Space Elevators: Low Cost Ticket to GEO? 429
Crocuta writes "The current issue of Science
News features a cover story
that discusses the current developments in space elevator technology. NASA has been
working on such devices for many years, but private companies such as Highlift Systems are now jumping on the space
elevator bandwagon, no doubt seeing the huge potential profit in a low cost per pound
delivery system. PhysicsWeb has a somewhat
older, but much more technical article
on the formation and structure of the carbon nanotubes that form the basis of the proposed
tether cables. With a development like this, we could shoot entire boy bands into space and make
the world a better place."
Repeat? (Score:1, Insightful)
I've said it before (Score:3, Insightful)
ok but (Score:1, Insightful)
Re:I've said it before (Score:3, Insightful)
Yeah, yeah, the shuttle is reusable, but disposable rockets are actually cheaper than that engineering nightmare, from what I read...
We'll never fund it (Score:4, Insightful)
The idea might be feasible -- I prefer the idea of a giant cannon/mass driver/gauss gun to shoot us into space myself -- but the idea of a 100,000km tube supporting an elevator is too farfetched to ever get funding, especially with increasingly conservative US administrations that would rather spend money launching rockets not into space, but into third-world cities, as well as European powers that have their own budget problems due to their social welfare systems that prefer to spend money on Earth and not in space.
Re:GET SOME PRIORITIES! (Score:3, Insightful)
The universe is a big scary place; we won't have the pleasure fully discovering this if we crawl under our beds and hide.
So when to elevator tickets go on sale?
Risky investment (Score:3, Insightful)
How many gazillion of billions do you think it will cost. If not by any accident, how many terrorists does it take to blow it up? There just is not and cannot be such big amount of capital tied into one physical place. It might be possible to build it - once, if you find someone who is ready to BURN that money. Someone who invested all his money into a dot.com in 1999 is worth economics nobel prize compared to this.
Re:another use for it... (Score:2, Insightful)
Re:Risky investment (Score:4, Insightful)
Erlang (Score:0, Insightful)
If the system software were written in Erlang, that won't be a problem.
Of course, those kitten-fucking pigs'll use Java, dooming millions to an icy grave in the sky...
Elevator + Orion = Fun! (Score:3, Insightful)
Once the elevator is built, use it to haul pieces of an Orion craft to the top and assemble it there. When it's ready, let it go, flinging it out of Earth's magnetic field. Once clear, light it up and go see the solar system.
This way there's no radioactive contamination of the atmosphere, minimal risk while getting the "fuel" in orbit, and it's a handy way to get a crapload of plutonium out of our hair.
Saturn in fifteen years, anyone?
Re:Free Electricity (Score:2, Insightful)
Re:ok but (Score:2, Insightful)
The people on board the elevator at the time might argue with that statement... :-/
Repopularizing space travel (Score:4, Insightful)
The entire space program has been gradually fading from world view, and particularly from the Western world. Yes, there are programs still going on at NASA and ESA and even in China, but it's nowhere near what was hoped for in the 1960s and 70s. Putting a high profile celebrity into space would bring a lot of attention back to the space program. Would it be fleeting? Of course. That's what media attention is nowadays. But it would probably enspire a lot young kids to go to space, just as the early US and Soviet astro/cosmonauts did nearly half a century ago.
Re:I knew it (Score:2, Insightful)
Why it can't work (repair delay, debris, current) (Score:5, Insightful)
How unrealistic can an analogy be? If a crack forms in some remote stretch of interstate, there's no danger of the rest of the interstate system suddenly ripping away and falling into space. Repairs would have to happen instantaneously without ever breaking an almost unimaginable ribbon tension. And this wouldn't be a very rare occurrence, either, as the ribbon would present a surface area of five to eleven million square meters on each side (5 to 11.5 cm wide, 10^8 meters long). And remember that it's on the equator, which every piece of orbiting debris crosses twice during each orbit.
And the only mentioned solution for lightning strikes (one of which could be fatal to the ribbon) seems almost totally unworkable, and doesn't take into account that a 100,000-kilometer-high conductive tower would generate its own lightning. Remember the ill-fated (but educational) Space Tether Experiment [nasa.gov]? And the tether was only a mile long. A space elevator's ribbon would intersect a huge chord of Earth's magnetic field, including both Van Allen Belts. Seems to me that, even if the ribbon didn't immediately blow like a giant flash-bulb filament, you still couldn't get within a hundred yards of the base due to the continuous electrical discharge.
Don't get me wrong--I've dreamed about space elevators since I was a kid reading about Clarke's hyperfilaments, but the more I think about it, the more unworkable it seems.
Re:Risky investment (Score:5, Insightful)
That said, however, putting a ribbon to space out in the middle of the ocean, away from any shipping lanes, international flight paths, or human activity at all is a good start at protection. It's HARD to get to a location that far removed from everything without anyone noticing (especially if that location is under constant watch and guard.
Additionally, this operation, while not devoid of human workers, won't have so many people laboring at the anchor-station or on the cable to make a terrorist attack really that fruitful. There just isn't that much casualty potential (although the capital losses could be considerable).
But capital is just money. And the neat thing about money is if you spend it on projects which create wealth, you're not really losing it. If the cable can operate for a few years, it will have paid for itself, anyway, and very likely several additional cables will be built to expand capacity. These cables will most likely expand radially from earth all around the equator, under the control of diverse groups of people. We already know that humans want to get out into space and explore it, even at considerable expense. The proposed budget for the cable is not chump change, but nor is it unreasonable when compared to other space projects. America alone has spent considerably more on the Space Shuttle program over the past 25 years, and for that money, we'd be able to lift up as much material (measured by tonnage) in 2-3 years as we have in all the Shuttle missions combined. So the real risk of huge financial loss is if a terrorist destroys the cable in that initial timeframe. Additionally, since most of the cost is in the research, design and development, rather than the construction and deployment, another cable could be built if the first one is destroyed (admittedly, if the first one is destroyed very quickly, there will be a huge political barrier to overcome before a second cable could be deployed).
Also, since the thing is so cheap to operate, many more nations, companies, and individuals will be able to afford to undertake space-based projects.
The thing is, if the whole world is given access to space, There won't be that much motivation to destroy the means to that access. If one country or company jealously hordes the cable and doesn't lease out usage to everyone else, that country or company will:
1. Risk considerable reprisal, both in the form of economic sanctions by the rest of the world, possible military threats, and very likely terrorist threats
2: Miss out on a fantastic opportunity to enhance the economy of the entire planet, and line its own pockets considerably in the process.
Therefore, it will be in the interest of whoever builds such a machine to let the rest of the world use it as well, including the deployment of components for the construction of additional cables.
Microscopic != Macroscopic (Score:5, Insightful)
Re:Why it can't work (repair delay, debris, curren (Score:5, Insightful)
So yes, there are many challenges to overcome, but they all, fortunately, seem surmountable.
Re:Oh great, one more reason for Bush to intervene (Score:2, Insightful)
Re:I knew it (Score:5, Insightful)
This is just impossible! :)
But seriously, I did read it. Well, really just the section about nanotubes, and if the rest of the paper is equally fallacious, I think that would serve as pretty conclusive evidence of the imposibility of the space elevator. Using a combination of an overestimate of the strength of nanotubes with an underestimate of their density, the author uses a strength/mass ratio that is twice as large as the UPPER bound on the strength of nanotubes (which is the ideal strength). In practice the ideal tensile strength is typically many times higher than the yield strength. In case you're wondering, this is based on density functional calculations I performed myself--far better than the crude estimates refered to in the paper. And yes, I did just check his source [sigmaxi.org]. It's a review paper that refers to an extrapolation of a strength based on a strain from a tight-binding molecular dynamics calculation which the authors recommend taking with a grain of salt.
On the experimental side, noone has yet (to my knowledge) produced a composite based on nanotubes which is actually particularly strong. Even if these composites are developed (and probably eventually nanotube composites will surpas carbon fiber composites), they are guaranteed to pay a major hit in strength/mass due to the mass of the epoxy. Look for more like a factor of two over carbon fiber composites, rather than the factor of 50 or so advertised.
As mentioned in the paper, the mass of cabling needed is extremely sensitive to the strength/mass ratio. I don't know the relation (since I haven't looked up the Pearson paper), but he mentions that if you diminish the strength/mass ratio by a factor of 50 (using kevlar) from his fictitious nanotube ratio, the mass goes up by about a factor of 100,000. With an overestimate of the strength of nanotubes of at least a factor of two, probably much more, it seems highly unlikely that the cost of the elevator (already estimated to be rather high) will be within reason, and for all I know there may similar "rounding up" going on in the rest of the paper.
Will not scale... (Score:2, Insightful)
That said, I can't get behind this space elevator push. First, the economics of it won't scale to meet a wide range of demand fluctuations. What if you build it and then find out that demand for it is only a tenth of what you had predicted? There's no way to scale down the sunk costs involved--it's an all or nothing sort of proposition.
Second, it would represent a prime terrorist target. No set of defensive systems could hope to cover against every possible means of attack. Missiles, bombs, lasers, and who knows what else. And we haven't even covered the subject of action by a hostile nation-state, which could presumably marshall far more impressive resources to the task of bringing down a cable.
Third, it represents completely unproven technology. Better to go with a multistage rocketplane or some variation on that theme. Design one that can be built with the equivalent of off-the-shelf parts and build it with a multi-purpose role. A launch vehicle that could also effectively double as a system for high-speed transoceanic delivery would have great commercial and military applications, and would be developed that much more quickly and economically.
In short, the space elevator is a nifty idea in many respects, but it won't happen until the construction of such a system is relatively trivial. When one business guy turns to another and says: "You know, we're paying a lot of money for pilots for our launch vehicles. Maybe we should just build an elevator and get some high school kids to run it."
Energy (Score:3, Insightful)
Comment removed (Score:5, Insightful)
Re:GET SOME PRIORITIES! (Score:2, Insightful)
Re:Actually, he's right... (Score:4, Insightful)
So of course, this being Slashdot, I get flamed and modded down by geniuses who don't know a fucking winking smiley when they see one.
Sigh... well, not like it matters. Excellent minus 2 is still Excellent, in all probability. And if not, well, it still doesn't matter.