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  • Elevator Music to the Stars

    Posted by James R. Rummel on November 2nd, 2008 (All posts by )

    I’m a kinda-sorta advocate of space exploration because I realize that the technology goes far beyond the intended purpose. Figure out a way to send a robot probe to a distant planet and you also have come up with hundreds of new applications that can be used right here on the Big Blue Marble. It is in this that people dedicated to space travel and myself agree.

    True blue space enthusiasts lose me when they try to make the case for a permanent human presence in space. It would cost far too much with the technology we have available, and they have never been able to come up with any benefit to justify the effort that makes any sense to me. A lot of them insist that it is something we have to do, though.

    One of our fellow Boyz, Steven den Beste of Chizumatic fame, gave me some insight into their motivation.

    Chizumatic is where Steven discusses anime, and he recently posted some thoughts on a series where teenage girls are recruited for a space program. It is there that Steven points out that, for some people, space travel is a religion. That is why they have never been able to articulate any justification for the expense of manned space travel that I could appreciate. I was talking to people who have their temples in the sky.

    The cost of flinging mass into orbit and beyond is a non-trivial problem that brings even the space enthusiasts up short. They say we can get around that by building a space elevator, which is a tower more than 60,000 miles high. Last time I checked, that is about two and a half times the circumference of the Earth.

    This actually is something that interests me, not because I think it is even remotely possible, but because I am intrigued by the Earthly applications if some of the basic engineering puzzles are solved. The very first problem before anyone can even think of building this stairway to heaven is coming up with a material that is strong and light enough to hold together under the stresses that such a structure would constantly experience.

    What could we do with such material? I have visions of bullet proof T-shirts dancing in my head. Main battle tanks that weigh as much as the family car, even though they can withstand point-blank armor piercing cannon fire. And what about the family car? Build the body of your common SUV out of such material and it would withstand even the most extreme road accident without any ill effects. Body shops would go bankrupt.

    But such an adamantine substance is clearly impossible, Wolverine’s skeleton notwithstanding. It is so ridiculous that I am rather reluctant to even bring it up, particularly since the people who talk about space elevators pretty much assume that we are only a few years away from the development of such a substance. One of us is way off base, but which?

    So I wrote an Email to Steven, asking him about this magical material. I was hoping that he could give me a baseline of local applications to work with. If we see, I dunno, car tires that are rated for 2 million miles before they begin to wear out, then we would know that we finally had something strong enough to build the beanstalk.

    He was kind enough to reply, for which I am very grateful. Unfortunately, he found other issues to be more interesting to discuss then how something sturdy enough for a space elevator would change our lives down here at the bottom of the gravity well.

    So I suppose I’ll just have to hold out for bullet proof underwear. If Fruit-of-the-Loom comes out with Level II-A protection on their tighty-whiteys, then the space elevator advocates can talk. Until then they are just wasting my time.

     

    28 Responses to “Elevator Music to the Stars”

    1. cottus Says:

      May I humbly suggest that space travel is all about survival, and survival is pretty much, theologically and philosophically, why we are here in the first place. I believe it is firmly established that in umpty ump years the sun will bloat into a red giant, its surface reaching out beyond the orbit of earth and then exploding as it goes supernova…or some such. Sooner or later attempts to save ‘Mother Earth’ are doomed. Hunkering down in ‘Bunker Earth’ is doomed. I believe in getting a head start on the problem. Can’t hurt. As you suggest, technological spinoffs are nice. Maybe a better use of scarce resources, because when successful, new resources become available.

    2. Obloodyhell Says:

      > It would cost far too much with the technology we have available, and they have never been able to come up with any benefit to justify the effort that makes any sense to me. A lot of them insist that it is something we have to do, though.

      LOL. Do you not see that the same reasoning you used a paragraph before applies? There are SO many things we don’t grasp about the conditions of microgravity, both its effects on humans, its utility for the performance of various engineering and processing tasks, and all manner of additional interesting possibilities which we not only have no clue about, but can’t begin to even ask a question about it.

      Foamed metals, alone, would more than amply pay for the price of keeping humans in space. Imagine a beam of steel with the same streength as a solid beam, but with a fraction of the weight, because it’s basically like steel styrofoam? You can’t do that on earth because gravity causes the air to float “up” in the liquid steel before it cools. And that deals with a whole HOST of possible techniques which cannot be investigated without a constant presence of Man In Space — non-wetting materials (think oil and water) can’t be formed, and that is highly relevant to materials creation. Gallium Arsenide is a known room-temperature superconductor, but it’s a laboratory curiosity because Gallium and Arsenic are non-wetting. The earth’s gravity means that they separate and drift apart as a result. If they were allowed to cool without that happening?

      Flames behave EXCEEDINGLY differently in microgravity. We have no idea what might be possible with this.

      Virtually free aluminum, boosted from the moon’s surface using a linear accellerator powered by the sun’s energy, and processed out in space, with no pollution, strip mining, or whatever, from earth could also pay for it, and all the energy used (aluminum is an expensive material to refine) comes from space, for free, via the sun. You don’t even need solar cells, just use mylar mirrors to focus the sun’s heat.

      Do you have any idea how much iron is in a typical nickel-iron asteroid, of which there are literally thousands? Somewhat more than the entire world’s production of steel. That’s *one* asteroid.

      A large chunk of the expense of putting men into space comes from the ridiculous expense of a transport system created and run by a government agency with little reason to try and cut costs, and with a military agenda having little to do with the desire to put and keep Man in space. Producing a people-only launch vehicle while developing a laser-launch mechanism for needed initial materials (the long run idea is to get as much as possible from out there, typically the moon)

      Health and leisure. Who knows what might be done if one could temporarily remove the burden of gravity from people who are ill? What sort of surgeries might become practical or even possible without that problem?

      Games? What sort of games can people play in zero G? The NFL is worth billions of dollars. Not possible in space? That seems unlikely. How much would people pay to be able to fly, which is not only practicable in space, but on the moon as well, with its one-sixth gravity. The tourism possibilities are enormous.

      It’s a bit dated, but I strongly recommend you read G. Harry Stine’s
      The Third Industrial Revolution (1979)

      Also by Stine:
      The Space Enterprise
      Halfway to Anywhere: Achieving America’s Destiny in Space
      Space Power

      And
      Doomsday Has Been Cancelled by J. Peter Vajk

      Stine wrote extensively on the future possibilities of space. Vajk’s book is partly about solar power satellites, but also touches strongly against the whole Club of Rome sort of garbage that was central to a lot of thinking in the mid-70s, and is an undercurrent of the anti-growth attitudes today.

    3. James R. Rummel Says:

      “Sooner or later attempts to save ‘Mother Earth’ are doomed. Hunkering down in ‘Bunker Earth’ is doomed.”

      So far, this has been the fallback position of most of the space enthusiasts I have engaged in discussion. Usually they want to talk about another dinosaur killing asteroid striking the Earth, claiming that we need to set up colonies on other planets so at least our species won’t be completely wiped out. But, they say, we gotta leave in order to stay alive.

      My main objection to manned space flight now is that it just plain costs too much to get people and the required life support mass into space using chemical rockets. The idea of a space elevator, surreal though it seems, is an attempt to cut these costs. Space enthusiasts try to sidestep these objections by saying that any amount is justified when simple survival is at stake.

      The problem is with either the time scale or the odds.

      The chances of a meteor screaming down from the sky and hitting me on the noggin are so remote that I don’t even bother to think about it in my daily routine, yet the odds of that happening are at least thousands of times better than a dinosaur killer vectoring in. By any realistic assessment, the threat just doesn’t justify the effort to counter it.

      So far as the Sun going red giant, we have about 5 billion years before that happens. Simple evolution says that nothing even resembling humanity will be around by then, so it really isn’t our problem.

      James

    4. James R. Rummel Says:

      “Foamed metals, alone, would more than amply pay for the price of keeping humans in space.”

      Call me when boosting all that mass, the factory and raw materials, into orbit becomes financially feasible. Strong steel won’t be worth much if it costs several times more than a similar weight of platinum to produce. I don’t see anyone building a skyscraper out of platinum beams down here, so…

      “Virtually free aluminum, boosted from the moon’s surface using a linear accellerator…”

      Again, call me when all your idea become economically viable. As it is we don’t have the capacity to even supply a lunar colony of more than a few people, let alone the fair sized town it would take to build your accelerator and mine the metals to send back to Earth.

      Besides, I wasn’t aware that aluminum was so expensive down here on Earth that we were desperate to find alternative sources. I know of some dumpsters where you can find all the cans you want for recycling, so a trip to the Moon is hardly necessary.

      “It’s a bit dated, but I strongly recommend you read…”

      Most space enthusiasts are surprised to learn that I’m already pretty well read when it comes to this subject. While I would never claim to be an engineer, or even as technically proficient as a professional machinist, I have been casually reading up on the subject since the early 1970’s. First it was science fiction when I was a child, and then on to more technical fare.

      The problem isn’t that I don’t know the details behind the supposed benefits, but that I’m well versed in the difficulties and the costs. Having ideas someone thinks are neato won’t make those difficulties go away, stroking someone’s sense of wonder won’t lower the cost. Until the difficulties and costs come down, it won’t happen.

      James

    5. Obloodyhell Says:

      OK, now, regarding the Space Elevator concept. Actually, the material issue itself isn’t that hard to imagine or deal with. It’s either sapphire whisker or some similar material, or carbon nanotubes. The tensile strength (that’s the term you’re interested in) is phenomenal. It makes spider silk look like spaghetti.

      The current problem with it is production of it in industrial quantities and forms. Right now, in the labs, partly due to Earth’s gravity, you can make sapphire whiskers about 3/4ths of an inch long before they snap off due to lateral stresses at the ends. There are similar limits on carbon nanotubes, but presumably for different reasons. I’m less familiar with that technology.

      Making strands of either substance which are miles long isn’t even vaguely practical on Earth, so far. In microgravity, though…. who knows?

      One thing to grasp about space elevators, which I suspect you don’t, is that they are not towers, which are a “compression structure”. Though a common referent for them is “Orbital Towers”, the actual engineering mechanics are much more that of a suspension bridge, with its attendant problems. Mechanically, it’s a wire under tension. You have to worry more about resonance problems than most people grasp — as Steven notes in his piece, the Tacoma Narrows bridge problem.

      Steven does see a problem where I’d argue it likely doesn’t exist — the presumed function of this device does not involve putting the energy needed into the system each lift to boost the presumed “cage” into orbit. The actual construction of a space elevator is, again, a wire under tension — gravity and centripetal force are the operating forces. The central point is 24k miles up, the so-called Geostationary orbit point, where fixed-point communications satellites reside. At least half the Space Elevator lies BEYOND that point, and the net effect of the forces are that anything attached to the elevator cable which is beyond that geostationary point is getting pushed OUTWARDS. Likely, however this thing is devised, it will use magnetic forces to raise and lower a cage.

      So the obvious choice is that you’re going to always operate a PAIR of devices, linked together — one coming in or going out, and the other going out or coming in, depending on whether or not you are raising or lowering the cage. One will be giving up potential energy, while the other is taking it up. The main energy which needs to be added to the system is losses to friction and conversion inefficiencies. Nontrivial, but not insoluble, either. If you look at the actual operating mechanism of any earth-bound elevators, you’ll see the same principle applied in the form of the counterweights, something which is a part of all elevator systems, but you’ll never, ever see them excepting in movies like Speed or Die Hard, where some action takes place in the actual shaft areas. In the Space Elevator, the counterweight is on the other side of the stationary orbit point at the center. Since there is substantial utility of being at the opposite, non-earth end of the device, it is probable that that end will be almost as heavily used as the earthly end.

      I don’t think earthquakes are a likely issue, since this thing is going to require a foundation which sinks several miles down into the bedrock layer. Most suggestions also are that it will take advantage of an equatorial mountain (Kilimanjaro is an common example) to gain itself a few thousand feet and also to make unpredictable earth-based winds a non-issue by rising almost completely above them before you even get to “structure”.

      Both of you ignore the real concern with Space Elevators, which is that they are obvious targets for terrorism. Sneak a nuclear weapon onto one of the earth-to-orbit cages and set it off anywhere above the landing area and you have a major problem. The upper section isn’t the problem (it will simply shift upwards until the new center of gravity balances with the orbital location), it’s the now-unsupported lower section which is the issue. As Steven notes, the Coriolus forces applying would have it wrapping around the earth, and it would hardly be pretty when that whip-snap end struck the earth with all that momentup built up, no matter how long it was.

      Mind you, I don’t anticipate seeing one in the lifetime of anyone currently alive on the earth — the engineering issues, which I appear to have minimized, are still anything but simple. And the chief reasons for creating one are actually such that they may be overtaken by technology. While a space elevator is the most efficient means for getting large numbers of people or material off-earth given the issues of gravity, if anyone comes up with effective anti-gravity, its reason for existing becomes close to nil. Since the development of a space elevator would almost certainly be a generation project, one has a major problem with the risks inherent of finding anywhere on earth — especially at the equator — being politically and economically stable for the length of time required to actually create this thing and recover the expenditures plus reasonable profit.

      So all-around, they are much like a STL Generations ship. Both are probably doable but also probably not cost-effective. Too much risk of some radical new tech development mooting all the effort needed to create one.

      I would suggest, though, that you and Steven both ought to read some of the SF which deals with the notions, since they discuss in a fair way the concepts involved and some of the socio-political and technical matters which are central to them. It’s clear from both your commentaries that you haven’t read much about the topic.

      The most obvious such book is Arthur C. Clarke’s now-venerable The Fountains of Paradise.

      David Gerrold also has a young-adult trilogy (akin to one of Heinlein’s juveniles — very adult-readable)
      The Dingilliad
      A notable portion of the story takes place on a space elevator as the family leaves the Earth for another planet.

      Kim Stanley Robinson wrote a trilogy
      The Mars Trilogy
      Which is about terraforming mars, and which has a space elevator as a part of the first book.

      Additionally, there is substantial use of the substance necessary for construction of a Space Elevator, referred to as “molecular monofilament”, in many of the Known Space stories of Larry Niven. He points out that this stuff, while incredibly useful, is also incredibly dangerous — since it would be almost invisible to the eye but able to cut through steel like a hot wire cutting through butter. Think about the classic trick of drawing a rope across a roadway your enemy is chasing you down and you start to see some… interesting uses. Another weaponary use for it is a sort of lead ball on one end, connected to a nunchuk like handle on the other, with a 3-4 foot length of the stuff connecting them. Very nasty. Just don’t make a mistake with it… D’OH!.

    6. James R. Rummel Says:

      “Actually, the material issue itself isn’t that hard to imagine or deal with. It’s either sapphire whisker or some similar material, or carbon nanotubes.”

      Steven mentions nanotubes in passing in his own post.

      “Now you hear them muttering about “carbon fibers” but that’s just religious catechism.”

      I have to agree with Steven on this. I’m talking about manufacturing enough material to make T-shirts, and you want to discuss spinning single strands tens of thousands of miles long? Your fantasy life is screwing up your perception of reality, my friend.

      I’ll say it one more time.

      The very first problem that has to be solved before anyone can even start discussing a space elevator is creating a material strong enough to build it. This material would find thousands of uses here on Earth decades before any of the other non-trivial problems will be solved. It is a waste of everyone’s time to go on about a space elevator until we actually see these applications in place.

      I stopped reading your comment after the third paragraph because, be honest here, what is the point? Even you admit the material doesn’t exist, so going any further would be the waste of time that I mentioned above.

      James

    7. Obloodyhell Says:

      > Call me when boosting all that mass, the factory and raw materials, into orbit becomes financially feasible.

      NO. You’re looking at it all wrong. You need to put people there, and probably enough to put a functioning mass driver on the moon. That’s about it. Both can be small enough to get the first self-sustaining part going to the point where it will make a return on investment. Then ramp up as we get more practice and have new ideas.

      You damned sure don’t put raw materials up there — you get them from either the moon or from asteroids, the moon is very plentiful in aluminum oxide. So at the least, we can presume getting both oxygen (for breathing) and aluminum (for smelting) there. The metals in an asteroid are actually fairly pure, limited requirements there. And for reaction mass, you can use the actual asteroid itself — throw part of it off to change the course, set it into a long, slow curve to lunar orbit or even into the trojan point location. This can be done with 60s-era ion propulsion systems. (The only reason I mention asteroids at all at this point is that we’re not sure how plentiful iron is on the moon… limited existing samples aren’t exactly a statistical universe)

      Start with relatively small ones (the size of small buildings) to make sure we really understand the mechanics of the process first, even though it’s apparently pretty straightforward.

      The whole costs of putting up some pilot plants are in the hundreds of billions of dollars, with possible RIOs in the multitrillion dollar range. That’s a lot of money but easily within the range of some of the bigger projects done with consortiums. A lot of the aspects of it could easily be justified with “X-prizes” for achieving specific feats and licensing the resultant technologies for wide use. This is a libertarian form of what the Apollo program accomplished, without the need to get the government involved unless there is a successful activity.

      > let alone the fair sized town it would take to build your accelerator and mine the metals to send back to Earth.

      ??Where the HELL do you get a “fair sized TOWN” required? This isn’t the bloody 1930s building the Hoover Dam…

      You’re talking maybe a few dozen people to assemble a broken-down-for shipping pre-constructed device that’s the size of a locomotive and a few dozen miles of train track, along with a few hundred solar panels. A set of rovers, later capable of remote operation, to do the collection — the stuff is nothing more than the surface DUST. That’s almost pure aluminum oxide. Use mirrors to melt the stuff into a box of slag. The biggest question is how to effectively tie it to the mass driver for launch. After creation, probably a half-dozen people or less for a few months at a time, just because we haven’t yet gotten anything better than the Mark-1 eyeball and the Mark-1 hand tied to the Mark-1 brain to actually fix random problems and investigate random solutions. We’re talking mostly about the basic problems of keeping people alive at an Antartic base for the winter.

      And you don’t send them directly to earth, you put them in lunar orbit and do things there. Probably foamed aluminum would be the best first product, just because it’s an obviously useful substance which you CAN’T make on earth. Foamed steel if we can find substantial iron ores while prospecting the surface (again, largely by remotes), but don’t count on that. Working out the kinks is another reason to have people there, because any first impressions as to what will work aren’t going to be 100% right.

      A lot of it can be done with a small plant at the start, with a lot of teleopertated and telesupervised activities, but with some good people there to deal with the unexpected or to make stuff on the fly which can resolve unforeseen problems.

      My God, you look at this as an unsurmountable obstacle rather than a set of surmountable challenges. You’re a prime example of how far this country is falling in terms of its will to do. I’m not saying it’s EASY. I’m saying it’s DAMNED OBVIOUSLY got lots of money to be made from it, and it’s mainly a matter of deciding to do it. All of the problems are engineering, and none of them are beyond the bounds of current technology.

      A laser-launch system for replenishables and a working reusable man-rated craft, like Space Ship Two or its successor are alone worth the development costs, and once you have those two the rest of it falls into place at a fraction of the numbers dancing around in your head, since you’re trying to do it the brute-force way, involving hundreds or thousands at the very beginning. That’s not the way you develop undeveloped resources in unexplored areas, and you ought to grasp enough about the manner in which this country was developed to see that. It’s a slow, steady progression to bootstrap such an arrangement.

      As Robert Heinlein put it, if you’re in orbit, you’re halfway to anywhere. Getting out of the Earth’s gravity well is the biggest trick, and the only reason it’s so expensive still is that it’s been the province of the Federal governments to this point. The amount of energy involved isn’t that high in terms of expense. It’s just that we are not real good at applying that energy within the bounds of the problem just yet.

      It’s a good thing no one like you was around to tell Jefferson about the sheer futility and uselessness of sending out Lewis and Clarke. I’m sure you would have been a real boost to the pioneer families, too…

      :^P

      If you want to cede space to the Chinese, well, go ahead, I can’t stop you.

      But I cite to you that you’re a fool to do so, and I, for one, have no intention of joining you.

      It’s the Manifest Destiny before us.

      We are meant to take on challenges. It’s in our very natures.

      My own life has been spent chronicling the rise and fall of human systems, and I am convinced that we are terribly vulnerable…. We should be reluctant to turn back upon the frontier of this epoch. Space is indifferent to what we do; it has no feeling, no design, no interest in whether or not we grapple with it. But we cannot be indifferent to space, because the grand, slow march of intelligence has brought us, in our generation, to a point from which we can explore and understand and utilize it. To turn back now would be to deny our history, our capabilities.
      – James A. Michener -

    8. Obloodyhell Says:

      > I stopped reading your comment after the third paragraph because, be honest here, what is the point? Even you admit the material doesn’t exist, so going any further would be the waste of time that I mentioned above.

      That’s ok, if you want to mark yourself as a close-minded idiot who has already decided the answer.

      Someone else might listen to your arrogant diatribe (and that IS what your blather is, when you can’t be bothered to actually read a carefully argued, non-emotional response, which openly acks that the elevator itself ISN’T going to happen anytime soon — my argument is far more with your claim that MAN IN SPACE is a waste of time and money)

      ================================================================
      More critically, why did you even waste time creating this topic? You clearly have no interest in the question, or the answers.
      ================================================================

      I’ll remember to ignore your mindless blather in the future. You’re quite atypical of most of the thread authors here, who are actually interested in something other than hearing themselves talk.

    9. Robert Schwartz Says:

      Things can be strong on one axis but not another. Concrete is strong in compression, but not in tension or shear. Space elevator cable needs to be strong in tension, but need not be strong in compression. It might not make very good undies. Me, I am sticking with cotton for my smalls.

    10. Obloodyhell Says:

      > Besides, I wasn’t aware that aluminum was so expensive down here on Earth that we were desperate to find alternative sources.

      And here you show your ignorance and close-mindedness. I specifically said FOAMED and took the time to explain WHY you can’t do that on earth.

      …but you already knew all the answers, right? You weren’t actually looking for anything that didn’t reaffirm your notion that Main In Space can’t be justified, solely on the basis of the fact that NASA can’t do it for less than a few thousand dollars a pound. What the hell is a Keynesian doing in this place?

    11. James R. Rummel Says:

      “You need to put people there, and probably enough to put a functioning mass driver on the moon.”

      So wake me up when we have the capability to actually put a mass driver on the Moon. A mass driver powerful enough that it can fling cargo into Earth orbit. Not to mention the technology to mine the Moon, and the technology to keep the people on the Moon alive so they can be doing all this mining and flinging.

      “More critically, why did you even waste time creating this topic? You clearly have no interest in the question, or the answers.”

      But that is just it. There are no answers to these problems that will actually work in the real world! Anyone who says otherwise is crazy.

      My purpose in discussing this topic was to bring attention to Steven’s remarks over on his own blog. It is also a cautionary note since I think it is counter productive when space enthusiasts start talking about projects that are obviously impossible. They are shooting themselves in the foot because the general public, the people they need to support further research and development, can tell when someone is trying to sell them a bill of goods.

      “Besides, I wasn’t aware that aluminum was so expensive down here on Earth that we were desperate to find alternative sources”-And here you show your ignorance and close-mindedness. I specifically said FOAMED and took the time to explain WHY you can’t do that on earth.

      No, you are lying. You never mentioned foamed aluminum. Instead you said…..

      Foamed metals, alone, would more than amply pay for the price of keeping humans in space. Imagine a beam of steel with the same streength as a solid beam, but with a fraction of the weight, because it’s basically like steel styrofoam?

      The only time you specifically mentioned aluminum you said…

      Virtually free aluminum, boosted from the moon’s surface using a linear accellerator powered by the sun’s energy, and processed out in space, with no pollution, strip mining, or whatever, from earth could also pay for it, and all the energy used (aluminum is an expensive material to refine) comes from space, for free, via the sun.

      And that was what I was responding to. You think that it makes sense to mine aluminum on the Moon, and I think it is too little return for a massive investment even if it was possible to do on an industrial scale.

      But speculation about such things is a waste of time because, as I’ve said before, we can’t do it with out current technology. There isn’t even any nascent breakthroughs in the development stage that will change this.

      James

    12. Tatterdemalian Says:

      “You can’t reason someone out of what they were never reasoned into.”

      These people want space exploration because we’ve seen the future, and we know Earth is going to die. Billions of years in the future, it’s true, but it’s still inevitable, and we don’t like it, and There Must Be Something We Can Do.

      There are understandable, if not particularly rational, reasons to try to expand human settlement to other planets. Having a backup in case something happens to eliminate all life on Earth is probably the best of these reasons. But this has to be done in a way that makes not just survivable, but economically viable colonies on the surface of other planets. Space itself just does not have sufficient raw materials to build with, and microgravity alone isn’t enough to run an economy on, especially since we can simulate it rather well right on the surface of the Earth with creative use of inertial forces.

      Still, it’s pretty obvious that the desire to live on other planets is there. If only people would channel it into things that might eventually get us there, instead of into conspiracies regarding why we aren’t already there.

    13. Paul Says:

      “You damned sure don’t put raw materials up there — you get them from either the moon or from asteroids, the moon is very plentiful in aluminum oxide.”

      I humbly submit that it will be far cheaper to simply ship the required pieces by rocket than it will be to ship all smelters, rolling presses, and machine tools and extra food and oxygen that your plan would require.

      “The whole costs of putting up some pilot plants are in the hundreds of billions of dollars, with possible RIOs in the multitrillion dollar range. That’s a lot of money but easily within the range of some of the bigger projects done with consortiums”

      Err, which bigger projects are you thinking of? Not only is that far larger than any private industry funded project in history, larger than the available cash to any potential private industry group, that cost is in excess of just about anything I can think of.

      “NO. You’re looking at it all wrong. You need to put people there, and probably enough to put a functioning mass driver on the moon.”

      Probably ranging in the hundreds due to construction (much harder out in space) and auxiliary folks. That’s assuming multiple shifts per day of course. If you wanted to reduce that down to only one shift per day and 16 hours of no work, I’m sure you could make do with less folk, though a much longer construction process. Of course, why you’d use people rather than ground controlled robots on the Moon doesn’t make much sense. And of course that requires that we’re able to build a functioning mass driver that doesn’t tear itself apart after one or two shots and it has to be capable of sending megatons of material per year in order to be cost effective. There’s also the necessity of catching it.

      “That’s not the way you develop undeveloped resources in unexplored areas, and you ought to grasp enough about the manner in which this country was developed to see that. It’s a slow, steady progression to bootstrap such an arrangement.

      The problem of course is that you could live off of the land in previous unexplored areas. You could drop someone off buck naked on the coast of America in the 16th century and they stood a good chance of a reasonable survival. Touch more difficult on the moon.

      “As Robert Heinlein put it, if you’re in orbit, you’re halfway to anywhere. Getting out of the Earth’s gravity well is the biggest trick, and the only reason it’s so expensive still is that it’s been the province of the Federal governments to this point.”

      Ah yes, the Space Libertarian “It’s all cuz of the evil government,” ignoring the notable lack of private industry interest in it. Its been the province of various national governments the entire time because they’ve been the ones with the most interest in and use for space.

      “Probably foamed aluminum would be the best first product, just because it’s an obviously useful substance which you CAN’T make on earth”

      Really? You might want to go tell the companies that are currently selling foamed aluminum that they are doing the impossible. Not to mention that, even were it actually impossible on Earth, it would have to be extraordinarily cheap to be find much use (aluminum became useful only after it could be cheaply produced for instance, as one of the most expensive materials in the world it was rather limited).

      As Robert Heinlein put it, if you’re in orbit, you’re halfway to anywhere

      Correction. You are halfway to nowhere at this point. There are no resources cost-effective out in space with any foreseeable technology.

      Look, here’s the plain and simple truth of lunar mining. A quarter pounder with cheese will cost about 60,000 dollars to send to the moon (lunar greenhouses get into all sorts of silly and leads to large increases in work force requirements and likely is more expensive due to the cost of shipping up enough water for the plants). Now how many quarter pounders is your work force going to consume per ton of material sent to Earth for sale and how in the world do you intend on recouping that cost while still being affordable enough to find use on a large scale (niche applications simply won’t take enough material to be profitable)?

    14. Steven Den Beste Says:

      After you get that mass driver on the moon and start flinging “free” aluminum at LEO, how do you make it stop once it reaches LEO?

      You know, “conservation of momentum” and all that… You’ve got several km/s of velocity to shed somehow.

    15. toad Says:

      Even if we had the material I’m not a big fan of beanstalks. To many security and construction problems. It is kind of like if we had the power sources and materials to build one, those same materials and power sources would eliminate the need for it.

    16. Rich Says:

      Steven: The “cathedral architects” of the 1970s suggested that slowing the mass should be done primarily by gravity (L4 and L5 being stable points; think Trojan asteroids), and brought to a “halt” to work on it by running it down a large cone-shaped mass driver, wired in reverse (KE being bled off by converting it to electrical current and thence to heat. Ignoring the fact that excess heat in space is usually a Bad Thing, and never easy to get rid of properly). LEO was not in the plans. At least, not back then. Who knows what the grand master plan is anymore?

      My biggest problem is with the existence of the whole debate as such. If the worshippers think this is such a hot idea (space elevators, space colonization, or even basic space exploration in general), let them pay for it. Better yet, let them learn the background needed, and get paid for it. If not, don’t force the rest of us to do those things. Conversely, if you’re opposed to the notion, don’t waste your own efforts in trying to convince the worshippers it’s foolhardy – as Tatterdemalian said above, you’re not going to reason people out of what they weren’t reasoned into to begin with. Live and let live.

      (Full disclosure: My childhood fascination with space efforts led to a career in aerospace engineering, to do what I just described above. After learning more about the subject, my actual work – like most of my peers’ – has all been in terrestrial aeronautics and related applications. Make of that what you will.)

    17. Steven Den Beste Says:

      Rich, a “a large cone-shaped mass driver” could get rid of the energy but it can’t get rid of the momentum.

    18. Rich Says:

      Steven: I think, assuming I recall right, that the idea was to treat the “subscript-2″ momentum as the whole “mass-shot plus mass-of-catcher” system, which’d move the catcher a little bit (how -much- displacement would depend on its mass). Then they’d permit the gravity of the Earth, Sun, and Moon to keep the catcher at the stable region. But the architects didn’t do a very good job explaining themselves (even in the NASA “technical papers!”), which on so basic a component of the system is a large part of why it’s still questionably feasible.

    19. Robert Schwartz Says:

      Steven: Why out in the ocean? Why not four miles closer to orbit in the mountains? Clarke’s original novel on the topic “Fountains of Paradise”, posited a location on an island like, but south of Sri Lanka. But, Ecuador is the only spot in the real world where there are really big mountains that lie on the Equator. Kenya has some highlands on the Equator as well.

      Note: Some years ago, somebody, I think it was Rand Simberg, published an economic analysis of the space program, which claimed that per kg prices to orbit would drop dramatically if the tempo of operations were higher. It seemed like a reasonable argument. Other arrangements less dramatic than the space elevator should also be explored like Heinlein’s catapult on Pike’s Peak.

    20. Steven Den Beste Says:

      Because 4 miles closer to orbit is a negligible benefit, and out in the ocean is safer in case the system fails catastrophically.

    21. Shannon Love Says:

      I have been a science fiction nut since I was a child so space travel/colonialization is in my blood but I have to say a lot of space enthusiast these days seem a lot like people pushing “alternative” energy. They want it to work, and work soon, so they do a lot of intellectual contortion to make it seem plausible.

      I see a lot of the same kind of self-righteous attitude that they alone understand the possibilities and that the rest of us are just to stupid and unimaginative to grasp the possibilities. People who raise practical objections are dismissed with hand waving, “who knows what future technology will bring” type arguments.

      I find this annoying because just as in energy debates, the romanticism of manned space exploration gets in the way of practical near term solutions. Space after all is a highly profitable multi-billion dollar private industry. It’s just that the money is in unmanned satellites and they produce and move information instead of goods and people. It’s boring but incredibly important work, especially for the long term. Romanticism can divert funds and effort away from practical solutions and make serious people who advocate a space presence look like loons.

    22. Obloodyhell Says:

      > But that is just it. There are no answers to these problems that will actually work in the real world! Anyone who says otherwise is crazy.

      You’re a frigging IDIOT. These problems aren’t utterly trivial, but all of them are readily soluble, and the cost is substantially less than we put into things like dogfood and cosmetics.

      > It is also a cautionary note since I think it is counter productive when space enthusiasts start talking about projects that are obviously impossible.

      And I’m clearly wasting my time arguing with an idiot. You can’t say that there are no answers and expect to be taken seriously as even vaguely open-minded. You’ve decided the answers — “There are no solutions. End of story. Period”.

      Unlike you, I actually grasp the power of human ingenuity.

      I grasp the capabilities of American enterprise.

      When you say things are “impossible”, you show your absolute ignorance of the depth of the challenge JFK made to place a man on the moon by 1970. At the moment he said that, in 1962, there was no plan for doing any such thing, and no known way to do it. The whole concept of Apollo hadn’t even been investigated in September of 1962. We’d barely even put men into orbit a couple times and brought them back.

      The early space program is a LITANY of abject failures, including the following list of efforts just to put something — anything — THERE:
      Pioneer 0 38 Thor-Able 17 Aug 1958 Lunar orbit Failure – first stage explosion; destroyed
      Pioneer 1 34 Thor-Able 11 Oct 1958 Lunar orbit Failure – software error; reentry
      Pioneer 2 39 Thor-Able 08 Nov 1958 Lunar orbit Failure – third stage misfire; reentry
      Pioneer 3 6 Juno 06 Dec 1958 Lunar flyby Failure – first stage misfire, reentry
      Pioneer 4 6 Juno 03 Mar 1959 Lunar flyby Failure – targeting error; solar orbit
      Pioneer P-1 168 Atlas-Able 24 Sep 1959 Lunar orbit Failure – pad explosion; destroyed
      Pioneer P-3 168 Atlas-Able 29 Nov 1959 Lunar orbit Failure – payload shroud; destroyed
      Pioneer P-30 175 Atlas-Able 25 Sep 1960 Lunar orbit Failure – second stage anomaly; reentry
      Pioneer P-31 175 Atlas-Able 15 Dec 1960 Lunar orbit Failure – first stage explosion; destroyed
      Ranger 1 306 Atlas – Agena 23 Aug 1961 Prototype test Failure – upper stage anomaly; reentry
      Ranger 2 304 Atlas – Agena 18 Nov 1961 Prototype test Failure – upper stage anomaly; reentry
      Ranger 3 330 Atlas – Agena 26 Jan 1962 Moon landing Failure – booster guidance; solar orbit
      Ranger 4 331 Atlas – Agena 23 Apr 1962 Moon landing Failure – spacecraft computer; crash impact
      Ranger 5 342 Atlas – Agena 18 Oct 1962 Moon landing Failure – spacecraft power; solar orbit
      Ranger 6 367 Atlas – Agena 30 Jan 1964 Lunar impact Failure – spacecraft camera; crash impact
      ===================================

      Have you ever actually SEEN one of the blockhouses? Have you looked at the instrumentation for one of the Mercury capsules? The sheer primitiveness of them positively boggles the mind.. It’s like looking at a Conestoga wagon and saying “You guys went over 1500 miles in rough terrain, and through mountain passes, in THIS THING? Wow!”. It’s the same thing: “You guys managed to go into space with THIS piece of crap!?!? Damn!”

      Your forefathers are looking down from above and sneering at you, going, “How the HELL did this lilly-livered pantywaist spring from children of my loins? Woman!?!? What the HELL were you doing when I was out of town!?!?”

      I’m not saying this will be EASY, or SIMPLE. I’m saying it NEEDS TO BE DONE. If NOTHING else, it provides a focus for people to look beyond their own petty little problems. It provides a sense of pride in HUMANITY — not as a nation, or as a race, or as a religion, but in WHAT HUMANS CAN DO IF THEY TRY.

      Shame on you, and every chickenshit pansy like you.

      “Impossible”. Everything is impossible until you do it.

      A friend of mine, back in the 1970s, was an amateur filmmaker. He shot things in super-8. He wanted to shoot a dream sequence, and so wanted to do a double-exposure. He went to a number of different shops, all said the same thing. Everywhere he went, they said, “Nope, Not with Super-8. You can’t do it.”

      So he did it anyways.

      And it worked. The film was a cult classic in the Orlando area for a decade, with regular showings at Fantasy and SF conventions.

      The problems you’re saying are “impossible” are anything but insurmountable. The techniques aren’t even “not understood” — no major breakthroughs are required — they just need to be designed and tested and the inevitable little kinks need to be worked out.

      I went to the World SF convention in 1992, in Orlando. There was a panel there on going back to the moon. In response to a question, the panel, made up of people from NASA, said, and I quote, “We could not make it back to the moon in 10 years if we wanted to”. The audience did a double take. “You mean we don’t have the will”. NO. “You mean we can’t get the political support”. NO.

      These idiots were *actually* saying that we could not accomplish, with 1990s technology, what had ALREADY been accomplished with 1960s technology, PERIOD.

      Welcome to the sub-genius club. You should apply for a job with NASA. You’d fit right in.

    23. Obloodyhell Says:

      > I humbly submit that it will be far cheaper to simply ship the required pieces by rocket than it will be to ship all smelters, rolling presses, and machine tools and extra food and oxygen that your plan would require.

      Paul, you’re looking at this very, very wrong, just like James. You’re thinking “transplant the existing stuff up there”.

      That’s NOT the way you bootstrap, unless you’re obscenely rich.

      You make a small, straightforward device designed to have lunar dust put in one end and blocks of aluminum coming out the other end, using solar power to do the cracking. The idea is NOT to make a large-scale project to start, but to get the basic blocks you can use to go further, without HAVING to port everything there. From that base of refined materials you can make most of the larger things with machine shops and machine tools and PEOPLE.

      When you’re building a town in the 1850s in Kansas, or wherever — you don’t ship log-cabins to Kansas, you don’t ship 20 ton ore smelters to Colorado. You put smaller devices in place to give you the power to take WHAT IS THERE and build what you need from the raw materials (trees, ores, in the 1850s case). You put the minimum of what is needed to turn the local substance into the things you need to build bigger things that can make the quantities of stuff you want.

      That is how you bootstrap.

      That’s where the term comes from. “Pulling one’s self up by one’s bootstraps”. When the computer is booting up, it doesn’t load the entire operating system from the first load, it loads a piece of it, then a larger piece, then the rest gets pulled in. It’s a multi-stage process.

      The first steps on the moon and in space aren’t going to be industrial scale. There’s a lot of things we need to develop an understanding of first, most notable manipulating things in microgravity, and the alterations in processes which microgravity causes. Microgravity will create problems, but it will also provide new techniques and new ways of doing things which will make us all quite rich in the long run — such things do. You always get rich learning new ways to manipulate the world around you.

      > Err, which bigger projects are you thinking of? Not only is that far larger than any private industry funded project in history, larger than the available cash to any potential private industry group, that cost is in excess of just about anything I can think of.

      Really? How much did the international air transport system cost to develop? What about the infrastructure supporting the automotive transport industry in the USA? What are those things valued at, in terms of total assets — planes, airport terminals, air traffic control, training facilities, ticketing systems, fueling logistics…?

      Did someone design all that in 1910, from designs someone figured out, or was it built from scratch over time, using initially primitive techniques that developed into some pretty damned sophisticated solutions? Evolution works in human systems, too.

      > Probably ranging in the hundreds due to construction (much harder out in space) and auxiliary folks.

      BS. You’re not trying to do this as a bootstrap, you’re trying to make a fully functional industrial-grade facility from scratch. Not only is that foolish (the fact is, that, on the spot, there’s going to be a lot of stuff you need to resolve due to the fact that things that worked in Earth gravity might not be the best option in microgravity or lunar gravity), but it’s not the way you bootstrap. You start small, you work out the kinks, and you build on what you’ve started.

      > Ah yes, the Space Libertarian “It’s all cuz of the evil government,”

      Ah, yes, the ignorant naysaying idiot who can’t deal with the idea that someone might actually not fit your own narrow-minded little picture of How Things Work.

      The government CERTAINLY has done little to nothing to encourage man in space since the Apollo program wound up. But at least some of this is due to intentional efforts by NASA to eliminate any real effort to produce competition.

      Are you aware that NASA destroyed all the documentation on the Saturn V rockets, specifically to be sure that no one could obtain them, and no private organization could create Saturn V’s (or Saturn 1B’s) to compete with the Space Shuttle? Millions of man-years of technical development. Gone. So that the Shuttle could not have any private-industry competition. EEEEvil? No. Just typical government bureacracy.

      > Correction. You are halfway to nowhere at this point. There are no resources cost-effective out in space with any foreseeable technology.

      Not with your lame ass attitude, no. Absolutely correct.

      “But, sir, what use is it?”
      “Madam, of what use is a newborn baby?”
      – Faraday –

      > After you get that mass driver on the moon and start flinging “free” aluminum at LEO, how do you make it stop once it reaches LEO?
      > You know, “conservation of momentum” and all that… You’ve got several km/s of velocity to shed somehow.

      Steven, how do you dare manage to think yourself able to hold a worthwhile opinion on the topic when you don’t have the slightest understanding of the basic fundamentals of orbital mechanics?

      1) I didn’t say put it into LEO, I said Lunar Orbit. That’s where you put the early refining efforts, to assist in the activity of developing an actual understanding of the way microgravity affects materials processing, which is far more the overall purpose of the activity.
      2) You might have noticed that foamed metals, in industrial quantities at low costs (as opposed to the limited availability takes microgravity. That is to say, they aren’t being done on the moon, either, but in orbit. Also note the possibility of high variation in the degree of foaming, really impossible on earth. How about aluminum which varies in density from 5% at one end to 50% at the center to 5% at the far end? Or varies from 20% at the bottom to 5% at the top? Or whatever. The ability to play with this stuff, to manipulate it at will, to really get an understanding of it is where the money is.
      3) How does it get from SO to earth? Does this really need to be explained? How does the shuttle get back to earth? The aluminum in question isn’t subject to human limits on g-forces, you might also note, since making such obvious leaps seems to be beyond some of you.

      > Rich, a “a large cone-shaped mass driver” could get rid of the energy but it can’t get rid of the momentum.

      OK, Steven: Hint: energy, momentum, they’re pretty much interchangeable. You can ALWAYS figure out how to deal with one when you have the other. At worst case, you have to somehow provide a measure of reaction mass (slag from the moon, anyone?), but JUST OFF THE TOP OF MY HEAD, probably the easy thing would be to tie several of these together and just hit them from different directions so the sum of the momentum involved cancels out. D’OH! I guess that was too complex a notion for you to consider, you being all happy that you’d poked yet another easily-surmounted “insurmoutable problem” into the mix, right?

      > Space after all is a highly profitable multi-billion dollar private industry.

      Actually, I have no problem with this — the problem I have is with people who START from the idea that man-in-space is an insurmountable problem rather than what it really is — an engineering problem, with most of the underlying techniques having fairly apparent solutions. Te devil is ALWAYS in the details, but that’s mostly what remains to be worked out.

      And space-tourism ALONE could easily pay for the cost of developing basic access to space, amortized over the course of about 30 years.

      What’s been lacking is a will-to-do, more than anything else. The amount of money we spend on ridiculous things like “wool and mohair price supports” (back in the budget after a year or so absence to break its 60-year run in the Federal Budget) is insane. But people like Rich are too busy making statements like “If the worshippers think this is such a hot idea (space elevators, space colonization, or even basic space exploration in general), let them pay for it.” to notice that we ALREADY pay for a hell of a lot of crap with far less potential value to all humanity, much less America, to care.

      It would all go a lot faster with a number of X-prizes set up to guarantee basic funding for such. Nothing gets paid out unless the goal is accomplished and the technology licensed. That encourages business to build up in a direction without actually costing anything unless they accomplish the goal. And it’s a worthwhile goal. Anything which vastly increases our understanding of an area we know next to nothing about — microgravity, the moon, whatever — is a worthwhile goal. And tends to make us rich as hell besides.

      =====
      Rich, re: momentum issues, part of what you’re ignoring is that, as you mentioned yourself, the usage of the Lagrange points. A catcher in those locations will get moved back into them by basic orbital mechanics of the earth-moon-lagrange point locations. The L4 and L5 positions are stable, as in “at the bottom of a bowl” (unlike the L1,2,3 positions which are stable like “balanced on a pin”). Thus, getting nudged slightly out of position a bit is irrelevant, The catcher’ll drift back into place… and that’s assuming, as I note, that you don’t rig your acquisitions so as to provide a fairly neutral momentum summary in the first place, which is almost a guarantee. By manipulating the mass driver and the time of launching, you can give these things just about whatever orbit you want, something Steven hasn’t figured out yet.

    24. Steven Den Beste Says:

      The L4 and L5 positions are stable, as in “at the bottom of a bowl” (unlike the L1,2,3 positions which are stable like “balanced on a pin”). Thus, getting nudged slightly out of position a bit is irrelevant, The catcher’ll drift back into place…

      That’s not what happens. They start orbiting the center of the bowl. If they are perturbed too much, they achieve escape velocity and leave it entirely.

      A lot of this discussion discounts the motion conservation laws. It’s like those people think that if you have a weight on the end of a string, and pull it up to an angle and let it go that it will fall back to the bottom and stop. That’s not what happens. It starts swinging back and forth — because energy and momentum are conserved.

      It turns out you can use a timing trick at the L4 and L5 points to get rid of the momentum. The excess energy can be radiated away. But that trick won’t work at LEO or at geostationary orbit because there isn’t any “bowl” to take advantage of. If you use a mass driver on the moon to ship industrial goods to Earth orbit, you have to figure out how to stop it once it gets there — and there’s a lot of momentum and a lot of energy to shed, somehow.

      By manipulating the mass driver and the time of launching, you can give these things just about whatever orbit you want, something Steven hasn’t figured out yet.

      No, that’s not true. You can give it orbits which conserve energy and conserve momentum — and those may not be the orbits you want.

      But let’s ignore those issues. I’ll settle for one answer to one specific question regarding a space elevator: once you have all the materials in hand, and all the money and political will you think you need, how do you build it?

      How, exactly, do you get the cable connected between the anchorage and the orbiting counterweight? Once the counterweight is in space, and the anchorage has been built, and you’ve got a big spool of cable either sitting next to the anchorage or orbiting with the counterweight, how do you string the cable between the two?

    25. lolwut Says:

      Jesus christ. They NEVER solved the catcher problem. Have you ever looked at anything besides THE HIGH FRONTIER (o great o’neil bless us with ur presence)? NASA has put a lot of this material online, I suggest you go seek it out (catcher stuff INCLUDED).

      “It’s the Manifest Destiny before us.”

      y helo thar libertarian ideology. Pity theres no indians to genocide.

      “These idiots were *actually* saying that we could not accomplish, with 1990s technology, what had ALREADY been accomplished with 1960s technology, PERIOD.”

      For all your blathering about OMG SIXTIES TECH, you completely fail to realize that america did not, and still does not, have anywhere near the launch capability to do a lunar mission. Full stop. End quote.

      http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html

      Charles Stross lays it out out very nicely.

      “And I’m also poking fun at the conceits of the secular religion the space settlers have brewed up for themselves to replace the good old-fashioned gunpowder Calvinism they grew up with. (They tend to be conservative or libertarian, with a small-town background: funnily enough, they tend not to be Christian as well. My suspicion is that they began questioning their background assumptions and kinda-sorta rejected the original religious programming even as they latched onto libertarianism as an acceptable dissident ideology. But throwing out the Jesus-squeezing left a God-shaped hole in their hearts, and settling the galaxy is the sort of abstract, teleologically oriented millennialist project that plugs neatly into that space.)”

    26. Steven Den Beste Says:

      Unlike you, I actually grasp the power of human ingenuity.
      I grasp the capabilities of American enterprise.

      In essence, what this guy is saying is, “If only we can get enough people to believe in the dream, then someone will solve the problem.”

      But that’s religion. It isn’t engineering. If you press this point, you’ll get some sort of comment to the effect, “Look at all the technological miracles we already have! How can you say these other things cannot be done?”

      Speaking as an engineer myself, I find this particular argument especially offensive because it’s not only religion, it makes we engineers into the gods of that religion. And we aren’t.

      Yeah, there have been miracles. I’ve helped create a few of them. But there have been a lot of other miracles that didn’t happen. Where’s my flying car?

      Engineering miracles are still tightly constrained by the laws of physics. We don’t get to ignore the conservation laws. We can’t change the universal electrical constant. And if some hoped-for miracle can’t be solved without doing those things, then that miracle won’t happen.

      “If anything is possible, then everything is possible.” Uh, no. It doesn’t work like that.

    27. lolwut Says:

      And to quote Hemingway: “You will die like a dog for no reason.”

      THAT is the future, not some star spanning libertarian wunderland populated by the Correct and Right Thinking (as well as white) apostles of Ayn Rand (peace be upon her).

      No.

      The future is a hellhole out of sub saharan Africa. You want to see the future? Look at the DRC. Look at Somalia. Theres the future. The oceans will be dead, the rainforest gone, mass starvation, genocide, famine, the desertification of north American farm land.

      And before you go off throwing out TWO FISTED GEOENGINEERING schemes from the bowels of slashdot: know that climate scientists laugh at the idea. Really. The consensus that I’ve put together by reading the material is either a) go to a standard of living comparable to the DDR, b) we are fucked.

      Knowing people it will be B.

    28. David Gillies Says:

      “How, exactly, do you get the cable connected between the anchorage and the orbiting counterweight?”

      The most plausible idea I’ve seen is you launch a satellite with a large spool of very thin cable material into GEO, then allow the satellite to drift out as you unspool the cable, keeping CMS in GEO. You catch it in the atmosphere and tie it down. Then you run a progressively larger series of spiders up the cable, bonding additional lengths of fibre to it. The spiders become part of the counterweight, which needs to become more massive as the cable gets thicker. ‘Cable’ conjures the image of a cylinder, but a flat ribbon is more likely. Furthermore, the maximum tension in the cable is not at either end but in the middle. So its cross-section will need to be variable.

      I personally don’t think the materials science is the main feasibility issue, at least from a tensile stress standpoint. Even though we are not there yet, there is no fundamental physical barrier to creating a sufficiently strong material (the C-C bond in graphene is adequate for the task). However we have no idea of the feasibility of unreeling a multi-thousand km wire without it tangling. The power source for the spiders is another issue. There’s talk of powering them through the cable, which is idiotic (the problems of maintaining adequate insulation along a structure that large probably really are insurmountable.) More likely is lasers focussed on photovoltaic arrays. Bigger issues are, I believe, with the environment in which the elevator will have to live. It will pass through both Van Allen belts, which are not areas in which unshielded humans can live for any length of time. The time to orbit will be of the order of days. The cable material will be attacked by monatomic oxygen in the upper atmosphere. It will be strongly vulnerable to micrometeorite abrasion in space, and lightning strikes in the atmosphere. Avoiding resonance effects will be problematic. We would need to eliminate orbital debris, which is a mammoth task. Terrorists could bring the thing down with a Cessna, or a low-cost cruise missile. A functionary of a national government could bring it down by lifting a telephone and instructing that it be so.

      Handwaving these difficulties away as stemming from insufficient will is no answer. Problems do not cease to be problems simply by claiming them otherwise. The chief barrier to a space elevator is not feasibility, but practicability.