According to Janhunen et. al. (2015), the Electric Solar Wind Sail (or E-sail) – a novel propellantless technology capable of “riding” the solar winds – could reduce the cost of navigating the Solar System outside our planet’s magnetosphere to virtually zero.
The “sail” is actually an electric field created between charged tethers, arranged centrifugally around the host ship and kept in a high positive potential by an onboard electron gun, that deflect solar wind protons and extract momentum from them. It was invented in 2006 by Pekka Janhunen at the Finnish Meteorological Institute (FMI) in Helsinki, Finland.
This new technology could help turn the idea of asteroid mining into reality – after a suitable water-bearing asteroid is detected, a mining unit could be sent to extract its water by heating it up and collecting the resulting vapour into a cool container. Once the container is full, it would be separated from the “sail” and sent to the orbit of Earth of Mars, where it would be split into hydrogen and oxygen, and turned into a liquid (LH2/LOX). This fuel could then be used to fill the tanks of manned vehicles travelling between the two planets.
Due to the exponential nature of the rocket equation, intermediate tankings reduce the launch mass dramatically. The asteroid-mined water could also be used as radiation shielding of the manned compartment, thereby reducing the launch mass even further.
In addition, with cheap propellant fuel available in Mars orbit, the onboard crew would have the option of an all-propulsive landing, which might potentially eliminate the issues related to the massive and extremely expensive heat shields, and allow for a more precise determination of landing area.
Researchers at the FMI, who were behind the study, think this arrangement – called the Electric Solar Wind Sail Facilitated Manned Mars Initiative (EMMI) – could enable a fundamentally new and economically sustainable approach to manned Mars flights. According to the authors, the “recurrent cost of continuous bi-directional traffic between Earth and Mars might ultimately approach the recurrent cost of running the International Space Station”.
The paper was accepted for publication on March 27 and published on April 3 in the scientific journal Acta Astronautica.