The Speculist

The article says they've grown carbon nanotubes 4 centimeters long, not 4 millimeters. However, the previous record was somewhere in the same neighborhood, 1 centimeter, perhaps. So we've certainly made some progress, but not nearly by a factor of 10,000.

But, you don't actually need the individual nanotubes to stretch from top to bottom. Most of the designs I've seen call for a composite material that uses 'reasonably' sized nanotubes held together with some epoxy type glue. There are some benefits to doing it that way in terms of redundancy, but also some drawbacks in terms of lower strength to weight ratio.

Centimeters, millimeters, what's the difference? :-)

I guess I didn't realize they were already achieving visible, macro-scale lengths. Thanks for setting me straight, Andrew.

Actually we're already there. The nanotubes don't have to be that long. They actually only need to be about 1 cm and bonded with a resin epoxy. 4 cms is way beyond the required length to provide the strength neccesary for the composite nanotube/epoxy resin fiber. The only problem now, and this is a real showstopper, is how do you make the nanotubes cheap enough. Now we need to start paying way more attention to the cost of nanotube production and less attention to the length.

american is right here. Sure 40,000 km long 400 nm wide fibres would be awesome, but we don't see that. We do need unusually long fibres due to the slipperiness of the carbon nanotubes. 4 cm is really good. If they can produce them in bulk and relatively cheap, then some sort of space tether should be feasible. At least, this makes a skyhook possible and maybe the full space elevator thing possible.

One thing that is odd here is the relative lack of discussion on orbital tethers that would shift things from a lower orbit to a higher one. Kevlar or Spectra can be used now to make a viable system. I guess these aren't sexy because they can be done now with current materials and because they don't solve the Earth to orbit problem.