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Going Up? 567

Posted by michael
from the keep-arms-inside-the-car dept.
jmiyaku writes "The National Post is reporting that NASA has given a Seattle company a $570,000 grant to continue its investigation into constructing a space elevator. Coupled with some production-grade technology from a Japanese car company (carbon nanotube composites), this elevator could be a reality within 15 years..." The Highlift website has some more information.
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Going Up?

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  • Environmental impact (Score:2, Interesting)

    by lonely (32990)

    One thing that worries me about orbital towers is the impact on the weather and the local environment. Something that big must affect local rain patters in some way...


    Also what about the risk of it falling down? An orbital tower will wrap about the earth more than once if it falls. The description in Red Mars was particularly though provoking.

    • by barawn (25691) on Tuesday August 13, 2002 @09:42AM (#4060988) Homepage
      The Elevator in Red Mars fell down because it had an asteroid at the far end providing counterbalance. Separate the asteroid from the cable, and it's no longer a space elevator, but a really stupidly placed cable. Flop. Splat.

      The elevator they're proposing is not counterbalanced - this requires it to be even longer than if it wasn't counterbalanced, but it doesn't require a conveniently placed asteroid. :)

      Remember: you're asking what if it falls, right? It is falling. It just happens to be falling at exactly the same rate that the Earth is turning. It's in orbit. In order to make it fall, you'd need to break it.
      • The elevator they're proposing is not counterbalanced - this requires it to be even longer than if it wasn't counterbalanced, but it doesn't require a conveniently placed asteroid. :)

        Um, it's still counterbalanced - by the outer half of the cable. Cut the cable in the middle, and the bottom half goes "splat" just as effectively as if the counterweight was just a big rock.
        • Space elevators by definition are counterbalanced: what I was saying was that there wasn't a convenient break point, as in an asteroid-balanced one. It wouldn't be an issue - you'd need to break the cable, and that's a fundamental problem.

          If you can break the cable, then yes, all hell breaks loose.
          • by dbrutus (71639)
            Actually, if you break the cable then it flutters down like a newspaper dropped from the... damn, start over. ...like a newspaper dropped from the Sears Tower. In the site's FAQ list they address the problem and the biggest unknown seems to be whether it's going to disintigrate into powder and cause some people to have a breathing problem. It's ~23.5 lbs per mile of cable so it isn't going to cause a tidal wave or anything. It's light, it's chemically very stable, it's unlikely to cause problems and has a projected space lifetime of about a thousand years.


      • Yeah but imagine if the cable breaks in the middle,
        then 50,000 km of cable is going to hit the earth,
        and the remainder is going to fly off into space.

    • by Christopher Thomas (11717) on Tuesday August 13, 2002 @09:51AM (#4061043)
      Also what about the risk of it falling down? An orbital tower will wrap about the earth more than once if it falls. The description in Red Mars was particularly though provoking.

      I used to think that this would make space elevators impractically dangerous. However, this turns out not to be the case.

      The energy gained by the falling cable will be at most its gravitational potential energy, which is within a factor of two of conventional high explosives (per unit weight). Pick a maximum yield on impact, and you have a maximum cable weight. Use a thin enough cable to meet this weight restriction, and you have an adequately disaster-proof elevator (it'll make a mess, but not wreck the world's climate).

      My own calculations with a 10 kT yield/cable weight came up with something that could reasonably be used for space travel and would pay for itself if you could keep the cargo moving.

      The biggest problem is figuring out how to move cargo fast enough. I'd be leery of having induction motors mess with the cable itself, and if its a nanotube bundle they won't conduct in the right direction anyways. Winches are much too slow. Sheathing the cable with metal would only be practical for a very thin layer, which ends up being too thin to support the required currents without boiling off (I think). It's an interesting design problem.
      • The biggest problem is figuring out how to move cargo fast enough.

        I say use compressed air. Pressurize below the cargo and let it shoot up the elevator. You could use any power source you wanted to power the air compressors. And if that weren't enough, the elevator "car" could also have wheel-type-things, so that it could climb up the elevator.

        What are the chances that whatever the elevator was tied to out in space would throw Earth's orbit off, ever-so-slightly? Would this affect us in any major way?
      • multiple cables and counterweights?
      • by mberman (93546) <mberman@earth l i n g .net> on Tuesday August 13, 2002 @10:48AM (#4061443) Homepage
        According to the article, the power source is a laser shot from the platform, aimed at collectors on the bottom of the car. There, it's converted to electricity, and drives motors with wheels on the cable. Since intertia should keep the cable perfectly straight, it seems like a really good use of laser-powered propulsion.
        • by Enigma2175 (179646) on Tuesday August 13, 2002 @02:32PM (#4063260) Homepage Journal
          the power source is a laser shot from the platform, aimed at collectors on the bottom of the car. There, it's converted to electricity, and drives motors with wheels on the cable.

          That is an idiotic design. If you use conventional conductors in the cable, then we can also use the cable as a big powerline from space. We can have a large solar array in space and get the power back to earth via the elevator cable. Proposals in the past for powering earth from space have suggested using microwave transmission, the elevator cable would be a much safer alternative. In addition, if you have a powered cable you can use energy return brakes on the climber, so when it comes back down the motors function as generators, returning power to the system. With the aforementioned solar array, the elevator can be an energy producer rather than an energy consumer. Not to mention the fact that it is terribly inefficient to convert the electricity to light (laser) then back to electricity on the climber. It would be much more efficient to run power in the cable itself.

      • Cable safety is really a bugbear. The only part of the cable that will fall towards earth is the part below the point of breakage. In a worst case scenario, this is at Geosynch orbit. But what most people fail to realize is that as the cable falls it speeds up just like any other falling object. 60 or so Km up the cable is falling fast enough to burn up completely on reentry. So only 60 km or less of cable reaches the ground even in a worst case breakage scenario. The plan that highlift talks about puts it in the middle of the pacific ocean, convieniently 60 km or more from anything that might be damaged by a falling cable.
      • "The energy gained by the falling cable will be at most its gravitational potential energy,"

        Isn't that cute... but it's WRONG!

        The top of the cable has something much more powerful acting on it than gravity alone: the bottom of the cable. The top will be moving just as fast as the bottom, accellerating downward just as much as the bottom. So you have a miles-high structure coming towards the earth at a relatively steady 9.8 m/s/s. This is far worse than mere gravity alone.
      • The biggest problem is figuring out how to move cargo fast enough. I'd be leery of having induction motors mess with the cable itself, and if its a nanotube bundle they won't conduct in the right direction anyways. Winches are much too slow. Sheathing the cable with metal would only be practical for a very thin layer, which ends up being too thin to support the required currents without boiling off (I think). It's an interesting design problem.

        I got a solution: Use rocket engines. In fact, skip the cable and just use the rocket engines alone! I am sure scientists can find a way to keep them pointed stable enough for flight.

        Wait a minute......
  • by toupsie (88295) on Tuesday August 13, 2002 @09:31AM (#4060909) Homepage
    If you build it, they [muzak.com] will come...
  • Going up? (Score:3, Funny)

    by bokketies (584972) on Tuesday August 13, 2002 @09:32AM (#4060917) Journal
    I sure hope it can get you down as well.
    • Um, getting down from orbit has never posed many problems. We on Earth call that "falling" and the trick isn't getting down, it's getting down slow enough not to vaporize one's arse. In more serious terms, no, it's not likely that anyone will ever use the elevator to reenter Earth's atmosphere. Most likely, if anything needs to come back down in one piece, they'll lift a reentry module with the elevator and then let it drop with the precious payload the old fashioned way.

      Virg
      • Re:Think About It (Score:3, Interesting)

        by dbrutus (71639)
        Actually, I think it would be much more likely that loaded return trips would be made. Why haul around all that expensive re-entry weight when you have the perfect mechanism to come back down on the elevator itself. It's elegant, it's cheaper, and it's likely to be much less riskier than re-entry which can and has gone wrong in the past.
  • fifteen years? (Score:3, Interesting)

    by s20451 (410424) on Tuesday August 13, 2002 @09:34AM (#4060926) Journal
    According to this BBC article [bbc.co.uk] covering the same story, a fifty year timeline is more likely.
  • by pgpckt (312866) on Tuesday August 13, 2002 @09:35AM (#4060934) Homepage Journal

    Well, Yucca Mountain leaves a whole lot to be desired. I suppose the best thing to do would be to shoot the radioactive waste into the sun. You could lanuch self-guiding ships full of the stuff straight into the sun...the sun sure wouldn't care. But how do you get the stuff in space safely?

    Perhaps this space elevator? I think it should be safe(r). Use the elevator to take the radioactive waste top the space station, then build a craft to launch the waste into the sun. No more radioactive waste problem! And it would probably be cheaper than the current proposed solution, plus it would be really great for the space program and scientific development. Is this a good idea?


    • Also a good idea for getting rid of those annoying polititions/celebs etc.

      I think the sun was used for this in a Simpsons episode somewhere?!

    • by barawn (25691) on Tuesday August 13, 2002 @09:46AM (#4061010) Homepage
      It's not feasible to send waste into the sun - take a look through a few astronomy texts and you'll see why.

      Basically the problem is that any object we lift from the Earth has energy, and angular momentum. If you want to hit the sun, and not just put it in a very eccentric orbit, you need to remove a lot of energy from the object, and the space elevator wouldn't help - it pulls you out of Earth's gravity well, not out of Earth's orbit. You'd require massive amounts of fuel to get it there.
      • Why don't you take some of your own advice?

        Consider: we have to make the elevator extend past geosyncronous orbit (otherwise, what would be holding it up?) and connect it to a counterweight at the end. The smaller the counterweight, the farther it must extend. Now, if you are positioned at the counterweight, you are moving at supra-orbital velocity (your angular velocity is the same as it the angular velocity of something in geosynchronous orbit, but you are farther out. Also, tangential orbital velocity goes down as you go out.)

        Therefore, if you let go of the space elevator at the counterweight, you will continue on tangentially to the orbit of the counterweight, but you will be in a very eccentric Earth orbit. The space elevator's utility would be much reduced it the tangential speed at the counterweight was not escape velocity for the Earth, so we could (reasonably) assume that it would be greater.

        Now, if you release from the counterweight at just the right time, you will be heading in the opposite direction that the Earth is moving in, relative to the Sun. This means that you will be put in an eccentric orbit around the Sun, with your new perihelion much closer to the Sun than the Earth's.

        If the elevator is long enough, then no further action need be taken, otherwise, a retrograde (I think that's the word) burn immediatly after release from the elevator can bring the orbit into one that intersects the Sun. There are more or less energy efficient ways to do the burn, but the point is that you already have a good kick from the elevator.

        So, no you are not at all incorrect about the amount of energy requred--it takes a lot of energy to impact the Sun--but the elevator helps tremendously.

        • The counterweight's not being planned, for difficulty: they're doing it with a pure strand.

          The difference in tangential orbital vel. is minimal here: you're talking about the difference between the Earth's position wrt Sun, and the top of the Elevator's position wrt Sun. They're identical, as far as anyone cares: it's six orders of magnitude difference.

          But, anyway: figure it out. OK. Cable's 100,000 km long, right? That'll give you 7.3 km/sec let go at the highest point. You're right: that is a good fraction of the 30 km/sec needed to impact the Sun, but it's not all of it. And that remaining amount is just plain friggin' huge. You can figure out the amount that needs to be removed to hit the Sun (rather than direct impact) but it's still not going to be efficient.

          There's another problem here, though: the elevator is located at the equator, and it is not rotating in the same plane as the Earth is wrt the Sun. It's rotating 23.5 degrees wrt the ecliptic. So you'll build up 7 km/sec, but of course, a large fraction of that is out of the ecliptic, which doesn't help you at all: in fact, 40%! So really, the elevator only helps you out with ~ 4 km/sec against the 30 km/sec you're traveling. Plus now you're moving out of the ecliptic, so that additional 3 km/sec actually adds to the amount you need to get rid of, if only slightly.

          Bottom line: 26 km/sec vs. 30 km/sec: it still sucks.
      • It's not feasible to send waste into the sun - take a look through a few astronomy texts and you'll see why...You'd require massive amounts of fuel to get it there.

        Oh, no. There are some waste products that should only be desposed of in this way--whatever the cost. For example: Richard Simmons [richardsimmons.com]
      • It's not feasible to send waste into the sun - take a look through a few astronomy texts and you'll see why.
        Basically the problem is that any object we lift from the Earth has energy, and angular momentum. If you want to hit the sun, and not just put it in a very eccentric orbit, you need to remove a lot of energy from the object, and the space elevator wouldn't help - it pulls you out of Earth's gravity well, not out of Earth's orbit. You'd require massive amounts of fuel to get it there.
        You only need to slow it down enough for the orbit to decay. A very good way of doing so for practically free is to attach a solar sail to the garbage packet. The solar wind will then simply slow it down so that it's orbit decays sufficiently to eventually hit the Sun.
        • Correction: you don't mean solar wind. You mean light pressure. Solar wind is made of charged particles, which wouldn't work that well for the solar sail issue. Light pressure is better. But anyway...

          Light goes out radially: how would you slow it down using this? It's constantly pushing it outwards.

          I've always been confused about this: how exactly would you move radially inward against something that's moving radially outward? This isn't like sailing where you have something else to push against. I can't see anyway to get a net velocity inward.
    • by f00Dave (251755) on Tuesday August 13, 2002 @09:46AM (#4061011) Homepage
      The energy required to actually launch something 'into the Sun' from Earth is enormous. The Earth's orbital velocity is around 30 km/s, or 108000 km/h (~64800 mph). That's a LOT of delta-V to get rid of! I'll leave the details to the science geeks, but even with a gravitational slingshot (say off Venus), you're not gonna kill all that speed without entering atmosphere. The alternative would be to haul shit up to the graviational midpoint then let it slide along the shaft, accellerating and getting whipped off at 1G at the end of it, aiming it to smack into Jupiter or something, instead. ;-)

      That whole 'spiraling into the sun' thing bugs me.

      http://nssdc.gsfc.nasa.gov/planetary/factsheet/e ar thfact.html
    • The subducting seafloor idea sounds much better to me. Drop in into a hole in the ocean floor, and it is pushed into the mantle. No loss of mass for the earth, no huge expenditure of energy, and the waste is taken care of.

    • by cybercuzco (100904) on Tuesday August 13, 2002 @11:58AM (#4061941) Homepage Journal
      Were you aware that the sun is a Giant ball of radiation? Were you further aware that that electromagnetic RADAITON is bathing the earth every single day? Dangerous solar RADIATION is known to cause CANCER in human beings. Why would we want to add to that radiation by slinging nuclear waste into the sun? The sun is also an unstable environment, if that nuclear waste went critical it could explode with the force of thousands of hiroshimas, possible damaging the sun and causing more harmful RADIATION to be spread to earth.

      In case you couldnt tell, i was being sarcastic ;-)

  • Sheesh.. (Score:2, Funny)

    by mrgrey (319015)
    Think of how many times your ears would pop...
  • by prwood (7060) on Tuesday August 13, 2002 @09:36AM (#4060940) Homepage
    Fans of space elevators will of course recall Arthur C. Clarke's novel on the perils and political obstacles in the construction of such:

    Fountains of Paradise [amazon.com]
  • Elevator vs. Launch (Score:3, Interesting)

    by chaidawg (170956) on Tuesday August 13, 2002 @09:37AM (#4060943)
    Does it seem to anyone else that this is less like a space elevator and more of a really large launch facility? Clark envisioned a true elevator, with cars coming up and down. With this proposal explained as it is, you still have to worry about craft that can deal with reentry and landing, instead of a simple elevator ride down.
    • by barawn (25691)
      Yah, but reentry's easy! It's simply an issue of falling into a gravity well, rather than climbing out of it. You've got all that atmosphere to brake you down!

      Think about it, really: the Shuttle is really a very advanced glider on its downward trip - that's all you really need. I imagine you could probably send a few reentry gliders or capsules up the space elevator if you need to.

      Anyway, getting up is the important part. We've pretty much got the "getting down" part pretty down pat. Getting up's much harder. Once it's in place, you could start shuttling things upward to build a space station at the top, and then work on downward-bound cars.

      First step is to get off this rock. :)
    • I think realisticaly, the elevator has to deal with reentry anyway- the cable can get cut at any time because of micrometeorites. If you were on the way up at the time, then you would need the system to allow you to land safely from any altitude.
  • Peter F. Hamilton and it's AWESOME Night's Dawn Trilogy sci-fi epic has a space elevator - His goes up to the O'Neil Halo - a "space station" that circumvents the globe in geostationary orbit! See something of the tech here - High Brazil [nights-dawn.com] is one of them - they are towers that ascend the skies ;)
    Yes, of course, if you haven't read it - you simply MUST! ;)
  • Wouldn't it be easier to bridge the atlantic ocean than to build an elevator to space? Probably safer and more practical too.
    • Dear God no. We can get across the Atlantic ridiculously easy: boats, planes, anything. There's no need to bridge it, and even if you did, then you've got stability against wind, gravity, anything else. It'd be engineering hell, and you can probably work out that it's impossible.

      A space elevator is a cute idea: it's quite safe, since, well, it's in orbit. It just happens to be in orbit above one spot over the earth (geosynchronous) and really long, so that one side of it touches Earth. And practical? Man. Launch costs go from "huge" to "free". The world would change in a year after this thing being built. Seriously. It'd look like science fiction in no time: space hotels, lunar bases, Martian missions - everything becomes easy.
    • I refer you to A Transatlantic Tunnel, Hurrah!" [zetnet.co.uk] by Harry Harrison...
    • Wouldn't it be easier to bridge the atlantic ocean than to build an elevator to space? Probably safer and more practical too.

      Tunnelling under would be more practical.
  • Finally, something to put on the World Trade Center site.
  • by agilen (410830) on Tuesday August 13, 2002 @09:40AM (#4060970)
    http://www.highliftsystems.com/faq.html [highliftsystems.com]

    This talks about what will happen if it falls, what terrorists can do to it, etc. It actually seems fairly honestly done, not all marketing-speak.
    • Where did they find a place with no high winds, hurricanes, tornados, or lightning? And, with ocean front property? I think I want to live there.
    • This was an interesting FAQ. Now I think we should make predictions as to its location, based on what they described:

      • Unaffected by hurricanes
      • Receives little or no lightning
      • If it breaks, the lower portion falls into the ocean
      • The anchor station will be an unlikely target to terrorists due to its isolation
      • Not in the path of any existing launch "programs"
    • Several times they dodge the questions of weather by saying that they'll simply put it in a place where there are no hurricanes and no thunderstorms. While I don't doubt there are places where these are infrequent, I don't believe for a second that there is anywhere on Earth around the equator where it's impossible to run into bad weather.

      If I remember correctly, the reason they don't want to deal with the lightning question is because running a huge electrical charge through a carbon nanotube will make it explode into a cloud of graphite, severing the connection.

      So, the question becomes, what do they plan on doing when (not if) bad weather comes for the orbital elevator. Can it be moved?

      Another unanswered question is what they plan to do about space debris.
  • by brejc8 (223089)
    I think it was AC Clarke who said that it would be about $100 to get someone into space and about $50 for a return journey.
    This does blow your average $1 million for a five day rocket based space holiday out of the water.
  • I like space stories as much as the next person. However, this one reads like a company sales spiel more than a serious initiative. And everyone shoulds know what "within 10-20 years" really means, no? That's how much longer to fusion it's been for quite a few decades. And it's still 10-20 years from commercial applications.

    No matter, this nano-material they're plugging should be quite useful for a few real-life applications right now. If there's no "well, you see.." about it somewhere.
    • I thought nanotubes were discussed awhile ago and the consensus was that they couldn't easily be produced in significant quantities in a reasonable amount of time.
  • short circuit (Score:2, Interesting)

    I seem to remember someone commenting that a space elevator would act like a bridge between the ionosphere and the earth - Making a giant "short circuit" - does anyone have a link to the article that was posted?
    • Size and Composition (Score:3, Informative)

      by virg_mattes (230616)
      They covered this on the web site. It will carry a current, but it's in the range of milliwatts because of the size and makeup of the ribbon. The comment was based on using a cable (like an Earthbound elevator) and so doesn't really apply here.

      Virg
  • This idea originally came from NASA's institute for advanced concepts. [usra.edu]

    There are a lot of funky stuff going on there. But, here's the original space elevator paper [usra.edu]. I personally thought it was an interesting read.
  • ...and believe this will not be a problem but we are conducting studies to make sure this isn't a problem. Since we are aware of the possible problems now we can design the elevator to avoid these problems.

    Houston, I think we have a problem.

  • beam me up (Score:2, Funny)

    by crea5e (590098)

    "Scotty one to beam up."

    "I'm doing the best I can captain but the elevator is stuck on floor 3."
  • by Uttles (324447) <uttles&gmail,com> on Tuesday August 13, 2002 @09:50AM (#4061038) Homepage Journal
    Mr. Laine said the material, expected to be highly conductive and 30 times stronger than steel, is not yet in production...

    Highly Conductive... the article also states that they are looking for a region of the planet for the anchor where storms and high winds are uncommon. I'm not so sure this is going to eliminate any risks. It seems to me they are going to have to develop this thing so that it can withstand being struck by lightning many, many times. A perfect solution would be something that could actually store and use the power generated by multiple lightning strikes.

    My point is just that we don't really know everything about lightning, and just assuming that because there aren't many storms in the region the cable will not get struck doesn't seem smart to me. A highly conductive lightning rod extending into space seems to me something that would attract electricity, no matter what the weather conditions. I'm just picturing something like a Van de Graaf generator attracting all the loose electrons in the area. They need to develop the system so that it accepts lightning and other electric charges and distributes them somehow, causing no damage, even while cargo is in transit.
  • ...or wouldn't you have to locate the anchor point to be at a location that makes sense for the "drop off" point of the satellites to establish a useful orbit?

    Why wouldn't we have a bunch of satellites in the same planar orbit?

    I'm assuming that the elevator gives the sats a ride up, and then simply releases them. Is there another release mechanism that "points" the satellite in the right direction?

    Also, could you use the elevator for geosynchronous orbit birds?
    • If you release the satellite in orbit, then boosting it into another orbit is "cheap" compared to getting it up into orbit in the first place. Many satellites have booster rockets anyway to give them some maneuverability.
    • The real cost in orbital maneuvering is getting into orbit in the first place. If the lift cost goes from $10,000/kg to $100/kg, it would be worth it to get dropped off at a less convenient position, and adjust the orbit as needed. Remember, just because you used the elevator to get off Earth doesn't mean you have to leave the rockets at home. Hauling a bunch of attitude adjustment fuel wouldn't be a big deal at those cheap lift prices.

      For that matter, if getting the sats from the elevator to their proper orbits becomes a common problem, you could have a fleet of high-orbit unmanned vehicles whose sole job would be to take satellites off the elevator and ferry them to where the are supposed to go, more or less, and let the sats handle just their own fine tuning once they're in place.
  • Sounds great and all - but 15 years? Yeah right. I'm still waiting on flying cars, jetpacks, and robotic sex slaves. (Oh wait - I don't think that last one was on the Jetsons.)
  • $570,000???
    Isn't that a wee-bit expensive for a dog-eared copy of Fountains of Paradises ????
  • How will the elevator be funded?
    The elevator can be funded privately, publicly, or with a combination of the two.

    In other words "We don't know".

  • Charles Sheffield's novel _The Web Between Worlds_ is a fictional account of the construction of such a "beanstalk." It's strong on the science and is a pretty good read.
  • From their website,
    For the initial space elevator these recurring costs combined with repaying the initial capital investment would give us total launch costs of $100/kg ($230/lb or 1/10 to 1/100 of conventional systems)
    So it's $100/kg, which works out to $230/lb. I see... looks like the same math that caused a recent failed mars mission.
  • Many /. readers seem to think of the catastrophical fall of the space elevator cable in the 'Red Mars' novel.
    The book described the cable as being 10m in diameter. I always thought of this being ludicrous.
    Look at the FAQ. It talks about a ribbon 1cm wide.
    • Mhmm - the width seems to vary quite a bit.
      It's only 1cm wide below 10km altitute.

      "The ribbon of our proposed 20,000 kg capacity elevator will have a 2 square millimeter cross-sectional area, be 1 meter wide and microns thick on average."
  • Mechanical climbers, powered by an electric motor, would scale the ribbon, hauling the cargo thousands of kilometres before catapulting the payload, which could include anything from satellites to human passengers, to its destination.

    NASA must be obsessed with catapults [uncoveror.com]. Every plan they come out with seems to make use of one in some way.
  • by Tickenest (544722) on Tuesday August 13, 2002 @10:48AM (#4061445) Homepage Journal
    Man, can you imagine how much time and money would be wasted the first time you get a jackass who pushes all the floor buttons on this puppy right as he's getting off?
  • I don't buy it (Score:3, Interesting)

    by khendron (225184) on Tuesday August 13, 2002 @10:52AM (#4061468) Homepage
    I LOVE the idea of a space elevator. Reading "Fountain's of Paradise" is what got me into the engineering field in the first place.

    However, I still do not buy the argument that getting into space will cost virtually nothing once a space elevator is built. Sure, in pure energy, the costs are low. But what about the entire support infrastructure?

    Right not it would cost me about $100 to take the train from Ottawa to Toronto, a 4 hour trip. With a space elevator we are talking about a trip 100 times farther and 50 times longer. Applying some hand waving math, we would be looking at $10K to $20K for a trip up the elevator. Maintenance costs for the elevator are going to be a *lot* more than those for a strip of train track, so it would not be unreasonable to multiple this estimate by a factor of 10.

    Yes, that is a lot less than $1,000,000 but also far from virtually nothing.
  • by ldopa1 (465624) on Tuesday August 13, 2002 @11:33AM (#4061768) Homepage Journal
    The space elevator has been featured in a lot of books, most recently David Gerrold's [amazon.com] "Jumping off the Planet" [amazon.com].

    This is a great idea, but it has one big problem. It isn't energy - The idea of generating energy by dangling something into the atmosphere from space has been explored and proven that it will work [nasa.gov].

    The problem is this: With every gram of matter you chuck into space (or even lift from the surface), the rotation of the Earth slows in direct proportion to the cargo's mass relative to the mass of the Earth. In other words, every time we throw something in to space,the Earth will slow down just a bit, no matter how small the load. Proving yet again that there's no such thing as a free lunch.

    Fine, you say. It'll take a TREMENDOUS amount of mass to be lifted into space to stop the rotation of the Earth. I completely agree. However, if the Earth slows .000001%, (about 9 hundredths of a second, enough to win/lose a car race) then the days will get measurably longer unless we bring an equal amount of mass down.

    Just to sate your curiosity, the earth weighs about 5.98 X 10^24 kilograms (or, 5,980,000,000,000,000,000,000 tons, metric, roughly speaking. Source. [enchantedlearning.com]). That said, it would just take us lifting 59,800,000,000,000 trillion tons into space to affect the aforementioned change. Again, a tremendous amount, right?

    Consider this: New York city alone produces 13,000 tons of residential waste a DAY, and they've run out of places to put it (Again, Source [fathom.com]). That's 4.7 Million tons a year. And they're currently paying PA to dump is for them. There are other cities with the same problem. Exactly how long do you think it will take for someone to decide to move the waste even farther away? Like Space? And that's just residential.

    That's only one example. Let's add Yucca Mountain's 77,000 Metric tons of waste and 100,000,000 gallons of high level radioactive waste water (Call Claire at the Yucca Mountain Project (dept. of civilian radioactive waste mgmt. for more info -Link [ymp.gov] or 1-(800) 225-6972). Okay, lets add the "extra" garbage of all of the other states, countries, provinces etc who have run out of places to put their waste. It adds up REALLY quickly.

    And that's not including the actual mass of the elevator itself, including it's anchor.

    Mind you, I still think we should build it, I just don't think we should use it as a tool to get rid of our problems that's we're too stupid to fix, but smart enough to move out of sight.
    • 59,800,000,000,000 trillion tons into space to affect the aforementioned change. Again, a tremendous amount, right?

      Well, yes, actually.

      Consider this: New York city alone produces 13,000 tons of residential waste a DAY, and they've run out of places to put it (Again, Source [fathom.com])... It adds up REALLY quickly.

      You're using your intuition, and it's wrong, wrong, wrong.

      It doesn't add up. Assume everyone in the world produces as much trash as a New Yorker City resident, and that we double that for non-residental, and that we send all of the trash in the world into space.

      That's 13K*(1/.002)*2= 13 million tons of trash a day. To achieve the slowdown you mention (.1 second/day) would take about 1.2*10^16 years. Tidal effects are slowing the earth much faster than that. More to the point, the sun will have blown up by then, making the rotation of the earth moot. Hell, I'm not sure all our protons won't have decayed by then - anybody know the numbers on that one?

    • Sigh... it's the old "we are running out of space for garbage" myth again.

      Just a nit in this discussion, but there is not any problem at all in terms of space for waste. I forget the figures, but basically you could put all the waste generated in the US for a century into a spot something like 10mi x 10mi. I live in the middle of a desert where the nearest large city outside of the one I live in (Phoenix) is 120 miles away! LOTS of room for rubbish. For that matter, we have huge retired open pit copper mines around here. We can use the rubbish to restore the scenery (although open pit mines are pretty cool to look at, and the Arizona town of Bisbee is built in one).

      Other than that, I'm glad at least someone did the math so I didn't have to.

  • by Guppy06 (410832) on Tuesday August 13, 2002 @11:39AM (#4061813)
    Everytime this has come up on Slashdot I've posted how foolish an idea this is (especially after 9/11), but nobody seems to listen to me.

    1.) If it falls, bad things will happen. As I type this there are probably at least 10 posts to this article moderated way up that point out how "safe" this thing would be coming down. Every single one has two flaws:
    • It treats the beanstalk as a series of point particles as opposed to one connected strand
    • It neglects the fact that gravity is stronger towards the bottom of the beanstalk than the top
    What does this mean? It means that, as the bottom comes down, the top will be yanked down faster than it would be by gravity alone. Want an analogy? Extend a tape measure to its full length. Let go and let it wind itself back up. Try not to cut your hand. And you want to build this on a large scale?

    2.) People will now respond to this post saying that it won't fall down because the top will be in orbit. In order to keep the bottom of the beanstalk from whipping around the circumference of the earth every 90 minutes, you must be talking about putting the center of gravity into geostationary orbit. I've done the math. If you want to put the center of gravity of a cable with uniform density into geostationary orbit, it puts the top of your beanstalk well beyond lunar orbit (inverse square againt). And when the moon snaps off that top guess what happens.

    To sum up: Not on my planet!
  • by MattJ (14813) on Tuesday August 13, 2002 @11:51AM (#4061896) Homepage
    Highlift Systems is sponsoring a two-day conference (Space Elevator Conference 2002) at the Seattle Sheraton, ending today. See http://www.confcon.com/sp_elev_02/sp_elev_02.html . I Googled to get the location details, here [confcon.com].

    And yes, ny the way, they had a dinner last night at the Space Needle :-)

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