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Scientist Sees Space Elevator in 15 Years
bofh31337 writes "Scientist Bradley C. Edwards, head of the space elevator project at the Institute for Scientific Research, thinks an elevator that climbs 62,000 miles into space could be operating in 15 years. He pegs the cost at $10 billion, a pittance compared with other space endeavors. 'It's not new physics--nothing new has to be discovered, nothing new has to be invented from scratch,' he says. 'If there are delays in budget or delays in whatever, it could stretch, but 15 years is a realistic estimate for when we could have one up.' NASA already has given more than $500,000 to study the idea, and Congress has earmarked $2.5 million more."
...Nobody but you can hear the elevator music
And consequently, nobody can hear you scream.
It would be cool if it didn't suck.
I've read quite a few posts about "riding the space elevator." I'm under the impression (and yes, I RTFA) that the space elevator would be solely used to send cargo up to space. Astronauts would still get up to the ISS by conventional means, and then the space elevator would just be a cheap[er] way to get supplies up to them without worrying about sending up rockets. Unless I missed something, humans wouldn't be travelling on this space elevator at all.
Some folks think it's a typo, that it's supposed to be 65 miles, not 65K miles. No, 65K miles is more like it. You really want your elevator's center of mass to be in geosynchronous orbit... Space elevators to LEO tend to, uh, get wound around the earth right fast.
And if the ribbon breaks, things generally aren't so bad. The portion of the elevator (including the counter weight) that's further from the earth will tend to move away from the earth. (If you spin in a circle with a rock in your hand, then let go of the rock, the rock goes away from you, not crashing in towards your head.) The nearer part will tend to fall, but it will tend to fall slowly and is relatively unlikely to cause damage. (At least, according to High lift systems, who came and gave a talk last year.) The elevator, since it's so huge, tends to not be terribly heavy. The system proposed by high lift systems
I believe Brad Edwards was involved in High Lift Systems, so I imagine the basic idea is the same.
If geo is ~20K miles, why does the elevator need to be so long? Does this mean that they're now thinking about a lighter counter weight? They used to talk about capturing an asteroid.
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I did some more research on this and found the following:
e di a/s/sp/space_elevator.html
The concept of the space elevator first appeared in 1895 when a Russian scientist named Konstantin Tsiolkovsky was inspired by the Eiffel Tower in Paris to consider a tower that reached all the way into space. He imagined placing a "celestial castle" at the end of a spindle-shaped cable, with the "castle" orbiting Earth in a geosynchronous orbit (i.e. the castle would remain over the same spot on Earth's surface). The tower would be built from the ground up to an altitude of 35,800 kilometers (geostationary orbit). Comments from Nikola Tesla are suggestive that he may have also conceived such a tower. His notes were sent behind the Iron Curtain after his death.
http://www.campusprogram.com/reference/en/wikip
This is a vital technology but...3 ft Pipelines (say 36" X65), mere steel steel shells say 1/3 to 1 inch thick, usually cost (usually way over) over $1 million / mile on terra firma. Not to mention how much super carbon fiber rod(nearly solid 3ft??), flying it up, joining in place. Try some multiple of $100 billion at least. $10b sounds like someone's "too cheap to meter" on nuclear power 50+ yrs ago. We got "nuked" financially.
No, it's not the only problem remaining. There are a ton of nanotube problems left, and there's some doubt that they even attain the sort of >100GPa tensile strength that Edwards' design requires (one test measuring actual SWNTs put the strongest ones in the test at around 60GPa (MWNTs have tested higher, but they're not applicable due to mass)).
Then there's the "fiber" problem. Nanotube fibers are at best held together by Van der Waals force. Edwards proposes some sort of unexplained "nanotube epoxy" that is somehow supposed to be able to withstand these incredible tensile strengths which the tubes themselves, even in theory, can barely withstand. I don't buy it one bit. The best fibers made so far, held together by the same forces, achieve the sort of tensile strength you get from Kevlar. Longer tubes will help, but you'd need a *huge* improvement.
The epoxy concept is bunk. There is a concept which might work, however: pressure induced interlinking of carbon nanotubes. Basically, you swap out some of the stronger sp2 bonds for the weaker sp3 bonds, but it interlinks the tubes.
I have other problems with Edwards' design, too, but he has done an awful lot of well-reasoned calculations. I contributed a lot to the article on Wikipedia, so if you want to read more about space elevators, that's the place.
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Have you read about what this system is like first?
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Wikipedia has a good explanation on 'The Van Allen Belt's Impact on the space elevator'.
As far as I understand it (from the recent Discover article), once the ribbon is initially deployed (starts out small), they send up small lifters that build onto the main ribbon, increasing its width. These initial lifters would park at the end of the cable forever, increasing the size of the counterweight. They claim that the initial ribbon would take about 2 years to build to full width with this method. Additional ribbons could be constructed in 7 months each, for MUCH less cost... after all, they can use the first elevator to start the construction, instead of sending the initial materials up on big tanks of burning rocket fuel.
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First off, it's not nearly so simple. Since the space elevator is tapered (in fact, a non-tapered elevator is essentially impossible around Earth), there is a weak point near Earth; this is your bottleneck. As soon as a craft passes the bottleneck, you can launch another; with Edwards' design, that's every 3-4 days. The entire trip is about 8 days.
Edwards' proposal *is* an up-only design, which I complained about on the message board (getting people out of orbit, while easier than in, is still quite dangerous and uses significant fuel). You can't just fire a little rocket to get out of orbit there (although you could slowly decelerate things with ion drives; wouldn't be too great of a solution for people, though).
There are plenty of ways for elevators to pass each other at high speeds when you're past the bottleneck; there are even more if you ditch the "flat ribbon held with rollers" concept and go to a "mesh" design, which can be climbed with teeth from one side only and has better resiliancy . If you allow down-climbing elevators, and keep your elevator size small to enable fast launches, energy recovered can be transferred to up-climbers, cutting down on the energy expense for the up-climbers (which makes up most of the cost, since power beaming is quite inefficient).
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When, exactly, did the production of steel on a scale that one could build a bridge out of the stuff begin? Iron, too, for that matter? Certainly not thousands of years ago.
Furthermore, it was mostly the math that needed improvement, not the materials.
You see, we've done this before... You know, the "monument of engineering in somebody else's country" thing? So where do we build this thingy along the equator??
Actually the plan isn't to build it in any country. The proposal is to use a floating platform converted from an oil drilling rig. There's a lot more suitable ocean than land, and an ocean platform could be best situated for good weather, and even moved a bit to dodge larger bits of debris. A platform out in the middle of the open ocean would also be less accessible to terrorists.