Editing Space elevator (section)

===Cable materials===
Using the above formula, the ratio between the cross-section at geostationary orbit and the cross-section at Earth's surface, known as taper ratio, can be calculated:<ref group="note">Specific substitutions used to produce the factor {{val|4.85|e=7}}:{{block indent|<math>A(R_g)/A_s = \exp \left[ \frac{\rho \times 9.81 \times (6.378\times 10^6)^2 } {T} \left( \frac{1}{6.378\times 10^6} + \frac{(6.378\times 10^6)^2}{2 (4.2164\times 10^7)^3} - \frac{1}{4.2164\times 10^7} - \frac{(4.2164\times 10^7)^2}{2 (4.2164\times 10^7)^3}\right)\right]</math>}}</ref>{{block indent|<math>A(R_g)/A_s = \exp \left[\frac{\rho}{T}\times 4.85\times 10^7\right]</math> }}
[[File:Space Elevator Taper Ratio.svg|thumb|upright=1.2|Taper ratio as a function of specific strength]]
{| class="wikitable" style="text-align:left"
|+Taper ratio for some materials<ref name="aravind" />
|-
!Material!!Tensile strength<br />(MPa)!!Density<br />(kg/m<sup>3</sup>)!![[Specific strength]]<br />(MPa)/(kg/m<sup>3</sup>)!!Taper ratio
|-
|[[Steel]] || 5,000 || 7,900 || 0.63 ||{{val|1.6|e=33}}
|-
|[[Kevlar]] || 3,600 || 1,440 || 2.5 ||{{val|2.5|e=8}}
|-
|[[UHMWPE]] @23°C || 3,600 || 0,980 || 3.7 ||{{val|5.4|e=6}}
|-
|Single wall [[carbon nanotube]] || 130,000 || 1,300 || 100 || 1.6
|}
The taper ratio becomes very large unless the specific strength of the material used approaches 48 (MPa)/(kg/m<sup>3</sup>). Low specific strength materials require very large taper ratios which equates to large (or astronomical) total mass of the cable with associated large or impossible costs.