if it was only until we could build another for someone else, assuming optimistically we wouldn't build ourselves a few backups first) in the world would be absolutely incredible.
Considering the price, it's complete foolishness not to pursue this, even if common sense says the opposite. And the best news of all is that carbon nanotube research is interesting enough on other, more commonly-sensible grounds, that it's going to continue anyhow.
Another thing that should be emphasized is "Suppose China gets there first." Personally, I'd love to see a space race over this issue. It would be one hell of a lot more productive over the long term then the moon race was!
Sheesh, evil *and* a jerk. -- Jade
Even if the space elevator could be built, how would one defend it against terrorism. It would be kind of a big target at 22,241 miles high.
-- Thou hast strayed far from the path of the Avatar.
Getting rid of our garbage -- do you know how much cleaner cities could be if we could just send garbage to the sun???
File under 'M' for 'Manic ranting'
So good, in fact, that I don't need to read the book. Thanks James! :)
There are a series of SF books by Kim Stanley Robinson, titled Red Mars, Green Mars and Blue Mars.
Space elevators are part of the story, and the sabotage of a space elevator on Mars results in catastrophe. I recall that the sabotage involved the cable being detached from the space station end. The space station flew off into space, and the cable fell back to ground, wrapping itself around the planet's equator.
Newby question here (IANAPhysicist), but wouldn't the elevator be a heavy load on the satellite supporting it? Wouldn't it exert a force downward towards the earth, thereby forcing it to continuously pull up to counter that force?
Let's hope this space elevator's fibers are a little more sturdy than the mast of Team NZ's yacht.
"AUCKLAND, New Zealand The meltdown of Team New Zealand, the America's Cup defender, continued on Friday when, on the third leg of Race 4 against the Swiss boat Alinghi, the Kiwis' mast exploded into a heap of carbon fiber shards."
(NYTimes)
I totally believe that Space Elevators are feasible in the near term. However, my concern is with whether we should. Is there a compelling enough reason that outweighs the risks involved to actually go and build one of these?
What risks you may ask?
Well, sure, shuttles are quite expensive to launch and are not flawless by any means. But what was lost recently? 7 lives, a bit of research and a relatively moderate chunk of change.
Ever thought about the effect of a disaster with one of these elevators? Use your imagination. Now remember that you have to use your imagination to even allow the concept of these being built so you can't just write off the possible effects of a catastrophe just because it's unlikely or far fetched...the whole idea is so if the idea becomes reality, well, likely so do many of the possible disasters that could come along with it.
Ever heard of the plan to build a dam across the mouth of James Bay, separating it from Hudson's bay? It was fully engineered and can be done...thank GOD nobody with more cash than sense has decided to back this idea.
Neato factor just doesn't cut it for me, I need real reasons that outweight the risks.
No Comment.
The Space Elevator
* Cost: 500
* Prerequisite: Super tensile solids
* Benefits: Doubles energy reserves production at this base and doubles mineral production rate at all your bases when producing orbital improvements; your units equipped with drop pods may now make orbital insertions anywhere on Planet; this project also waives any aerospace complex restrictions on orbital improvements.
We estimate that during the next mission century most of Planet's industries will be moved off-planet to Nessus Prime and other orbital facilities. Many of our industries will benefit greatly from the low gravity environments available in space, particularly those involving genetically engineered microbes.
CEO Nwabudike Morgan
"The Centauri Monopoly"
Never approach a vast undertaking with a half-vast plan.
dear timothy,
judging by the quality of comments so far for this story, i think that slashdot posters should be required to read the book in question before commenting on its book review. a little yes/no check box would do the trick:
Have you read the book being reviewed? yes/no
it would be like those web sites that check your age to make sure you are over 13 so that they can collect your information. this honor system is proven to work; there are no records of anyone under 13 selling their privacy on the internet since that law was implemented.
sincerely,
donna
Considering that a small paint fleck travelling at 20,000 kph can imbed itself through several layers of lexan, what's to to stop stray bolts from constantly clipping this thing in two?
Okay, okay, you're saying, that's obvious. However we could look at another scenario to see how such things are possible:
Say we're sitting in 1983 or so, and we're saying, boy, it would be nice if all universities could have supercomputers and massive 10GB storage arrays to do computational exercises. Looking back 20 years, we know that's basically possible. The desktops of today were the supercomputers of yesterday.
So, let's figure out how to spread the cost. How can we incorporate carbon nanotubes into equipment that everyone needs/wants to use? Does it mean integrating it into automotive equipment? Consumer electronics? Clothing? What?
What would be the killer business/consumer application for carbon nanotubes?
If we assume that cost is a function of production size and research money, the best way to up both is to provide a market that's not pie-in-the-sky (forgive the pun). We can have cheap nanotubes in 10 years, but it seems that the best way to do that is to make nanotubes common everywhere, not by utilitizing the NASA budget (which is going to be under heavy scrutiny after the latest disaster).
-- Bird in the Bush: The Renewable Energy Blog http://www.birdinthebush.org
Even if something like this can be built and erected, how long would it last before it needed overhaul or replacement? Parts wear out, even carbon nanotubes.
Maybe there's a nanotech solution so that tiny repair robots can constantly be working on maintenance. How close are we to nanobots that can handle such a task?
You see? You see? Your stupid minds! Stupid! Stupid!
How can I be a part of this? How can I be involved in making it happen? I probably have no skills that would be relevant (unless they need a database backend designed and some Perl kung-fu for some reason), but I'll do anything. I'll sweep up at night. I'll make coffee and donut runs for the engineers. Anything. Just let me be involved somehow. I'll quit my job right now and move to Australia or wherever and live on bread and water and raw dreams.
-- http://frobnosticate.com
Just because you can do something... doesn't mean you should. This would be a horrible waste of money.
This is precisely why the government should not be involved in pioneering space travel...the tendency to think big is not good in this case.
If the originators think this is such a great idea, then let them raise the money and do it themselves. I'll be the first in line to congratulate them, but keep my money away from this scheme.
Why does this remind me of Fred Flintstone using his feet to propel his car forward?
I guess any space technology improvement is a good one, but does it really need to be so brute-force-ish? Whatever happened to the NASA of old that created the shuttle?
They say that the next generation of space craft is still many years off, but I bet money could dramatically reduce the time frame (money always fixes problems like this - yay capitalism!)
I think it is good to at least gaze into the future of possibilities and while this certainly would make for cheap satellite launches, etc.. I am skeptical at how safe it would be to send humans up or back on it..
Say it comes to a grinding halt 1/2 way up. What on earth do you send to rescue the people off it this time?
A wholly owned subsidiary of United Technologies Corp (UTX).
The authors argue that carbon nanotube fibers are both strong and light enough that a 100,000 km elevator, constructed of a 2m wide carbon nanotube "ribbon," could be constructed in 10 years for a cost of US $6 billion
Given that nobody is currently manufacturing things out of carbon nanotube fibers, I find this 10 year projection the equivalent of vaporware. I think a very long period of R&D will be needed before a 2m ribbon can be constructed.
Interesting analysis of the materials. I wonder what the self support length of other materials might be. Like spider's silk, which is claimed to have tensile strength far greater than that of steel.
-- Minds are like parachutes... they work best when open.
I always wondered what the "climbers" would hold on to. Carbon nanotubes are probably a bit slippery, like graphite. Are they going to punch chain holes in it? Also, how do the climbers adjust for the changing width and thickness along the ribbon?
Obviously the answer is not a space elevator, but a space escalator. Make it an endless belt that can be rotated. Provides a two-way transportation path, as well. The mass would have to be much larger though (continous profile along the entire length).
...
I worry if we make the cost so small, we'll have an artificial ring of space debris around our planet and we'll never be able to get out of here.
Besides previous Slashdot stories about NASA's space elevator project, I also wrote several columns about this concept in the last months. If you're interested, take a look at "NASA Plans Elevators to Space," "Pushing the space elevator closer to reality" or "Space tourism 'viable at $15,000 a seat'?."
Elevator that powers itself up the cable? NO WAY. It needs to be a loop that is powered from the ground, like a ski lift. The payload just gets into position and grabs the cable. It then lets go at the top. The only problem is the cable is twice as long and will wrap around the earth a couple times when it breaks and starts infernos all about the equator. If it werent for bad Karma I'd have not Karma at all.
Going up?
The earth is a closed system. Our garbage, though it may be destroying the *present* environment, is an important part of that closed system. Removing significant amounts of almost anything, even garbage, from the earth will have a far greater and worse effect on mother nature than anything else we have done so far.
Right now, we may be killing our environment with our garbage. But, after we are gone the earth will continue. If we remove significant amounts of anything from the earth, it will likely die and be like the moon.
Sorry for the unrelated comment, but I think this has to be posted. It concerns an example of the extremely ignorant attitudes towards war with Iraq: http://web.syr.edu/~mgkemp/dailyupdate.html
What chance is there that the cable acts as a wick and drains earths atmosphere out to space? How about bringing pollutants in from space? Are these derned scientists about to get us all killed again?
This has far too many practical applications.
If you want to build a monument to humanity, I suggest we carve a peace symbol on the moon.... using nuclear weapons.
The book/article mentions that the ribbon will initially wound on a mechanism in LEO, and then unwound during deployment to a floating platform on the equator. Just wondering what the minimum bend radius is for nanotubes. If you wind it too tightly, you'd fracture a lot of the tubes, significantly reducing the ribbon's strength (you'd be relying on the cross-tube adhesive more than before).
Chip H.
I am surprised no one posted this yet, but the thing is that there is no free ride with space elevator. When you climb it, the object will accelerate (the speed of the sattelite at geostationary orbit is much higher that the speed of an object at the earth's surface). So it will experience what is called Coriolis force (actually, pseudo-force) that will accelerate it. At the same time, the speed of the sattelite will decrease, and after some lifts it will fall down to earth. To maintain it on the orbit, we'll have to burn some fuel, the very thing that we want to avoid by building the elevator. -- regnull
ONE ELSE STORIES MIRRORED??
As a research project, this is interesting. The concept is interesting. As a potential candidate for transportation, its next to impossible. Its so improbable that I'm amazed that people can consistently talk about it as if it'll eventually happen.
Perhap after strengthening it. First thing is to deploy more of them. Suppose you start shipping cargo up the elevator... Alternative methods to get payloads to space are so expensive in comparison that support for them dries up. If something happens to the elevator, there would be no way to build a new one. Naturally there will always be some need for rockets, but suppose the shuttle program stops and you need people in the LEO part of deployment of a first elevator? Better make at least 2 and keep them separated.
Ok, at least what must be done is teorically possible and have a lot of work done, but some of this depend that some things can really be done.
But when the space elevator is done, and if the ticket is not as sideral as its heigh, will be fun to go to an elevator with only 2 buttons: 1st floor - 1billonth floor
Or the folks making these estimations never leave their ivory towers and actually BUILD anything on this scale.
The Big Dig in Boston is approaching US$15 billion in total cost, but we can build an elevator to GEO for 6 billion? I doubt it.
There's zoning and environmental regulations that need to be taken into consideration. Dealing with the unions, waste disposal, etc.
You're better off leasing.
Maybe we should consider that the technology for this currently exists but that it is in the extremely prototype/classified military stages. Microtubules of carbon are hard enought to sustain for any length measuring centimeters, and even if you foud a way to use buckyball carbons to construct these tubes there is the problem of finding a solvent capable enough of holding them together. Also, what will serve as the counterweight on top? A big-ass space station? A small asteroid? Anything large enough to support this thing will take years to bring into orbit/adjust to our orbit. Finally, look at the proposed sites for the elevator. Ecuador is considered a prime site but look how close it is to the Sendero Luminoso terrorist groups in Peru and narcotraficos in Colombia, neither of which like the US government (funding it) too much. Perth, Australia is considered another prime site but look at its proximity to the extremists in Indonesia. This thing would prove an obvious terrorist/sabotage target, especially if other nations started trying to build their own. The idea is sound, but the technology to build it and actual construction techniques needed to work with nanotech don't make this a realistic project for at least 25 years IMO. In the meanwhile, we need to concentrate on developing newer LEO and HEO lift systems to get our tech into space while the kinks are worked out of this project.
As long as there is a Second Amendment, there will always be a First Amendment.
If you know what you are talking about...
The economic trouble we're in now began back in the eighties with Reagan's service economy bullshit. Essentially IT and the stockmarket has been little more than a multi-player rehash of the 1930s Ponzi game. These Republican bastards represent greed, not American capitalism. American capitalism is about growth through managed competition, not supporting vicious monopolies in a desperate grab for power.
The likelihood of biotech taking up the slack from IC and software is very low. On the one hand you have Affymetrix and the chip players with their promising well paying plan for tailored therapies, but on the other hand you have magic bullets like stem cell therapy that could totally wipe out profits.
If we want to keep going with the capitalist experiment, we've got to get back to our roots --exploration. The promises are as enormous as the American frontiers seemed in the eighteenth century. The only way this will happen is with a genuinely cheap ticket to orbit. America needs a space elevator.
A space elevator has a lot of odds against it. This book sounds like a good example of the fact that the odds tell you what you have to do to succeed - not to give you a reason to quit.
/. book reviews, but this one actually intrigues me.
Besides, they don't call it Space Exploration for nothing. Exploration denotes a lot of unknowns.
It's how you meet them that matters.
I'm usually not thrilled with
"The Sage treasures Unity and measures all things by it" - Lao Tzu
... yep it would be like wasting $19bn a year failing to eradicate drug usage, or paying out £100bn a year so people don't have to do any work, or giving 30bn to farmers to keep their fields empty ... wait a second ...
A news report on the Space Elevator comes on the TV.
Kent: But there's already one big winner: Our state school system, which gets fully half the profits from the Space Elevator.
Skinner: [talking with his teachers] Just think what we can buy with that money... History books that know how the Korean War came out. Math books that don't have that base six crap in them! And a state-of-the-art detention hall [holds up a scale model] where unruly children are sent to Space Elevator detention.
Teacher: [to no one in particular] Space Elevators. Always with the Space Elevators
</Obligatory Simpsons Reference>
[With apologies to Dog of Death episode.]
-kgj
Whether or not gravity was working on that day or not.
Ok, so imagine that this thing breaks about halfway up. The portion connected to the ground stays put or maybe it collapses in which case you've got no problem since it's built over the ocean and like you say it's not going to collapse onto anything (except perhaps the poor bastards getting ready to send their load up the elevator).
The portion that's no longer connected to the ground would then be in a very low orbit wouldn't it? It's going to come back down though where would depend on a number of factors. I don't know enough to speak intelligently on what those are so I'm going to have to pass this on to someone more knowledgable than I am.
But I imagine it would come back down. How much debris would we be talking about? How far away from it's orginal anchor spot would it get before it came down? How much of it could we expect to burn up?
It's something I don't want to be "down wind" of I know that much.
Appended to the end of comments you post. 120 chars.
When a payload is hoisted, the geosync end [and it had better be massive] will have to accelerate it and slow down itself. You'd get this back when you lowered a load.
Q: So why aren't we doing it? Why aren't we making this priority 1, when it could boost space exploration by several orders of magnitude?
A: Because today's gov and NASA contractors still have a lot of expensive rocketry missions in store, to extract lots of funding from the taxpayer. The mechanism is identical to there being no alternative to gas-powered cars, because influential people have a lot to loose when new concepts make things cheaper! So they keep telling you it can't be done, and it CAN'T be done until someone actually does it!
If you would do a poll now asking the average American whether a space elevator could be done, I'm willing to bet a month's salary that the result will be: "90% think it's a ridiculous idea and it can never be done." and answers like "That's all science fiction, we better stick to our rockets, and by the way spacefaring is very complex it can't be done just by stepping into an elevator."
That's because of the way the public opinion works. If NASA would announce tomorrow "we are, as of now, committing a large part of our budget to build a speca elevator" you can bet that wise people keep appearing from all over the place, explaining the Reasonable Concept Of The Space Elevator And Why It Must Be Built.
But that won't happen any time soon. Sometimes I think science fiction may have done more to prevent space exploration progress than many other factors, because it's so easy to use it to ridicule concepts of technological progress.
It makes me so sad when I see what we could achieve even within our lifetime, but our world's inherent corruption prevents it from becoming a reality... (sniff)
Secondly, if they anchor it somewhere in the middle of the ocean (as most people seem to suggest) it is going to be quite easy to enforce some exclusion zone. Sea is comparatively flat and easy to patrol, both with actual ships and via radar and satellite imagery. There is always the possibility of terrorist organizations with submarines, although probably a few active sonar buoys would help.
Lastly, at 36.000 km hitting the terminus with just about anything requires rather sophisticated technology, akin to ICBMs. We'd be in a whole lot of trouble in that case, and the terminus makes a comparatively poor target for this kind of capability.
Not to play the contrarian here, but the terrorist threat to such a structure is, in my opinion, being vastly overstated in this discussion.
Pathman, Free (as in GPL) 3D Pac Man
This thing would be the biggest target for terrorism would it not? so even if it got built, wouldn't it just be doomed anyway?
All it takes is one deluded muslim with an airplane and you've got a huge pile of carbon fibre nanotube trash. This thing would be too tempting a target for anyone who has a grievence against whoever builds it.
The Russians have won. They have made the world a cesspool of distrust, greed, fear and hate.
I wish I'd have an option to skip all (overrated) funny postings.
:)
While I really really appreciate the -1 rating to avoid spam, trolls and flames... the higher ratings are obsolete at the moment: If you want to read all interesting and informative postings, you you have to ignore the ratings to catch up all the informative postings. funny postings are overrated IMHO and the real informations stick also in lower rated '2' postings or in replies (which become seldom highrated).
Well, please slashdot crew cosider an filtering option 'skip funny ratings'. Thanks, Mark
PS: great article
Such a lot of work to create an elevator with only two floors...
Exchanging the positions and the speeds of two bodies having identical mass is (in theory) free. Now imagine the following gadget: a rotating cable with two docking stations on its ends orbiting Earth. The far end is on geostationary speed and distance, the near end is LEO. All you have to do is to lift the satellite to LEO (at the right time) and the cable will swap it with an old GEO satellite.
This system can also be cascaded, and the inventor proposes a chain of such cables from LEO right up to the surface of the moon. We could put up stuff on the moon in exchange for moon rock. COOL.
Its better than space elevator in that you can use honest-to-god iron instead ot the exotic and expensive carbon-nanotube stuff.
longest. review. ever.
Kim Stanley Robinson in "Green Mars" I believe.
Your knowledge of Heinlen is impressive; reading your list made me recall books I'd forgotten I read.
"the best safety of the frontier...will be secured by total annihilation of the few remaining indians" L Frank Baum 1890
If the ribbon broke, then the lower part should fall into the sea as you suggest. But I think that the upper part of the ribbon, and the satelite, which is now well above Geosyncronous orbit (in order to support the weight of the ribbon and its payload) will be hurled away from Earth. I have read that by using the uppermost part of the space elevator as a launching station, we would be able to fling craft to Mars in a fraction of the time it takes us to get there now. So I would think that the upper part of the elevator would not pose a problem to us here on the surface.
Now if something hit the ribbon and pulled the satelite too close to Geosyncronous orbit, then the whole thing might fall down, but it should all be pretty much in the same area.
He's a hack author, and a bit of a nutjob, but let's at least get the name spelled right.
Skinner is a predictable man; of all the Simpsons characters, perhaps the easiest to parody.
I'm guessing he was raised in a box by some eminent behaviorist.
-kgj
how much carbon would this take? could silicone be used instead?
instead of 'adheavsives', couldn't the nano tubes be woven?
instead of waiting for space object to hit the cable, couldn't lasers be used to 'push' the object over to one side?
It seems like making space elevators readily available to many countries would be a bad idea. (Specifically, I mean when the review mentioned that the space elevator could be used to produce other space elevators for sale to other countries.)
What would Saddam Hussein do with one? He would likely send a huge bomb up into geosynchronous orbit, then have it drop on the US. Possibilities like this make me glad that we're developing the missle shield program (initially known as "Star Wars" during the Reagan era.) When Clinton took office, he discontinued it, but it is going forward with Dubya in office...
Because you'd have a conductor between the clouds and the ground, it should equalize the charge differences and would prevent the "shadow" charge from being generated on the ground which would prevent the path of negative charge from the cloud to generate the "equalization" bolt of lightning.
Assuming that the current theories on how lightning is created are accurate, I wonder if the localized decrease in lightning would have any environment effects.
You just KNOW you're going to be spending 1000km listening to elevator music. How many sane astronauts will we have left after they're forced to spend a day riding into orbit while listening to the vienna boys choir version of a Kenny G song? And of course the other problem is no matter how well you secure the facility, no matter how carefully you screen the passengers... you just KNOW some annoying 9 year old kid will jump in, press all the buttons, and jump back out....
Payloads into orbit every other day? $/lb low, lower, lowest? Routine access to earth orbit? Where have we heard that before?
If Slashdot were chemistry it would look like this:Cadaverine
One can't help but be reminded of the biblical Tower of Babel (a proposed tower that would reach heaven) -- you'll remember that God put the ax to that project by mixing up the languages spoken by the various participants.
:)
Now, if NASA is involved, will the mixup be metric versus imperial measurement?
who's moderating the meta-moderators?
Why is everyone saying "NASA should do this!" or "the government should do this!".
/.ers would be immediately suspicious of the "Bill Gates Space Elevator", and it would frequently lock up and need rebooting.
If I had several billion dollars, I would be a complete idiot NOT to sink my money into such a venture. Of course,
For the mega-rich, the income potential and (maybe more importantly) the "my name in human history" potential of this SHOULD be irresistible. Plus, I'm a firm believer in free-enterprise. Let companies do it for a profit and it will be safer, quicker, and more efficiently run than any government project.
-Styopa
http://www.tiem.utk.edu/~mbeals/spider.html
The tensile strength of carbon fibre composite is listed here, and it's nothing like the 130 GPa which the article is aiming for.
http://www.fibraplex.com/tow.asp
Personally, I just love the way in which the need for high tensile strength materials is glossed over. That is THE tough problem to be solved, but don't go the website or its FAQ hoping to be reassured on that score.
If you calculate the theoretical ultimate strength of a material based on the number of bonds per area, and the force required to disrupt those bonds, you get numbers of the order of 300 to 500 GPa. REAL numbers come in several orders of magnitude lower (see above). And the answer to why is illuminating.
You don't get perfect materials. Little imperfections (dislocations are an example) in the structure of a material provide points of weakness which can yield at much lower tensions than the theoretical upper limit. Additionally, carbon composites are tricky things to handle. Carbon nanotubes LOVE sticking to each other, and don't readily separate, or embed in a composite matrix. (Bear in mind, I'm not sure what material they have in mind. Carbon nanotube weave is completely different from carbon nanotube composite.) Because of this poor adhesion to the matrix, carbon composites have a nasty habit of failing completely. Small flaws tend to focus strains onto the point of maximum weakness, and the material tears itself apart.
The big problem is getting chemical bonds to go where you want them to go. In polymer science, that is getting closer to a solved problem, with the molecular weight of UHMWPE well into the millions. But carbon nanotube production is still very very primitive.
Ok, so what about the falling debris? is it enough to create destructive waves. Or even thunami?
A ribbon will flutter and will soon turn into a messed up twisted round shape, so you would do better by designing it to be a round cable to begin with. Handling oscillations, weather and collisions would require it to be hundreds, if not thousands of times stronger than required. So even carbon nonotubes would not necessarily be strong enough for a practical system.
And the whole earth was of one language, and of one speech.
And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar, and they dwelt there.
And they said one to another, "Come, let us make bricks and burn them thoroughly." And they had brick for stone, and slime had they for mortar.
And they said, "Come, let us build us a city and a tower whose top may reach unto heaven; and let us make us a name, lest we be scattered abroad upon the face of the whole earth."
And the LORD came down to see the city and the tower which the children of men built.
And the LORD said, "Behold, the people are one and they have all one language, and this they begin to do; and now nothing will be withheld from them which they have imagined to do.
Come, let Us go down, and there confound their language, that they may not understand one another's speech."
So the LORD scattered them abroad from thence upon the face of all the earth; and they left off building the city.
Therefore is the name of it called Babel [that is, Confusion], because the LORD did there confound the language of all the earth; and from thence did the LORD scatter them abroad upon the face of all the earth.
"Overhead, without any fuss, the stars were going out."
Sure, someone can do it but this will not work period! Forget space elevator BUT I want carbon nanotube for my shoelaces so it can last longer than three months untied, please.
Arthur C. Clarke - (note the missing "e" Why is it technical people who think they're so smart can't spell their way out of a paper bag?
Very in-depth, with some real criticism of the book, too; very different from the elementary-school book reports that some SlashDot revews can be.
Quite apart from the fact that the RGB Mars series was just a story based on comparatively limited scientific research, we're also talking about a microscopically thin ribbon here, not the massive one described in K.S. Robinson's books.
Just explosively cut the in-atmosphere parts of the ribbon into 100-metre lengths containing a very small weight at each end, and watch the parachutes fall to earth over a period. Only the vehicles currently in transit up or down would be in trouble. Drag drones and parachutes for them I guess.
The main problem would be with the section heading outbound after detaching from Earth. The rescue mission would have a pretty tall order just to save the people, let alone elevator resources.
But I imagine it would come back down. How much debris would we be talking about? How far away from it's orginal anchor spot would it get before it came down? How much of it could we expect to burn up?
/. before, and the theory in the last article was that the ribbon would break up into tiny nano-chunks. The exact environmental impact would probably have to be studied more, but it wouldn't be anything like 40,000 km of steel cable falling from the sky.
It'd be a meter wide, a few tens of thousands of kilometers long, and a micron thick. That's 10^-6 meters. It probably wouldn't fall so much as flutter.
The idea of a carbon nanotube ribbon space elevator has been on
The enemies of Democracy are
But couple of issues.
50,000 miles is a long way for a mechanical crawler. Escpecially one that amounts to a 20 tonne capacity elevator and it could never exert more than the load limit in terms of force.. IE if 20 tonnes is the theoretical maximum for the 130 rated nano tubes then lifting 20 tonnes at say a 9.8 mps (1G) acceleration would be roughly 40 tonnes of force on the cable meaning a broken cable. Thus you would likely be lifting 18 tonnes and having low acceleration loads, you also could not exceed that load when decelerating. Hitting the gas or breaks to hard could lead to exceeding the cables strength. I am wondering if a lighter system with more leeway to zip up and down the cable would not allow for easier and more timely transfer of mass.
for example:
If you can accelerate/decelerate at 1g with a 20 tonne vehicle (40 tonnes of force ) then you can accelerate at 4g's with a 10 tonne vehicle ( also 40 tonnes of force ). This means you can go ~4 times as fast which is a very significant difference when dealing with long transit distances. So a 20 day round trip by the 20 tonne could be accopmlished in 5 days by the ten tonne and would allow for 4 trips in the same time. Even if the 10 tonne only had 30% of the cargo capactiy it lifts more in the same amount of time over the long haul. You get that benifit whatever the units of acceleation are be it G or more likely in fractional G acceleration loads. And the smaller the rates we are dealing with the larger the impact is of relatively small increases.
Don't get me wrong, the idea is great but the margin of error here sounds awfully thin esepcially considering the key material hasn't reached its theoretical proving point in a LAB much less in a mass production environment. Once they do that I say full steam ahead. But until then its a bit premature to start tossing out headlines reading "Space elevator for just 6 billion "
perhaps if it read
"Space elevator for just 6 billion IF IF IF IF IF IF IF IF IF"
I don't ask you to be me. I only ask you not expect me to be you.
How about an elevator to the otherside of the earth? It would shorten the distance by about 7000km.
that it was a near certainty that by the time I was old enough to ask a girl out on a date, the question "would you like a ride in my spaceship" would be greeted not with derision, but with awe. Of course the sad reality is that none of this has come to pass.
Girls, dates, what was I smoking back then?
Contrary to what American trial lawyers would like you to believe, nothing in life is risk free.
The question is whether the risk (and investment) is warrented by the returns.
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
Too much focus on weak forces, the EM forces are the real issue. It is a 10,000Km antenna. Forget the low conductivity -- at the voltages it will create from the static charges alone, it might as well be a copper lightning rod.
Since we waste most of our space exploration money on making it possible for people to eat, sleep, drink, defecate/urinate, bathe, and breath in space, we don't have good enough robotics. There is, of course, the european walking robot that is supposed to quickly move to deal with external damage to the ISS, among other things.
By spending so much on manned space flight, we are barking up the wrong tree and drastically retarding space exploration.
Shameless plug: See also my page about an alternative concept which avoids the problem with skyhooks that they are incompatible with satellites.
This seems sensible. I find it kind of incidentally funny, though, that we could now be at the point where NASA might depend on the consumer market to pay for the development of advanced technologies... traditionally, we have always heard about the opposite path: technology developed as a solution to NASA's engineering challenges being "spun off" into consumer products!
Hey, I think I'll go have some Tang! ; )
look it up bro... the news guys all did their own "recounts" ...
and bush still won florida.
if al had had his way, we'd _still_ be counting, and they would be re-defining what chad configuration constituted a "vote" every other day in a vain effort to conjure votes for al that may or may not have been cast.
Jeez, move on already.
dum spiro, spero
Could the elevator be used to get rid of nuclear wastes by sending them to outerspace ?
We could send the wastes in orbit in small loads to limit the risks in case of an accident. Then hang a rocket to them and send them out of the solar system, or in the sun, or in jupiter, or anywhere else far away.
They said it could be done, not that it could be done NOW. If they put a 6mo. stop on military spending to build a space elevator they'd still have to invent mass producable carbon nanotubes, the infrastructure to transport such, figure out the hundreds of international treaties required to appease the rest of the planet who will be wondering like Slashdot "What happens if it falls", and train however many thousands of people in Space Elevator repair and maintenance. If nothing else, I didn't see anything in the article about what the initial payload to orbit would be. If it's really significant you're talking about having to build new launch platforms just to get the basics into orbit and shuttle launches to support it. THEN you have to wonder about the International Space Station, which would probably find itself shit out of luck in the funding department once something like this got rolling - and wouldn't that be just the king of wasted cash...
In conventional carbon fiber-based equipment (tennis racquets, planes, etc.) some material, often an epoxy, holds the fibers together. I haven't read the book, but it may be difficult to hold the fibers together without adding several times their weight. Right now mass-produced nanotubes are around 10 microns long, with exceptional tubes 100 microns to 1 millimeter. Efforts are being made to continuously grow tubes, which would in principle allow arbitrary lengths and less splicing. I consider this a more important obstacle than the slightly-too-low strength of the fibers themselves. -David
The questions is would SSTO even work? How much would it cost. Well, graphite-fiber composite was supposed to give such a boost in increased mass fraction that a SSTO was supposed to be feasible. We are only talking graphite, not carbon nanotubes here. It turns out the graphite composite cracked when cycled through with cryogenic propellant. And then they gave up on X-33 after spending a billion dollars.
If that carbon nanotube stuff has such great strength and is just within reach, you should have SSTO spaceships build out of it long before you build that Space Elevator.
The platform from which the initial ribbon is deployed.
Getting ships to it as it gets higher and higher is a problem but that's a hell of a lot of mass already in orbit.
If you don't want to repeat the past, stop living in it.
"Is that a rocket in your pocket?"
Rich
Rich
According to my "Nasa's big book of imperial/metric conversions", these are actually the same length.
Rich
Ironically UCLA chemists have recently reported making advances related to carbon nanotubes. It is a room-temperature procedure so it could eventually be used for commercial applications.
0 30 6075829.htm
http://www.sciencedaily.com/releases/2003/03/03
-
For the mega-rich, the income potential and (maybe more importantly) the "my name in human history" potential of this SHOULD be irresistible.
- Plus, I'm a firm believer in free-enterprise. Let companies do it for a profit and it will be safer, quicker, and more efficiently run than any government project.
- The good reason to reach for this which can't be emphasized enough in the current environment is that for a relatively modest investment, the impact on the economy would be enormous (and good). Compared to other proposals to jumpstart the economy, this one has incredible bang for the buck.
-
I am sure the terrorist strikes will stop themselves if the US gains a reputation for a R&D and science nation instead of a warring and military nation.
- I seem to recall that the base of these things would be on large platforms anchored in the middle of the ocean, so if they did collapse, they would just fall harmlessly over water.
- Space elevators around Mars create an efficient Earth-Mars transportation network. Elevators on the moons of Jupiter throw spacecraft down into Jupiter's turbulent upper atmosphere to scoop up 3HE and ship it back to Earth in decade-long space convoys where it will power the latest and greatest IEF fusion power-plants.
Meme 1: Cheap access to orbit will translate into a vast economic bounty.Meme 2: Big infrastructure projects are done better, faster, and more cheaply by private enterprise than by government commission.
Meme 3: Terrorism will stop if we only [insert good-intentioned but simplistic solution here]
Meme 4: If a space elevator falls, nothing bad will happen. It's way out in the middle of the ocean.
Meme 5: [insert currently fashionable incarnation here] nuclear fusion is the way to go.
Meme 6: Your "place in human history" is really really important.
Meme 7: Mining the solar system is not only economically feasible, it's commercially attractive.
I have a hard time with all of these, although I'm sure circumstances can be described where they have a kernel of truth in them.
As I have mentioned in the past, I am in favor of a major unmanned space program, but mainly as a vehicle to stimulate technological development with non-military aerospace and robotics projects. The Space Elevator might help, if it fulfills its promise of cheap access to LEO. Hard to believe, though. 10 years and 6 billion dollars seems very optimistic.
Why bother tethering this thing to the ground? It should be feasable to have a platform that is strung below it at a high altitude. Supplies and payload could be brought aboard by helicopter or blimp. This would reduce the overall length of the elevator and also make it movable (easier to avoid space junk). The platform would be a counter weight and could disconnect if part of the ribbon is cut somewhere else.
This would also make it look very cool (kind of like Lando's place in ESB).
I'm sure there are a million reasons to not do this but there were a million reasons not to go to the moon and we did that.
The thing that bugs me is that the material necessary doesn't exist. Nobody knows how to make carbon nanotubes of arbitrary length and consistent shape. Last I heard, they could barely make them 1mm long! They haven't even managed it to live up to its theoretical strength in the lab.
Furthermore, they know very well that nanotubes don't like to crosslink with anything. Nanotubes are basically graphite (a planar form of carbon) wrapped into a tube shape. Graphite and nanotubes have a highly stable resonant structure, with no electrons free to bond with anything else. That's why graphite is used in pencils - the graphite layers slide right over each other. In nanotubes, there are no electrons available to bond and thus no bonding, no crosslinking, no nothing. They'll slide right through any matrix they're embedded in.
In other words, though the strength of the material seems very promising at first glance, they've got a lot of work to do for a practical solution. Remember, a chain is only as strong as its weakest link.
Off topic, an elevator climbing the ribbon would require a lot of energy. One descending the ribbon could actually generate energy, certainly enough to support its own operation, maybe enough to help power those going up under the right circumstances.
---If you can't trust a nerd, who can you trust?
How much would it take for a payload to depart from earth and arrive at the top of the elevator?
Everybody has a purpose in life, maybe mine is to lurk in slashdot.
So the earth has its own center of gravity (obviously)... Anyone know what the outward force of this 'space elevator' would have on the center of gravity of the earth if it was indeed bolted down? I mean we're talking about a sphere (our planet) rotating... Now we're bolting something to this ball and having it run out into space (like a ball and chain). Wouldnt we need to build these elevators perpendicular to the axis of the spin of the earth and put them on opposite sides of the planet? Maybe i'm just not thinking properly right now but would someone care to explain?
Science Daily is reporting today that UCLA chemists have found a new method for producing Carbon Nanoscrolls. It appears to be a cheaper alternative to Nanotubes. Edit: I see a previous AC poster mentioned this briefly. Well, this expands on it a bit.
UCLA chemists report in the Feb. 28 issue of Science a room-temperature chemical method for producing a new form of carbon called carbon nanoscrolls. Nanoscrolls are closely related to the much touted carbon nanotubes but have significant advantages over them, said Lisa Viculis and Julia Mack, the lead authors of the Science article and graduate students in the laboratory of Richard B. Kaner, UCLA professor of chemistry and biochemistry.
Ok, just for kicks and gigles. What would be the sound of a thin cable of this sort occilating. Whether its attached to ground, or ocean, its going to have a little bit of occilation. That should create a very deep bass tone I'm thinking.
fnord
[Submit]
Comment removed based on user account deletion
Oh, gods, I can't resist:
l ?m enu=news.celebrities . Seems he could save an awful lot of money....
http://www.ananova.com/news/story/sm_559816.htm
Does this mean that "livin' it up while I'm going down" might be an week-long job?
http://www.highliftsystems.com/convertedToHTML/nia c_pdf/contents.html
nice analysis !!
Ummm.... 3.8 centimeters is not a foot. It's roughly 1.5 inches. You're wife's just humoring you all this time.
I take drugs seriously.
Or even thunami?
I'd see a speech therapist about that lisp if I were you.
I take drugs seriously.
Great post, but the moderators seem to have missed the quote.
1 cm = 2.54 in
3.8 * 2.54 = 9.652 inches != 12 inches
Silly Rabbit.
Redundancy is good; triple redundancy is twice as good! - Me.
The article sez a height of 4000km. That's about 2500 miles, or roughly the width of the US. I'm not saying I want that falling on my house, but it's a far cry from wrapping itself around the world.
Second, the earth has an atmosphere (really! I swear! ;>). Assuming the thing has a center of gravity roughly near the geosynchronus orbit point, when it snaps the part above the break will go flying off, never to return. The bottom will fall. However, it's a ribbon, therefore having a high surface area/volume ratio. Three things effectively determine whether a meteorite burns up before it hits the ground - density, SA/V ratio, and vaporization temperature of the material (roughly). Nanotubes should be less thermally stable than rock, it's more dense (meaning it has a higher terminal velocity for a given shape/size, and spends less time in the atmosphere "burning", though granted at a higher temperature), and they have an incredible SA/V ratio.
Long story short, I expect that most of it will burn up long before it hits the ground. It's far lower TV also means it will be moving very slowly when it hits, and its size should mean that it will not hit all at once, dissipating its energy somewhat gradually.
But I'm just guessing. ;)
-Looking for a job as a materials chemist or multivariat
http://www.howstuffworks.com/space-elevator.htm Is this picture the same thing?
Every time there's a space elevator article, some dope points out that there was a problem in some science fiction story, then someone with a grasp of physics comes along and explains the atmosphere.
I can see a serious plethora of other applications for nanotube fiber.
Yeah, sure it's an expensive option but, woven into fabric it should be fairly resilient. "Nano-weave: it's the new Kevlar."
Stretch it over a form and impregnate it with some sort of semi-rigid polymer to form ultra light body panels and other parts for everything from golf carts and SUVs to aircraft and orbital workstations.
My office has been taken over by iPod people.
The following paper gives an idea what some of them are, and where we are in the commercialization process. Most of them are at stages where we either have evidence of interesting properties, or else measured proof of interesting properties, but we don't have any manufacturing processes that would let us put them into place. But there are a small number of applications already out there, and many, many more which it is certain will be viable as soon as production processes improve.
Rich
Many of the posts regarding this book/review are convinced we should already be building the thing for the lousy $6 billion it will cost. The problem is the $6 billion number and the technology are still NOT real.
The authors admit that the tensile strength needed is 3 to 4 times greater than any experiments have shown so far. They ASSUME that the strength needed can be reached in the near future based on theorical projections and it can be mass produced for cheap. They additionally assume that the nanotube technology will not have adverse environmental impacts that will curtail production and drive up costs.
The $6 billion budget seems horribly low and fails to account for the vast amonts of R&D, and manufacturing that would be needed before construction could begin. $6 billion is a small amount to the megacorps of today and they would jump at the thought of such a great ROI (Return On Investment). Then why aren't they investing in this already? Because it is still a LONG way off from reality.
I like the idea as much as most people, but the truth is that this idea has many obstacles to overcome before serious development can begin. My guess (and it is a total guess)is that the real cost would be closer to $60 billion after the technology has been developed.
can grow food for us next year. Food and eating is a little more important that space elevators
Anonymous Cowards - Oh God, How I hate you
To me this just sounds like a future terrorist attack plan to me!!!! lol the alqaeda of 2060 attacks the mighty space elevator by launching their asses into it, it falls quite easily!! (yes i know it would "fall" but this is a comedy post i do actually RTFA!!!"
$a = SQLquery) 'What we do in life
From your sig:
I propose that no one should use the word "Orwellian" unless they've actually read Orwell.
That's a bit Orwellian of you to try and control what people say and think... What're you gonna do, watch me all the time to make sure I only use "Orwellian" when I should?
Just because I doubt myself does not mean I find your position compelling.
The article sez a height of 4000km. That's about 2500 miles, or roughly the width of the US. I'm not saying I want that falling on my house, but it's a far cry from wrapping itself around the world.
Read the article again. The ~4000 km value is the value used to calculate the needed strength of the material, normalized to earth surface gravity. The actual height of the wire, just to reach geosynchronous orbit, is about 35,000 km. However, that would be a dangerous design, as the net centripetal force would still allow a severed cable to fall back to earth. By increasing the length to 100,000 km we get a number of huge advantages (enough energy to fling stuff off to Mars, Venus and the asteroid belt, not to mention the moon, and a huge safety feature in that a severed cable will tend to fall away fron the earth, not toward it). However, if the cable were severed beneath the geosyncrhonous way-station, the smaller part would fall toward earth while the larger part would be flung away.
Rather than a one-way cable, I would build several loops in parallel (think ski-lifts, or a hybrid cable-car/lift, complete with brief stops in motion for people to bet on and off). You could thereby operate multiple cars per cable loop, running them up one side of the loop and down the other, with stoppage only for loading/unloading. The stoppage could even be avoided with a coupling/decoupling mechanism, whereby the car decouples at the end of is ascent/descent and is taken to a unloading area, while a new car is coupled in its place in a separate, nearby loading area through which the same loop links a few tens or hundreds of meters later.
Multiple such loops would add sufficient redundancy that the way station and platform would be relatively safe even if one or more cables did in fact sever. That still doesn't fully protect one from the small piece of falling cable, but as you point out, the atmosphere is likely to take care of that, and safety features such could be added (cross-loop tethers, or the ability for each car to stop the motion of the loop, then tether itself to the opposing side of the loop, or a neighboring loop, and so on).
With terrorism a real possibility, reasonably safe failure modes will undoubtably be a requirement of such an undertaking.
The Future of Human Evolution: Autonomy
If the ribbon severed, say at 100 km, it would react to "inertial drag"( probably the wrong term) and spread out in the path of Earth's rotation, thus spreading across a large area of the equator.
Atmospheric drag would effect this but I'm guessing that the material is heat resistant so wouldn't we see a red hot "whip" slam down? The path seems safe in som eqitorial ares, but I'm only a caveman.
I think most of the gain is actually supposed to come from not needing reactive mass though.
Rich
Humans already speak enough languages without building a tower of babel.
Chika Chik-ah... do-e ow ow.
Young Einstein: "That's Relativity."
(with apologies to Yahoo Serious)
If you are are going to go through life believing that the only things that can be true are the things that "feel" like they should be true, you're going to miss out on some of the coolest shit in the universe. Relativity, as I said. Not to mention quantum physics.
One of the great things about science is that it lets us pursue the "Why not?" response to "It can't be done." The modern world was built on such thinking; the Dark Ages were built on intuition.
I'll tell you what the 'effect' is! It's pissing me off!
Also Diamond films can be extremely strong (>8GPa typical today). Perhaps coating optical fibers with diamond film or some other technology might improve the perfomance to make a large taper space elevator viable. The advantage is that materials are cheap and very refined manufacturing capability exists.
Fiber optic cable:
Tensile Strength:~3.9 Gpa (From manufacturer's data sheet)
Density: 2.0g/cm^3
Self Support height: 198km
Steel:
Tensile Strength 5.0Gpa
Density: 7.9 g/cm^3
SSH: 64km
...to make carbon nanotubes economical?
Is this stuff flexible enough to be used as rope? Could it replace hemp or other synthetics for ships or theatrical counter-weight systems?
I mean, if the only start to the manufacturing of carbon nanotubes is a NASA contract for a few million kilometers of the stuff for a certain special project, its gonna cost $100 a foot or more.
What?
It cant be done for the same reason why you cant balance a human hair on a golf ball.
Aint gonna happen, kids.
Bowie J. Poag
Rich
Think about it...
True genius is grasping a situation like a peice of fruit, and peircing it just right so that it drains dry.
But Seriously, set the time frame for 20 years just to be safe.
If the ribbon severed, say at 100 km, it would react to "inertial drag"( probably the wrong term) and spread out in the path of Earth's rotation, thus spreading across a large area of the equator.
You're talking about how the farther-out parts are moving faster, and as they fall toward earth that would mean they are no longer geosynchronous and would whip around, right? That's an issue, but I don't think it'd be that bad since the atmosphere would slow it down.
Of course if it severed at 100km, then only 100km would be coming down (the rest would fly off into space), which isn't a large area at all. Put the base 100km away from population centers (or trade routes, I guess), and there isn't any concern.
Also, you wouldn't really need to worry about more than that falling anyway. Anything that fell from above 100km would burn up in the atmosphere.
Atmospheric drag would effect this but I'm guessing that the material is heat resistant so wouldn't we see a red hot "whip" slam down?
At about 7kg/km, it isn't going to be "slamming down" anywhere. I think that's the key to understanding the safety issues -- the thing may be big, but it isn't heavy at all. Imagine a 100km feather, then imagine something much less dense.
Because of that, I think the whole falling issue is moot. With that kind of density, any horizontal motion would be slowed by air drag very quickly. In fact, I'd bet wind would do more to spread out the range over which it falls than the inertial effect. It'll kinda drift down and you'll have a big pile of carbon.
The enemies of Democracy are
There's probably a disconnect somewhere in my logic, but I think that positioning and size of the counter weight will be crucial.
The original idea is that the counter-weight is placed in geosyncronous orbit and therefore exerts only minimal forces on the cable, and the cable will support its own weight.
Until you place a load on the cable, and this is where my problem begins.
When a climber starts up the cable, there's a problem with the weight of the climber and payload and rotational acceleration. It is rotational acceleration and weight that will cause to counterweight move down and eastward as the climber will resist the increased velocity required to move away from the earth pulling on the cable and finally moving the counterweight. The climber goes slowly up the cable, but the cable is rooted on both ends and and forces felt on one end are also felt on the other, in fact the forces aren't equal at both ends at any given point on the cable but roughly the middle. (I beleive there is a bow type woodworking clamp based on this very principle, a small force apllied over a large distance at one end of the bow increases the force applied to the object at the other end of the bow mechanism.)
The weight meanwhile is moving down and east, from all these forces.; How long before counter weight crashes to earth, or the ribbon snaps from tension?
Now obviously there are two answers to the problem, both with the similiar problems of their own.
One is to increase the mass of the counter weight. A more massive weight would be more feasable, because it would move less, but; jets would have to be placed on it to maintain geosyncronous orbit, because there aren't any forces up or down on the counter weight in that orbit, any force, however small, will accelerate the object. One remedy for this is for every trip up make sure there is an equally massive trip back down again. What goes must come down. You only lose energy on friction.
The second answer is to place the weight further out, thus counteracting any downward pull on the cable. It will still tak an eastward tach upon climbing, but from the climber module on out the calble would be mosltly straight. The counter weight still moves down a bit, but easily reagains its perpendicular stance upon the climber reaching the top ( it would probably take on a pendulum motion at this point as it finds its way back to equilibrium.)
The problem is if the weight were to be placed too far out, the centripetal forces would have to be supported by the cable, all the time, and the cable has to support the climber and ensuing forces from climbing in addition to centripetal forces.
So the tensile strength of the cable is what determines the size and distance of the counter weight, and the size and speed of the payload.; Are carbon nanotubes, going to be able to withstand all these forces over roughly 10,000km? I'm massivley skeptical.
One Note: The exact opposite happens on the way down. A decrease in velocity, and an increase in weight. Not to mention your working against centripetal force on the way back, forces are reversed.
cat sig >
considering that this elevator would weight 100 trillion tons, could you imagine what would happen if it snapped near the top, and the rest fell on NYC? Ghastly.
As mentioned in the review, the strength of currently manufactured carbon nanotubes is, so far, grossly inadequate. It's theoretically possible for nanotubes to handle the required load, but WHEN can we actually manufacture them with the requisite strength?
But the even BIGGER hurdle to overcome is the LENGTH of the nanotubes. The longest we can manufacture currently are less than a couple CENTImeters, and this project will require nanotubes of thousands of KILOmeters in length. Even allowing for some sort of Moore's Law effect, and something to reduce the cost to within a reasonable range, it may take more than 100 years to develop the capability to make the nanotubes required.
So don't be fooled by the "10 years + $6 billion" estimate. It's doubtful we'll even be capable of building one of these in this century.
Anyone ever seen the South Park episode "Ladder to Heaven"?
Were you there when they built the Elevator to Heaven? --Alan Jackson
/^([Ss]ame [Bb]at (time, |channel.)){2}$/
Now, I don't find that quote very applicable to this, honestly.
This is no vain persuit of faith, it's science that can be made possible.
We know of the exhistance of space, and as for heaven, that has yet to be truly seen, if it exhists.
Let's not get into a heated debate over science and religion.
Rich
Screw the mile high club, how about the 200 mile high club. Fooling around in an elevator defintely wouldn't be a quicky anymore. ....floor 26,153 lady's lingerie
Also what about those bratty kids that hit every button and then jump off the elevator. If you got caught in one of those you'd starve to death before reaching orbit.
Indeed. Perhaps I should found the "Department of 'Orwell' Usage".
;)
You may mod me off-topic now.
If your bitterest enemies are people who hack the heads off civilians, then I would say you're doing something right.
Cite your references please. A lot of smart people have been working on this for a long time and they have actual data to back up their assertions. You do not as far as I can see. Just because you don't think it will happen doesn't mean it's not going to.
On the ground, an object moves forward at the speed of rotation of the surface of the earth; the same object, in geostationnary orbit moves much faster, simply to cover the much greater distance from the center of the earth in 24 hours.
So, presumably, as the object is moved up the elevator, it will need to be accelerated until it has the orbital velocity at the geostationary orbit height.
As the object moves higher, the cable will therefore not only have to support it vertically, but give it an accelerating shove to increase it's horizontal velocity.
To reverse the reasonning, the inertia of the object will tend to drive the cable backwards in respect to it's orbital rotation along with the earth; this backwards drive will have to be compensated somehow; either by putting small rockets along the cable, or by making it very taut with an extremely heavy counterweight at a very great height.
Let's make no mistake: the space elevator WILL NOT let you put a given mass in orbit for less energy.
Some points:
1: The Red Mars Elivator was much, much, much thicker than the one being proposed here.
2: Earth has a real atmosphere, where you can feel a 20 MPH wind...unlike Mars.
3: Due to 1 and 2, the fact that the Red Mars elivator doens't burn up doesn't even suggest that the proposed one wouldn't.
This sig wasn't worth reading, was it.
Also, the cable would not be like a string that someone waves around in a circle. As the article/review states, it is a very tall satellite in geosynchronous orbit. This means you wouldn't have to push the cable up or hold it down. You'd just have to hold onto it so it doesn't drift. :)
Karma: Chameleon (Mostly affected by the 1980s)
Doh! . My bad. Earth's circumference is about 40,000 km, so it's almost once.
-Looking for a job as a materials chemist or multivariat
I too enjoyed KSR's scene of the Mars cable's spectacular fall, but the truth is that the space elevator we are envisioning is extremely light in relation to the surface area of the ribbon.
Carbon nanotubes have a density of about 1.3 g/cm^3. So imagine a square meter of ribbon material = 1 micron * 1 meter * 1 meter = 1e-6 cubic meters = 1 cm^3, so our square meter has a mass of 1.3 grams! We're looking at a fall about as violent as a length of toilet paper!
Surely, right, Gravitational Potential Energy is our friend? mgh means that for every kilo, every metre, the energy converted in getting the vessel up to the top level is mostly reclaimed in the descent? Let's say that it's inefficient and only does 80% generation. Hey, that's reduced it to £20 a kilo! Wahey! Even for the heaviest guy, that's only £2000 to space! I'll be buying a ticket! The possibilities are almost endless! Oh, and for those morons (I presume you are, if you're not, check your passport, are you SURE it isn't American?) who are obsessed with terrorism, this isn't going to be a big target. The tower is not going to be massively wide, and is certainly not going to be able to be hit by terrorists, let me tell why. We build the tower on Hawaii. That gives you a few thousand miles of nothing to monitor for terrorist attacks. Not only that, but it's 100000 km's high! The highest an average aeroplane goes is 30km's! Come on! Plus the great thing about nanotubes is that if you do hit them, all you're going to do is send a shockwave - they're incredibly strong to lateral attacks, and the only way you're going to kill someone is if the wire has a vehicle on it already. Finally, if the USA doesn't do this, you can bet your bottom dollar that someone will. The Russians, maybe not. The Chinese, maybe. Hell, even us Europeans. One thing IS certain, it's not going to be manned. Not for quite a few years, until it's been tested to death, and some entrepreneur builds a hotel. Just my two pence.
This could have enormous military applications. Imagine the advantages of being able to lift an almost unlimited quantity of bombs and artillery to any point in orbit. Might even make the missile shield work.
We need another space race. Maybe if Bush thought that the Chinese were going to build a space elevator, he'd seriously consider it.
Alternatively, a certain rich individual with plans for world domination might invest. Slashdot's favorite villain lost or gave away something like $50 billion last year (according to Fortune magazine), and $6 billion isn't much more than his profit or loss from a volatile day on the stock market.
To do the necessary momemtum transfer to the earth, you'd have to have an impossibly stiff piston pushing the payload to geosync.
One thing I'd like to know is whether any thought has been given to disaster-aversion should, unhappily, the thing fails and breaks or is deliberately sabotaged to break. It would be the world's biggest terrorist target. If you sever the ladder anywhere along its length, the delicate balance holding it in place is gone, and the section past the sever point is flung out to space, while the other section falls, slapping the earth around the equator.
Don't label something "offtopic" unless you know the topic well enough to tell what's on topic.
You said:
One thing does bother me though... wont anything sent up the elevator need a horizontal boost eastwards (as well as power to climb) in order to bring it up to rotational speed as it rises?
Yes. The answer to this is that
you steal rotational energy from
the earth as you go up. "Look ma!
I'm making the earth spin slower!"
The above post I made was meant for the parent of b-bagginses post. I replied to the wrong message.
Don't label something "offtopic" unless you know the topic well enough to tell what's on topic.
It's a cable with a potential tensile strength in the 100s of GPa... I think the pilot would be in for a surprise when the cable just bends a little and slices the plane in half... ;-)
It's sort of like hanging a piece of kevlar from the ceiling with a weight a few hundred tons (assuming the ceiling won't let go, so to speak) and trying to slice it with your hand... which do you think will give first?
Doesn't the 1 micron thick ribbon sound similar to Sinclair Thread, from Ringworld?
If it falls over a city, could you pull one end and drop buildings?
Does it slice an off-course airliner in half as it flies thru?
Could I get large spider webs woven from it to drape across hallways to surprise unwitting burglars?
Something that strong could revolutionize several industries.
Truth isn't Truth - Guliani
Huh? How can a quote about building a tower to the heavens be inapplicable to an article about building a tower to the heavens? I am surprised that I was modded as "flamebait" for posting a simple, well-known, generally noncontroversial quote with no commentary whatsoever.
It honestly never occurred to me that I was saying anything inflammatory, especially in response to a gag article about Illuminati plots. I just thought that it was an interesting comparison---I am a Christian, but I have no Christian position whatsoever on whether the Space Elevator is a good idea. I am also a scientist with some aerospace expertise, and I find the science highly interesting.
Methinks that a few folks are a bit sensitive about religion...
Couple of _real_ scientific thoughts:
1) The conservation of mass and momentum are being infringed on here. Assuming that you build this thing, a tether will have a fixed energy equal to the sum of potential and kenetic energy (PE+KE)=E. Lifting something to GEO requires increasing PE of the something, this is said to be done with electric lift. But what about the KE that's orthoginal to the tether (called orbital velocity)? KE in the velocity vector has to come from the tether, electric propulsion won't help (no reaction mass in the orthoginal direction). The result is that the tether sees a force in the direction counter to the orbit. This force is integrated over time (the lift time) and distance, resulting in energy removed from the tether (PE+KE)=E. Either the tether loses PE (ie falls to earth a little more) or loses KE (starts to "slow" down) and loses omega. A loss of omega means that tether is no longer in a syncronous orbit and will begin to arch backwards in space. Lift enough mass, and the orbit of the tip mass will decay to the point where the tether rips itself off the anchor. The only solution is to replace the energy the tip mass needs (PE and/or KE). This means fuel, like rocket fuel. The bigger the tip mass, the more fuel you need.
Which brings us to the second point. The equitorial plane of the Earth is constantly changing in reference to the intertial frame. The amount of inclination change is ~45 degrees per year in a cycle. Most people understand this as seasons, over the course of the year, the Earth rocks 23 degrees North, then 46 degrees South and 23 degrees back North. The 46 degrees is inclination change that the tether and the tip mass have to deal with 24/7/365. Every day the tether and tip mass have to do an extreamly energetic orbital plane change. This energy comes from no where else but big rocket engines, which require fuel.
Sure, lift all the fuel to do these two manuevers every so often. I'm not saying it can't be done, but don't think the physics are straight forward and has been completely solved. Even the big guys doing the real research on this haven't solved this pair of problems yet.
One end dangles into the atmosphere. It is subject to wind pushing on that end, and thus upsetting the object's orbit. If it is in geosynchronous orbit, it won't have the friction braking problem low-earth satellites do since the atmosphere will be moving with it, but any windstorms will throw it off balance. (If the wind blows west-to-east, the ladder's orbit speeds up a bit and the ladder is "thrown" upward. If the wind blows east-to-west, the ladder's orbit slows and it falls.)
Don't label something "offtopic" unless you know the topic well enough to tell what's on topic.
The Earth rotates, 25,000 miles in 24 hours at the equator, that's some 1,000 mph. At the geosynchronous orbit the orbital speed is about 6,000 mph. Where would the missing 5,000 mph come from? The elevator would only be good for shuffling the same weight up and down, not for building a big space station.
Not you, just the naysayers in general.
Damnit, people, you just hook the earth end to a huge, powerful, fast winch. If it breaks, flip 'er on, and crank her down faster than she can fall. Have it pile up in a huge pile out behind the anchor, or just feed it down into the ocean, accordingly.
Duh.
Shit, I should probably patent that idea.
"Has [being a kidnapped teenage girl, raped repeatedly for months] changed you?" - Katie Couric to Elizabeth Smart
I can't imagine anything less than a 20km no-fly zone and substantial antiaircraft installations to enforce that. Said student pilot had better have packed a parachute.
Got time? Spend some of it coding or testing
Does the term `geosynchronous' mean anything to you? The thing spins at the same rate as the atmosphere, wind would more or less average out, excess weight on the end of the cable provides all the tension it needs to stay up. Next question...?
Got time? Spend some of it coding or testing
Remember -- the whole space elevector together acts just like a geo-synchronous satellite. It's just a particularly long and skinny one. Theoretically (barring any atmospheric effects, or other "noise"), it would "float" - no force would be required to anchor it down to earth (but due to the noise, some force would be required).
If it were cut in two, then it would become 2 satellites. The lower satellite (the piece closer to earth) would have a lower orbit, and therefore would require a greater velocity than it had, to remain in orbit. It would therefore fall. The top half would have a further-out orbit, and would be going too fast to remain in orbit. It would therefore escape orbit (i.e. would be flung out to space).
Look, the Shuttle debacle just illustrates my point that a real space program absolutely requires cheap access to orbit, and we need to move beyond rocket propulsion to make that happen. The Shuttle's engines boost within shouting distance of the theoretical limit for chemical propellants; most of the beast is at least sort-of reusable; and it still costs $20K per kg delivered to low orbit. There are ways to improve upon this, but I hope we can agree that we don't want nuclear-powered rockets operating anywhere near Earth's gravity well anytime soon.
The thing is, this insane transport cost is the show-stopper when contemplating any non-trivial project outside the atmosphere. Nothing technological prevented us from building O'Neill colonies in the '70s. Nothing technological is preventing us from building solar power satellites, or huge orbiting or Lunar telescopes, or hotels in geosync, or settlements on the Moon or Mars with scheduled transports twice weekly. The limiting factor is that no private organization can afford to boost several thousand tons of material into space, and no elected government would dare to try. (Some non-elected ones might, but they can't afford it. [g]) The transport cost has to come down by a factor of at least 100 to make these things possible, and there's good reason to think that even a completely reusable single-stage-to-orbit "space plane" won't cut it. Given this, any reasonable budget for R&D on a solution with potential to drive that cost to orbit down to a few $$ per ton is cheap at the price.
As to specific points:
Who the hell said anything about "a walk in the park?" I believe I was clear enough, by implication at least, that I was talking about a project on the scale of the Mercury / Gemini / Apollo programs. At it's peak, Apollo involved something like a quarter-million people and $20 billion / year (2003 dollars). Hardly a "walk in the park." The way I read the article, they were talking about $6 billion as the manufacturing cost of the elevator itself. R&D not included, and I suspect they didn't figure in the cost of shipping all those nanotubes up to geosync the soon-to-be-old-fashioned way. So what? So it takes 7 or 8 years and $100-odd billion to ramp up to build the first one. Still cheap at the price (maybe 10 years to recover costs through all the Shuttle flights that NASA won't have to conduct, and all the dumb boosters that the Air Force / France / China / et al won't have to launch), and the second elevator would come in reasonably close to that $6 billion, complete. Probably less. In 1900, the technologies needed for heavier-than-air flight did not exist. In 1962, the technologies to land men on the moon did not exist. What's your point? We have a solid theoretical basis for development of space-elevator technology, which is a lot more than Wilbur & Orville had when they started. Maybe. Does that make this project any less so? And I'd argue that you'd have a hard time finding such a project. There's something about exploration and New Frontiers that fascinates us insatiably-curious humans in a way nothing else can. Fun experiment: Have an AIDS or cancer researcher speak to a 5th-grade class. Then send an astronaut in. Guess which one spends an extra hour signing autographs.And now we have the possibility of developing technology which would be the equivalent of the Trans-continental Railroad, opening those frontiers to more than a select few and making "trade" with those pioneers dirt-cheap compared to what we have now. Even if nanotube construction ultimately proves to be impractical, isn't it worth a fraction of a percent of the national budget to find out?? As government programs go, it certainly beats hell out of corporate welfare and Lawrence Welk museums.
Life is like surrealism: if you have to have it explained to you, you can't afford it.
A potential issue might be such a topheavy structure once the payload is in geosynchronous orbit. It seems the further away a tethered object is from the base, the more stress and pull there is. Kinda like a kite that went too far up and the string broke. Since wind can be argued to be a factor, I will give other analogies. Imagine holding the string of a teather ball while spinning. If you have 1 foot of rope let out, the ball will not pull as hard as if 5 feet were let out. Quite similarly, recall one of those times at the county fair, aboard the Graviton. While the operator could stand casually near the center, if you were a foot away from the pad - forget it. Perhaps this was already calculated - I don't know if it was or not. I believe the concept is feasable, however anything less than perfection in design could be catastrophic (the break in kite string doesn't always happen near the spool). I normally would be unconcerned, however with news like NASA designs failing simply due to "centemeters, inches... what's the difference" or doctors giving patients organs as incompatable as they come, etc... this better be a perfect design which could even survive 1 airplane crash. I don't even want to know the implications of failure If my writing did not make sense, it's probably because I'm about to fall asleep... off to bed I go.
instead of ferrying the initial ribbon up with so many space-shuttle launches, why not just send up the carbon-nano-tube making machine to the International Space Station and make the ribbons up there. Maybe they can form stronger in zero grav anyway.
Gotta have a cool name or people won't pay attention. How 'bout "Space Noodle"?
A big risk - what if the cable broke? Sure the best engineers will try to make it over designed, but accidents, war and sabotage happen. In Kim Stanley Robinson's books "{Red,Green,Blue} Mars" he explores the consequences of a space elevator on Mars and it's failure. Those books though fiction were based on a lot of scientific research. On Mars the consequence would be the cable wrapping mutilple times around the planet total destruction of much of the equatorial region.
On earth the elevator cable would be much longer, much more massive and have much more potential and kenetic energy. At a guess you would lose at least the entire tropics, including any other space elevators, maybe you would lose everything (remember the shock wave will not decay with the normal inverse square law, in it may after a point not decay at all and refocus at the poles).
Such a system can not survive in a world not dedicated to cooperation.
While it might require more than two brain cells it is clear to me that the aborgation of the the Anti Basilitic Missile Treaty and the development of a Missile Sheild would quickly lead to an adversarory denying the use of space to all by deploying malicious space junk.
If that happens we'll all be stuck down here for a couple of hundred years while it all settles down.
You've got it backwards.
1 in = 2.54 cm
So 3.8 cm = 1.496062992126 in = 0.1246719160105 ft (approximately).
(Actually, my guess is that someone calculated that the Moon was moving away by about 1.5 in a year, and someone else converted it to Metric (1.5 in = 3.81 cm ~= 3.8 cm).)
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Enter the space elevator.
Basically, if we build a space elevator we get an answer to the long-term nuclear waste disposal problem, as a nearly-free side effect: a problem expensive enough to justify such a construction project in its own right, before we look into speculative items like 3He mining or space tourism.
For resonance to occur the structure must be fixed at both ends, causing waves to reflect back along the structure which build up until it collapses. This elevator would only be fixed at ONE end, any oscillations would just dissipate at the other end.
The lower wouldn't even be fixed really as it would be anchored to a floating platform that would be free to move about the surface of the water. This could generate some serious waves though.
Meme 4: Nothing Bad - its in the ocean.
While the Space Ribbon itself will be so light and Flat, it will presumably crumple like a dropped string. It could create a problem by getting tangled in one region, and then pulled along by the atmosphere, tearing up trees etc. but for the most part, a minor concern. The Payload climbers however will fall back from Space, and they will not burn up as the Space Shuttle. The Space shuttle is after all orbiting at great horizontal velocity, and uses aerobraking to counter act the rotational energy (Otherwise it would have to have nearly as much fuel for reentry as is currently used for launch - multiplying the launch weight by a factor of ten or so.)
Thus the payload will largly survive reentry and create a deadly but rather small impact - should the parachute fail. And this would presumably fall into the sea.
As brer Rabbit says when caught up in the trap of Brer Fox "At first I was afraid I'ez goinna fall, and then I'ez afraid I _Ain't_ goinna fall.
The real concern in the event of a failure is losing the elevator into space. The static state of forces is pulling out from the earth - tethered by the weight of the sea platform, therefore any break will result in outward drift.
There are two likely causes of failure, one is lightning - which would cause 100% of the remaining cable to drift, The other is terminal space junk or astroid damage, which would cause a jack and the beanstalk effect. Here again, the payload climbers will bring it down rather directly, and the fallout pattern would be small, and relatively straighforward to cleanup (Not like an oil spill for example)
LASTLY regarding LEO: I think solar powered unmanned gliders are a better solution for LEO problems (Satellite, communications, etc) and the space elevator puts nothing directly into LEO. What it does do is deliver payloads to oceanic equatorial geostationary orbits. Getting from there to LEO is still a lot of delta-V.
Terrorism (war, conflict) will stop when there are enough resources including food, water, education, and medicine for every man on earth to support seven virgin wives and seventy children in a palace with servants. A Space elevator does nothing to resolve this problem. Sorry.
AIK
Remember, once the counter weight shifts one direction or the other the force anchoring it in place is no longer veritcle, but has a component in the direction opposide to the movement. Remember, the anchor isn't at the center of the earth, but is placed some 8k miles away, so there center of gravity of the anchor/earth system won't be directly under the anchor point (i.e. the cable is slightly slanted and is draging against the anchor on the ground) The energy for the velocity change going into and coming out of orbit is actually coming from the earth's own inertia - granted, we still have to pay for actual lift costs.
The real problem is the fact that once the first mass has been raised the anchor is going to wobble back and forth like a pendulum - the timing of subsequent elevator operations will have be careful to avoid constructive interference.
The end of this tower would make a great place for a space station. Due to the centripetal effects at the space-end of this elevator, there would be an artificial gravity created away from earth. This would mean humans could have a more permanent presence in space without the drawbacks of life in a zero-G environment. First we would of course need to overcome the higher radiation levels at this orbital distance. Of course with cheaper transport up this would be less of a problem since heavier shielding could be brought up.
-this comment would be modded up if I posted it earlier =)
If an Elevator ever did get built here before we've evolved ourselves a bit more, I'd be holding my breath just waiting for the first kamikaze lunatic to try to crash a plane into the thing and send it hurtling!
That's air friction working gently but steadily to deorbit ISS. It won't be significant on a space elevator under any sort of tension, especially a geosynchronous one because that will orbit at roughly the same rate as the atmosphere that slows ISS.
Got time? Spend some of it coding or testing
The constraint of a 2m wide cable seems unnecessary in the first place. What is wrong with having a much thicker structure at the point of greatest stress near the LEO, and thinning out the farther it is from that center point, both up and down? The combined strength of many parallel cables made of cheaper materials such as steel, kevlar, or fiberglass should be equivalent to nanotubes (or nanoscrolls), and the redundancy of more parallelism will add to its safety as well.
How wide would it need to be? Maybe 200m or 2km is enough. I don't know; you tell me. But I doubt there is any physical reason that it can't be as wide as necessary to hold the remainder of the structure. The obstacle may be a practical constraint involving how this structure can be assembled, or how much material it would require, which implies economic constraints.
The construction process suggested in "The Space Elevator" involves a thin ribbon of nanotube material. If that were to work, the same process would apply to my suggestion as well, but instead of adding more nanotube cables along the whole length, first thicken up the middle with short strings, and then gradually thicken up longer portions of the cable. This also has the advantage of not requiring the first climbers to lift strings that are a large fraction of the weight of the whole ribbon.
But another process, that doesn't rely on any initial ribbon hanging down to Earth, would start at the LEO point and grow both up and down, always thickening in the middle enough to support the structure in both directions. The problem with this approach is where does the material come from? Lifting it up from Earth by rockets is what we want to avoid, hence the idea of mining it from an astroid.
Here's a related experiment that someone should try: Imagine flying a kite with a really long string, and after 10 meters or so you attach another kite with its own string, thus doubling the string width. Repeat after another 10 meters, etc. You should be able to keep doing this without using thicker strings because each kite only needs to lift its own string. The constraint is that the wind will only hold up a certain weight of string for each kite, and you run out of air after a while anyway. But each kite lower on the string will help hold up the string for the higher kites as well as holding up their own shorter length of string. So how high could the first kite go?
Daniel LaLiberte https://www.facebook.com/daniel.laliberte
i'm willing to donate 10$ to build this damn elevator .... anyone else ?
already
if every citizen on earth could donate 10 bucks, we would
have 60 billions ? should be almoust enough or what ?
[the sum is an average i guess, a chinese worker can't
afford 10$ , but an american businessman can surely give
it a 1000$ so it makes us all even i think]
gogogogogo spaaaaceeee !!!
[tired of sitting down here , let's go startrek crazy !]
I'd tell you the chances of this story being a dupe, but you wouldn't like it.
About twenty bucks a person based on US population estimates. I'd gladly invest a couple hundred bucks in this if someone want's to start it up as a private enterprise.