space elevators, again

Wired hypothesizes (without anything to back it up, really) that the Shuttle disaster might spur development of a space elevator:

Meanwhile Time follows the money and delivers some scathing (and, I think, fairly well deserved) criticism to the shuttle and ISS programs:

Space elevators are super cool. I babbled on about them in an April journal entry:

Folks are claiming that a space elevator could be built for $10B, which is just under twice NASA's current annual manned spaceflight budget. For that, you can lift to orbit for $100/Kg instead of $40,000/Kg.

Tags: ,

25 Responses:

  1. babysimon says:

    Folks are claiming that a space elevator could be built for $10B, which is just under twice NASA's current annual manned spaceflight budget.

    I admit to not having read the links you posted, but I thought we were several advances in materials science away from building one at all, never mind for the super-bargain price of $10B. That's only twice as expensive as the Jubilee Line Extension!

    That price looks incredibly optimistic. If only it were true...

    • naturalborn says:

      That price does look incredibly optimistic. And I haven't seen any studies of how to get the inevitable resonance under control, or how difficult it would be to move the necessary asteroid into place, or how nasty the obvious failure mode of it getting dropped onto earth would be, or what a mining operation on the moon would be like - the structure couldn't possibly be lifted from earth, it would have to be lowered from space, which involves constructing it somewhere up there...

  2. mattbot says:

    How many Airbus and/or Boeing hits does 200 gigapascals of tensile strength give you? As a registered Affront to God (TM) this thing will need some security. Easier than a pipeline I guess. So do you like your third world hell holes in African or South American? Afghanistan required only a $1B down payment with an addition $2B over a 4 year contract so lots are relatively cheap. It's buyer's market.

    • internebbish says:

      Oh man, I so agree with this.
      From what I remember the space elevator concept 20+ years ago, it would make the WTC disaster look like a champagne bubble.

      Imagine if you will, a couple of 747s hit thestructure. Not only does the thing collapse but you have the top part swinging around wildly in the sky as the system struggles to maintain geonsynchronous orbit. Occaisionally, the world's largest swizzle stick takes out a mountain or a chunk of chicago.

      And then there are the aforementioned harmonics if you get a nice storm going in the area you'd get a sequel to the Tacoma Narrow's bridge.

      • unabomber says:

        This happened in that Red Mars/Blue Mars/Green Mars sci-fi series, and the collapsed elevator fell onto the surface and wrapped around the planet twice. It's fairly good fiction reading if you're into the whole idea, though. Of course, they did this like 100 years from now, and it was easy to say "we just used nanotechnology!" and leave it at that.

        -FC

        • forthdude says:

          Man, those were some frustrating novels... I hate them! There'd be some really cool bits (like the aforementioned collapsing space elevator or the fuel-air bomb in the domed crater) and then vast tracts of boring prose. I couldn't even finish Blue Mars. If the whole book was bad then I wouldn't care so much.

        • jwz says:

          Man, I hated that book. The only reason I even made it all the way to the end was that I was having a really hard time sleeping, and that book was a very strong sedative. That book managed to bore me to unconsciousness while describing: the settlement and terraforming of Mars; creation of an immortality drug; revolution against Earth; the construction of a space elevator; and the destruction of the elevator.

          I mean, how is that even possible? You'd have to go out of your way to make those boring. Well, he did.

          • unabomber says:

            It's probably no surprise that Kim Stanley Robinson's favorite band is Yes.

            I didn't make it to the end of the *Mars trilogy - I gave up somewhere in the middle of Blue, when it turned into a droning political monologue. It is amazing that he managed to create objects and situations that still stick in my mind very vividly, and then manged to intersperse them with about 1000 pages of a geology textbook.

            -FC

  3. rpkrajewski says:

    I was especially appalled when I read that NASA cancelled cheaper unmanned programs at the expense of the shuttle. The real test of our system is if anybody investigating this tragedy is going to be able to take on the entrenched interests that are risking lives and holding back a better way to explore space.

    • atakra says:

      Or how about how the *news* that the tiles could have been made out of a stronger metal-based alternative, but how that was scrapped because the funding to NASA had been capped after the Challenger explosion?

      • rpkrajewski says:

        Yep.

        Of course, even newer materials cost money. If "we" want safe manned flights, we're going to have to pay for them. My guess is that NASA's budget would have to double just for safety and upgrading the shuttle technology, assuming that it's prudent to even keep the shuttles running at all.

        Here's another good article that questions the shuttle:

        http://slate.msn.com/id/2078104/

  4. atakra says:

    Just like 'Bubblegum Crisis'?
    Well then I also want mutant rampaging robots in my future.

    SOON!

  5. Take the yield strenght of your favorite unobtainium alloy, divide by the density of your alloy, and a suitably reduced value of gravity, and find the max height of your structure.

    No matter what material you use, you're not going to get anywhere near the geosynchronos layer, which is where you need to be for this to work.

    You could drop a kevlar string from the top, but I still don't think it'll work.

    space elevators fail the freshman physics napkin analysis

    • jwz says:

      It only needs to be in geosynchronous orbit if you want it to attach to the ground. It can be in a lower orbit, meaning the whole tether orbits the earth (while standing "upright.") You dock to the bottom end with a high flying plane, and then your payload gets a cheap ride to the top. Once you're at the top, orbital insertion is "just let go." That also means the elevator is way less tall. Here's one page that describe this, calling it a skyhook.

      The stuff about how to make the tether resiliant against impacts is pretty interesting, too.

      • mattbot says:

        Yeah, but it's not like it's a free ride. How many tether shots until the Earth grinds to a halt?

        I wonder how the tenthers handle reentry on the satelite deorbiting device? Do they break up or comedown in 5km long firey strands? That would be something to see.

        The radiation belt herding tenthers sound fascinating too. This could pave the way to long-term space habitats and improve low orbit spacecraft service life tremendously. This is the first time I've ever heard a suggestion about handling the radiation problem besides adding more shielding. Would long range radio communication be improved as a side effect?

        Do you know how much interest is growing for such technology within the space community? I've spoken to a couple electrical propultion engineers and it seems like launch technology isn't seen as an interesting area, it being so rocket-centric currently. There isn't much funding in alternatives that I've read about and aerospace engineers have to follow the cash. The private sector and the military will be making the call on this one while NASA is out of the game. And the military seems more interested in sub-orbital craft these days from what I read.

      • ciphergoth says:

        Oh, that is a top idea. Nice.

        The affordable spaceflight people want to combine this with a "spaceplane" for the first hop. I wonder if a "space gun" might be a viable alternative? I guess it's much easier for a plane to dock with the lower end of the elevator than a gun-launched projectile.

        http://www.astronautix.com/lvfam/gunnched.htm

      • If you wanted a "just let go" orbital insertion of your payload, you couldn't let go at the top of the tether, but rather at the middle, as it's the middle (CG) that's in orbit. The top moves too fast and the bottom moves too slow.

        That's the lead-in the the problem of a free-orbit tether. Let's consider what we save when driving up the tether: The energy needed to bring a payload of P kilos up M meters, and accellerate it to K km/sec (rotationally around the earth). Let's call this X.

        Here's the problem: Since the gravitational potential of the payload-tether system stays constant during ascension, when you bring the payload up, you are pulling the tether down a tiny bit. You add X energy to the payload only by taking away X from the gravitational potential of the tether.

        We can't just let the tether fall, because even with the most efficient utilization, you won't get more than the mass of the tether itself lifted over the lifetime of the tether. Since that's the case, the rocket-power used to lift the tether itself would be better spent lifting the payloads meant for the tether.

        Thus, after you push something up with the tether, the tether goes down, and we need to push the tether back up again. To do this, we'd need ... rockets. The same ammount of rocket power, possibly more, than it would take to lift the payload by itself.

        Or, an alternate explanation: Imagine the orbiting tether, CG at orbit height and velocity. Now, tie something to the bottom end. The system as a whole is now in a slightly decaying object, whether the payload is at the top, at the bottom, or in the middle. What would it take to ke

        • jwz says:

          Yeah, you have to push energy into the tether to keep it up while liftin, and all the sites I linked to talked about ways to do this. Mostly they didn't mention rockets at all, because they're more wasteful than other ways. The sites tended to talk about various kinds of electrical propulsion, either ion engines or pushing against the Earth's magnetic fieild, with power coming from solar generation at the top end of the tether. (One site suggested putting a solar sail at the top, but that sounds kind of sketchy to me.)

          So you can say "you ought to be just spending that thrust on the payload itself", but it's pretty hard to get payload out of the atmosphere using those kinds of techniques without a giant structure there to begin with. That's like saying "instead of using a block and tackle to lift that piano, you might as well just lift it straight up."

          Also, you get to reclaim the energy of things going down the tether. Presumably more mass will always be going up than down, but at least you're not throwing all that energy away. There's a lot of it.

          • None of the sites you linked to were for designs where the tether was to lift anywhere near a significant multiple of it's own mass over it's own lifetime - mostly shuttle-borne or similar stuff.

            Ion engines on the end might be a good idea 30 years out, but not now - while they have good lifetime energy output/weight ratio, they're not that great on power/weight. Since you need a good deal of power just to overcome atmospheric resistance of the bottom end, only a tiny ammount of surplus power will be available for relifting - and that surplus power, over time, is your payload capacity, over time.

            I think that given current materials technology and propulsion technology means we'll be doing the oxidation-in-metal tube style of lifting in earth/space launches for a long time yet (20 years is my guess)

        • Or, an alternate explanation: Imagine the orbiting tether, CG at orbit height and velocity. Now, tie something to the bottom end. The system as a whole is now in a slightly decaying object, whether the payload is at the top, at the bottom, or in the middle. What would it take to keep the whole system in orbit? A rocket at the bottom, capable of pushing up the weight of the payload for the time the payload is on the tether.

          A rocket capable of launching the payload by itself, basically. You're launching hundreds of thousands of kilos of tether (or space shuttle and skyhook) with the additional lifting potential of maybe tens of thousands of kilos.

          A further problem with the non-anchored tether is rotational velocity. In order for the tether to be orbiting earth slow enough that even the fastest airplanes (SR-71-style) can can grab on to it, the CG will need to be near... the geosynchronous layer, just like the anchored tether.

          The other solution is to fly the plane the opposite direction around the earth as the tether is orbiting, but trying to grab a tether at an orbital rotational velocity is about as hard as shooting down ICBM's in space - and that's before you get to the "hanging on to the tether bit" and resolving the problems in the relative velocity.

          The nice thing about the ground-anchored tether is raises itself back up after it's used, because of the centripetal force on the counterweight above geosynch. We're stealing a little bit of the energy stored in the Earth's rotation. Every launch will lenghthen the day infinitesimally.

  6. phygelus says:

    Funny how "progessive" liberals (the author of that Time piece is a senior editor of the New Republic and a visiting fellow of the Brookings Institution) are putting the not-so-new "man was not meant to fly" spin on the Columbia accident.

    Expect to hear lots of arguments in favor of (oxymoronic) unmanned space "exploration" from the electric car (Can you imagine "The Road Warrior" with electric cars?) crowd in the coming months.

    The most important long-term purpose of space exploration is to have people living on other worlds, so that knowledge is multiply insured against catastrophe.

    Phygelus

  7. fo0bar says:

    Why is the space elevator docked with the death star?

  8. I read somewhere that carbon nanotubes like the ones the Wired article talks about have a tendency to explode when exposed to bright light. Oops!

    • cirollo says:

      It's not really an "explosion"... you can watch a video of it for yourself.

      This has been observed only in certain types of single-walled nanotubes. Multi-walled nanotubes, C60 (buckyballs), etc don't ignite from light flashes.

      Nanotubes and such do tend to conduct electricity fairly well. It would be really interesting to think about what would happen to have a conducting wire connecting the earth to the upper atmosphere. Think about the guys who shoot off tethered rockets in order to induce lightning strikes.

      The potential difference between the ground and upper atmosphere is somewhere in the neighborhood of 400,000 volts! I'm fairly certain that you would get so much current flowing that any wire would be immediately vaporized.

      *reaches for a pen and some napkins*

  9. I'm confused (and not a scientist) -- what powers this elevator?

    Wouldn't it take a massive amount of energy to get it up the tether and out of our atmosphere?