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NASA Space Science

Space Elevator Conference Prompts Lofty Questions 212

Posted by timothy
from the put-the-new-toys-on-the-credit-card dept.
itwbennett writes "Even the most ardent enthusiasts gathered at the annual Space Elevator Conference on Friday don't expect it to be built anytime soon, but that doesn't stop them from dreaming, planning, and trying to solve some of the more vexing problems. One of the trickiest questions is who's going to pay for the operational costs when an elevator is eventually built. 'It's been nine years we've been looking for someone' to study that, said Bryan Laubscher, one of the leading space elevator enthusiasts and principle at Odysseus Technologies, a company working on high-strength materials."
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Space Elevator Conference Prompts Lofty Questions

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  • Or build a skyhook (Score:3, Interesting)

    by MichaelSmith (789609) on Saturday August 13, 2011 @11:32PM (#37082734) Homepage Journal

    It needs to be strong but nanotubes aren't required. You make a cable about 1000 km long. It has fittings on both ends which vehicles can attach themselves to. It orbits slightly more than 500 km above the ground and rotates its its axis horizontal and at 90 degrees to its orbit. The length and orbital altitude and chosen so that when one end almost reaches the ground it has a low velocity, while the other end is above escape velocity. You use it to exchange mass between the surface of the Earth and a trajectory which will take you to other planets. A dead mass can be sent down to Earth and a vehicle carrying passengers and supplies can be sent the other way.

    • by hedwards (940851)

      The idea is tantamount to expecting to go to the moon by pulling on your own boot straps.

      In order for it to work, you'd need to have some energy source to resist the pull of the item you're wanting to lift into space. And by the time you start sending rockets up with fuel to do that, you might as well just use rockets to send the payload into orbit because it's much more efficient.

      • by physicsphairy (720718) on Sunday August 14, 2011 @02:15AM (#37083228) Homepage

        Well, one idea is that you catch random orbiting junk at the other end, replenishing the lost momentum. In any case, efficiency isn't particularly important. The major limitation on getting things into space right now is construction, launch logistics, etc. If we could somehow be continuously sending things into space, it would be well-worth having to send two or three times the fuel along with.

      • by Urkki (668283)

        The idea is tantamount to expecting to go to the moon by pulling on your own boot straps.

        In order for it to work, you'd need to have some energy source to resist the pull of the item you're wanting to lift into space. And by the time you start sending rockets up with fuel to do that, you might as well just use rockets to send the payload into orbit because it's much more efficient.

        There's power aplenty at the orbit, so just use ion or plasma propulsion, and send stuff up at frequency that matches the average lift generated. The amount of propellant sent up will be a tiny fraction of what current chemical rockets need to get a single kilogram to orbit. And if more capacity, more frequent lifts, are needed, then just strap on more engines, and/or send more stuff down to earth.

        • Or how about this simple way of doing things :

          Orbits come in many sizes. Orbits close to geostationary orbits have the following properties :
          if you are slightly closer to earth, you will fall down (slowly)
          if you are at the exact right spot, you will stay there
          if you are slightly further away from earth, you are in effect on an escape trajectory, you will gain height (slowly)

          So here's an idea. Since this cable has to withstand umpteen giganewtons of tension anyway, place the top of the elevator too high. The

    • by strack (1051390)
      thats a stupid idea. the sheer drag as it plows through the atmosphere repeatedly means itll last only a few orbits, if that. even if the speed was low, the drag would still be large enough to bring it down quickly. and anything you sling into orbit is gonna pull the entire thing down, so your gonna need the same, probably more, thrust to bring it back to that 500km orbit than youd spend just blasting a rocket with that payload on the same trajectory.
      • by 0123456 (636235)

        thats a stupid idea. the sheer drag as it plows through the atmosphere repeatedly means itll last only a few orbits, if that.

        I'm not entirely convinced. If you rotate it at the correct speed it could have zero velocity relative to Earth at the bottom of the swing and you could pick the orbit so that it picked up payloads in thin air (of course getting the payloads onto something that's rotating like that would be tricky).

      • Say you use it to send mass to the moon. For every 1000kg of food, fuel and people you send up, you send down 1100kg of lunar rock. This shifts the the centre of gravity of the rotating tether to a higher altitude every time two payloads are exchanged. Each end of the tether drops down to 10 or 20 km altitude, and at a low speed. Its motion relative to the ground would be mostly vertical. The amount of energy lost on each rotation would be fairly small and could be offset by importing rock from places outsi

    • Sadly, since a skyhook is not attached to the earth, it misses one of the key advantages of a space elevator: the earth itself supplying the necessary angular momentum. For an elevator, only potential energy must be supplied, and that rapidly gets cheaper the further up you go. Past geo-synchronous orbit it is entirely free, but velocity still increases linearly with height. (Keep in mind that the kinetic energy is proportional to the square of the velocity; paying for that energy directly is very expens

    • by IrquiM (471313)
      The weight of that cable sort of kills your idea before it starts....
      • Why? It only has to support itself against centrifugal forces and the gravitational gradient along its length. It could be assembled in orbit from smaller lengths of cable.

    • It needs to be strong but nanotubes aren't required. You make a cable about 1000 km long.

      What's it going to be built out of, then? Nobody's ever build a 1000km long anything, much less a something that can support its own weight in Earth's gravity field.

  • Even the most ardent enthusiasts gathered at the annual Space Elevator Conference on Friday don't expect it to be built anytime soon

    Considering that the engineers who will design and build the elevator first need the scientists to figure out the physics and chemistry of the materials required that is a pretty good perspective.

  • The article suspects a space elevator could be built for $18 Billion? And they're worried about doing a study to explore who will pay for it? That much money is budget dust for any major country. Once the technology is there, I'm sure Boeing or Bechtel will be more than happy to take taxpayer money to work on the project and "create jobs."

    • Re: (Score:3, Informative)

      by Anonymous Coward

      That number is way lowballed. What, are they thinking the price of the nanotube cable is comparable to the market price of carbon?

      Anyone dumb enough to pay to build a space elevator this early in the game will lose their money.

      Seriously, it's an elevator from the ground to one point in geosynchronous orbit. A payload released at almost any other altitude will need reaction mass to establish a stable orbit, most of which will be expended in the direction of the cable and thus wear it down. (The exceptions ar

    • AC below has key points, but I am responding to you in a different vein.

      I'll let you have your 18 billion to build it, but it's the "leading edge" of another 100 billion in support industries. "A Cable to lift what? To where?"

    • The article suspects a space elevator could be built for $18 Billion? And they're worried about doing a study to explore who will pay for it? That much money is budget dust for any major country. Once the technology is there, I'm sure Boeing or Bechtel will be more than happy to take taxpayer money to work on the project and "create jobs."

      Sure, the Yanks could borrow some more money from China.

  • by JoshuaZ (1134087) on Saturday August 13, 2011 @11:53PM (#37082814) Homepage
    Anyone interested in this issue should read the NIAC report http://www.spaceelevator.com/docs/521Edwards.pdf [spaceelevator.com] which discusses the issues in detail and the technical problems. Space elevators would make space travel much cheaper. But the technical issues are immense. The NIAC report carefully outlines the major issues and how they might be handled. We would need to make extremely high quality carbon nanotubes at an immense scale. We also would need to put into space a structure orders of magnitude larger than anything we've put in space. Indeed, a space elevator would be one of the largest physical structures ever made by humans. And the engineering hurdles, such as the problems of wind in the lower atmosphere, are massive. But there's nothing about the idea that is physically impossible. The primary issues are issues of scale. And the issues are being worked on. Right now, there's a lot of work on making carbon nanotubes of high quality in a large scale. Since such nanotubes would have many different applications there's a lot of funding for that and that will likely be extremely beneficial to humanity well before it scales up to anything near that needed for a space elevator. Since the nanotube manufacturing is the primary technical hurdle, this is a good thing. I doubt we will see a space elevator in my lifetime, but maybe my children, or their children, will see it. And on that thing ribbon, space travel will finally become as cheap as so many have envisioned it.
    • by JoshuaZ (1134087)

      And on that thing ribbon

      Ugh. Need to pay more attention to preview. Replace "thing" with "thin".

    • Space elevators would make space travel much cheaper. But the technical issues are immense.

      We can't honestly say the first part without having a bit more of a clue about the second.

  • by mbone (558574) on Sunday August 14, 2011 @12:37AM (#37082936)

    One of the interesting things about this conference (which I attended) is that nanoscience researchers on Friday reported substantial improvements in the ability to make carbon nanotubes. They can now "grow" 1 cm nanotube mats, which can be spun into fibers. This is a substantial improvement from even 1 year ago.

    I still think that a terrestrial space elevator is a decade out, but this year has convinced me that it is coming much faster than a lot of people think.

    • by AGMW (594303)

      I still think that a terrestrial space elevator is a decade out, but this year has convinced me that it is coming much faster than a lot of people think.

      If we actually return to the moon, might a space elevator be more practical there? Could we do that now?
      What about Mars ... how close are we to using a SE there?

      • by vlm (69642)

        If we actually return to the moon, might a space elevator be more practical there? Could we do that now?

        There's a whole wikipedia article on the topic, but in summary, a lunar elevator would be off the shelf. Not off the shelf at your local home depot, but more like Aircraft Spruce and Specialty. Not kidding, I checked their website and they sell kevlar49 spools at about ten cents per foot for 7100 denier.

        It would be fun to try on a "smaller" asteroid. Then literally hardware store products would be good enough plus the operational training would be priceless.

  • Since it will be shared infrastructure like our roads, the public should retain ownership rather than some for-profit corporation, and the contractors we hire to build it should be thus paid with a tax or bond. Of course the same should have been done with telecom infrastructure (and then we'd have true neutrality of the wires).

    • by macraig (621737)

      ... and queue the Libertarian rant in 5... 4... 3... 2....

    • by vux984 (928602)

      I agree. But in the real world even crucial regular bridges are being built by for-profit corporations ... for profit.

      • by macraig (621737)

        That's what happens when there's no Eisenhower figure to step up and generate consensus. Yeah, people thought Obama was gonna be that type of figure, but it's not happening. (Eisenhower was a Republican, though perhaps Republicans were less cartoonish back then and acknowledged that taxes and "socialization" were practical for some things.)

        • by 0123456 (636235)

          Eisenhower was a Republican, though perhaps Republicans were less cartoonish back then and acknowledged that taxes and "socialization" were practical for some things.

          No, they just hadn't seen clear proof back then of what a disaster socialist policies always are in the long term.

          • Yeah, sure. Them there socialists are out to get you. Be afraid, good citizen, be afraid, there's them there socialist boogeymen in your closet! I just stay in my European socialist hellhole and enjoy life. The US were on the road to third-world status when I worked there in the early 2000s - go ahead and slide further in to your banana republic mode, you seem to enjoy it. I just pity the decent guys over there. But hey, if you want to get out - i got two large sofas in the living room - ample space for a
          • by sgt scrub (869860)

            All of the AAA countries have a socialist party. Socialism is to Capitalism what a Republic is to a Democracy, balance. If our founding fathers would have placed that balance into the constitution we would be in a much better place.

  • by iamacat (583406) on Sunday August 14, 2011 @01:32AM (#37083080)

    Our lack of progress in space exploration has more to do with losing the will than limitations of technology. We could have launched a mission to Alpha Centauri by now if we pursued project Orion with modern advances to material science and optimized computer control of propulsion. If we are not doing that, who is to say we will build a space elevator even if the technology is feasible?

    • by Ambvai (1106941)

      Which reminds me of a story I came across once-- it was basically the journal of an explorer who left Earth to some distant system with the intent to beam information back and start the colonization of the universe. Turns out, when he [and the rest of the crew] got there, space travel had advanced so much that he was welcomed as an artifact that only historians cared about while his trip amounted to nothing more than a footnote in the history books. (Plus a little extra human interest about his wife and kid

    • by Arlet (29997)

      We could have launched a mission to Alpha Centauri by now if we pursued project Orion

      I don't think the plans for project Orion involved slowing down at the destination, so it would be a rather pointless exercise of zipping through the Alpha Centauri system at 0.03 c, and hopefully taking a few blurry pictures of a planet before entering interstellar space again.

    • by loufoque (1400831)

      The reason we're not doing is that nuclear scares people.
      Nuclear power plants are being closed and replaced by burning more oil as we speak.

  • by John.P.Jones (601028) on Sunday August 14, 2011 @01:40AM (#37083100)

    I was thinking about how the energy of chemical rockets is just barely sufficient (given fuel mass) to make chemical rockets that can escape Earth's gravity well. I'm not sure of the exact headroom but my understanding is that it is fairly tight. From what I have read on the strength of nanotubes, they too are theoretically just strong enough to barely make a space elevator a possibility (if we could manage to weave them into a macro-fiber without significant losses.) If this turns out to be the case I wonder if there is a connection between these two methods and the strength of chemical bonds to overcome the gravitational potential of our planet. Need it be so that these two very different ways of utilizing bond strength achieve a similar maximum gravitational field that they can overcome? And even more speculatively could the fact that the gravitational field of the Earth is near this value be important in the suitability of it to life?

    • by UCSCTek (806902)

      That's quite the stretch.

      Naively, I would say the important comparison is between the scale of thermal energy available on Earth to organic bond strengths. I don't see gravity being a large issue.

    • Now there is an interesting coefficient to add to the Drake equation. Also, another one would be too much gravity to leave their plant so many fewer hot rods of the gods.
  • http://en.wikipedia.org/wiki/Launch_loop [wikipedia.org] Launch loops are basically a big cable, supported magnetically in a vacuum sheath, and accelerated up to high speeds (14km/s+), it could be set up as a 2000km long track along the ground, about 80km up. Since it's moving faster than escape velocity, it would appear to move away from the ground, since the ground is curving away from it faster than it's moving. so it would just need to be tethered to put it into a nice flat path, and could be magnetically looped aro

  • It would be a nice to have at least one elevator on the planet where that button worked.
  • by mattr (78516) <mattr@teleb[ ].com ['ody' in gap]> on Sunday August 14, 2011 @04:52AM (#37083724) Homepage Journal

    The Japan Space Elevator Association (http://www.jsea.jp in Japanese) in addition to covering technical and engineering also considers business and legal issues. And here [youtube.com] is a video from JSETEC 2011 shot in Fujinomiya City, Shizuoka Prefecture on August 7 showing a climber built by Takane Matsumoto of Team Aquarius. Certainly it's cool that something like his climber exists! I don't know how high it went but I think they were going for 600m altitude. Anyway I expect these groups would welcome anybody who wanted to investigate building a loop instead.

  • by mattr (78516)

    OP says nobody is thinking about costs. However the Japan Space Elevator Association (http://www.jsea.jp in Japanese) in addition to covering technical and engineering also considers business and legal issues. Their site says they are the only group to cover legal.
    I once attended a meeting of theirs and a manager from a leading aerospace company was in charge. Their website also mentions someone's estimate of about 200M USD to build a megafloater island not counting cost of the station and elevator itself.

    F

  • So the questions are: can you have 6 climbers on a ribbon instead of 3?

    Seriously, those are the questions? So I guess they have a ribbon that allows 1 climber already then?

    How about REAL questions:

    1. What is the maximum carbon fiber ribbon length can you even make with current technologies? What is the longest length of ribbon that can be made that will support its own weight with current tech?

    2. What is the climate and weather going to do to the ribbon? Rain? Thunderstorm? Tornado? Hail? Even all the Sun l

    • by mbone (558574)

      1. What is the maximum carbon fiber ribbon length can you even make with current technologies? What is the longest length of ribbon that can be made that will support its own weight with current tech?

      About an inch right now, but it can be spun. No one thinks that the SE will have 100,000 long nanotubes - they will be centimeters long. Each bond is fairly weak, but the # of bonds increase with length and so short tubes can be bonded together. The real question is, how long do the fibers have to be to have a

  • This is not just putting a cable in orbit. Consider a long list of stability problems [newscientist.com] inherent to any project of this type. Everything from Harmonic vibration, to Coriolis effect, to shear from solar winds and complex interactions with the ionosphere. It might take a month to lift a cable car safely. Okay for raw materials, not so great for people or perishables.

    Also imagine you have a 45,000 mile long antenna that extends out into the solar wind. Can you imagine the kind of voltages and currents that this

  • Won't we have to worry about rats? The high up they live, the larger!

Computers are unreliable, but humans are even more unreliable. Any system which depends on human reliability is unreliable. -- Gilb

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