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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."
And you thought that the CN Tower was a long elevator ride. I wonder how long it would take to go that far into space in an elevator? Would there be in-elevator movies and food service?
There would need to be. At any reasonable speed, you're looking at a 24 to 48 hour trip.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
The current issue of Discover magizine has a much longer and more informative writeup.
And I think he means 62,000 miles. 62 Miles is only the boundary of space. What would the point of finishing there be? The reason he says 62,000 is because it covers everything useful in space travel, from Low earth orbit up past geosynchronous orbit.
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No, it *is* 62000 miles. The tether has to be that long to allow a suitable anchor to be attached at the other end and keep the right amount of tension on it. Or something. /not rocket scientist, but mightily impressed at this bloody good idea.
Brian Smith "Jokers and aces, bruisy and blackfern" - Steve Kilbey, Day of the Dead.
Uhhm, even in his book, Edwards admits that the carbon nanotubes needed to make this work just aren't there yet; while we can manufacture nanotubes now, we can't make them as strong (by a factor of around 100) or nearly as long (by a factor of 10,000 or more) as needed. While it may well be that, as soon as someone really puts some effort/research bucks into making stronger/longer nanotubes, they will happen, but it seems like 15 years might still be optimistic.
OTOH, this would be way cool, and maybe in my lifetime to boot...
"I'm a scientist! I don't think, I observe!" - Dr. Clayton Forrester
NASA says geosynchronous orbit is 36000 km = 22000 miles. I think the 62000 miles part must be so the centrifugal force keeps the cable taut. You could build a solid tower up to 62 miles, but a cable-elevator just wouldn't work at that distance.
Well, "3001" wasn't published until 1996. He wrote "The Fountains of Paradise", another book about a space elevator, in 1978. But, at any rate, sci-fi authors rarely think up these things themselves. Instead, they generally get their ideas from journals and contacts in the scientific community. For example, one of my college CS professors is friends with Greg Bear, and helped him with background material for a couple novels.
Better RTFA, and maybe do a little research. We are actually within a factor of two of having materials strong enough; anything after that becomes essentially an engineering problem.
...phil
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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'.
I think the idea for this is using the elevators to lift the mass up to an appropriate altitude and letting it go. Part of the mass is a booster rocket to get the mass into the appropriate orbit. It'd take a whole hell of a lot less rocket fuel to do this than to launch it directly from Earth's surface. Taking the mass to an altitude above geosynch and letting it go would give it a huge boost for getting out of Earth's gravity well. As far as efficiency, they are planning on driving these things with lasers powered by solar cells. I forget the exact details, but they imply that the propulsion systems are one of the easier components to develop for the project.
IIRC, the main rebuttal for this is that the cable will be much wider than the minimum required for the target maximum liftable mass, and that there will be "repair lifters" that go up on occasion to patch holes in the ribbon cable. For the larger, trackable space junk masses, the cable will be tied down to a mobile oil rig platform to allow for evasive maneuvers.
Above geosynch orbit altitude, masses "moving" (quoted because it depends on your reference frame) at the speed at which the weighted end would be moving tend to want to leave orbit. Put simply, things trying to maintain synchronous orbit (staying over one spot) below geosynch altitude want to fall (not moving fast enough), things at geosynch altitude stay where they are (speed is just right), and things above goesynch altitude want to leave orbit (moving too fast). For example, the moon's orbital speed is 1.03km/s (about 2200 mph, or about Mach 3), performing one revolution every ~28 days. The speed of something maintaining a geosynch orbit at 60k miles would be insanely fast, revolving once a day (at that altitude, it would be moving at ~7.5km/s). That would put a lot of stress (not sure how to calculate that) on the ribbon, which is part of the reason it needs to be so strong. The centripetal force would keep the cable taut. The weighted end would be quite massive, enough that the relatively small mass of the lifter and its cargo wouldn't cause enough of a change in mass to the elevator system as a whole.
Also, if the cable were to be in danger of getting dragged down, they'd probably just let it go, and the weighted end would rip the ribbon out into orbit and away. I don't think they are too worried about it getting dragged down, based on the designs I've read about.
The article in the recent Discover goes into more depth than the article attached to this thread... it even goes so far as to claim that many of the scientists that attend these conferences end up signing on to help the Space Elevator along towards being realized.
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NASA already has given more than $500,000 to study the idea...
That's not all that much money at NASA, it's the equivalent of 2 Full Time Equivalents (FTEs), plus a little bit of equipment to work with.
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.