Exponential Tethers, a Detailed Evaluation
- Paper number
IAC-05-D4.3.08
- Author
Mr. Blaise Gassend, Massachussets Institute of Technology (MIT), United States
- Year
2005
- Abstract
Since Dr Edwards' NIAC proposal, the concept of a space elevators has been revolutionized by the idea of deploying a low capacity elevator, and then exponentially building it up with materials lifted from the Earth on the elevator itself. During this build up phase, the elevator's slenderness makes it vulnerable to space debris. Moreover, most of the capital expenses have been incurred, but revenue will not start coming in until the full elevator has been built. To reduce the build up time, I proposed (Gassend 2004) the idea of using tethers with an exponential taper to speed up the build up phase. Exponential tether methods were compared with Dr Edwards' scheme, mainly on the basis of elevator growth rate. Other build up concepts have also been proposed (Shelef 2004) and evaluated. Unfortunately, lack of a common evaluation methodology makes it impossible to properly compare these different proposals. In this paper, I present a set of guidelines for how to evaluate a space elevator concept. Quantitative metrics will provide a precise evaluation of deployment time, deployment cost, deployment risk and lift rate. Qualitative criteria will take into account power supply convenience, damage repair, etc. The exponential tether concept will be revisited using the proposed evaluation methodology, and it will be compared with other existing space elevator deployment schemes. As expected, the best scheme depends strongly on the strength to mass ratio of the tether material. It is hoped that future authors will conform to this standard evaluation methodology, easing comparison between space elevator schemes.
- Abstract document