Stochastic Analysis of Survivability of Triple Net Tether

Abstract

A calculation method to estimate the survivability of a net-like tether system is explained in this paper. An electrodynamic tether is a candidate device to decelerate orbital debris without propellant. The major problem with using a tether in space is its vulnerability against collisions by space debris. Some conceptual designs are proposed to enhance the survivability of tether, such as tape tether, multiline tether, or net-type tether. Authors formulated the survivability of multi-segmented double-line tether in the preceding study. In this study, the calculation method is extended to treat a net-type triple tether which has been developed for the EDT by JAXA. The procedure of the calculation is as follows. First, fatality rates of each element in nettype tether are calculated by integrating differential flux multiplied by cross-sectional area, then survivabilities of each tether element are obtained as a function of time. Next, considering the topology of the net, probabilities along possible severing paths are summed up, and the survivability of the whole tether is obtained. At last, a simplified method with desirable precision and faster computation time is introduced. The numerical example shows that the net tether has much higher survivability than the double tether.