Simulation study of solar wind push on a charged wire: basis of solar wind electric sail propulsion

Abstract

Abstract.One possibility for propellantless propulsion in space is to use the momentum flux of the solar wind. A way to set up a solar wind sail is to have a set of thin long wires which are kept at high positive potential by an onboard electron gun so that the wires repel and deflect incident solar wind protons. The efficiency of this so-called electric sail depends on how large force a given solar wind exerts on a wire segment and how large electron current the wire segment draws from the solar wind plasma when kept at a given potential. We use 1-D and 2-D electrostatic plasma simulations to calculate the force and present a semitheoretical formula which captures the simulation results. We find that under average solar wind conditions at 1 AU the force per unit length is (5±1)×10 −8 N/m for 15 kV potential and that the electron current is accurately given by the well-known orbital motion limited (OML) theory cylindrical Langmuir probe formula. Although the force may appear small, an analysis shows that because of the very low weight of a thin wire per unit length, quite high final speeds (over 50 km/s) could be achieved by an electric sailing spacecraft using today's flight-proved components. It is possible that artificial electron heating of the plasma in the interaction region could increase the propulsive effect even further.Keywords. General or miscellaneous (Instruments useful in three or more fields; New fields (not classifiable under other headings); Techniques applicable in three or more fields)

Solar Wind Sails

“…The plasma magnet is already accessed by laboratory experiment (Slough, 2007). In 2004, Janhunen proposed a completely new idea using the solar wind, which has a set of thin long wires being kept at a high positive potential so that the wires repel and deflect incident solar wind protons and it is called as electrostatic sail (Janhunen, 2004;Janhunen & Sandroos, 2007). These ideas are not so matured to proceed to a flight demonstration in space, but attractive solar wind sails that are competitive against the existing thruster technology is emerging.…”

Boltzmann electron PIC simulation of the E-sail effect

“…The code that we use in this paper is a descendant of a PIC code that we used earlier (Janhunen and Sandroos, 2007;Janhunen, 2012Janhunen, , 2014a. It is an electrostatic code with linear particle weighting and additional grid-level smoothing which is implemented in the Fourier domain.…”

“…In order to engineer E-sail devices in detail, one should predict the magnitude of the Coulomb drag that the flowing solar wind exerts on the charged tether. Thus far this problem has been studied using particle-in-cell (PIC) simulations (Janhunen and Sandroos, 2007;Janhunen, 2009aJanhunen, , 2012, Vlasov simulations (Sánchez-Arriaga and Pastor-Moreno, 2014) and other methods (Sanmartín et al, 2008;Sanchez-Torres, 2014). However, a fully satisfactory way of estimating E-sail thrust has not yet emerged, except for negative polarity tethers (Janhunen, 2014a), which are however more suitable to use in low Earth orbit (LEO) as a deorbiting plasma brake device (Janhunen, 2010) than in the solar wind (Janhunen, 2009b).…”

“…The issue of trapped electrons was identified by Janhunen and Sandroos (2007) and simulations were later made where chaotisation of trapped electron orbits when scattering at the end of the tether and at the spacecraft was explicitly included in the PIC code, as well as occasional removal of trapped electrons due to collisions with the tether (Janhunen, 2012). However, in that calculation the timescale where trapped electrons were removed was made much faster than in reality, in order to complete the simulation run in a reasonable time.…”

Artificial equilibrium points for a generalized sail in the circular restricted three-body problem

“…This is possible by simply specializing the value of η. For example η = 2 describes the thrust provided by a solar sail (McInnes, 1999b) or a magnetic sail (Zubrin and Andrew, 1991), while η ∈ [1, 7/6] corresponds to an electric sail model (Janhunen and Sandroos, 2007;Mengali et al, 2008;Janhunen, 2010). Finally η = 0 represents a constant propulsive acceleration, or a thrust that is independent of the distance from the massive attractor.…”