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Space Elevators Going Up
MikShapi writes "CBC is running a new piece on the Space Elevator. Nothing dramatically new, as we're all still waiting for one of the many Carbon Nanotube research centers to announce they reached the famous 100GPa red line from page 10 of the NIAC Phase 2 Report, thus obtaining 'unobtainium' [pun intended], the material necessary to build the Elevator. The report predicts this will happen during the course of the next two years or so. It's then that the fun really starts - A REAL all-out space race, open to everyone with will and a national budget, winner probably getting to own space [read last paragraph]. In the meanwhile, we can all spread the word, discuss, debate and brainstorm every nook and cranny of the program here on Slashdot, and give Edwards a shoulder by giving the program every bit of mass-exposure we can."
The Fountains of Paradise by Arthur C Clarke and Red/Green/Blue Mars by Kim Stanley Robinson. Both discuss the politics and sociology surrounding the construction and use of a space elevator. Good books, well worth a read.
Tubal-Cain smokes the white owl.
Unobtainium is a term for non-existant wonder materials. In this case carbon-nano tubes are unobtainium. As in unobtainable.
Unobtainium; A general term for any material that is, for all practical purposes, impossible to obtain!
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Not two years away. More like fourteen. According to the article, it would be two years away once research has produced the proper technique for creating a cable, and once someone produces 650 tons of the stuff. Earlier in the article he mused that they were 12 years away from such a thing.
I'm a physicist, and I work with carbon nanotubes. In October's Macromolecules, there was a paper put out called "Phase Behavior and Rheology of SWNTs in Superacids". It was done by a huge group of people (for a nanotech paper), including Nobel winner Richard Smalley. A press release about it was posted here somewhere.
To make a long story short:
They did it.
By finding a way to dissolve nanotubes, then slowly concentrating the solutions, they formed a liquid crystal of nanotubes. By extruding this through a syringe, they formed an aligned, macroscopic, nanotube rope.
I've seen this stuff... somewhere, and it looks just like black string.
What's left?
They used tubes grown by high pressure carbon monoxide, which leads to a lot of defects. If they switch to methane, the defects will largely be gone, but the yeild drops.
They probably need to chemically connect the tubes. You can do that with an electron beam, but that would be a pain industrially. I'm sure there's a way around it.
I'm sure that same group of people has already figured out many more problems and solutions than I can think of. I havn't seen anything out about the mechanical properties of these ropes yet, but I would expect something within a few months, and I would be surprised if it wasn't amazing.
I used to be a skeptic when it came to a space elevator, but now...
As far as countries on the equator go, Ecuador's competition consists of Colombia, Brazil, Sao Tome & Principe, Gabon, Republic of the Congo, Democratic Republic of the Congo, Uganda, Kenya, Somalia, Maldives, Indonesia and Kiribati. I reckon they've got a shot!
It's amazing, it reminds me of the Manhattan Project.
At the time the scientists were looking to get enough Uranium (238) and Plutonium to build the bomb. Everything else around was ready but they were producing only grams of the required materials a week.
In only 2 years they improved the production quality and quantity dramatically to levels they didn't even dreamed of before.
That's when they understood that what they though was granted long before (the 'rest' of the engineering needed for the bomb) was the actual hardest part to 'build'.
Maybe this will happen to the space elevator with the nanotubes.
Iraq: war to save the U
Well Buckminsterfullerenes were origionally VERY rare and hard to make. Then the carbon arc method using high pressure rare gas atmosphere was developed and suddenly they were abundant. Hell I made such a device for my senior year independant study program in high scholl back in 1996-7. These would typically make a fairly high percentage Buckyballs in the soot but I don't think many buckytubes, I assume they are waiting for a similar process for making buckytubes.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
The station is not only intended for putting things in orbit or for cargo purposes, but also for experimentation. The space elevator can only get the stuff/people up into space, but without a place to put them they arn't much use. Therefore, the ISS is still just as important as it was before, maybe more so. With the ability to more cheaply and easily get experimentation materials to the station, experimentation in space will become cheaper and more widely available. Perhaps with this new space elevator students can even go beyond the "vomit comet" and actually go into space. One easily accesible space station will inevidabley lead to others, soon.
With the competition that all of this new technology is/will be producing, a commom point like the ISS is important to unite the major countries.
where are we going to find a big enough rock to attach to the other end?
According to the book, the plan is to send up a rocket with the smallest possible cable. The cable gets lowered to Earth and secured (cable also gets spooled out in the opposite direction, in order to keep the spacecraft in orbit). Then they send up a series of progressively larger robots along the ribbon. Each robot adds more material to the ribbon as it climbs, and when it gets to the top of the ribbon, it stays there to add to the mass of the counterweight. So basically we bootstrap our way up.
I don't care if it's 90,000 hectares. That lake was not my doing.
The real barrier is going to be whether or not it'd be dangerous if it breaks or if it's cut.
I remember reading about this concern somewhere. The idea was that the carbon nanotubes would be stretched almost as thin as paper. Should the ribbon break all that would happen is the ribbion would float back to Earth like paper and no one would get hurt.
The now defunct www.highliftsystems.com website had a faq where thay had examined a number of failure modes of a nanotube ribbon space elevator. They had concluded that any fragments entering the earths atmosphere would probably shatter into small pieces rather than coming down in large chunks.
The figures the article quotes are that the cable would be about 100,000km long, one meter wide and way app. 650 tons, that would mean each square metre would be 6.5 grams, thats about a tenth of the mass per square meter of standard photocopy paper.
According to page 19 of the report, under the heading of Ribbon Infall,"The raw numbers suggest that the worst case cable infall is not as bad as the best case, nominal operation of current rocket programs."
Granted, they supply no numbers and they explicitly state that they have done no serious quantitative analysis of this, so I'm curious how they came to his conclusion.
Nature has spend along time doing research for us. So you root the thing like a tree.
As for vibrations you make a cable whis is made out of many smaller cables all of them at slightly different tensions so that they vibrate at different freqs.
The cable is "holding" mostly its own weight. Therefore, if the material is not at the critical strength, the elevator can't be built. (not disagreeing with you about the difference from lab to real life tho)
Except of course that the cable is stationary from the surface of the earth all the way up past geosync orbit (30,000k's).
The ISS however, is moving at about 6-7km/s, in a different orbital inclination, barely a few hundred k's up. Getting material from the elevator to the ISS is going to be rather tricky.
I hope they've done all the sums involved with regards to moving the base of the cable around a bit, wouldn't want it to get severed by a LEO satellite.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
There is one problem that doesn't seem to be addressed -- the problem of imparting the necessary angular momentum to the elevator car as it rises.
As the car rises, from the point of view of the ground, it will appear that the car is dragging the tether westward. As the car continues to rise, the angle of the tether-bend will increase, pulling the base station down into a lower orbit, If the system doesn't "crack the whip" and snap off the sky station, or induce a huge oscillation in the tether/sky station, it will at the very least leave the sky station in a lower orbit, and the tether "slanted" westward. The more mass you send up the tether, the sharper the slant, and the worse the problem becomes.
The following experiment graphically illustrates the basic problem. The "space elevator" does not behave like an elevator.
Take a long piece of string or fishing line and tie a medium bolt to the end. Go outside to a large open area. Take a second bolt of similar size, thread it through the line, and hold it in your hand along with the free end of the fishing line. Now start spinning in a circle and let the line play out until the bolt is spinning at the end of the line. For the purposes of this demonstration, you are the earth, the fishing line is the elevator, and the tied bolt is the space anchor. You are looking straight "up" the elevator tether at the space station at the "top". Notice how your hand (the base station on the surface of the earth) is moving fairly slowly (with respect to your torso, the core of the earth), but the bolt at the end of the line (sky station) is whipping around at high speed? This means that the bolt on the end of the string has a lot of angular momentum, and the bolt in your hand has considerably less angular momentum. Now let go of the bolt you are holding while you continue to hold the string. The "elevator car" bolt will proceed to travel "up" the string into space until it comes to a stop at the "space station." However, the bolt will NOT simply rise straight up the line like an elevator car. Instead it will drag the line in the direction opposite to the direction you are rotating, and will "crack the whip" somewhere near the end of the travel. When you are all finished, the line will be oscillating "east to west" (forward/backward) relative to your hand.
Not what you may have been expecting based on the conceptually flawed "elevator" analogy.
Now there are limits to this demonstration. For instance, the actual elevator car will be speed controlled, not flying freely like the travelling bolt, and there are massive differences in scale and speed. But even if you solved all the engineering problems you can, the basic problem of conservation of angular momentum remains, and it's a show-stopper.
The oscillation problem could theoretically be avoided by carefully timing the rise of the elevator car, but the killer is conservation of angular momentum. As the elevator approaches the sky station, it will drag the tether westward and pull the sky station into a lower orbit. It can't help but do it, because as the elevator car reaches the sky station, it is going to have to match speed with the sky station. In order to do this, it will have to "steal" some angular momentum from the sky station, and even in a best-case scenario, where the timing is done absolutely perfectly and no oscillation is induced, the system will balance the equation by dropping the sky station into a lower orbit, and leaving the tether "slanted" westward. Bringing the elevator car back down again (perfectly timed once again to avoid oscillation) would straighten out the tether, but if the purpose of the space elevator is to sling things into space, then it becomes clear that the entire scheme isn't going to work. Any object lifted to the sky station is going to "steal" angular momentum from the sky station, and once you let go of anything, you will never get back that angular momentum, and there will be no way to straighten out the t
On the contrary, The King James Dictionary on Studylight.org says that meek means "Gentle; tender; free from pride." So does the one at Blue Letter Bible.
The Greek Concordance with Strong's Numbering says that the word in Matthew 5:5 was originally (in Greek) "praus", which it translates as "mild, i.e. (by implication) humble".
So in that spirit may I humbly suggest that you or your professor are perhaps mistaken.
"Lord, grant that I may always be right, for Thou knowest that I am hard to turn" -- A Scots-Irish prayer
According to Strong's Concordance, the word in the original Greek is "praus" (latinized spelling) which means mildness of disposition, gentleness of spirit, or meekness. If this page doesn't load, go here, type "meek" into the first line, submit, find Matthew 5:5 and click on the number 4239. This word is close to the modern Greek "praos" which also means "meek."
In other words, Jesus was saying that the humble and mild-mannered will inherit the Earth. You can find this same word commonly translated as meek in 1st Peter 3:4. Also, if you look at the context of Matthew 5:1-13, the opening of one of Jesus's sermons, it's quite clear that he's saying that rewards await the humble and downtrodden. They "are the salt of the Earth" and there is not an aggressive or angry group among "the poor in spirit," "those who mourn," "the meek," "those who hunger for righteousness," "the merciful," "the pure of heart," or "the peacemakers."
I'd be very surprised if Strong's Concordance was wrong on the issue given the context and the modern descendant of the word. I'd love to see some evidence for your professor's claims.
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
But according to this 2003 article, "Pet owners are expected to lavish $31.5 billion on their animals" - more than twice that total!
Hey, you got to take care of your pets and all that - nobody's arguing that. But people have to have a sense of proportion. We spend less on NASA than we spend on dogfood? Then maybe the cost-benefit ratio makes a little more sense.
"Lord, grant that I may always be right, for Thou knowest that I am hard to turn" -- A Scots-Irish prayer
1/625 is not the odds of the thing falling down overall...that's of the odds of it falling down because of the Leonids in 2031. To put it another way, there's a 1/625 chance that it will be destroyed if it is actually in the sky between 6-12 pm November the 17th 2031.
There's a 1/100,000 chance of being destroyed by the leonids in any one of the 'minor' leonid years. And this is ignoring all of the other mundane risks such as cumulative damage by oxidation and the like.
None of those mundane (or outlandish) things you mention have anywhere near that kind of risk profile.
Laugh while you can, monkey-boy!
It's not really too complicated. You just need to get high enough for your potential energy to equal the energy you want at your desired orbit, then drop into that spot. You'll keep falling until your kinetic + potential energy = your initial potential energy. You need to get the angles right and everything, of course, and you might need a little rocket burn here and there, but that's just calculation.
The space station is still a waste of time, though. If you have a space elevator, you can lift the whole damn station into orbit on it.
I don't hear that kind of optimism coming from the scientists.
Rather, there is talk of an ocean platform where you've got nothing for hundreds of miles, including air traffic. That way there's plenty of chance to intercept anything even remotely heading into the area.
An aircraft carrier, a sub, and a couple of patrol boats could then do the job.
*This assumes that each section of the elevator has the same mass as any other equally long section.
Laws are horrible moral guides, moral guides make even worse laws.
While there is a difference between achieving 100 GPa over very short lengths and over 100,000 kilometers, it's not as much as you might think.
The longest individual nanotubes we can reliably produce are on the order of a couple of centimeters. But once we have nanotubes on the order of a meter long, they will probably be sufficient to produce a long ribbon with sufficient loading on the nanotubes themselves.
The limiting factor is not the length of the nanotubes in a composite (beyond a certain point, anyway), but rather how effectively the nanotubes themselves can be made to bear the load. Nanotube exteriors are slippery, like graphite, so the challenge is being able to stick them together in a substrate the transfers load effectively between them.
For this, a process known as "functionalization" comes into play. This basically means adding small appendages to the nanotubes so that they have more traction within the substrate.
LiftWatch.org carries regular space-elavator news items. Here are some recent articles on CNT advances:
Can you say "bullwhip the size of a planet"? I would NOT want to be beneath the path of that thing if it broke. The tsunamis would be interesting too.
Actually, there should not be too much of physical backlash or impact from it - the majority of the cable would burn up when entering the atmosphere. The main danger, as covered in the article and Edward's report, would be the danger from inhaling nano-tube particles. Some early results of rats exposed to nanotube inhalation have been pretty negative.First Falcon-1 to orbit, then Falcon-9. Then I can die a happy man.
I think one of the places that they are currently considering is just off Perth Australia. I am ont sure about Cayambe, Equador, but they are looking for an Ocean based anchor point for the elevator so that the base can easily be moved to help it dodge satellites and debris. Additionally, it needs to be in a region of low lightning activity and low hurricane/intense winds, as intense weather activity could threaten the elevator, particularly during early phases of it's construction. For some of the criteria that would be used to find a anchor location, check out Edwards report.
First Falcon-1 to orbit, then Falcon-9. Then I can die a happy man.
Check the bottom of this page. Of particular note:
We've all benefited greatly from weather and telecom satellites.
Note these are both forms of information -- to get physical goods and energy, it's still much too expensive. Thus a radically cheaper way to get to orbit will make much more possible (solar energy collection, asteroid mining, to pick a couple at random).
sending a rock with a 100,000 km long ribbon attached to it into space.
I do appreciate the joke, but if you were to actually cut that ribbon at ground level, all that happens is that the space elevator goes into a slighly elliptical orbit: the cut end of the ribbon ascends a few miles into the atmosphere only to come back down 12 hours later to pretty much the same location, where it can be snagged and re-anchored (same procedure as when the elevator is first lowered from orbit). A mishap for sure, but nothing more.
Be faithful to your obsessions. Identify them and be faithful to them, let them guide you like a sleepwalker. JG Ballard
One thing I really question is the claim that there will be or can be only one final winner in "owning" space.
One word for you: Microsoft.
Not a monopoly cast in stone for all time, but a small player that is in the right place when a major new frontier (with subsequent exponential growth) is opened, can go on to lock competition out of the market for decades. This should be well undertood on slashdot of all places.
The most economical way by far (factor of 1000 or so) to build the *second* space elevator is to use the first one to lift the components. This provides a very simple way to lock out the competition: refuse to lift their CNT ribbon. Add to that the headstart in the technology and practical experience operating the things, and it looks pretty likely that whoever owns the first space elevator will own all of them for quite a while.
Actually, an even better analogy than Microsoft are the railroad barons. Do the names Vanderbilt, Carnegie, etc. ring a bell? Most of the "old wealth" in the US is still in the hands of those families whose ancestors controlled for a few decades the only economic means of transport to the American West.
Be faithful to your obsessions. Identify them and be faithful to them, let them guide you like a sleepwalker. JG Ballard
The carnage that such an event would wreak absolutely beggars the imagination.
The carnage would be non-existent. The proposed ribbon has the approximate shape, weight and composition of carbon paper (remember those?). All but the lowest few km would burn up in the atmosphere. The rest might land on your head with all the force of a fluttering sheet of newspaper.
Read Kim Stanley Robinson's Red Mars. Skip to the last few chapters if you just want the space elevator stuff.
The truth doesn't always make good fiction, and good fiction doesn't always tell the truth.
Be faithful to your obsessions. Identify them and be faithful to them, let them guide you like a sleepwalker. JG Ballard
The true reason for 'dominance' is the amount of MASS that the space elevator would allow to be lifted. If they devoted some of the lifting capabilities to military use, they'd be able to lift enough kinetic-kill satellites to prevent any other country from building another, as well as being able to kill any launch from space (if they're willing to go that extreme). A little more mass, and they'd be able to strat-nuke any country/area they wanted, for the ultimate in extreme. Military doctrine still holds that holding the high ground is critical to victory. Right now the orbitals are the 'high ground'.
I don't read AC A human right
No, actually the middle floor will have no gravity (geostational orbit).
The top orbit will have "gravity" in exactly the opposite direction because it's spinning faster than than the required speed to stay in orbit. It has to pull on the cable to keep it from falling down.
It is somewhat like going through the earth. As deeper you go the gravity will diminish. In the middle of the earth: None. On the other side the gravity will increase again but in the opposite direction.
Have you ever looked through the Forbes 400? "Old money" in the US is largely a myth.
The ten wealthiest individuals in America are Gates, Buffett, Paul Allen, Larry Ellison, Michael Dell, and the Walton heirs. (Steve Ballmer is 11th, incidentally.) Of these, only the Waltons inherited their money, and that not from some ancient rail baron, but from a self-made man who died in 1992.
All employees must wash hands before seeking equitable relief.
No tension eh?
So the cable stays taught because it has hairspray on it?
Sigh. I actually thought you might have read something about the space elevator concept.
The cable stays taut because of gravity. There is no tension between the cable and the ground. There is, in fact, no reason that the cable needs to touch the ground at all.
The cable remains taut because the center of mass is in geosync, and the inner cable needs to keep up with it - tension.
Imagine a spacecraft at geosynchronous orbit which extends 1 meter of cable downward, and 1 meter of cable upward. It, of course, stays at geosynch, because its center of mass is still at geosynch. Now have the spacecraft repeat that thousands of times, until the cable reaches near the Earth's surface. That's a space elevator. Don't think of it as interacting with the ground in any way. It isn't.
Cut it at the bottom, and it goes in orbit.
I'm sorry, but you're wrong. The cable already is in orbit . Cutting it at the bottom will simply move its center of mass infinitesimally higher, and will simply make it drift to the west very very slowly. Obviously it won't come back to the same place 24 hours later, so that part of the post was completely wrong. But cutting it at the bottom won't do anything. The cable will likely just sit there.
Ballparking some numbers: if you cut off the bottom 1 km of a 100,000 km cable, that will move the center-of-mass out about 0.001%. The cable's orbit was at a 24 hour orbit, and orbital periods go as proportional to the 3/2s power of the radius, so the period will increase about 0.001% (this is *really* ballparking). This means that the period increases by about one second per revolution. Something at the Earth's surface moves about half a kilometer a second while rotating (40K kilometers in ~ 80K seconds), so this means it moves about half a kilometer per day to the west. This means that it moves about 5 millimeters per second to the west.
Considering all they need to do is spool out 1km more cable downward, I think they might be able to recover it.
100GPa is only about ten times as strong as good steel.
You've missed a zero - last time I've checked high-strength steel alloys were below 1 GPa.
The "cable" is going to have to be pretty substantial.
You're missing the point: since virtually all the tensile strength is required to support the mass of the ribbon, that ribbon must perforce be both extremely tough *and* extremely light. Plans call for a ribbon weight of only 7.5 grams per meter, which is actually less than a sheet of laser printer paper.
I think it would hit the ground, relatively intact, at supersonic (but nowhere near asteroid) speeds.
Nonsense. The proposed ribbon is made of carbon, and thus has the aerodynamic and chemical properties of an extremely long and tough piece of paper. In other words, any pieces accelerated to high speed by orbital dynamics will burn up; any remaining fragments will flutter harmlessly. The only extant concern is the potential release of (potentially carcinogenic) free carbon nanotubes; this needs to be investigated.
All of which you would already know if you'd bothered to follow the link I provided instead of arguing from ignorance.
Be faithful to your obsessions. Identify them and be faithful to them, let them guide you like a sleepwalker. JG Ballard
The cable already is in orbit . Cutting it at the bottom will simply move its center of mass infinitesimally higher, and will simply make it drift to the west very very slowly.
Not quite - it will depend on how the SE is actually being used at the time. Consider: the SE must remain in GEO *when loaded* at the bottom at its maximum payload capacity, or else it would come crashing down. Thus when operating at less than maximum capacity, the anchor must supply the missing mass to balance the SE, so there will be tension at the anchor point. When the ribbon is cut in such a situation, the SE will go into an elliptical orbit.
If 15 tons of payload are cut off at the anchor, this actually corresponds to the mass of 2'000 km of ribbon. I guess the counterweight at GEO ameliorates this, but I can't calculate by how much. (The very first counterweight can't be too massive since it will have to be lifted by rocket.)
Be faithful to your obsessions. Identify them and be faithful to them, let them guide you like a sleepwalker. JG Ballard