Stepping Closer To The Space Elevator

multicsfan writes "This article at Space Daily indicates that one of the major stumbling blocks against the space elevator has a potential solution. What do you make the elevator from? What's strong enough? It appears that carbon nanotubes may meet that requirement with a strength twice the minimum estimated." Now the problem is just getting a process that can get us from growing 4 mm in length to 47,000 km - I've got Wallace (and Gromit) working on it now.

Comments

Some issues of a rather more practical nature

[maggard]

First of all the esteemed Kim Stanley Robinson is only the latest in a long series of authors to discuss Space Elevators, indeed their pedigree goes back to the 1940's. Arthur C. Clarke was the first to bring them to wide attention in his novel "The Fountains of Paradise".

Space Elevators work by orbiting synchronously with the Earth. Indeed due to their stationary nature they're often referred to as "beanstalks" (Jack and the...) There are other designs where they instead act as a giant rotating spar slicing down through the atmosphere and back up again but the most popular is where they're tethered (anchored is probably too strong a word) somewhere on or near the Earth's equator.

Many designs truncate the outer-end of the cable, instead substituting some sort of counterweight such a captured asteroid. For vertical transport sealed cabins would be used for passengers, unsealed would do for hardy cargo. The technologies wouldn't be very exotic, indeed they could be built today by anyway halfway competent Jr. Technical School.

Most designs have the cabins ascend & descend using electric motors (none using winches & cables found in the more traditionial elevators.) The motors themselves needn't be anything special, anything that can lift the cabin in 1G would do fine. Another alternative would be some sort of magnetic drive, Lawrence Livermore's Inductrak being one good candidate.

Power requirements would be fairly modest & using the electric motors as electrical generators on the down trip could recover much of the power used. A single large power station would be enough with today's technologies, or possibly several solar satellites using future technology.

However there are a couple of fundamental problems that are evident even from this far away.

• Carbon nanotubes have thus far only been created in very short lengths. Scaling them up hasn't been achieved yet.
• There isn't a good mechanism for bonding, braiding, or otherwise welding together the nanotubes.
• The mechanical, electrical & chemical properties of the tubes are still being studied. They may prove to be unsuitable for this application.
• Carbon is flammable, be it as lumps of coal or as diamonds or as nanotubes.
• However recently other materials then carbon have been formed into nanotubes so it may not be the only choice.
• We don't have a way to get the construction materials into orbit from where to begin building. An expansion of space shipping by several orders of magnitude for an extended period of time would be required to ferry up an elevator's components from the planetary surface.
• As others have pointed out the dangers of a disrupted elevator would be significant, indeed catastrophic.
• The financial investment in such a project would dwarf all other civil engineering to date. While the payoffs could well be incredible the risk would be great & the markets unproven.

Space Elevators may well indeed prove in the long term the best way to get between orbit & a planetary surface. However they're a way off in terms of materials alone not to mention finances & other practicalities. Even if we were to develop a magic fiber tomorrow with all of the necessary properties it would be several decades before we'd be in a position to use it. That said it's never too soon to start laying the groundwork.

I purposely didn't look up & embed URLs into this: Clearly you're already online if you're reading this so paste the interesting bits into your favorite search engine and look up the nouns yourself.

J. Storrs-Hall's space dock

[WillWare]

A few years back, John Storrs-Hall (for many years the moderator of sci.nanotech) was talking about an interesting idea that, like the space elevator, is not very far beyond existing material science. It is also probably more economical. The gist is an airport runway, 300 km long and at an altitude of 100 km, with a built-in linear motor that can accelerate a spacecraft. Over 80 seconds at 10 G, the craft accelerates to 8 km/sec, necessary to maintain a circular orbit. Humans (at least young healthy ones) can survive this acceleration. Current approaches to space launch cost around $10,000 per kilogram. The space dock could allow launches for 91 cents per kilogram, dropping to 42 cents per kilogram as the construction was amortized over the first few decades of use.

3001 already explained this very thing - in 1997

[macpeep]

Arthur C Clarke's Space Odyssey 3001 - printed in 1997 - have space elevators and in the end of the book he explains that they could very well be possible to manufacture using tubular buckminsterfullerene. In the back of the book he says:

"Meanwhile, the discovery of the third form of carbon, buckminsterfullerene (C60) has made the concept of the Space Elevator much more plausible. In 1990 a group of chemists at Rice University, Houston, produced a tubular form of C60 - which has far greater tensile strength than diamond. The group's leader, Dr. Smalley, even went so far as to claim it was the strongest material that could ever exist - and added that it would make possible the construction of the Space Elevator."

Growing from 4mm in length to 47,000 km

[GeekLife.com]

I think I got a spam the other day advertising just that.
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