Flowing Plasma Interaction with an Electric Sail Tether Element

For many spacecraft system designers, the space environment is regarded only as a threat to their hardware’s survivability. However, for some systems, the space environment provides a means to generate power and... [ view full abstract ]

For many spacecraft system designers, the space environment is regarded only as a threat to their hardware’s survivability. However, for some systems, the space environment provides a means to generate power and propulsion.  The electric sail concept, for example, uses the solar wind to propel small spacecraft.  By deploying multiple tethers, an electric sail, or E-sail, transfers momentum from solar wind protons by deflecting them via a repelling electric field established by a positively-biased tether element.  Critical to E-sail efficiency is the establishment of a large plasma sheath around each tether.  A large sheath area translates to an increased interaction area with the solar wind, which ultimately yields a greater propulsive force.  A laboratory-scaled test has been conducted at NASA’s Marshall Space Flight Center to study the interaction of a biased tether element with a drifting plasma.  This paper will describe the plasma conditions chosen in order to allow for scaling to solar wind conditions.  Measurements of drifting ion deflection by a biased tether element will also be presented.  Finally, application of the laboratory measurements to a model development effort will be discussed.