# Chinese find material to make space elevator. How much will the cable weigh?

The article China has strongest fibre that can haul 160 elephants – and a space elevator? came out today in the SCMP, and I would like to find out how much the cable would weigh. But I'm not sure if the article contains enough information to calculate it, and so I'm hoping someone can help me figure this out.

Here's what I know. 1 cubic centimeter of the fibre can hold 800 tonnes and weighs 1.6 grams and has a strength of 80 gigapascals. I also know that a space elevator is about 36 megameter long.

Here are most of the relevant numbers from the article, but I'm not 100% sure if there's something else there that could be helpful:

But so far, the space elevator idea has remained in the realm of physical and mathematical models because there has been no material strong enough to make the super-light, ultra-strong cables needed.

Those cables would need to have tensile strength – to withstand stretching – of no less than 7 gigapascals, according to Nasa. In fact, the US space agency launched a global competition in 2005 to develop such a material, with a US\$2 million prize attached. No one claimed the prize.

Now, the Tsinghua team, led by Wei Fei, a professor with the Department of Chemical Engineering, says their latest carbon nanotube fibre has tensile strength of 80 gigapascals.

Carbon nanotubes are cylindrical molecules made up of carbon atoms that are linked in hexagonal shapes with diameters as small as 1 nanometre. They have the highest known tensile strength of any material – theoretically up to 300 gigapascals

• graphite is about 2.3 g/cm^3, single-walled nanotubes might be 1.4 if packed densely but these cables are probably not just SWCNT, so graphite might be a good starting point. With density and the 80 GPa that's probably all that's needed as far as the material is concerned. The hard part is the math for the cable thickness versus height, and there should be people here who've done that calculation before, perhaps even some existing answers to address that.
– uhoh
Oct 26 '18 at 13:32
• Assuming the cubic centimeter cited was 1cm in cross-section, that's 31,250km of self-breaking length. Elevator possible without tapering the tether, and first lead tether used to pull heavier, stronger upwards could be of order of 50 ton.
– SF.
Oct 26 '18 at 17:14
• different, but related (and currently unanswered): Has there been any independent verification of the results from this Chinese nanotube study?
– uhoh
Jul 19 '19 at 0:33
• The actual paper is on ResearchGate, in case that helps: researchgate.net/publication/…
– DJG
Jul 19 '19 at 14:45
• "Here, we demonstrate the fabrication of CNT bundles (CNTBs) that are centimetres long with tensile strength over 80 GPa using ultralong defect-free CNTs." So centimeters long is ultralong?!! Wtf. Jul 20 '19 at 21:42