At The Oklahoman, Jim Stafford tells his readers about the Space Elevator.

Further thoughts from Dr. Edwards (again via Andy Price) on the Pugno study:  

“The supportive interaction between the CNTs already exists in several forms:
1) van de Walls forces
2) physical “knotting” or twisting like cotton or any other fiber and
3) functionalized nanotubes

Any one of these could be used to cross link CNTs and effectively transfer loads and greatly reduce the overall strength reduction of any weak CNT.  There are a couple other options as well, but these have been shown to work.  By not including this in a discussion of a macroscopic material, Pugno is insuring that the material will fall apart.  Compare a raw mat of cotton to a spun cotton thread – the performance is a little different.  I can assure everyone that raw cotton fibers are not perfect throughout their length (much less so than quality CNTs) but strong threads can still be made from them.”

Forwarded from Andy Price, and with the kind permission of Dr. Edwards, following are his initial thoughts on the Pugno study;

“The paper by Pugno has been beaten around a bit.  I just read the paper, very interesting.  Let me run through a few thoughts on it.

I start off worrying when someone creates his own theory and simulation to model everything from nanoscale to megascale (nanotubes to Earth) especially when there are plenty of molecular models out there.  But having said that, let me assume his simulation is perfect for a nanotube.  He appears to have scripted the paper to claim the cable will break (he repeats this claim at least four times throughout the paper often with the note that it is his opinion) – a second worry when an author appears to be trying to prove a conclusion.  Here are a few notes I made on his discussion:
– references and then ignores coatings to eliminate atomic oxygen erosion.
– states radiation damage will cause defects but doesn’t discuss the amount.  Damage seen in experiments is minimal for carbon fibers in the radiation fields around Earth.
– I may be wrong but it appeared to me that Pugno was using a macroscopic model to represent a damaged nanotube as a solid tube with a physical hole in it.  He certainly discusses this and then discusses missing bonds so I would be curious to know which one he went with.  I will need to look at this again.
– uses an erroneous theoretical maximum of 100GPa for the tensile strength of CNTs.  CNTs have been measured at strengths from 150GPa to 200 GPa and he references one that is at 109GPa.  His final 30GPa is directly related to this.
– uses the strength of long CNT bundles to prove his arguments.  CNT bundles are not a valid comparison because they can have very short CNTs and limited interaction.
– assumes that all CNTs will be damaged (it appears to be on a 100 nm length) and that none of them interact with each other in a supportive manner.
This is from a quick read of the paper but essentially as far as I understand, Pugno makes some poor assumptions to argue that there will be damage to all the CNTs in a ribbon, calculates that each CNT will degrade 70% and then jumps to the conclusion that the ribbon will degrade 70%.  As far as I can tell he doesn’t look at or consider the structure of the CNT threads, the interactions of the CNTs, real defect type and frequency, techniques to reduce defects in production, the real defect production rates in space, the maximum measured CNT strengths, …  The paper didn’t strike me as very good scientific work.
Having said all of this, people will view my remarks as biased – a reasonable assumption.  I have attempted to be objective because I would like to know the answers as well.  I would like to request that others examine this material as well.
I applaud the attempt to examine the materials issue, but don’t think Pugno has provided a good analysis in this paper.”

Thank you Andy and Dr. Edwards.