A paper analyses the potential of the electric solar wind sail for solar system space missions. Applications studied include fly-by missions to terrestrial planets (Venus, Mars and Phobos, Mercury) and asteroids, missions based on non-Keplerian orbits (orbits that can be maintained only by applying continuous propulsive force), one-way boosting to outer solar system, off-Lagrange point space weather forecasting and low-cost impactor probes for added science value to other missions. We also discuss the generic idea of data clippers (returning large volumes of high resolution scientific data from distant targets packed in memory chips) and possible exploitation of asteroid resources. Possible orbits were estimated by orbit calculations assuming circular and coplanar orbits for planets. Some particular challenge areas requiring further research work and related to some more ambitious mission scenarios are also identified and discussed.
The electric solar wind sail (E-sail) is an advanced concept for spacecraft propulsion, based on momentum transfer from the solar wind plasma stream, intercepted by long and charged tethers. The electrostatic field created by the tethers deflects trajectories of solar wind protons so that their flow-aligned momentum component decreases. The flow-aligned momentum lost by the protons is transferred to the charged tether by a Coulomb force (the charged tether is pulled by the plasma charge separation electric field) and then transmitted to the spacecraft as thrust. The concept is attractive for applications because no propellant is needed for traveling over long distances. The E-sail’s operating principle is different from other propellantless propulsion technologies such as the solar photon sail and the solar wind magnetic sail. The former is based on momentum transfer from sunlight (solar photons), while the latter is based on a large loop-shaped superconductive wire whose magnetic field deflects solar wind protons from their originally straight trajectories.
The main purpose of this article is to analyze the potential of E-sail technology in some of the envisaged possible applications for solar system space activities. To a limited extent we also adopt a comparative approach,estimating the added value and other advantages stemming from E-sail technology in comparison with present chemical and electric propulsion systems and(in some cases) with other propellantless propulsion concepts. When making such comparisons a key quantity that we use for representing the mission cost is the total required velocity change, Av, also called delta-v.The Sail Propulsion Working Group, a joint working group between the Navigation Guidance and Control Section and the Electric Propulsion Section of the European Space Agency, has envisaged the study of three reference missions which could be successfully carried out using propellantless propulsion concepts.