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Science

Sir Arthur Speaks 84

Posted by Hemos from the listen-to-wizened-one dept.
rw2 wrote to us with an interview with Clarke in the NY Times. Login, of course, is required, but the interview is worth reading. Talks about space elevators, Kubrick & 2001 amongst other interesting subjects.
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Sir Arthur Speaks More

Sir Arthur Speaks

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  • Did anyone else think of Red Mars and start to worry about the idea of a Space Elevator? At least when a rocket explodes or a satellite orbit decays, it only ruins a small chunk of real estate.

    Sure, it would be cool... but you won't catch me moving to the equator.

    --
    QDMerge [rmci.net] 0.4!

  • Good article (Score:3)

    by Otto ( 17870 ) on Tuesday October 26, 1999 @09:56AM (#1586078) Homepage Journal
    I'd read about his space elevator concept, both in his books and in actual papers on the subject.. Like all good ideas, it's very, very simple.. But I still thought diamond was the way to go.. I'd never considered bucky tubes.. genius man, genius..

    Good Line here:
    By the way, I'm an absentee landlord of a hundred square miles of some rather rugged territory near the orbit of Mars. I have an asteroid named after me. Isaac Asimov's got one too. It's smaller and more eccentric.

    Ha! Asimov would have loved that..

    Let's see here... more browsing.. ah ha! He talks about how he originally came up with the idea for the geosyncronous satellite for communications:

    Q. One of the legends about you is that you came up with the idea for Comsat in an article you wrote in 1945 and that you never patented the idea.

    A. Oh, so you want to ask me about how I lost a billion dollars in my spare time? Well, you see when I wrote my "comsat" paper, it was 1945....I didn't think that satellites could be launched until the end of the century.... I just wrote this article and sent it off and got £15 for it....what I should have done is to try to copyright the word "comsat." If I'd done that....

    Good one.. Bit uninformative of anything new, and definitely the article is way too short.. I'd really like to see an indepth interview, or at least to read about whatever he wants to write about.. Someone like Clarke, well, they're just plain interesting, all the time..




    ---
  • Well, at least if we do it, we won't have to be dodging Deimos and Phobos as the elevator rotates..

    but using Buckminsterfullerenes is cool..

    I think in the Mars Trilogy they called em "Bucky Balls" kinda cool..

  • There are plenty of 'free' logins.

    cypherpunk/cypherpunk comes to mind.

    Let the list begin again =)
  • 51% percent of survival? I'd buy that. I would like to know what he thinks about that UN population implosion report.

    I did not realize that nanotubular carbon was so strong. In high school (it was a long time ago) about I did a paper on Bucky Ball (aka C-60) and it's ability to encapulate RNA for gene repair.

    Why can't nanotubes be produced in bulk? What kind of contrants are involved in it's production process?

  • Re:Clarke is the man (Score:3)

    by Bearpaw ( 13080 ) on Tuesday October 26, 1999 @10:21AM (#1586085)
    Why can't nanotubes be produced in bulk? What kind of contrants are involved in it's production process?

    The current production technique [rice.edu] is a bit awkward and labor intensive. But samples can be purchased here [rice.edu].

  • Uh... all logins are free. It's a free site.

    The reason it doesn't say so is that Rob & Co. were sick of writing "Free registration required" at the end of EVERY news item linking to NYT.

  • What I meant when I said 'free' logins are the ones that don't actually have anything to do with my demographics. In other words, a login we can all use so that there's no information collection. A beat-the-system kinda thought.

  • Space Elevator materials. (Score:4)

    by Tau Zero ( 75868 ) on Tuesday October 26, 1999 @10:36AM (#1586088) Journal
    You wouldn't be using Buckyballs, you'd be using Buckytubes. A Buckyball is an interesting molecule, but it's a ball; not very useful for making a cable. A Buckytube is made along the same principles of connected triangles of carbon, but there's a large section between the two ends which is like a plane of graphite wrapped around and spliced to itself, forming a pipe. Now THAT can make a cable.

    The problem with a geosynchronous skyhook is that if it breaks, there's a hell of a lot of stuff that's coming down, hard. Fortunately, you don't have to use a skyhook for that. "Space fountains", Lofstrom loops, Jacobs Ladders and other ways of exploiting kinetic momentum could build structures that wouldn't be so tall that they'd span an ocean if they failed; if they were all sited on Eastern shores with nothing but open water to the dawnward, breaking them would only make some waves (ahem).
    --

  • Did anyone else think of Red Mars and start to worry about the idea of a Space Elevator? At least when a rocket explodes or a satellite orbit decays, it only ruins a small chunk of real estate.

    Sure, it would be cool... but you won't catch me moving to the equator.

    I think this wouldn't be a problem if you made the elevator from "bucky-tubes." It would be very light, and probably would just burn-up/float away before any real damage could be done.

  • The "cypherpunks" account no longer works.. No Sir Arthur Clarke for me (unless someone cares to email me the text in the article)!

    -- Does Rain Man use the Autistic License for his software?
  • A very good read. Nice to see that he still has such wit at 81. I especially liked this one:

    "I have difficulty remembering names. But I feel as long as I can spell "Alzheimer," I'm in good shape."

    I agree that the article was a bit short. I would have liked to hear a bit more about what he thinks of the future.

    "I think we have a 51 percent chance of survival. I would say the next decade is perhaps one of the most crucial in human history, though many people have felt that in the past. But it's real now."

    That's a pretty pessimistic view, but that doesn't mean that it's far from the truth. He might very well be right. We are living in a crucial era. The choices we make in the next decade will be of great importance.

    -- J J

    "There's always a bigger fish."
  • The only accurate information they can record about you is your IP address. There is nothing forcing you to use your real name, demographics, or anything else. They can't prove that you're not an 84 year old Albanian woman who makes half a million dollars each week from her investment portfolio.

    So just create an account. Personally, I just randomly type letters and click boxes until it lets me in. The random crap is saved in a cookie, if the cookie goes away then I give it more gibberish.

    Username: dkjal;ajk;lkdjasl
    Password: asdfgh (needs to be same twice)
    E-mail: lkj@sdfsdf.com

    etc ...

  • interesting electrical properties too (Score:3)

    by garyrich ( 30652 ) on Tuesday October 26, 1999 @10:45AM (#1586093) Homepage Journal
    In addition to great strength, by changing
    the orientation of the carbon rings you can
    get a conductor, a diode or a semiconductor.
    Extremely cool things. The 1st folks that
    can make them in industrial quantities are
    going to get fantastically rich.

    in re falling skyhooks: couldn't you set it
    up so that a disaster would cause a disconnect
    at the base so that it would (in most cases)
    fall up rather than down? I still wouldn't want
    to be on it at the time. I recall some papers
    from a few years ago also that showed skyhooks
    to be fairly stable, statically and dynamically.

    garyr
  • I read Red Mars, but didn't worry about the idea of a space elevator. But then again, I've also read The Web between the Worlds and The Fountains of Paradise.
    The former, btw, was written by Charles Sheffield who's been described as a successor to both Heinlein and Clarke. These labels don't do him justice.

  • I had the pleasure to meet Sir Aurthur in 1996 on a visit to Sri Lanka and was struck by how incredibly sharp this guy is, despite how frail he seemed when I met him. An old man in a wheelchair he may be, but he has a mind like a razor. Here's hoping he keeps going for a while longer.

  • Of course in the Fountains of Paradise, the diamond filament was so thin that you couldn't see it. Walking through it would cut you in half!

    The hard part is putting enough weight up in space to be able to lift a large load.. and keeping stability would be tough too. It's like using a baloon.

    Imagine the winds and huricanes and natural phenomenon. Plus, there'd have to be alot of cable monitoring systems. Cable would need to be replaced.

    Pan
  • How would it fall 'up' instead of down?

    It would seem obvious that the only gravity well nearby is the Earth, and as the top of the elevator would be in geosynchronous orbit (or would it?), the only place for things below the geosynch point would be to fall down the gravity well.

    Or is there some way that the base could be pulled up into orbit?
  • Well you could buy a copy of the paper. IMHO it is not at all unreasonable for the NYT time require you to login to their site. They spend a lot of money to gather all that news. Hell they have to pay the guy who goes and does the interview and the editor etc. You get the product of all that for *FREE*. If you don't want to login buy a copy of the physical paper at your newsstand.

  • He was knighted after all? I thought that the flap over charges that he is a paedophile caused the British to withdraw the offer of knighthood. Does anyone have the story on this?

  • You're mistaken. This is about Arthur C. Clarke. If you haven't heard of the guy, I honestly don't know what to say, except 'read a book'.

    In respects to buckytubes, I thought we were just starting to produce them in industrially significant quantities a year ago. I was hearing about all sorts of applications for them, from structural materials to ultra-thin computer monitors. What happened? Where's all the cool new toys? :(

    "Read a book!!!" - Handy (longtime companion of the Human Ton).

  • "Any sufficiently advanced technology is indstinguishable from magic."

    Hmmmm... perhaps it's time to change my sig line? ;-)

    Zontar The Mindless,

  • "The hard part is putting enough weight up in space to be able to lift a large load.. and keeping stability would be tough too. It's like using a baloon."

    Not so; do the math. A space elevator is at tension; it's anchored to two points at very different (linear) velocities, and all the points in between want to fly off. Due to the strength required for this, not to mention the enormous length, the thing is far more massive even at its smallest imaginable size than anything you might want to lift on it, and stablility problems are similarly solved.

  • Q. One reason you advocate space travel is fear of asteroids?

    A. I'm always quoting the science fiction writer Larry Niven that "the dinosaurs became extinct because they didn't have a space program."

    Or electricity for heaters, or bomb shelters, or the ability to grow food without soil or direct sunlight, or the ability to clone species, or yada, yada, yada. If we have the ability to relocate a large enough population to an acceptable destination, I'm gonna guess we can stop an asteroid (yes I know how difficult it is).
  • Yeah, the article was really a fluff job. Too bad they wasted an opportunity to really ask him some questions. Obviously the reported wasn't prepared.

  • login: uncle_duke
    password: trudeau
    And of course the country is American Samoa!
  • Hrmm...


    <dig dig>

    This paper [islandone.org] seems to suggest that due to the Earth's rotation, an object farther away from the surface will build potential energy in much the same fashion that the blades of a celing fan move faster at the tips.


    From the paper:


    The classic example is a skyhook, a cable in geosynchronous orbit long enough to reach down and attach to the ground. A payload which climbs the skyhook builds potential energy, gains momentum from the Earth's angular momentum, and can go into orbit.

    Thus, it would seem to me that if you attach the earth end of the elevator to the Earth and have enough weight at geosynchronis orbit, if the elevator broke then the broken piece would fly off into space, or at least orbit (think broken fan blade). What would happen to the attached end I couldn't say...
  • cypherpunks321 (pass=cypher)

    or create your own account.. it's free and you don't even have to give them a real email address, they don't mail you your password or anything.

    The above account is made out for a male from Uruguay with email guest@hotmail.com. So if, you're paranoid, they won't know anything useful about you.
    ---
  • Use login cypherpunks01, password cypherpunks01. Or cypherpunks02, etcetera. Someone mentioned in another thread that there are over a hundred "cypherpunksN accounts on the NYT site.
  • Or is there some way that the base could be pulled up into orbit?

    Well, let's say that the mass of the elevator would be pretty low, since its use of buckytubbes, but still have a great tensile strength.
    Then "all" that would be needed would be to place the receiving station (space part) further away than the normal geosyncronous orbit, so that eccentric forces would "pull" exert a pull on the entire ladder.

    Well, hum, there's one tiny little problem to all this, geosyncronous orbit is about 36'000 Km up.
    And i sure hope that those buckytubbes are more stable than my Legos ;)

    Murphy(c)

  • Re:Clarke is the man (Score:3)

    by Big Electric Cat ( 101345 ) on Tuesday October 26, 1999 @11:24AM (#1586111)
    To clarify, all the current ways of producing nanotubes involve making a big mess out of some carbon, and then separating the nanotubes out. While the percentage of molecules that turn out to be nanotubes can be improved with sophisticated techniques like the one described above, it seems like what you'd want for construction would be long tubes. I can't see how you'd get those other than with nano- or organic assemblers...
  • Maybe you need to check this article [slashdot.org] our before you make an a judgement on how anonymous you really are.
  • simple.

    ensure the center of gravity of the breakaway portion is at greater than geo orbit altitude.
    this makes for 2 nice properties:

    1. cable always in tension ( centrifugal force
    pulling cable out like tennis ball on a
    string.

    2. in event of breakaway, fall "up"

    unfortunately, our idiotic government would never cough up the funds to do basic development of the components necessary to build such a thing...


    I am 32 yrs old.
    When I was 5 ( 1972 ) it was reasonable to believe that within my working lifetime, I would be able to go to orbit as a tourist.
    we were progressing that fast. the technology (except HAL) of 2001 was reasonable. everything (technologically speaking) in that movie COULD have happened by now.

    somewhere along the line we lost our way.

    the government fell in love with the space shuttle, a brilliant idea, flawed execution.

    the government fell in love with the space station, again good idea, crappy execution.

    if we had only....


  • One thing's for certain...your frothing-at-the-mouth, holier-than-thou attitude is amusing in the extreme.

    I thought we were discussing A.C.C.'s ideas, and the logical extension of same, such as buckytubes and skyhooks (an interesting discussion thus far). Perhaps the subject of his sexual proclivities ought to be discussed elsewhere.

  • somewhere along the line we lost our way.

    the government fell in love with the space shuttle, a brilliant idea, flawed execution.

    I think the problem was that the government (well, congress) didn't fall in love with the shuttle. They cut the budget down so much that development was drawn out (beyond the lifetime of Skylab, for example), and high operational costs had to be accepted in favor of saving development funds.

    the government fell in love with the space station, again good idea, crappy execution.

    This is again a case where congress both didn't properly fund the program, and (more importantly) kept screwing around with the designs, forcing nasa to delay construction. Any of the early designs could be in orbit right now if congress had just kept their hands off things.

    Of course the whole space station problem goes back to Nixon and the refusal to do another Saturn V production run. Building a space station using a vehicle designed for station resupply (ie: the shuttle) is just stupid.

    if we had only....

    Intelligent people in washington?

  • I don't know about anyone else, but AC is truly "THE MAN" in my book.


    In all honesty I don't know of anything that I can find at fault with him (other than his Mysterious World of Arthur C. Clarke which, I will admit, is truly entertaining to watch, but is total bunk science.)


    Anyway, to this day whenever I pick up one of his books, the first thing I think of when I read something about some gizmo is "okay...." but then I soon say "Wow!" when it finally sinks in just what the thing does.

    If there should be a patron saint of /., AC gets my vote.


    941415926518293950285123123568785948184839358193 948913958495
    80124569890476636201512012315668018651125564087489 7980465063
  • What would happen to the attached end I couldn't say...
    It goes the only place it can: down. And since it is rotating along with the Earth but at a greater radius, it has a greater eastward velocity than the Earth's surface so it falls to the east, wrapping itself around the equator like string around a ball.

    It wouldn't be particularly nice to be around, like a broken steel cable whipping into its attachments and ripping up anything that gets in its way. It would be best to be elsewhere.
    --

  • It was a rumour in one of the British tabloids.

    The knighthood had already been granted, but the timing of the story was such that Clarke asked that the ceremony be postponed until he could respond to the charges.

    Statement by Sir Arthur's Executive Secretary, on the SFWA website [sfwa.org]

    I haven't heard anything about the outcome of Sir Arthur's legal action against the paper.

  • Clarke, Technology, and this Interview (Score:3)

    by Hrunting ( 2191 ) on Tuesday October 26, 1999 @12:03PM (#1586120) Homepage
    Given the fact that this item is up on the NYT home page and not buried in a paper somewhere (although I'm sure it's there, too), I wonder what Sir Arthur's connection to all this technology that he's always seemed to predict is. Does he use the Internet? Does he think computers with HAL's intellect will one day exist and should we fear them?

    He'd make a great target for a Slashdot interview. The questions from the NYT were nice, but I don't think they were posed by a geek. Given the reverence to which we hold Clarke, I'm sure that if we were asking the questions, you could probably write a whole 'nother novel with the answers.

  • 3001 (Score:2)

    by eries ( 71365 )
    Too bad the author didn't get a chance to talk about 3001. I felt like such a sucker after buying that - I found it really immature and ideological. What could he have been thinking? He seems pretty smart in the article, I guess he just doesn't take his fans too seriously. Alas
  • OK, I'm ignorant. In English, what are they?

    And how likely is it that they'll be cheap enough to do what he is proposing anytime soon?(and he said it'd still be $1 trillion, where's that budget surplus?)

  • no YOU make me sick (Score:1)

    by Anonymous Coward
    We must stop promoting this disgusting puritan attitude that there is somehow something wrong with sex. You need to be flogged repeatedly. Children should be introduced to sex at the youngest age possible, in order to not pervert them as society has done. If arthur c clarke is a pedophile, that is just another facet of his genious.
  • I'm glad to hear that it turned out this way. It's unfortunate that the initial splash of scandal gets widely publicized, but the resolution that the scandal was in fact libel never seems to get the same level of publicity.

    I've long been an admirer of Sir Arthur's writings, especially the hilarious Tales from the White Hart [amazon.com], and the marvelous Childhood's End [amazon.com]. Neither receive the publicity of his later 2001 and Rama related work, but in my opinion are far more interesting.

  • It might be designed to 'break-up' into sections in such a case, with parachute or balloon assist.

    Or perhaps the broken Earthward end could be retracted at such a rate that it never completely 'falls over'.

    Or the broken Earthward end could manipulate the falling structure from the base in such a way to make it 'coil' to some degree as it falls, limiting the impact to a very large but pre-determined area.

    Or it could be made to 'disintigrate' on demand in the case of an emergency, hopefully into something bio-degradeable. Maybe there's a resonance frequency or some-such that could make Bucky tubes fly apart.

    In any case, the ascension vehicle would clearly have to be capable of making a controlled descent on it's own from any point on the hook.

    Interesting puzzles, but probably not insurmountable.

  • Re:Terminal ballistic qualities if it falls ;-) (Score:3)

    by Tau Zero ( 75868 ) on Tuesday October 26, 1999 @02:08PM (#1586130) Journal
    It might be designed to 'break-up' into sections in such a case, with parachute or balloon assist.
    If the break was 4000 miles up (18,300 miles down from geosync), the bit at the top end of the bottom segment would have an eastward velocity of about 1050 MPH relative to the surface and potential energy equivalent to a speed of roughly 18,000 MPH. You are NOT going to stop this thing with a parachute.
    Or perhaps the broken Earthward end could be retracted at such a rate that it never completely 'falls over'
    You can only guide it while it is moving slower than the speed of sound in its own material; after that, any change of tension or direction gets shoved downward by the motion of the material faster than it can propagate upward. On the other hand, by reeling it in you can increase the speed (thus kinetic energy) of what's about to smack you. If that happens, osculate your posterior farewell!

    One thing here: The entire skyhook, which is rotating about the Earth's axis on the same 23 hour 56 minute sidereal schedule, is moving eastward and will keep moving eastward; the downward pull of the lower sections will "crack the whip" and accelerate the upper sections to even higher velocities (eastward and downward) than they would attain as disconnected masses.

    Or it could be made to 'disintigrate' on demand
    This is about the only thing you could do. Since Buckytubes are made out of carbon, they can burn in an oxygen atmosphere. After the speed gets up to a couple thousand MPH, the heat created by the supersonic passage through the air should be enough to keep a flame going. If the skyhook cable could separate itself into very fine filaments on its way down, it would either burn or turn to dust. The dust may be harmful, but at least it would not make tsunamis.

    As for the sonic booms this might create, I have no idea how damaging they might be.
    --

  • I think this has been answered pretty well by othre posts, but -- it's not quite a geosynchronous orbit. If were perfectly geosynchronous then something like a hurracaine could pull on the cable and yank the entire thing down. You pull it down enough with the cable that the cable is tensioned and will resist environmental forces that would tend destabilize it. You'd still get standing waves in the cable, but I gather these are not as big a problem as they could be.

    anyway, this means that the centrifugal force is larger than the gravitational force. So, if you just let go of the bottom of the structure it should be hurled away from the earth like a fanblade. In the aforementioned Red Mars Scenario terrorists blew up the anchoring satellite. Losing the ballast like that make it fall to earth regardless. Lacking an anchor point it may do less damage, but still a big mess. Megadeaths, bad press, angry investors. An all around bad day for everyone.

    garyr
  • It goes the only place it can: down

    OK so far...

    And since it is rotating along with the Earth but at a greater radius, it has a greater eastward velocity than the Earth's surface so it falls to the east, wrapping itself around the equator like string around a ball.

    Actually, no. Although the top of the cable does possess a greater angular velocity than the bottom, it is also moving through a proportionally greater arc of space. After the cable snaps, the only thing that has changed in the equation is that the cable/payload unit, which was suspended due its center of mass lying beyond geosynchronous orbit, is now a separate payload unit outside geosynchronous orbit (more on that later), and a cable, whose new center of gravity is well within geosynchronous orbit. Thus, the cable cannot remain in its suspended state, and falls. As it falls, atmospheric effects (read: wind) may influence its fall, but by and large, it will come straight down. This may be a problem, particularly if the thing breaks high up on the chain. Don't be below this thing when it falls (visions of the fall of shadow square wire in Ringworld come to mind).

    In respects to the payload, all that will happen to it when it disconnects is it will attain a higher, non-geosynchronous orbit, where it will remain (hopefully until astronauts can effect a rescue of the crew).

  • No, it can't come straight down, except the first infinitesimal increment of motion.

    I could go into detail, but at this hour the only thing I'm going to tell you is to review your coursework relative to rotating frames of reference, which is a rather important issue you appear to have neglected. Check out Coriolis acceleration if you are having difficulties.
    --

  • The energy requirement to significantly change the orbit of a 10 km asteroid is roughly equivalent to what it takes to accelerate at least a few million people to the speed of light. Asteroids are heavy, people aren't - it's going to be a lot more energy-efficient to move the people. Plus, once we have a few hundred million people in space the population not living on earth will likely explode just as it did in the Americas from 400 or so years ago.

  • You don't need to relocate billions or even millions, just enough to ensure the survival of the species.

    The smart thing to do would be to choose a small human population with a large genetic diversity, and a large enough selection of other animals, plants etc to keep the survivors fed. Noah's Ark, in other words.

    The interesting part would be choosing who goes and who stays...

  • Trust me on this, they are plenty stable. If I remember correctly, they have something like 4 or 5 times the needed tensile strength... Although I could be forgetting.... (it might be like 2 times... But I'm pretty sure it's more). I once knew ;)
  • "Any sufficiently advanced technology is indstinguishable from magic."

    The same can be said of any sufficiently advanced card game.
    --
    "HORSE."

  • No, it can go either up or down if it breaks.. Think of the cable as being produced in geostationary orbit, you extend kilometers of cable both ``up'' and ``down''. The cable you extend up is to counterbalance the cable you extend down. Eventually you extrude enough cable that you can seat it on the ground, but its under no net-motion, literally magically hanging from the sky. THEN, you add in a weight on the outer-tip. centrifugal force means it'll now cause a net tension on the earth's surface, so if it were to break on the ground, it would pull up.

    If it breaks close to the surface, only the portion below the break will fall, the portion above the break will rise due to the inbalanced forces. (IE, since its not ``holding up'' so much weight, it will move outward until centrifugal forces are balanced.) If it breaks 10000km up, then you have a problem. :) If it breaks up in geostationary orbit, you have a BIG problem.



  • Span an ocean? Clarke orbit is 4 or 5 Earth radii from the surface...according to 2piR, that means that the cable would go all the way around the planet. Don't be on the equator when this happens.

    Terrorists did this at the end of Red Mars...what a COOL sequence in a COOL book. Moral of the story is: Don't break the space elevator.
  • Information might want to be free, but it's not ready to pay for the costs of producing itself yet in many cases. Get used to it. : )

  • The person who invents a method to produce industrial lengths of Buckytubes stands a very good chance of becoming the richest person on the planet. Rest assured, people are working on it.

    Not that money is everything...personally, providing an inexpensive route off this planet would be more than reward enough.

    It is definitly a solvable problem, and I'd be surprised if it isn't solved within the next five years.

  • The British sunday tabloids have a level of journalistic integrity that makes the Weekly World News look like the New York Times by comparison.

    Anonymous Coward, indeed.

  • Sir Authur has been using computers since the days of the Altair and CP/M. He has co-written books with Gentry Lee via e-mail. I've read text chats [scifi.com] with Clarke. He has mentioned that he uses the Net quite a bit in other interviews.

  • I can't see how you'd get those other than with nano- or organic assemblers...


    That's an idea... maybe I should abondon C++ and learn DNA, and make a tube-spewing organism.

  • The energy requirement to significantly change the orbit of a 10 km asteroid is roughly equivalent to what it takes to accelerate at least a few million people to the speed of light.

    I.e. infinite?

  • I would, but there are large parts of the world where this is not a practical suggestion.
  • The entire skyhook, which is rotating about the Earth's axis on the same 23 hour 56 minute sidereal schedule, is moving eastward and will keep moving eastward

    What I'm wondering is, would a skyhook have enough mass to alter the speed of the earth's rotation in any significant way? Would we have to build 2 hooks on opposite sides of the planet to counterbalance any wobble, or would they just not be massive enough to count...
    Your Working Boy,
  • Ok, technically, to a significant fraction of the speed of light. The calculation is pretty simple:

    Gravitational energy of asteroid = 1/2 M v^2
    where M = Volume * density.
    Volume = 4/3 * pi * (5 km)^3 (if the diameter is 10 km) = 5*10^11 m^3
    Density = roughly 4*10^3 kg/m^3
    so M = roughly 2*10^15 kg

    The size of this asteroid mass is what's important - it's enormous compared to anything we can handle with any remotely available technology today.

    If we can strap rockets to an asteroid like that and significantly change its orbit, we can certainly send a number of people roughly equivalent to that mass into space to fend for themselves. If each person weighs on average 100 kg and requires an extra 100 kg of luggage, that means that if we have the ability to move an asteroid that size, we also have the ability to put into space 10^13 or 10 trillion people.

    We'll be populating space in the billions long before we can move asteroids around much. And Clarke's point that we need to get into space to avoid our "single point of failure" here on this planet is very very important.
  • I attended a NASA space elevator workshop earlier this year, and I'd like to make a few comments. First of all, the cable hanging from synchronous orbit is not an optimum design. Large structures have to support all the load at each point. So a cable hanging down is smallest at the bottom, and each unit of length going up has to be an increment thicker to support the added weight of that length of cable. So as you go up the cable cross section gets exponentially bigger, because thicker cable in the higher sections add proportionately more load. Now consider a tower built up from the ground, using the same type of high strength materials as the cable would use. A tower will show the same type of exponential taper, but with the fat portion near the ground (i.e. it will look like the Eiffel Tower). For a minimum weight design, you would build a tower up from the ground and have it's top meet a cable hanging down from orbit. To put some numbers to it, assume you have 2 million psi carbon fiber of the buckytube flavor. A constant section strand 800 km long at one gee can just support it's own length. The physics of the situation says the cross section needs to increase by a factor of e (2.718..) every 800 km to keep from breaking. The earth's gravity well is the equivalent of 6400 km deep due to the fall off of gravity with height. So a cable hanging all the way from synchronous orbit, which is only 2% from the top of the gravity well, needs to be about e^8 times the mass of whatever you are lifting, or about 3000:1. If you have a tower and a cable, each e^4 times the cargo weight, then the combined weight is 110 times the cargo weight. This is a much simplified analysis. In the real world, you will have factors of safety and redundant design, overhead beyond a bare cable to deal with. Also, the tower, being close to the ground is presumably cheaper to build than the stuff in orbit. Finally, compressive and tension strengths for the same material are not the same. But the basic idea is that a cable all the way from orbit is not optimum. Secondly, buckytubes are presently made at a cost of $800/gram, a few grams at a time. Work is being done on scaling up production and bringing down cost. If it gets down in the range of $10/gram, people will start using it in places where weight is extremely critical (that's about the cost to launch things into space for example). Thirdly, long cables in orbit MUST be damage tolerant and have self-repair capabilities because man-made space junk and natural meteoroids WILL run into it. For example, you can have 6 main cables, any 4 of which can carry the load, with cross-straps every 10 km to re-distribute the load around a break. The cables need to be separated by more than the width of the widest thing that can run into it (think space station = 120 m wide). When a cable gets broken, a "repair spider" runs out to the break with a replacement spool of cable, winds in the broken pieces, and installs the new one. Fourthly, in the near term, a full up space elevator is not economic. Single-stage to orbit rockets are marginal on having payload (88% fuel, 10% structure, 2% payload). So anything you can do to relieve them of some of the rocket propulsion job can have a dramatic impact on payload capacity. So a tower going up from the ground in the range of 10-100 km (which can be done without buckytubes), and a cable in orbit to catch the rocket which is 100s of km long can help a lot, and can be done with existing carbon fibers.
  • That's actually a very good idea. I don't think IT jobs will go away in the future, but 20 years from now, biotech will be the place to be; the time to get there is NOW.
  • Hey,

    The account that Slash gives us seems to point to page, but not the one i was (we all are) looking for. Tried to find it in the archive but you seem to have to pay for it. Is there anyone that knows a working URL?

    -Rejo.
  • Cookies attached to ads don't work if you block the ads at your firewall ;-).
  • I'm afraid that bucky- structures are not exactly connected triangles of carbon. The buckyball would be a bunch of connected triangles, if nature hadn't cut off all of the tips and created those pentagons. What you end up with is a truncated icosahedron--better known as a soccer ball. This structure has the same symmetry group as the icosahedron [the triangles] but is instead made up of 20 hexagons and 12 pentagons.

    If you open any organic chemistry book, you'll notice that carbon seems to like to bond together in rings of 6, hexagons. Carbon seems to support hexagons, pentagons and heptagons with relative stability.
  • See, for example, Kim Stanley Robinson's Red Mars [amazon.com] epic hard-sf trilogy, which includes a description of the failure of a space elevator.

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