December 1st, 2008
How strong does a tether really have to be in order to make a working, useful Space Elevator? This is a question that Ben Shelef, CEO of the Spaceward Foundation, has been exploring in some detail.
The answer to this question relates to how strong the climber power system is. The stronger the power system is, the weaker the tether can be (and vice-versa). There is no absolute minimum number, but there is an equation which Ben has created, The Space Elevator Feasibility Condition, which answers this question.
According to Ben’s calculations, for example, a tether which has a tensile strength of 30 GPa-cc/g would be strong enough to create a useful Space Elevator provided the Climber power system can generate at least 1.5 kWatt/kg. If the tensile strength of the tether is only 25 GPa-cc/g, the power system needs to generate at least 3.5 kWatt/kg.
How does climber power relate to tether strength? Ben documents all of this in a new paper; The Space Elevator Feasibility Condition, available (in html and pdf formats) in the Library section of the Spaceward website.
Over the next few days, I’m going to be looking at and writing about this paper in more detail.
This paper is very important for all of us in the Space Elevator community to read and understand. We need to be able to pose realistic scenarios and give justifiable answers to questions when they are presented to us. The Space Elevator Feasibility Condition will help us do that.
(Picture of spontaneous formation of Stone-Wales Defect in a nanotube under tension from the Spaceward website - click on it for a slightly larger version)