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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...
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!
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!
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.
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.
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
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
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?
I think you have to place a counterweight past (at? IANAPhysicist either) the geosynchronous point.
If your bitterest enemies are people who hack the heads off civilians, then I would say you're doing something right.
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'?."
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.
The space elevator satellite also extends a cable outwards, which balances the gravity experienced by the bottom part with the centrifugal psuedo-force on the top part.
This is also why a break on the planetside isn't the disaster most people think it would be; the part below the break falls to the earth, probably at not too great a speed, and the part above the break floats out into space.
A break above the satellite is worse, but there are ways of helping that too. One interesting, albiet possibly controversial idea, and bear in mind I'm just thinking of this right now, is to deliberately set up explosives/chemicals to cut the elevator at certain intervals, so if a break does occur, you cut an equivalent amount of the cable off the other end so the body of the cable and the satellite are still salvagable.
Also, since you can lift so much, any manned vehicle can be made safe as long as the explosion doesn't occur onboard (obviously); there's enough weight available to make a vehicle that can land safely on the Earth. (Look at the pods for the Apollo missions; it doesn't take too much to splash-down safely, compared to what it takes to get that high in the first place.)
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
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)
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.
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....
Try this exercise in backyard physics: Tie a rock to the end of a piece of rope. Hold the other end. Spin around and watch the rock fly and observe the tension on the rope.
You don't need rockets to keep the rope tight - the energy comes from the rotational energy you are providing. In the case of a space elevator, the Earth's own rotation provides the tension.
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
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
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.
According to my "Nasa's big book of imperial/metric conversions", these are actually the same length.
Rich
-
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.
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.
Ni! Ni!
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.
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.
...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?
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.
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