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A Space Elevator for Real?
I saw a report on space.com recently describing what appear to be real
consideration of a space elevator, using carbon nanotube technology to get enough strenth for the cable. Obviously it's still an "out there" notion, but this article seemed to have a lot more seriousness than others I've seen discussing the concept. Does anyone here know anything more about this? Thanks, Kip |
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A Space Elevator for Real?
Kip Ingram wrote:
I saw a report on space.com recently describing what appear to be real consideration of a space elevator, using carbon nanotube technology to get enough strenth for the cable. Obviously it's still an "out there" notion, but this article seemed to have a lot more seriousness than others I've seen discussing the concept. Does anyone here know anything more about this? It's based on work by Dr. Brad Edwards, now of ISR (Institute for Scientific Research, Inc., a West Virginia think tank) that was funded by NIAC (NASA Institute for Advanced Concepts). The intent was to develop a space elevator design that could be built in the near term (nominally 15 years) and be at least competitive with existing launchers for current markets (i.e., not require huge increases in space activity to be practical). The basic design is a 100,000 km by 1-meter by 1-micron-thick ribbon of carbon-nanotube composite fibers, mass around 80 tons, with a 20 ton load capacity. The "climbers" use simple friction drive (treads clamped around the ribbon) to go up the ribbon at 200 km/hr, taking about a week to reach GEO. Climbers are powered by laser power beaming from the ground, and are 7 tons empty (13 ton payload). The ribbon is "bootstrapped" -- an initial few-cm ribbon is deployed down from GEO, and small (initially 1-ton) climbers carrying ribbon spools widen the initial ribbon until it reaches full width. The ribbon is anchored on a floating platform in the Pacific, which among other things allows the bottom of the ribbon to be moved to dodge LEO satellites as needed. It's a very interesting concept, but has (not surprisingly) lots of practical problems. Some are addressed in Edwards' NIAC reports (see www.niac.usra.edu) and a book he put out (search Bradley C. Edwards on Amazon) but work on the concept is still at a very early stage. The most fundamental issue is whether carbon nanotube (CNT) composites will actually achieve the required tensile strength -- individual nanotubes are strong enough (upwards of 150 GPa tensile strength) but it's not clear if it will be possible to make long cables with a large fraction of the raw-nanotube strength to weight; the baseline cable design assumes ~60 GPa cable strength. If the CNT materials work(and they probably will get close enough to make an elevator possible, though perhaps not with the performance Edwards assumed) then there are a bunch of other things to worry about -- collisions with LEO satellites and meteoroids, dynamic stability, ribbon wear, etc., etc. Many fun Ph.D. theses to be had.... There was just a workshop on the subject (which is what prompted the flurry of press articles); you can see the presentations at http://www.isr.us/spaceelevatorconference/presentations.html (There's even one by me; I didn't plan to talk at the conference, but I objected to some of the economic estimates in another talk and got challenged to do better, so I literally put a talk together overnight.) Jordin -- Jordin Kare "Point and click" means you're out of ammo. |
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A Space Elevator for Real?
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#4
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A Space Elevator for Real?
In article ,
Mister Sharkey wrote: The basic design is a 100,000 km by 1-meter by 1-micron-thick ribbon of carbon-nanotube composite fibers... In the reports I have read, the designs always call for a ribbon of carbon nanotubes. Why a ribbon, and not a cylindrical cable? Would a ribbon be stronger, or easier for the climbers to climb, or what? The ribbon is less likely to be cut completely by a small debris hit. Multiple cables with cross-connections would be even better, but much more complicated. Also, don't overlook the problem of how the climbers get traction on the cable. A cylindrical cable with the same cross-section would be only about a millimeter in diameter. A wide flat ribbon is much easier to climb. -- MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer pointing, 10 Sept; first science, early Oct; all well. | |
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