Matthew Eby
December 13, 2001
ASEN 5050-Spaceflight Dynamics
University of Colorado Boulder

Abstract

Space tethers, long deployable cord structures, have recently shown promise in a wide range of astrodynamic applications. These structures, often kilometers in length, employ either a fiber weave of Silicon Carbide, Graphite, Kevlar, or other polymer, wrapped in electrically conductive material, such as copper. When deployed from a spacecraft a tether can serve many roles, as explored by recent missions including TSS-1, SEDS-I and SEDS-II. A tether can control the center of gravity for microgravity experiments, generate power by sweeping through Earth's magnetic field, or can be used to exchange momentum between two bodies, thereby providing a basis for non-thrust orbital maneuvers. In addition to exploring these topics, this paper proposes the use of a space tether to design a scientific mission to study the response of important MEMS (Micro-Electro-Mechanical-Systems) materials to exposure to the space environment. The emergence of MEMS devices in space applications, such as accelerometers, necessitates a better understanding of the response of these materials to the space environment. Specifically, a designer needs to know the response of the strength, Young's Modulus, and coefficient of thermal expansion to long period exposure to large thermal fluctuations, atomic oxygen, and high energy and ultraviolet radiation. Research at Johns Hopkins University has successfully tested the response of polysilicon to thermal fluctuation. As an extension, this paper studies the feasibility of deploying a small satellite containing polysilicon that employs tether induced electrodynamic drag to control the orbit.

Tether Concepts