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Space Science

Stepping Closer To The Space Elevator 255

Posted by Hemos from the going-down-mr.-tyler dept.
multicsfan writes "This article at Space Daily indicates that one of the major stumbling blocks against the space elevator has a potential solution. What do you make the elevator from? What's strong enough? It appears that carbon nanotubes may meet that requirement with a strength twice the minimum estimated." Now the problem is just getting a process that can get us from growing 4 mm in length to 47,000 km - I've got Wallace (and Gromit) working on it now.
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Stepping Closer To The Space Elevator More

Stepping Closer To The Space Elevator

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  • Technical Information on Bean Stalks (Score:1)

    by Anonymous Coward
    Here's a link [homoexcelsior.com] with some basic info about beanstalks (the 5 technologies required, etc...) and a link to the NASA white paper. This should help explain some of the questions I've seen posed here regarding the propultion of the elevator cars and the carbon nanotube requirements.

  • Details, math, etc... (Score:1)

    by Anonymous Coward
    Does anyone have any explanations or links to sites with details on the physics behind a space elevator? As in actual calculations. It would be a nice resource for people interested in what would be required to get one of these things built, as well as generate interest and educate.

    For example, I can understand the purpose of a counterweight. Not hard. Problem is, without knowing the numbers, it's hard to see what options are feasible or not. What mass are we talking about here (for the counterweight in space)? What force is required to get that mass up into space, if moving an asteriod is not a feasible option? Could the mass be replaced by an engine that always fires away from earth? How powerful of an engine would be required? While the suggestion of a large rock as a counterweight would be feasible, what other solutions may be feasible, e.g. could a nuclear engine provide enough thrust? What about a space sail (for the half or whatever time when the geosyncronous orbit allows a space sail to be used)?

    Similarly, I'm wondering why an earth-based building is necessary. Does the end of the elevator/line actually have to be in contact with the earth, held? Could we carefully balance the line such that the need for a large building is necessary (this and past articles mention the huge buildings necessary)?

    Yeah, what I'm aiming for is whether a continuously firing engine in space could act as an appropriate counterweight, and with enough control, be used to eliminate the need for an earth based building. Having a site with the numbers would be nice, so I could answer these on my own, and educate myself as to the details required to carry out this project. Yeah, I could have someone just answer these questions straight out, but I wouldn't learn anything consequential and maybe contributory in the process.

  • Re:Oh, cool! (Score:1)

    by Anonymous Coward
    The main problem seems to be the amount of carbon to make the tubules.

    Um, have you ever heard of coal? It is well over 90% carbon. Carbon is very abundant. The problem is growing nanotube fibers of sufficient length. The current processes for building nanotubes is completely slapdash. The result is black soot that the researchers must sort through to find buckyballs or nanotubes. I am sure people are working on more efficient manufacturing processes, but I haven't seen anything better yet.
  • Not just any elevator music... the muzak version of "Stairway to Heaven", over and over and over...
  • I think you mean everyone with an ID over 500 is new :-)
    --
  • Once a space elevator gets biult, it's the people of color who would control access to it, and they would be able to impose their own worldview on space access.

    Yeah. 'cause that worked out just that way for that whole Panama Canal thing, right?

    ----

  • I agree with "Red Mars" (Score:3)

    by Skyshadow ( 508 ) on Tuesday May 08, 2001 @11:40AM (#236709) Homepage
    I think the writer of "Red Mars" had the real issue with this thing down: it'd become the biggest target for terrorism in history.

    Why hijack a commercial jet liner when you can send an orbiting base flying out of the solar system?

    ----

  • If Libya built a space elevator, nobody else would do a goddamn thing, because Libya would have a huge advantage.

    But the US is going to build one first.

    And nobody else is going to be able to do a goddamn thing about it. (except the aussies, who will probably just pass an ordinance forcing all women to wear turtlenecks so the americans don't look down their shirts.)
  • I would guess that though the main supporting member is 10cm thick at the base, there would be a vast infrastructure surrounding the beanstalk, and attached to the beanstalk all the way up, allowing more than one elevator to climb it at the same time.

    Think bandwidth.
  • At $1.50 per kilogram (for simplicity):

    Cost for me to ride up: $163 USD
    Cost for my wife to ride up: $78 USD

    Cost of my wifes luggage to ride up: Twice the current national debt!!!
  • Cut at the bottom, the whole assembly would enter Earth orbit. The question of whether parts of it would ever hit the Earth would depend on the solutions to a hell of a lot of differential equations.

    Remember the counter weight? It has to be going at the same speed as the elevator but is at a higher orbit so it would drag all the structure in space...

  • I'm getting confused.

    Wouldn't spliting it into stages reduce the likelyhood of it whiping the equator into a frenzy ?

  • The other thing is that this elevator cannot be a direct lift into orbit. In order to work you need to break the climb into stages. The 1st would be a conventional aircraft up to a floating platform ( think 30 blimps in a cluster ).

    The second and 3rd stages would also be blimp clusters but at increasing altitudes. That gets you well above the stratorfare and hence above weather etc... You then have the final hop to a low orbit satellite or space station...

    Not as convenient as the original plan but this could possibly work without damage to the strand causing the whole thing to come crashing down in an unplanned manner ( Planing is key since the station would likely be bigger than Mir. If it comes down you better make sure it lands in the ocean. I can't imagine the kind of liability suite you would face for wiping out a small town.

    PS: The individual stages could also tumble but spliting reduces both the risk and the extent of damage if it hapens.
    --
    Quidquid latine dictum sit, altum viditur.
    Whatever is said in Latin sounds profound.
  • I read a really nice article about this in Popular Science YEARS ago.
  • Robinson himself admits that he was grossly over-optimistic in his timescale for terraforming Mars. Even with all the techniques he suggests, it would take several times longer. An interesting alternative I once heard about is the "world-house" (cf green house) a plastic skin holding down a km or so of breathable atmosphere near the surface, supported on pylons. Surprisingly, the physics can be made to work out without ridiculously strong materials, and the skin can be built progressively.
  • It's called a solar chimney, and they work with current technology, at least in pilot and demonstration systems. Large scale economics are another question, but it's possible. (Depending on efficiencies it may be worth covering the collector at the base with photovoltaics and just using the waste heat absorbed to drive a chimney.)

    http://www.ccom.lk/energen/solrchmn.html
    http://www.me.ufl.edu/SOLAR/chimney.html
    http://www.google.com/search?client=googlet&q=So la r%20chimney
    http://www.amazon.com/exec/obidos/ASIN/393069869 2/ qid%3D950759721/sr%3D1-35/bargainsolarcom/107-9764 317-8756526

    --
  • "The financial investment in such a project would dwarf all other civil engineering to date." You obviosly haven't heard of the big dig....

    I'm well aware of Boston's "Big Dig" Central Artery / Tunnel Project - I lived in Boston for many years & still contract there.

    The $14 Billion of the "Big Dig" wouldn't cover the development & deployment of the spacecraft required much less their operation or the actual construction of the Space Elevator.

    Good to see the old towne hasn't become any less provincial.

  • Capturing a NEO is a lovely idea. However that would also require the development of yet more exotic technologies of which we're only now beginning to dream of.

    1. NEO's would need to be surveyed; we need a better understanding of their composition & structure.
    2. A factory capable of working autonomously in micro(nano?)-gravity & vacuum must be designed (humans would be another order of problems.)
    3. The factory would then need to be launched & assembled in orbit, then somehow transported to the candidate NEO (which generally have a very high delta-v in regards to Earth.)
    4. This factory would then be required to install itself, deploy collection systems & begin refining local materials.
    5. We have to assume that the local materials would be suitable for the type of production required.
    6. Some sort of motor would need to be constructed or installed and the orbit of the NEO shifted to match that of Earth/Moon system.
    7. The NEO would steered (safely) in such a manner it can be captured (safely!) around Earth in an orbit relatively undisturbed by lunar effects & presumably geosynchronous.
    8. Once in place the cable would need to be deployed in a controlled fashion.
    9. The cable would be required to have a number of fantastic properties including:
      • Flexibility
      • Durability
      • Incredible tensile strength
      • Resistance to corrosion from upper & lower atmospheric gasses
      • Be unaffected by solar radiation
      • Be unaffected by the Van Allen belts
      • Possess whatever electrical characteristics are required
      • Possess whatever magnetic properties are required.
      • Be flawless or at least capable of withstanding flaws.
    10. Then of course the lower end would have to deal with atmospheric & electrical conditions as it is constructed then finally navigated to it's tether point.
    11. Finally the entire structure must be safer then virtually anything ever before designed by humanity because of course any failure on it's part could be a catastrophe of a scale never before seen by mankind.
    12. The political & financial will to undertake such a project would need to be built & sustained for many years.

    Somehow I find that a very daunting list of requirements.

    I'm not knocking the NEO idea, I'm just pointing out it's not a slam-dunk of a solution.

    Please no one glibly answer "nanotechnology". Even if we could build the basic parts required there are still the command, control, and power-requirements of a nanotechnology-solution that promise to be at least as difficult as building the darn things. Answering "by clicking our heels together 3 times" would be as honest an answer at this point.

  • First of all the esteemed Kim Stanley Robinson is only the latest in a long series of authors to discuss Space Elevators, indeed their pedigree goes back to the 1940's. Arthur C. Clarke was the first to bring them to wide attention in his novel "The Fountains of Paradise".

    Space Elevators work by orbiting synchronously with the Earth. Indeed due to their stationary nature they're often referred to as "beanstalks" (Jack and the...) There are other designs where they instead act as a giant rotating spar slicing down through the atmosphere and back up again but the most popular is where they're tethered (anchored is probably too strong a word) somewhere on or near the Earth's equator.

    Many designs truncate the outer-end of the cable, instead substituting some sort of counterweight such a captured asteroid. For vertical transport sealed cabins would be used for passengers, unsealed would do for hardy cargo. The technologies wouldn't be very exotic, indeed they could be built today by anyway halfway competent Jr. Technical School.

    Most designs have the cabins ascend & descend using electric motors (none using winches & cables found in the more traditionial elevators.) The motors themselves needn't be anything special, anything that can lift the cabin in 1G would do fine. Another alternative would be some sort of magnetic drive, Lawrence Livermore's Inductrak being one good candidate.

    Power requirements would be fairly modest & using the electric motors as electrical generators on the down trip could recover much of the power used. A single large power station would be enough with today's technologies, or possibly several solar satellites using future technology.

    However there are a couple of fundamental problems that are evident even from this far away.

    • Carbon nanotubes have thus far only been created in very short lengths. Scaling them up hasn't been achieved yet.
    • There isn't a good mechanism for bonding, braiding, or otherwise welding together the nanotubes.
    • The mechanical, electrical & chemical properties of the tubes are still being studied. They may prove to be unsuitable for this application.
    • Carbon is flammable, be it as lumps of coal or as diamonds or as nanotubes.
    • However recently other materials then carbon have been formed into nanotubes so it may not be the only choice.
    • We don't have a way to get the construction materials into orbit from where to begin building. An expansion of space shipping by several orders of magnitude for an extended period of time would be required to ferry up an elevator's components from the planetary surface.
    • As others have pointed out the dangers of a disrupted elevator would be significant, indeed catastrophic.
    • The financial investment in such a project would dwarf all other civil engineering to date. While the payoffs could well be incredible the risk would be great & the markets unproven.
    Space Elevators may well indeed prove in the long term the best way to get between orbit & a planetary surface. However they're a way off in terms of materials alone not to mention finances & other practicalities. Even if we were to develop a magic fiber tomorrow with all of the necessary properties it would be several decades before we'd be in a position to use it. That said it's never too soon to start laying the groundwork.

    I purposely didn't look up & embed URLs into this: Clearly you're already online if you're reading this so paste the interesting bits into your favorite search engine and look up the nouns yourself.

  • Fountains of Paradise [fatbrain.com] (also by Clarke, but printed in 1979) centers around the idea of a space elevator.
  • It sure has, why, the US has never interfered with Panama since the canal handoff, no sir, never.

    Except for that Noriega thing, but never again.
  • Hemos posted on this same topic just a few months ago...guess he forgot ;)

    You must be new here. Next you're going to complain about the spelling. :)
    p;
  • At Mars it would work. On Earth, you need taper, because without it you would overwhelm the nuclear forces that hold matter together. There is no material possible that could support an untapered tether at Earth.

  • J. Storrs-Hall's space dock (Score:5)

    by WillWare ( 11935 ) on Tuesday May 08, 2001 @07:01PM (#236732) Homepage Journal
    A few years back, John Storrs-Hall (for many years the moderator of sci.nanotech) was talking about an interesting idea [imm.org] that, like the space elevator, is not very far beyond existing material science. It is also probably more economical. The gist is an airport runway, 300 km long and at an altitude of 100 km, with a built-in linear motor that can accelerate a spacecraft. Over 80 seconds at 10 G, the craft accelerates to 8 km/sec, necessary to maintain a circular orbit. Humans (at least young healthy ones) can survive this acceleration. Current approaches to space launch cost around $10,000 per kilogram. The space dock could allow launches for 91 cents per kilogram, dropping to 42 cents per kilogram as the construction was amortized over the first few decades of use.
  • It's definitely something where the failure modes would need careful study. Build the first one on the moon. (Smaller, cheaper, easier, less useful...) Practice throwing spaceships at targets, catching returns, etc. Then build a pinwheel at earth (high in the stratosphere to space). Useful, but not as expensive, fewer worrisome failure modes, etc. Then build a beanstalk on Mars. Think of it as a scale model for one on earth, and design it accordingly. It will be more expensive than one designed specially for Mars, but as a prototype of the real one at Earth, the cost should all be written off. (I suppose that one could use Venus rather than Mars, but only chemical plants would want to visit Venus).

    Then expand into the web between the worlds. Eventually an elevator to the stars. (I might prefer MacroLife.)

    Caution: Now approaching the (technological) singularity.
  • Why people keep posting that?
    There are only 2 buttons: Lobby and Penthouse!

  • Scientists have no taste in music... (Score:4)

    by mackman ( 19286 ) on Tuesday May 08, 2001 @11:44AM (#236744)
    Dammit, it's supposed to be a stairway to heaven, not a friggin elevator.
  • An estimate has already been made that vs reusable launch vehicles, a space elevator may be able to achieve an advantage of 1000:1 or better in price per kilogram lifted into orbit. Possibly as much as 10K:1 advantage.

    There are plenty of companies who lift kilograms into orbit to make this financially viable if the construction costs can be brought into the range where either a government or a very large aerospace firm can consider constructing one.

    Scientific American had a very good discussion of the subject back in decemberish?
  • Yes, someone will invent a way to make nanotubes cheaply, but then we will have to wait another 20 years for the patent to wear off, hmm I wondering if Clark but patents into his 50 year estimate :)
  • Note: you'd also have to deal with higher orbits for the counter weight too, which would probably extend up atleast a few KM just a note.
  • Ok, I haven't read RGB Mars, Clarke's 3001, or even CYMK Uranus, but I have read the article, and from that limited research, I think you've got it wrong.

    Following the "thought experiment" given in the article, if the space elevator is cut from the earth base at the bottom, nothing would happen. The space base of the elevator is in geostationary orbit. It is then extended both toward the earth and away from it so that the center of gravity remains at the space base. It's extended this way until the shaft reaches the earth base. The earth base is likely to be quite tall to make the shaft as short as possible. The shaft, space base, and counterweight do not rely on the earth base for support. Want to get freaky? Build the elevator so that the shaft doesn't even touch the earth base.

    So what happens when some terrorist blows part of it up or it crumbles because the maintenance guy slacked off? I don't know, let's ask the experts here...What happens to a geostationary satellite that's overly weighted away from the planet? (Assuming the shaft is the section that gets bombed/crumbles.)

    -sk

    ...as an aside, could you build the counterweight so that it serves as a sheild and/or solar array for the space base and shaft sections?

  • I think the Saturnians tried this millions of years ago, and look what happend to them: planet pulled apart into a low density giant; stupid rings make space travel essentially impossible; civilization destroyed, etc. I say we wait for antigravity drive.
  • I don't think a non-tapering stalk is feasable. You want to taper, so that the minimum stress is on each portion. You start with the stress at the end points, and you need 1 unit to handle that stress. A bit further in, and you need 1 unit to handle the end point stress, and 1 unit to handle the stress of the stalk from the end to that point, and that means you need to taper. It's the same reason why we build our tallest buildings tapering, except in that instance the taper is away from the ground instead of to it.
  • The counterweight goes at the opposite end of the beanstalk to the earth.

    O----x----o
    O= earth
    o= counterweight
    x= construction satellite

    The bit you might be missing is that you want to attach the counterweight and the earth at close to the same time, so that the beanstalk goes from being under tension at neither end, to under tension at both ends.

  • 3001 already explained this very thing - in 1997 (Score:5)

    by macpeep ( 36699 ) on Tuesday May 08, 2001 @12:46PM (#236754)
    Arthur C Clarke's Space Odyssey 3001 - printed in 1997 - have space elevators and in the end of the book he explains that they could very well be possible to manufacture using tubular buckminsterfullerene. In the back of the book he says:

    "Meanwhile, the discovery of the third form of carbon, buckminsterfullerene (C60) has made the concept of the Space Elevator much more plausible. In 1990 a group of chemists at Rice University, Houston, produced a tubular form of C60 - which has far greater tensile strength than diamond. The group's leader, Dr. Smalley, even went so far as to claim it was the strongest material that could ever exist - and added that it would make possible the construction of the Space Elevator."
  • "Terrorists attacking beanstalks" is a very common theme. I've seen several short stories directly address the attacks, and indirect references in <u>Friday</u> (Robert Heinlein; Lima stalk) and the David Brin "Startide Rising" universe (where one character's last view of his wife was her losing her grip at the 20 km level... but I think that was just a partial stalk.

    In fact, I believe the first story involving beanstalks involve an attack on one - the companion "science fact" article explained their physics. I'm sure I'll remember the name of the author just after I hit submit - probably either Benford or Sheffeld.
  • I assume the elevator would work the same way that most elevators work, a car that holds passengers that holds cargo which is attached to a long cable which goes over a pully system that has the drive motor and a counterweight on the other end.
    Then you assume wrong. It's based on magnetic levitation.
    --
  • The entire rope assembly needs to be super-strong because it is holding a massive swinging weight that normally would be flung off into space, but isn't because it is attached by (in this case) the carbon nanotube rope.
    Duh, if it's holding up the station, then why is the small end at ground level?

    The cable is hanging from a geostationary satellite. It needs to be super strong to support its own weight. If disconnected from the satellite, it would indeed fall to the earth.

    This is why we need engineers. It seems like nobody else can remember that you can't push a rope.
    --

  • Whitey's space elevator grafiti (Score:4)

    by The Queen ( 56621 ) on Tuesday May 08, 2001 @11:48AM (#236762) Homepage
    So will spray-paint stick to that fancy carbon shit? Cuz we ain't gonna let Whitey forget they roots, nowahmsayn?

    "Smear'd with gumms of glutenous heat, I touch..." - Comus, John Milton

  • Huh? (Score:2)

    by Gorimek ( 61128 )
    But a geostationary orbit means that it will stay over the same spot all the time. Where do these forces come from? Is it all the material in between that would naturally have faster orbits at their height?

    BTW, it's probbaly better to ship up the parts of a sapce ship and assemble it there, rather than lifting the thing up there whole.
  • Agreed. Robinson's RGB Mars rule. One point of interest which I must raise as something of an SF buff, is Charles Sheffield's book The Web Between the Worlds [amazon.com]. It's all (um, almost) about space elevator (or "beanstalk" as he prefers to call them) technology, some of its implications, with lots of technical background. And, you gotta love the part where Mr Sheffield "objects" to Robinson's crashing elevator, because it destroys the city where the elevator was anchored to Mars. The name of the city? Sheffield, of course. ;^)
  • In the Mars trilogy the 'stalk was cut away from its upper anchor and gravity took over ... as it starts to move closer to the planet it starts to spin up (moving to a lower orbit and all that) . with the bottom still attached the result is that it starts to wrap around the planet coming down faster and faster as more and more of it comes in

  • Growing from 4mm in length to 47,000 km (Score:5)

    by GeekLife.com ( 84577 ) on Tuesday May 08, 2001 @01:34PM (#236772) Homepage
    I think I got a spam the other day advertising just that.
    -----

  • Rotational inertia? (Score:3)

    by kevin805 ( 84623 ) on Tuesday May 08, 2001 @03:13PM (#236773) Homepage
    It seems to me like there would be a problem in that you still need to impart that 17k mph orbital speed to whatever you lift up. Since the elevator car just lifts straight up, the acceleration would come out of the inertia of the elevator itself, which would slow it down over time, causing it to smack into the earth at hypersonic speeds, destroying civilization as we know it.

    (before you question the physics, do this: put on your socks, go in the kitchen, spin around with your arms out. bring them in. watch self speed up. extend. watch self slow down)

    Am I missing anything? Do current plans just call for having a rocket on the station to keep it at the right velocity? How would it work with lateral forces on the cable itself?
  • Though understand, that with the technology needed to construct such a thing comes the technology needed to protect against such a disaster, in theory at least. An active space elevator with trillions upon trillions of nanomachines maintaining it could be made to never fall, or to have safety devices such as a failsafe disassembling that takes place, so if it falls all that hits the earth is soft dust.
  • Well, um... great concept, but I think you're ignoring the fact that most of the good humor on Slashdot depends on the context of the discussion. I don't really think most of the +5 funny posts would stand on thier own.
  • In fact, I believe the first story involving beanstalks involve an attack on one - the companion "science fact" article explained their physics. I'm sure I'll remember the name of the author just after I hit submit - probably either Benford or Sheffeld.

    If you were thinking of Charles Sheffield's The Web Between Worlds [baen.com], the story considered the possibilty of a terrorist attack but it didn't actually happen.

    BTW I think A.C. Clarke had a space elevator story out just a few months (weeks?) before Sheffield's novel was released.

  • Hmmm... Would it slosh the oceans? perhaps. The easiest way to figure it is that inert objects in LEO have several times the specific energy of gasoline at the surface. (that is to say, the kinetic energy of a pound of gasoline in orbit exceeds its latent chemical energy by a factor of something like two). The tower's latent energy is greater because most of it is in a higher orbit than LEO -- but not more than a factor of two greater (LEO is halfway to Earth escape, energetically speaking). Gasoline and TNT are comparable.

    Hmmm.... Typical mass: suppose it's a tapered pyramid a hundred meters across at the top and pointy at the bottom, 50,000 km long. Density is (of course) 1. That's 1/4 * 50,000 * 104 tonnes, or about 1011 tonnes. Impact would be equivalent to a few thousand 100-megaton warheads. Well, OK, so that's a lot of energy. Just how much is it?

    Ruining civilization would require sloshing the water pretty high -- a reasonable estimate is, say, enough to lift 1% of the ocean 100m. The Pacific Ocean's mass is something like (1 tonne/m3) * (10km) * (2000km * 5000km), or 1017 tonnes -- an equivalent energy to lifting the 1011 tonnes of the station 105km. So, yup, everything's in the right ballpark.

    There's certainly not enough energy in the elevator to slosh "the entire Pacific and Atlantic across the continents, wiping out our entire civilization in one stroke" -- but there's probably enough to (briefly) flood the great plains with salt water.

  • Excuse me if I am full of shit but I think the problem with your solution is that the added tension of the weight of the cable in your solution would mean that an incredibly efficient system would need to be used for joining, and I do not believe there is a current technology to do this. In summary the tensile strength requirement includes the requirement to carry the weight of the cable itself and once you adjust the weight of the cable you need more strength. If you can do it....choose your equatorial home with the ability to raise the budget!
  • Currently about 90% of the weight of a space shuttle on take-off is fuel. If you want to build the ISS you have to send up huge numbers of missions to get the materials up. If you build a space elevator you do not have to carry the fuel around and can carry larger loads and you can do it for nearly free once you begin bringing things back down. You bring up and assemble a large (say 1000 cubic metres) space craft, send it around the local planets to leave gear, possibly people and collect samples. This craft needs very little propulsion (all things are relative) as it starts off with the speed of the top of the cable so it simply uses that speed to sling it into its next orbit at the same energy. While they are gone you can build your orbital stations for research etc. and mining or colonisation craft. Ideally your first team will drop gear to start the setup of an evelavtor at each stop. Once you have elevators on two bodies it becomes a simple task to move items from a to b be it supplies for colonisers, returning colonisers, samples or mined/manufactured items.

  • Re:Very neat... (Score:4)

    by 13013dobbs ( 113910 ) on Tuesday May 08, 2001 @11:48AM (#236790) Homepage
    The country that builds this thing will have an ENORMOUS advantage over every other nation.

    Besides launching ships, what advantages might such a country have?

    1. Unrestricted view of foreign nude beaches
    2. Looking down the shirt of large brested foreign chicks
    3. Always being able to taunt: "Hey, don't fuck with us, shorty."
    4. Best bungie platform *ever*
    5. Peeing on other countries

  • The major stumbling block with building a space elevator has nothing to do with whether it is theoretically possible to build one, but rather with economics.

    Let us assume, for the purposes of illustration, that all this technology was totally proven and risk-free. We have carbon tube launch vehicles and a potential carbon tube elevator. I will blithely also make up a few more numbers: Counting sustaining costs, an ultra-light ultra-strong space elevator trip costs only 1/4 that of a new ultra-light ultra-strong space vehicle, and it takes a mere 100,000 flights to build the elevator.

    My assumptions are probably wildly optimistic, but the conclusion you reach still shows why it won't be done: You break even when you reach (merely) your 125,000th trip into space.

    Even the most wide eyed space enthusiast would have trouble justifying such demand for space travel.

  • In Nick Park's claymation Wallace and Gromit episode entitled "A Grand Day Out", inventor Wallace creates a rocket to go to the moon, because they need cheese, and as everyone knows, that's what the moon is made of. The dumber people think you are, the more surprised they'll be when you kill them

  • The amount of destruction is going to be strongly dependent on where the break happens and the exact design of the elevator. The one in Red Mars was essentially a worst-case scenario: a comparatively thick, non-tapered elevator (which would be possible on Mars), a thin atmosphere that didn't provide much protection against falling objects, and a break at the ballast asteroid that produced the maximum possible material to fall. In such a case you would have a particularly nasty fall. FWIW, the sabotage in that case was the deliberate separation of the ballast asteroid by destroying its achoring to the cable, rather than an attempt to break the strand itself- not something that would be defended against by anti-breakage measures.

    I also think that your suggestion of designed in breakage system to chop off chunks as it fell would be a truly bad one. Adding in such a system would actually make the elevator more dangerous, as it could cause an undesired cable breakage if it were accidentally or deliberately set off when it shouldn't be. A really dastardly terrorist could crack the control system, blow up the highest mounted cable-breaking charge to precipitate a fall, and then crash the rest of the system. Then you have a falling cable and no way to stop it- the exact thing that you're trying to prevent. IMO Robinson's proposed alternative- built in anti-debris defense stations along the cable- is a more plausible solution to the problem.

  • We don't have a way to get the construction materials into orbit from where to begin building. An expansion of space shipping by several orders of magnitude for an extended period of time would be required to ferry up an elevator's components from the planetary surface.

    This particular problem is probably best solved by getting the materials in space in the first place. You'd capture a near Earth asteroid that had a high carbon content and build the elevator out of materials processed there. The excess, non-carbonaceous materials could be processed into the ballast for the outer end of the cable.

  • Yeah, I am working my way through Green Mars right now... awesome series. Robinson's elevator (in Red Mars, anyway) is a bit different than the one proposed here; the cable is a uniform 10 metres thick (not tapering down to 10 cm) and its central core is a double helix of diamond.

    I think the damage caused by a space elevator falling on Earth would be considerably more than that portrayed in Red Mars. Firstly our gravity well is stronger, secondly, the elevator cable would fall mostly into the ocean, which would cause massive waves, probably wreck a lot of coastal cities.

  • if i did the math right we only have to wait 50 years for the 47000km tubes to be avalable
  • Now the problem is just getting a process that can get us from growing 4 mm in length to 47,000 km

    No, we just need to make 4mm nanotubes and weave them together into a 47,000km cable. Nanotubes are currently in micro-meter lengths; 4 millimeter nanotubes will be cohesive enough to provide a strong weave.

  • Lifting the people isn't terribly difficult: just use a magnetic propulsion system, which has the added benefit of generating electricity when run in reverse as a magnetic braking system when they come back down.

    The hard part will be lifting the cable up in the first place. That's the only problem I haven't heard solved yet.

  • No elevator cable, use magnetics instead. Electromagnets evenly spaced along the way just have to lift the elevator a few inches.
  • this elevator cannot be a direct lift into orbit.

    Why not? Use stronger electromagnets near the base to lift weights.

    It will be preferable to break packages up into smaller chunks, though.

    I can't imagine the kind of liability suite you would face for wiping out a small town.

    The problem isn't the station at the top coming down and wiping out a small town. The problem is the whole blasted cable coming down and wrapping itself around the equator a couple times.

  • Gee, they've solved THAT problem with airplanes and rockets, right? Airtight pressurized cabins? ever heard of those?
  • Once you're up there, you're in geostationary orbit and don't need the elevator for support.

    Even when you're just partway up you could jump off the elevator and enter a lower orbit via a horizontal bump from small rocket engines.

  • A related article posted somewhere a couple days ago detailed that 4mm nanotubes would be enough. Just passing on what the nanotube manufacturer says.

  • .. (Score:2)

    by grue23 ( 158136 )
    Now the problem is just getting a process that can get us from growing 4 mm in length to 47,000 km

    this isn't another one of those penis extension spam email things i keep getting, is it?

  • >The other thing is that this elevator cannot be a direct lift into orbit.

    Um. I don't know what leads you to say this but it IS in fact a direct lift into geosynchronous orbit. That's the whole point. And you can even get to lower energy orbits by jumping off the elevator below geosynchoronous (not too low otherwise you will reenter...).

    It has been studied EXTENSIVELY. The basic concept works fine.

  • Anything we expect to stay in space needs some kind of station-keeping propulsion.

    What you describe, however, is really a matter of the up-station serving as a kinetic energy sink - the energy the elevator car absorbs going up is released again on the way down. There'd be losses to various mechanical inefficiency, but that can be measured and controlled.

  • In an effort to build the biggest weed-whip ever, they are talking about building the cable out of carbon using a process called "HiPCO".

    Do you have any idea how much carbon that would remove from out biosphere!? The surface temperatures of the Earth would drop, growing the ice-caps and lowering the sea level! Catastrophic changes of weather patterns could occur!

    We need an international treaty (which trumps all such petty issues as "national sovereignty" that might get in the way). To prevent this from happening!

    Failing that, we should ramp up a massive effort to extract more carbon from the ground and introduce it into our biosphere by burning fossil fuels. Everybody leave your cars running all day, every day, for the rest of the Century... that might almost be enough to give us a chance. If you drive a small car, or an electric, go out and get the biggest-assed SUV you can afford. Hurry, your planet needs you.

  • You've actually hit upon a lot of the ideas in the book; you should probably try reading it, if it sounds at all interesting, you would probably enjoy it.

    To clarify what happens in the book: The terrorists blow up the central portion of the space elevator, pretty much directly at the midpoint. The top half flies harmlessly into space. The bottom half, now no longer balanced by the top half, flies into the ground.

    And since it's made of these insanely strong carbon tubes, it doesn't crumble or break. It's a giant tube, thousands of kilometers long, falling into the earth. (If this still doesn't sound bad, here's the right thought experiment. Imagine cutting down a tree (and arguably a tree isn't such a bad model for carbon tubules). If you've ever cut down a big tree, you know the amount of force with which it hits the earth. Now imagine that same tree, except now it extends 20Km into the sky.

    For the people who are still nay-sayers: Try computing the potential energy stored within a 5kg mass 10,000 km above the earth. Now convert that to kinetic energy and figure out the ground velocity. (Given, energy will be burnt up or diminished in the atmosphere, but anything that hits will have lotsnlots of joules.) Larry Niven talks about dropping 'crowbars' (with minimal guidance/targeting) from orbit as a weapon in the book Footfall. It's actually amazing how much power such a weapon could hold. (A projective travelling at 3000 m/s has a much kinetic energy equal to its weight in high explosives.) [yarchive.net]

  • Catastropic Space Elevator Disaster (Score:4)

    by IvyMike ( 178408 ) on Tuesday May 08, 2001 @11:45AM (#236834)

    In the Red Mars [amazon.com], Green Mars [amazon.com], Blue Mars [amazon.com] trilogy by Kim Stanley Robinson [sfsite.com], he describes a space elevator on Mars which is destroyed by terrorists. The effects of the billions of tons of carbon tubules smashing into Mars as the space elevator falls (wrapping itself around Mars in the process) is on a par with the destruction caused by asteroid/comet impact.

    The books are quite good, with a lot of cool ideas, and are probably one of the most realistic treatments of how we could terraform Mars. But you'll have to work your way through some lengthy discussions about the geology of the red planet.

  • Sure, the thing weighs gigatons, but as it falls it is subject to the coriolis force. so the thing would wrap itself around the earth. it doesn't just plop down to one spot, and it takes a while to do so (more than 45 minutes).

    sure, everyone around the equator is kinda disappointed, but what a show!

    why not embed small nuclear (or since we are daydreaming, antimatter) charges to blow it up into tiny pieces if it starts to fall.

    and what about the jackass who pushes all the buttons just before he gets off?

    /m

  • I had it in my head that since gravity acts differently at different points on the cable, it could not maintain a stable orbit, but I guess that's not true. I think the thing I missed is that the added force of gravity on the cable that's being lowered is counterbalanced by the so-called centrifugal force acting on the counterweight being raised.

    I also thought that something akin to the Coriolis force may come into play (I know the Coriolis force will have nothing to do with the whole space elevator, but I thought something similar might cause the cable to start bending, like the arm of a galaxy). But I guess that's not true, either.

    (So I suppose I deserved to be moderated down... oh, well.)

    ...you want to attach the counterweight and the earth at close to the same time, so that the beanstalk goes from being under tension at neither end, to under tension at both ends.

    Actually, you should be able to safely attach the ground end first, because it will just be hanging in geostationary orbit, as it were. I'm not sure you even need a counterweight to pull the whole thing taut - just enough to overcome the force of gravity on the cable.

    Probably, the best way to attach an added counterweight (if you need one) would be to bring it to the original geostationary satellite and then let it "fall up" to the end of the cable.

    Another option might be to use the construction satellite itself as the counterweight - so as the cable gets lowered to the earth, the satellite just moves itself to a higher altitude.

    --

  • Re:Very neat... (Score:3)

    by Kazymyr ( 190114 ) on Tuesday May 08, 2001 @12:06PM (#236851) Journal
    I find it interesting everyone quotes the [red, blue, green] Mars, but no one remembers who first had the idea: A.C.Clarke - "Fountains of Paradise". It's a very good book, it even has the right solution for preventing the catastrophic collapse. :)
  • Another book featuring a space elevator is "Jumping Off the Planet" [barnesandnoble.com], by David Gerrold. Lots of great stuff about the economy, social impacts, etc of the "Beanstalk".
  • Also, the chances of it falling at a safe re-entry angle are fairly remote. Most likely it would just burn up in our atmosphere. Remember, there is a lot of *friction* when something falls to the earth from space.

    Well, your fingers weave quick minarets; Speak in secret alphabets;
  • So will spray-paint stick to that fancy carbon shit? Cuz we ain't gonna let Whitey forget they roots, nowahmsayn?

    nocanyoutranslatetoenglish?
  • Like anything else, once you can build one of these things, building a dozen would just be a matter of scale. The idea of "up" would simply become another commodity.

    Can you imagine a world where near-earth-orbit travel becomes almost banal?

    The least popular Jackson brother may have wasted that 20 million after all. [ridiculopathy.com]

  • Dr. Forward has a VERY interesting whitepaper out that has taken the "beanstalk" idea to a much more usable conclusion. Rotating tethers. You don't need one great big bloody stalk. You just need a couple "rotavators" that toss everything to each other.

    The one in the lowest orbit is just long enough to dip down into the atmosphere, where you "dock" with it using some type of plane, etc. THen the end keeps swinging up and tosses the cargo into orbit like a giant sling (a kilometers long sling). You also put one in orbit around the Moon. Easy travel back and forth. Look it up.

  • Also on Space Science (Score:3)

    by bziman ( 223162 ) on Tuesday May 08, 2001 @02:54PM (#236874) Homepage Journal
    Yes, this was published in Space Science [spacescience.com] and featured [slashdot.org] on Slashdot, back in September. They were using carbon nanofibers back then, too.

    The two articles have the same artist rendition at the top, and drops the same numbers, but the September article has more cool pictures.

    --brian

  • Deep Background on Carbon Nanotubes (Score:3)

    by hillct ( 230132 ) on Tuesday May 08, 2001 @11:40AM (#236881) Homepage Journal
    This is the most comprehensive site I've found for deep bakground on Carbon Nanotubes: http://www.pa.msu.edu/cmp/csc/nanotube.html [msu.edu]

    --CTH

    --

  • Interference with other equatorial orbits (Score:3)

    by dmatos ( 232892 ) on Tuesday May 08, 2001 @05:18PM (#236882)
    Well, I got halfway through the other comments, and haven't seen a thread bringing up this point yet, so...

    Has anyone given any thought to how a stationary permanent space elevator will restrict the number of orbits available? No more equatorial orbits at all, at any height (except geosynch), and any orbits that cross the equator (say, the polar orbits that many spy satellites are on) would have to be VERY carefully calculated so that they would be in a resonance pattern with the elevator, and miss it every time. Well, that covers every orbit possible, doesn't it.

    Other people's thoughts on this?

    PS - credit to Larry Niven Rainbow Mars for bringing up that objection.
  • do you really know how many tons of CO2 you would need? also, the 2 O atoms would be split off. Their isn't enough C in the air to do that. Their is enough captured in the ground to do it, however. We may need to mine the moon to do it, if we don't want to do mass conversion of Coal to Carbon.


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  • I think you're a little confused... if it collapsed it could possibly strike something on the earth, or cause damage to spaceborne objects in its path, however there's nothing even close to an engineering reality at the moment that could tear the earth in two.

    OTOH you should read the end of Red Mars and imagine what the falling elevator would do when it hits an ocean. Not a pretty thought... more than enough energy there to slosh the entire Pacific and Atlantic across the continents, wiping out our entire civilization in one stroke. Makes the K-T impactor look like a popcorn kernel by comparison.

  • In one of the Gateway books by Fredrik Pohl, they actually have a space elevator that is blown up by terrorists (the ground station) and the loop ends up feeding into a huge man-made lake and vaporizing it

    No, the device which is destroyed in Heechee Rendezvous is a Lufstrom loop, a way of launching orbital vehicles which stores massive amounts of kinetic energy in a loop like a conveyor belt which travels at orbital velocity. Relatively small amounts of this kinetic energy are extracted by each launch (riding the loop to orbital velocity by a linear induction setup) and are restored by low-impulse continuous power sources (presumably nuclear).

    The amount of energy released in the collapse of a space elevator would vaporize a lake the length of the Equator.

  • If the elevator is severed from its counterweight it will accelerate as it falls. Take a bullwhip, hold it by the handle, and spin in a circle so that the tip is "orbiting" you. Suddenly stop spinning. Let us know how tightly the whip wraps around you (analogy of impact of the cable) and whether the tip hurts when it hits you.

  • Re:Very neat... (Score:4)

    by localroger ( 258128 ) on Tuesday May 08, 2001 @01:24PM (#236896) Homepage
    If the rope were cut at the bottom, the whole assembly would be shot into space and never seen again.

    Wrong. Cut at the bottom, the whole assembly would enter Earth orbit. The question of whether parts of it would ever hit the Earth would depend on the solutions to a hell of a lot of differential equations.

    If it were cut at the top, the weight would fly out, and the rope, although no longer able to lift objects, would continue to stay aloft because it also has outward momentum.

    Wrong. Cut at the top, the rope would not have enough outward momentum to hold its own against gravity. That's why there is a counterweight.

    The only potential problem is if it were cut in the middle. Even in this case, only half of the rope would come back to earth.

    Very astute. Except...

    the only effect would be a few miles of super-strong rope falling down on whatever remote location they build this thing at.

    True if by "few" you mean about 10,000. Hint: There is no equatorial location on Earth that is not within 10,000 miles of an ocean.

    Re-read (Re? Oh well, make that just "read") the finale of Red Mars and get back to us.

  • Oh, cool! (Score:3)

    by Shoten ( 260439 ) on Tuesday May 08, 2001 @11:36AM (#236898)
    Now the problem is just getting a process that can get us from growing 4 mm in length to 47,000 km

    Oh, cool! We're almost there. So, when does it go up...next week, or do we have to wait until after the summer? By the way, just how much pure carbon do you think they'll need, anyhow? I might be able to spare a few grams of it from off the valves in my car...

  • to would control it.

    Though I find it very had to believe that the powers that be would allow some country outside the G8 to control a space elevator. Friggin Ron Reagan has a shitfit that Nicarauga has a democratically elected government that did not cow-tow to the Capitalistic line, what would his spiritual descendants do if say Libya built a space elevator?
  • It seems to me that an enzyme set would be ideally suited to building N-length nanotubes. Additionally, you could glue them together with that indestructable stuff barnacles use to cling to stuff. It's got huge compression strengths, while nanotubes have awesome tensional strength. Bio-composites anyone?

  • Uh, no (Score:4)

    by cryptochrome ( 303529 ) on Tuesday May 08, 2001 @12:24PM (#236912) Journal
    Actually, nanotubes are NOT cohesive enough. In fact in nanotube composite materials, the tubes are so smooth and so non interactive that they slip around each other and any binding matrix. So I'm afraid we'll be needing that nanotube polymerase or polymerizing reaction or nanomachine constructor. Potentially some slight modifications may need to be made - if it's twice as strong as it needs to be, maybe we could compromise that strength a little by cross-linking them. If they were somewhat longer, weaving might also be an option. Perhaps carbon nanofibers (VGCF) would be easier to produce. How would they perform?

    But there are other problems too. Nanotubes will degrade under certain high-energy conditions. Therefore they might not work so well in space. And finally, one of the forms of nanotubes is conducting. If you have an electrical conductor (the elevator wire) sweeping through a magnetic field (the earth's) you'll generate an electrical current in the conductor (high voltage, potentially useful) as well as mechanical force perpendicular to the magnetic field and the conductor (BIG problem). It wouldn't take long for that to be dragged down to earth. I'm not sure how the semiconductor form would hold up. Carbon nanofibers are very conductive too.

    cryptochrome
  • Some guy has a whole herd of breeding goats that have spider silk generators in their DNA, they extract the chemicals from goat milk, and presto! He's gearing up for commercial production.

    That's way stronger than Kevlar, isn't it?

  • I wonder if you will have to give Gene Wilder a piece of chocolate before you can ride it.

    --------------------------------

  • The only thing I would like to point out (Score:3)

    by Sycraft-fu ( 314770 ) on Tuesday May 08, 2001 @05:47PM (#236926)
    Is that all of you seem to be bassing your asserations about this crash off of a work of FICTION (Red Mars). Now I know that often SF authors do research and their secnarios are accurate, but this may not be the case. I'd consult a physics professor before making any firm judgement in this matter.
  • I seem to recall a story that went something like this:

    On a discussion of ways to purify U-235 for making an atomic bomb (this was in the 1940's), a scientist was talking about atomic-mass spectrometers. He said, "A unit can purify uranium-235 more than sufficiently to make a bomb, but it would take a million years to purify enough for just one bomb."

    Someone from the audience said, "So you build a million units, then it only takes one year."

    We currently make cable in machines that go much more than one mile per hour. The rest is just assembly and orbital mechanics (you have to put the stuff in orbit and build it downward, or rather outward both ways from geosynchronous orbit).
    --
    spam spam spam spam spam spam
    No one expects the Spammish Repetition!

  • Stick a metal pole parrel to the floor on a ball. Spin the ball, doesn't the pole fly off. Now stick a pole ontop of the ball, perpendicular to the floor and spin the ball. Wouldn't a polar space elevator require a lot less anchoring?
  • "The financial investment in such a project would dwarf all other civil engineering to date." You obviosly haven't heard of the big dig....
  • Far more than an approximation, the center of mass is a fundamental principle in physics as basic as gravity itself. Take an object...any object into microgravity, and spin it any way you like. Make it spin about an axis, or tumble end-over-end, and you'll find that whatever you do it's going to spin about a single point of its structure. This is the center of mass. It's really the same thing as the center of gravity for an airplane, but they've applied a different name since by definition we're dealing with a zero-G environment. NORgasmic
  • how much would you tip the bell hop?

    being an elevator operator is usually a good job... but it has its ups and downs.

  • Oh Man..... (Score:4)

    by CullyUCSC ( 450467 ) on Tuesday May 08, 2001 @12:22PM (#236956)
    Can you imagine listening to elevator music for 47,000 kilometers???
  • NIAC (NASA Institute for Advanced Concepts) at http://www.niac.usra.edu has a full 200 page paper about this including the physics and math. I know, I read the whole damn thing.. If anyone has questions about it, this is the site to go to. .....Math, Science, Art.....

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