The E-sail is a novel propellantless technology that was invented in Finland in 2006. The E-sail utilises long, charged tethers to convert natural solar wind momentum flux into spacecraft thrust.
According to Janhunen et al. (2015) the E-sail could make asteroid mining feasible by providing essentially free logistics in the solar system outside of Earth's magnetosphere. After finding a suitable water bearing asteroid, a mining unit is could be sent by the E-sail to extract the water from asteroid soil.
This can be done by heating the material and letting the evolving water vapour condense in a cool container. When the container is full, it is separated from the mining unit and transported with an E-sail in to the orbit of Mars or Earth, where it is split into hydrogen and oxygen and liquefied. The liquid hydrogen/oxygen (LH2/LOX) fuel can be used to fill the tanks of manned vehicles travelling between Earth and Mars.
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