Value chain · CLM-1370
In plain terms
The cable needs a material about 30 times stronger than steel. In 2003 only carbon nanotubes looked able to get there, and real fibres were nowhere near yet.
The claim as recorded
The 2003 space-elevator study states that the ribbon needs material of about 100 GPa tensile strength, about 30 times steel, and that only carbon nanotube composites could reach it: "steel is not strong enough", nor are Kevlar, carbon fibre or spider silk. It gives steel as 3 GPa and Kevlar as 3.7 GPa. Composite fibres of the time had reached about 5 GPa.
Evidence behind this: T3, a final report to the NASA Institute for Advanced Concepts; it permits "the study states Y".
Scope and limits
The source states strength, not strength-to-weight; FB-18's label speaks of strength-to-weight. No ribbon density is given on the pages read, so a specific-strength figure cannot be derived from them. 100 / 3 = 33 times steel (my arithmetic), consistent with the "30 times" on PDF p.20. The 2003 forecast that full-strength material would arrive within about two years (PDF p.2, p.10) is a projection, not a result.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.7: ultra-high-strength material (100 GPa) is critical (paraphrase); "steel is not strong enough", neither is Kevlar, carbon fibre, spider silk or any material other than carbon nanotubes (paraphrase after the quotation). PDF p.9: "Steel has a strength of 3 GPa" and Kevlar 3.7 GPa (paraphrase); fibres of 5 GPa at about 5% nanotube loading (paraphrase). PDF p.20: "To build the elevator we will need strengths of 30 times steel."
Basis: tensile strength (GPa)
Cite this
energyaperture.com/c/clm-1370
CLM-1370, Energy Aperture, as of 2003-03.
Connected records
Other published records linked to this one. A list, not a judgement.