exploits


Middle of May, we talked you about this amazing challenge: the space elevator, a cable in nanotubes between the Earth and a geostationnary satellite. A reminder here.

Nicola Pugno, a polytechnician of Turin, made his calculations: that won't work. According to him, the defects existing at atomic scale would reduce the solidity of this kind of cable of (at least) 70%.




For this application, the cable in nanotubes should resist a tension of 62 billion Pascals (62 GPa). Like if, in a rope game, 100.000 people drew on each side!
And the tests in laboratory showed that nanotubes can resist approximately 100 GPa. But if just 1 carbon atom is missing in the crystalline construction, its solidity is reduced approximately 30%.

And recent measurements on high-quality nanotubes showed that it missed 1 atom every 4 micrometers! Defects with 2 missing atoms are much more rare but Pugno points out that the cable measures 100.000 km, which increases the probabilities considerably.
Its calculations will be published in July and they show that large defects can reduce the solidity of the cable to less than 30 GPa. Ouch.
Not mentioning the micro-meteorites and the erosion due to oxygen.

On another hand, there is Bradley Edwards, who carried out the study of feasibility for NASA and who even wrote a book on the subject. He is also the president and the founder of the company Carbon Designs. Just for this, we know he's a smart guy.
Bradley says he will be able to manufacture cables resisting the threshold of 62 GPa, during the next 3 years. I skip his technical arguments.

Anyway, the discussions are running but the date of 2010 seems not realistic at all anymore.

for those who do not know : the pressure is the force per unit area applied on a surface in a direction perpendicular to that surface. Mathematically:

p = F/A

where:

p is the pressure
F is the normal force
A is the area.