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Nanotubes Start to Show their Promise
Rei writes "Researchers at the University of Texas at Dallas have developed the highest quality nanotube sheets to date (the team previously set strength records with polymer-nanotube composites). Producable at a rate comparable to commercial wool spinning, the transparent cloth has exceedingly high conductivity, flexibility, has huge surface area to volume ratios, can potentially be made into very effective OLEDs and thin-film photovoltaic cells, and outperforms even our best bulk materials (such as Mylar and Kevlar) at strength normalized to weight. It strongly absorbs microwaves for localized heating (leading to applications in seamless microwave welding of sections and even windshield warming), changes conductivity little over a wide temperature range (very useful in sensors), and is expected to be used in commercial applications very soon. The research should even be expandable to artificial muscles! To head people off, while the exact tensile strength is not listed, it sounds like it is still far from the >100 GPa needed for a space elevator. Anyways, here's to process advancements!"
...the cost?
I know tfa says that it will be efficient, but does that take the cost into perspective? It's not unusual to hear about a new idea that is totally ground braking in several fields, then the research on the commercial fades out, because they find out that it's too pricey. A lot of products was that way in the beginning. Just look at LCD screens etc.
Well. That being said. This sound awesome, I'd like to see it developed...
Scully: Should we arrest David Copperfield?
Mulder: Yes we should, but not for this.
on that page was the urine powered battery.... Now that could useful. Drink a few beers and power your laptop.
If it strongly absorbs microwaves, I wonder about its potential as a radar-absorbing material for stealth military aircraft, leadfoot driver's cars, etc.
If this stuff is so resilient, NASA should really research a coating of it over the Shuttle tank foam that keeps falling off.
Artifical Intelligience is no match for natural stupidity.
I remember a meeting of the Chicago Society for Space Settlement* at the Adler Planetarium back in 1978 where space elevators were discussed. Even back then, they knew that carbon-fibers were about the only material that could potentially be strong enough.
It's taken a very long time to get here (I was just a kid at the time), and I pretty much have always dismissed the idea of space elevators, but it's kinda neat to see that the concept is evolving along the same vein as over two decades ago.
*(CSSS merged with the L5 society in the early 1980's.)
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
This month's IEEE Spectrum features an article by Bradley Edwards who studied the near-term feasibility of a space elevator under a grant from NASA. His conclusion is that it could be accomplished in as little as 10-15 years and for as "little" as $10B (meaning little enough that there are several individuals on Earth who could fund it privately). Of course, the major technological limitation is the nanotubes. He suggests "spun" nanotubes (like yarn) or nanotube composites (and he contends that if one of these broke near the top, it would not be the end of life as we know it -- it's a ribbon that would loft gently down to Earth and burn up in the atmosphere). He even addresses storms, terrorism and space-borne threates. It's a good article and somewhat technical (written for engineers). His conclusions are quite credible, and probably more informed than your average Slashdot debate.
Today's Sesame Street was brought to you by the number e.
Edwards declares two as "preferable", one exclusively up and the other exclusively down, and provides no means for power exchange between them. He also doesn't study down climbers, which have different requirements (braking and dissipating the braking energy, plus different strains on the tether)
There is a big difference between an up-only cable and an up-down cable - up-down allows for easy energy exchange, better utilization of cable bearing strength, and lower capital costs (than two separate cables), but needs to be a small amount larger, is slightly harder to build, and most significantly, requires many launches of small elevators instead of few launches of large elevators for effective power exchange.
To understand why having both up and down utilize the tether better, picture the strains on each part of the tether if you have one starting at the bottom and the other starting at the top. Start the one on the top first - once it has enough acceleration to go without pulling on the tether, start the bottom one. They pass each other at a point less than 0.5g. The one that was at GEO lands on earth braking slowly while the other elevator largely drifts, and once it touches down, the Earth elevator brakes as fast as it wants to and arrives at GEO.
You'll notice that these two elevators could be carrying a full payload, and put little more stress on the tether than just an up-only climber with equivalent payload at any given point.
Adding in more elevators decreases this benefit somewhat (although still keeps minimal strain on the critical bottom part of the tether at any given time - it's easier to reinforce the further up you get, because reinforcements have to be supported all the way back to GEO), but allows for power transfer. With just two elevators at a time, power transfer isn't realistic (unless the tether superconducts or you can afford the mass of thousands-of-miles-long superconductor, the resistance is too great for long distance transmission; furthermore, the battery mass to store energy for several days of power accumulation is not realistic. Storing several hours worth, however, is realistic, as is transferring that much power in a couple minutes time in a "passing zone")
Kneel Before Christ!
It sounds like to me they should use this stuff to wrap the foam insulation onto the space shuttle external tank so it won't fall off. Then they can think about using it for space elevators.