Impact of solar wind fluctuations on Electric Sail mission design

摘要

The Electric Solar Wind Sail (E-sail) is a propellantless propulsion system that generates thrust by exploiting the interaction between a grid of tethers, kept at a high electric potential, and the charged particles of the solar wind. Such an advanced propulsion system allows innovative and exotic mission scenarios to be envisaged, including non-Keplerian orbits, artificial Lagrange point maintenance, and heliostationary condition attainment. In the preliminary mission analysis of an E-sail-based spacecraft, the local physical properties of the solar wind are usually specified and kept constant, while the E-sail propulsive acceleration is assumed to vary with the heliocentric distance, the sail attitude, and the grid electric voltage. However, the solar wind physical properties are known to be characterized by a marked variability, which implies a non-negligible uncertainty as to whether or not the solutions obtained with a deterministic approach are representative of the actual E-sail trajectory. The aim of this paper is to propose an effective method to evaluate the impact of solar wind variability on the E-Sail trajectory design, by considering the solar wind dynamic pressure as a random variable with a gamma distribution. In particular, the effects of plasma property fluctuations on E-sail trajectory are calculated with an uncertainty quantification procedure based on the generalized polynomial chaos method. The paper also proposes a possible control strategy that uses suitable adjustments of grid electric voltage. Numerical simulations demonstrate the importance of such a control system for missions that require a precise modulation of the propulsive acceleration magnitude. (C) 2018 Elsevier Masson SAS. All rights reserved.